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Sample records for electrochemical sample matrix

  1. Sunlight assisted synthesis of silver nanoparticles in zeolite matrix and study of its application on electrochemical detection of dopamine and uric acid in urine samples

    International Nuclear Information System (INIS)

    Meenakshi, S.; Devi, S.; Pandian, K.; Devendiran, R.; Selvaraj, M.

    2016-01-01

    Sunlight assisted reduction of silver ions were accomplished for the synthesis of silver nanoparticles incorporated within the mesoporous silicate framework of zeolite Y. The zeolite-Y and AgNP/Zeo-Y were characterized by field emission scanning electron microscopy, transmission electron microscopy, N 2 adsorption-desorption BET isotherm and X–ray diffraction techniques. The incorporation of silver nanoparticles within the porous framework was further confirmed by cyclic voltammetry and electrochemical impedance spectroscopy. An enhanced electrocatalytic oxidation of biologically important molecules like dopamine and uric acid using AgNP/Zeo-Y modified glassy carbon electrode has been developed. A simultaneous oxidation of DA and UA peaks were obtained at + 0.31 V and + 0.43 V (vs. Ag/AgCl) using AgNP/Zeo-Y/GCE under the optimum experimental condition. A well-resolved peak potential window (~ 120 mV) for the oxidation of both DA and UA were observed at AgNP/Zeo-Y/GCE system. The calibration curves for DA and UA were obtained within the dynamic linear range of 0.02 × 10 −6 to 0.18 × 10 −6 M (R 2 = 0.9899) and 0.05 × 10 −6 to 0.7 × 10 −6 M (R 2 = 0.9996) and the detection limits were found to be 1.6 × 10 −8 M and 2.51 × 10 −8 M by using differential pulse voltammetry (DPV) method. The proposed method was successfully applied for the determination of both DA and UA in human urine samples with a related standard deviation was < 3%, and n = 5 using the standard addition method. - Highlights: • Sunlight assisted synthesis of AgNP/Zeo-Y via ion exchange method. • Enhanced electrocatalytic peak current values for DA and UA with a well separated peak to peak position. • AgNP/Zeo-Y/GCE for the simultaneous detection of DA and UA by CV and DPV methods. • Detection limit was found to be 1.60 × 10 -8 M and 2.51 × 10 −8 M for DA and UA respectively. • DPV technique was effectively realistic to detect DA and UA in urine samples.

  2. Electrochemical process for the manufacturing of titanium alloy matrix composites

    Directory of Open Access Journals (Sweden)

    V. Soare

    2009-07-01

    Full Text Available The paper presents a new method for precursors’ synthesis of titanium alloys matrix composites through an electrochemical process in molten calcium chloride. The cathode of the cell was made from metallic oxides powders and reinforcement ceramic particles, which were pressed and sintered into disk form and the anode from graphite. The process occurred at 850 °C, in two stages, at 2,7 / 3,2 V: the ionization of the oxygen in oxides and the reduction with calcium formed by electrolysis of calcium oxide fed in the electrolyte. The obtained composite precursors, in a form of metallic sponge, were consolidated by pressing and sintering. Chemical and structural analyses on composites samples were performed.

  3. Comparison of transition-matrix sampling procedures

    DEFF Research Database (Denmark)

    Yevick, D.; Reimer, M.; Tromborg, Bjarne

    2009-01-01

    We compare the accuracy of the multicanonical procedure with that of transition-matrix models of static and dynamic communication system properties incorporating different acceptance rules. We find that for appropriate ranges of the underlying numerical parameters, algorithmically simple yet high...... accurate procedures can be employed in place of the standard multicanonical sampling algorithm....

  4. Analysis of electrochemical disintegration process of graphite matrix

    International Nuclear Information System (INIS)

    Tian Lifang; Wen Mingfen; Chen Jing

    2010-01-01

    The electrochemical method with ammonium nitrate as electrolyte was studied to disintegrate the graphite matrix from the simulative fuel elements for high temperature gas-cooled reactor. The influences of process parameters, including salt concentration, system temperature and current density, on the disintegration rate of graphite fragments were investigated in the present work. The experimental results showed that the disintegration rate depended slightly on the temperature and salt concentration. The current density strongly affected the disintegration rate of graphite fragments. Furthermore, the content of introduced oxygen in final graphite fragments was independent of the current density and the concentration of electrolyte. Moreover, the structural evolution of graphite was analyzed based on the microstructural parameters determined by X-ray diffraction profile fitting analysis using MAUD (material analysis using diffraction) before and after the disintegration process. It may safely be concluded that the graphite disintegration can be ascribed to the influences of the intercalation of foreign molecules in between crystal planes and the partial oxidation involved. The disintegration process was described deeply composed of intercalate part and further oxidation part of carbon which effected together to lead to the collapse of graphite crystals.

  5. Electrochemical behavior of anodized AA6063-T6 alloys affected by matrix structures

    International Nuclear Information System (INIS)

    Huang, Yung-Sen; Shih, Teng-Shih; Wu, Chen-En

    2013-01-01

    Highlights: ► Deformation after solution treatment introduced Al matrix to have deformation bands and few Si particles. ► Dislocations remained in the matrix lift up field potential and produce AlOOH oxide in the AAO film. ► The silicon-containing particles were found to trap in the AAO film. ► The silicon particles and the Al(OOH) oxide is significantly to influence the electrochemical behavior of AAO films. - Abstract: AA 6063 alloys were cold-rolled (CR) either before or after solution treatment (S) and then different samples were artificially aged (T6) to obtain different samples (CRST6 and SCRT6). The highest dislocation density was observed in the SCRT6 sample which also showed the lowest particle count among the three samples; ST6, CRST6 and SCRT6. Subsequently, all samples were anodized in a 15 wt% sulfuric acid solution for different time spans to obtain anodic aluminum oxide (AAO) films. The anodized samples were further analyzed with X-ray Photoelectron Spectroscopy (XPS) analysis. We determined that the constituent phases in the AAO film were composed of hydrated amorphous alumina, hydrated oxide (Al(OH) 3 ) and oxyhydroxide (AlOOH) phases together with some silicon-containing particles trapped in the films on all samples. In the electrochemical test, the silicon-containing particles and hydrated Al(OH) 3 oxide that existed at the electrolyte/film (e/f) interface were found to inversely influence the corrosion resistance of the anodized samples.

  6. Evaluation of the Technical-Economic Potential of Particle- Reinforced Aluminum Matrix Composites and Electrochemical Machining

    International Nuclear Information System (INIS)

    Schubert, A; Hackert-Oschätzchen, M; Lehnert, N; Götze, U; Herold, F; Schmidt, A; Meichsner, G

    2016-01-01

    Compared to conventional cutting, the processing of materials by electrochemical machining offers some technical advantages like high surface quality, no thermal or mechanical impact on the work piece and preservation of the microstructure of the work piece material. From the economic point of view, the possibility of process parallelization and the absence of any process-related tool wear are mentionable advantages of electrochemical machining. In this study, based on experimental results, it will be evaluated to what extent the electrochemical machining is technically and economically suitable for the finish-machining of particle- reinforced aluminum matrix composites (AMCs). Initial studies showed that electrochemical machining - in contrast to other machining processes - has the potential to fulfil demanding requirements regarding precision and surface quality of products or components especially when applied to AMCs. In addition, the investigations show that processing of AMCs by electrochemical machining requires less energy than the electrochemical machining of stainless steel. Therefore, an evaluation of electrochemically machined AMCs - compared to stainless steel - from a technical and an economic perspective will be presented in this paper. The results show the potential of electro-chemically machined AMCs and contribute to the enhancement of instruments for technical-economic evaluations as well as a comprehensive innovation control. (paper)

  7. Electrochemical dehalogenisation of chlorinated aromatics - from model substances to practice-relevant ''real life'' samples

    International Nuclear Information System (INIS)

    Voss, I.; Altrogge, M.; Francke, W.

    1993-01-01

    Building on methods for the dehalogenisation of chlorinated benzoles known from the literature, an investigation was carried out whether polychlorinated biphenyls, dibenzo furane and dibenzo-p-dioxin can be dehalogenated electrochemically. The experiments were carried out with pure substances and transferred to mixed substances (real life samples). The investigations showed that both pure substances and complex mixtures can be dehalogenated without problems. Even in the presence of a clear oil matrix (e.g.: Oil trickled through a deposit), dehalogenisation of the xenobiotica present is possible. First attempts at 'scaling up' show that the method is also suitable in principle, for the disposal of large quantities of contaminated liquids. (BBR) [de

  8. Analysis of Off Gas From Disintegration Process of Graphite Matrix by Electrochemical Method

    International Nuclear Information System (INIS)

    Tian Lifang; Wen Mingfen; Chen Jing

    2010-01-01

    Using electrochemical method with salt solutions as electrolyte, some gaseous substances (off gas) would be generated during the disintegration of graphite from high-temperature gas-cooled reactor fuel elements. The off gas is determined to be composed of H 2 , O 2 , N 2 , CO 2 and NO x by gas chromatography. Only about 1.5% graphite matrix is oxidized to CO 2 . Compared to the direct burning-graphite method, less off gas,especially CO 2 , is generated in the disintegration process of graphite by electrochemical method and the treatment of off gas becomes much easier. (authors)

  9. Combining Electrochemical Sensors with Miniaturized Sample Preparation for Rapid Detection in Clinical Samples

    Science.gov (United States)

    Bunyakul, Natinan; Baeumner, Antje J.

    2015-01-01

    Clinical analyses benefit world-wide from rapid and reliable diagnostics tests. New tests are sought with greatest demand not only for new analytes, but also to reduce costs, complexity and lengthy analysis times of current techniques. Among the myriad of possibilities available today to develop new test systems, amperometric biosensors are prominent players—best represented by the ubiquitous amperometric-based glucose sensors. Electrochemical approaches in general require little and often enough only simple hardware components, are rugged and yet provide low limits of detection. They thus offer many of the desirable attributes for point-of-care/point-of-need tests. This review focuses on investigating the important integration of sample preparation with (primarily electrochemical) biosensors. Sample clean up requirements, miniaturized sample preparation strategies, and their potential integration with sensors will be discussed, focusing on clinical sample analyses. PMID:25558994

  10. The Performance Analysis Based on SAR Sample Covariance Matrix

    Directory of Open Access Journals (Sweden)

    Esra Erten

    2012-03-01

    Full Text Available Multi-channel systems appear in several fields of application in science. In the Synthetic Aperture Radar (SAR context, multi-channel systems may refer to different domains, as multi-polarization, multi-interferometric or multi-temporal data, or even a combination of them. Due to the inherent speckle phenomenon present in SAR images, the statistical description of the data is almost mandatory for its utilization. The complex images acquired over natural media present in general zero-mean circular Gaussian characteristics. In this case, second order statistics as the multi-channel covariance matrix fully describe the data. For practical situations however, the covariance matrix has to be estimated using a limited number of samples, and this sample covariance matrix follow the complex Wishart distribution. In this context, the eigendecomposition of the multi-channel covariance matrix has been shown in different areas of high relevance regarding the physical properties of the imaged scene. Specifically, the maximum eigenvalue of the covariance matrix has been frequently used in different applications as target or change detection, estimation of the dominant scattering mechanism in polarimetric data, moving target indication, etc. In this paper, the statistical behavior of the maximum eigenvalue derived from the eigendecomposition of the sample multi-channel covariance matrix in terms of multi-channel SAR images is simplified for SAR community. Validation is performed against simulated data and examples of estimation and detection problems using the analytical expressions are as well given.

  11. Electrochemical removal of metals from crude oil samples

    Energy Technology Data Exchange (ETDEWEB)

    Welter, K.; Salazar, E.; Balladores, Y.; Marquez, O.P.; Marquez, J.; Martinez, Y. (Laboratorio de Electroquimica, Facultad de Ciencias, Universidad de Los Andes, Merida 5101-Venezuela)

    2009-02-15

    Removal of vanadium from vanadyl (IV) meso-tetra-phenylporphyrin (VO-MTPP) and vanadyl (IV) octa-ethylporphyrin (VO-OEP) and metals removal from Ayacucho Venezuelan crude oil samples were performed using electrochemical techniques. According to cyclic voltammograms, a potential of - 2.3 V vs. Ag/AgNO{sub 3} (0.1 M), LiClO{sub 4} (0.1 M) in acetonitrile, was chosen for running electrolysis at platinum (Pt), graphite (G) and glassy carbon (GC) electrodes. Qualitative analysis was done by cyclic voltammetry (CV) and atomic absorption spectroscopy (AAS) while quantification was performed by AAS and inductively coupled plasma/atomic emission spectrometry (ICP/AES). Three stages (best results) of the study are reported: (a) when using commercial porphyrins; the best conditions for electrolysis were: tetrahydrofuran (THF)/20% methanol (MeOH)/1% perchloric acid (HClO{sub 4}) on GC, producing 84% hydro-demetalation (HDM) for VO-MTPP, and 78% HDM for VO-OEP; (b) when using extracts of crude oil; demetalation percentages, after 90 min of electrolysis, on graphite, and after 120 min of electrolysis on platinum, were 66.44% and 64.10% HDM respectively, no discrimination of metals under these conditions (c) from electrolysis in whole crude oil, quantitative analysis gave: vanadium (V) 31.2 mg/kg, iron (Fe) 65, 0 mg/kg and nickel (Ni) 6, 3 mg/kg, with charge efficiencies of V (7.5%), Fe (79.6%) and Ni (8.2%). (author)

  12. Matrix Sampling of Items in Large-Scale Assessments

    Directory of Open Access Journals (Sweden)

    Ruth A. Childs

    2003-07-01

    Full Text Available Matrix sampling of items -' that is, division of a set of items into different versions of a test form..-' is used by several large-scale testing programs. Like other test designs, matrixed designs have..both advantages and disadvantages. For example, testing time per student is less than if each..student received all the items, but the comparability of student scores may decrease. Also,..curriculum coverage is maintained, but reporting of scores becomes more complex. In this paper,..matrixed designs are compared with more traditional designs in nine categories of costs:..development costs, materials costs, administration costs, educational costs, scoring costs,..reliability costs, comparability costs, validity costs, and reporting costs. In choosing among test..designs, a testing program should examine the costs in light of its mandate(s, the content of the..tests, and the financial resources available, among other considerations.

  13. Disintegration of graphite matrix from the simulative high temperature gas-cooled reactor fuel element by electrochemical method

    International Nuclear Information System (INIS)

    Tian Lifang; Wen Mingfen; Li Linyan; Chen Jing

    2009-01-01

    Electrochemical method with salt as electrolyte has been studied to disintegrate the graphite matrix from the simulative high temperature gas-cooled reactor fuel elements. Ammonium nitrate was experimentally chosen as the appropriate electrolyte. The volume average diameter of disintegrated graphite fragments is about 100 μm and the maximal value is less than 900 μm. After disintegration, the weight of graphite is found to increase by about 20% without the release of a large amount of CO 2 probably owing to the partial oxidation to graphite in electrochemical process. The present work indicates that the improved electrochemical method has the potential to reduce the secondary nuclear waste and is a promising option to disintegrate graphite matrix from high temperature gas-cooled reactor spent fuel elements in the head-end of reprocessing.

  14. Spiked natural matrix materials as quality assessment samples

    International Nuclear Information System (INIS)

    Feiner, M.S.; Sanderson, C.G.

    1988-01-01

    The Environmental Measurements Laboratory has conducted the Quality Assessment Program since 1976 to evaluate the quality of the environmental radioactivity data, which is reported to the Department of Energy by as many as 42 commercial contractors involved in nuclear work. In this program, matrix materials of known radionuclide concentrations are distributed routinely to the contractors and the reported results are compared. The five matrices used are: soil, vegetation, animal tissue, water and filter paper. Environmental soil, vegetation and animal tissue are used, but the water and filter paper samples are prepared by spiking with known amounts of standard solutions traceable to the National Bureau of Standards. A summary of results is given to illustrate the successful operation of the program. Because of the difficulty and high cost of collecting large samples of natural matrix material and to increase the versatility of the program, an attempt was recently made to prepare the soil, vegetation and animal tissue samples with spiked solutions. A description of the preparation of these reference samples and the results of analyses are presented along with a discussion of the pitfalls and advantages of this approach. 19 refs.; 6 tabs

  15. Design compliance matrix waste sample container filling system for nested, fixed-depth sampling system

    International Nuclear Information System (INIS)

    BOGER, R.M.

    1999-01-01

    This design compliance matrix document provides specific design related functional characteristics, constraints, and requirements for the container filling system that is part of the nested, fixed-depth sampling system. This document addresses performance, external interfaces, ALARA, Authorization Basis, environmental and design code requirements for the container filling system. The container filling system will interface with the waste stream from the fluidic pumping channels of the nested, fixed-depth sampling system and will fill containers with waste that meet the Resource Conservation and Recovery Act (RCRA) criteria for waste that contains volatile and semi-volatile organic materials. The specifications for the nested, fixed-depth sampling system are described in a Level 2 Specification document (HNF-3483, Rev. 1). The basis for this design compliance matrix document is the Tank Waste Remediation System (TWRS) desk instructions for design Compliance matrix documents (PI-CP-008-00, Rev. 0)

  16. Wet-digestion of environmental sample using silver-mediated electrochemical method

    International Nuclear Information System (INIS)

    Kuwabara, Jun

    2010-01-01

    An application of silver-mediated electrochemical method to environmental samples as the effective digestion method for iodine analysis was tried. Usual digestion method for 129 I in many type of environmental sample is combustion method using quartz glass tube. Chemical yield of iodine on the combustion method reduce depending on the type of sample. The silver-mediated electrochemical method is expected to achieve very low loss of iodine. In this study, dried kombu (Laminaria) sample was tried to digest with electrochemical cell. At the case of 1g of sample, digestion was completed for about 24 hours under the electric condition of <10V and <2A. After the digestion, oxidized species of iodine was reduced to iodide by adding sodium sulfite. And then the precipitate of silver iodide was obtained. (author)

  17. Empirical method for matrix effects correction in liquid samples

    International Nuclear Information System (INIS)

    Vigoda de Leyt, Dora; Vazquez, Cristina

    1987-01-01

    A simple method for the determination of Cr, Ni and Mo in stainless steels is presented. In order to minimize the matrix effects, the conditions of liquid system to dissolve stainless steels chips has been developed. Pure element solutions were used as standards. Preparation of synthetic solutions with all the elements of steel and also mathematic corrections are avoided. It results in a simple chemical operation which simplifies the method of analysis. The variance analysis of the results obtained with steel samples show that the three elements may be determined from the comparison with the analytical curves obtained with the pure elements if the same parameters in the calibration curves are used. The accuracy and the precision were checked against other techniques using the British Chemical Standards of the Bureau of Anlysed Samples Ltd. (England). (M.E.L.) [es

  18. Extraordinary tunable dynamic range of electrochemical aptasensor for accurate detection of ochratoxin A in food samples

    Directory of Open Access Journals (Sweden)

    Lin Cheng

    2017-06-01

    Full Text Available We report the design of a sensitive, electrochemical aptasensor for detection of ochratoxin A (OTA with an extraordinary tunable dynamic sensing range. This electrochemical aptasensor is constructed based on the target induced aptamer-folding detection mechanism and the recognition between OTA and its aptamers results in the conformational change of the aptamer probe and thus signal changes for measurement. The dynamic sensing range of the electrochemical aptasensor is successfully tuned by introduction of free assistant aptamer probes in the sensing system. Our electrochemical aptasensor shows an extraordinary dynamic sensing range of 11-order magnitude of OTA concentration from 10−8 to 102 ng/g. Of great significance, the signal response in all OTA concentration ranges is at the same current scale, demonstrating that our sensing protocol in this research could be applied for accurate detections of OTA in a broad range without using any complicated treatment of signal amplification. Finally, OTA spiked red wine and maize samples in different dynamic sensing ranges are determined with the electrochemical aptasensor under optimized sensing conditions. This tuning strategy of dynamic sensing range may offer a promising platform for electrochemical aptasensor optimizations in practical applications.

  19. Indirect Electrochemical Analysis of Crocin in Phytochemical Sample

    Directory of Open Access Journals (Sweden)

    Riyaz Ahmad Dar

    2012-01-01

    Full Text Available A new electroanalytical method has been developed for the quantitative determination of crocin in a sample of stigmas of saffron (Crocus sativus L.. Crocin is polarographically inactive. However, cysteine in 0.02 M NaCl, pH=5.2±0.01 produces a well defined wave/peak with E1/2/Ep= –0.47/–0.45 V vs. Ag/AgCl. On recording polarograms of a set of solution containing a fixed concentration of cysteine and varying concentrations of crocin under aforesaid experimental conditions a gradual decrease in peak height/diffusion current and a negative shift in peak potential was observed. Thus, indicating cysteine-crocin interaction. Amperometric titration indicated crocin to cysteine ratio of 1:2. The above amperometric titration procedure has been used to determine the concentration of crocin in a sample of saffron. Crystallization process was carried out for the extraction of crocin from dried powder of saffron stigmas. The crystallized crocin was identified by UV-Visible spectrophotometry(at 255 nm and 442 nm and the quantitative analysis by the developed amperometric method. The concentration of crocin in saffron was found to be 2.13% and purity of isolated crocin 96.81%. The percent recovery varied from 98.56–100.31% and RSD (n=5 of 2.17%.The validation of the proposed procedure for the quantitative assay of crocin was examined via an evaluation of the repeatability, recovery, selectivity and relative standard deviation.

  20. Electrochemical determination of morin in Kiwi and Strawberry fruit samples using vanadium pentoxide nano-flakes.

    Science.gov (United States)

    Sasikumar, Ragu; Govindasamy, Mani; Chen, Shen-Ming; Chieh-Liu, Yu; Ranganathan, Palraj; Rwei, Syang-Peng

    2017-10-15

    Herein, we report the synthesis of Vanadium Pentoxide Nanoflakes (V 2 O 5 NF) using ionic liquid and employed the V 2 O 5 NF in electrochemical determination of Morin (MR) in fruit samples. The V 2 O 5 NF were characterized by Powder X-ray diffraction (PXRD), scanning electron microscope (SEM), energy-dispersive X-ray analyzer (EDX), differential pulse voltammetry (DPV), and cyclic voltammetry (CV). Remarkably, the as-synthesized V 2 O 5 NF exhibited excellent electrochemical behavior and electrochemical ability towards MR. The CV and DPV studies were recognized that the electrochemical performance of V 2 O 5 NF film modified glassy carbon electrode (V 2 O 5 NF/GCE) towards detection of MR is outstanding in comparison with unmodified GCE. The proposed MR sensor shows a wide linear range, high sensitivity, and low limit of detection are 0.05-10.93μm, 1.130μAμM -1 cm -2 , and 9nM respectively. The fabulous analytical parameters of the developed sensor surpassed the previously reported modified electrodes, rendering the potential application of V 2 O 5 NF in environmental, biomedical, and pharmaceutical samples. Copyright © 2017. Published by Elsevier Inc.

  1. Comparison of dechlorination rates for field DNAPL vs synthetic samples: effect of sample matrix

    Science.gov (United States)

    O'Carroll, D. M.; Sakulchaicharoen, N.; Herrera, J. E.

    2015-12-01

    Nanometals have received significant attention in recent years due to their ability to rapidly destroy numerous priority source zone contaminants in controlled laboratory studies. This has led to great optimism surrounding nanometal particle injection for insitu remediation. Reported dechlorination rates vary widely among different investigators. These differences have been ascribed to differences in the iron types (granular, micro, or nano-sized iron), matrix solution chemistry and the morphology of the nZVI surface. Among these, the effects of solution chemistry on rates of reductive dechlorination of various chlorinated compounds have been investigated in several short-term laboratory studies. Variables investigated include the effect of anions or groundwater solutes such as SO4-2, Cl-, NO3-, pH, natural organic matters (NOM), surfactant, and humic acid on dechlorination reaction of various chlorinated compounds such as TCE, carbon tetrachloride (CT), and chloroform (CF). These studies have normally centered on the assessment of nZVI reactivity toward dechlorination of an isolated individual contaminant spiked into a ground water sample under ideal conditions, with limited work conducted using real field samples. In this work, the DNAPL used for the dechlorination study was obtained from a contaminatied site. This approach was selected to adequately simulate a condition where the nZVI suspension was in direct contact with DNAPL and to isolate the dechlorination activity shown by the nZVI from the groundwater matrix effects. An ideal system "synthetic DNAPL" composed of a mixture of chlorinated compounds mimicking the composition of the actual DNAPL was also dechlorinated to evaluate the DNAPL "matrix effect" on NZVI dechlorination activity. This approach allowed us to evaluate the effect of the presence of different types of organic compounds (volatile fatty acids and humic acids) found in the actual DNAPL on nZVI dechlorination activity. This presentation will

  2. Electrochemical Analysis of Antichemotherapeutic Drug Zanosar in Pharmaceutical and Biological Samples by Differential Pulse Polarography

    OpenAIRE

    Reddy, Chennupalle Nageswara; ReddyPrasad, Puthalapattu; Sreedhar, NeelamYughandhar

    2013-01-01

    The electrochemical reduction of zanosar was investigated systematically by direct current polarography, cyclic voltammetry, and differential pulse polarography (DPP). A simple DPP technique was proposed for the direct quantitative determination of anticancer drug zanosar in pharmaceutical formulation and spiked human urine samples for the first time. The reduction potential was −0.28 V versus Ag/AgCl with a hanging mercury drop electrode in Britton-Robinson buffer as supporting electrolyte. ...

  3. Observation of a physical matrix effect during cold vapour generation measurement of mercury in emissions samples

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Richard J.C., E-mail: richard.brown@npl.co.uk; Webb, William R.; Goddard, Sharon L.

    2014-05-01

    Highlights: • A matrix effect for CV-AFS measurement of mercury in emissions samples is reported. • This results from the different efficiencies of liberation of reduced mercury. • There is a good correlation between solution density and the size of the effect. • Several methods to overcome the bias are presented and discussed. - Abstract: The observation of a physical matrix effect during the cold vapour generation–atomic fluorescence measurement of mercury in emissions samples is reported. The effect is as a result of the different efficiencies of liberation of reduced mercury from solution as the matrix of the solution under test varies. The result of this is that peak area to peak height ratios decease as matrix concentration increases, passing through a minimum, before the ratio then increases as matrix concentration further increases. In the test matrices examined – acidified potassium dichromate and sodium chloride solutions – the possible biases caused by differences between the calibration standard matrix and the test sample matrix were as large as 2.8% (relative) representing peak area to peak height ratios for calibration standards and matrix samples of 45 and 43.75, respectively. For the system considered there is a good correlation between the density of the matrix and point of optimum liberation of dissolved mercury for both matrix types. Several methods employing matrix matching and mathematical correction to overcome the bias are presented and their relative merits discussed; the most promising being the use of peak area, rather than peak height, for quantification.

  4. Electrochemically modified sulfisoxazole nanofilm on glassy carbon for determination of cadmium(II) in water samples

    International Nuclear Information System (INIS)

    Gupta, Vinod Kumar; Yola, Mehmet Lütfi; Atar, Necip; Solak, Ali Osman; Uzun, Lokman; Üstündağ, Zafer

    2013-01-01

    Highlights: • Sulfisoxazole was grafted onto glassy carbon electrode. • The electrode was characterized by spectroscopic and electrochemical methods. • It has been used for the determination of Cd(II) ions in real samples in very low concentrations. -- Abstract: Sulfisoxazole (SO) was grafted to glassy carbon electrode (GCE) via the electrochemical oxidation of SO in acetonitrile solution containing 0.1 M tetrabutylammoniumtetra-fluoroborate (TBATFB). The prepared electrode was characterized by using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), reflection–absorption infrared spectroscopy (RAIRS) and X-ray photoelectron spectroscopy (XPS). The ellipsometric thickness of SO nanofilm at the glassy carbon surface was obtained as 14.48 ± 0.11 nm. The stability of the SO modified GCE was studied. The SO modified GCE was also utilized for the determination of Cd(II) ions in water samples in the presence of Pb(II) and Fe(II) by adsorptive stripping voltammetry. The linearity range and the detection limit of Cd(II) ions were 1.0 × 10 −10 to 5.0 × 10 −8 M and 3.3 × 10 −11 M (S/N = 3), respectively

  5. Sample preparation and electrochemical data of Co3O4 working electrode for seawater splitting

    Directory of Open Access Journals (Sweden)

    Malkeshkumar Patel

    2017-10-01

    Full Text Available In this data article, we presented the electrochemical data of the working electrode made of Co3O4 semi-transparent film. Electrochemically stable, porous nature of Kirkendall-diffusion grown Co3O4 films were applied to generate hydrogen from the seawater splitting (Patel et al., 2017 [1]. The data presented in this article includes the photograph of prepared samples, polarization curves for water oxidation and Tafel plot, linear sweep voltammetry measurements under the pulsed light condition in 0.1 M Na2S2O3 electrolyte, and transient photoresponses with natural sea water. Moreover, seawater splitting using the Co3O4 working electrode is demonstrated.

  6. Distribution of the Determinant of the Sample Correlation Matrix: Monte Carlo Type One Error Rates.

    Science.gov (United States)

    Reddon, John R.; And Others

    1985-01-01

    Computer sampling from a multivariate normal spherical population was used to evaluate the type one error rates for a test of sphericity based on the distribution of the determinant of the sample correlation matrix. (Author/LMO)

  7. Automated MALDI Matrix Coating System for Multiple Tissue Samples for Imaging Mass Spectrometry

    Science.gov (United States)

    Mounfield, William P.; Garrett, Timothy J.

    2012-03-01

    Uniform matrix deposition on tissue samples for matrix-assisted laser desorption/ionization (MALDI) is key for reproducible analyte ion signals. Current methods often result in nonhomogenous matrix deposition, and take time and effort to produce acceptable ion signals. Here we describe a fully-automated method for matrix deposition using an enclosed spray chamber and spray nozzle for matrix solution delivery. A commercial air-atomizing spray nozzle was modified and combined with solenoid controlled valves and a Programmable Logic Controller (PLC) to control and deliver the matrix solution. A spray chamber was employed to contain the nozzle, sample, and atomized matrix solution stream, and to prevent any interference from outside conditions as well as allow complete control of the sample environment. A gravity cup was filled with MALDI matrix solutions, including DHB in chloroform/methanol (50:50) at concentrations up to 60 mg/mL. Various samples (including rat brain tissue sections) were prepared using two deposition methods (spray chamber, inkjet). A linear ion trap equipped with an intermediate-pressure MALDI source was used for analyses. Optical microscopic examination showed a uniform coating of matrix crystals across the sample. Overall, the mass spectral images gathered from tissues coated using the spray chamber system were of better quality and more reproducible than from tissue specimens prepared by the inkjet deposition method.

  8. Electrochemical study of oxidation process of promethazine using sensor based on carbon nanotubes paste containing immobilized DNA on inorganic matrix

    Directory of Open Access Journals (Sweden)

    João Paulo Marco

    2014-10-01

    Full Text Available In the present work the voltammetric behavior and the oxidation process of promethazine (PHZ in electrochemical sensor based on carbon nanotubes paste containing DNA immobilized on the inorganic matrix prepared by sol-gel process (SiO2/Al2O3/Nb2O5. The method of Laviron verified that the system is irreversible and high speed of electron transfer between the electrode and DNA. The study of the oxidation of PHZ and influence of pH showed slope of 0.054 V / pH (near the nernstian system: 0.0592 V / pH suggesting that it involves the transfer of two protons and two electrons.

  9. Electrochemical Corrosion Behaviour of Alumina-Al 6061 and Silicon Carbide-Al 6061 Metal-Matrix Composites

    International Nuclear Information System (INIS)

    Mohamed, K.E.; Gad, M.M.A.; El-Sayed, A.A.; Moustafa, O.H.

    2001-01-01

    The electrochemical corrosion behaviour of powder metallurgy-processed metal-matrix composites (MMCs)based on Al alloy 6061 reinforced with particulate Al 2 O 3 or Sic has been studied in chloride-containing environment. Also, the corrosion behaviour of the unrein forced Al 6061 produced by the same route investigated. Electrochemical tests were conducted on composites containing 10 and 20 vo l% of both reinforced particulates. Potentiodynamic polarization tests have been carried out in neutral as well as acidic and alkaline de-aerated 10 -3 M Na CI solution. In the neutral environment, the addition of Al 2 O 3 particulates was found to shift both the corrosion potential (E corr ) and the break down potential (E b ) slightly into the positive direction irrespective of the volume fraction added (10 and 20 vo l%). On the other hand , Sic caused a shift of E corr into the active site while the E b value was slightly ennobled. For both composites, the corrosion current values at the break down potentials were almost the same as the unrein forced alloy. In an attempt to further clarify the role of both particulate addition, cathodic polarization runs were conducted in both acidic (ph 3) and alkaline (ph 9)solutions for 20 vo l% of Al 2 O 3 and 20 vo l% Sic composite specimens. This indicated that cathodic current values for Sic composites were higher than those corresponding to the unrein forced alloy 6061, and those for the Al 2 O 3 composites were lower

  10. Matrix algebra and sampling theory : The case of the Horvitz-Thompson estimator

    NARCIS (Netherlands)

    Dol, W.; Steerneman, A.G.M.; Wansbeek, T.J.

    Matrix algebra is a tool not commonly employed in sampling theory. The intention of this paper is to help change this situation by showing, in the context of the Horvitz-Thompson (HT) estimator, the convenience of the use of a number of matrix-algebra results. Sufficient conditions for the

  11. Effect of sample matrix on the fundamental properties of the inductively coupled plasma

    International Nuclear Information System (INIS)

    Lehn, Scott A.; Warner, Kelly A.; Huang Mao; Hieftje, Gary M.

    2003-01-01

    In the inductively coupled plasma (ICP), the emission intensities of atomic and ionic spectral lines are controlled by fundamental parameters such as electron temperature, electron number density, gas-kinetic temperature, analyte atom and ion number densities, and others. Accordingly, the effect of a sample matrix on the analyte emission intensity in an ICP might be attributable to changes in these fundamental parameters caused by the matrix elements. In the present study, a plasma imaging instrument that combines Thomson scattering, Rayleigh scattering, laser-induced fluorescence and computed tomography has been employed to measure the above-mentioned parameters in the presence and absence of matrix elements. The data thus obtained were all collected on a spatially resolved basis and without the need for Abel inversion. Calcium, strontium and barium served as analytes, while lithium, copper and zinc were introduced as matrix elements. Comparing the data with and without the matrix elements allows us to determine the extent to which each fundamental parameter changes in the presence of a matrix element, and to better understand the nature of the matrix effects that occur in the ICP. As has been seen in previous studies with different matrix elements, ion emission and ion number densities follow opposite trends when matrix interferents are introduced into the plasma: ion emission is enhanced by the presence of matrix interferents while ion concentrations are lowered. These changes are consistent with a shift from collisional deactivation to radiative decay of excited-state analyte species

  12. Electrochemical Immunosensor for the Detection of Aflatoxin B1 in Palm Kernel Cake and Feed Samples

    Directory of Open Access Journals (Sweden)

    Farah Asilah Azri

    2017-11-01

    Full Text Available Palm kernel cake (PKC is the solid residue following oil extraction of palm kernels and useful to fatten animals either as a single feed with only minerals and vitamins supplementation, or mixed with other feedstuffs such as corn kernels or soy beans. The occurrence of mycotoxins (aflatoxins, ochratoxins, zearalenone, and fumonisins in feed samples affects the animal’s health and also serves as a secondary contamination to humans via consumption of eggs, milk and meats. Of these, aflatoxin B1 (AFB1 is the most toxically potent and a confirmed carcinogen to both humans and animals. Methods such as High Performance Liquid Chromatography (HPLC and Liquid Chromatography–Mass Spectrometry (LC-MS/MS are common in the determination of mycotoxins. However, these methods usually require sample pre-treatment, extensive cleanup and skilled operator. Therefore, in the present work, a rapid method of electrochemical immunosensor for the detection of AFB1 was developed based on an indirect competitive enzyme-linked immunosorbent assay (ELISA. Multi-walled carbon nanotubes (MWCNT and chitosan (CS were used as the electrode modifier for signal enhancement. N-ethyl-N′-(3-dimethylaminopropyl-carbodiimide (EDC and N-hydroxysuccinimide (NHS activated the carboxyl groups at the surface of nanocomposite for the attachment of AFB1-BSA antigen by covalent bonding. An indirect competitive reaction occurred between AFB1-BSA and free AFB1 for the binding site of a fixed amount of anti-AFB1 antibody. A catalytic signal based on horseradish peroxidase (HRP in the presence of hydrogen peroxide (H2O2 and 3,3′,5,5′-tetramethylbenzidine (TMB mediator was observed as a result of attachment of the secondary antibody to the immunoassay system. As a result, the reduction peak of TMB(Ox was measured by using differential pulse voltammetry (DPV analysis. Based on the results, the electrochemical surface area was increased from 0.396 cm2 to 1.298 cm2 due to the electrode

  13. Electrochemical Immunosensor for the Detection of Aflatoxin B₁ in Palm Kernel Cake and Feed Samples.

    Science.gov (United States)

    Azri, Farah Asilah; Selamat, Jinap; Sukor, Rashidah

    2017-11-30

    Palm kernel cake (PKC) is the solid residue following oil extraction of palm kernels and useful to fatten animals either as a single feed with only minerals and vitamins supplementation, or mixed with other feedstuffs such as corn kernels or soy beans. The occurrence of mycotoxins (aflatoxins, ochratoxins, zearalenone, and fumonisins) in feed samples affects the animal's health and also serves as a secondary contamination to humans via consumption of eggs, milk and meats. Of these, aflatoxin B₁ (AFB₁) is the most toxically potent and a confirmed carcinogen to both humans and animals. Methods such as High Performance Liquid Chromatography (HPLC) and Liquid Chromatography-Mass Spectrometry (LC-MS/MS) are common in the determination of mycotoxins. However, these methods usually require sample pre-treatment, extensive cleanup and skilled operator. Therefore, in the present work, a rapid method of electrochemical immunosensor for the detection of AFB₁ was developed based on an indirect competitive enzyme-linked immunosorbent assay (ELISA). Multi-walled carbon nanotubes (MWCNT) and chitosan (CS) were used as the electrode modifier for signal enhancement. N -ethyl- N '-(3-dimethylaminopropyl)-carbodiimide (EDC) and N -hydroxysuccinimide (NHS) activated the carboxyl groups at the surface of nanocomposite for the attachment of AFB₁-BSA antigen by covalent bonding. An indirect competitive reaction occurred between AFB₁-BSA and free AFB₁ for the binding site of a fixed amount of anti-AFB₁ antibody. A catalytic signal based on horseradish peroxidase (HRP) in the presence of hydrogen peroxide (H₂O₂) and 3,3',5,5'-tetramethylbenzidine (TMB) mediator was observed as a result of attachment of the secondary antibody to the immunoassay system. As a result, the reduction peak of TMB (Ox) was measured by using differential pulse voltammetry (DPV) analysis. Based on the results, the electrochemical surface area was increased from 0.396 cm² to 1.298 cm² due to the

  14. Electrochemically reduced graphene oxide-based electrochemical sensor for the sensitive determination of ferulic acid in A. sinensis and biological samples

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Linjie [School of Pharmacy, Lanzhou University, Lanzhou 730000 (China); Gou, Yuqiang [Lanzhou Military Command Center for Disease Prevention and Control, Lanzhou 730000 (China); Gao, Xia; Zhang, Pei; Chen, Wenxia; Feng, Shilan [School of Pharmacy, Lanzhou University, Lanzhou 730000 (China); Hu, Fangdi, E-mail: hufd@lzu.edu.cn [School of Pharmacy, Lanzhou University, Lanzhou 730000 (China); Li, Yingdong, E-mail: lydj412@163.com [Gansu College of Tradition Chinese Medicine, Lanzhou 730000 (China)

    2014-09-01

    An electrochemically reduced graphene oxide (ERGO) modified glassy carbon electrode (GCE) was used as a new voltammetric sensor for the determination of ferulic acid (FA). The morphology and microstructure of the modified electrodes were characterized by scanning electron microscopy (SEM) and Raman spectroscopy analysis, and the electrochemical effective surface areas of the modified electrodes were also calculated by chronocoulometry method. Sensing properties of the electrochemical sensor were investigated by means of cyclic voltammetry (CV) and differential pulse voltammetry (DPV). It was found that ERGO was electrodeposited on the surface of GCE by using potentiostatic method. The proposed electrode exhibited electrocatalytic activity to the redox of FA because of excellent electrochemical properties of ERGO. The transfer electron number (n), electrode reaction rate constant (k{sub s}) and electron-transfer coefficient (α) were calculated as 1.12, 1.24 s{sup −1}, and 0.40, respectively. Under the optimized conditions, the oxidation peak current was proportional to FA concentration at 8.49 × 10{sup −8} mol L{sup −1} to 3.89 × 10{sup −5} mol L{sup −1} with detection limit of 2.06 × 10{sup −8} mol L{sup −1}. This fabricated sensor also displayed acceptable reproducibility, long-term stability, and high selectivity with negligible interferences from common interfering species. The voltammetric sensor was successfully applied to detect FA in A. sinensis and biological samples with recovery values in the range of 99.91%-101.91%. - Highlights: • A novel ERGO–based electrochemical sensor of FA was successfully fabricated by using one-step electrodeposition method. • The electrode reaction was an adsorption–diffusion mixed controlled process. • The low detection limit with good selectivity and sensitivity were obtained. • This method was applied for the determination of FA in A. sinensis and biological samples.

  15. Asymptotic theory for the sample covariance matrix of a heavy-tailed multivariate time series

    DEFF Research Database (Denmark)

    Davis, Richard A.; Mikosch, Thomas Valentin; Pfaffel, Olivier

    2016-01-01

    In this paper we give an asymptotic theory for the eigenvalues of the sample covariance matrix of a multivariate time series. The time series constitutes a linear process across time and between components. The input noise of the linear process has regularly varying tails with index α∈(0,4) in...... particular, the time series has infinite fourth moment. We derive the limiting behavior for the largest eigenvalues of the sample covariance matrix and show point process convergence of the normalized eigenvalues. The limiting process has an explicit form involving points of a Poisson process and eigenvalues...... of a non-negative definite matrix. Based on this convergence we derive limit theory for a host of other continuous functionals of the eigenvalues, including the joint convergence of the largest eigenvalues, the joint convergence of the largest eigenvalue and the trace of the sample covariance matrix...

  16. Investigation of Electrochemical and Morphological Properties of Mixed Matrix Polysulfone-Silica Anion Exchange Membrane

    Directory of Open Access Journals (Sweden)

    Khoiruddin

    2016-02-01

    Full Text Available Mixed matrix anion exchange membranes (AEMs were synthesized using dry-wet phase inversion. The casting solutions were prepared by dispersing finely ground anion-exchange resin particles in N,N-dimethylacetamide (DMAc solutions of polysulfone (PSf. Subsequently, nanosilica particles were introduced into the membranes. The results show that evaporation time (tev and solution composition contributed to membrane properties formation. A longer tev produces membranes with reduced void fraction inside the membranes, thus the amount of water adsorbed and membrane conductivity are reduced. Meanwhile, the permselectivity was improved by increasing tev, since a longer tev produces membranes with a narrower channel for ion migration and more effective Donnan exclusion. The incorporation of 0.5 %-wt nanosilica particles into the polymer matrix led to conductivity improvement (from 2.27 to 3.41 mS.cm-1. This may be associated with additional pathway formation by hydroxyl groups on the silica surface that entraps water and assists ion migration. However, at further silica loading (1.0 and 1.5 %-wt, these properties decreased (to 1.9 and 1.4 mS.cm-1 respectively, which attributed to inaccessibility of ion-exchange functional groups due to membrane compactness. It was found from the results that nanosilica contributes to membrane formation (increases casting solution viscosity then reduces void fraction and membrane functional group addition (provides hydroxyl groups.

  17. Testing of a Microfluidic Sampling System for High Temperature Electrochemical MC&A

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, Candido [Argonne National Lab. (ANL), Argonne, IL (United States); Nichols, Kevin [Argonne National Lab. (ANL), Argonne, IL (United States)

    2013-11-27

    This report describes the preliminary validation of a high-temperature microfluidic chip system for sampling of electrochemical process salt. Electroanalytical and spectroscopic techniques are attractive candidates for improvement through high-throughput sample analysis via miniaturization. Further, microfluidic chip systems are amenable to micro-scale chemical processing such as rapid, automated sample purification to improve sensor performance. The microfluidic chip was tested to determine the feasibility of the system for high temperature applications and conditions under which microfluidic systems can be used to generate salt droplets at process temperature to support development of material balance and control systems in a used fuel treatment facility. In FY13, the project focused on testing a quartz microchip device with molten salts at near process temperatures. The equipment was installed in glove box and tested up to 400°C using commercial thermal transfer fluids as the carrier phase. Preliminary tests were carried out with a low-melting halide salt to initially characterize the properties of this novel liquid-liquid system and to investigate the operating regimes for inducing droplet flow within candidate carrier fluids. Initial results show that the concept is viable for high temperature sampling but further development is required to optimize the system to operate with process relevant molten salts.

  18. Effects of sample size on estimates of population growth rates calculated with matrix models.

    Directory of Open Access Journals (Sweden)

    Ian J Fiske

    Full Text Available BACKGROUND: Matrix models are widely used to study the dynamics and demography of populations. An important but overlooked issue is how the number of individuals sampled influences estimates of the population growth rate (lambda calculated with matrix models. Even unbiased estimates of vital rates do not ensure unbiased estimates of lambda-Jensen's Inequality implies that even when the estimates of the vital rates are accurate, small sample sizes lead to biased estimates of lambda due to increased sampling variance. We investigated if sampling variability and the distribution of sampling effort among size classes lead to biases in estimates of lambda. METHODOLOGY/PRINCIPAL FINDINGS: Using data from a long-term field study of plant demography, we simulated the effects of sampling variance by drawing vital rates and calculating lambda for increasingly larger populations drawn from a total population of 3842 plants. We then compared these estimates of lambda with those based on the entire population and calculated the resulting bias. Finally, we conducted a review of the literature to determine the sample sizes typically used when parameterizing matrix models used to study plant demography. CONCLUSIONS/SIGNIFICANCE: We found significant bias at small sample sizes when survival was low (survival = 0.5, and that sampling with a more-realistic inverse J-shaped population structure exacerbated this bias. However our simulations also demonstrate that these biases rapidly become negligible with increasing sample sizes or as survival increases. For many of the sample sizes used in demographic studies, matrix models are probably robust to the biases resulting from sampling variance of vital rates. However, this conclusion may depend on the structure of populations or the distribution of sampling effort in ways that are unexplored. We suggest more intensive sampling of populations when individual survival is low and greater sampling of stages with high

  19. Effects of sample size on estimates of population growth rates calculated with matrix models.

    Science.gov (United States)

    Fiske, Ian J; Bruna, Emilio M; Bolker, Benjamin M

    2008-08-28

    Matrix models are widely used to study the dynamics and demography of populations. An important but overlooked issue is how the number of individuals sampled influences estimates of the population growth rate (lambda) calculated with matrix models. Even unbiased estimates of vital rates do not ensure unbiased estimates of lambda-Jensen's Inequality implies that even when the estimates of the vital rates are accurate, small sample sizes lead to biased estimates of lambda due to increased sampling variance. We investigated if sampling variability and the distribution of sampling effort among size classes lead to biases in estimates of lambda. Using data from a long-term field study of plant demography, we simulated the effects of sampling variance by drawing vital rates and calculating lambda for increasingly larger populations drawn from a total population of 3842 plants. We then compared these estimates of lambda with those based on the entire population and calculated the resulting bias. Finally, we conducted a review of the literature to determine the sample sizes typically used when parameterizing matrix models used to study plant demography. We found significant bias at small sample sizes when survival was low (survival = 0.5), and that sampling with a more-realistic inverse J-shaped population structure exacerbated this bias. However our simulations also demonstrate that these biases rapidly become negligible with increasing sample sizes or as survival increases. For many of the sample sizes used in demographic studies, matrix models are probably robust to the biases resulting from sampling variance of vital rates. However, this conclusion may depend on the structure of populations or the distribution of sampling effort in ways that are unexplored. We suggest more intensive sampling of populations when individual survival is low and greater sampling of stages with high elasticities.

  20. Spectroscopic and electrochemical characterization of cytochrome c encapsulated in a bio sol-gel matrix.

    Science.gov (United States)

    Deriu, Daniela; Pagnotta, Sara Emanuela; Santucci, Roberto; Rosato, Nicola

    2008-08-01

    Sol-gel technique represents a remarkably versatile method for protein encapsulation. To enhance sol-gel biocompatibility, systems envisaging the presence of calcium and phosphates in the sol-gel composition were recently prepared and investigated. Unfortunately, the low pH at which solutions were prepared (pH proteins, because the acidic environment induces protein denaturation. In this paper we apply a new protocol based on the introduction of calcium nitrate to the inorganic phase, with formation of a binary bioactive system. In this case protein encapsulation results versatile and secure, being achieved at a pH close to neutrality (pH 6.0); also, the presence of calcium is expected to enhance system biocompatibility. To determine the properties of the salt-doped sol-gel and the influence exerted on entrapped biosystems, the structural and functional properties of embedded cytochrome c have been investigated. Data obtained indicate that the salt-doped sol-gel induces no significant change in the structure and the redox properties of the embedded protein; also, the matrix increases protein stability. Interestingly, the presence of calcium nitrate appears determinant for refolding of the acid-denatured protein. This is of interest in the perspective of future applications in biosensoristic area.

  1. Electrochemical analysis of antichemotherapeutic drug zanosar in pharmaceutical and biological samples by differential pulse polarography.

    Science.gov (United States)

    Reddy, Chennupalle Nageswara; Reddyprasad, Puthalapattu; Sreedhar, Neelamyughandhar

    2013-01-01

    The electrochemical reduction of zanosar was investigated systematically by direct current polarography, cyclic voltammetry, and differential pulse polarography (DPP). A simple DPP technique was proposed for the direct quantitative determination of anticancer drug zanosar in pharmaceutical formulation and spiked human urine samples for the first time. The reduction potential was -0.28 V versus Ag/AgCl with a hanging mercury drop electrode in Britton-Robinson buffer as supporting electrolyte. The dependence of the intensities of currents and potentials on pH, concentration, scan rate, deposition time, and nature of the supporting electrolyte was investigated. The calibration curve was found to be linear with the following equation: y = 0.4041x + 0.012, with a correlation coefficient of 0.992 (R (2)) over a concentration range from 1.0 × 10(-7) M to 1.0 × 10(-3) M. In the present investigation, the achieved limit of detection (LOD) and limit of quantization (LQD) were 7.42 × 10(-8) M and 2.47 × 10(-8) M; respectively. Excipients did not interfere with the determination of zanosar in pharmaceutical formulation and spiked urine samples. Precision and accuracy of the developed method were checked by recovery studies in pharmaceutical formulation and spiked human urine samples.

  2. Electrochemical Analysis of Antichemotherapeutic Drug Zanosar in Pharmaceutical and Biological Samples by Differential Pulse Polarography

    Directory of Open Access Journals (Sweden)

    Chennupalle Nageswara Reddy

    2013-01-01

    Full Text Available The electrochemical reduction of zanosar was investigated systematically by direct current polarography, cyclic voltammetry, and differential pulse polarography (DPP. A simple DPP technique was proposed for the direct quantitative determination of anticancer drug zanosar in pharmaceutical formulation and spiked human urine samples for the first time. The reduction potential was −0.28 V versus Ag/AgCl with a hanging mercury drop electrode in Britton-Robinson buffer as supporting electrolyte. The dependence of the intensities of currents and potentials on pH, concentration, scan rate, deposition time, and nature of the supporting electrolyte was investigated. The calibration curve was found to be linear with the following equation: y=0.4041x+0.012, with a correlation coefficient of 0.992 (R2 over a concentration range from 1.0×10-7 M to 1.0×10-3 M. In the present investigation, the achieved limit of detection (LOD and limit of quantization (LQD were 7.42×10-8 M and 2.47×10-8 M; respectively. Excipients did not interfere with the determination of zanosar in pharmaceutical formulation and spiked urine samples. Precision and accuracy of the developed method were checked by recovery studies in pharmaceutical formulation and spiked human urine samples.

  3. Preparation of Environmental and Food Samples to Support the Heavy Metals Detection by Stripping Electrochemical

    International Nuclear Information System (INIS)

    Iswani S

    2002-01-01

    Preparation of environmental and food samples to support the heavy metals detection by stripping electrochemistry was done. The water samples taken directly from the ground water were acidified with 1 mL of HNO 3 acic suprapure was not digested, while the soils samples which have already dried in the oven at 105 o C, ware grinded and sieved through 150 μm, werte digested with HNO 3 acic suprapure in the digestion bomb at 150 o C for 3-4 hours. The mussels samples which have already freezed in the freezer were peeled, dried with N 2 liquid, grinded and dried again in the freeze drier at the pressure of ≅ 10 -2 mBar, and then were grinded again, weighted, digested with HNO 3 acic and HClO 4 suprapure in the digestion bomb at 150 o C for 3 hours. Food samples were homogenized by electric mixer, dried with freeze dried, homogenized again by using ZrO 2 ball mill, weighted, digested by HPA (high Pressure Asher). The heavy metals in the food samples solution of digestion product were detected by using Polarographic Analyzer EGandG of SWV and DPASV methods, while in the water, soils and the mussels solution were detected by using PDV 2000 and Polarograf E-505, DPASV method. The method validity were tested with SRM materials such as soil-5, soil-7, water W-4, and coppepoda. The heavy metals detection results in the water, soils, mussels, and food by electrochemical method were reported in this paper. (author)

  4. Integrating Electrochemical Detection with Centrifugal Microfluidics for Real-Time and Fully Automated Sample Testing

    DEFF Research Database (Denmark)

    Andreasen, Sune Zoëga; Kwasny, Dorota; Amato, Letizia

    2015-01-01

    Here we present a robust, stable and low-noise experimental set-up for performing electrochemical detection on a centrifugal microfluidic platform. By using a low-noise electronic component (electrical slip-ring) it is possible to achieve continuous, on-line monitoring of electrochemical experime......Here we present a robust, stable and low-noise experimental set-up for performing electrochemical detection on a centrifugal microfluidic platform. By using a low-noise electronic component (electrical slip-ring) it is possible to achieve continuous, on-line monitoring of electrochemical...

  5. Tribological performance of titanium samples oxidized by fs-laser radiation, thermal heating, or electrochemical anodization

    Science.gov (United States)

    Kirner, S. V.; Slachciak, N.; Elert, A. M.; Griepentrog, M.; Fischer, D.; Hertwig, A.; Sahre, M.; Dörfel, I.; Sturm, H.; Pentzien, S.; Koter, R.; Spaltmann, D.; Krüger, J.; Bonse, J.

    2018-04-01

    Commercial grade-1 titanium samples (Ti, 99.6%) were treated using three alternative methods, (i) femtosecond laser processing, (ii) thermal heat treatment, and (iii) electrochemical anodization, respectively, resulting in the formation of differently conditioned superficial titanium oxide layers. The laser processing (i) was carried out by a Ti:sapphire laser (pulse duration 30 fs, central wavelength 790 nm, pulse repetition rate 1 kHz) in a regime of generating laser-induced periodic surface structures (LIPSS). The experimental conditions (laser fluence, spatial spot overlap) were optimized in a sample-scanning setup for the processing of several square-millimeters large surface areas covered homogeneously by these nanostructures. The differently oxidized titanium surfaces were characterized by optical microscopy, micro Raman spectroscopy, variable angle spectroscopic ellipsometry, and instrumented indentation testing. The tribological performance was characterized in the regime of mixed friction by reciprocating sliding tests against a sphere of hardened steel in fully formulated engine oil as lubricant. The specific tribological performance of the differently treated surfaces is discussed with respect to possible physical and chemical mechanisms.

  6. Effect of the sample matrix on measurement uncertainty in X-ray fluorescence analysis

    International Nuclear Information System (INIS)

    Morgenstern, P.; Brueggemann, L.; Wennrich, R.

    2005-01-01

    The estimation of measurement uncertainty, with reference to univariate calibration functions, is discussed in detail in the Eurachem Guide 'Quantifying Uncertainty in Analytical Measurement'. The adoption of these recommendations to quantitative X-ray fluorescence analysis (XRF) involves basic problems which are above all due to the strong influence of the sample matrix on the analytical response. In XRF-analysis, the proposed recommendations are consequently applicable only to the matrix corrected response. The application is also restricted with regard to both the matrices and analyte concentrations. In this context the present studies are aimed at the problems to predict measurement uncertainty also with reference to more variable sample compositions. The corresponding investigations are focused on the use of the intensity of the Compton scattered tube line as an internal standard to assess the effect of the individual sample matrix on the analytical response relatively to a reference matrix. Based on this concept the estimation of the measurement uncertainty of an analyte presented in an unknown specimen can be predicted in consideration of the data obtained under defined matrix conditions

  7. LIBS detection of heavy metal elements in liquid solutions by using wood pellet as sample matrix

    International Nuclear Information System (INIS)

    Wen Guanhong; Sun Duixiong; Su Maogen; Dong Chenzhong

    2013-01-01

    Laser-induced breakdown spectroscopy (LIBS) has been applied to the analysis of heavy metals in liquid sample. A new approach was presented to improve the detection limit and minimize the sample matrix effects, in which dried wood pellets absorbed the given amounts of Cr standard solutions and then were baked because they have stronger and rapid absorption properties for liquid samples as well as simple elemental compositions. In this work, we have taken a typical heavy metal Cr element as an example, and investigated the spectral feasibility of Cr solutions and dried wood pellets before and after absorbing Cr solutions at the same experimental conditions, respectively. The results were demonstrated to successfully produce a superior analytical response for heavy metal elements by using wood pellet as sample matrix according to obtained LOD of 0.07 ppm for Cr element in solutions. (author)

  8. LIBS Detection of Heavy Metal Elements in Liquid Solutions by Using Wood Pellet as Sample Matrix

    International Nuclear Information System (INIS)

    Wen Guanhong; Sun Duixiong; Su Maogen; Dong Chenzhong

    2014-01-01

    Laser-induced breakdown spectroscopy (LIBS) has been applied to the analysis of heavy metals in liquid samples. A new approach was presented to lower the limit of detection (LOD) and minimize the sample matrix effects, in which dried wood pellets absorbed the given amounts of Cr standard solutions and then were baked because they have stronger and rapid absorption properties for liquid samples as well as simple elemental compositions. In this work, we have taken a typical heavy metal Cr element as an example, and investigated the spectral feasibility of Cr solutions and dried wood pellets before and after absorbing Cr solutions at the same experimental conditions. The results were demonstrated to successfully produce a superior analytical response for heavy metal elements by using wood pellet as sample matrix according to the obtained LOD of 0.07 ppm for Cr element in solutions

  9. MALDI (matrix assisted laser desorption ionization) Imaging Mass Spectrometry (IMS) of skin: Aspects of sample preparation.

    Science.gov (United States)

    de Macedo, Cristiana Santos; Anderson, David M; Schey, Kevin L

    2017-11-01

    MALDI (matrix assisted laser desorption ionization) Imaging Mass Spectrometry (IMS) allows molecular analysis of biological materials making possible the identification and localization of molecules in tissues, and has been applied to address many questions on skin pathophysiology, as well as on studies about drug absorption and metabolism. Sample preparation for MALDI IMS is the most important part of the workflow, comprising specimen collection and preservation, tissue embedding, cryosectioning, washing, and matrix application. These steps must be carefully optimized for specific analytes of interest (lipids, proteins, drugs, etc.), representing a challenge for skin analysis. In this review, critical parameters for MALDI IMS sample preparation of skin samples will be described. In addition, specific applications of MALDI IMS of skin samples will be presented including wound healing, neoplasia, and infection. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Matrix effects in PIXE evaluation of the major components in thick homogeneous samples

    International Nuclear Information System (INIS)

    Oystaeyen, B. van; Demortier, G.

    1983-01-01

    Matrix effects on the major component X-ray yields in PIXE measurements are studied in general terms with the Au-Cu-Ag matrix as practical example. Postulating firstly that all the major components may be simultaneously detected through one well-isolated peak for each of them, and secondly that a known reference material is available which contains all the elements of the unknown sample, we propose a direct method to extract the true concentrations of the latter taking into accout the matrix effects. The geometrical parameters describing the target location with respect to ion beam direction and detector position are also studied and a first attempt is made to include them in the data treatment. (orig.)

  11. Matrix effect study in the determination of linear alkylbenzene sulfonates in sewage sludge samples.

    Science.gov (United States)

    Cantarero, Samuel; Zafra-Gómez, Alberto; Ballesteros, Oscar; Navalón, Alberto; Vílchez, José L; Verge, Coral; De Ferrer, Juan A

    2011-04-01

    We propose a study of the matrix effect in the determination of linear alkylbenzene sulfonates (LAS) in sewage sludge samples. First, a rapid, selective and sensitive method is proposed. The method involves two stages: the extraction of the compound from the samples and analysis by liquid chromatography with fluorescence detection (LC-FLD). Three different techniques of extraction (microwave-assisted extraction, Soxhlet, and ultrasounds) were compared, and microwave-assisted extraction was selected as the best suited for our purpose. Microwave-assisted extraction allows reducing the extraction time (25 min compared with 12 h for conventional Soxhlet extraction) and solvent waste (25 ml of methanol compared with 200 ml for Soxhlet or more than 50 ml for the ultrasonic procedure). Absence of matrix effect was evaluated with two standards (2ØC(8:0) and 2ØC(16:0) ) that are not commercial; therefore, neither of them was detected in sewage sludge samples and they showed similar environmental behavior (adsorption and precipitation) to LAS (C(11:0) -C(13.0) ), which allow us to evaluate the matrix effect. Validation was carried out by a recovery assay, and the method was applied to samples from different sources; therefore, they had different compositions. Copyright © 2011 SETAC.

  12. Exploiting multi-function Metal-Organic Framework nanocomposite Ag@Zn-TSA as highly efficient immobilization matrixes for sensitive electrochemical biosensing.

    Science.gov (United States)

    Dong, Sheying; Zhang, Dandan; Suo, Gaochao; Wei, Wenbo; Huang, Tinglin

    2016-08-31

    A novel multi-function Metal-Organic Framework composite Ag@Zn-TSA (zinc thiosalicylate, Zn(C7H4O2S), Zn-TSA) was synthesized as highly efficient immobilization matrixes of myoglobin (Mb)/glucose oxidase (GOx) for electrochemical biosensing. The electrochemical biosensors based on Ag@Zn-TSA composite and ionic liquid (IL) modified carbon paste electrode (CPE) were fabricated successfully. Furthermore, the properties of the sensors were discussed by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and amperometric current-time curve, respectively. The results showed the proposed biosensors had wide linear response to hydrogen peroxide (H2O2) in the range of 0.3-20,000 μM, to nitrite (NO2(-)) for 1.3 μM-1660 μM and 2262 μM-1,33,000 μM, to glucose for 2.0-1022 μM, with a low detection limit of 0.08 μM for H2O2, 0.5 μM for NO2(-), 0.8 μM for glucose. The values of the apparent heterogeneous electron transfer rate constant (ks) for Mb and GOx were estimated as 2.05 s(-1) and 2.45 s(-1), respectively. Thus, Ag@Zn-TSA was a kind of ideal material as highly efficient immobilization matrixes for sensitive electrochemical biosensing. In addition, this work indicated that MOF nanocomposite had a great potential for constructing wide range of sensing interface. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Characterizing full matrix constants of piezoelectric single crystals with strong anisotropy using two samples

    Science.gov (United States)

    Tang, Liguo; Zhang, Yang; Cao, Wenwu

    2016-10-01

    Although the self-consistency of the full matrix material constants of a piezoelectric sample obtained by the resonant ultrasonic spectroscopy technique can be guaranteed because all constants come from the same sample, it is a great challenge to determine the constants of a piezoelectric sample with strong anisotropy because it might not be possible to identify enough resonance modes from the resonance spectrum. To overcome this difficulty, we developed a strategy to use two samples of similar geometries to increase the number of easy identifiable modes. Unlike the IEEE resonance methods, sample-to-sample variation here is negligible because the two samples have almost the same dimensions, cut from the same specimen and poled under the same conditions. Using this method, we have measured the full matrix constants of a [011]c poled 0.71Pb(Mg1/3Nb2/3)O3-0.29PbTiO3 single crystal, which has 17 independent constants. The self-consistency of the obtained results is checked by comparing the calculated elastic stiffness constants c33 D , c44 D , and c55 D with those directly measured ones using the ultrasonic pulse-echo method.

  14. An Overview of Pesticide Monitoring at Environmental Samples Using Carbon Nanotubes-Based Electrochemical Sensors

    Directory of Open Access Journals (Sweden)

    Ademar Wong

    2017-03-01

    Full Text Available Carbon nanotubes have received enormous attention in the development of electrochemical sensors by promoting electron transfer reactions, decreasing the work overpotential within great surface areas. The growing concerns about environmental health emphasized the necessity of continuous monitoring of pollutants. Pesticides have been successfully used to control agricultural and public health pests; however, intense use can cause a number of damages for biodiversity and human health. In this sense, carbon nanotubes-based electrochemical sensors have been proposed for pesticide monitoring combining different electrode modification strategies and electroanalytical techniques. In this paper, we provide a review of the recent advances in the use of carbon nanotubes for the construction of electrochemical sensors dedicated to the environmental monitoring of pesticides. Future directions, perspectives, and challenges are also commented.

  15. Some remarks on estimating a covariance structure model from a sample correlation matrix

    OpenAIRE

    Maydeu Olivares, Alberto; Hernández Estrada, Adolfo

    2000-01-01

    A popular model in structural equation modeling involves a multivariate normal density with a structured covariance matrix that has been categorized according to a set of thresholds. In this setup one may estimate the covariance structure parameters from the sample tetrachoricl polychoric correlations but only if the covariance structure is scale invariant. Doing so when the covariance structure is not scale invariant results in estimating a more restricted covariance structure than the one i...

  16. Molecularly imprinted polymer-matrix nanocomposite for enantioselective electrochemical sensing of D- and L-aspartic acid.

    Science.gov (United States)

    Prasad, Bhim Bali; Srivastava, Amrita; Tiwari, Mahavir Prasad

    2013-10-01

    A new molecularly imprinted polymer-matrix (titanium dioxide nanoparticle/multiwalled carbon nanotubes) nanocomposite was developed for the modification of pencil graphite electrode as an enantioselective sensing probe for aspartic acid isomers, prevalent at ultra trace level in aqueous and real samples. The nanocomposite having many shape complementary cavities was synthesized adopting surface initiated-activators regenerated by electron transfer for atom transfer radical polymerization. The proposed sensor has high stability, nanocomposite uniformity, good reproducibility, and enhanced electrocatalytic activity to respond oxidative peak current of L-aspartic acid quantitatively by differential pulse anodic stripping voltammetry, without any cross-reactivity in real samples. Under the optimized operating conditions, the L-aspartic acid imprinted modified electrode showed a wide linear response for L-aspartic acid within the concentration range 9.98-532.72 ng mL(-1), with the minimum detection limit of 1.73-1.79 ng mL(-1) (S/N=3) in aqueous and real samples. Almost similar stringent limit (1.79 ng mL(-1)) was obtained with cerebrospinal fluid which is typical for the primitive diagnosis of neurological disorders, caused by an acute depletion of L-aspartic acid biomarker, in clinical settings. Copyright © 2013 Elsevier B.V. All rights reserved.

  17. Accounting for Sampling Error in Genetic Eigenvalues Using Random Matrix Theory.

    Science.gov (United States)

    Sztepanacz, Jacqueline L; Blows, Mark W

    2017-07-01

    The distribution of genetic variance in multivariate phenotypes is characterized by the empirical spectral distribution of the eigenvalues of the genetic covariance matrix. Empirical estimates of genetic eigenvalues from random effects linear models are known to be overdispersed by sampling error, where large eigenvalues are biased upward, and small eigenvalues are biased downward. The overdispersion of the leading eigenvalues of sample covariance matrices have been demonstrated to conform to the Tracy-Widom (TW) distribution. Here we show that genetic eigenvalues estimated using restricted maximum likelihood (REML) in a multivariate random effects model with an unconstrained genetic covariance structure will also conform to the TW distribution after empirical scaling and centering. However, where estimation procedures using either REML or MCMC impose boundary constraints, the resulting genetic eigenvalues tend not be TW distributed. We show how using confidence intervals from sampling distributions of genetic eigenvalues without reference to the TW distribution is insufficient protection against mistaking sampling error as genetic variance, particularly when eigenvalues are small. By scaling such sampling distributions to the appropriate TW distribution, the critical value of the TW statistic can be used to determine if the magnitude of a genetic eigenvalue exceeds the sampling error for each eigenvalue in the spectral distribution of a given genetic covariance matrix. Copyright © 2017 by the Genetics Society of America.

  18. Tuning of structural, light emission and wetting properties of nanostructured copper oxide-porous silicon matrix formed on electrochemically etched copper-coated silicon substrates

    Science.gov (United States)

    Naddaf, M.

    2017-01-01

    Matrices of copper oxide-porous silicon nanostructures have been formed by electrochemical etching of copper-coated silicon surfaces in HF-based solution at different etching times (5-15 min). Micro-Raman, X-ray diffraction and X-ray photoelectron spectroscopy results show that the nature of copper oxide in the matrix changes from single-phase copper (I) oxide (Cu2O) to single-phase copper (II) oxide (CuO) on increasing the etching time. This is accompanied with important variation in the content of carbon, carbon hydrides, carbonyl compounds and silicon oxide in the matrix. The matrix formed at the low etching time (5 min) exhibits a single broad "blue" room-temperature photoluminescence (PL) band. On increasing the etching time, the intensity of this band decreases and a much stronger "red" PL band emerges in the PL spectra. The relative intensity of this band with respect to the "blue" band significantly increases on increasing the etching time. The "blue" and "red" PL bands are attributed to Cu2O and porous silicon of the matrix, respectively. In addition, the water contact angle measurements reveal that the hydrophobicity of the matrix surface can be tuned from hydrophobic to superhydrophobic state by controlling the etching time.

  19. Matrix modifiers application during microimpurities determination in complex samples by electrothermal atomic-absorption spectrometry

    International Nuclear Information System (INIS)

    Bejzel', N.F.; Daaman, F.I.; Fuks-Pol', G.R.; Yudelevich, I.G.

    1993-01-01

    The review covers publications of primarily last 5 years and is devoted to the use of matrix modifiers (MM) for the determinations of trace impurities in complex samples by electrothermal atomic-absorption analysis. The role of MM in analytical process has been discussed as well as MM influence on all the elements of analytical system; factors, determining the effectiveness of MM action, the basis types of MM have been described. A great body of information is tabulated on the use of different MM for the determination of particular analysis in geological, medicobiological, technological, ecological samples and in pure materials and chemicals

  20. Matrix modification for determination of microimpurities in complex samples by electrothermal atomic-absorption spectrometry

    International Nuclear Information System (INIS)

    Bejzel', N.F.; Daaman, F.I.; Fuks-Pol', G.R.; Yudelevich, I.G.

    1993-01-01

    The review covers publications of primarily last 5 years and is devoted to the use of matrix modifiers (MM) for the determinations of trace impurities in complex samples by electrothermal atomic-absorption analysis. The role of MM in analytical process has been discussed as well as MM influence on all the elements of analytical system; factors, determining the effectiveness of MM action, the basis types of MM have been described. A great body of information is tabulated on the use of different MM for the determination of particular analysis in geological, medicobiological, technological, ecological samples and in pure materials and chemicals

  1. Ternary monolayers as DNA recognition interfaces for direct and sensitive electrochemical detection in untreated clinical samples

    Czech Academy of Sciences Publication Activity Database

    Campuzano, S.; Kuralay, F.; Lobo-Castanón, M.J.; Bartošík, Martin; Vyavahare, K.; Paleček, Emil; Haake, D.A.; Wang, J.

    2011-01-01

    Roč. 26, č. 8 (2011), s. 3577-3583 ISSN 0956-5663 R&D Projects: GA MŠk(CZ) ME09038 Institutional research plan: CEZ:AV0Z50040507; CEZ:AV0Z50040702 Keywords : electrochemical detection * DNA hybridization * self-assembled monolayer Subject RIV: BO - Biophysics Impact factor: 5.602, year: 2011

  2. Virtual electrochemical nitric oxide analyzer using copper, zinc superoxide dismutase immobilized on carbon nanotubes in polypyrrole matrix.

    Science.gov (United States)

    Madasamy, Thangamuthu; Pandiaraj, Manickam; Balamurugan, Murugesan; Karnewar, Santosh; Benjamin, Alby Robson; Venkatesh, Krishna Arun; Vairamani, Kanagavel; Kotamraju, Srigiridhar; Karunakaran, Chandran

    2012-10-15

    In this work, we have designed and developed a novel and cost effective virtual electrochemical analyzer for the measurement of NO in exhaled breath and from hydrogen peroxide stimulated endothelial cells using home-made potentiostat. Here, data acquisition system (NI MyDAQ) was used to acquire the data from the electrochemical oxidation of NO mediated by copper, zinc superoxide dismutase (Cu,ZnSOD). The electrochemical control programs (graphical user-interface software) were developed using LabVIEW 10.0 to sweep the potential, acquire the current response and process the acquired current signal. The Cu,ZnSOD (SOD1) immobilized on the carbon nanotubes in polypyrrole modified platinum electrode was used as the NO biosensor. The electrochemical behavior of the SOD1 modified electrode exhibited the characteristic quasi-reversible redox peak at the potential, +0.06 V vs. Ag/AgCl. The biological interferences were eliminated by nafion coated SOD1 electrode and then NO was measured selectively. Further, this biosensor showed a wide linear range of response over the concentration of NO from 0.1 μM to 1 mM with a detection limit of 0.1 μM and high sensitivity of 1.1 μA μM(-1). The electroanalytical results obtained here using the developed virtual electrochemical instrument were also compared with the standard cyclic voltammetry instrument and found in agreement with each other. Copyright © 2012 Elsevier B.V. All rights reserved.

  3. Baseline Design Compliance Matrix for the Rotary Mode Core Sampling System

    International Nuclear Information System (INIS)

    LECHELT, J.A.

    2000-01-01

    The purpose of the design compliance matrix (DCM) is to provide a single-source document of all design requirements associated with the fifteen subsystems that make up the rotary mode core sampling (RMCS) system. It is intended to be the baseline requirement document for the RMCS system and to be used in governing all future design and design verification activities associated with it. This document is the DCM for the RMCS system used on Hanford single-shell radioactive waste storage tanks. This includes the Exhauster System, Rotary Mode Core Sample Trucks, Universal Sampling System, Diesel Generator System, Distribution Trailer, X-Ray Cart System, Breathing Air Compressor, Nitrogen Supply Trailer, Casks and Cask Truck, Service Trailer, Core Sampling Riser Equipment, Core Sampling Support Trucks, Foot Clamp, Ramps and Platforms and Purged Camera System. Excluded items are tools such as light plants and light stands. Other items such as the breather inlet filter are covered by a different design baseline. In this case, the inlet breather filter is covered by the Tank Farms Design Compliance Matrix

  4. Exploiting multi-function Metal-Organic Framework nanocomposite Ag@Zn-TSA as highly efficient immobilization matrixes for sensitive electrochemical biosensing

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Sheying, E-mail: dongsyy@126.com [College of Sciences, Xi' an University of Architecture and Technology, Xi' an, 710055 (China); Zhang, Dandan; Suo, Gaochao; Wei, Wenbo [College of Sciences, Xi' an University of Architecture and Technology, Xi' an, 710055 (China); Huang, Tinglin [School of Environmental and Municipal Engineering, Xi' an University of Architecture and Technology, Xi' an, 710055 (China)

    2016-08-31

    A novel multi-function Metal-Organic Framework composite Ag@Zn-TSA (zinc thiosalicylate, Zn(C{sub 7}H{sub 4}O{sub 2}S), Zn-TSA) was synthesized as highly efficient immobilization matrixes of myoglobin (Mb)/glucose oxidase (GOx) for electrochemical biosensing. The electrochemical biosensors based on Ag@Zn-TSA composite and ionic liquid (IL) modified carbon paste electrode (CPE) were fabricated successfully. Furthermore, the properties of the sensors were discussed by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and amperometric current-time curve, respectively. The results showed the proposed biosensors had wide linear response to hydrogen peroxide (H{sub 2}O{sub 2}) in the range of 0.3–20,000 μM, to nitrite (NO{sub 2}{sup −}) for 1.3 μM–1660 μM and 2262 μM–1,33,000 μM, to glucose for 2.0–1022 μM, with a low detection limit of 0.08 μM for H{sub 2}O{sub 2}, 0.5 μM for NO{sub 2}{sup −}, 0.8 μM for glucose. The values of the apparent heterogeneous electron transfer rate constant (k{sub s}) for Mb and GOx were estimated as 2.05 s{sup −1} and 2.45 s{sup −1}, respectively. Thus, Ag@Zn-TSA was a kind of ideal material as highly efficient immobilization matrixes for sensitive electrochemical biosensing. In addition, this work indicated that MOF nanocomposite had a great potential for constructing wide range of sensing interface. - Highlights: • Novel Ag@Zn-TSA was used as highly efficient immobilization matrixes of Mb/glucose. • We exploited multi-function MOFs for a wide range of electrocatalytic sensing interface. • The proposed biosensors had an excellent catalytic effect on the small molecule (NO{sub 2}{sup −}, H{sub 2}O{sub 2}, glucose).

  5. Exploiting multi-function Metal-Organic Framework nanocomposite Ag@Zn-TSA as highly efficient immobilization matrixes for sensitive electrochemical biosensing

    International Nuclear Information System (INIS)

    Dong, Sheying; Zhang, Dandan; Suo, Gaochao; Wei, Wenbo; Huang, Tinglin

    2016-01-01

    A novel multi-function Metal-Organic Framework composite Ag@Zn-TSA (zinc thiosalicylate, Zn(C_7H_4O_2S), Zn-TSA) was synthesized as highly efficient immobilization matrixes of myoglobin (Mb)/glucose oxidase (GOx) for electrochemical biosensing. The electrochemical biosensors based on Ag@Zn-TSA composite and ionic liquid (IL) modified carbon paste electrode (CPE) were fabricated successfully. Furthermore, the properties of the sensors were discussed by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and amperometric current-time curve, respectively. The results showed the proposed biosensors had wide linear response to hydrogen peroxide (H_2O_2) in the range of 0.3–20,000 μM, to nitrite (NO_2"−) for 1.3 μM–1660 μM and 2262 μM–1,33,000 μM, to glucose for 2.0–1022 μM, with a low detection limit of 0.08 μM for H_2O_2, 0.5 μM for NO_2"−, 0.8 μM for glucose. The values of the apparent heterogeneous electron transfer rate constant (k_s) for Mb and GOx were estimated as 2.05 s"−"1 and 2.45 s"−"1, respectively. Thus, Ag@Zn-TSA was a kind of ideal material as highly efficient immobilization matrixes for sensitive electrochemical biosensing. In addition, this work indicated that MOF nanocomposite had a great potential for constructing wide range of sensing interface. - Highlights: • Novel Ag@Zn-TSA was used as highly efficient immobilization matrixes of Mb/glucose. • We exploited multi-function MOFs for a wide range of electrocatalytic sensing interface. • The proposed biosensors had an excellent catalytic effect on the small molecule (NO_2"−, H_2O_2, glucose).

  6. Molecularly imprinted polymer-matrix nanocomposite for enantioselective electrochemical sensing of D- and L-aspartic acid

    International Nuclear Information System (INIS)

    Prasad, Bhim Bali; Srivastava, Amrita; Tiwari, Mahavir Prasad

    2013-01-01

    A new molecularly imprinted polymer-matrix (titanium dioxide nanoparticle/multiwalled carbon nanotubes) nanocomposite was developed for the modification of pencil graphite electrode as an enantioselective sensing probe for aspartic acid isomers, prevalent at ultra trace level in aqueous and real samples. The nanocomposite having many shape complementary cavities was synthesized adopting surface initiated-activators regenerated by electron transfer for atom transfer radical polymerization. The proposed sensor has high stability, nanocomposite uniformity, good reproducibility, and enhanced electrocatalytic activity to respond oxidative peak current of L-aspartic acid quantitatively by differential pulse anodic stripping voltammetry, without any cross-reactivity in real samples. Under the optimized operating conditions, the L-aspartic acid imprinted modified electrode showed a wide linear response for L-aspartic acid within the concentration range 9.98–532.72 ng mL −1 , with the minimum detection limit of 1.73–1.79 ng mL −1 (S/N = 3) in aqueous and real samples. Almost similar stringent limit (1.79 ng mL −1 ) was obtained with cerebrospinal fluid which is typical for the primitive diagnosis of neurological disorders, caused by an acute depletion of L-aspartic acid biomarker, in clinical settings. Highlights: • We have adopted surface initiated-activators regenerated by electron transfer for atom transfer radical polymerization. • This approach takes advantage of the nanostructured ultrathin imprinted film. • Successful enantioselective sensing and ultratrace analysis of D- and L-aspartic acid. • Stringent detection limit without any non-specific false-positive contribution

  7. Molecularly imprinted polymer-matrix nanocomposite for enantioselective electrochemical sensing of D- and L-aspartic acid

    Energy Technology Data Exchange (ETDEWEB)

    Prasad, Bhim Bali, E-mail: prof.bbpd@yahoo.com; Srivastava, Amrita; Tiwari, Mahavir Prasad

    2013-10-15

    A new molecularly imprinted polymer-matrix (titanium dioxide nanoparticle/multiwalled carbon nanotubes) nanocomposite was developed for the modification of pencil graphite electrode as an enantioselective sensing probe for aspartic acid isomers, prevalent at ultra trace level in aqueous and real samples. The nanocomposite having many shape complementary cavities was synthesized adopting surface initiated-activators regenerated by electron transfer for atom transfer radical polymerization. The proposed sensor has high stability, nanocomposite uniformity, good reproducibility, and enhanced electrocatalytic activity to respond oxidative peak current of L-aspartic acid quantitatively by differential pulse anodic stripping voltammetry, without any cross-reactivity in real samples. Under the optimized operating conditions, the L-aspartic acid imprinted modified electrode showed a wide linear response for L-aspartic acid within the concentration range 9.98–532.72 ng mL{sup −1}, with the minimum detection limit of 1.73–1.79 ng mL{sup −1} (S/N = 3) in aqueous and real samples. Almost similar stringent limit (1.79 ng mL{sup −1}) was obtained with cerebrospinal fluid which is typical for the primitive diagnosis of neurological disorders, caused by an acute depletion of L-aspartic acid biomarker, in clinical settings. Highlights: • We have adopted surface initiated-activators regenerated by electron transfer for atom transfer radical polymerization. • This approach takes advantage of the nanostructured ultrathin imprinted film. • Successful enantioselective sensing and ultratrace analysis of D- and L-aspartic acid. • Stringent detection limit without any non-specific false-positive contribution.

  8. Nanomolar electrochemical detection of caffeic acid in fortified wine samples based on gold/palladium nanoparticles decorated graphene flakes.

    Science.gov (United States)

    Thangavelu, Kokulnathan; Raja, Nehru; Chen, Shen-Ming; Liao, Wei-Cheng

    2017-09-01

    Amalgamation of noble metal nanomaterials on graphene flakes potentially paves one way to improve their physicochemical properties. This paper deals with the simultaneous electrochemical deposition of gold and palladium nanoparticles on graphene flakes (Au/PdNPs-GRF) for the sensitive determination of caffeic acid (CA). The physiochemical properties of the prepared Au/PdNPs-GRF was characterized by using numerous analytical techniques such as scanning electron microscopy, electron dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray powder diffraction, Raman spectroscopy and electrochemical impedance spectroscopy. The enhanced electrochemical determination of CA at Au/PdNPs deposition on GRF were studied by using cyclic voltammetry and differential pulse voltammetry. In results, Au/PdNPs-GRF electrode exhibited an excellent electrocatalytic activity towards CA with wide linear range and low limit of detection of 0.03-938.97µM and 6nM, respectively. Eventually, the Au/PdNPs-GRF was found as a selective and stable active material for the sensing of CA. In addition, the proposed sensor showed the adequate results in real sample analysis. Copyright © 2017 Elsevier Inc. All rights reserved.

  9. Correlation between Sweet Spots of Glycopeptides and Polymorphism of the Matrix Crystal in MALDI Samples.

    Science.gov (United States)

    Nishikaze, Takashi; Okumura, Hisako; Jinmei, Hiroshi; Amano, Junko

    2012-01-01

    A standard dried-droplet preparation using 2,5-dihydroxybenzoic acid (2,5-DHBA) as the matrix results in a large variation in signal intensity and poor shot-to-shot reproducibility in matrix-assisted laser desorption/ionization (MALDI). We expected that the differences can be attributed to the nature of the crystal structures in the region of the "sweet spot" within the MALDI samples. 2,5-DHBA crystals with and without analytes on a target plate obtained by means of a dried-droplet preparation contain two polymorphs, which can be distinguished by Raman spectra. In comparing the Raman image with the MS image, a clear correlation between the signal distribution of glycopeptides and hydrophilic peptides and the specific crystal form of 2,5-DHBA could be made. The ionization of hydrophobic peptides appears to proceed in both types of polymorphic crystals. In addition, the derivatization of glycopeptides with a pyrene group enabled us to detect glycopeptides regardless the crystal form. As the result, the number of sweet spots increased and MS spectra with a high signal intensity were obtained. The results suggest that the introduction of a hydrophobic/aromatic moiety to glycopeptides results in a more successful MALDI analysis due to the effective incorporation of the analyte into matrix crystals.

  10. A dual amplified electrochemical immunosensor for ofloxacin: Polypyrrole film-Au nanocluster as the matrix and multi-enzyme-antibody functionalized gold nanorod as the label

    International Nuclear Information System (INIS)

    Zang, Shuai; Liu, Yingju; Lin, Mouhong; Kang, Jianli; Sun, Yuanming; Lei, Hongtao

    2013-01-01

    Graphical abstract: Schematic representation of the OFL electrochemical immunosensor using Au nanoclusters/PPy/GCE as the substrate and multi-HRP-GNR-Ab2 bioconjugates as the label. Highlights: ► Gold nanorod was used to load HRP and Ab 2 to form multi-HRP-GNR-Ab 2 . ► A sensitive immunosensor for ofloxacin was constructed using the homemade antibody. ► A dual signal amplified strategy was based on the PPy-Au and multi-HRP-GNR-Ab 2 . -- Abstract: In this work, an electrochemical immunosensor, basing on a dual signal amplified strategy by employing a biocompatible polypyrrole film-Au nanocluster matrix as a sensor platform and multi-enzyme-antibody functionalized gold nanorod as an electrochemical detection label, is established for sensitive detection of ofloxacin (OFL). Firstly, polypyrrole film and Au nanoclusters were progressively fabricated onto the surface of a glassy carbon electrode via electropolymerization and electrochemical deposition, respectively. Such PPy-Au nanocomposite modified electrode was used to immobilize OFL-OVA, blocked with the blocking reagent, and then associated with the corresponding antibody. Secondly, gold nanorod (GNR) was synthesized to load horseradish peroxidase (HRP) and horseradish peroxidase-secondary antibody (HRP-Ab 2 ), and the resulting nanostructure (multi-HRP-GNR-Ab 2 ) was applied as the detection label. The fabrication process of the ordered multilayer structure and immunosensor were characterized by scanning electron microscopy (SEM) and electrochemical measurements, respectively. Finally, based on a competitive immunoassay, i.e., the association ability with the corresponding antibody between the captured antigen and free OFL in the solution, the fabricated immunosensor exhibited a sensitive response to OFL in the range from 0.08 to 410 ng/mL with a detection limit of 0.03 ng/mL. The current immunosensor exhibited good sensitivity, selectivity and long-term stability. This amplification strategy shows excellent

  11. A liquid scintillation counter specifically designed for samples deposited on a flat matrix

    International Nuclear Information System (INIS)

    Potter, C.G.; Warner, G.T.

    1986-01-01

    A prototype liquid scintillation counter has been designed to count samples deposited as a 6x16 array on a flat matrix. Applications include the counting of labelled cells processed by a cell harvester from 96-well microtitration plates onto glass fibre filters and of DNA samples directly deposited onto nitrocellulose or nylon transfer membranes (e.g. 'Genescreen' NEN) for genetic studies by dot-blot hybridisation. The whole filter is placed in a bag with 4-12 ml of scintillant, sufficient to count all 96 samples. Nearest-neighbour intersample cross talk ranged from 0.004% for 3 H to 0.015% for 32 P. Background was 1.4 counts/min for glass fibre and 0.7 counts/min for 'Genescreen' in the 3 H channel: for 14 C the respective figures were 5.3 and 4.3 counts/min. Counting efficiency for 3 H-labelled cells on glass fibre was 54%(E 2 /B=2053) and 26% for tritiated thymidine spotted on 'Genescreen'(E 2 /B=980). Similar 14 C samples gave figures on 97%(E 2 /B=1775) and 81(E 2 B=1526) respectively. Electron emission counting from samples containing 125 I and 51 Cr was also possible. (U.K.)

  12. Fabrication of an electrochemical sensor based on computationally designed molecularly imprinted polymer for the determination of mesalamine in real samples

    Energy Technology Data Exchange (ETDEWEB)

    Torkashvand, M. [Department of Analytical Chemistry, Razi University, Kermanshah (Iran, Islamic Republic of); Gholivand, M.B., E-mail: mbgholivand@yahoo.com [Department of Analytical Chemistry, Razi University, Kermanshah (Iran, Islamic Republic of); Taherkhani, F. [Department of Physical Chemistry, Razi University, Kermanshah (Iran, Islamic Republic of)

    2015-10-01

    A novel electrochemical sensor based on mesalamine molecularly imprinted polymer (MIP) film on a glassy carbon electrode was fabricated. Density functional theory (DFT) in gas and solution phases was developed to study the intermolecular interactions in the pre-polymerization mixture and to find the suitable functional monomers in MIP preparation. On the basis of computational results, o-phenylenediamine (OP), gallic acid (GA) and p-aminobenzoic acid (ABA) were selected as functional monomers. The MIP film was cast on glassy carbon electrode by electropolymerization of solution containing ternary monomers and then followed by Ag dendrites (AgDs) with nanobranch deposition. The surface feature of the modified electrode (AgDs/MIP/GCE) was characterized by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). Under the optimal experimental conditions, the peak current was proportional to the concentration of mesalamine ranging from 0.05 to 100 μM, with the detection limit of 0.015 μM. The proposed sensor was applied successfully for mesalamine determination in real samples. - Highlights: • The determination of MES using AgDs/MIP/GCE is reported for the first time. • The computer assisted design of terpolymer MIPs was used to screen monomers. • Theoretical results of DFT approach were in agreement with experimental results. • The sensor displayed a high selectivity for template in the presence of interferes. • The developed sensor has been applied to determine mesalamine in real samples.

  13. Electrochemical sensing of total antioxidant capacity and polyphenol content in wine samples using amperometry online-coupled with microdialysis.

    Science.gov (United States)

    Jakubec, Petr; Bancirova, Martina; Halouzka, Vladimir; Lojek, Antonin; Ciz, Milan; Denev, Petko; Cibicek, Norbert; Vacek, Jan; Vostalova, Jitka; Ulrichova, Jitka; Hrbac, Jan

    2012-08-15

    This work describes the method for total antioxidant capacity (TAC) and/or total content of phenolics (TCP) analysis in wines using microdialysis online-coupled with amperometric detection using a carbon microfiber working electrode. The system was tested on 10 selected wine samples, and the results were compared with total reactive antioxidant potential (TRAP), oxygen radical absorbance capacity (ORAC), and chemiluminescent determination of total antioxidant capacity (CL-TAC) methods using Trolox and catechin as standards. Microdialysis online-coupled with amperometric detection gives similar results to the widely used cyclic voltammetry methodology and closely correlates with ORAC and TRAP. The problem of electrode fouling is overcome by the introduction of an electrochemical cleaning step (1-2 min at the potential of 0 V vs Ag/AgCl). Such a procedure is sufficient to fully regenerate the electrode response for both red and white wine samples as well as catechin/Trolox standards. The appropriate size of microdialysis probes enables easy automation of the electrochemical TAC/TCP measurement using 96-well microtitration plates.

  14. Fabrication of an electrochemical sensor based on computationally designed molecularly imprinted polymer for the determination of mesalamine in real samples

    International Nuclear Information System (INIS)

    Torkashvand, M.; Gholivand, M.B.; Taherkhani, F.

    2015-01-01

    A novel electrochemical sensor based on mesalamine molecularly imprinted polymer (MIP) film on a glassy carbon electrode was fabricated. Density functional theory (DFT) in gas and solution phases was developed to study the intermolecular interactions in the pre-polymerization mixture and to find the suitable functional monomers in MIP preparation. On the basis of computational results, o-phenylenediamine (OP), gallic acid (GA) and p-aminobenzoic acid (ABA) were selected as functional monomers. The MIP film was cast on glassy carbon electrode by electropolymerization of solution containing ternary monomers and then followed by Ag dendrites (AgDs) with nanobranch deposition. The surface feature of the modified electrode (AgDs/MIP/GCE) was characterized by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). Under the optimal experimental conditions, the peak current was proportional to the concentration of mesalamine ranging from 0.05 to 100 μM, with the detection limit of 0.015 μM. The proposed sensor was applied successfully for mesalamine determination in real samples. - Highlights: • The determination of MES using AgDs/MIP/GCE is reported for the first time. • The computer assisted design of terpolymer MIPs was used to screen monomers. • Theoretical results of DFT approach were in agreement with experimental results. • The sensor displayed a high selectivity for template in the presence of interferes. • The developed sensor has been applied to determine mesalamine in real samples

  15. Ex vivo characterization of normal and adenocarcinoma colon samples by Mueller matrix polarimetry.

    Science.gov (United States)

    Ahmad, Iftikhar; Ahmad, Manzoor; Khan, Karim; Ashraf, Sumara; Ahmad, Shakil; Ikram, Masroor

    2015-05-01

    Mueller matrix polarimetry along with polar decomposition algorithm was employed for the characterization of ex vivo normal and adenocarcinoma human colon tissues by polarized light in the visible spectral range (425-725 nm). Six derived polarization metrics [total diattenuation (DT ), retardance (RT ), depolarization(ΔT ), linear diattenuation (DL), retardance (δ), and depolarization (ΔL)] were compared for normal and adenocarcinoma colon tissue samples. The results show that all six polarimetric properties for adenocarcinoma samples were significantly higher as compared to the normal samples for all wavelengths. The Wilcoxon rank sum test illustrated that total retardance is a good candidate for the discrimination of normal and adenocarcinoma colon samples. Support vector machine classification for normal and adenocarcinoma based on the four polarization properties spectra (ΔT , ΔL, RT ,and δ) yielded 100% accuracy, sensitivity, and specificity, while both DTa nd DL showed 66.6%, 33.3%, and 83.3% accuracy, sensitivity, and specificity, respectively. The combination of polarization analysis and given classification methods provides a framework to distinguish the normal and cancerous tissues.

  16. A Global Sampling Based Image Matting Using Non-Negative Matrix Factorization

    Directory of Open Access Journals (Sweden)

    NAVEED ALAM

    2017-10-01

    Full Text Available Image matting is a technique in which a foreground is separated from the background of a given image along with the pixel wise opacity. This foreground can then be seamlessly composited in a different background to obtain a novel scene. This paper presents a global non-parametric sampling algorithm over image patches and utilizes a dimension reduction technique known as NMF (Non-Negative Matrix Factorization. Although some existing non-parametric approaches use large nearby foreground and background regions to sample patches but these approaches fail to take the whole image to sample patches. It is because of the high memory and computational requirements. The use of NMF in the proposed algorithm allows the dimension reduction which reduces the computational cost and memory requirement. The use of NMF also allow the proposed approach to use the whole foreground and background region in the image and reduces the patch complexity and help in efficient patch sampling. The use of patches not only allows the incorporation of the pixel colour but also the local image structure. The use of local structures in the image is important to estimate a high-quality alpha matte especially in the images which have regions containing high texture. The proposed algorithm is evaluated on the standard data set and obtained results are comparable to the state-of-the-art matting techniques

  17. A global sampling based image matting using non-negative matrix factorization

    International Nuclear Information System (INIS)

    Alam, N.; Sarim, M.; Shaikh, A.B.

    2017-01-01

    Image matting is a technique in which a foreground is separated from the background of a given image along with the pixel wise opacity. This foreground can then be seamlessly composited in a different background to obtain a novel scene. This paper presents a global non-parametric sampling algorithm over image patches and utilizes a dimension reduction technique known as NMF (Non-Negative Matrix Factorization). Although some existing non-parametric approaches use large nearby foreground and background regions to sample patches but these approaches fail to take the whole image to sample patches. It is because of the high memory and computational requirements. The use of NMF in the proposed algorithm allows the dimension reduction which reduces the computational cost and memory requirement. The use of NMF also allow the proposed approach to use the whole foreground and background region in the image and reduces the patch complexity and help in efficient patch sampling. The use of patches not only allows the incorporation of the pixel colour but also the local image structure. The use of local structures in the image is important to estimate a high-quality alpha matte especially in the images which have regions containing high texture. The proposed algorithm is evaluated on the standard data set and obtained results are comparable to the state-of-the-art matting techniques. (author)

  18. Fabrication of an electrochemical nanoaptasensor based on AuNPs for ultrasensitive determination of cocaine in serum sample

    International Nuclear Information System (INIS)

    Roushani, Mahmoud; Shahdost-fard, Faezeh

    2016-01-01

    Herein we describe an ultrasensitive electrochemical nanoaptasensor for the detection of one of the most dangerous narcotic drugs available, cocaine. The nanoaptasensor was constructed by the covalent attachment of a 5′-NH 2 -3′-gold nanoparticles terminated aptamer on the surface of a glassy carbon electrode which was deposited with gold nanoparticles (AuNPs/GCE). It is worth noting that the interaction of the cysteamine stable self-assembled monolayer on the AuNPs/GCE surface and the covalent attachment of terephthalaldehyde via amide coupling with the amine groups in the cysteamine and aptamer, respectively, resulted in the covalent attachment of the aptamer to AuNPs/GCE. The presence of gold nanoparticles both on surface of the glassy carbon electrode and in the end of the aptamer, can provide advantages such as increase of active surface area, high acceleration of the electron transfer and improved electrochemical signal, respectively. The decrease in the peak current of [Fe(CN) 6 ] 3−/4− as the probe redox with increase of cocaine concentration, in differential pulse voltammetry as the measuring technique, from 5 pM up to 5 nM was linear and an unprecedented detection limit of 0.5 pM was yielded. Furthermore, the effect of some common analgesic drugs as the potential interferents were investigated and also, to evaluate practical application of the proposed nanoaptasensor human blood serum sample as a real sample was used. Simple preparation, low operation cost, speed and validity are the decisive factors of this method motivating its application to biosensing investigation. - Highlights: • An electrochemical nanoaptasensor for the detection of cocaine is presented. • An AuNPs terminated aptamer was covalent bonded on the surface of the AuNPs/GCE. • The presence of AuNPs has many advantages and improved electrochemical signal. • Two linear ranges from 5 pM up to 5 nM and an unprecedented LOD of 0.5 pM were yielded. • It will shed light on new

  19. Fabrication of an electrochemical nanoaptasensor based on AuNPs for ultrasensitive determination of cocaine in serum sample

    Energy Technology Data Exchange (ETDEWEB)

    Roushani, Mahmoud, E-mail: mahmoudroushani@yahoo.com; Shahdost-fard, Faezeh

    2016-04-01

    Herein we describe an ultrasensitive electrochemical nanoaptasensor for the detection of one of the most dangerous narcotic drugs available, cocaine. The nanoaptasensor was constructed by the covalent attachment of a 5′-NH{sub 2}-3′-gold nanoparticles terminated aptamer on the surface of a glassy carbon electrode which was deposited with gold nanoparticles (AuNPs/GCE). It is worth noting that the interaction of the cysteamine stable self-assembled monolayer on the AuNPs/GCE surface and the covalent attachment of terephthalaldehyde via amide coupling with the amine groups in the cysteamine and aptamer, respectively, resulted in the covalent attachment of the aptamer to AuNPs/GCE. The presence of gold nanoparticles both on surface of the glassy carbon electrode and in the end of the aptamer, can provide advantages such as increase of active surface area, high acceleration of the electron transfer and improved electrochemical signal, respectively. The decrease in the peak current of [Fe(CN){sub 6}]{sup 3−/4−} as the probe redox with increase of cocaine concentration, in differential pulse voltammetry as the measuring technique, from 5 pM up to 5 nM was linear and an unprecedented detection limit of 0.5 pM was yielded. Furthermore, the effect of some common analgesic drugs as the potential interferents were investigated and also, to evaluate practical application of the proposed nanoaptasensor human blood serum sample as a real sample was used. Simple preparation, low operation cost, speed and validity are the decisive factors of this method motivating its application to biosensing investigation. - Highlights: • An electrochemical nanoaptasensor for the detection of cocaine is presented. • An AuNPs terminated aptamer was covalent bonded on the surface of the AuNPs/GCE. • The presence of AuNPs has many advantages and improved electrochemical signal. • Two linear ranges from 5 pM up to 5 nM and an unprecedented LOD of 0.5 pM were yielded. • It will shed

  20. Integrated Circuits for Rapid Sample Processing and Electrochemical Detection of Biomarkers

    Science.gov (United States)

    Besant, Justin

    The trade-off between speed and sensitivity of detection is a fundamental challenge in the design of point-of-care diagnostics. As the relevant molecules in many diseases exist natively at extremely low levels, many gold-standard diagnostic tests are designed with high sensitivity at the expense of long incubations needed to amplify the target analytes. The central aim of this thesis is to design new strategies to detect biologically relevant analytes with both high speed and sensitivity. The response time of a biosensor is limited by the ability of the target analyte to accumulate to detectable levels at the sensor surface. We overcome this limitation by designing a range of integrated devices to optimize the flux of the analyte to the sensor by increasing the effective analyte concentration, shortening the required diffusion distance, and confining the analyte in close proximity to the sensor. We couple these devices with novel ultrasensitive electrochemical transduction strategies to convert rare analytes into a detectable signal. We showcase the clinical utility of these approaches with several applications including cancer diagnosis, bacterial identification, and antibiotic susceptibility profiling. We design and optimize a device to isolate rare cancer cells from the bloodstream with near 100% efficiency and 10 000-fold specificity. We analyse pathogen specific nucleic acids by lysing bacteria in close proximity to an electrochemical sensor and find that this approach has 10-fold higher sensitivity than standard lysis in bulk solution. We design an electronic chip to readout the antibiotic susceptibility profile with an hour-long incubation by concentrating bacteria into nanoliter chambers with integrated electrodes. Finally, we report a strategy for ultrasensitive visual readout of nucleic acids as low as 100 fM within 10 minutes using an amplification cascade. The strategies presented could guide the development of fast, sensitive and low-cost diagnostics

  1. Porous or roughened electrode with an assigned matrix for electrochemical cells with acid electrolytes, especially fuel cell batteries

    Energy Technology Data Exchange (ETDEWEB)

    Boehm, H; Fleischmann, R

    1975-10-16

    According to the invention an electrolyte matrix is to be used, which experiences a definite increase in volume by swelling, and fits on to the electrode in such a way that it is closely meshed with it. Matrix materials treated with sulphuric acid are claimed, such as 1) polystyrol, polyethelyne, polyvinyl alcohol, polyvinyl acetate, methyl cellulose or polyester, which are used alone or compounded with silica gel, aluminium oxide or sea sand, and 2) zeolite, silica, aluminium dioxide, titanium dioxide or zirconium dioxide using binding materials.

  2. Effects of microstructures on hydrogen induced cracking of electrochemically hydrogenated double notched tensile sample of 4340 steel

    Energy Technology Data Exchange (ETDEWEB)

    Sk, Mobbassar Hassan, E-mail: Skmobba@qu.edu.qa [Center for Advanced Materials, Qatar University, Doha (Qatar); Overfelt, Ruel A. [Materials Research and Education Center, Materials Engineer, Auburn University, Auburn, AL (United States); Abdullah, Aboubakr M. [Center for Advanced Materials, Qatar University, Doha (Qatar)

    2016-04-06

    Quantitative fractographic characteristics of 4340 steel is demonstrated for a grain size range of 10−100 µm and hardness range of 41–52 HRC. Double-notched tensile samples were electrochemically charged in-situ with hydrogen in 0.5 m H{sub 2}SO{sub 4}+5 mg/l As{sub 2}O{sub 3} solution for 0–40 min charging time. Hydrogen induced fracture initiations were analyzed by novel metallographic investigation of the “unbroken” notch while the overall fractographic behaviors were examined by the scanning electron microscopic imaging of the fracture surfaces of the actually broken notch. Effect of hydrogen was predominantly manifested as intergranular fracture for the harder samples and quasi-cleavage fracture for the softer counterparts. 10–40 µm samples showed the maximum intensity of the hydrogen induced fracture features (intergranular and/or quasi-cleavage) close to the notch which gradually reduced with increasing distance from the notch. The largest grained samples (100 µm) however showed brittle behavior even in absence of hydrogen with similar intensity of percent fracture features at all distance from the notch, while presence of hydrogen intensified the overall percent brittle fractures with their intensities being highest close to the notch. Finally, the brittle fracture characteristics of the hydrogen embrittled samples were shown to be distinguishably different from that of the liquid nitrogen treated samples of same grain sizes and hardnesses.

  3. Characterization of nanostructured CuO-porous silicon matrix formed on copper-coated silicon substrate via electrochemical etching

    Science.gov (United States)

    Naddaf, M.; Mrad, O.; Al-zier, A.

    2014-06-01

    A pulsed anodic etching method has been utilized for nanostructuring of a copper-coated p-type (100) silicon substrate, using HF-based solution as electrolyte. Scanning electron microscopy reveals the formation of a nanostructured matrix that consists of island-like textures with nanosize grains grown onto fiber-like columnar structures separated with etch pits of grooved porous structures. Spatial micro-Raman scattering analysis indicates that the island-like texture is composed of single-phase cupric oxide (CuO) nanocrystals, while the grooved porous structure is barely related to formation of porous silicon (PS). X-ray diffraction shows that both the grown CuO nanostructures and the etched silicon layer have the same preferred (220) orientation. Chemical composition obtained by means of X-ray photoelectron spectroscopic (XPS) analysis confirms the presence of the single-phase CuO on the surface of the patterned CuO-PS matrix. As compared to PS formed on the bare silicon substrate, the room-temperature photoluminescence (PL) from the CuO-PS matrix exhibits an additional weak `blue' PL band as well as a blue shift in the PL band of PS (S-band). This has been revealed from XPS analysis to be associated with the enhancement in the SiO2 content as well as formation of the carbonyl group on the surface in the case of the CuO-PS matrix.

  4. Intermittent Contact Alternating Current Scanning Electrochemical Microscopy: A Method for Mapping Conductivities in Solid Li Ion Conducting Electrolyte Samples

    Energy Technology Data Exchange (ETDEWEB)

    Catarelli, Samantha Raisa; Lonsdale, Daniel [Uniscan Instruments Ltd., Macclesfield (United Kingdom); Cheng, Lei [Energy Storage and Distribution Resources Division, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Materials Sciences and Engineering Department, University of California Berkeley, Berkeley, CA (United States); Syzdek, Jaroslaw [Bio-Logic USA LLC, Knoxville, TN (United States); Doeff, Marca, E-mail: mmdoeff@lbl.gov [Energy Storage and Distribution Resources Division, Lawrence Berkeley National Laboratory, Berkeley, CA (United States)

    2016-03-31

    Intermittent contact alternating current scanning electrochemical microscopy (ic-ac-SECM) has been used to determine the electrochemical response to an ac signal of several types of materials. A conductive gold foil and insulating Teflon sheet were first used to demonstrate that the intermittent contact function allows the topography and conductivity to be mapped simultaneously and independently in a single experiment. Then, a dense pellet of an electronically insulating but Li ion conducting garnet phase, Al-substituted Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12} (LLZO), was characterized using the same technique. The polycrystalline pellet was prepared by classical ceramic sintering techniques and was comprised of large (~150 μm) grains. Critical information regarding the contributions of grain and grain boundary resistances to the total conductivity of the garnet phase was lacking due to ambiguities in the impedance data. In contrast, the use of the ic-ac-SECM technique allowed spatially resolved information regarding local conductivities to be measured directly. Impedance mapping of the pellet showed that the grain boundary resistance, while generally higher than that of grains, varied considerably, revealing the complex nature of the LLZO sample.

  5. Electrochemical Study of Carbon Nanotubes/Nanohybrids for Determination of Metal Species Cu2+ and Pb2+ in Water Samples

    Directory of Open Access Journals (Sweden)

    Andréa Claudia Oliveira Silva

    2016-01-01

    Full Text Available The use of nanomaterials, such as nanoparticles and nanotubes, for electrochemical detection of metal species has been investigated as a way of modifying electrodes by electrochemical stripping analysis. The present study develops a new methodology based on a comparative study of nanoparticles and nanotubes with differential pulse anodic stripping voltammetry (DPASV and examines the simultaneous determination of copper and lead. The glassy carbon electrode modified by gold nanoparticles demonstrated increased sensitivity and decreased detection limits, among other improvements in analytical performance data. Under optimized conditions (deposition potential −0.8 V versus Ag/AgCl; deposition time, 300 s; resting time, 10 s; pulse amplitude, 50 mV; and voltage step height, 4 mV, the detection limits were 0.2279 and 0.3321 ppb, respectively, for determination of Pb2+ and Cu2+. The effects of cations and anions on the simultaneous determination of metal ions do not exhibit significant interference, thereby demonstrating the selectivity of the electrode for simultaneous determination of Pb2+ and Cu2+. The same method was also used to determine Cu2+ in water samples.

  6. Electrochemical determination of serotonin in urine samples based on metal oxide nanoparticles/MWCNT on modified glassy carbon electrode

    Directory of Open Access Journals (Sweden)

    Omolola E. Fayemi

    2017-04-01

    Full Text Available The electrochemical response of serotonin on the modified electrode based on multiwalled-carbon-nanotube (MWCNT doped respectively with nickel, zinc and iron oxide nanoparticles coating on glassy carbon electrode (GCE at physiological pH 7 was determined using cyclic voltammetry (CV and square wave voltammetry (SWV. The modified GCE/MWCNT-metal oxide electrodes exhibited excellent electrocatalytic activity towards the detection of serotonin at large peak current and lower oxidation potentials compared to other electrodes investigated. The dynamic range for the serotonin determination was between 5.98 × 10−3 μM to 62.8 μM with detection limits 118, 129 and 166 nM for GCE/MWCNT-NiO, GCE/MWCNT-ZnO and GCE/MWCNT-Fe3O4 sensors respectively. GCE-MWCNT-NiO was the best electrode in terms of serotonin current response, electrode stability, resistance to fouling and limit of detection towards the analyte. The developed sensors were found to be electrochemically stable, reusable, economically effective due to their extremely low operational cost, and have demonstrated good limit of detection, sensitivity and selectivity towards serotonin determination in urine samples. Keywords: Metal oxides nanoparticles, Multiwalled carbon nanotubes, Glassy carbon electrode, Serotonin, Cyclic voltammetry, Square wave voltammetry

  7. Characterization of a stream sediment matrix material for sampling behavior in order to use it as a CRM

    International Nuclear Information System (INIS)

    Huang Donghui; Xiao Caijin; Ni Bangfa; Tian Weizhi; Zhang Yuanxun; Wang Pingsheng; Liu Cunxiong; Zhang Guiying

    2010-01-01

    Sampling behavior of multielements in a stream sediment matrix was studied with sample sizes in a range of 9 orders of magnitude by a combination of INAA, PIXE and SR-XRF. For accurately weighable sample sizes (>1 mg), sampling uncertainties for 16 elements are better than 1% by INAA. For sample sizes that cannot be accurately weighed (<1 mg), PIXE and SR-XRF were used and the effective sample sizes were estimated. Sampling uncertainties for seven elements are better than 1% at sample sizes of tenth mg level, and that for three elements are better than 10% on ng levels.

  8. The augmented lagrange multipliers method for matrix completion from corrupted samplings with application to mixed Gaussian-impulse noise removal.

    Directory of Open Access Journals (Sweden)

    Fan Meng

    Full Text Available This paper studies the problem of the restoration of images corrupted by mixed Gaussian-impulse noise. In recent years, low-rank matrix reconstruction has become a research hotspot in many scientific and engineering domains such as machine learning, image processing, computer vision and bioinformatics, which mainly involves the problem of matrix completion and robust principal component analysis, namely recovering a low-rank matrix from an incomplete but accurate sampling subset of its entries and from an observed data matrix with an unknown fraction of its entries being arbitrarily corrupted, respectively. Inspired by these ideas, we consider the problem of recovering a low-rank matrix from an incomplete sampling subset of its entries with an unknown fraction of the samplings contaminated by arbitrary errors, which is defined as the problem of matrix completion from corrupted samplings and modeled as a convex optimization problem that minimizes a combination of the nuclear norm and the l(1-norm in this paper. Meanwhile, we put forward a novel and effective algorithm called augmented Lagrange multipliers to exactly solve the problem. For mixed Gaussian-impulse noise removal, we regard it as the problem of matrix completion from corrupted samplings, and restore the noisy image following an impulse-detecting procedure. Compared with some existing methods for mixed noise removal, the recovery quality performance of our method is dominant if images possess low-rank features such as geometrically regular textures and similar structured contents; especially when the density of impulse noise is relatively high and the variance of Gaussian noise is small, our method can outperform the traditional methods significantly not only in the simultaneous removal of Gaussian noise and impulse noise, and the restoration ability for a low-rank image matrix, but also in the preservation of textures and details in the image.

  9. A novel variable selection approach that iteratively optimizes variable space using weighted binary matrix sampling.

    Science.gov (United States)

    Deng, Bai-chuan; Yun, Yong-huan; Liang, Yi-zeng; Yi, Lun-zhao

    2014-10-07

    In this study, a new optimization algorithm called the Variable Iterative Space Shrinkage Approach (VISSA) that is based on the idea of model population analysis (MPA) is proposed for variable selection. Unlike most of the existing optimization methods for variable selection, VISSA statistically evaluates the performance of variable space in each step of optimization. Weighted binary matrix sampling (WBMS) is proposed to generate sub-models that span the variable subspace. Two rules are highlighted during the optimization procedure. First, the variable space shrinks in each step. Second, the new variable space outperforms the previous one. The second rule, which is rarely satisfied in most of the existing methods, is the core of the VISSA strategy. Compared with some promising variable selection methods such as competitive adaptive reweighted sampling (CARS), Monte Carlo uninformative variable elimination (MCUVE) and iteratively retaining informative variables (IRIV), VISSA showed better prediction ability for the calibration of NIR data. In addition, VISSA is user-friendly; only a few insensitive parameters are needed, and the program terminates automatically without any additional conditions. The Matlab codes for implementing VISSA are freely available on the website: https://sourceforge.net/projects/multivariateanalysis/files/VISSA/.

  10. Source apportionment and location by selective wind sampling and Positive Matrix Factorization.

    Science.gov (United States)

    Venturini, Elisa; Vassura, Ivano; Raffo, Simona; Ferroni, Laura; Bernardi, Elena; Passarini, Fabrizio

    2014-10-01

    In order to determine the pollution sources in a suburban area and identify the main direction of their origin, PM2.5 was collected with samplers coupled with a wind select sensor and then subjected to Positive Matrix Factorization (PMF) analysis. In each sample, soluble ions, organic carbon, elemental carbon, levoglucosan, metals, and Polycyclic Aromatic Hydrocarbons (PAHs) were determined. PMF results identified six main sources affecting the area: natural gas home appliances, motor vehicles, regional transport, biomass combustion, manufacturing activities, and secondary aerosol. The connection of factor temporal trends with other parameters (i.e., temperature, PM2.5 concentration, and photochemical processes) confirms factor attributions. PMF analysis indicated that the main source of PM2.5 in the area is secondary aerosol. This should be mainly due to regional contributions, owing to both the secondary nature of the source itself and the higher concentration registered in inland air masses. The motor vehicle emission source contribution is also important. This source likely has a prevalent local origin. The most toxic determined components, i.e., PAHs, Cd, Pb, and Ni, are mainly due to vehicular traffic. Even if this is not the main source in the study area, it is the one of greatest concern. The application of PMF analysis to PM2.5 collected with this new sampling technique made it possible to obtain more detailed results on the sources affecting the area compared to a classical PMF analysis.

  11. Determination of temperature dependence of full matrix material constants of PZT-8 piezoceramics using only one sample.

    Science.gov (United States)

    Zhang, Yang; Tang, Liguo; Tian, Hua; Wang, Jiyang; Cao, Wenwu; Zhang, Zhongwu

    2017-08-15

    Resonant ultrasound spectroscopy (RUS) was used to determine the temperature dependence of full matrix material constants of PZT-8 piezoceramics from room temperature to 100 °C. Property variations from sample to samples can be eliminated by using only one sample, so that data self-consistency can be guaranteed. The RUS measurement system error was estimated to be lower than 2.35%. The obtained full matrix material constants at different temperatures all have excellent self-consistency, which can help accurately predict device performance at high temperatures using finite element simulations.

  12. Overcoming Matrix Effects in a Complex Sample: Analysis of Multiple Elements in Multivitamins by Atomic Absorption Spectroscopy

    Science.gov (United States)

    Arnold, Randy J.; Arndt, Brett; Blaser, Emilia; Blosser, Chris; Caulton, Dana; Chung, Won Sog; Fiorenza, Garrett; Heath, Wyatt; Jacobs, Alex; Kahng, Eunice; Koh, Eun; Le, Thao; Mandla, Kyle; McCory, Chelsey; Newman, Laura; Pithadia, Amit; Reckelhoff, Anna; Rheinhardt, Joseph; Skljarevski, Sonja; Stuart, Jordyn; Taylor, Cassie; Thomas, Scott; Tse, Kyle; Wall, Rachel; Warkentien, Chad

    2011-01-01

    A multivitamin tablet and liquid are analyzed for the elements calcium, magnesium, iron, zinc, copper, and manganese using atomic absorption spectrometry. Linear calibration and standard addition are used for all elements except calcium, allowing for an estimate of the matrix effects encountered for this complex sample. Sample preparation using…

  13. Electrochemical monitoring of malondialdehyde biomarker in biological samples via electropolymerized amino acid/chitosan nanocomposite.

    Science.gov (United States)

    Hasanzadeh, Mohammad; Mokhtari, Fozieh; Jouyban-Gharamaleki, Vahid; Mokhtarzadeh, Ahad; Shadjou, Nasrin

    2018-04-15

    This study reports on the electropolymerization of a low toxic and biocompatible nanopolymer with entitle poly arginine-graphene quantum dots-chitosan (PARG-GQDs-CS) as a novel strategy for surface modification of glassy carbon surface and preparation of a new interface for measurement of malondialdehyde (MDA) in exhaled breath condensate. Electrochemical deposition, as a well-controlled synthesis procedure, has been used for subsequently layer-by-layer preparation of GQDs-CS nanostructures on a PARG prepolymerized on the surface of glassy carbon electrode using cyclic voltammetry techniques in the regime of -1.5 to 2 V. The modified electrode appeared as an effective electroactivity for detection of MDA by using cyclic voltammetry, linear sweep voltammetry, and differential pulse voltammetry. The prepared modified electrode demonstrated a noticeably good activity for electrooxidation of MDA than PARG. Enhancement of peak currents is ascribed to the fast heterogeneous electron transfer kinetics that arise from the synergistic coupling between the excellent properties of PARG and semiconducting polymer, GQDs as high density of edge plane sites and subtle electronic characteristics and unique properties of CS such as excellent film-forming ability, high permeability, good adhesion, nontoxicity, cheapness, and a susceptibility to chemical modification. The prepared sensor showed 1 oxidation processes for MDA at potentials about 1 V with a low limit of quantification 5.94 nM. Finally, application of new sensor for determination of MDA in exhaled breath condensate was suited. In general, the simultaneous attachment of GQDs and CS to structure of poly amino acids provides new opportunities within the personal healthcare. Copyright © 2018 John Wiley & Sons, Ltd.

  14. Sample preparation technique for transmission electron microscopy anodized Al-Li-SiC metal matrix composite

    International Nuclear Information System (INIS)

    Shahid, M.; Thomson, G.E.

    1997-01-01

    Along with improved mechanical properties, metal matrix composites (MMC) have a disadvantage of enhanced corrosion susceptibility in aggressive environments. Recent studies on corrosion behaviour of an Al-alloy 8090/SiC MMC, revealed considerably high corrosion rates of the MMC in near neutral solutions containing chloride ions. Anodizing is one of the potential surface treatment for the MMC to provide protective coating against corrosion. The surface and cross section of the anodized MMC can easily be observed using scanning electron microscope. The anodizing behaviour of the MMC can be understood further if the anodized cross section in examined under transmission electron microscope (TEM). However, it is relatively difficult to prepare small (3 mm diameter) electron transparent specimens of the MMC supporting an anodic film. In the present study a technique has been developed for preparing thin electron transparent specimens of the anodized MMC. This technique employed conventional ion beam thinning process but the preparation of small discs was a problem. A MMMC consisting of Al-alloy 8090 with 20 % (by weight) SiC particulate with an average size of 5 Mu m, was anodized and observed in TEM after preparing the samples using the above mentioned techniques. (author)

  15. Preparation of milk samples for immunoassay and liquid chromatographic screening using matrix solid-phase dispersion.

    Science.gov (United States)

    Barker, S A; Long, A R

    1994-01-01

    The use of drugs to maintain the health and maximize the output of dairy cattle has made the monitoring of milk for such agents essential. Screening tests based on immunological, microbial inhibition, and bacterial receptor assays have been developed for the detection of violative levels of therapeutic substances. However, such assays are not infallible, and false positive or negative results can occur when contaminants bind receptors or compete for the binding of the target residues. Such effects may arise from dietary sources, diseases, or other variables. Thus, a violation by such a test is not definitive until further confirmation is obtained. Our laboratory has developed extraction procedures for several drugs used in dairy production. Our method uses matrix solid-phase dispersion (MSPD) to isolate drugs away from contaminants and to eliminate many possible interferences. MSPD can also be used to enhance the specificity of such assays by fractionating various classes of drugs that may cross-react. Similarly, such methods may be used for liquid chromatographic screening and confirmation of a suspect sample.

  16. Matrix-assisted laser desorption/ionization sample preparation optimization for structural characterization of poly(styrene-co-pentafluorostyrene) copolymers

    International Nuclear Information System (INIS)

    Tisdale, Evgenia; Kennedy, Devin; Wilkins, Charles

    2014-01-01

    Graphical abstract: -- Highlights: •We optimized sample preparation for MALDI TOF poly(styrene-copentafluorostyrene) co-polymers. •Influence of matrix choice was investigated. •Influence of matrix/analyte ratio was examined. •Influence of analyte/salt ratio (for Ag+ salt) was studied. -- Abstract: The influence of the sample preparation parameters (the choice of the matrix, matrix:analyte ratio, salt:analyte ratio) was investigated and optimal conditions were established for the MALDI time-of-flight mass spectrometry analysis of the poly(styrene-co-pentafluorostyrene) copolymers. These were synthesized by atom transfer radical polymerization. Use of 2,5-dihydroxybenzoic acid as matrix resulted in spectra with consistently high ion yields for all matrix:analyte:salt ratios tested. The optimized MALDI procedure was successfully applied to the characterization of three copolymers obtained by varying the conditions of polymerization reaction. It was possible to establish the nature of the end groups, calculate molecular weight distributions, and determine the individual length distributions for styrene and pentafluorostyrene monomers, contained in the resulting copolymers. Based on the data obtained, it was concluded that individual styrene chain length distributions are more sensitive to the change in the composition of the catalyst (the addition of small amount of CuBr 2 ) than is the pentafluorostyrene component distribution

  17. Matrix-assisted laser desorption/ionization sample preparation optimization for structural characterization of poly(styrene-co-pentafluorostyrene) copolymers

    Energy Technology Data Exchange (ETDEWEB)

    Tisdale, Evgenia; Kennedy, Devin; Wilkins, Charles, E-mail: cwilkins@uark.edu

    2014-01-15

    Graphical abstract: -- Highlights: •We optimized sample preparation for MALDI TOF poly(styrene-copentafluorostyrene) co-polymers. •Influence of matrix choice was investigated. •Influence of matrix/analyte ratio was examined. •Influence of analyte/salt ratio (for Ag+ salt) was studied. -- Abstract: The influence of the sample preparation parameters (the choice of the matrix, matrix:analyte ratio, salt:analyte ratio) was investigated and optimal conditions were established for the MALDI time-of-flight mass spectrometry analysis of the poly(styrene-co-pentafluorostyrene) copolymers. These were synthesized by atom transfer radical polymerization. Use of 2,5-dihydroxybenzoic acid as matrix resulted in spectra with consistently high ion yields for all matrix:analyte:salt ratios tested. The optimized MALDI procedure was successfully applied to the characterization of three copolymers obtained by varying the conditions of polymerization reaction. It was possible to establish the nature of the end groups, calculate molecular weight distributions, and determine the individual length distributions for styrene and pentafluorostyrene monomers, contained in the resulting copolymers. Based on the data obtained, it was concluded that individual styrene chain length distributions are more sensitive to the change in the composition of the catalyst (the addition of small amount of CuBr{sub 2}) than is the pentafluorostyrene component distribution.

  18. Electrochemical Determination of Caffeine Content in Ethiopian Coffee Samples Using Lignin Modified Glassy Carbon Electrode

    Directory of Open Access Journals (Sweden)

    Meareg Amare

    2017-01-01

    Full Text Available Lignin film was deposited at the surface of glassy carbon electrode potentiostatically. In contrast to the unmodified glassy carbon electrode, an oxidative peak with an improved current and overpotential for caffeine at modified electrode showed catalytic activity of the modifier towards oxidation of caffeine. Linear dependence of peak current on caffeine concentration in the range 6×10-6 to 100×10-6 mol L−1 with determination coefficient and method detection limit (LoD = 3 s/slope of 0.99925 and 8.37×10-7 mol L−1, respectively, supplemented by recovery results of 93.79–102.17% validated the developed method. An attempt was made to determine the caffeine content of aqueous coffee extracts of Ethiopian coffees grown in four coffee cultivating localities (Wonbera, Wolega, Finoteselam, and Zegie and hence to evaluate the correlation between users preference and caffeine content. In agreement with reported works, caffeine contents (w/w% of 0.164 in Wonbera coffee; 0.134 in Wolega coffee; 0.097 in Finoteselam coffee; and 0.089 in Zegie coffee were detected confirming the applicability of the developed method for determination of caffeine in a complex matrix environment. The result indicated that users’ highest preference for Wonbera and least preference for Zegie cultivated coffees are in agreement with the caffeine content.

  19. Electrochemical Determination of Caffeine Content in Ethiopian Coffee Samples Using Lignin Modified Glassy Carbon Electrode.

    Science.gov (United States)

    Amare, Meareg; Aklog, Senait

    2017-01-01

    Lignin film was deposited at the surface of glassy carbon electrode potentiostatically. In contrast to the unmodified glassy carbon electrode, an oxidative peak with an improved current and overpotential for caffeine at modified electrode showed catalytic activity of the modifier towards oxidation of caffeine. Linear dependence of peak current on caffeine concentration in the range 6 × 10 -6 to 100 × 10 -6  mol L -1 with determination coefficient and method detection limit (LoD = 3 s/slope) of 0.99925 and 8.37 × 10 -7  mol L -1 , respectively, supplemented by recovery results of 93.79-102.17% validated the developed method. An attempt was made to determine the caffeine content of aqueous coffee extracts of Ethiopian coffees grown in four coffee cultivating localities (Wonbera, Wolega, Finoteselam, and Zegie) and hence to evaluate the correlation between users preference and caffeine content. In agreement with reported works, caffeine contents (w/w%) of 0.164 in Wonbera coffee; 0.134 in Wolega coffee; 0.097 in Finoteselam coffee; and 0.089 in Zegie coffee were detected confirming the applicability of the developed method for determination of caffeine in a complex matrix environment. The result indicated that users' highest preference for Wonbera and least preference for Zegie cultivated coffees are in agreement with the caffeine content.

  20. Sensitive Electrochemical Determination of Gallic Acid: Application in Estimation of Total Polyphenols in Plant Samples

    Directory of Open Access Journals (Sweden)

    Mohammad Ali Sheikh-Mohseni

    2016-12-01

    Full Text Available A modified electrode was prepared by modification of the carbon paste electrode (CPE with graphene nano-sheets. The fabricated modified electrode exhibited an electrocatalytic activity toward gallic acid (GA oxidation because of good conductivity, low electron transfer resistance and catalytic effect. The graphene modified CPE had a lower overvoltage and enhanced electrical current respect to the bare CPE for the oxidation of GA. The oxidation potential of GA decreased more than 210 mV by the modified electrode. The modified electrode responded to the GA in the concentration range of 3.0 × 10-5-1.5 × 10-4 M with high sensitivity by the technique of differential pulse voltammetry. Also, detection limit of 1.1 × 10-7 M was obtained by this modified electrode for GA. This electrode was used for the successful determination of GA in plant samples. Therefore, the content of total polyphenols in plant samples can be determined by the proposed modified electrode based on the concentration of GA in the sample.

  1. Electrochemical studies on stress corrosion cracking of incoloy-800 in caustic solution. Part II: Precracking samples

    Directory of Open Access Journals (Sweden)

    Dinu Alice

    2006-01-01

    Full Text Available Stress corrosion cracking (SCC in a caustic medium may affect the secondary circuit tubing of a CANDU NPP cooled with river water, due to an accidental formation of a concentrated alkaline environment in the areas with restricted circulation, as a result of a leakage of cooling water from the condenser. To evaluate the susceptibility of Incoloy-800 (used to manufacture steam generator tubes for CANDU NPP to SCC, some accelerated corrosion tests were conducted in an alkaline solution (10% NaOH, pH = 13. These experiments were performed at ambient temperature and 85 °C. We used the potentiodynamic method and the potentiostatic method, simultaneously monitoring the variation of the open circuit potential during a time period (E corr/time curve. The C-ring method was used to stress the samples. In order to create stress concentrations, mechanical precracks with a depth of 100 or 250 μm were made on the outer side of the C-rings. Experimental results showed that the stressed samples were more susceptible to SCC than the unstressed samples whereas the increase in temperature and crack depth lead to an increase in SCC susceptibility. Incipient micro cracks of a depth of 30 μm were detected in the area of the highest peak of the mechanical precrack.

  2. eSensor: an electrochemical detection-based DNA microarray technology enabling sample-to-answer molecular diagnostics

    Science.gov (United States)

    Liu, Robin H.; Longiaru, Mathew

    2009-05-01

    DNA microarrays are becoming a widespread tool used in life science and drug screening due to its many benefits of miniaturization and integration. Microarrays permit a highly multiplexed DNA analysis. Recently, the development of new detection methods and simplified methodologies has rapidly expanded the use of microarray technologies from predominantly gene expression analysis into the arena of diagnostics. Osmetech's eSensor® is an electrochemical detection platform based on a low-to- medium density DNA hybridization array on a cost-effective printed circuit board substrate. eSensor® has been cleared by FDA for Warfarin sensitivity test and Cystic Fibrosis Carrier Detection. Other genetic-based diagnostic and infectious disease detection tests are under development. The eSensor® platform eliminates the need for an expensive laser-based optical system and fluorescent reagents. It allows one to perform hybridization and detection in a single and small instrument without any fluidic processing and handling. Furthermore, the eSensor® platform is readily adaptable to on-chip sample-to-answer genetic analyses using microfluidics technology. The eSensor® platform provides a cost-effective solution to direct sample-to-answer genetic analysis, and thus have a potential impact in the fields of point-of-care genetic analysis, environmental testing, and biological warfare agent detection.

  3. Device for electrochemical detection of metal sample surface resistance and passivation against corrosion in electrolyte

    International Nuclear Information System (INIS)

    Urbancik, L.; Bar, J.; Nemec, J.; Sima, A.

    1986-01-01

    The device consists of a teflon vessel with sealing and an opening below the electrolyte level. Into it is submerged an electrode connected to a dc voltage supply whose other pole is connected to a sample of the metal which is pressed to the opening in the sealing with a flexible strap. The teflon vessel and the sealing are integral. The device is simpler and less costly than those manufactured so far. The operating capability of damaged sealing may be renewed by simple mechanical working. The device may be used for detecting the resistance and passivation of steam generator metal tubes. (J.B.). 1 fig

  4. Electrochemical detection of a powerful estrogenic endocrine disruptor: ethinylestradiol in water samples through bioseparation procedure.

    Science.gov (United States)

    Martínez, Noelia A; Pereira, Sirley V; Bertolino, Franco A; Schneider, Rudolf J; Messina, Germán A; Raba, Julio

    2012-04-20

    The synthetic estrogen ethinylestradiol (EE2) is an active component of oral contraceptives (OCs), considered as an endocrine disrupting compound (EDC). It is excreted from humans and released via sewage treatment plant effluents into aquatic environments. EDCs are any environmental pollutant chemical that, once incorporated into an organism, affects the hormonal balance of various species including humans. Its presence in the environment is becoming of great importance in water quality. This paper describes the development of an accurate, sensitive and selective method for capture, preconcentration and determination of EE2 present in water samples using: magnetic particles (MPs) as bioaffinity support for the capture and preconcentration of EE2 and a glassy carbon electrode modified with multi-walled carbon nanotubes (MWCNTs/GCE) as detection system. The capture procedure was based on the principle of immunoaffinity, the EE2 being extracted from the sample using the anti-EE2 antibodies (anti-EE2 Ab) which were previously immobilized on MPs. Subsequently the analyte desorption was done employing a sulfuric acid solution and the determination of the EE2 in the pre-concentrated solution was carried out by square wave voltammetry (SWV). This method can be used to determine EE2 in the range of 0.035-70 ng L(-1) with a detection limit (LOD) of 0.01 ng L(-1) and R.S.D.levels. Copyright © 2012 Elsevier B.V. All rights reserved.

  5. First Electrochemical Method of Nitrothal-Isopropyl Determination in Water Samples

    Directory of Open Access Journals (Sweden)

    Dariusz Guziejewski

    2016-01-01

    Full Text Available The aim of the research was the use of square wave adsorptive stripping voltammetry (SWAdSV in conjunction with a hanging mercury drop electrode (HMDE for the determination of nitrothal-isopropyl. It was found that optimal SW technique parameters were frequency, 200 Hz; amplitude, 50 mV; and step potential, 5 mV. Accumulation time and potential were studied to select the optimal conditions in adsorptive stripping voltammetry: 45 s at 0.0 V, respectively. The calibration curve (SWSV was linear in the nitrothal-isopropyl concentration range from 2.0 × 10−7 to 2.0 × 10−6 mol L−1 with detection limit of 3.46 × 10−8 mol L−1. The repeatability of the method was determined at a nitrothal-isopropyl concentration level equal to 6.0 × 10−7 mol L−1 and expressed as RSD = 5.5% (n=6. The proposed method was successfully validated by studying the recovery of nitrothal-isopropyl in spiked environmental samples.

  6. Fabrication of a novel electrochemical sensor for determination of hydrogen peroxide in different fruit juice samples

    Directory of Open Access Journals (Sweden)

    Navid Nasirizadeh

    2016-01-01

    Full Text Available A new hydrogen peroxide (H2O2 sensor is fabricated based on a multiwalled carbon nanotube-modified glassy carbon electrode (MWCNT-GCE and reactive blue 19 (RB. The charge transfer coefficient, α, and the charge transfer rate constant, ks, of RB adsorbed on MWCNT-GCE were calculated and found to be 0.44 ± 0.01 Hz and 1.9 ± 0.05 Hz, respectively. The catalysis of the electroreduction of H2O2 by RB-MWCNT-GCE is described. The RB-MWCNT-GCE shows a dramatic increase in the peak current and a decrease in the overvoltage of H2O2 electroreduction in comparison with that seen at an RB modified GCE, MWCNT modified GCE, and activated GCE. The kinetic parameters such as α and the heterogeneous rate constant, k', for the reduction of H2O2 at RB-MWCNT-GCE surface were determined using cyclic voltammetry. The detection limit of 0.27μM and three linear calibration ranges were obtained for H2O2 determination at the RB-MWCNT-GCE surface using an amperometry method. In addition, using the newly developed sensor, H2O2 was determined in real samples with satisfactory results.

  7. The influence of pyrolysis and matrix modifiers on determination of Cr and Pb in sediment samples by GFAAS

    Directory of Open Access Journals (Sweden)

    Risfidian Mohadi

    2016-04-01

    Full Text Available Abstract: The Influence of pyrolysis and matrix modifiers on determination of Cr and Pb in sediment samples using graphite furnace atomic absorption spectrometry has been investigated. The sediment samples including three certified reference materials (CRMs are reported. Analyses were performed using microwave assisted dissolution. The matrix modifiers Mg(NO32, Pd+Mg(NO32 and NH4H2PO4were shown to be optimazed. The recovery for Cr and Pb in CRMs in the case of sample dissolution was found to be between 81 to 91% for Cr and 94 to 98% for Pb of the certified values, respectively. Keywords: Sediment, Pyrolysis, Matrix modifiers, Cr, Pb Abstrak (Indonesia: Pengaruh pirolisis dan matriks pengubah pada penentuan Cr dan Pb dalam sampel sedimen menggunakan tungku grafit spektroskopi serapan atom telah diteliti. Sampel sedimen termasuk tiga bahan referensi bersertifikat (CRMs dilaporkan dianalisis dengan menggunakan bantuan microwave ekstraktor. Matriks pengubah Mg(NO32, Pd+Mg(NO32 dan NH4H2PO4 telah digunakan dan menghasilkan nilai temu balik untuk Cr dan Pb dalam CRMs ditemukan antara 81-91% untuk Cr dan 94-98 % untuk Pb dari nilai sertifikat masing-masing. Katakunci: Sedimen, Pirolisis, Matrix modifiers, Cr, Pb

  8. Determination of antimony by electrochemical hydride generation atomic absorption spectrometry in samples with high iron content using chelating resins as on-line removal system

    International Nuclear Information System (INIS)

    Bolea, E.; Arroyo, D.; Laborda, F.; Castillo, J.R.

    2006-01-01

    A method for the removal of the interference caused by iron on electrochemical generation of stibine is proposed. It consists of a chelating resin Chelex 100 column integrated into a flow injection system and coupled to the electrochemical hydride generator quartz tube atomic absorption spectrometer (EcHG-QT-AAS). Iron, as Fe(II), is retained in the column with high efficiency, close to 99.9% under optimal conditions. No significant retention was observed for Sb(III) under same conditions and a 97 ± 5% signal recovery was achieved. An electrochemical hydride generator with a concentric configuration and a reticulated vitreous carbon cathode was employed. The system is able to determine antimony concentrations in the range of ng ml -1 in presence of iron concentrations up to 400 mg l -1 . The procedure was validated by analyzing PACS-2 marine sediments reference material with a 4% (w/w) iron content and a [Fe]:[Sb] ratio of 4000:1, which caused total antimony signal suppression on the electrochemical hydride generation system. A compost sample with high iron content (0.7%, w/w), was also analyzed. A good agreement was found on both samples with the certified value and the antimony concentration determined by ICP-MS, respectively

  9. Electrochemical mechanism of eugenol at a Cu doped gold nanoparticles modified glassy carbon electrode and its analytical application in food samples

    International Nuclear Information System (INIS)

    Lin, Xiaoyun; Ni, Yongnian; Kokot, Serge

    2014-01-01

    Graphical abstract: A simple one-step electrodeposition method was used to fabricate a Cu doped gold nanoparticles modified glassy carbon electrode. An electrochemical reaction mechanism for o-methoxy phenols was suggested. In addition, the above Cu@AuNPs/GCE was successfully employed for the analysis of eugenol in food samples. - Highlights: • One-step construction of the Cu@AuNPs/GCE electrode. • The modified electrode showed high sensitivity for the analysis of eugenol. • Electrochemical mechanism of eugenol by use of Cu@AuNPs/GCE was inferred. • The novel method was successfully employed for analysis of eugenol in food samples. - Abstract: A simple one-step electrodeposition method was used to construct a glassy carbon electrode (GCE), which has been modified with Cu doped gold nanoparticles (GNPs), i.e. a Cu@AuNPs/GCE. This electrode was characterized with the use of scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The eugenol was electrocatalytically oxidized at the Cu@AuNPs/GCE. At this electrode, in comparison with the behavior at the GCE alone, the corresponding oxidation peak current was enhanced and the shift of the oxidation potentials to lower values was observed. Electrochemical behavior of eugenol at the Cu@AuNPs/GCE was investigated with the use of the cyclic voltammetry (CV) technique, and additionally, in order to confirm the electrochemical reaction mechanism for o-methoxy phenols, CVs for catechol, guaiacol and vanillin were investigated consecutively. Based on this work, an electrochemical reaction mechanism for o-methoxy phenols was suggested, and in addition, the above Cu@AuNPs/GCE was successfully employed for the analysis of eugenol in food samples

  10. A novel type of electrochemical sensor based on ferromagnetic carbon-encapsulated iron nanoparticles for direct determination of hemoglobin in blood samples.

    Science.gov (United States)

    Matysiak, Edyta; Donten, Mikolaj; Kowalczyk, Agata; Bystrzejewski, Michal; Grudzinski, Ireneusz P; Nowicka, Anna M

    2015-02-15

    An effective, fast, facile and direct electrochemical method of determination of hemoglobin (Hb) in blood sample without any sample preparation is described. The method is accomplished by using the ferromagnetic electrode modifier (carbon-encapsulated iron nanoparticles) and an external magnetic field. The successful voltammetric determination of hemoglobin is achieved in PBS buffer as well as in the whole blood sample. The obtained results show the excellent electroactivity of Hb. The measurements are of high sensitivity and good reproducibility. The detection limit is estimated to be 0.7 pM. The electrochemical determination data were compared with the gravimetric data obtained with a quartz crystal microbalance. The agreement between these results is very good. The changes of the electrode surface morphology before and after Hb detection are monitored by electron microscopy. The functionality of the electrochemical sensor is tested with human and rat blood samples. The concentration of hemoglobin in the blood samples determined by using voltammetric/gravimetric detection is in perfect agreement with the data obtained from typical clinical analysis. Copyright © 2014 Elsevier B.V. All rights reserved.

  11. Fibroin/dodecanol floating solidification microextraction for the preconcentration of trace levels of flavonoids in complex matrix samples.

    Science.gov (United States)

    Chen, Xuan; Li, Jie; Hu, Shuang; Bai, Xiaohong; Zhao, Haodong; Zhang, Yi

    2018-01-01

    A new fibroin/dodecanol floating solidification microextraction, coupled with high performance liquid chromatography, was developed and applied for enrichment and quantification of the trace flavonoids in traditional Chinese medicine and biological samples. Also, fibroin sensibilization mechanism was described, and influence of sample matrix to enrichment factor was investigated. In this method, a homogeneous fibroin/dodecanol of dispersed solution was employed as microextraction phase to flavonoids (myricetin, quercetin, isorhamnetin, chrysin, kaempferide), the several critical parameters affecting the performance, such as organic extractant, amount of fibroin in organic extractant, volume of extraction phase, dispersant, salt concentration, pH of sample phase, stirring rate, extraction time, and volume of sample phase were tested and optimized. Under the optimized conditions, enrichment factor of flavonoids ranged from 42.4 to 238.1 in different samples, excellent linearities with r 2 ≥ 0.9968 for all analytes were achieved, limits of detection were less than or equal to 5.0ng/mL, average recoveries were 92.5% to 115.0% in different samples. The new procedure is simple, fast, low cost, environmentally friendly and high EF, it can also be applied to the concentration and enrichment of the trace flavonoids in other complex matrixes. Copyright © 2017. Published by Elsevier B.V.

  12. Effect of sample matrix composition on INAA sample weights, measurement precisions, limits of detection, and optimum conditions

    International Nuclear Information System (INIS)

    Guinn, V.P.; Nakazawa, L.; Leslie, J.

    1984-01-01

    The instrumental neutron activation analysis (INAA) Advance Prediction Computer Program (APCP) is extremely useful in guiding one to optimum subsequent experimental analyses of samples of all types of matrices. By taking into account the contributions to the cumulative Compton-continuum levels from all significant induced gamma-emitting radionuclides, it provides good INAA advance estimates of detectable photopeaks, measurement precisions, concentration lower limits of detection (LOD's) and optimum irradiation/decay/counting conditions - as well as of the very important maximum allowable sample size for each set of conditions calculated. The usefulness and importance of the four output parameters cited in the title are discussed using the INAA APCP outputs for NBS SRM-1632 Coal as the example

  13. Matrix-assisted laser desorption/ionization sample preparation optimization for structural characterization of poly(styrene-co-pentafluorostyrene) copolymers.

    Science.gov (United States)

    Tisdale, Evgenia; Kennedy, Devin; Xu, Xiaodong; Wilkins, Charles

    2014-01-15

    The influence of the sample preparation parameters (the choice of the matrix, matrix:analyte ratio, salt:analyte ratio) was investigated and optimal conditions were established for the MALDI time-of-flight mass spectrometry analysis of the poly(styrene-co-pentafluorostyrene) copolymers. These were synthesized by atom transfer radical polymerization. Use of 2,5-dihydroxybenzoic acid as matrix resulted in spectra with consistently high ion yields for all matrix:analyte:salt ratios tested. The optimized MALDI procedure was successfully applied to the characterization of three copolymers obtained by varying the conditions of polymerization reaction. It was possible to establish the nature of the end groups, calculate molecular weight distributions, and determine the individual length distributions for styrene and pentafluorostyrene monomers, contained in the resulting copolymers. Based on the data obtained, it was concluded that individual styrene chain length distributions are more sensitive to the change in the composition of the catalyst (the addition of small amount of CuBr2) than is the pentafluorostyrene component distribution. Copyright © 2013 Elsevier B.V. All rights reserved.

  14. Development of on-line electrochemical sample pretreatment methods for the analysis of thallium and uranium by ICP-MS

    International Nuclear Information System (INIS)

    Zhou, F.; Van Berkel, G.J.; Morton, S.J.; Duckworth, D.C.; Adeniyi, W.K.; Keller, J.M.

    1995-01-01

    Anodic and adsorptive stripping voltammetry (AWV and AdSV, respectively) were performed on-line with a mercury thin-film electrode (MTFE) to effect the selective accumulation and detection of thallium and uranium, respectively. ASV-ICP-MS experiments using thallium as the test element were performed to characterize the behavior of the on-line system for low level and quantitative determinations. Excellent linearity in response was demonstrated for thallium standards ranging from 0.25 ng/L to 50 microg/L. The 1.0 pg/L detection limit calculated from this data for thallium (3σ/sensitivity) was 400 times lower than that of conventional ICP-MS. The ability to overcome sample matrix effects in quantitative determinations was demonstrated by the analysis of an undiluted synthetic urine sample. AdSV-ICP-MS experiments were performed using uranium as the test element to demonstrate the utility of this method for the determination of radiologically important elements. A uranium(VI)-cupferron complex was used to effect adsorptive accumulation of uranium from a 10 microg/L standard solution onto the MTFE. The uranium was chemically stripped from the electrode for subsequent downstream detection by the ICP-MS. The quantitative nature of this method and a modest enhancement of signal levels (∼X10) over those levels obtained with conventional ICP-MS for samples in the microgram/liter concentration range were demonstrated. Modifications to the current system to provide low flow rate operation will allow further optimization of the ASV-ICP-MS and AdSV-ICP-MS combinations

  15. On plate graphite supported sample processing for simultaneous lipid and protein identification by matrix assisted laser desorption ionization mass spectrometry.

    Science.gov (United States)

    Calvano, Cosima Damiana; van der Werf, Inez Dorothé; Sabbatini, Luigia; Palmisano, Francesco

    2015-05-01

    The simultaneous identification of lipids and proteins by matrix assisted laser desorption ionization-mass spectrometry (MALDI-MS) after direct on-plate processing of micro-samples supported on colloidal graphite is demonstrated. Taking advantages of large surface area and thermal conductivity, graphite provided an ideal substrate for on-plate proteolysis and lipid extraction. Indeed proteins could be efficiently digested on-plate within 15 min, providing sequence coverages comparable to those obtained by conventional in-solution overnight digestion. Interestingly, detection of hydrophilic phosphorylated peptides could be easily achieved without any further enrichment step. Furthermore, lipids could be simultaneously extracted/identified without any additional treatment/processing step as demonstrated for model complex samples such as milk and egg. The present approach is simple, efficient, of large applicability and offers great promise for protein and lipid identification in very small samples. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. Reducing matrix effect error in EDXRF: Comparative study of using standard and standard less methods for stainless steel samples

    International Nuclear Information System (INIS)

    Meor Yusoff Meor Sulaiman; Masliana Muhammad; Wilfred, P.

    2013-01-01

    Even though EDXRF analysis has major advantages in the analysis of stainless steel samples such as simultaneous determination of the minor elements, analysis can be done without sample preparation and non-destructive analysis, the matrix issue arise from the inter element interaction can make the the final quantitative result to be in accurate. The paper relates a comparative quantitative analysis using standard and standard less methods in the determination of these elements. Standard method was done by plotting regression calibration graphs of the interested elements using BCS certified stainless steel standards. Different calibration plots were developed based on the available certified standards and these stainless steel grades include low alloy steel, austenitic, ferritic and high speed. The standard less method on the other hand uses a mathematical modelling with matrix effect correction derived from Lucas-Tooth and Price model. Further improvement on the accuracy of the standard less method was done by inclusion of pure elements into the development of the model. Discrepancy tests were then carried out for these quantitative methods on different certified samples and the results show that the high speed method is most reliable for determining of Ni and the standard less method for Mn. (Author)

  17. Double pulse laser induced breakdown spectroscopy: Experimental study of lead emission intensity dependence on the wavelengths and sample matrix

    Energy Technology Data Exchange (ETDEWEB)

    Piscitelli S, V; Martinez L, M A; Fernandez C, A J [Laboratorio de Espectroscopia Laser, Escuela de Quimica, Facultad de Ciencias, Universidad Central de Venezuela, Caracas, DC 1020 (Venezuela, Bolivarian Republic of); Gonzalez, J J; Mao, X L [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Russo, R.E. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)], E-mail: RERusso@lbl.gov

    2009-02-15

    Lead (Pb) emission intensity (atomic line 405.78 nm) dependence on the sample matrix (metal alloy) was studied by means of collinear double pulse (DP)-laser induced breakdown spectroscopy (LIBS). The measurement of the emission intensity produced by three different wavelength combinations (i.e. I:532 nm-II:1064 nm, I:532 nm-II:532 nm, and I:532 nm-II:355 nm) from three series of standard reference materials showed that the lead atomic line 405.78 nm emission intensity was dependent on the sample matrix for all the combination of wavelengths, however reduced dependency was found for the wavelength combination I:532 nm-II:355 nm. Two series of standard reference materials from the National Institute of Standards and Technology (NIST) and one series from the British Chemical Standards (BCS) were used for these experiments. Calibration curves for lead ablated from NIST 626-630 ('Zn{sub 95}Al{sub 4}Cu{sub 1}') provided higher sensitivity (slope) than those calibration curves produced from NIST 1737-1741 ('Zn{sub 99.5}Al{sub 0.5}') and with the series BCS 551-556 ('Cu{sub 87}Sn{sub 11}'). Similar trends between lead emission intensity (calibration curve sensitivities) and reported variations in plasma temperatures caused by the differing ionization potentials of the major and minor elements in these samples were established.

  18. Matrix effects break the LC behavior rule for analytes in LC-MS/MS analysis of biological samples.

    Science.gov (United States)

    Fang, Nianbai; Yu, Shanggong; Ronis, Martin Jj; Badger, Thomas M

    2015-04-01

    High-performance liquid chromatography (HPLC) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) are generally accepted as the preferred techniques for detecting and quantitating analytes of interest in biological matrices on the basis of the rule that one chemical compound yields one LC-peak with reliable retention time (Rt.). However, in the current study, we have found that under the same LC-MS conditions, the Rt. and shape of LC-peaks of bile acids in urine samples from animals fed dissimilar diets differed significantly among each other. To verify this matrix effect, 17 authentic bile acid standards were dissolved in pure methanol or in methanol containing extracts of urine from pigs consuming either breast milk or infant formula and analyzed by LC-MS/MS. The matrix components in urine from piglets fed formula significantly reduced the LC-peak Rt. and areas of bile acids. This is the first characterization of this matrix effect on Rt. in the literature. Moreover, the matrix effect resulted in an unexpected LC behavior: one single compound yielded two LC-peaks, which broke the rule of one LC-peak for one compound. The three bile acid standards which exhibited this unconventional LC behavior were chenodeoxycholic acid, deoxycholic acid, and glycocholic acid. One possible explanation for this effect is that some matrix components may have loosely bonded to analytes, which changed the time analytes were retained on a chromatography column and interfered with the ionization of analytes in the MS ion source to alter the peak area. This study indicates that a comprehensive understanding of matrix effects is needed towards improving the use of HPLC and LC-MS/MS techniques for qualitative and quantitative analyses of analytes in pharmacokinetics, proteomics/metabolomics, drug development, and sports drug testing, especially when LC-MS/MS data are analyzed by automation software where identification of an analyte is based on its exact molecular weight and Rt

  19. Adsorptive stripping voltammetric determination of trace amounts of lead in environmental water samples with complicated matrix

    Directory of Open Access Journals (Sweden)

    Grabarczyk M.

    2013-04-01

    Full Text Available A sensitive, simple and fast adsorptive stripping voltammetric procedure for trace determination of lead in environmental water samples has been developed. The method is based on adsorptive accumulation of the Pb(II-cupferron complex onto a hanging mercury drop electrode, followed by the reduction of the adsorbed species by a voltammetric scan using differential pulse modulation. The interference from surface active substances was eliminated by adsorption of interferents onto an Amberlite XAD-16 resin. Optimumconditions for removing the surfactants by mixing the analysed sample with resin were evaluated. The accuracy of the method was tested by analyzing certified reference material (SPS-WW1 Waste Water.

  20. Use of Matrix Sampling Procedures to Assess Achievement in Solving Open Addition and Subtraction Sentences.

    Science.gov (United States)

    Montague, Margariete A.

    This study investigated the feasibility of concurrently and randomly sampling examinees and items in order to estimate group achievement. Seven 32-item tests reflecting a 640-item universe of simple open sentences were used such that item selection (random, systematic) and assignment (random, systematic) of items (four, eight, sixteen) to forms…

  1. Matrix removal in state of the art sample preparation methods for serum by charged aerosol detection and metabolomics-based LC-MS.

    Science.gov (United States)

    Schimek, Denise; Francesconi, Kevin A; Mautner, Anton; Libiseller, Gunnar; Raml, Reingard; Magnes, Christoph

    2016-04-07

    Investigations into sample preparation procedures usually focus on analyte recovery with no information provided about the fate of other components of the sample (matrix). For many analyses, however, and particularly those using liquid chromatography-mass spectrometry (LC-MS), quantitative measurements are greatly influenced by sample matrix. Using the example of the drug amitriptyline and three of its metabolites in serum, we performed a comprehensive investigation of nine commonly used sample clean-up procedures in terms of their suitability for preparing serum samples. We were monitoring the undesired matrix compounds using a combination of charged aerosol detection (CAD), LC-CAD, and a metabolomics-based LC-MS/MS approach. In this way, we compared analyte recovery of protein precipitation-, liquid-liquid-, solid-phase- and hybrid solid-phase extraction methods. Although all methods provided acceptable recoveries, the highest recovery was obtained by protein precipitation with acetonitrile/formic acid (amitriptyline 113%, nortriptyline 92%, 10-hydroxyamitriptyline 89%, and amitriptyline N-oxide 96%). The quantification of matrix removal by LC-CAD showed that the solid phase extraction method (SPE) provided the lowest remaining matrix load (48-123 μg mL(-1)), which is a 10-40 fold better matrix clean-up than the precipitation- or hybrid solid phase extraction methods. The metabolomics profiles of eleven compound classes, comprising 70 matrix compounds showed the trends of compound class removal for each sample preparation strategy. The collective data set of analyte recovery, matrix removal and matrix compound profile was used to assess the effectiveness of each sample preparation method. The best performance in matrix clean-up and practical handling of small sample volumes was showed by the SPE techniques, particularly HLB SPE. CAD proved to be an effective tool for revealing the considerable differences between the sample preparation methods. This detector can

  2. Preliminary evaluation of new polymer matrix for solid-phase extraction of nonylphenol from water samples.

    Science.gov (United States)

    Guerreiro, António; Soares, Ana; Piletska, Elena; Mattiasson, Bo; Piletsky, Sergey

    2008-03-31

    Molecularly imprinted (MIP) and blank polymers with affinity for nonylphenol were designed using computational modelling. Chromatographic tests demonstrated higher affinity of imprinted polymers towards the template nonylphenol as compared with blank polymers. The performance of both polymers in solid-phase extraction was however very similar. Both blank and imprinted polymers appeared to be suitable for the removal and pre-concentration of nonylphenol from contaminated water samples with 99% efficiency of the recovery. The commercial resins PH(EC) (Biotage) and C18 (Varian) tested in the same conditions used for comparative purposes had recovery rate <84%. The polymer capacity for nonylphenol was 231 mg g(-1) for blank and 228 mg g(-1) for MIP. The synthesised materials can have significance for sample pre-concentration and environmental analysis of this class of compounds.

  3. Development and validation of dried matrix spot sampling for the quantitative determination of amyloid β peptides in cerebrospinal fluid.

    Science.gov (United States)

    Delaby, Constance; Gabelle, Audrey; Meynier, Philippe; Loubiere, Vincent; Vialaret, Jérôme; Tiers, Laurent; Ducos, Jacques; Hirtz, Christophe; Lehmann, Sylvain

    2014-05-01

    The use of dried blood spots on filter paper is well documented as an affordable and practical alternative to classical venous sampling for various clinical needs. This technique has indeed many advantages in terms of collection, biological safety, storage, and shipment. Amyloid β (Aβ) peptides are useful cerebrospinal fluid (CSF) biomarkers for Alzheimer disease diagnosis. However, Aβ determination is hindered by preanalytical difficulties in terms of sample collection and stability in tubes. We compared the quantification of Aβ peptides (1-40, 1-42, and 1-38) by simplex and multiplex ELISA, following either a standard operator method (liquid direct quantification) or after spotting CSF onto dried matrix paper card. The use of dried matrix spot (DMS) overcame preanalytical problems and allowed the determination of Aβ concentrations that were highly commutable (Bland-Altman) with those obtained using CSF in classical tubes. Moreover, we found a positive and significant correlation (r2=0.83, Pearson coefficient p=0.0329) between the two approaches. This new DMS method for CSF represents an interesting alternative that increases the quality and efficiency in preanalytics. This should enable the better exploitation of Aβ analytes for Alzheimer's diagnosis.

  4. Matrix Metalloproteinase-9/Neutrophil Gelatinase-Associated Lipocalin Complex Activity in Human Glioma Samples Predicts Tumor Presence and Clinical Prognosis

    Directory of Open Access Journals (Sweden)

    Ming-Fa Liu

    2015-01-01

    Full Text Available Matrix metalloproteinase-9/neutrophil gelatinase-associated lipocalin (MMP-9/NGAL complex activity is elevated in brain tumors and may serve as a molecular marker for brain tumors. However, the relationship between MMP-9/NGAL activity in brain tumors and patient prognosis and treatment response remains unclear. Here, we compared the clinical characteristics of glioma patients with the MMP-9/NGAL activity measured in their respective tumor and urine samples. Using gelatin zymography assays, we found that MMP-9/NGAL activity was significantly increased in tumor tissues (TT and preoperative urine samples (Preop-1d urine. Activity was reduced by seven days after surgery (Postop-1w urine and elevated again in cases of tumor recurrence. The MMP-9/NGAL status correlated well with MRI-based tumor assessments. These findings suggest that MMP-9/NGAL activity could be a novel marker to detect gliomas and predict the clinical outcome of patients.

  5. Dependence of matrix effect on ionization polarity during LC-ESI-MS analysis of derivatized amino acids in some natural samples.

    Science.gov (United States)

    Oldekop, Maarja-Liisa; Rebane, Riin; Herodes, Koit

    2017-10-01

    Matrix effect, the influence of co-eluting components on the ionization efficiency of the analyte, affects the trueness and precision of the LC-ESI-MS analysis. Derivatization can reduce or eliminate matrix effect, for example, diethyl ethoxymethylenemalonate (DEEMM) derivatives have shown less matrix effect compared to other derivatives. Moreover, the use of negative ion mode can further reduce matrix effect. In order to investigate the combination of derivatization and different ionization modes, an LC-ESI-MS/MS method using alternating positive/negative ion mode was developed and validated. The analyses in positive and negative ion modes had comparable limit of quantitation values. The influence of ESI polarity on matrix effect was investigated during the analysis of 22 DEEMM-derivatized amino acids in herbal extracts and honeys. Sample dilution approach was used for the evaluation of the presence of matrix effect. Altogether, 4 honeys and 11 herbal extracts were analyzed, and the concentrations of 22 amino acids in the samples are presented. In the positive ion mode, matrix effect was observed for several amino acid derivatives and the matrix effect was stronger in honey samples compared to the herbal extracts. The negative ion mode was free from matrix effect, with only few exceptions in honeys (average relative standard deviation over all analytes and matrices was 8%; SD = 7%). The matrix effect was eliminated in the positive ion mode by sample dilution and agreement between concentrations from the two ion modes was achieved for most amino acids. In conclusion, it was shown that the combination of derivatization and negative ion mode can be a powerful tool for minimizing matrix effect in more complicated applications.

  6. Quality Assessment of Platelet-Rich Fibrin-Like Matrix Prepared from Whole Blood Samples after Extended Storage

    Directory of Open Access Journals (Sweden)

    Hideo Kawabata

    2017-09-01

    Full Text Available The platelet-rich fibrin–like matrix (PRFM is usually prepared onsite and immediately used for regenerative therapy. Nonetheless, to meet the clinical necessity of preserving the PRFM without quality deterioration, we developed a method for preparation of PRFMs from short-term-stored whole blood (WB samples. In this study, to evaluate the practical expiration date of storage, we extended the storage time of WB samples from 2 to 7 days and assessed the quality of the resulting PRFMs. WB samples collected with acid-citrate-dextrose were stored with gentle agitation at ambient temperature. To prepare PRFMs, the stored WB samples were mixed with CaCl2 in glass tubes and centrifuged. Fibrin fiber networks, CD41 and CD62P expression, and Platelet Derived Growth Factor-BB (PDGF-BB levels were examined by scanning electron microscopy (SEM, flow cytometry, and an Enzyme-Linked ImmunoSorbent Assay (ELISA, respectively. Long-term storage had no significant effect on either blood cell counts or platelet functions tested. The resulting PRFMs were visually identical to freshly prepared ones. PDGF-BB levels did not markedly decrease in a time-dependent manner. However, fibrin fibers gradually became thinner after storage. Although the coagulation activity may diminish, we propose that PRFMs can be prepared—without evident loss of quality—from WB samples stored for up to 7 days by our previously developed method.

  7. Double use of focused microwave irradiation for accelerated matrix hydrolysis and lipid extraction in milk samples

    International Nuclear Information System (INIS)

    Garcia-Ayuso, L.E.; Luque de Castro, M.D.; Velasco, J.; Dobarganes, M.C.

    1999-01-01

    Irradiation with microwave energy has allowed to carry out the extraction of lipids from milk samples (namely, cow, goat and sheep) with quantitative results similar to the Weibull–Berntrop extraction procedure but milk fat obtained by microwave assisted extraction undergoes lesser chemical transformation of triglycerides during the whole process. A considerable reduction of the procedure time (50 min versus 10 h) is achieved with similar reproducibility to that provided by the conventional method. An in situ’ solvent recycling step makes the method environmentally clean

  8. Electrochemical sample preparation for the determination of Cd, Pb, and Cu in the presence of surfactants by stripping voltammetry

    International Nuclear Information System (INIS)

    Svintsova, L.D.; Chernysheva, N.N.

    1997-01-01

    The electrochemical pretreatment of aqueous solutions of synthetic surfactants in a diaphragm elelctrolyzer was used in order to diminish surfactant interference. The determination of cadmium, lead, and copper by stripping voltammetry with a mercury-film electrode in model solutions of cetylpyriridinium chloride, sodium lauryl sulfate, and OP-10 was taken as an example. It was found that the reproducibility of anodic peaks of the elements was improved, and the linearity of calibration characteristics was recovered; however, the sensitivity was not always as high as the value in the blank experiment

  9. Critical points of DNA quantification by real-time PCR – effects of DNA extraction method and sample matrix on quantification of genetically modified organisms

    Directory of Open Access Journals (Sweden)

    Žel Jana

    2006-08-01

    Full Text Available Abstract Background Real-time PCR is the technique of choice for nucleic acid quantification. In the field of detection of genetically modified organisms (GMOs quantification of biotech products may be required to fulfil legislative requirements. However, successful quantification depends crucially on the quality of the sample DNA analyzed. Methods for GMO detection are generally validated on certified reference materials that are in the form of powdered grain material, while detection in routine laboratories must be performed on a wide variety of sample matrixes. Due to food processing, the DNA in sample matrixes can be present in low amounts and also degraded. In addition, molecules of plant origin or from other sources that affect PCR amplification of samples will influence the reliability of the quantification. Further, the wide variety of sample matrixes presents a challenge for detection laboratories. The extraction method must ensure high yield and quality of the DNA obtained and must be carefully selected, since even components of DNA extraction solutions can influence PCR reactions. GMO quantification is based on a standard curve, therefore similarity of PCR efficiency for the sample and standard reference material is a prerequisite for exact quantification. Little information on the performance of real-time PCR on samples of different matrixes is available. Results Five commonly used DNA extraction techniques were compared and their suitability for quantitative analysis was assessed. The effect of sample matrix on nucleic acid quantification was assessed by comparing 4 maize and 4 soybean matrixes. In addition 205 maize and soybean samples from routine analysis were analyzed for PCR efficiency to assess variability of PCR performance within each sample matrix. Together with the amount of DNA needed for reliable quantification, PCR efficiency is the crucial parameter determining the reliability of quantitative results, therefore it was

  10. Critical points of DNA quantification by real-time PCR--effects of DNA extraction method and sample matrix on quantification of genetically modified organisms.

    Science.gov (United States)

    Cankar, Katarina; Stebih, Dejan; Dreo, Tanja; Zel, Jana; Gruden, Kristina

    2006-08-14

    Real-time PCR is the technique of choice for nucleic acid quantification. In the field of detection of genetically modified organisms (GMOs) quantification of biotech products may be required to fulfil legislative requirements. However, successful quantification depends crucially on the quality of the sample DNA analyzed. Methods for GMO detection are generally validated on certified reference materials that are in the form of powdered grain material, while detection in routine laboratories must be performed on a wide variety of sample matrixes. Due to food processing, the DNA in sample matrixes can be present in low amounts and also degraded. In addition, molecules of plant origin or from other sources that affect PCR amplification of samples will influence the reliability of the quantification. Further, the wide variety of sample matrixes presents a challenge for detection laboratories. The extraction method must ensure high yield and quality of the DNA obtained and must be carefully selected, since even components of DNA extraction solutions can influence PCR reactions. GMO quantification is based on a standard curve, therefore similarity of PCR efficiency for the sample and standard reference material is a prerequisite for exact quantification. Little information on the performance of real-time PCR on samples of different matrixes is available. Five commonly used DNA extraction techniques were compared and their suitability for quantitative analysis was assessed. The effect of sample matrix on nucleic acid quantification was assessed by comparing 4 maize and 4 soybean matrixes. In addition 205 maize and soybean samples from routine analysis were analyzed for PCR efficiency to assess variability of PCR performance within each sample matrix. Together with the amount of DNA needed for reliable quantification, PCR efficiency is the crucial parameter determining the reliability of quantitative results, therefore it was chosen as the primary criterion by which to

  11. Critical points of DNA quantification by real-time PCR – effects of DNA extraction method and sample matrix on quantification of genetically modified organisms

    Science.gov (United States)

    Cankar, Katarina; Štebih, Dejan; Dreo, Tanja; Žel, Jana; Gruden, Kristina

    2006-01-01

    Background Real-time PCR is the technique of choice for nucleic acid quantification. In the field of detection of genetically modified organisms (GMOs) quantification of biotech products may be required to fulfil legislative requirements. However, successful quantification depends crucially on the quality of the sample DNA analyzed. Methods for GMO detection are generally validated on certified reference materials that are in the form of powdered grain material, while detection in routine laboratories must be performed on a wide variety of sample matrixes. Due to food processing, the DNA in sample matrixes can be present in low amounts and also degraded. In addition, molecules of plant origin or from other sources that affect PCR amplification of samples will influence the reliability of the quantification. Further, the wide variety of sample matrixes presents a challenge for detection laboratories. The extraction method must ensure high yield and quality of the DNA obtained and must be carefully selected, since even components of DNA extraction solutions can influence PCR reactions. GMO quantification is based on a standard curve, therefore similarity of PCR efficiency for the sample and standard reference material is a prerequisite for exact quantification. Little information on the performance of real-time PCR on samples of different matrixes is available. Results Five commonly used DNA extraction techniques were compared and their suitability for quantitative analysis was assessed. The effect of sample matrix on nucleic acid quantification was assessed by comparing 4 maize and 4 soybean matrixes. In addition 205 maize and soybean samples from routine analysis were analyzed for PCR efficiency to assess variability of PCR performance within each sample matrix. Together with the amount of DNA needed for reliable quantification, PCR efficiency is the crucial parameter determining the reliability of quantitative results, therefore it was chosen as the primary

  12. Electrochemical studies of nevirapine, an anti-HIV drug, and its assay in tablets and biological samples

    Directory of Open Access Journals (Sweden)

    JALDAPPAGARI SEETHARAMAPPA

    2012-06-01

    Full Text Available The electrochemical oxidation of nevirapine, an anti-HIV drug, at a glassy carbon electrode has been studied by voltammetric techniques. Nevirapine showed one well defined irreversible oxidation peak with a potential of 0.749 V in phosphate buffer at pH 10. The effects of different electrolytes, pH and scan rate on the electrochemical behaviour of nevira¬pine were examined to determine the optimum reaction conditions. The oxidation peak current was found to vary linearly with the concentration of nevirapine in the range of 5.0 – 350 µM. The limit of detection and limit of quantification values were calculated and found to be 1.026 µM and 3.420 µM, respectively. The low relative standard deviation values of inter-day and intra-day assays highlighted the good reproducibility of the proposed m¬ethod for assay of nevirapine. Further, a sensitive and accurate differential pulse voltammetric method was developed for the determination of nevirapine concentrations in pharma¬ceutical formulations.

  13. Sensitive and selective determination of gallic acid in green tea samples based on an electrochemical platform of poly(melamine) film

    Energy Technology Data Exchange (ETDEWEB)

    Su, Ya-Ling; Cheng, Shu-Hua, E-mail: shcheng@ncnu.edu.tw

    2015-12-11

    In this work, an electrochemical sensor coupled with an effective flow-injection amperometry (FIA) system is developed, targeting the determination of gallic acid (GA) in a mild neutral condition, in contrast to the existing electrochemical methods. The sensor is based on a thin electroactive poly(melamine) film immobilized on a pre-anodized screen-printed carbon electrode (SPCE*/PME). The characteristics of the sensing surface are well-characterized by field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and surface water contact angle experiments. The proposed assay exhibits a wide linear response to GA in both pH 3 and pH 7.0 phosphate buffer solutions (PBS) under the optimized flow-injection amperometry. The detection limit (S/N = 3) is 0.076 μM and 0.21 μM in the pH 3 and pH 7 solutions, respectively. A relative standard deviation (RSD) of 3.9% is obtained for 57 successive measurements of 50 μM GA in pH 7 solutions. Interference studies indicate that some inorganic salts, catechol, caffeine and ascorbic acid do not interfere with the GA assay. The interference effects from some orthodiphenolic compounds are also investigated. The proposed method and a conventional Folin–Ciocalteu method are applied to detect GA in green tea samples using the standard addition method, and satisfactory spiked recoveries are obtained. - Highlights: • A nitrogen-rich conducting polymer was used for electroanalysis of gallic acid. • The sensor exhibits excellent electrochemical activity in both acidic and neutral media. • Good analytical results in terms of low detection limit and wide linear range are obtained. • The flow-injection amperometric assay is highly stable for continuous 57 replicates measurement (RSD = 3.9%). • The assay shows good recovery for green tea samples.

  14. Sensitive and selective determination of gallic acid in green tea samples based on an electrochemical platform of poly(melamine) film

    International Nuclear Information System (INIS)

    Su, Ya-Ling; Cheng, Shu-Hua

    2015-01-01

    In this work, an electrochemical sensor coupled with an effective flow-injection amperometry (FIA) system is developed, targeting the determination of gallic acid (GA) in a mild neutral condition, in contrast to the existing electrochemical methods. The sensor is based on a thin electroactive poly(melamine) film immobilized on a pre-anodized screen-printed carbon electrode (SPCE*/PME). The characteristics of the sensing surface are well-characterized by field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and surface water contact angle experiments. The proposed assay exhibits a wide linear response to GA in both pH 3 and pH 7.0 phosphate buffer solutions (PBS) under the optimized flow-injection amperometry. The detection limit (S/N = 3) is 0.076 μM and 0.21 μM in the pH 3 and pH 7 solutions, respectively. A relative standard deviation (RSD) of 3.9% is obtained for 57 successive measurements of 50 μM GA in pH 7 solutions. Interference studies indicate that some inorganic salts, catechol, caffeine and ascorbic acid do not interfere with the GA assay. The interference effects from some orthodiphenolic compounds are also investigated. The proposed method and a conventional Folin–Ciocalteu method are applied to detect GA in green tea samples using the standard addition method, and satisfactory spiked recoveries are obtained. - Highlights: • A nitrogen-rich conducting polymer was used for electroanalysis of gallic acid. • The sensor exhibits excellent electrochemical activity in both acidic and neutral media. • Good analytical results in terms of low detection limit and wide linear range are obtained. • The flow-injection amperometric assay is highly stable for continuous 57 replicates measurement (RSD = 3.9%). • The assay shows good recovery for green tea samples.

  15. Electrochemically assisted fast-atom-bombardment mass spectrometry

    International Nuclear Information System (INIS)

    Phillips, L.R.

    1988-01-01

    The hybridization of electrochemistry and fast atom bombardment (FAB) mass spectrometry (MS) creates a new hyphenated technique, referred to as electrochemically assisted FAB (EFAB) MS, which improves the applicability of FAB MS in selectivity and extends the range of compounds to include low polarity molecules, and also reduces mass spectral complications due to matrix-related artifacts. FAB MS has proven to be indispensable in analysis of samples that are otherwise too intractable for conventional MS, such as peptides, oligosaccharides, and oligonucleotides, due to low volatility and ready thermal degradation. There are limits on its applicability, however, in that it works best with samples that are already ionic, or predisposed to become so by simple proton transfer to or from the matrix. A wide range of chemical substances can be ionized/analyzed by electrochemical methods. Therefore, a possible approach towards improving applicability of FAB MS is through its hybridization with electrochemistry. Samples are activated by electrolysis, carried out directly in the sample matrix through use of a modified FAB sample probe which was constructed containing a small electrolytic cell on the tip. In operation, one electrode is held at normal sample-probe/ion-source voltage, while the other electrode can be continuously varied ±15 volts to create electrochemical potentials. Several chemical substances, known to be unresponsive to FAB MS, have been examined by EFAB MS. Resultant spectra generally show a dramatic increases in signal/chemical noise ratio of structurally significant ions when compared to normal FAB spectra

  16. Determination of arsenic and cadmium in shellfish samples by graphite furnace atomic absorption spectrometry using matrix modifier

    International Nuclear Information System (INIS)

    Cortez Diaz, Mirella del Carmen

    2002-01-01

    Heavy metals are a big source of environmental contamination and are also highly toxic to humans. Since shellfish are bio-accumulators of these metals, proper techniques for quantifying them should be available. This work aims to develop an analytical method for the quantitative determination of heavy metals in biological materials (shellfish), specifically arsenic and cadmium at the trace level, using graphite furnace atomic absorption spectrometry, for which nickel and phosphate solutions were used to modify the modifiers. Prior to the analysis, the sample was diluted with nitric acid in a DAB II pressure digestion system order to destroy the organic matter. The instrument conditions were initially set (wavelength, slit, integration peaks, graphite tube, etc.), then the work range was defined for each element and the most appropriate operational parameters were studied, such as: temperature, ramp times, hold times and internal gas flow, in the different stage of the electrothermal treatment (drying, calcination, atomization) for the furnace program. Once the above mentioned conditions were set and since this was a biological sample, a matrix chemical modifier had to be used, in order to make the elements that accompany the element being studied more volatile. In this way the chemical and spectral interferences decrease together with the high background absorption of the matrix. Therefore, different matrix modifiers were studied for the definition of each analyte. The method validation was done using Certified Oyster Tissue Reference Material N o 1566a from the National Institute of Standards and Technology applying different tests in order to eliminate outliers. Repeatability, uncertainty, sensitivity, lineal range, working range, detection limit and quantification limit were evaluated for each element, and the results were compared with the values for the certified material. The Fisher and Student tests were the statistical tools used. The experimental values

  17. Dense sampled transmission matrix for high resolution angular spectrum imaging through turbid media via compressed sensing (Conference Presentation)

    Science.gov (United States)

    Jang, Hwanchol; Yoon, Changhyeong; Choi, Wonshik; Eom, Tae Joong; Lee, Heung-No

    2016-03-01

    We provide an approach to improve the quality of image reconstruction in wide-field imaging through turbid media (WITM). In WITM, a calibration stage which measures the transmission matrix (TM), the set of responses of turbid medium to a set of plane waves with different incident angles, is preceded to the image recovery. Then, the TM is used for estimation of object image in image recovery stage. In this work, we aim to estimate highly resolved angular spectrum and use it for high quality image reconstruction. To this end, we propose to perform a dense sampling for TM measurement in calibration stage with finer incident angle spacing. In conventional approaches, incident angle spacing is made to be large enough so that the columns in TM are out of memory effect of turbid media. Otherwise, the columns in TM are correlated and the inversion becomes difficult. We employ compressed sensing (CS) for a successful high resolution angular spectrum recovery with dense sampled TM. CS is a relatively new information acquisition and reconstruction framework and has shown to provide superb performance in ill-conditioned inverse problems. We observe that the image quality metrics such as contrast-to-noise ratio and mean squared error are improved and the perceptual image quality is improved with reduced speckle noise in the reconstructed image. This results shows that the WITM performance can be improved only by executing dense sampling in the calibration stage and with an efficient signal reconstruction framework without elaborating the overall optical imaging systems.

  18. Preparation and evaluation of a novel molecularly imprinted polymer coating for selective extraction of indomethacin from biological samples by electrochemically controlled in-tube solid phase microextraction

    Energy Technology Data Exchange (ETDEWEB)

    Asiabi, Hamid [Department of Chemistry, Tarbiat Modares University, P.O. Box 14115-175, Tehran (Iran, Islamic Republic of); Yamini, Yadollah, E-mail: yyamini@modares.ac.ir [Department of Chemistry, Tarbiat Modares University, P.O. Box 14115-175, Tehran (Iran, Islamic Republic of); Seidi, Shahram; Ghahramanifard, Fazel [Department of Analytical Chemistry, Faculty of Chemistry, K.N. Toosi University of Technology, Tehran (Iran, Islamic Republic of)

    2016-03-24

    In the present work, an automated on-line electrochemically controlled in-tube solid-phase microextraction (EC-in-tube SPME) coupled with HPLC-UV was developed for the selective extraction and preconcentration of indomethacin as a model analyte in biological samples. Applying an electrical potential can improve the extraction efficiency and provide more convenient manipulation of different properties of the extraction system including selectivity, clean-up, rate, and efficiency. For more enhancement of the selectivity and applicability of this method, a novel molecularly imprinted polymer coated tube was prepared and applied for extraction of indomethacin. For this purpose, nanostructured copolymer coating consisting of polypyrrole doped with ethylene glycol dimethacrylate was prepared on the inner surface of a stainless-steel tube by electrochemical synthesis. The characteristics and application of the tubes were investigated. Electron microscopy provided a cross linked porous surface and the average thickness of the MIP coating was 45 μm. Compared with the non-imprinted polymer coated tubes, the special selectivity for indomethacin was discovered with the molecularly imprinted coated tube. Moreover, stable and reproducible responses were obtained without being considerably influenced by interferences commonly existing in biological samples. Under the optimal conditions, the limits of detection were in the range of 0.07–2.0 μg L{sup −1} in different matrices. This method showed good linearity for indomethacin in the range of 0.1–200 μg L{sup −1}, with coefficients of determination better than 0.996. The inter- and intra-assay precisions (RSD%, n = 3) were respectively in the range of 3.5–8.4% and 2.3–7.6% at three concentration levels of 7, 70 and 150 μg L{sup −1}. The results showed that the proposed method can be successfully applied for selective analysis of indomethacin in biological samples. - Graphical abstract: An automated on

  19. Baseline Design Compliance Matrix for the Type 4 In Situ Vapor Samplers and Supernate and Sludge and Soft Saltcake Grab Sampling

    International Nuclear Information System (INIS)

    BOGER, R.M.

    2000-01-01

    The DOE has identified a need to sample vapor space, exhaust ducts, supernate, sludge, and soft saltcake in waste tanks that store radioactive waste. This document provides the Design Compliance Matrix (DCM) for the Type 4 In-Situ Vapor Sampling (ISVS) system and the Grab Sampling System that are used for completing this type of sampling function. The DCM identifies the design requirements and the source of the requirements for the Type 4 ISVS system and the Grab Sampling system. The DCM is a single-source compilation design requirements for sampling and sampling support equipment and supports the configuration management of these systems

  20. Predicting the required number of training samples. [for remotely sensed image data based on covariance matrix estimate quality criterion of normal distribution

    Science.gov (United States)

    Kalayeh, H. M.; Landgrebe, D. A.

    1983-01-01

    A criterion which measures the quality of the estimate of the covariance matrix of a multivariate normal distribution is developed. Based on this criterion, the necessary number of training samples is predicted. Experimental results which are used as a guide for determining the number of training samples are included. Previously announced in STAR as N82-28109

  1. Electrochemical attosyringe.

    Science.gov (United States)

    Laforge, François O; Carpino, James; Rotenberg, Susan A; Mirkin, Michael V

    2007-07-17

    The ability to manipulate ultrasmall volumes of liquids is essential in such diverse fields as cell biology, microfluidics, capillary chromatography, and nanolithography. In cell biology, it is often necessary to inject material of high molecular weight (e.g., DNA, proteins) into living cells because their membranes are impermeable to such molecules. All techniques currently used for microinjection are plagued by two common problems: the relatively large injector size and volume of injected fluid, and poor control of the amount of injected material. Here we demonstrate the possibility of electrochemical control of the fluid motion that allows one to sample and dispense attoliter-to-picoliter (10(-18) to 10(-12) liter) volumes of either aqueous or nonaqueous solutions. By changing the voltage applied across the liquid/liquid interface, one can produce a sufficient force to draw solution inside a nanopipette and then inject it into an immobilized biological cell. A high success rate was achieved in injections of fluorescent dyes into cultured human breast cells. The injection of femtoliter-range volumes can be monitored by video microscopy, and current/resistance-based approaches can be used to control injections from very small pipettes. Other potential applications of the electrochemical syringe include fluid dispensing in nanolithography and pumping in microfluidic systems.

  2. Numerical stability of finite difference algorithms for electrochemical kinetic simulations: Matrix stability analysis of the classic explicit, fully implicit and Crank-Nicolson methods and typical problems involving mixed boundary conditions

    DEFF Research Database (Denmark)

    Bieniasz, Leslaw K.; Østerby, Ole; Britz, Dieter

    1995-01-01

    The stepwise numerical stability of the classic explicit, fully implicit and Crank-Nicolson finite difference discretizations of example diffusional initial boundary value problems from electrochemical kinetics has been investigated using the matrix method of stability analysis. Special attention...... has been paid to the effect of the discretization of the mixed, linear boundary condition with time-dependent coefficients on stability, assuming the two-point forward-difference approximations for the gradient at the left boundary (electrode). Under accepted assumptions one obtains the usual...... stability criteria for the classic explicit and fully implicit methods. The Crank-Nicolson method turns out to be only conditionally stable in contrast to the current thought regarding this method....

  3. Simultaneous Automatic Electrochemical Detection of Zinc, Cadmium, Copper and Lead Ions in Environmental Samples Using a Thin-Film Mercury Electrode and an Artificial Neural Network

    Directory of Open Access Journals (Sweden)

    Jiri Kudr

    2014-12-01

    Full Text Available In this study a device for automatic electrochemical analysis was designed. A three electrodes detection system was attached to a positioning device, which enabled us to move the electrode system from one well to another of a microtitre plate. Disposable carbon tip electrodes were used for Cd(II, Cu(II and Pb(II ion quantification, while Zn(II did not give signal in this electrode configuration. In order to detect all mentioned heavy metals simultaneously, thin-film mercury electrodes (TFME were fabricated by electrodeposition of mercury on the surface of carbon tips. In comparison with bare electrodes the TMFEs had lower detection limits and better sensitivity. In addition to pure aqueous heavy metal solutions, the assay was also performed on mineralized rock samples, artificial blood plasma samples and samples of chicken embryo organs treated with cadmium. An artificial neural network was created to evaluate the concentrations of the mentioned heavy metals correctly in mixture samples and an excellent fit was observed (R2 = 0.9933.

  4. Determination of arsenic and cadmium in shellfish samples by graphite furnace atomic absorption spectrometry using matrix modifier

    International Nuclear Information System (INIS)

    Villalobos Aranda, Juan; Cortez Diaz, Mirella

    2003-01-01

    Serious problems of environmental contamination due to the activity of the man exist at the present time. Where the greater impact is the produced one by heavy metals that go to the sea. Where the shellfish can collect some of them, the highly toxic ones, since these are bioaccumulation of these metals. Therefore one becomes necessary to count with the reliable analytical procedures to determine these elements. The purpose of this work is to present the determination of arsenic and cadmium in shellfish, by spectroscopy of atomic absorption with graphite furnace. For each determined element, solutions of nickel and phosphate like matrix modifiers were used respectively The validation was made using a Reference Certified Material, Oyster ' Tissue 156 (National Institute of Standards and Technology). The sample previously was digested in triplicate by two consecutive days, with nitric acid in a pressure digestion system DAB 11. For each element it was evaluated: limit of detection and quantification, sensitivity, repeatability, linear, slope rank and uncertainty. In addition, the obtained results were compared with the certified values of the certified material of reference using like statistical tools the tests of Student and Fisher. In both tests the calculated values were smaller to the shown ones in table, for degrees of freedom with 95% of confidence. Thus it was verified that it does not exist significant differences between the precision and the average values of the results obtained with respect to the values of the certified material. In addition, the obtained parameters are appropriate for the determination of these trace elements in this type of environmental sample (author)

  5. Vortex-homogenized matrix solid-phase dispersion for the extraction of short chain chlorinated paraffins from indoor dust samples.

    Science.gov (United States)

    Chen, Yu-Hsuan; Chang, Chia-Yu; Ding, Wang-Hsien

    2016-11-11

    A simple and effective method for determining short chain chlorinated paraffins (SCCPs) in indoor dust is presented. The method employed a modified vortex-homogenized matrix solid-phase dispersion (VH-MSPD) prior to its detection by gas chromatography - electron-capture negative-ion mass spectrometry (GC-ECNI-MS) operating in the selected-ion-monitoring (SIM) mode. Under the best extraction conditions, 0.1-g of dust sample was dispersed with 0.1-g of silica gel by using vortex (2min) instead of using a mortar and pestle (3min). After that step, the blend was transferred to a glass column containing 3-g acidic silica gel, 2-g basic silica gel, and 2-g of deactivated silica gel, used as clean-up co-sorbents. Then, target analytes were eluted with 5mL of n-hexane/dichloromethane (2:1, v/v) mixture. The extract was evaporated to dryness under a gentle stream of nitrogen. The residue was then re-dissolved in n-hexane (10μL), and subjected to GC-ECNI-MS analysis. The limits of quantitation (LOQs) ranged from 0.06 to 0.25μg/g for each SCCP congener. Precision was less than 7% for both intra- and inter-day analysis. Trueness was above 89%, which was calculated by mean extraction recovery. The VH-MSPD combined with GC-ECNI-MS was successfully applied to quantitatively detect SCCPs from various indoor dust samples, and the concentrations ranged from 1.2 to 31.2μg/g. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. Independent assessment of matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) sample preparation quality : Effect of sample preparation on MALDI-MS of synthetic polymers

    NARCIS (Netherlands)

    Kooijman, Pieter C.; Kok, Sander; Honing, Maarten

    2017-01-01

    Rationale: Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) provides detailed and in-depth information about the molecular characteristics of synthetic polymers. To obtain the most accurate results the sample preparation parameters should be chosen to suit the sample and the

  7. Measurement of K-27, an oxime-type cholinesterase reactivator by high-performance liquid chromatography with electrochemical detection from different biological samples.

    Science.gov (United States)

    Gyenge, Melinda; Kalász, Huba; Petroianu, George A; Laufer, Rudolf; Kuca, Kamil; Tekes, Kornélia

    2007-08-17

    K-27 is a bisquaternary asymmetric pyridinium aldoxime-type cholinesterase reactivator of use in the treatment of poisoning with organophosphorous esterase inhibitors. A sensitive, simple and reliable reverse-phase high-performance liquid chromatographic method with electrochemical detection was developed for the measurement of K-27 concentrations in rat brain, cerebrospinal fluid, serum and urine samples. Male Wistar rats were treated intramuscularly with K-27 and the samples were collected 60 min later. Separation was carried out on an octadecyl silica stationary phase and a disodium phosphate solution (pH 3.7) containing citric acid, octane sulphonic acid and acetonitrile served as mobile phase. Measurements were carried out at 30 degrees C at E(ox) 0.65 V. The calibration curve was linear through the range of 10-250 ng/mL. Accuracy, precision and the limit of detection calculated were satisfactory according to internationally accepted criteria. Limit of quantitation was 10 ng/mL. The method developed is reliable and sensitive enough for monitoring K-27 levels from different biological samples including as little as 10 microL of cerebrospinal fluid. The method--with slight modification in the composition of the mobile phase--can be used to measure a wide range of other related pyridinium aldoxime-type cholinesterase reactivators.

  8. In-line electrochemical reagent generation coupled to a flow injection biamperometric system for the determination of sulfite in beverage samples.

    Science.gov (United States)

    de Paula, Nattany T G; Barbosa, Elaine M O; da Silva, Paulo A B; de Souza, Gustavo C S; Nascimento, Valberes B; Lavorante, André F

    2016-07-15

    This work reports an in-line electrochemical reagent generation coupled to a flow injection biamperometric procedure for the determination of SO3(2-). The method was based on a redox reaction between the I3(-) and SO3(2-) ions, after the diffusion of SO2 through a gas diffusion chamber. Under optimum experimental conditions, a linear response ranging from 1.0 to 12.0 mg L(-1) (R=0.9999 and n=7), a detection and quantification limit estimated at 0.26 and 0.86 mg L(-1), respectively, a standard deviation relative of 0.4% (n=10) for a reference solution of 4.0 mg L(-1) SO3(2-) and sampling throughput for 40 determinations per hour were achieved. Addition and recovery tests with juice and wine samples were performed resulting in a range between 92% and 110%. There were no significant differences at a 95% confidence level in the analysis of eight samples when comparing the new method with a reference procedure. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Horseradish peroxidase and antibody labeled gold nanoparticle probe for amplified immunoassay of ciguatoxin in fish samples based on capillary electrophoresis with electrochemical detection.

    Science.gov (United States)

    Zhang, Zhaoxiang; Liu, Ying; Zhang, Chaoying; Luan, Wenxiu

    2015-03-01

    This paper describes a new amplified immunoassay with horseradish peroxidase (HRP) and antibody (Ab) labeled gold nanoparticles (AuNPs) probe hyphenated to capillary electrophoresis (CE) with electrochemical (EC) detection for ultrasensitive determination of ciguatoxin CTX1B. AuNPs were conjugated with HRP and Ab, and then incubated with limited amount of CTX1B to produce immunocomplex. The immunoreactive sample was injected into capillary for CE separation and EC detection. Enhanced sensitivity was obtained by adopting the AuNPs as carriers of HRP and Ab at high HRP/Ab molar ratio. The calibration curve of CTX1B was in the range of 0.06-90 ng/mL. The detection limit was 0.045 ng/mL, which is 38-fold lower than that of HPLC-MS method for CTX1B analysis. The proposed method was successfully applied for the quantification of CTX1B in contamined fish samples by simultaneously labeling Ab and HRP on AuNPs. The amplified IA with HRP and Ab labeled AuNPs probe hyphenated to CE and EC detection provides a sensitive analytical approach for the determination of trace ciguatoxin in complex samples. Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. Synthesis and application of bismuth ferrite nanosheets supported functionalized carbon nanofiber for enhanced electrochemical detection of toxic organic compound in water samples.

    Science.gov (United States)

    Ramaraj, Sukanya; Mani, Sakthivel; Chen, Shen-Ming; Kokulnathan, Thangavelu; Lou, Bih-Show; Ali, M Ajmal; Hatamleh, A A; Al-Hemaid, Fahad M A

    2018-03-15

    Recently, the multiferroic material has fabulous attention in numerous applications owing to its excellent electronic conductivity, unique mechanical property, and higher electrocatalytic activity, etc. In this paper, we reported that the synthesis of bismuth ferrite (BiFeO 3 ) nanosheets integrated functionalized carbon nanofiber (BiFeO 3 NS/F-CNF) nanocomposite using a simple hydrothermal technique. Herein, the structural changes and crystalline property of prepared BiFeO 3 NS/F-CNF nanocomposite were characterized using Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). From this detailed structural evolution, the formation of nanosheets like BiFeO 3 and its nanocomposite with F-CNF were scrutinized and reported. Furthermore, the as-prepared BiFeO 3 NS/F-CNF nanocomposite modified glassy carbon electrode (GCE) was applied for electrochemical detection of catechol (CC). As expected, BiFeO 3 NS/F-CNF/GCE shows excellent electrocatalytic activity as well as 3.44 (F-CNF/GCE) and 7.92 (BiFeO 3 NS/GCE) fold higher electrochemical redox response for CC sensing. Moreover, the proposed sensor displays a wide linear range from 0.003 to 78.02 µM with a very low detection limit of 0.0015 µM. In addition, we have validated the real-time application of our developed CC sensor in different water samples. Copyright © 2017 Elsevier Inc. All rights reserved.

  11. Sensitive and selective determination of gallic acid in green tea samples based on an electrochemical platform of poly(melamine) film.

    Science.gov (United States)

    Su, Ya-Ling; Cheng, Shu-Hua

    2015-12-11

    In this work, an electrochemical sensor coupled with an effective flow-injection amperometry (FIA) system is developed, targeting the determination of gallic acid (GA) in a mild neutral condition, in contrast to the existing electrochemical methods. The sensor is based on a thin electroactive poly(melamine) film immobilized on a pre-anodized screen-printed carbon electrode (SPCE*/PME). The characteristics of the sensing surface are well-characterized by field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and surface water contact angle experiments. The proposed assay exhibits a wide linear response to GA in both pH 3 and pH 7.0 phosphate buffer solutions (PBS) under the optimized flow-injection amperometry. The detection limit (S/N = 3) is 0.076 μM and 0.21 μM in the pH 3 and pH 7 solutions, respectively. A relative standard deviation (RSD) of 3.9% is obtained for 57 successive measurements of 50 μM GA in pH 7 solutions. Interference studies indicate that some inorganic salts, catechol, caffeine and ascorbic acid do not interfere with the GA assay. The interference effects from some orthodiphenolic compounds are also investigated. The proposed method and a conventional Folin-Ciocalteu method are applied to detect GA in green tea samples using the standard addition method, and satisfactory spiked recoveries are obtained. Copyright © 2015 Elsevier B.V. All rights reserved.

  12. A simple, rapid and eco friendly method for determination of uranium in geological samples of low silicate matrix by ICP-OES

    International Nuclear Information System (INIS)

    Hanuman, V.V.; Chakrapani, G.; Singh, A.K.

    2013-01-01

    A simple, rapid, cost effective and eco friendly decomposition and dissolution method is developed for the determination of uranium (U 3 O 8 ) by Inductively Coupled Plasma - Optical Emission Spectrometer (ICP-OES) in low silicate geological samples. The salts of Sodium di-hydrogen phosphate monohydrate and Sodium pyrophosphate deca hydrate are used in the ratio of 1:1 (phosphate flux) for the decomposition of low silicate matrix geological samples. Samples are decomposed by fusion with the phosphate flux after ignition and the dissolution is carried out using distilled water. If the samples contain >10% silica, they have been treated with little amount of (HF+HNO 3 ) prior to fusion with phosphate flux. These samples, are analysed by ICP-OES directly without any separation from the matrix. The spectral interferences of major matrix elements (Al, Ti, Fe, Mn, etc present in the sample) on uranium are studied and it is observed that their interferences are negligible, as dilution is required to bring uranium concentration into calibration range of instrument. This is the first time, the phosphate flux is used for decomposition of low silicate geological samples for uranium determination by ICP-OES

  13. On Matrix Sampling and Imputation of Context Questionnaires with Implications for the Generation of Plausible Values in Large-Scale Assessments

    Science.gov (United States)

    Kaplan, David; Su, Dan

    2016-01-01

    This article presents findings on the consequences of matrix sampling of context questionnaires for the generation of plausible values in large-scale assessments. Three studies are conducted. Study 1 uses data from PISA 2012 to examine several different forms of missing data imputation within the chained equations framework: predictive mean…

  14. Characterizing the Effects of Washing by Different Detergents on the Wavelength-Scale Microstructures of Silk Samples Using Mueller Matrix Polarimetry.

    Science.gov (United States)

    Dong, Yang; He, Honghui; He, Chao; Zhou, Jialing; Zeng, Nan; Ma, Hui

    2016-08-10

    Silk fibers suffer from microstructural changes due to various external environmental conditions including daily washings. In this paper, we take the backscattering Mueller matrix images of silk samples for non-destructive and real-time quantitative characterization of the wavelength-scale microstructure and examination of the effects of washing by different detergents. The 2D images of the 16 Mueller matrix elements are reduced to the frequency distribution histograms (FDHs) whose central moments reveal the dominant structural features of the silk fibers. A group of new parameters are also proposed to characterize the wavelength-scale microstructural changes of the silk samples during the washing processes. Monte Carlo (MC) simulations are carried out to better understand how the Mueller matrix parameters are related to the wavelength-scale microstructure of silk fibers. The good agreement between experiments and simulations indicates that the Mueller matrix polarimetry and FDH based parameters can be used to quantitatively detect the wavelength-scale microstructural features of silk fibers. Mueller matrix polarimetry may be used as a powerful tool for non-destructive and in situ characterization of the wavelength-scale microstructures of silk based materials.

  15. Characterizing the Effects of Washing by Different Detergents on the Wavelength-Scale Microstructures of Silk Samples Using Mueller Matrix Polarimetry

    Directory of Open Access Journals (Sweden)

    Yang Dong

    2016-08-01

    Full Text Available Silk fibers suffer from microstructural changes due to various external environmental conditions including daily washings. In this paper, we take the backscattering Mueller matrix images of silk samples for non-destructive and real-time quantitative characterization of the wavelength-scale microstructure and examination of the effects of washing by different detergents. The 2D images of the 16 Mueller matrix elements are reduced to the frequency distribution histograms (FDHs whose central moments reveal the dominant structural features of the silk fibers. A group of new parameters are also proposed to characterize the wavelength-scale microstructural changes of the silk samples during the washing processes. Monte Carlo (MC simulations are carried out to better understand how the Mueller matrix parameters are related to the wavelength-scale microstructure of silk fibers. The good agreement between experiments and simulations indicates that the Mueller matrix polarimetry and FDH based parameters can be used to quantitatively detect the wavelength-scale microstructural features of silk fibers. Mueller matrix polarimetry may be used as a powerful tool for non-destructive and in situ characterization of the wavelength-scale microstructures of silk based materials.

  16. A novel electrochemical sensor based on magneto Au nanoparticles/carbon paste electrode for voltammetric determination of acetaminophen in real samples

    Energy Technology Data Exchange (ETDEWEB)

    Haghshenas, Esmaeel; Madrakian, Tayyebeh, E-mail: madrakian@basu.ac.ir; Afkhami, Abbas

    2015-12-01

    An electrochemical magneto Au nanoparticles/carbon paste electrodes (MAuNP/CPE) which is used for the determination of acetaminophen (AC) in real samples was developed. Initially, Au nanoparticles were immobilized at the surface of Fe{sub 3}O{sub 4} (AuNPs@Fe{sub 3}O{sub 4}), which was used as a sorbent for capturing AC molecules. After adding AuNPs@Fe{sub 3}O{sub 4} to the AC solution and stirring for 20 min, the AuNPs@Fe{sub 3}O{sub 4} was gathered on the magneto electrode based on its magnetic field. The AC molecules which became adsorbed at AuNPs@Fe{sub 3}O{sub 4} were analyzed by differential pulse voltammetry (DPV). For characterization and investigation of the performance of AuNPs@Fe{sub 3}O{sub 4} and MAuNPs/CPE, various methods, including scanning electron microscopy, X-ray diffraction, UV–Vis spectroscopy, electrochemical impedance spectroscopy, cyclic voltammetry and DPV were used. Under the optimized conditions, the anodic peak current was linear to the concentration of AC in the range of 0.1 to 70.0 μmol L{sup −1} with the detection limit of 4.5 × 10{sup −2} μmol L{sup −1}. This method was also successfully used to detect the concentration of AC in pharmaceutical formulations and human serum samples. In addition, the proposed magneto sensor exhibited good reproducibility, long-term stability and fast current response. - Highlights: • Magneto Au nanoparticle/carbon paste electrode was fabricated. • Au nanoparticles were immobilized at the surface of Fe{sub 3}O{sub 4} (AuNPs@Fe{sub 3}O{sub 4}). • It is the first time AuNPs@Fe{sub 3}O{sub 4} and magneto electrode are used for the determination of AC. • The proposed sensor showed a wide linear range, low detection limit, and high sensitivity. • This sensor is also used for the determination of AC in real samples.

  17. Mercapto-ordered carbohydrate-derived porous carbon electrode as a novel electrochemical sensor for simple and sensitive ultra-trace detection of omeprazole in biological samples

    Energy Technology Data Exchange (ETDEWEB)

    Kalate Bojdi, Majid [Department of Chemistry, Faculty of Science, Shahid Beheshti University, Tehran 1983963113 (Iran, Islamic Republic of); Faculty of Chemistry, Kharazmi (Tarbiat Moallem) University, Tehran (Iran, Islamic Republic of); Behbahani, Mohammad [Department of Chemistry, Faculty of Science, Shahid Beheshti University, Tehran 1983963113 (Iran, Islamic Republic of); Mashhadizadeh, Mohammad Hosein [Faculty of Chemistry, Kharazmi (Tarbiat Moallem) University, Tehran (Iran, Islamic Republic of); Bagheri, Akbar [Department of Chemistry, Faculty of Science, Shahid Beheshti University, Tehran 1983963113 (Iran, Islamic Republic of); Hosseiny Davarani, Saied Saeed, E-mail: ss-hosseiny@sbu.ac.ir [Department of Chemistry, Faculty of Science, Shahid Beheshti University, Tehran 1983963113 (Iran, Islamic Republic of); Farahani, Ali [Department of Chemistry, Faculty of Science, Shahid Beheshti University, Tehran 1983963113 (Iran, Islamic Republic of)

    2015-03-01

    We are introducing mercapto-mesoporous carbon modified carbon paste electrode (mercapto-MP-C-CPE) as a new sensor for trace determination of omeprazole (OM) in biological samples. The synthesized modifier was characterized by thermogravimetry analysis (TGA), differential thermal analysis (DTA), transmission electron microscopy (TEM), Fourier transform infrared spectrometry (FT-IR), X-ray diffraction (XRD), elemental analysis (CHN) and N{sub 2} adsorption surface area measurement (BET). The electrochemical response characteristic of the modified-CPE toward OM was investigated by cyclic and differential pulse voltammetry (CV and DPV). The proposed sensor displayed a good electrooxidation response to the OM, its linear range is 0.25 nM to 25 μM with a detection limit of 0.04 nM under the optimized conditions. The prepared modified electrode shows several advantages such as high sensitivity, long-time stability, wide linear range, ease of preparation and regeneration of the electrode surface by simple polishing and excellent reproducibility. - Highlights: • A modified nanoporous carbon as a novel sensor • High stability and good repeatability and reproducibility by the prepared sensor • Trace determination of omeprazole • Biological and pharmaceutical samples.

  18. Mercapto-ordered carbohydrate-derived porous carbon electrode as a novel electrochemical sensor for simple and sensitive ultra-trace detection of omeprazole in biological samples

    International Nuclear Information System (INIS)

    Kalate Bojdi, Majid; Behbahani, Mohammad; Mashhadizadeh, Mohammad Hosein; Bagheri, Akbar; Hosseiny Davarani, Saied Saeed; Farahani, Ali

    2015-01-01

    We are introducing mercapto-mesoporous carbon modified carbon paste electrode (mercapto-MP-C-CPE) as a new sensor for trace determination of omeprazole (OM) in biological samples. The synthesized modifier was characterized by thermogravimetry analysis (TGA), differential thermal analysis (DTA), transmission electron microscopy (TEM), Fourier transform infrared spectrometry (FT-IR), X-ray diffraction (XRD), elemental analysis (CHN) and N 2 adsorption surface area measurement (BET). The electrochemical response characteristic of the modified-CPE toward OM was investigated by cyclic and differential pulse voltammetry (CV and DPV). The proposed sensor displayed a good electrooxidation response to the OM, its linear range is 0.25 nM to 25 μM with a detection limit of 0.04 nM under the optimized conditions. The prepared modified electrode shows several advantages such as high sensitivity, long-time stability, wide linear range, ease of preparation and regeneration of the electrode surface by simple polishing and excellent reproducibility. - Highlights: • A modified nanoporous carbon as a novel sensor • High stability and good repeatability and reproducibility by the prepared sensor • Trace determination of omeprazole • Biological and pharmaceutical samples

  19. Matrix effect on the detection limit and accuracy in total reflection X-ray fluorescence analysis of trace elements in environmental and biological samples

    International Nuclear Information System (INIS)

    Karjou, J.

    2007-01-01

    The effect of matrix contents on the detection limit of total reflection X-ray fluorescence analysis was experimentally investigated using a set of multielement standard solutions (500 ng/mL of each element) in variable concentrations of NH 4 NO 3 . It was found that high matrix concentration, i.e. 0.1-10% NH 4 NO 3 , had a strong effect on the detection limits for all investigated elements, whereas no effect was observed at lower matrix concentration, i.e. 0-0.1% NH 4 NO 3 . The effect of soil and blood sample masses on the detection limit was also studied. The results showed decreasing the detection limit (in concentration unit, μg/g) with increasing the sample mass. However, the detection limit increased (in mass unit, ng) with increasing sample mass. The optimal blood sample mass of ca. 200 μg was sufficient to improve the detection limit of Se determination by total reflection X-ray fluorescence. The capability of total reflection X-ray fluorescence to analyze different kinds of samples was discussed with respect to the accuracy and detection limits based on certified and reference materials. Direct analysis of unknown water samples from several sources was also presented in this work

  20. Visualization and quantification of heterogeneous diffusion rates in granodiorite samples by X-ray absorption imaging. Diffusion within gouge materials, altered rim and intact rock matrix

    International Nuclear Information System (INIS)

    Altman, S.J.; Tidwell, V.C.; Uchida, M.

    2001-01-01

    Matrix diffusion is one of the most important contaminant migration retardation processes in crystalline rocks. Performance assessment calculations in various countries assume that only the area of the fracture surface where advection is active provides access to the rock matrix. However, accessibility to the matrix could be significantly enhanced with diffusion into stagnant zones, fracture fillings, and through an alteration rim in the matrix. Laboratory visualization experiments were conducted on granodiorite samples to investigate and quantify diffusion rates within different zones of a Cretaceous granodiorite. Samples were collected from the Kamaishi experimental site in the northern part of the main island of Japan. Diffusion of iodine out of the sample is visualized and rates are measured using x-ray absorption imaging. X-ray images allow for measurements of relative iodine concentration and relative iodine mass as a function of time and two-dimensional space at a sub-millimeter spatial resolution. In addition, two-dimensional heterogeneous porosity fields (at the same resolution as the relative concentration fields) are measured. This imaging technique allows for a greater understanding of the spatial variability of diffusion rates than can be accomplished with standard bulk measurements. It was found that diffusion rates were fastest in partially gouge-filled fractures. Diffusion rates in the recrystallized calcite-based fracture-filling material were up to an order of magnitude lower than in gouge-filled fractures. Diffusion in altered matrix around the fractures was over an order of magnitude lower than that in the gouge-filled fractures. Healed fractures did not appear to have different diffusion rates than the unaltered matrix

  1. Visualization and quantification of heterogeneous diffusion rates in granodiorite samples by X-ray absorption imaging. Diffusion within gouge materials, altered rim and intact rock matrix

    Energy Technology Data Exchange (ETDEWEB)

    Altman, S.J.; Tidwell, V.C. [Sandia National Laboratories, Albuquerque, NM (United States); Uchida, M. [Japan Nuclear Cycle Development Inst., Ibaraki (Japan)

    2001-08-01

    Matrix diffusion is one of the most important contaminant migration retardation processes in crystalline rocks. Performance assessment calculations in various countries assume that only the area of the fracture surface where advection is active provides access to the rock matrix. However, accessibility to the matrix could be significantly enhanced with diffusion into stagnant zones, fracture fillings, and through an alteration rim in the matrix. Laboratory visualization experiments were conducted on granodiorite samples to investigate and quantify diffusion rates within different zones of a Cretaceous granodiorite. Samples were collected from the Kamaishi experimental site in the northern part of the main island of Japan. Diffusion of iodine out of the sample is visualized and rates are measured using x-ray absorption imaging. X-ray images allow for measurements of relative iodine concentration and relative iodine mass as a function of time and two-dimensional space at a sub-millimeter spatial resolution. In addition, two-dimensional heterogeneous porosity fields (at the same resolution as the relative concentration fields) are measured. This imaging technique allows for a greater understanding of the spatial variability of diffusion rates than can be accomplished with standard bulk measurements. It was found that diffusion rates were fastest in partially gouge-filled fractures. Diffusion rates in the recrystallized calcite-based fracture-filling material were up to an order of magnitude lower than in gouge-filled fractures. Diffusion in altered matrix around the fractures was over an order of magnitude lower than that in the gouge-filled fractures. Healed fractures did not appear to have different diffusion rates than the unaltered matrix.

  2. Simultaneous determination of iodide and iodate in soil solution samples by HPLC with electrochemical detection and post-column reaction method

    Energy Technology Data Exchange (ETDEWEB)

    Takeda, Akira; Takaku, Yuichi; Hisamatsu, Shun' ichi [Department of Radioecology, Institute for Environmental Sciences, Aomori 039-3212 (Japan); Tsukada, Hirofumi [Department of Radioecology, Institute for Environmental Sciences, Aomori 039-3212 (Japan); Institute of Environmental Radioactivity, Fukushima University, Fukushima 960-1196 (Japan)

    2014-07-01

    Iodine-129 (half-life 1.6 x 10{sup 7} y) discharged into the atmosphere from nuclear facilities (e.g., a nuclear fuel reprocessing plant) is partly deposited on land and introduced into soil. Stable iodine ({sup 127}I) can be used as a natural analogue to predict the long-term behavior of {sup 129}I in the terrestrial environment. Iodine in soil mainly exists as I{sup -}, IO{sub 3}{sup -}, and organic iodine. Because the mobilities of these species in soil are quite different, iodine speciation in soil solution is a key for predicting the behavior of iodine in soil. We developed a new speciation method suitable for routine analysis of many soil solution samples, and successfully applied the method to real samples. The method involves determining the concentration of total iodine and then separately measuring the I{sup -} and IO{sub 3}{sup -} concentrations with an HPLC system. The HPLC system (Nano-space SI-2; Shiseido, Tokyo, Japan) consisted of a UV/Vis spectrometer and an electrochemical (amperometric) detector (50 mV Ag/AgCl). Two reverse-phase columns (2.0 x 50 mm Capcel Pak DD C8 and 2.0 x 250 mm Capcel Pak MGII C18; Shiseido) were serially connected, and a switching valve was set between them. I{sup -} and IO{sub 3}{sup -} in the sample solution were separated from each other in the DD C8 column. IO{sub 3}{sup -} eluted first from the column, while I{sup -} was retained. After IO{sub 3}{sup -} was further separated from other halogen acids with the C18 column, IO{sub 3}{sup -} was reacted with KBr and o-dianisidine in a thermos-reactor (90 deg. C), and absorption at 450 nm was measured with the UV/Vis spectrometer. The concentration of I{sup -} eluted from the first column was determined with the electrochemical detector. To determine the concentration of total iodine in the sample solution, organic iodine was decomposed by UV irradiation (UV digester 705; Metrohm AG, Herisau, Switzerland) for 30 min at 20 deg. C. The iodine in the solution was reduced to I

  3. Design and development of electrochemical polymer-based lab-on-a-disc devices for biological applications

    DEFF Research Database (Denmark)

    Sanger, Kuldeep

    of pHCA. The second generation LoD device (with integrated SLM extraction) was more advanced and facilitated extraction, enrichment, as well as electrochemical detection of pHCA from the complex sample matrix, i.e., E. coli supernatant at different time points during the cell culture. Realizing......The need for reliable, fast, easy to use, portable and cost effective analytical tools has led to several novel approaches in the development of miniaturized microfluidic platforms integrated with electrochemical sensors. This thesis presents the design and development of an electrochemical...... filtration) was used to quantify pHCA at the end of bacterial culture (24 hours) when the cell density is the highest. We demonstrated the efficiency of the centrifugal filtration, which enabled cell-free electrochemical detection eliminating the effect of high cell density on electrochemical quantification...

  4. Independent assessment of matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) sample preparation quality: Effect of sample preparation on MALDI-MS of synthetic polymers.

    Science.gov (United States)

    Kooijman, Pieter C; Kok, Sander; Honing, Maarten

    2017-02-28

    Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) provides detailed and in-depth information about the molecular characteristics of synthetic polymers. To obtain the most accurate results the sample preparation parameters should be chosen to suit the sample and the aim of the experiment. Because the underlying principles of MALDI are still not fully known, a priori determination of optimal sample preparation protocols is often not possible. Employing an automated sample preparation quality assessment method recently presented by us we quantified the sample preparation quality obtained using various sample preparation protocols. Six conventional matrices with and without added potassium as a cationization agent and six ionic liquid matrices (ILMs) were assessed using poly(ethylene glycol) (PEG), polytetrahydrofuran (PTHF) and poly(methyl methacrylate) (PMMA) as samples. All sample preparation protocols were scored and ranked based on predefined quality parameters and spot-to-spot repeatability. Clearly distinctive preferences were observed in matrix identity and cationization agent for PEG, PTHF and PMMA, as the addition of an excess of potassium cationization agent results in an increased score for PMMA and a contrasting matrix-dependent effect for PTHF and PEG. The addition of excess cationization agent to sample mixtures dissipates any overrepresentation of high molecular weight polymer species. Our results show reduced ionization efficiency and similar sample deposit homogeneity for all tested ILMs, compared with well-performing conventional MALDI matrices. The results published here represent a start in the unsupervised quantification of sample preparation quality for MALDI samples. This method can select the best sample preparation parameters for any synthetic polymer sample and the results can be used to formulate hypotheses on MALDI principles. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  5. Fluorescence imaging of sample zone narrowing and dispersion in a glass microchip: the effects of organic solvent (acetonitrile)-salt mixtures in the sample matrix and surfactant micelles in the running buffer.

    Science.gov (United States)

    Jia, Zhijian; Lee, Yi-kuen; Fang, Qun; Huie, Carmen W

    2006-03-01

    A mismatch in the EOF velocities between the sample zone and running buffer region is known to generate pressure-driven, parabolic flow profile of the sample plug in electrokinetic separation systems. In the present study, video fluorescence microscopy was employed to capture real-time dynamics of the sample plug (containing fluorescein as the probe molecule) in a discontinuous conductivity system within a glass microchip, in which the sample matrix consisted of a mixture of ACN and salt (NaCl), and the running buffer contained sodium cholate (SC) micelles as the pseudo-stationary phase (i.e., performing "ACN stacking" in the mode of MEKC). Upon application of the separation voltage, the video images revealed that zone narrowing and broadening of the probe molecules occurred as the sample plug headed toward the cathode during the initial time period, probably resulting in part from the stacking/sweeping, and destacking of the SC micelles at the boundaries between the sample zone and running buffer. Interestingly, a second sample zone narrowing event can be observed as the sample plug moved further toward the cathode, which could be attributed to the sweeping of the slower moving probe molecules by the faster moving SC micelles that originated from the anode. This phenomenon was studied as a function of pH, sample plug length, as well as the concentration of organic solvent and salt in the sample matrix. The data suggested that the presence of large amounts of an organic solvent (such as ACN or methanol) and salts in the sample matrix not only induces sample dispersion due to the formation of a pressure-driven (hydrodynamic) flow, but may also lead to the formation of a double sample zone narrowing phenomenon by altering the local EOF dynamics within the separation system.

  6. Electrochemical biosensors

    CERN Document Server

    Cosnier, Serge

    2015-01-01

    "This is an excellent book on modern electrochemical biosensors, edited by Professor Cosnier and written by leading international experts. It covers state-of-the-art topics of this important field in a clear and timely manner."-Prof. Joseph Wang, UC San Diego, USA  "This book covers, in 13 well-illustrated chapters, the potential of electrochemical methods intimately combined with a biological component for the assay of various analytes of biological and environmental interest. Particular attention is devoted to the description of electrochemical microtools in close contact with a biological cell for exocytosis monitoring and to the use of nanomaterials in the electrochemical biosensor architecture for signal improvement. Interestingly, one chapter describes the concept and design of self-powered biosensors derived from biofuel cells. Each topic is reviewed by experts very active in the field. This timely book is well suited for providing a good overview of current research trends devoted to electrochemical...

  7. Electrochemical determination of the levels of cadmium, copper and lead in polluted soil and plant samples from mining areas in Zamfara State, Nigeria

    Directory of Open Access Journals (Sweden)

    Modupe Mabel Ogunlesi

    2017-12-01

    Full Text Available The concentrations of lead, copper and cadmium in soil and plant samples collected from Abare and Dareta villages in Anka local government area of Zamfara State, Nigeria have been electrochemically determined. The study was carried out because of the high mortality of women and children under five, reported for these areas in June 2010. The cause was ascribed to the lead poisoning which has been related to the mining and processing of gold-containing ores. Linear sweep anodic stripping voltammetry technique was used with the glassy carbon working, Ag/AgCl reference and platinum auxiliary electrodes. Voltammetric peaks for lead, copper and cadmium that were observed at -495 mV, -19.4 mV and -675 mV, respectively, have formed a basis for construction of the corresponding calibration plots. The concentrations (in mg/kg of lead, copper and cadmium in the soil samples were found in the ranges of 18.99−26087.70, 2.96−584.60 and 0.00−1354.25, respectively. The concentration values for lead were far above already established USEPA (2002 and WHO (1996 maximum permissible limits for residential areas. The concentrations of lead, copper and cadmium in the food samples ranged between 5.70−79.91, 11.17−41.21 and 0.00−5.74 mg/kg. Several of these values are found well above the FAO/WHO limits of 0.1, 2 and 0.1 mg/kg, respectively. The results indicate that in addition to the lead poisoning, copper and cadmium poisoning may also be responsible for sudden and high mortality in this population.

  8. Independent assessment of matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) sample preparation quality: A novel statistical approach for quality scoring.

    Science.gov (United States)

    Kooijman, Pieter C; Kok, Sander J; Weusten, Jos J A M; Honing, Maarten

    2016-05-05

    Preparation of samples according to an optimized method is crucial for accurate determination of polymer sample characteristics by Matrix-Assisted Laser Desorption Ionization (MALDI) analysis. Sample preparation conditions such as matrix choice, cationization agent, deposition technique or even the deposition volume should be chosen to suit the sample of interest. Many sample preparation protocols have been developed and employed, yet finding the optimal sample preparation protocol remains a challenge. Because an objective comparison between the results of diverse protocols is not possible, "gut-feeling" or "good enough" is often decisive in the search for an optimum. This implies that sub-optimal protocols are used, leading to a loss of mass spectral information quality. To address this problem a novel analytical strategy based on MALDI imaging and statistical data processing was developed in which eight parameters were formulated to objectively quantify the quality of sample deposition and optimal MALDI matrix composition and finally sum up to an overall quality score of the sample deposition. These parameters can be established in a fully automated way using commercially available mass spectrometry imaging instruments without any hardware adjustments. With the newly developed analytical strategy the highest quality MALDI spots were selected, resulting in more reproducible and more valuable spectra for PEG in a variety of matrices. Moreover, our method enables an objective comparison of sample preparation protocols for any analyte and opens up new fields of investigation by presenting MALDI performance data in a clear and concise way. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Mercapto-ordered carbohydrate-derived porous carbon electrode as a novel electrochemical sensor for simple and sensitive ultra-trace detection of omeprazole in biological samples.

    Science.gov (United States)

    Kalate Bojdi, Majid; Behbahani, Mohammad; Mashhadizadeh, Mohammad Hosein; Bagheri, Akbar; Hosseiny Davarani, Saied Saeed; Farahani, Ali

    2015-03-01

    We are introducing mercapto-mesoporous carbon modified carbon paste electrode (mercapto-MP-C-CPE) as a new sensor for trace determination of omeprazole (OM) in biological samples. The synthesized modifier was characterized by thermogravimetry analysis (TGA), differential thermal analysis (DTA), transmission electron microscopy (TEM), Fourier transform infrared spectrometry (FT-IR), X-ray diffraction (XRD), elemental analysis (CHN) and N2 adsorption surface area measurement (BET). The electrochemical response characteristic of the modified-CPE toward OM was investigated by cyclic and differential pulse voltammetry (CV and DPV). The proposed sensor displayed a good electrooxidation response to the OM, its linear range is 0.25nM to 25μM with a detection limit of 0.04nM under the optimized conditions. The prepared modified electrode shows several advantages such as high sensitivity, long-time stability, wide linear range, ease of preparation and regeneration of the electrode surface by simple polishing and excellent reproducibility. Copyright © 2014 Elsevier B.V. All rights reserved.

  10. An electrochemical sensor for rizatriptan benzoate determination using Fe3O4 nanoparticle/multiwall carbon nanotube-modified glassy carbon electrode in real samples.

    Science.gov (United States)

    Madrakian, Tayyebeh; Maleki, Somayeh; Heidari, Mozhgan; Afkhami, Abbas

    2016-06-01

    In this paper a sensitive and selective electrochemical sensor for determination of rizatriptan benzoate (RZB) was proposed. A glassy carbon electrode was modified with nanocomposite of multiwalled carbon nanotubes (MWCNTs) and Fe3O4 nanoparticles (Fe3O4/MWCNTs/GCE). The results obtained clearly show that the combination of MWCNTs and Fe3O4 nanoparticles definitely improves the sensitivity of modified electrode to RZB determination. The morphology and electroanalytical performance of the fabricated sensor were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), square wave voltammetry (SWV) and cyclic voltammetry (CV). Also, the effect of experimental and instrumental parameters on the sensor response was evaluated. The square wave voltammetric response of the electrode to RZB was linear in the range 0.5-100.0 μmol L(-1) with a detection limit of 0.09 μmol L(-1) under the optimum conditions. The investigated method showed good stability, reproducibility and repeatability. The proposed sensor was successfully applied for real life samples of blood serum and RZB determination in pharmaceutical. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. Heteroatom-enriched and renewable banana-stem-derived porous carbon for the electrochemical determination of nitrite in various water samples

    Science.gov (United States)

    Madhu, Rajesh; Veeramani, Vediyappan; Chen, Shen-Ming

    2014-04-01

    For the first time, high-surface-area (approximately 1465 m2 g-1), highly porous and heteroatom-enriched activated carbon (HAC) was prepared from banana stems (Musa paradisiaca, Family: Musaceae) at different carbonization temperatures of 700, 800 and 900°C (HAC) using a simple and eco-friendly method. The amounts of carbon, hydrogen, nitrogen and sulfur in the HAC are 61.12, 2.567, 0.4315, and 0.349%, respectively. Using X-ray diffraction (XRD), CHNS elemental analysis, X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy, the prepared activated carbon appears amorphous and disordered in nature. Here, we used HAC for an electrochemical application of nitrite (NO2-) sensor to control the environmental pollution. In addition, HAC exhibits noteworthy performance for the highly sensitive determination of nitrite. The limit of detection (LODs) of the nitrite sensor at HAC-modified GCE is 0.07 μM. In addition, the proposed method was applied to determine nitrite in various water samples with acceptable results.

  12. A new and efficient Solid Phase Microextraction approach for analysis of high fat content food samples using a matrix-compatible coating.

    Science.gov (United States)

    De Grazia, Selenia; Gionfriddo, Emanuela; Pawliszyn, Janusz

    2017-05-15

    The current work presents the optimization of a protocol enabling direct extraction of avocado samples by a new Solid Phase Microextraction matrix compatible coating. In order to further extend the coating life time, pre-desorption and post-desorption washing steps were optimized for solvent type, time, and degree of agitation employed. Using optimized conditions, lifetime profiles of the coating related to extraction of a group of analytes bearing different physical-chemical properties were obtained. Over 80 successive extractions were carried out to establish coating efficiency using PDMS/DVB 65µm commercial coating in comparison with the PDMS/DVB/PDMS. The PDMS/DVB coating was more prone to irreversible matrix attachment on its surface, with consequent reduction of its extractive performance after 80 consecutive extractions. Conversely, the PDMS/DVB/PDMS coating showed enhanced inertness towards matrix fouling due to its outer smooth PDMS layer. This work represents the first step towards the development of robust SPME methods for quantification of contaminants in avocado as well as other fatty-based matrices, with minimal sample pre-treatment prior to extraction. In addition, an evaluation of matrix components attachment on the coating surface and related artifacts created by desorption of the coating at high temperatures in the GC-injector port, has been performed by GCxGC-ToF/MS. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Clay matrix voltammetry

    International Nuclear Information System (INIS)

    Perdicakis, Michel

    2012-01-01

    Document available in extended abstract form only. In many countries, it is planned that the long life highly radioactive nuclear spent fuel will be stored in deep argillaceous rocks. The sites selected for this purpose are anoxic and satisfy several recommendations as mechanical stability, low permeability and low redox potential. Pyrite (FeS 2 ), iron(II) carbonate, iron(II) bearing clays and organic matter that are present in very small amounts (about 1% w:w) in soils play a major role in their reactivity and are considered today as responsible for the low redox potential values of these sites. In this communication, we describe an electrochemical technique derived from 'Salt matrix voltammetry' and allowing the almost in-situ voltammetric characterization of air-sensitive samples of soils after the only addition of the minimum humidity required for electrolytic conduction. Figure 1 shows the principle of the developed technique. It consists in the entrapment of the clay sample between a graphite working electrode and a silver counter/quasi-reference electrode. The sample was previously humidified by passing a water saturated inert gas through the electrochemical cell. The technique leads to well-defined voltammetric responses of the electro-active components of the clays. Figure 2 shows a typical voltammogram relative to a Callovo-Oxfordian argillite sample from Bure, the French place planned for the underground nuclear waste disposal. During the direct scan, one can clearly distinguish the anodic voltammetric signals for the oxidation of the iron (II) species associated with the clay and the oxidation of pyrite. The reverse scan displays a small cathodic signal for the reduction of iron (III) associated with the clay that demonstrates that the majority of the previously oxidized iron (II) species were transformed into iron (III) oxides reducible at lower potentials. When a second voltammetric cycle is performed, one can notice that the signal for iron (II

  14. Simultaneous determination of levodopa, carbidopa and tryptophan using nanostructured electrochemical sensor based on novel hydroquinone and carbon nanotubes: Application to the analysis of some real samples

    International Nuclear Information System (INIS)

    Mazloum-Ardakani, Mohammad; Ganjipour, Bahram; Beitollahi, Hadi; Amini, Mohammad Kazem; Mirkhalaf, Fakhradin; Naeimi, Hossein; Nejati-Barzoki, Maryam

    2011-01-01

    Highlights: → A novel hydroquinone-carbon nanotube paste electrode have been fabricated. → This electrode reduced the oxidation potential of levodopa by about 460 mV. → Some kinetic parameters for oxidation of levodopa has been determined. → This electrode resolved the voltammetric waves of levodopa, carbidopa and tryptophan. → This electrode used for determination of levodopa in some real samples. - Abstract: In the present paper, the use of a novel carbon paste electrode modified by 2, 2'-[1,2-ethanediylbis (nitriloethylidyne)]-bis-hydroquinone (EBNBH) and carbon nanotubes prepared by a simple and rapid method for the determination of levodopa (LD), carbidopa (CD) and tryptophan (Trp) was described. In the first part of the work, cyclic voltammetry was used to investigate the redox properties of this modified electrode at various scan rates. The apparent charge-transfer rate constant, k s , and transfer coefficient, α, for electron transfer between EBNBH and carbon nanotube paste electrode were calculated. In the second part of the work, the mediated oxidation of LD at the modified electrode was described. It has been found that under optimum condition (pH 7.0) in cyclic voltammetry, the oxidation of LD occurs at a potential about 460 mV less positive than that of an unmodified carbon paste electrode. The values of electron transfer coefficient (α), catalytic rate constant (k h ') and diffusion coefficient (D) were calculated for LD, using electrochemical approaches. Differential pulse voltammetry (DPV) exhibited two linear dynamic ranges and a detection limit (3σ) of 0.094 μM for LD. In the third part of the work, simultaneous determination of LD, CD and Trp at the modified electrode was described. Finally, this method was used for the determination of LD in some real samples, using standard addition method.

  15. Optimization of the sample dilution for minimization of the matrix effects and achieving maximal sensitivity in XRFA

    International Nuclear Information System (INIS)

    Dimov, L.; Benova, M.

    1989-01-01

    The method of neutral medium dilution can lead to practically full leveling of the matrix but the high degree of dilution at which this effect is achieved will inevitably result in loss of sensitivity. In the XRFA of heavy elements in a light matrix the dependence of the fluorescence intensity upon concentration is characterized by gradually decreasing steepness reacting saturation (as in analysis of Pb in a Pb-concentrate). The dilution by neutral medium can shift the concentration range to a zone of greater steepness but this results in an increase of sensitivity towards the concentration in the initial (undiluted) material only to a certain degree of dilution. This work presents an optimization of the degree of dilution by neutral medium which achieves a sufficient leveling of the matrix when using different materials and also maximal sensitivity towards higher concentrations. Furthermore an original solution is found to the problem of selecting a neutral medium enabling to achieve good homogenization with various materials and particularly - with marble flour. (author)

  16. Electrochemical Processes

    DEFF Research Database (Denmark)

    Bech-Nielsen, Gregers

    1997-01-01

    The notes describe in detail primary and secondary galvanic cells, fuel cells, electrochemical synthesis and electroplating processes, corrosion: measurments, inhibitors, cathodic and anodic protection, details of metal dissolution reactions, Pourbaix diagrams and purification of waste water from...

  17. Electrochemical analysis

    International Nuclear Information System (INIS)

    Hwang, Hun

    2007-02-01

    This book explains potentiometry, voltametry, amperometry and basic conception of conductometry with eleven chapters. It gives the specific descriptions on electrochemical cell and its mode, basic conception of electrochemical analysis on oxidation-reduction reaction, standard electrode potential, formal potential, faradaic current and faradaic process, mass transfer and overvoltage, potentiometry and indirect potentiometry, polarography with TAST, normal pulse and deferential pulse, voltammetry, conductometry and conductometric titration.

  18. Electrochemical Behavior of Catechol and Hydroquinone at Copper Doped Poly (Methyl Red Coated Hydroxyl Multiwalled Carbon Nanotube Film and Their Simultaneous Determination in Water Samples

    Directory of Open Access Journals (Sweden)

    Ying Zhang

    2014-09-01

    Full Text Available A glassy carbon electrode modified with copper doped poly (methyl red coated hydroxyl multiwalled carbon nanotube film (Cu-PMR/MWCNTs, was developed to serve as a sensor for simultaneous determination of Hydroquinone (HQ and catechol (CC in this paper. The fabricated electrode showed excellent electrocatalytic behaviors towards the oxidation of HQ and CC with the enhancement of the redox peak current and the decrease of the peak-to-peak separation. Under the optimized condition, the individual determination of HQ or CT in their mixtures was performed, the response peak currents of the modified electrodes were linear over ranges of 8.0´10-7~4.0´10-4 M (R2=0.999 for CT and 5.0´10-7~2.0´10-4 M (R2=0.993 for HQ. The sensor also exhibited good sensitivity with the detection limit of 1.0´10-8 mol/L and 5.0´10-8 mol/L for HQ and CT, respectively. The simultaneous determination of HQ and CC was demonstrated by simultaneously changing their concentrations. The reduction peak currents of HQ and CC increased linearly with the concentration of their own in the range of 8´10-7 and 2.0´10-4 M for HQ and CC, with correlation coefficients of 0.994 and 0.995 (S/N=3, respectively. This study provides a new kind of composite modified electrode for electrochemical sensors with good selectivity and strong anti-interference. It has been applied to simultaneous determination of HQ and CT in water sample with high selectivity.

  19. In situ liquid-liquid extraction as a sample preparation method for matrix-assisted laser desorption/ionization MS analysis of polypeptide mixtures

    DEFF Research Database (Denmark)

    Kjellström, Sven; Jensen, Ole Nørregaard

    2003-01-01

    A novel liquid-liquid extraction (LLE) procedure was investigated for preparation of peptide and protein samples for matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS). LLE using ethyl acetate as the water-immiscible organic solvent enabled segregation of hydrophobic...... matrix to the organic solvent enhanced the efficiency of the LLE-MALDI MS method for analysis of hydrophobic peptides and proteins. LLE-MALDI MS enabled the detection of the hydrophobic membrane protein bacteriorhodopsin as a component in a simple protein mixture. Peptide mixtures containing...... phosphorylated, glycosylated, or acylated peptides were successfully separated and analyzed by the in situ LLE-MALDI MS technique and demonstrate the potential of this method for enhanced separation and structural analysis of posttranslationally modified peptides in proteomics research....

  20. Determination of As, Cd, and Pb in Tap Water and Bottled Water Samples by Using Optimized GFAAS System with Pd-Mg and Ni as Matrix Modifiers

    Directory of Open Access Journals (Sweden)

    Sezgin Bakırdere

    2013-01-01

    Full Text Available Arsenic, lead, and cadmium were determined in tap and bottled water samples consumed in the west part of Turkey at trace levels. Graphite furnace atomic absorption spectrometry (GFAAS was used in all detections. All of the system parameters for each element were optimized to increase sensitivity. Pd-Mg mixture was selected as the best matrix modifier for As, while the highest signals were obtained for Pb and Cd in the case of Ni used as matrix modifier. Detection limits for As, Cd, and Pb were found to be 2.0, 0.036, and 0.25 ng/mL, respectively. 78 tap water and 17 different brands of bottled water samples were analyzed for their As, Cd, and Pb contents under the optimized conditions. In all water samples, concentration of cadmium was found to be lower than detection limits. Lead concentration in the samples analyzed varied between N.D. and 12.66 ± 0.68 ng/mL. The highest concentration of arsenic was determined as 11.54 ± 2.79 ng/mL. Accuracy of the methods was verified by using a certified reference material, namely, Trace Element in Water, 1643e. Results found for As, Cd, and Pb in reference materials were in satisfactory agreement with the certified values.

  1. Summary of micrographic analysis of selected core samples from Well ER-20-6n number 1 in support of matrix diffusion testing

    International Nuclear Information System (INIS)

    1998-01-01

    ER-20-6number s ign1 was cored to determine fracture and lithologic properties proximal to the BULLION test cavity. Selected samples from ER-20-6number s ign1 were subjected to matrix and/or fracture diffusion experiments to assess solute movement in this environment. Micrographic analysis of these samples suggests that the similarity in bulk chemical composition results in very similar mineral assemblages forming along natural fractures. These samples are all part of the mafic-poor Calico Hills Formation and exhibit fracture-coating mineral assemblages dominated by mixed illite/smectite clay and illite, with local opaline silica (2,236 and 2, 812 feet), and zeolite (at 2,236 feet). Based on this small sample population, the magnitude to which secondary phases have formed on fracture surfaces bears an apparently inverse relationship to the competency of the host lithology, reflected by variations in the degree of fracturing and the development of secondary phases on fracture surfaces. In the flow breccia at 2,851 feet, thinly developed, localized coatings are developed along persistent open fracture apertures in this competent rock type. Fractures in the devitrified lava from 2,812 feet are irregular, and locally blocked by secondary mineral phases. Natural fractures on the zeolitized tuff from 2,236 feet are discontinuous and irregular and typically obstructed with secondary mineral phases. There are also a second set of clean fractures in the 2,236 foot sample which lack secondary mineral phases and are interpreted to have been induced by the BULLION test. Based on these results, it is expected that matrix diffusion will be enhanced in samples where potentially transmissive fractures exhibit the greatest degree of obstruction (2,236>2,812=2,835>2,851). It is unclear what influence the induced fractures observed at 2,236 feet may have on diffusion given the lack of knowledge on their extent. It is assumed that the bulk matrix diffusion characteristics of the

  2. Electrochemical impedance spectroscopy for analytical determination of paraquat in meconium samples using an immunosensor modified with fullerene, ferrocene and ionic liquid

    Energy Technology Data Exchange (ETDEWEB)

    Sun Xiulan [State Key Laboratory of Food Science and Technology, Wuxi 214122 (China); Li Zaijun, E-mail: zaijunli@263.ne [School of Chemical and Materials Engineering, Jiangnan University, Lihu Road 1800, Wuxi 214122 (China); Cai, Yan; Wei, Zhilei [School of Chemical and Materials Engineering, Jiangnan University, Lihu Road 1800, Wuxi 214122 (China); Fang Yinjun; Ren Guoxiao; Huang Yaru [Zhejiang Zanyu Technology Limited Corporation, Hangzhou 311215 (China)

    2011-01-01

    The paper reports a highly sensitive electrochemical immunosensor for the detection of paraquat. The immunosensor bases on glassy carbon electrode modified with a composite made from fullerene, ferrocene and the ionic liquid. The components were immobilized on the electrode surface by chitosan. The antibody of paraquat was covalently conjugated to the surface which was then blocked with bovine serum albumin. Analytical characteristics of the immunosensor were investigated by electrochemical impedance spectroscopy. It offers good repeatability (RSD = 1.5%), a stability of more than 150 days, an impedimetric response to paraquat in the range from 3.89 x 10{sup -11} to 4.0 x 10{sup -8} mol L{sup -1}, and a detection limit (S/N = 3) of 9.0 x 10{sup -12} mol L{sup -1}. The effects of omitting fullerene and the ionic liquid were well tested. The results indicated that sensitivity of the immunosensor is 3.7-fold better if fullerene and ionic liquid are used. This demonstrates that fullerene facilitates electron transfer on surface of the electrode due to unique electrochemical properties, while the ionic liquid provides biocompatible microenvironment for the antibody, which results in the enhanced sensitivity and stability. Moreover, surface morphology feature and electrochemical properties of the electrode were also examined. The method was satisfactorily applied to the determination of paraquat in meconium.

  3. Sampling

    CERN Document Server

    Thompson, Steven K

    2012-01-01

    Praise for the Second Edition "This book has never had a competitor. It is the only book that takes a broad approach to sampling . . . any good personal statistics library should include a copy of this book." —Technometrics "Well-written . . . an excellent book on an important subject. Highly recommended." —Choice "An ideal reference for scientific researchers and other professionals who use sampling." —Zentralblatt Math Features new developments in the field combined with all aspects of obtaining, interpreting, and using sample data Sampling provides an up-to-date treat

  4. Condenser: a statistical aggregation tool for multi-sample quantitative proteomic data from Matrix Science Mascot Distiller™.

    Science.gov (United States)

    Knudsen, Anders Dahl; Bennike, Tue; Kjeldal, Henrik; Birkelund, Svend; Otzen, Daniel Erik; Stensballe, Allan

    2014-05-30

    We describe Condenser, a freely available, comprehensive open-source tool for merging multidimensional quantitative proteomics data from the Matrix Science Mascot Distiller Quantitation Toolbox into a common format ready for subsequent bioinformatic analysis. A number of different relative quantitation technologies, such as metabolic (15)N and amino acid stable isotope incorporation, label-free and chemical-label quantitation are supported. The program features multiple options for curative filtering of the quantified peptides, allowing the user to choose data quality thresholds appropriate for the current dataset, and ensure the quality of the calculated relative protein abundances. Condenser also features optional global normalization, peptide outlier removal, multiple testing and calculation of t-test statistics for highlighting and evaluating proteins with significantly altered relative protein abundances. Condenser provides an attractive addition to the gold-standard quantitative workflow of Mascot Distiller, allowing easy handling of larger multi-dimensional experiments. Source code, binaries, test data set and documentation are available at http://condenser.googlecode.com/. Copyright © 2014 Elsevier B.V. All rights reserved.

  5. Implementation of electrochemical, optical and denuder-based sensors and sampling techniques on UAV for volcanic gas measurements: examples from Masaya, Turrialba and Stromboli volcanoes

    Science.gov (United States)

    Rüdiger, Julian; Tirpitz, Jan-Lukas; Maarten de Moor, J.; Bobrowski, Nicole; Gutmann, Alexandra; Liuzzo, Marco; Ibarra, Martha; Hoffmann, Thorsten

    2018-04-01

    Volcanoes are a natural source of several reactive gases (e.g., sulfur and halogen containing species) and nonreactive gases (e.g., carbon dioxide) to the atmosphere. The relative abundance of carbon and sulfur in volcanic gas as well as the total sulfur dioxide emission rate from a volcanic vent are established parameters in current volcano-monitoring strategies, and they oftentimes allow insights into subsurface processes. However, chemical reactions involving halogens are thought to have local to regional impact on the atmospheric chemistry around passively degassing volcanoes. In this study we demonstrate the successful deployment of a multirotor UAV (quadcopter) system with custom-made lightweight payloads for the compositional analysis and gas flux estimation of volcanic plumes. The various applications and their potential are presented and discussed in example studies at three volcanoes encompassing flight heights of 450 to 3300 m and various states of volcanic activity. Field applications were performed at Stromboli volcano (Italy), Turrialba volcano (Costa Rica) and Masaya volcano (Nicaragua). Two in situ gas-measuring systems adapted for autonomous airborne measurements, based on electrochemical and optical detection principles, as well as an airborne sampling unit, are introduced. We show volcanic gas composition results including abundances of CO2, SO2 and halogen species. The new instrumental setups were compared with established instruments during ground-based measurements at Masaya volcano, which resulted in CO2 / SO2 ratios of 3.6 ± 0.4. For total SO2 flux estimations a small differential optical absorption spectroscopy (DOAS) system measured SO2 column amounts on transversal flights below the plume at Turrialba volcano, giving 1776 ± 1108 T d-1 and 1616 ± 1007 T d-1 of SO2 during two traverses. At Stromboli volcano, elevated CO2 / SO2 ratios were observed at spatial and temporal proximity to explosions by airborne in situ measurements. Reactive

  6. Implementation of electrochemical, optical and denuder-based sensors and sampling techniques on UAV for volcanic gas measurements: examples from Masaya, Turrialba and Stromboli volcanoes

    Directory of Open Access Journals (Sweden)

    J. Rüdiger

    2018-04-01

    Full Text Available Volcanoes are a natural source of several reactive gases (e.g., sulfur and halogen containing species and nonreactive gases (e.g., carbon dioxide to the atmosphere. The relative abundance of carbon and sulfur in volcanic gas as well as the total sulfur dioxide emission rate from a volcanic vent are established parameters in current volcano-monitoring strategies, and they oftentimes allow insights into subsurface processes. However, chemical reactions involving halogens are thought to have local to regional impact on the atmospheric chemistry around passively degassing volcanoes. In this study we demonstrate the successful deployment of a multirotor UAV (quadcopter system with custom-made lightweight payloads for the compositional analysis and gas flux estimation of volcanic plumes. The various applications and their potential are presented and discussed in example studies at three volcanoes encompassing flight heights of 450 to 3300 m and various states of volcanic activity. Field applications were performed at Stromboli volcano (Italy, Turrialba volcano (Costa Rica and Masaya volcano (Nicaragua. Two in situ gas-measuring systems adapted for autonomous airborne measurements, based on electrochemical and optical detection principles, as well as an airborne sampling unit, are introduced. We show volcanic gas composition results including abundances of CO2, SO2 and halogen species. The new instrumental setups were compared with established instruments during ground-based measurements at Masaya volcano, which resulted in CO2 ∕ SO2 ratios of 3.6 ± 0.4. For total SO2 flux estimations a small differential optical absorption spectroscopy (DOAS system measured SO2 column amounts on transversal flights below the plume at Turrialba volcano, giving 1776 ± 1108 T d−1 and 1616 ± 1007 T d−1 of SO2 during two traverses. At Stromboli volcano, elevated CO2 ∕ SO2 ratios were observed at spatial and temporal proximity

  7. Electrochemical capacitor

    Science.gov (United States)

    Anderson, Marc A.; Liu, Kuo -Chuan; Mohr, Charles M.

    1999-10-05

    An inexpensive porous metal oxide material having high surface area, good conductivity and high specific capacitance is advantageously used in an electrochemical capacitor. The materials are formed in a sol-gel process which affords control over the properties of the resultant metal oxide materials.

  8. Electrochemical construction

    Science.gov (United States)

    Einstein, Harry; Grimes, Patrick G.

    1983-08-23

    An electrochemical cell construction features a novel co-extruded plastic electrode in an interleaved construction with a novel integral separator-spacer. Also featured is a leak and impact resistant construction for preventing the spill of corrosive materials in the event of rupture.

  9. Electrochemical device

    Science.gov (United States)

    Grimes, Patrick G.; Einstein, Harry; Bellows, Richard J.

    1988-01-12

    A tunnel protected electrochemical device features channels fluidically communicating between manifold, tunnels and cells. The channels are designed to provide the most efficient use of auxiliary power. The channels have a greater hydraulic pressure drop and electrical resistance than the manifold. This will provide a design with the optimum auxiliary energy requirements.

  10. Electrochemical Cell

    DEFF Research Database (Denmark)

    1999-01-01

    The invention relates to a rechargeable electrochemical cell comprising a negative electrode, an electrolyte and a positive electrode in which the positive electrode structure comprises a lithium cobalt manganese oxide of the composition Li¿2?Co¿y?Mn¿2-y?O¿4? where 0 ... for capacity losses in lithium ion cells and lithium-alloy cells....

  11. Stress distributions due to hydrogen concentrations in electrochemically charged and aged austenitic stainless steel

    International Nuclear Information System (INIS)

    Rozenak, P.; Loew, A.

    2008-01-01

    As a result of hydrogen concentration gradients in type austenitic stainless steels, formed during electrochemical charging and followed by hydrogen loss during aging, at room temperature, surface stresses were developed. These stresses were measured by X-ray technique and the crack formation thus induced could be studied using equilibrium stress equations. After various electrochemical charging and aging times, X-ray diffraction patterns obtained from samples indicated that the reflected and broadened diffraction peaks are the result of the formation of a non-uniform but continuous solid solution in the austenitic matrix. Since both hydrogen penetrations during charging and hydrogen release during aging are diffusion controlled processes and huge hydrogen concentration gradients in the thin surface layer, at depths comparable with the depth of X-ray penetration, are observed. The non-uniform hydrogen concentration in the austenitic matrix, results to the non-uniform expansion of the atomic microstructure and latter inevitably leads to the development of internal stresses. The internal stresses development formulae's are very similar to those relating to non-uniform heating of the materials, where thermal stresses appear due to non-uniform expansion or contraction. The relevant well developed theory is applicable in our case of non-uniform hydrogen concentrations in a solid solution of electrochemically charged and aged austenitic matrix. A few cracks were present on the surface after some minutes of electrochemical charging and the severity of cracking increased as hydrogen was lost during subsequent aging. This is consistent with the expectation of high compressive stresses in the bulk of the specimen during charging and high tensile surface stresses (at the level of 1 x 10 11 Pa) during the aging process. These stresses can induce the formation of surface cracks during the aging process after electrochemical charging in the AISI 316 stainless steel

  12. Determination of UV filters in high ionic strength sample solutions using matrix-compatible coatings for solid-phase microextraction.

    Science.gov (United States)

    An, Jiwoo; Anderson, Jared L

    2018-05-15

    A double-confined polymeric ionic liquid (PIL) sorbent coating was fabricated for the determination of nine ultraviolet (UV) filters in sample solutions containing high salt content by direct immersion solid-phase microextraction (DI-SPME) coupled to high-performance liquid chromatography (HPLC). The IL monomer and crosslinker cations and anions, namely, 1-vinyl-3-decylimidazolium styrenesulfonate ([VImC 10 ][SS]) and 1,12-di(3-vinylbenzylimidazolium) dodecane distyrenesulfonate ([(VBIm) 2 C 12 ] 2[SS]), were co-polymerized to create a highly stable sorbent coating which allowed for up to 120 direct-immersion extractions in 25% NaCl (w/v) solution without a decrease in its extraction capability. Extraction and desorption parameters such as desorption solvent, agitation rate, extraction time, desorption solvent volume, and desorption time were evaluated and optimized. The analytical performance of the styrenesulfonate anion-based PIL fiber, PIL fiber containing chloride anions, and a commercially available polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber were compared. Coefficients of determination (R 2 ) for the styrenesulfonate anion-based PIL fiber ranged from 0.995 to 0.999 and the limits of detection (LODs) varied from 0.1 to 5 µg L -1 . The developed method was successfully applied in real water samples including tap, pool, and lake water, and acceptable relative recovery values were obtained. The lifetime of the PIL fiber containing chloride anions as well as the PDMS/DVB fiber were considerably shorter than the PIL fiber containing the styrenesulfonate anion, with both fibers showing a notable decrease in reproducibility and significant damage to the sorbent coating surface after 40 and 70 extractions, respectively. The R 2 values for the chloride anion containing PIL fiber were at or higher than 0.991 with LODs ranging from 0.5 to 5 µg L -1 . For the PDMS/DVB fiber, R 2 values ranged from 0.992 to 0.999 and LODs were found to be as low as 0.2

  13. Optimization of a method based on micro-matrix solid-phase dispersion (micro-MSPD for the determination of PCBs in mussel samples

    Directory of Open Access Journals (Sweden)

    Nieves Carro

    2017-03-01

    Full Text Available This paper reports the development and optimization of micro-matrix solid-phase dispersion (micro-MSPD of nine polychlorinated biphenyls (PCBs in mussel samples (Mytilus galloprovincialis by using a two-level factorial design. Four variables (amount of sample, anhydrous sodium sulphate, Florisil and solvent volume were considered as factors in the optimization process. The results suggested that only the interaction between the amount of anhydrous sodium sulphate and the solvent volume was statistically significant for the overall recovery of a trichlorinated compound, CB 28. Generally most of the considered species exhibited a similar behaviour, the sample and Florisil amounts had a positive effect on PCBs extractions and solvent volume and sulphate amount had a negative effect. The analytical determination and confirmation of PCBs were carried out by using GC-ECD and GC-MS/MS, respectively. The method was validated having satisfactory precision and accuracy with RSD values below 6% and recoveries between 81 and 116% for all congeners. The optimized method was applied to the extraction of real mussel samples from two Galician Rías.

  14. Problems, possibilities and limitations of inductively coupled plasma atomic emission spectrometry in the determination of platinum, palladium and rhodium in samples with different matrix composition

    Energy Technology Data Exchange (ETDEWEB)

    Petrova, P.; Velichkov, S. [Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. G. Bontchev Str. bl. 11, 1113 Sofia (Bulgaria); Velitchkova, N. [Geological Institute, Bulgarian Academy of Sciences, Acad. G. Bontchev Str., bl.24, 1113 Sofia (Bulgaria); Havezov, I. [Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. G. Bontchev Str. bl. 11, 1113 Sofia (Bulgaria); Daskalova, N., E-mail: das15482@svr.igic.bas.b [Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. G. Bontchev Str. bl. 11, 1113 Sofia (Bulgaria)

    2010-02-15

    The economic and geological importance of platinum group of elements has led to the development of analytical methods to quantify them in different types of samples. In the present paper the quantitative information for spectral interference in radial viewing 40.68 MHz inductively coupled plasma atomic emission spectrometry in the determination of Pt, Pd and Rh in the presence of complex matrix, containing Al, Ca, Fe, Mg, Mn, P and Ti as matrix constituents was obtained. The database was used for optimum line selections. By using the selected analysis lines the following detection limits in ng g{sup -1} were obtained: Pt 1700, Pd-1440, Rh-900. The reached detection limits determine the possibilities and limitation of the direct ICP-AES method in the determination of Pt, Pd and Rh in geological and environmental materials. The database for spectral interferences in the presence of aluminum can be used for the determination of platinum group of elements in car catalysts. The accuracy of the analytical results was experimentally demonstrated by two certified reference materials that were analyzed: SARM 7, Pt ore and recycled auto-catalyst certified reference material SRM 2556.

  15. Rapid, simple, and highly sensitive analysis of drugs in biological samples using thin-layer chromatography coupled with matrix-assisted laser desorption/ionization mass spectrometry.

    Science.gov (United States)

    Kuwayama, Kenji; Tsujikawa, Kenji; Miyaguchi, Hajime; Kanamori, Tatsuyuki; Iwata, Yuko T; Inoue, Hiroyuki

    2012-01-01

    Rapid and precise identification of toxic substances is necessary for urgent diagnosis and treatment of poisoning cases and for establishing the cause of death in postmortem examinations. However, identification of compounds in biological samples using gas chromatography and liquid chromatography coupled with mass spectrometry entails time-consuming and labor-intensive sample preparations. In this study, we examined a simple preparation and highly sensitive analysis of drugs in biological samples such as urine, plasma, and organs using thin-layer chromatography coupled with matrix-assisted laser desorption/ionization mass spectrometry (TLC/MALDI/MS). When the urine containing 3,4-methylenedioxymethamphetamine (MDMA) without sample dilution was spotted on a thin-layer chromatography (TLC) plate and was analyzed by TLC/MALDI/MS, the detection limit of the MDMA spot was 0.05 ng/spot. The value was the same as that in aqueous solution spotted on a stainless steel plate. All the 11 psychotropic compounds tested (MDMA, 4-hydroxy-3-methoxymethamphetamine, 3,4-methylenedioxyamphetamine, methamphetamine, p-hydroxymethamphetamine, amphetamine, ketamine, caffeine, chlorpromazine, triazolam, and morphine) on a TLC plate were detected at levels of 0.05-5 ng, and the type (layer thickness and fluorescence) of TLC plate did not affect detection sensitivity. In addition, when rat liver homogenate obtained after MDMA administration (10 mg/kg) was spotted on a TLC plate, MDMA and its main metabolites were identified using TLC/MALDI/MS, and the spots on a TLC plate were visualized by MALDI/imaging MS. The total analytical time from spotting of intact biological samples to the output of analytical results was within 30 min. TLC/MALDI/MS enabled rapid, simple, and highly sensitive analysis of drugs from intact biological samples and crude extracts. Accordingly, this method could be applied to rapid drug screening and precise identification of toxic substances in poisoning cases and

  16. A heteroskedastic error covariance matrix estimator using a first-order conditional autoregressive Markov simulation for deriving asympotical efficient estimates from ecological sampled Anopheles arabiensis aquatic habitat covariates

    Directory of Open Access Journals (Sweden)

    Githure John I

    2009-09-01

    Full Text Available Abstract Background Autoregressive regression coefficients for Anopheles arabiensis aquatic habitat models are usually assessed using global error techniques and are reported as error covariance matrices. A global statistic, however, will summarize error estimates from multiple habitat locations. This makes it difficult to identify where there are clusters of An. arabiensis aquatic habitats of acceptable prediction. It is therefore useful to conduct some form of spatial error analysis to detect clusters of An. arabiensis aquatic habitats based on uncertainty residuals from individual sampled habitats. In this research, a method of error estimation for spatial simulation models was demonstrated using autocorrelation indices and eigenfunction spatial filters to distinguish among the effects of parameter uncertainty on a stochastic simulation of ecological sampled Anopheles aquatic habitat covariates. A test for diagnostic checking error residuals in an An. arabiensis aquatic habitat model may enable intervention efforts targeting productive habitats clusters, based on larval/pupal productivity, by using the asymptotic distribution of parameter estimates from a residual autocovariance matrix. The models considered in this research extends a normal regression analysis previously considered in the literature. Methods Field and remote-sampled data were collected during July 2006 to December 2007 in Karima rice-village complex in Mwea, Kenya. SAS 9.1.4® was used to explore univariate statistics, correlations, distributions, and to generate global autocorrelation statistics from the ecological sampled datasets. A local autocorrelation index was also generated using spatial covariance parameters (i.e., Moran's Indices in a SAS/GIS® database. The Moran's statistic was decomposed into orthogonal and uncorrelated synthetic map pattern components using a Poisson model with a gamma-distributed mean (i.e. negative binomial regression. The eigenfunction

  17. [Matrix effect and application of field-amplified sample injection in the analysis of four tetracyclines in waters by capillary electrohoresis].

    Science.gov (United States)

    2014-08-01

    The system abilities of two chromatographic techniques, capillary electrophoresis (CE) and high performance liquid chromatography (HPLC), were compared for the analysis of four tetracyclines (tetracycline, chlorotetracycline, oxytetracycline and doxycycline). The pH, concentration of background electrolyte (BGE) were optimized for the analysis of the standard mixture sample, meanwhile, the effects of separation voltage and water matrix (pH value and hardness) effects were investigated. In hydrodynamic injection (HDI) mode, a good quantitative linearity and baseline separation within 9. 0 min were obtained for the four tetracyclines at the optimal conditions; the analytical time was about half of that of HPLC. The limits of detection (LODs) were in the range of 0. 28 - 0. 62 mg/L, and the relative standard deviations (RSDs) (n= 6) of migration time and peak area were 0. 42% - 0. 56% and 2. 24% - 2. 95%, respectively. The obtained recoveries spiked in tap water and fishpond water were at the ranges of 96. 3% - 107. 2% and 87. 1% - 105. 2%, respectively. In addition, the stacking method, field-amplified sample injection (FASI), was employed to improve the sensitivity, and the LOD was down to the range of 17.8-35.5 μg/L. With FASI stacking, the RSDs (n=6) of migration time and peak area were 0. 85%-0. 95% and 1. 69%-3.43%, respectively. Due to the advantages of simple sample pretreatment and fast speed, CE is promising in the analysis of the antibiotics in environmental water.

  18. Electrochemical cell

    Science.gov (United States)

    Kaun, T.D.

    An improved secondary electrochemical cell is disclosed having a negative electrode of lithium aluminum, a positive electrode of iron sulfide, a molten electrolyte of lithium chloride and potassium chloride, and the combination that the fully charged theoretical capacity of the negative electrode is in the range of 0.5 to 1.0 that of the positive electrode. The cell thus is negative electrode limiting during discharge cycling. Preferably, the negative electrode contains therein, in the approximate range of 1 to 10 volume % of the electrode, an additive from the materials of graphitized carbon, aluminum-iron alloy, and/or magnesium oxide.

  19. A new electrochemical sensor for highly sensitive and selective detection of nitrite in food samples based on sonochemical synthesized Calcium Ferrite (CaFe2O4) clusters modified screen printed carbon electrode.

    Science.gov (United States)

    Balasubramanian, Paramasivam; Settu, Ramki; Chen, Shen-Ming; Chen, Tse-Wei; Sharmila, Ganapathi

    2018-08-15

    Herein, we report a novel, disposable electrochemical sensor for the detection of nitrite ions in food samples based on the sonochemical synthesized orthorhombic CaFe 2 O 4 (CFO) clusters modified screen printed electrode. As synthesized CFO clusters were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transformer infrared spectroscopy (FT-IR), Thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and amperometry (i-t). Under optimal condition, the CFO modified electrode displayed a rapid current response to nitrite, a linear response range from 0.016 to 1921 µM associated with a low detection limit 6.6 nM. The suggested sensor also showed the excellent sensitivity of 3.712 μA μM -1  cm -2 . Furthermore, a good reproducibility, long-term stability and excellent selectivity were also attained on the proposed sensor. In addition, the practical applicability of the sensor was investigated via meat samples, tap water and drinking water, and showed desirable recovery rate, representing its possibilities for practical application. Copyright © 2018 Elsevier Inc. All rights reserved.

  20. Development of an enzyme-linked immunosorbent assay for seven sulfonamide residues and investigation of matrix effects from different food samples.

    Science.gov (United States)

    Zhang, Hongyan; Wang, Lei; Zhang, Yan; Fang, Guozhen; Zheng, Wenjie; Wang, Shuo

    2007-03-21

    Direct competitive enzyme-linked immunosorbent assays (ELISA) were developed to detect a broad range of sulfonamides in various matrices. Screening for this class of antibiotics in pig muscle, chicken muscle, fish, and egg extracts was accomplished by simple, rapid extraction methods carried out with only phosphate-buffered saline (PBS) buffer. Twenty milliliters of extract solution was added to 4 g of sample to extract the sulfonamide residues, and sample extracts diluted with assay buffer were directly analyzed by ELISA; matrix effects could be avoided with 1:5 dilution of pig muscle, chicken muscle, and egg extracts with PBS and 1:5 dilution of fish extract with 1% bovine serum albumin (BSA)-PBS. For liver sample, the extraction method was a little more complicated; 2 g of sample was added to 20 mL of ethanol, mixed, and then centrifuged. The solvent of 10 mL of the upper liquid was removed, and the residues were dissolved in 10 mL of PBS and then filtered; the filtrate was diluted two-fold with 0.5% BSA-PBS for ELISA. These common methods were able to detect seven sulfonamide residues such as sulfisozole, sulfathiazole, sufameter, sulfamethoxypyridazine, sulfapyridine, sulfamethizole, and sulfachlorpyridazine in pig muscle, liver, chicken muscle, egg, and fish. The assay's detection limits for these compounds were less than 100 microg kg-1. Various extraction methods were tested, and the average recovery (n=3) of 100 microg kg-1 for the matrices was found to range from 77.3 to 123.7%.

  1. Screening of Chlamydomonas reinhardtii Populations with Single-Cell Resolution by Using a High-Throughput Microscale Sample Preparation for Matrix-Assisted Laser Desorption Ionization Mass Spectrometry.

    Science.gov (United States)

    Krismer, Jasmin; Sobek, Jens; Steinhoff, Robert F; Fagerer, Stephan R; Pabst, Martin; Zenobi, Renato

    2015-08-15

    The consequences of cellular heterogeneity, such as biocide persistence, can only be tackled by studying each individual in a cell population. Fluorescent tags provide tools for the high-throughput analysis of genomes, RNA transcripts, or proteins on the single-cell level. However, the analysis of lower-molecular-weight compounds that elude tagging is still a great challenge. Here, we describe a novel high-throughput microscale sample preparation technique for single cells that allows a mass spectrum to be obtained for each individual cell within a microbial population. The approach presented includes spotting Chlamydomonas reinhardtii cells, using a noncontact microarrayer, onto a specialized slide and controlled lysis of cells separated on the slide. Throughout the sample preparation, analytes were traced and individual steps optimized using autofluorescence detection of chlorophyll. The lysates of isolated cells are subjected to a direct, label-free analysis using matrix-assisted laser desorption ionization mass spectrometry. Thus, we were able to differentiate individual cells of two Chlamydomonas reinhardtii strains based on single-cell mass spectra. Furthermore, we showed that only population profiles with real single-cell resolution render a nondistorted picture of the phenotypes contained in a population. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  2. Fabrication and application of a new modified electrochemical sensor using nano-silica and a newly synthesized Schiff base for simultaneous determination of Cd2+, Cu2+ and Hg2+ ions in water and some foodstuff samples

    International Nuclear Information System (INIS)

    Afkhami, Abbas; Soltani-Felehgari, Farzaneh; Madrakian, Tayyebeh; Ghaedi, Hamed; Rezaeivala, Majid

    2013-01-01

    Highlights: ► A new modified electrochemical sensor was constructed and used. ► A new Schiff base coated nano-silica was used as modifier. ► The electrochemical properties of electrode were studied. ► This modifier enhanced the electrochemical properties of electrode. ► The electrode was used for simultaneous determination of Cd 2+ , Cu 2+ and Hg 2+ ions. -- Abstract: A new chemically modified carbon paste electrode was constructed and used for rapid, simple, accurate, selective and highly sensitive simultaneous determination of cadmium, copper and mercury using square wave anodic stripping voltammetry (SWASV). The carbon paste electrode was modified by N,N′-bis(3-(2-thenylidenimino)propyl)piperazine coated silica nanoparticles. Compared with carbon paste electrode, the stripping peak currents had a significant increase at the modified electrode. Under the optimized conditions (deposition potential, −1.100 V vs. Ag/AgCl; deposition time, 60 s; resting time, 10 s; SW frequency, 25 Hz; pulse amplitude, 0.15 V; dc voltage step height, 4.4 mV), the detection limit was 0.3, 0.1 and 0.05 ng mL −1 for the determination of Cd 2+ , Cu 2+ and Hg 2+ , respectively. The complexation reaction of the ligand with several metal cations in methanol was studied and the stability constants of the complexes were obtained. The effects of different cations and anions on the simultaneous determination of metal ions were studied and it was found that the electrode is highly selective for the simultaneous determination of Cd 2+ , Cu 2+ and Hg 2+ . Furthermore, the present method was applied to the determination of Cd 2+ , Cu 2+ and Hg 2+ in water and some foodstuff samples

  3. Electrochemical impedance spectroscopy of oxidized porous silicon

    Energy Technology Data Exchange (ETDEWEB)

    Mula, Guido, E-mail: guido.mula@unica.it [Dipartimento di Fisica, Università degli Studi di Cagliari, Cittadella Universitaria di Monserrato, S.P. 8 km 0.700, 09042 Cagliari (Italy); Tiddia, Maria V. [Dipartimento di Fisica, Università degli Studi di Cagliari, Cittadella Universitaria di Monserrato, S.P. 8 km 0.700, 09042 Cagliari (Italy); Ruffilli, Roberta [Nanochemistry, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova (Italy); Falqui, Andrea [Nanochemistry, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova (Italy); Dipartimento di Scienze Chimiche e Geologiche, Università degli Studi di Cagliari, Cittadella Universitaria di Monserrato, S.P. 8 km 0.700, 09042 Cagliari (Italy); Palmas, Simonetta; Mascia, Michele [Dipartimento di Ingegneria Meccanica Chimica e dei Materiali, Università degli Studi di Cagliari, Piazza d' Armi, 09126 Cagliari (Italy)

    2014-04-01

    We present a study of the electrochemical oxidation process of porous silicon. We analyze the effect of the layer thickness (1.25–22 μm) and of the applied current density (1.1–11.1 mA/cm{sup 2}, values calculated with reference to the external samples surface) on the oxidation process by comparing the galvanostatic electrochemical impedance spectroscopy (EIS) measurements and the optical specular reflectivity of the samples. The results of EIS were interpreted using an equivalent circuit to separate the contribution of different sample parts. A different behavior of the electrochemical oxidation process has been found for thin and thick samples: whereas for thin samples the oxidation process is univocally related to current density and thickness, for thicker samples this is no more true. Measurements by Energy Dispersive Spectroscopy using a Scanning Electron Microscopy confirmed that the inhomogeneity of the electrochemical oxidation process is increased by higher thicknesses and higher currents. A possible explanation is proposed to justify the different behavior of thin and thick samples during the electrochemical process. - Highlights: • A multidisciplinary approach on porous Si electrochemical oxidation is proposed. • Electrochemical, optical, and structural characterizations are used. • Layer thickness and oxidation current effects are shown. • An explanation of the observed behavior is proposed.

  4. Application of a simple column-switching ion chromatography technique for removal of matrix interferences and sensitive fluorescence determination of acidic compounds (pharmaceutical drugs) in complex samples.

    Science.gov (United States)

    Muhammad, Nadeem; Subhani, Qamar; Wang, Fenglian; Guo, Dandan; Zhao, Qiming; Wu, Shuchao; Zhu, Yan

    2017-09-15

    This work illustrates the introduction of a simple, rugged and flexible column-switching ion chromatography (IC) technique for an automated on-line QuEChERS extracted samples extracts washing followed by sensitive fluorescence (FLD) determination of five acidic pharmaceutical drugs namely; clofibric acid (CLO), ibuprofen (IBU), aspirin (ASP), naproxen (NAP) and flurobrofen (FLU) in three complex samples (spinach, apple and hospital sewage sludge). An old anion exchange column IonPac ® AS11-HC was utilized as a pre-treatment column for on-line washing of inorganic and organic interferences followed by isocratic separation of five acidic drugs with another anion exchange IonPac ® AS12A analytical column by exploiting the column-switching technique. This novel method exhibited good linearity with correlation coefficients (r 2 ) for all drugs were in the range 0.976-0.996. The limit of detection and quantification of all five acidic drugs were in the range 0.024μg/kg to 8.70μg/kg and 0.082μg/kg to 0.029mg/kg, respectively, and better recoveries in the range 81.17-112.5% with percentage relative standard deviations (RSDs) less than 17.8% were obtained. This on-line sample pre-treatment method showed minimum matrix effect in the range of 0.87-1.25 except for aspirin. This simple rugged and flexible column-switching system required only 28min for maximum elimination of matrices and interferences in three complex samples extracts, isocratic separation of five acidic drugs and for the continuous regeneration of pre-treatment column prior to every subsequent analysis. Finally, this simple automated IC system was appeared so rugged and flexible, which can eliminate and wash out most of interference, impurities and matrices in complex samples, simply by adjusting the NaOH and acetonitrile concentration in washing mobile phase with maximum recoveries of acidic analytes of interest. Copyright © 2017. Published by Elsevier B.V.

  5. Electrochemical techniques implementation for corrosion rate measurement in function of humidity level in grounding systems (copper and stainless steel) in soil samples from Tunja (Colombia)

    Science.gov (United States)

    Salas, Y.; Guerrero, L.; Blanco, J.; Jimenez, C.; Vera-Monroy, S. P.; Mejía-Camacho, A.

    2017-12-01

    In this work, DC electrochemical techniques were used to determine the corrosion rate of copper and stainless-steel electrodes used in grounding, varying the level of humidity, in sandy loam and clay loam soils. The maximum corrosion potentials were: for copper -211 and -236mV and for stainless steel of -252 and -281mV, in sandy loam and clay loam respectively, showing that in sandy loam the values are higher, about 30mV. The mechanism by which steel controls corrosion is by diffusion, whereas in copper it is carried out by transfer of mass and charge, which affects the rate of corrosion, which in copper reached a maximum value of 5mm/yr and in Steel 0.8mm/yr, determined by Tafel approximations. The behaviour of the corrosion rate was mathematically adjusted to an asymptotic model that faithfully explains the C.R. as a function of humidity, however, it is necessary to define the relation between the factor □ established in the model and the precise characteristics of the soil, such as the permeability or quantity of ions present.

  6. Silica Modified with Polyaniline as a Potential Sorbent for Matrix Solid Phase Dispersion (MSPD) and Dispersive Solid Phase Extraction (d-SPE) of Plant Samples

    Science.gov (United States)

    Sowa, Ireneusz; Wójciak-Kosior, Magdalena; Strzemski, Maciej; Sawicki, Jan; Staniak, Michał; Dresler, Sławomir; Szwerc, Wojciech; Mołdoch, Jarosław; Latalski, Michał

    2018-01-01

    Polyaniline (PANI) is one of the best known conductive polymers with multiple applications. Recently, it was also used in separation techniques, mostly as a component of composites for solid-phase microextraction (SPME). In the present paper, sorbent obtained by in situ polymerization of aniline directly on silica gel particles (Si-PANI) was used for dispersive solid phase extraction (d-SPE) and matrix solid–phase extraction (MSPD). The efficiency of both techniques was evaluated with the use of high performance liquid chromatography with diode array detection (HPLC-DAD) quantitative analysis. The quality of the sorbent was verified by Raman spectroscopy and microscopy combined with automated procedure using computer image analysis. For extraction experiments, triterpenes were chosen as model compounds. The optimal conditions were as follows: protonated Si-PANI impregnated with water, 160/1 sorbent/analyte ratio, 3 min of extraction time, 4 min of desorption time and methanolic solution of ammonia for elution of analytes. The proposed procedure was successfully used for pretreatment of plant samples. PMID:29565297

  7. Pilot Testing of a Sampling Methodology for Assessing Seed Attachment Propensity and Transport Rate in a Soil Matrix Carried on Boot Soles and Bike Tires.

    Science.gov (United States)

    Hardiman, Nigel; Dietz, Kristina Charlotte; Bride, Ian; Passfield, Louis

    2017-01-01

    Land managers of natural areas are under pressure to balance demands for increased recreation access with protection of the natural resource. Unintended dispersal of seeds by visitors to natural areas has high potential for weedy plant invasions, with initial seed attachment an important step in the dispersal process. Although walking and mountain biking are popular nature-based recreation activities, there are few studies quantifying propensity for seed attachment and transport rate on boot soles and none for bike tires. Attachment and transport rate can potentially be affected by a wide range of factors for which field testing can be time-consuming and expensive. We pilot tested a sampling methodology for measuring seed attachment and transport rate in a soil matrix carried on boot soles and bike tires traversing a known quantity and density of a seed analog (beads) over different distances and soil conditions. We found % attachment rate on boot soles was much lower overall than previously reported, but that boot soles had a higher propensity for seed attachment than bike tires in almost all conditions. We believe our methodology offers a cost-effective option for researchers seeking to manipulate and test effects of different influencing factors on these two dispersal vectors.

  8. Pilot Testing of a Sampling Methodology for Assessing Seed Attachment Propensity and Transport Rate in a Soil Matrix Carried on Boot Soles and Bike Tires

    Science.gov (United States)

    Hardiman, Nigel; Dietz, Kristina Charlotte; Bride, Ian; Passfield, Louis

    2017-01-01

    Land managers of natural areas are under pressure to balance demands for increased recreation access with protection of the natural resource. Unintended dispersal of seeds by visitors to natural areas has high potential for weedy plant invasions, with initial seed attachment an important step in the dispersal process. Although walking and mountain biking are popular nature-based recreation activities, there are few studies quantifying propensity for seed attachment and transport rate on boot soles and none for bike tires. Attachment and transport rate can potentially be affected by a wide range of factors for which field testing can be time-consuming and expensive. We pilot tested a sampling methodology for measuring seed attachment and transport rate in a soil matrix carried on boot soles and bike tires traversing a known quantity and density of a seed analog (beads) over different distances and soil conditions. We found % attachment rate on boot soles was much lower overall than previously reported, but that boot soles had a higher propensity for seed attachment than bike tires in almost all conditions. We believe our methodology offers a cost-effective option for researchers seeking to manipulate and test effects of different influencing factors on these two dispersal vectors.

  9. Silica Modified with Polyaniline as a Potential Sorbent for Matrix Solid Phase Dispersion (MSPD and Dispersive Solid Phase Extraction (d-SPE of Plant Samples

    Directory of Open Access Journals (Sweden)

    Ireneusz Sowa

    2018-03-01

    Full Text Available Polyaniline (PANI is one of the best known conductive polymers with multiple applications. Recently, it was also used in separation techniques, mostly as a component of composites for solid-phase microextraction (SPME. In the present paper, sorbent obtained by in situ polymerization of aniline directly on silica gel particles (Si-PANI was used for dispersive solid phase extraction (d-SPE and matrix solid–phase extraction (MSPD. The efficiency of both techniques was evaluated with the use of high performance liquid chromatography with diode array detection (HPLC-DAD quantitative analysis. The quality of the sorbent was verified by Raman spectroscopy and microscopy combined with automated procedure using computer image analysis. For extraction experiments, triterpenes were chosen as model compounds. The optimal conditions were as follows: protonated Si-PANI impregnated with water, 160/1 sorbent/analyte ratio, 3 min of extraction time, 4 min of desorption time and methanolic solution of ammonia for elution of analytes. The proposed procedure was successfully used for pretreatment of plant samples.

  10. Dried blood spot on-card derivatization: an alternative form of sample handling to overcome the instability of thiorphan in biological matrix.

    Science.gov (United States)

    Mess, Jean-Nicholas; Taillon, Marie-Pierre; Côté, Cynthia; Garofolo, Fabio

    2012-12-01

    Thiorphan, the active metabolite of racecadotril, can undergo oxidation in biological matrices such as blood and plasma. In bioanalysis, a general approach for the stabilization of such a molecule is to derivatize the thiol group to a more stable thioether, often requiring complex handling procedures at the clinical site. In this research, the concept of dried blood spot (DBS) on-card derivatization was evaluated to stabilize thiorphan. DBS cards were in-house pre-treated with 2-bromo-3'-methoxyacetophenone and left to dry prior to blood spotting. Thiorphan was shown to be effectively derivatized to thiorphan-methoxyacetophenone once applied on the in-house pre-treated cards. Thiorphan-methoxyacetophenone was extracted by soaking a 6 mm DBS punch in methanol containing the internal standard (thiorphan-methoxyacetophenone-D₅). Chromatographic separation was achieved on a Waters XBridge C₁₈ column with a gradient elution of 5 mM NH₄HCO₃ and methanol in 2.5 min and detection by ESI(+)/MS/MS. A linear (weighted 1/x²) relationship was obtained over a concentration range of 5.00-600.00 ng/mL. The assay met regulatory guidelines acceptance criteria for sensitivity, selectivity, precision and accuracy, matrix effect, recovery, dilution integrity and multiple stability evaluations. The DBS on-card derivatization has shown to be an easy and reliable alternative form of sample collection for the quantification of thiorphan. Copyright © 2012 John Wiley & Sons, Ltd.

  11. Detection and characterization of Newcastle disease virus in clinical samples using real time RT-PCR and melting curve analysis based on matrix and fusion genes amplification

    Directory of Open Access Journals (Sweden)

    Saad Sharawi

    2013-10-01

    Full Text Available Aim: Newcastle disease is still one of the major threats for poultry industry allover the world. Therefore, attempt was made in this study to use the SYBR Green I real-time PCR with melting curves analysis as for detection and differentiation of NDV strains in suspected infected birds. Materials and Methods: Two sets of primers were used to amplify matrix and fusion genes in samples collected from suspectly infected birds (chickens and pigeons. Melting curve analysis in conjunction with real time PCR was conducted for identifying different pathotypes of the isolated NDVs. Clinical samples were propagated on specific pathogen free ECE and tested for MDT and ICIP. Results: The velogenic NDVs isolated from chickens and pigeons were distinguished with mean T 85.03±0.341 and m 83.78±0.237 respectively for M-gene amplification and for F-gene amplification the mean T were 84.04±0.037 and m 84.53±0.223. On the other hand the lentogenic NDV isolates including the vaccinal strains (HB1 and LaSota have a higher mean T (86.99±0.021 for M-gene amplification and 86.50±0.063 for F-gene amplification. The test showed no reaction with m unrelated RNA samples. In addition, the results were in good agreement with both virus isolation and biological pathotyping (MDT and ICIP. The assay offers an attractive alternative method for the diagnosis of NDV that can be easily applied in laboratory diagnosis as a screening test for the detection and differentiation of NDV infections. Conclusion: As was shown by the successful rapid detection and pathotyping of 15 NDV strains in clinical samples representing velogenic and lentogenic NDV strains, and the agreement with the results of virus isolation , biological pathotyping and pathogenicity indices. The results of this report suggests that the described SybrGreen I real-time RT-PCR assay in conjunction with Melting curve analysis used as a rapid, specific and simple diagnostic tools for detection and pathotyping of

  12. Microfluidic electrochemical device and process for chemical imaging and electrochemical analysis at the electrode-liquid interface in-situ

    Science.gov (United States)

    Yu, Xiao-Ying; Liu, Bingwen; Yang, Li; Zhu, Zihua; Marshall, Matthew J.

    2016-03-01

    A microfluidic electrochemical device and process are detailed that provide chemical imaging and electrochemical analysis under vacuum at the surface of the electrode-sample or electrode-liquid interface in-situ. The electrochemical device allows investigation of various surface layers including diffuse layers at selected depths populated with, e.g., adsorbed molecules in which chemical transformation in electrolyte solutions occurs.

  13. A Paper-Based Electrochromic Array for Visualized Electrochemical Sensing

    OpenAIRE

    Fengling Zhang; Tianyi Cai; Liang Ma; Liyuan Zhan; Hong Liu

    2017-01-01

    We report a battery-powered, paper-based electrochromic array for visualized electrochemical sensing. The paper-based sensing system consists of six parallel electrochemical cells, which are powered by an aluminum-air battery. Each single electrochemical cell uses a Prussian Blue spot electrodeposited on an indium-doped tin oxide thin film as the electrochromic indicator. Each electrochemical cell is preloaded with increasing amounts of analyte. The sample activates the battery for the sensin...

  14. Electrochemical performance of potentiodynamically deposited polyaniline electrodes in ionic liquid

    Energy Technology Data Exchange (ETDEWEB)

    Patil, Dipali S., E-mail: dipali.patilphy@gmail.com [Department of Physics, Yeungnam University, Gyeonbuk 712-749 (Korea, Republic of); Thin Film Materials Laboratory, Department of Physics, Shivaji University, Kolhapur 416 004 (India); Pawar, S.A. [Thin Film Materials Laboratory, Department of Physics, Shivaji University, Kolhapur 416 004 (India); Department of Materials Science and Engineering, Chonnam National University, Gwangju 500 757 (Korea, Republic of); Patil, S.K.; Salavi, P.P.; Kolekar, S.S. [Department of Chemistry, Shivaji University, Kolhapur 416 004 (India); Devan, R.S.; Ma, Y.R. [Department of Physics, National Dong Hwa University, Hualien 97401, Taiwan (China); Kim, J.H. [Department of Materials Science and Engineering, Chonnam National University, Gwangju 500 757 (Korea, Republic of); Shin, J.C. [Department of Physics, Yeungnam University, Gyeonbuk 712-749 (Korea, Republic of); Patil, P.S., E-mail: patilps_2000@yahoo.com [Thin Film Materials Laboratory, Department of Physics, Shivaji University, Kolhapur 416 004 (India)

    2015-10-15

    Present work reports electropolymerization of aniline onto stainless steel substrate using room temperature ionic liquid N-methyl-2-pyrrolidonium hydrogensulfate [NMP][HSO{sub 4}] by potentiodynamic electrodeposition method. To study the effect of electropolymerization cycle number on the electrochemical performance, the number of scans is varied from 1{sup st} to 5{sup th} cycle. X-ray photoelectron spectroscopy is used for the phase identification of polyaniline (PANI) films. Scanning electrochemical microscopy (SECM) was used to study the electrochemical activity of PANI films. The highest specific capacitance of 581 Fg{sup −1} and energy density of 96.6 whkg{sup −1} are obtained for the sample, deposited using four cycle. - Graphical abstract: We have synthesized PANI samples with different thickness (or deposited mass) on stainless steel as a function of deposition cycles by potentiodynamic electrodeposition in room temperature IL [NMP][HSO{sub 4}]. A globular nanostructural growth of PANI is observed over the compact background of PANI for sample P{sub 2}. The sample P{sub 4} revealed a globular structure with spongy porous morphology. This nanostructure and porous structure is useful for supercapacitor, because it reduces the diffusion resistance of the electrolyte into electrode matrix. - Highlights: • Electropolymerization of aniline using room temperature ionic liquid N-methyl-2-pyrrolidonium hydrogensulfate [NMP][HSO4]. • The highest specific capacitance of 581 Fg{sup −1} and energy density of 96.60 Whkg{sup −1} is observed for the optimized sample. • The improved specific capacitance of PANI electrode material can be used to develop high performance supercapacitor.

  15. Electrochemical performance of potentiodynamically deposited polyaniline electrodes in ionic liquid

    International Nuclear Information System (INIS)

    Patil, Dipali S.; Pawar, S.A.; Patil, S.K.; Salavi, P.P.; Kolekar, S.S.; Devan, R.S.; Ma, Y.R.; Kim, J.H.; Shin, J.C.; Patil, P.S.

    2015-01-01

    Present work reports electropolymerization of aniline onto stainless steel substrate using room temperature ionic liquid N-methyl-2-pyrrolidonium hydrogensulfate [NMP][HSO 4 ] by potentiodynamic electrodeposition method. To study the effect of electropolymerization cycle number on the electrochemical performance, the number of scans is varied from 1 st to 5 th cycle. X-ray photoelectron spectroscopy is used for the phase identification of polyaniline (PANI) films. Scanning electrochemical microscopy (SECM) was used to study the electrochemical activity of PANI films. The highest specific capacitance of 581 Fg −1 and energy density of 96.6 whkg −1 are obtained for the sample, deposited using four cycle. - Graphical abstract: We have synthesized PANI samples with different thickness (or deposited mass) on stainless steel as a function of deposition cycles by potentiodynamic electrodeposition in room temperature IL [NMP][HSO 4 ]. A globular nanostructural growth of PANI is observed over the compact background of PANI for sample P 2 . The sample P 4 revealed a globular structure with spongy porous morphology. This nanostructure and porous structure is useful for supercapacitor, because it reduces the diffusion resistance of the electrolyte into electrode matrix. - Highlights: • Electropolymerization of aniline using room temperature ionic liquid N-methyl-2-pyrrolidonium hydrogensulfate [NMP][HSO4]. • The highest specific capacitance of 581 Fg −1 and energy density of 96.60 Whkg −1 is observed for the optimized sample. • The improved specific capacitance of PANI electrode material can be used to develop high performance supercapacitor

  16. Graphene-based electrochemical supercapacitors

    Indian Academy of Sciences (India)

    Graphenes prepared by three different methods have been investigated as electrode materials in electrochemical supercapacitors. The samples prepared by exfoliation of graphitic oxide and by the transformation of nanodiamond exhibit high specific capacitance in aq. H2SO4, the value reaching up to 117 F/g. By using an ...

  17. Flow injection electrochemical hydride generation inductively coupled plasma time-of-flight mass spectrometry for the simultaneous determination of hydride forming elements and its application to the analysis of fresh water samples

    International Nuclear Information System (INIS)

    Bings, Nicolas H.; Stefanka, Zsolt; Mallada, Sergio Rodriguez

    2003-01-01

    A flow injection (FI) method was developed using electrochemical hydride generation (EcHG) as a sample introduction system, coupled to an inductively coupled plasma time-of-flight mass spectrometer (ICP-TOFMS) for rapid and simultaneous determination of six elements forming hydrides (As, Bi, Ge, Hg, Sb and Se). A novel low volume electrolysis cell, especially suited for FI experiments was designed and the conditions for simultaneous electrochemical hydride generation (EcHG; electrolyte concentrations and flow rates, electrolysis voltage and current) as well as the ICP-TOFMS operational parameters (carrier gas flow rate, modulation pulse width (MPW)) for the simultaneous determination of 12 isotopes were optimized. The compromise operation parameters of the electrolysis were found to be 1.4 and 3 ml min -1 for the anolyte and catholyte flow rates, respectively, using 2 M sulphuric acid. An optimum electrolysis current of 0.7 A (16 V) and an argon carrier gas flow rate of 0.91 l min -1 were chosen. A modulation pulse width of 5 μs, which influences the sensitivity through the amount of ions being collected by the MS per single analytical cycle, provided optimum results for the detection of transient signals. The achieved detection limits were compared with those obtained by using FI in combination with conventional nebulization (FI-ICP-TOFMS); values for chemical hydride generation (FI-CHG-ICP-TOFMS) were taken from the literature. By using a 200 μl sample loop absolute detection limits (3σ) in the range of 10-160 pg for As, Bi, Ge, Hg, Sb and 1.1 ng for Se and a precision of 4-8% for seven replicate injections of 20-100 ng ml -1 multielemental sample solutions were achieved. The analysis of a standard reference material (SRM) 1643d (NIST, 'Trace Elements in Water') showed good agreement with the certified values for As and Sb. Se showed a drastic difference, which is probably due to the presence of hydride-inactive Se species in the sample. Recoveries better than

  18. Matrix theory

    CERN Document Server

    Franklin, Joel N

    2003-01-01

    Mathematically rigorous introduction covers vector and matrix norms, the condition-number of a matrix, positive and irreducible matrices, much more. Only elementary algebra and calculus required. Includes problem-solving exercises. 1968 edition.

  19. Electrochemical energy generation

    International Nuclear Information System (INIS)

    Kreysa, G.; Juettner, K.

    1993-01-01

    The proceedings encompass 40 conference papers belonging to the following subject areas: Baseline and review papers; electrochemical fuel cells; batteries: Primary and secondary cells; electrochemical, regenerative systems for energy conversion; electrochemical hydrogen generation; electrochemistry for nuclear power plant; electrochemistry for spent nuclear fuel reprocessing; energy efficiency in electrochemical processes. There is an annex listing the authors and titles of the poster session, and compacts of the posters can be obtained from the office of the Gesellschaft Deutscher Chemiker, Abteilung Tagungen. (MM) [de

  20. First steps towards a generic sample preparation scheme for inorganic engineered nanoparticles in a complex matrix for detection, characterization, and quantification by asymmetric flow-field flow fractionation coupled to multi-angle light scattering and ICP-MS

    DEFF Research Database (Denmark)

    Wagner, Stephan; Legros, Samuel; Löschner, Katrin

    2015-01-01

    content by asymmetric flow-field flow fractionation coupled to a multi-angle light scattering detector and an inductively coupled plasma mass spectrometer. Following the proposed generic procedure SiO2-ENPs were separated from a tomato soup. Two potential sample preparation methods were tested these being...... quality criteria for method development is urgently needed for standardized and systematic development of procedures for separation of ENPs from a complex matrix. The chosen analytical technique was shown to be suitable for detecting SiO2-ENPs in a complex food matrix like tomato soup and may therefore...

  1. Highly sensitive and selective spectrofluorimetric determination of metoclopramide hydrochloride in pharmaceutical tablets and serum samples using Eu3+ ion doped in sol-gel matrix.

    Science.gov (United States)

    Attia, M S; Aboaly, M M

    2010-06-30

    A simple, sensitive and selective spectrofluorimetric method for the determination of Metoclopramide hydrochloride (MCP) is developed. The MCP can remarkably enhances the luminescence intensity of the Eu(3+) ion doped in sol-gel matrix at lambda(ex)=380 nm in DMSO at pH 8.7. The intensity of the emission band of Eu(3+) ion doped in sol-gel matrix increases due to energy transfer from MCP to Eu(3+) in the excited state. The enhancement of the emission band of Eu(3+) ion doped in sol-gel matrix at 617 nm was found to be directly proportional to the concentration of MCP with a dynamic range of 5 x 10(-9) - 1.0 x 10(-6) mol L(-1) and detection limit of 2.2 x10(-11) mol L(-1). Copyright 2010 Elsevier B.V. All rights reserved.

  2. Selective extraction of U(VI), Th(IV), and La(III) from acidic matrix solutions and environmental samples using chemically modified Amberlite XAD-16 resin

    Energy Technology Data Exchange (ETDEWEB)

    Prabhakaran, D.; Subramanian, M.S. [Department of Chemistry, Indian Institute of Technology, 600 036, Chennai (India)

    2004-06-01

    A new grafted polymer has been developed by the chemical modification of Amberlite XAD-16 (AXAD-16) polymeric matrix with [(2-dihydroxyarsinoylphenylamino)methyl]phosphonic acid (AXAD-16-AsP). The modified polymer was characterized by a combination of {sup 13}C CPMAS and {sup 31}P solid-state NMR, Fourier transform-NIR-FIR-Raman spectroscopy, CHNPS elemental analysis, and thermogravimetric analysis (TGA). The distribution studies for the extraction of U(VI), Th(IV), and La(III) from acidic solutions were performed using an AXAD-16-AsP-packed chromatographic column. The influences of various physiochemical parameters on analyte recovery were optimized by both static and dynamic methods. Accordingly, even under high acidities (>4 M), good distribution ratio (D) values (10{sup 2}-10{sup 4}) were achieved for all the analytes. Metal ion desorption was effective using 1 mol L{sup -1} (NH{sub 4}){sub 2}CO{sub 3}. From kinetic studies, a time duration of <15 min was sufficient for complete metal ion saturation of the resin phase. The maximum metal sorption capacities were found to be 0.25, 0.13, and 1.49 mmol g{sup -1} for U(VI); 0.47, 0.39, and 1.40 mmol g{sup -1} for Th(IV); and 1.44, 1.48, and 1.12 mmol g{sup -1} for La(III), in the presence of 2 mol L{sup -1} HNO{sub 3}, 2 mol L{sup -1} HCl, and under pH conditions, respectively. The analyte selectivity of the grafted polymer was tested in terms of interfering species tolerance studies. The system showed an enrichment factor of 365, 300, and 270 for U(VI), Th(IV), and La(III), and the limit of analyte detection was in the range of 18-23 ng mL{sup -1}. The practical applicability of the polymer was tested with synthetic nuclear spent fuel and seawater mixtures, natural water, and geological samples. The RSD of the total analytical procedure was within 4.9%, thus confirming the reliability of the developed method. (orig.)

  3. [Comparative evaluation of physical-mechanical properties and surface morphology of the samples of base self cured acrylic resin "Redont-kolir" polymerized in the silicone and alginate matrixes].

    Science.gov (United States)

    2014-01-01

    Determination of advantages of using silicone or alginate impression material as a matrix is decisive for quality of immediate and transitional dentures manufactured by the direct method using self-cured acrylic resins. The aim of this study was a comparative evaluation of physical-mechanical properties and surface morphology of the samples of base self-cured acrylic resin "Redont-kolir" polymerized in the silicone and alginate matrix. The samples were polymerized in the C-silicone - "Zeta plus-putty" ("Zhermack", Italy) and alginate -"Ypeen" ("Spofa Dental", Czech Republic) matrixes under different regimes: 1) in the pneumopolymerizer "Averon" at an air pressure of 3 atm., a temperature of 450C for 15 minutes, and 2) polymerization in water at 450C for 15 minutes. We determined the following physical and mechanical properties: bending load, toughness, bending stress at break, hardness by Heppler, conical point of fluidity and water absorption. Electron microscopy studies of the samples have been conducted on electronic raster microscope JSM-840 ("Jeol", Japan). As a result of studies, it was found that the optimum regime of polymerization for acrylate "Redont-kolir" is in the pneumopolymerizer "Averon" at an air pressure of 3 atm., a temperature of 450 C for 15 minutes. By the results of studying the surface morphology of the samples we can draw a conclusion that the use of an alginate impression material as matrix allows to obtain a qualitatively better surface of denture. But taking into account the technological properties of the alginate impression materials, namely an expressed shrinkage, their use for this purpose must be limited by the time during which the impression matrix remain stable in size, which is specified by manufacturer's recommendations.

  4. Nanostructured conducting molecularly imprinted polymer for selective extraction of salicylate from urine and serum samples by electrochemically controlled solid-phase micro-extraction

    International Nuclear Information System (INIS)

    Ameli, Akram; Alizadeh, Naader

    2011-01-01

    Highlights: ► Overoxidized polypyrrole templated with salicylate has been utilized as conducting molecular imprinted polymer for EC-SPME. ► This first study reported on conducting molecular imprinted polymer was used to EC-SPME of salicylate. ► Proposed method, is particularly effective in sample clean-up and selective monitoring of salicylate in physiological samples. - Abstract: Overoxidized polypyrrole (OPPy) films templated with salicylate (SA) have been utilized as conducting molecular imprinted polymers (CMIPs) for potential-induced selective solid-phase micro-extraction processes. Various important fabrication factors for controlling the performance of the OPPy films have been investigated using fluorescence spectrometry. Several key parameters such as applied potential for uptake, release, pH of uptake and release solution were varied to achieve the optimum micro-extraction procedure. The film template with SA exhibited excellent selectivity over some interference. The calibration graphs were linear in the ranges of 5 × 10 −8 to 5 × 10 −4 and 1.2 × 10 −6 to 5 × 10 −4 mol mL −1 and the detection limit was 4 × 10 −8 mol L −1 . The OPPy film as the solid-phase micro-extraction absorbent has been applied for the selective clean-up and quantification of trace amounts of SA from physiological samples. The results of scanning electron microscopy (SEM) have confirmed the nano-structure morphologies of the films.

  5. Nanostructured conducting molecularly imprinted polymer for selective extraction of salicylate from urine and serum samples by electrochemically controlled solid-phase micro-extraction

    Energy Technology Data Exchange (ETDEWEB)

    Ameli, Akram [Department of Chemistry, Faculty of Science, Tarbiat Modares University, P.O. Box 14115-175, Tehran (Iran, Islamic Republic of); Alizadeh, Naader, E-mail: alizaden@modares.ac.ir [Department of Chemistry, Faculty of Science, Tarbiat Modares University, P.O. Box 14115-175, Tehran (Iran, Islamic Republic of)

    2011-11-30

    Highlights: Black-Right-Pointing-Pointer Overoxidized polypyrrole templated with salicylate has been utilized as conducting molecular imprinted polymer for EC-SPME. Black-Right-Pointing-Pointer This first study reported on conducting molecular imprinted polymer was used to EC-SPME of salicylate. Black-Right-Pointing-Pointer Proposed method, is particularly effective in sample clean-up and selective monitoring of salicylate in physiological samples. - Abstract: Overoxidized polypyrrole (OPPy) films templated with salicylate (SA) have been utilized as conducting molecular imprinted polymers (CMIPs) for potential-induced selective solid-phase micro-extraction processes. Various important fabrication factors for controlling the performance of the OPPy films have been investigated using fluorescence spectrometry. Several key parameters such as applied potential for uptake, release, pH of uptake and release solution were varied to achieve the optimum micro-extraction procedure. The film template with SA exhibited excellent selectivity over some interference. The calibration graphs were linear in the ranges of 5 Multiplication-Sign 10{sup -8} to 5 Multiplication-Sign 10{sup -4} and 1.2 Multiplication-Sign 10{sup -6} to 5 Multiplication-Sign 10{sup -4} mol mL{sup -1} and the detection limit was 4 Multiplication-Sign 10{sup -8} mol L{sup -1}. The OPPy film as the solid-phase micro-extraction absorbent has been applied for the selective clean-up and quantification of trace amounts of SA from physiological samples. The results of scanning electron microscopy (SEM) have confirmed the nano-structure morphologies of the films.

  6. Enzyme-Gelatin Electrochemical Biosensors: Scaling Down

    Directory of Open Access Journals (Sweden)

    Hendrik A. Heering

    2012-03-01

    Full Text Available In this article we investigate the possibility of scaling down enzyme-gelatin modified electrodes by spin coating the enzyme-gelatin layer. Special attention is given to the electrochemical behavior of the selected enzymes inside the gelatin matrix. A glassy carbon electrode was used as a substrate to immobilize, in the first instance, horse heart cytochrome c (HHC in a gelatin matrix. Both a drop dried and a spin coated layer was prepared. On scaling down, a transition from diffusion controlled reactions towards adsorption controlled reactions is observed. Compared to a drop dried electrode, a spin coated electrode showed a more stable electrochemical behavior. Next to HHC, we also incorporated catalase in a spin coated gelatin matrix immobilized on a glassy carbon electrode. By spincoating, highly uniform sub micrometer layers of biocompatible matrices can be constructed. A full electrochemical study and characterization of the modified surfaces has been carried out. It was clear that in the case of catalase, gluteraldehyde addition was needed to prevent leaking of the catalase from the gelatin matrix.

  7. Variability of matrix effects in liquid and gas chromatography - mass spectrometry analysis of pesticide residues after QuEChERS sample preparation of different food crops

    Science.gov (United States)

    Gas and liquid chromatography (GC and LC) coupled to sophisticated mass spectrometry (MS) instruments are among the most powerful analytical tools currently available to monitor pesticide residues in food, among other applications. However, both GC-MS and LC-MS are susceptible to matrix effects whi...

  8. A SIMPLE AND RAPID MATRIX-ASSISTED LASER DESORPTION/IONIZATION TIME OF FLIGHT MASS SPECTROMETRY METHOD TO SCREEN FISH PLASMA SAMPLES FOR ESTROGEN-RESPONSIVE BIOMARKERS

    Science.gov (United States)

    In this study, we describe and evaluate the performance of a simple and rapid mass spectral method for screening fish plasma for estrogen-responsive biomarkers using matrix assisted laster desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS) couopled with a short...

  9. Integrated Electrochemical Analysis System with Microfluidic and Sensing Functions

    Directory of Open Access Journals (Sweden)

    Hiroaki Suzuki

    2008-02-01

    Full Text Available An integrated device that carries out the timely transport of solutions andconducts electroanalysis was constructed. The transport of solutions was based oncapillary action in overall hydrophilic flow channels and control by valves that operateon the basis of electrowetting. Electrochemical sensors including glucose, lactate,glutamic oxaloacetic transaminase (GOT, glutamic pyruvic transaminase (GPT, pH,ammonia, urea, and creatinine were integrated. An air gap structure was used for theammonia, urea, and creatinine sensors to realize a rapid response. To enhance thetransport of ammonia that existed or was produced by the enzymatic reactions, the pHof the solution was elevated by mixing it with a NaOH solution using a valve based onelectrowetting. The sensors for GOT and GPT used a freeze-dried substrate matrix torealize rapid mixing. The sample solution was transported to required sensing sites atdesired times. The integrated sensors showed distinct responses when a sample solutionreached the respective sensing sites. Linear relationships were observed between theoutput signals and the concentration or the logarithm of the concentration of theanalytes. An interferent, L-ascorbic acid, could be eliminated electrochemically in thesample injection port.

  10. Anodized titanium and stainless steel in contact with CFRP: an electrochemical approach considering galvanic corrosion.

    Science.gov (United States)

    Mueller, Yves; Tognini, Roger; Mayer, Joerg; Virtanen, Sannakaisa

    2007-09-15

    The combination of different materials in an implant gives the opportunity to better fulfill the requirements that are needed to improve the healing process. However, using different materials increases the risk of galvanic coupling corrosion. In this study, coupling effects of gold-anodized titanium, stainless steel for biomedical applications, carbon fiber reinforced polyetheretherketone (CFRP), and CFRP containing tantalum fibers are investigated electrochemically and by long-term immersion experiments in simulated body fluid (SBF). Potentiodynamic polarization experiments (i/E curves) and electrochemical impedance spectroscopy (EIS) of the separated materials showed a passive behavior of the metallic samples. Anodized titanium showed no corrosion attacks, whereas stainless steel is highly susceptibility for localized corrosion. On the other side, an active dissolution behavior of both of the CFRPs in the given environment could be determined, leading to delaminating of the carbon fibers from the matrix. Long-term immersion experiments were carried out using a set-up especially developed to simulate coupling conditions of a point contact fixator system (PC-Fix) in a biological environment. Electrochemical data were acquired in situ during the whole immersion time. The results of the immersion experiments correlate with the findings of the electrochemical investigation. Localized corrosion attacks were found on stainless steel, whereas anodized titanium showed no corrosion attacks. No significant differences between the two CFRP types could be found. Galvanic coupling corrosion in combination with crevice conditions and possible corrosion mechanisms are discussed. Copyright 2007 Wiley Periodicals, Inc.

  11. Microfabricated disposable nanosensor based on CdSe quantum dot/ionic liquid-mediated hollow fiber-pencil graphite electrode for simultaneous electrochemical quantification of uric acid and creatinine in human samples

    Energy Technology Data Exchange (ETDEWEB)

    Hooshmand, Sara; Es' haghi, Zarrin, E-mail: eshaghi@pnu.ac.ir

    2017-06-15

    In this research, a novel sensitive electrochemical nanosensor based on the cadmium selenide quantum dots (QDs)/ionic liquid mediated hollow fiber-pencil graphite electrode (HF-PGE) was prepared and applied for simultaneous determination of uric acid (UA) and creatinine (Crn) in urine and serum samples. The electrocatalytic oxidation of the analytes was investigated via differential pulse (DPV) and cyclic voltammetry (CV). The experiments were designed, in two different steps, according to Taguchi's method; OA9 L9 (3{sup 3}) and OA9 L9 (3{sup 4}) orthogonal array to optimize experimental runs. The results revealed that the electrode response was initially influenced by the types of sensor and types of ionic liquids and their ratios. The amount of QD, buffer pH, equilibration time and scan rate also influenced electrode response efficiency. According to the results of Taguchi analysis, the amount of tetra phenyl phosphonium chloride (TPPC) and QD were the most influencing parameters on the yield response of the modified electrodes. Linear ranges were obtained between 0.297–2.970 × 10{sup 3} and 0.442–8.840 × 10{sup 3} μM, with the detection limits of 0.083 and 0.229 μM and relative standard deviations (RSD) of 2.4% and 1.8%, for UA and Crn, respectively. Finally, the proposed method was successfully examined for simultaneous determination of UA and Crn in human urine and serum samples. - Highlights: • Sensor based on modified CdSe quantum dot/ionic liquid mediated hollow fiber graphite electrode. • One-step simultaneous purification, pre-concentration, extraction, back-extraction and determination of electroactive analytes. • Target analyte uric acid (UA) and creatinine (Crn) in urine and serum samples. • Disposable nature of sensor reduced risk of carry-over.

  12. Novel, Improved Sample Preparation for Rapid, Direct Identification from Positive Blood Cultures Using Matrix-Assisted Laser Desorption/Ionization Time-of-Flight (MALDI-TOF) Mass Spectrometry

    OpenAIRE

    Schubert, Sören; Weinert, Kirsten; Wagner, Chris; Gunzl, Beatrix; Wieser, Andreas; Maier, Thomas; Kostrzewa, Markus

    2011-01-01

    Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) is widely used for rapid and reliable identification of bacteria and yeast grown on agar plates. Moreover, MALDI-TOF MS also holds promise for bacterial identification from blood culture (BC) broths in hospital laboratories. The most important technical step for the identification of bacteria from positive BCs by MALDI-TOF MS is sample preparation to remove blood cells and host proteins. We present a m...

  13. An electrochemical sensor for rizatriptan benzoate determination using Fe{sub 3}O{sub 4} nanoparticle/multiwall carbon nanotube-modified glassy carbon electrode in real samples

    Energy Technology Data Exchange (ETDEWEB)

    Madrakian, Tayyebeh, E-mail: madrakian@basu.ac.ir; Maleki, Somayeh; Heidari, Mozhgan; Afkhami, Abbas

    2016-06-01

    In this paper a sensitive and selective electrochemical sensor for determination of rizatriptan benzoate (RZB) was proposed. A glassy carbon electrode was modified with nanocomposite of multiwalled carbon nanotubes (MWCNTs) and Fe{sub 3}O{sub 4} nanoparticles (Fe{sub 3}O{sub 4}/MWCNTs/GCE). The results obtained clearly show that the combination of MWCNTs and Fe{sub 3}O{sub 4} nanoparticles definitely improves the sensitivity of modified electrode to RZB determination. The morphology and electroanalytical performance of the fabricated sensor were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), square wave voltammetry (SWV) and cyclic voltammetry (CV). Also, the effect of experimental and instrumental parameters on the sensor response was evaluated. The square wave voltammetric response of the electrode to RZB was linear in the range 0.5–100.0 μmol L{sup −1} with a detection limit of 0.09 μmol L{sup −1} under the optimum conditions. The investigated method showed good stability, reproducibility and repeatability. The proposed sensor was successfully applied for real life samples of blood serum and RZB determination in pharmaceutical. - Highlights: • Simple and sensitive Fe{sub 3}O{sub 4}/MWCNTs/GCE for rizatriptan benzoate determination • The surface morphology of nanocomposite was characterized by SEM and EDS. • Rizatriptan benzoate was measured at 0.09 μmol L{sup −1} with good sensitivity and selectivity. • The electrode has been successfully applied in serum and pharmaceutical samples. • The nanocomposite had excellent electrocatalytic activity and biocompatibility.

  14. Magnetic graphene composites as both an adsorbent for sample enrichment and a MALDI-TOF MS matrix for the detection of nitropolycyclic aromatic hydrocarbons in PM2.5.

    Science.gov (United States)

    Zhang, Jiangang; Zhang, Li; Li, Ruijin; Hu, Di; Ma, Nengxuan; Shuang, Shaomin; Cai, Zongwei; Dong, Chuan

    2015-03-07

    A simple and rapid method that uses synthesized magnetic graphene composites as both an adsorbent for enrichment and as a matrix in MALDI-TOF MS analysis was developed for the detection of nitropolycyclic hydrocarbons (nitro-PAHs) in PM2.5 samples. Three nitro-PAHs were detected down to sub pg μL(-1) levels based on calculations from an instrumental signal-to-noise better than 3, which shows the feasibility of using the new materials in MALDI-TOF MS as a potential powerful analytical approach for the analysis of nitro-PAHs in PM2.5 samples.

  15. Matrix calculus

    CERN Document Server

    Bodewig, E

    1959-01-01

    Matrix Calculus, Second Revised and Enlarged Edition focuses on systematic calculation with the building blocks of a matrix and rows and columns, shunning the use of individual elements. The publication first offers information on vectors, matrices, further applications, measures of the magnitude of a matrix, and forms. The text then examines eigenvalues and exact solutions, including the characteristic equation, eigenrows, extremum properties of the eigenvalues, bounds for the eigenvalues, elementary divisors, and bounds for the determinant. The text ponders on approximate solutions, as well

  16. In-situ SEM microchip setup for electrochemical experiments with water based solutions

    DEFF Research Database (Denmark)

    Jensen, Eric; Købler, C.; Jensen, Palle Skovhus

    2013-01-01

    Studying electrochemical (EC) processes with electron microscopes offers the possibility of achieving much higher resolution imaging of nanoscale processes in real time than with optical microscopes. We have developed a vacuum sealed liquid sample electrochemical cell with electron transparent wi...

  17. High temperature and pressure electrochemical test station

    DEFF Research Database (Denmark)

    Chatzichristodoulou, Christodoulos; Allebrod, Frank; Mogensen, Mogens Bjerg

    2013-01-01

    An electrochemical test station capable of operating at pressures up to 100 bars and temperatures up to 400 ◦C has been established. It enables control of the partial pressures and mass flow of O2, N2, H2, CO2, and H2O in a single or dual environment arrangement, measurements with highly corrosive...... media, as well as localized sampling of gas evolved at the electrodes for gas analysis. A number of safety and engineering design challenges have been addressed. Furthermore, we present a series of electrochemical cell holders that have been constructed in order to accommodate different types of cells...... and facilitate different types of electrochemical measurements. Selected examples of materials and electrochemical cells examined in the test station are provided, ranging from the evaluation of the ionic conductivity of liquid electrolytic solutions immobilized in mesoporous ceramic structures...

  18. Electrochemical Reduction of solid UO2 in Molten Fluoride Salts

    International Nuclear Information System (INIS)

    Gibilaro, Mathieu; Cassayre, Laurent; Massot, Laurent; Chamelot, Pierre; Malmbeck, Rikard; Dugne, Olivier; Allegri, Patrick

    2010-01-01

    The direct electrochemical reduction of UO 2 solid pellets was carried out in LiF-CaF 2 (+ 2wt % Li 2 O) at 850 deg. C. An inert gold anode was used instead of the usual reactive sacrificial carbon anode. In this case, reduction of oxide ions yields O 2 gas evolution on the anode. Electrochemical characterisations of UO 2 pellets have been performed by linear sweep voltammetry at 10 mV/s and reduction waves associated to its direct reduction have been observed at a potential 150 mV more positive in comparison with the solvent reduction. Then, galvano-static electrolyses runs have been realised and products were characterised by SEM-EDX, EPMA/WDS and XRD. In one of the runs, uranium oxide was partially reduced and three phases were observed: non reduced UO 2 in the centre, pure metallic uranium on the external layer and an intermediate phase representing the initial stage of reduction taking place at the grain boundaries. In another run, the UO 2 sample was fully reduced. Due to oxygen removal, the U matrix had a typical coral-like structure which is characteristic of the pattern observed after the electroreduction of solid oxides. (authors)

  19. Electrochemical sensing carcinogens in beverages

    CERN Document Server

    Zia, Asif Iqbal

    2016-01-01

    This book describes a robust, low-cost electrochemical sensing system that is able to detect hormones and phthalates – the most ubiquitous endocrine disruptor compounds – in beverages and is sufficiently flexible to be readily coupled with any existing chemical or biochemical sensing system. A novel type of silicon substrate-based smart interdigital transducer, developed using MEMS semiconductor fabrication technology, is employed in conjunction with electrochemical impedance spectroscopy to allow real-time detection and analysis. Furthermore, the presented interdigital capacitive sensor design offers a sufficient penetration depth of the fringing electric field to permit bulk sample testing. The authors address all aspects of the development of the system and fully explain its benefits. The book will be of wide interest to engineers, scientists, and researchers working in the fields of physical electrochemistry and biochemistry at the undergraduate, postgraduate, and research levels. It will also be high...

  20. Electrochemical solar energy conversion

    International Nuclear Information System (INIS)

    Gerischer, H.

    1991-01-01

    The principles of solar energy conversion in photoelectrochemical cells are briefly reviewed. Cells for the generation of electric power and for energy storage in form of electrochemical energy are described. These systems are compared with solid state photovoltaic devices, and the inherent difficulties for the operation of the electrochemical systems are analyzed. (author). 28 refs, 10 figs

  1. Electrochemical thermodynamic measurement system

    Science.gov (United States)

    Reynier, Yvan [Meylan, FR; Yazami, Rachid [Los Angeles, CA; Fultz, Brent T [Pasadena, CA

    2009-09-29

    The present invention provides systems and methods for accurately characterizing thermodynamic and materials properties of electrodes and electrochemical energy storage and conversion systems. Systems and methods of the present invention are configured for simultaneously collecting a suite of measurements characterizing a plurality of interconnected electrochemical and thermodynamic parameters relating to the electrode reaction state of advancement, voltage and temperature. Enhanced sensitivity provided by the present methods and systems combined with measurement conditions that reflect thermodynamically stabilized electrode conditions allow very accurate measurement of thermodynamic parameters, including state functions such as the Gibbs free energy, enthalpy and entropy of electrode/electrochemical cell reactions, that enable prediction of important performance attributes of electrode materials and electrochemical systems, such as the energy, power density, current rate and the cycle life of an electrochemical cell.

  2. The measurement of phosphorus in low alloy steels by electrochemical methods

    International Nuclear Information System (INIS)

    Rahier, A.; Campsteyn, A.; Verheyen, E.; Verpoucke, G.

    2008-01-01

    The oscillo-polarographic method reported by Chen for the determination of phosphorus in silicates, iron ores, carbonates and tea leaves has been thoroughly studied and enhanced in view of the determination of P in various steels. Together with a carefully selected sample dissolution method, the chromatographic separation reported by Hanada et al. for eliminating the matrix has also been examined. The results of these investigations allowed finding out a path towards the successful electrochemical measurement of P in low alloy ferritic steels without eliminating the matrix. The limit of detection is 5.2 micro gram -1 in the metal. The precision ranges between 5 and 15 % relative to the mean measured values. The finely tuned method has been successfully validated using five NIST standard steels. The chromatographic method remains an option for addressing other metals in the future, should they contain unacceptable levels of possibly interfering elements.. Detailed experimental procedures are given.

  3. The measurement of phosphorus in low alloy steels by electrochemical methods

    Energy Technology Data Exchange (ETDEWEB)

    Rahier, A.; Campsteyn, A.; Verheyen, E.; Verpoucke, G.

    2008-08-15

    The oscillo-polarographic method reported by Chen for the determination of phosphorus in silicates, iron ores, carbonates and tea leaves has been thoroughly studied and enhanced in view of the determination of P in various steels. Together with a carefully selected sample dissolution method, the chromatographic separation reported by Hanada et al. for eliminating the matrix has also been examined. The results of these investigations allowed finding out a path towards the successful electrochemical measurement of P in low alloy ferritic steels without eliminating the matrix. The limit of detection is 5.2 micro gram{sup -1} in the metal. The precision ranges between 5 and 15 % relative to the mean measured values. The finely tuned method has been successfully validated using five NIST standard steels. The chromatographic method remains an option for addressing other metals in the future, should they contain unacceptable levels of possibly interfering elements.. Detailed experimental procedures are given.

  4. Matrix thermalization

    International Nuclear Information System (INIS)

    Craps, Ben; Evnin, Oleg; Nguyen, Kévin

    2017-01-01

    Matrix quantum mechanics offers an attractive environment for discussing gravitational holography, in which both sides of the holographic duality are well-defined. Similarly to higher-dimensional implementations of holography, collapsing shell solutions in the gravitational bulk correspond in this setting to thermalization processes in the dual quantum mechanical theory. We construct an explicit, fully nonlinear supergravity solution describing a generic collapsing dilaton shell, specify the holographic renormalization prescriptions necessary for computing the relevant boundary observables, and apply them to evaluating thermalizing two-point correlation functions in the dual matrix theory.

  5. Matrix thermalization

    Science.gov (United States)

    Craps, Ben; Evnin, Oleg; Nguyen, Kévin

    2017-02-01

    Matrix quantum mechanics offers an attractive environment for discussing gravitational holography, in which both sides of the holographic duality are well-defined. Similarly to higher-dimensional implementations of holography, collapsing shell solutions in the gravitational bulk correspond in this setting to thermalization processes in the dual quantum mechanical theory. We construct an explicit, fully nonlinear supergravity solution describing a generic collapsing dilaton shell, specify the holographic renormalization prescriptions necessary for computing the relevant boundary observables, and apply them to evaluating thermalizing two-point correlation functions in the dual matrix theory.

  6. Matrix thermalization

    Energy Technology Data Exchange (ETDEWEB)

    Craps, Ben [Theoretische Natuurkunde, Vrije Universiteit Brussel (VUB), and International Solvay Institutes, Pleinlaan 2, B-1050 Brussels (Belgium); Evnin, Oleg [Department of Physics, Faculty of Science, Chulalongkorn University, Thanon Phayathai, Pathumwan, Bangkok 10330 (Thailand); Theoretische Natuurkunde, Vrije Universiteit Brussel (VUB), and International Solvay Institutes, Pleinlaan 2, B-1050 Brussels (Belgium); Nguyen, Kévin [Theoretische Natuurkunde, Vrije Universiteit Brussel (VUB), and International Solvay Institutes, Pleinlaan 2, B-1050 Brussels (Belgium)

    2017-02-08

    Matrix quantum mechanics offers an attractive environment for discussing gravitational holography, in which both sides of the holographic duality are well-defined. Similarly to higher-dimensional implementations of holography, collapsing shell solutions in the gravitational bulk correspond in this setting to thermalization processes in the dual quantum mechanical theory. We construct an explicit, fully nonlinear supergravity solution describing a generic collapsing dilaton shell, specify the holographic renormalization prescriptions necessary for computing the relevant boundary observables, and apply them to evaluating thermalizing two-point correlation functions in the dual matrix theory.

  7. Electrochemical gating in scanning electrochemical microscopy

    NARCIS (Netherlands)

    Ahonen, P.; Ruiz, V.; Kontturi, K.; Liljeroth, P.; Quinn, B.M.

    2008-01-01

    We demonstrate that scanning electrochemical microscopy (SECM) can be used to determine the conductivity of nanoparticle assemblies as a function of assembly potential. In contrast to conventional electron transport measurements, this method is unique in that electrical connection to the film is not

  8. A Paper-Based Electrochromic Array for Visualized Electrochemical Sensing

    Directory of Open Access Journals (Sweden)

    Fengling Zhang

    2017-01-01

    Full Text Available We report a battery-powered, paper-based electrochromic array for visualized electrochemical sensing. The paper-based sensing system consists of six parallel electrochemical cells, which are powered by an aluminum-air battery. Each single electrochemical cell uses a Prussian Blue spot electrodeposited on an indium-doped tin oxide thin film as the electrochromic indicator. Each electrochemical cell is preloaded with increasing amounts of analyte. The sample activates the battery for the sensing. Both the preloaded analyte and the analyte in the sample initiate the color change of Prussian Blue to Prussian White. With a reaction time of 60 s, the number of electrochemical cells with complete color changes is correlated to the concentration of analyte in the sample. As a proof-of-concept analyte, lactic acid was detected semi-quantitatively using the naked eye.

  9. A Paper-Based Electrochromic Array for Visualized Electrochemical Sensing.

    Science.gov (United States)

    Zhang, Fengling; Cai, Tianyi; Ma, Liang; Zhan, Liyuan; Liu, Hong

    2017-01-31

    We report a battery-powered, paper-based electrochromic array for visualized electrochemical sensing. The paper-based sensing system consists of six parallel electrochemical cells, which are powered by an aluminum-air battery. Each single electrochemical cell uses a Prussian Blue spot electrodeposited on an indium-doped tin oxide thin film as the electrochromic indicator. Each electrochemical cell is preloaded with increasing amounts of analyte. The sample activates the battery for the sensing. Both the preloaded analyte and the analyte in the sample initiate the color change of Prussian Blue to Prussian White. With a reaction time of 60 s, the number of electrochemical cells with complete color changes is correlated to the concentration of analyte in the sample. As a proof-of-concept analyte, lactic acid was detected semi-quantitatively using the naked eye.

  10. Simplified sample preparation method for protein identification by matrix-assisted laser desorption/ionization mass spectrometry: in-gel digestion on the probe surface

    DEFF Research Database (Denmark)

    Stensballe, A; Jensen, Ole Nørregaard

    2001-01-01

    /ionization-time of flight mass spectrometry (MALDI-TOF-MS) is used as the first protein screening method in many laboratories because of its inherent simplicity, mass accuracy, sensitivity and relatively high sample throughput. We present a simplified sample preparation method for MALDI-MS that enables in-gel digestion...... for protein identification similar to that obtained by the traditional protocols for in-gel digestion and MALDI peptide mass mapping of human proteins, i.e. approximately 60%. The overall performance of the novel on-probe digestion method is comparable with that of the standard in-gel sample preparation...... protocol while being less labour intensive and more cost-effective due to minimal consumption of reagents, enzymes and consumables. Preliminary data obtained on a MALDI quadrupole-TOF tandem mass spectrometer demonstrated the utility of the on-probe digestion protocol for peptide mass mapping and peptide...

  11. Electrochemical force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kalinin, Sergei V.; Jesse, Stephen; Collins, Liam F.; Rodriguez, Brian J.

    2017-01-10

    A system and method for electrochemical force microscopy are provided. The system and method are based on a multidimensional detection scheme that is sensitive to forces experienced by a biased electrode in a solution. The multidimensional approach allows separation of fast processes, such as double layer charging, and charge relaxation, and slow processes, such as diffusion and faradaic reactions, as well as capturing the bias dependence of the response. The time-resolved and bias measurements can also allow probing both linear (small bias range) and non-linear (large bias range) electrochemical regimes and potentially the de-convolution of charge dynamics and diffusion processes from steric effects and electrochemical reactivity.

  12. Graphene nanocomposites for electrochemical cell electrodes

    Science.gov (United States)

    Zhamu, Aruna; Jang, Bor Z.; Shi, Jinjun

    2015-11-19

    A composite composition for electrochemical cell electrode applications, the composition comprising multiple solid particles, wherein (a) a solid particle is composed of graphene platelets dispersed in or bonded by a first matrix or binder material, wherein the graphene platelets are not obtained from graphitization of the first binder or matrix material; (b) the graphene platelets have a length or width in the range of 10 nm to 10 .mu.m; (c) the multiple solid particles are bonded by a second binder material; and (d) the first or second binder material is selected from a polymer, polymeric carbon, amorphous carbon, metal, glass, ceramic, oxide, organic material, or a combination thereof. For a lithium ion battery anode application, the first binder or matrix material is preferably amorphous carbon or polymeric carbon. Such a composite composition provides a high anode capacity and good cycling response. For a supercapacitor electrode application, the solid particles preferably have meso-scale pores therein to accommodate electrolyte.

  13. High-performance lithium-rich layered oxide materials: Effects of chelating agents on microstructure and electrochemical properties

    International Nuclear Information System (INIS)

    Li, Lingjun; Xu, Ming; Chen, Zhaoyong; Zhou, Xiang; Zhang, Qiaobao; Zhu, Huali; Wu, Chun; Zhang, Kaili

    2015-01-01

    The mechanisms and effects of three typical chelating agents, namely glucose, citric acid and sucrose on the sol-gel synthesis process, electrochemical degradation and structural evolution of 0.5Li 2 MnO 3 ·0.5LiNi 0.5 Co 0.2 Mn 0.3 O 2 (LLMO) materials are systematically compared for the first time. X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy analysis indicate that the sample synthesized from sucrose owns well structure, homogenous distribution, low Ni 3+ concentration and good surface structural stability during cycling, respectively. Electrochemical tests further prove that the LLMO material obtained from sucrose maintains 258.4 mAh g −1 with 94.8% capacity retention after 100 cycles at 0.2 C. The superior electrochemical performance can be ascribed to the exceptional complexing mechanism of sucrose, compared to those of the glucose and citric acid. Namely, one mole sucrose can be hydrolyzed into two different monosaccharides and further chelates three M (Li, Ni, Co and Mn) ions to form a more uniform ion-chelated matrix during sol-gel process. This discovery is an important step towards understanding the selection criterion of chelating agents for sol-gel method, that chelating agent with excellent complexing capability is beneficial to the distribution, structural stability and electrochemical properties of advanced lithium-rich layered materials

  14. Rapid extraction and quantitative detection of the herbicide diuron in surface water by a hapten-functionalized carbon nanotubes based electrochemical analyzer.

    Science.gov (United States)

    Sharma, Priyanka; Bhalla, Vijayender; Tuteja, Satish; Kukkar, Manil; Suri, C Raman

    2012-05-21

    A solid phase extraction micro-cartridge containing a non-polar polystyrene absorbent matrix was coupled with an electrochemical immunoassay analyzer (EIA) and used for the ultra-sensitive detection of the phenyl urea herbicide diuron in real samples. The EIA was fabricated by using carboxylated carbon nanotubes (CNTs) functionalized with a hapten molecule (an amine functionalized diuron derivative). Screen printed electrodes (SPE) were modified with these haptenized CNTs and specific in-house generated anti diuron antibodies were used for bio-interface development. The immunodetection was realized in a competitive electrochemical immunoassay format using alkaline phosphatase labeled secondary anti-IgG antibody. The addition of 1-naphthyl phosphate substrate resulted in the production of an electrochemically active product, 1-naphthol, which was monitored by using differential pulse voltammetry (DPV). The assay exhibited excellent sensitivity and specificity having a dynamic response range of 0.01 pg mL(-1) to 10 μg mL(-1) for diuron with a limit of detection of around 0.1 pg mL(-1) (n = 3) in standard water samples. The micro-cartridge coupled hapten-CNTs modified SPE provided an effective and efficient electrochemical immunoassay for the real-time monitoring of pesticides samples with a very high degree of sensitivity.

  15. Fundamentals of electrochemical science

    CERN Document Server

    Oldham, Keith

    1993-01-01

    Key Features* Deals comprehensively with the basic science of electrochemistry* Treats electrochemistry as a discipline in its own right and not as a branch of physical or analytical chemistry* Provides a thorough and quantitative description of electrochemical fundamentals

  16. Electrochemical Analysis of Neurotransmitters

    Science.gov (United States)

    Bucher, Elizabeth S.; Wightman, R. Mark

    2015-07-01

    Chemical signaling through the release of neurotransmitters into the extracellular space is the primary means of communication between neurons. More than four decades ago, Ralph Adams and his colleagues realized the utility of electrochemical methods for the study of easily oxidizable neurotransmitters, such as dopamine, norepinephrine, and serotonin and their metabolites. Today, electrochemical techniques are frequently coupled to microelectrodes to enable spatially resolved recordings of rapid neurotransmitter dynamics in a variety of biological preparations spanning from single cells to the intact brain of behaving animals. In this review, we provide a basic overview of the principles underlying constant-potential amperometry and fast-scan cyclic voltammetry, the most commonly employed electrochemical techniques, and the general application of these methods to the study of neurotransmission. We thereafter discuss several recent developments in sensor design and experimental methodology that are challenging the current limitations defining the application of electrochemical methods to neurotransmitter measurements.

  17. Organic electrochemical transistors

    KAUST Repository

    Rivnay, Jonathan; Inal, Sahika; Salleo, Alberto; Owens, Ró isí n M.; Berggren, Magnus; Malliaras, George G.

    2018-01-01

    Organic electrochemical transistors (OECTs) make effective use of ion injection from an electrolyte to modulate the bulk conductivity of an organic semiconductor channel. The coupling between ionic and electronic charges within the entire volume

  18. ELECTROCHEMICAL STUDIES OF CARBON STEEL CORROSION IN HANFORD DOUBLE SHELL TANK (DST) WASTE

    Energy Technology Data Exchange (ETDEWEB)

    DUNCAN, J.B.; WINDISCH, C.F.

    2006-10-13

    This paper reports on the electrochemical scans for the supernatant of Hanford double-shell tank (DST) 241-SY-102 and the electrochemical scans for the bottom saltcake layer for Hanford DST 241-AZ-102. It further reports on the development of electrochemical test cells adapted to both sample volume and hot cell constraints.

  19. Matrix Effect Evaluation and Method Validation of Azoxystrobin and Difenoconazole Residues in Red Flesh Dragon Fruit (Hylocereus polyrhizus) Matrices Using QuEChERS Sample Preparation Methods Followed by LC-MS/MS Determination.

    Science.gov (United States)

    Noegrohati, Sri; Hernadi, Elan; Asviastuti, Syanti

    2018-03-30

    Production of red flesh dragon fruit (Hylocereus polyrhizus) was hampered by Colletotrichum sp. Pre-harvest application of azoxystrobin and difenoconazole mixture is recommended, therefore, a selective and sensitive multi residues analytical method is required in monitoring and evaluating the commodity's safety. LC-MS/MS is a well-established analytical technique for qualitative and quantitative determination in complex matrices. However, this method is hurdled by co-eluted coextractives interferences. This work evaluated the pH effect of acetate buffered and citrate buffered QuEChERS sample preparation in their effectiveness of matrix effect reduction. Citrate buffered QuEChERS proved to produce clean final extract with relative matrix effect 0.4%-0.7%. Method validation of the selected sample preparation followed by LC-MS/MS for whole dragon fruit, flesh and peel matrices fortified at 0.005, 0.01, 0.1 and 1 g/g showed recoveries 75%-119%, intermediate repeatability 2%-14%. The expanded uncertainties were 7%-48%. Based on the international acceptance criteria, this method is valid.

  20. Electrochemical polymer electrolyte membranes

    CERN Document Server

    Fang, Jianhua; Wilkinson, David P

    2015-01-01

    Electrochemical Polymer Electrolyte Membranes covers PEMs from fundamentals to applications, describing their structure, properties, characterization, synthesis, and use in electrochemical energy storage and solar energy conversion technologies. Featuring chapters authored by leading experts from academia and industry, this authoritative text: Discusses cutting-edge methodologies in PEM material selection and fabricationPoints out important challenges in developing PEMs and recommends mitigation strategies to improve PEM performanceAnalyzes the cur

  1. Rapid method for direct identification of bacteria in urine and blood culture samples by matrix-assisted laser desorption ionization time-of-flight mass spectrometry: intact cell vs. extraction method.

    Science.gov (United States)

    Ferreira, L; Sánchez-Juanes, F; Muñoz-Bellido, J L; González-Buitrago, J M

    2011-07-01

    Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) is a fast and reliable technology for the identification of microorganisms with proteomics approaches. Here, we compare an intact cell method and a protein extraction method before application on the MALDI plate for the direct identification of microorganisms in both urine and blood culture samples from clinical microbiology laboratories. The results show that the intact cell method provides excellent results for urine and is a good initial method for blood cultures. The extraction method complements the intact cell method, improving microorganism identification from blood culture. Thus, we consider that MALDI-TOF MS performed directly on urine and blood culture samples, with the protocols that we propose, is a suitable technique for microorganism identification, as compared with the routine methods used in the clinical microbiology laboratory. © 2010 The Authors. Clinical Microbiology and Infection © 2010 European Society of Clinical Microbiology and Infectious Diseases.

  2. Using solvent-free sample preparation to promote protonation of poly(ethylene oxide)s with labile end-groups in matrix-assisted laser desorption/ionisation.

    Science.gov (United States)

    Mazarin, Michael; Phan, Trang N T; Charles, Laurence

    2008-12-01

    Protonation is usually required to observe intact ions during matrix-assisted laser desorption/ionization (MALDI) of polymers containing fragile end-groups while cation adduction induces chain-end degradation. These polymers, generally obtained via living free radical polymerization techniques, are terminated with a functionality in which a bond is prone to homolytic cleavage, as required by the polymerization process. A solvent-free sample preparation method was used here to avoid salt contaminant from the solvent traditionally used in the dried-droplet MALDI procedure. Solvent-based and solvent-free sample preparations were compared for a series of three poly(ethylene oxide) polymers functionalized with a labile end-group in a nitroxide-mediated polymerization reaction, using 2,4,6-trihydroxyacetophenone (THAP) as the matrix without any added salt. Intact oligomer ions could only be produced as protonated molecules in solvent-free MALDI while sodium adducts of degraded polymers were formed from the dried-droplet samples. Although MALDI analysis was performed at the laser threshold, fragmentation of protonated macromolecules was still observed to occur. However, in contrast to sodiated molecules, dissociation of protonated oligomers does not involve the labile C--ON bond of the end-group. As the macromolecule size increased, protonation appeared to be less efficient and sodium adduction became the dominant ionization process, although no sodium salt was added in the preparation. Formation of sodiated degraded macromolecules would be dictated by increasing cation affinity as the size of the oligomers increases and would reveal the presence of salts at trace levels in the MALDI samples.

  3. Matrix inequalities

    CERN Document Server

    Zhan, Xingzhi

    2002-01-01

    The main purpose of this monograph is to report on recent developments in the field of matrix inequalities, with emphasis on useful techniques and ingenious ideas. Among other results this book contains the affirmative solutions of eight conjectures. Many theorems unify or sharpen previous inequalities. The author's aim is to streamline the ideas in the literature. The book can be read by research workers, graduate students and advanced undergraduates.

  4. Electrochemical Incineration of Phenolic Compounds from the Hydrocarbon Industry Using Boron-Doped Diamond Electrodes

    Directory of Open Access Journals (Sweden)

    Alejandro Medel

    2012-01-01

    Full Text Available Electrochemical incineration using boron-doped diamond electrodes was applied to samples obtained from a refinery and compared to the photo-electro-Fenton process in order to selectively eliminate the phenol and phenolic compounds from a complex matrix. Due to the complex chemical composition of the sample, a pretreatment to the sample in order to isolate the phenolic compounds was applied. The effects of the pretreatment and of pH on the degradation of the phenolic compounds were evaluated. The results indicate that the use of a boron-doped diamond electrode in an electrochemical incineration process mineralizes 99.5% of the phenolic sample content. Working in acidic medium (pH = 1, and applying 2 A at 298 K under constant stirring for 2 hours, also results in the incineration of the reaction intermediates reflected by 97% removal of TOC. In contrast, the photo-electro-Fenton process results in 99.9% oxidation of phenolic compounds with only a 25.69% removal of TOC.

  5. Electrochemical behavior of low phosphorus electroless Ni-P-Si3N4 composite coatings

    International Nuclear Information System (INIS)

    Balaraju, J.N.; Ezhil Selvi, V.; Rajam, K.S.

    2010-01-01

    In the present investigation the electroless Ni-P-Si 3 N 4 composite coatings were prepared by using a low phosphorus bath containing submicron size silicon nitride particles. Plain Ni-P deposits were also prepared for comparison. The phosphorus contents present in electroless plain Ni-P and Ni-P-Si 3 N 4 coatings are 3.7 and 3.4 wt.%, respectively. Scanning electron microscope (SEM) images obtained for composite coatings (cross-sections) showed that the second phase particles are uniformly distributed throughout the thickness of the deposits. It was found that nodularity increased with particle codeposition in Ni-P matrix. To find out the electrochemical behavior of plain Ni-P and composite coatings, potentiodynamic polarization and electrochemical impedance (EIS) studies were carried out in 3.5 wt.% sodium chloride solution in non-deaerated condition. Second phase particle incorporation in Ni-P matrix indicated a marginal decrease in corrosion current density compared to the plain Ni-P deposits. This was further confirmed by EIS studies and SEM analysis of the corroded samples.

  6. Corrosive effect of the type of soil in the systems of grounding more used (copper and stainless steel) for local soil samples from the city of Tunja (Colombia), by means of electrochemical techniques

    Science.gov (United States)

    Guerrero, L.; Salas, Y.; Blanco, J.

    2016-02-01

    In this work electrochemical techniques were used to determine the corrosion behaviour of copper and stainless steel electrodes, used in grounding varying soil type with which they react. A slight but significant change in the corrosion rate, linear polarization resistance and equivalent parameters in the technique of electrochemical impedance spectroscopy circuit was observed. Electrolytes in soils are slightly different depending on laboratory study, but the influence was noted in the retention capacity of water, mainly due to clays, affecting ion mobility and therefore measures such as the corrosion rate. Behaviour was noted in lower potential for copper corrosion, though the corrosion rate regardless of the type of soil, was much higher for electrodes based on copper, by several orders of magnitude.

  7. Novel, improved sample preparation for rapid, direct identification from positive blood cultures using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry.

    Science.gov (United States)

    Schubert, Sören; Weinert, Kirsten; Wagner, Chris; Gunzl, Beatrix; Wieser, Andreas; Maier, Thomas; Kostrzewa, Markus

    2011-11-01

    Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) is widely used for rapid and reliable identification of bacteria and yeast grown on agar plates. Moreover, MALDI-TOF MS also holds promise for bacterial identification from blood culture (BC) broths in hospital laboratories. The most important technical step for the identification of bacteria from positive BCs by MALDI-TOF MS is sample preparation to remove blood cells and host proteins. We present a method for novel, rapid sample preparation using differential lysis of blood cells. We demonstrate the efficacy and ease of use of this sample preparation and subsequent MALDI-TOF MS identification, applying it to a total of 500 aerobic and anaerobic BCs reported to be positive by a Bactec 9240 system. In 86.5% of all BCs, the microorganism species were correctly identified. Moreover, in 18/27 mixed cultures at least one isolate was correctly identified. A novel method that adjusts the score value for MALDI-TOF MS results is proposed, further improving the proportion of correctly identified samples. The results of the present study show that the MALDI-TOF MS-based method allows rapid (directly from positive BCs and with high accuracy. Copyright © 2011 American Society for Investigative Pathology and the Association for Molecular Pathology. Published by Elsevier Inc. All rights reserved.

  8. Preparation and electrochemical application of a new biosensor ...

    Indian Academy of Sciences (India)

    The electrocatalytic behaviour of oxidized acetaminophen was studied at the surface of the biosensor, using various electrochemical methods. The advantages of this ..... each case, a few ml of methanol was added to sample, and then it was ...

  9. Towards a fully automated lab-on-a-disc system integrating sample enrichment and detection of analytes from complex matrices

    DEFF Research Database (Denmark)

    Andreasen, Sune Zoëga

    the technology on a large scale from fulfilling its potential for maturing into applied technologies and products. In this work, we have taken the first steps towards realizing a capable and truly automated “sample-to-answer” analysis system, aimed at small molecule detection and quantification from a complex...... sample matrix. The main result is a working prototype of a microfluidic system, integrating both centrifugal microfluidics for sample handling, supported liquid membrane extraction (SLM) for selective and effective sample treatment, as well as in-situ electrochemical detection. As a case study...

  10. Materials for electrochemical capacitors

    Science.gov (United States)

    Simon, Patrice; Gogotsi, Yury

    2008-11-01

    Electrochemical capacitors, also called supercapacitors, store energy using either ion adsorption (electrochemical double layer capacitors) or fast surface redox reactions (pseudo-capacitors). They can complement or replace batteries in electrical energy storage and harvesting applications, when high power delivery or uptake is needed. A notable improvement in performance has been achieved through recent advances in understanding charge storage mechanisms and the development of advanced nanostructured materials. The discovery that ion desolvation occurs in pores smaller than the solvated ions has led to higher capacitance for electrochemical double layer capacitors using carbon electrodes with subnanometre pores, and opened the door to designing high-energy density devices using a variety of electrolytes. Combination of pseudo-capacitive nanomaterials, including oxides, nitrides and polymers, with the latest generation of nanostructured lithium electrodes has brought the energy density of electrochemical capacitors closer to that of batteries. The use of carbon nanotubes has further advanced micro-electrochemical capacitors, enabling flexible and adaptable devices to be made. Mathematical modelling and simulation will be the key to success in designing tomorrow's high-energy and high-power devices.

  11. Electrochemical reduction of NOx

    DEFF Research Database (Denmark)

    Traulsen, Marie Lund

    NO and NO2 (collectively referred to as NOx) are air pollutants, and the largest single contributor to NOx pollution is automotive exhaust. This study investigates electrochemical deNOx, a technology which aims to remove NOx from automotive diesel exhaust by electrochemical reduction of NOx to N2...... and O2. The focus in this study is on improving the activity and selectivity of solid oxide electrodes for electrochemical deNOx by addition of NOx storage compounds to the electrodes. Two different composite electrodes, La0.85Sr0.15MnO3-δ-Ce0.9Gd0.1O1.95 (LSM15-CGO10) and La0.85Sr0.15FeO3-δ-Ce0.9Gd0.1O......1.95 (LSF15-CGO10), have been investigated in combination with three different NOx storage compounds: BaO, K2O and MnOx. The main focus in the investigation has been on conversion measurements and electrochemical characterization, the latter by means of electrochemical impedance spectroscopy...

  12. Matrix analysis

    CERN Document Server

    Bhatia, Rajendra

    1997-01-01

    A good part of matrix theory is functional analytic in spirit. This statement can be turned around. There are many problems in operator theory, where most of the complexities and subtleties are present in the finite-dimensional case. My purpose in writing this book is to present a systematic treatment of methods that are useful in the study of such problems. This book is intended for use as a text for upper division and gradu­ ate courses. Courses based on parts of the material have been given by me at the Indian Statistical Institute and at the University of Toronto (in collaboration with Chandler Davis). The book should also be useful as a reference for research workers in linear algebra, operator theory, mathe­ matical physics and numerical analysis. A possible subtitle of this book could be Matrix Inequalities. A reader who works through the book should expect to become proficient in the art of deriving such inequalities. Other authors have compared this art to that of cutting diamonds. One first has to...

  13. Systems, methods and computer-readable media for modeling cell performance fade of rechargeable electrochemical devices

    Science.gov (United States)

    Gering, Kevin L

    2013-08-27

    A system includes an electrochemical cell, monitoring hardware, and a computing system. The monitoring hardware periodically samples performance characteristics of the electrochemical cell. The computing system determines cell information from the performance characteristics of the electrochemical cell. The computing system also develops a mechanistic level model of the electrochemical cell to determine performance fade characteristics of the electrochemical cell and analyzing the mechanistic level model to estimate performance fade characteristics over aging of a similar electrochemical cell. The mechanistic level model uses first constant-current pulses applied to the electrochemical cell at a first aging period and at three or more current values bracketing a first exchange current density. The mechanistic level model also is based on second constant-current pulses applied to the electrochemical cell at a second aging period and at three or more current values bracketing the second exchange current density.

  14. Comprehensive proteome analysis of nasal lavage samples after controlled exposure to welding nanoparticles shows an induced acute phase and a nuclear receptor, LXR/RXR, activation that influence the status of the extracellular matrix.

    Science.gov (United States)

    Ali, Neserin; Ljunggren, Stefan; Karlsson, Helen M; Wierzbicka, Aneta; Pagels, Joakim; Isaxon, Christina; Gudmundsson, Anders; Rissler, Jenny; Nielsen, Jörn; Lindh, Christian H; Kåredal, Monica

    2018-01-01

    Epidemiological studies have shown that many welders experience respiratory symptoms. During the welding process a large number of airborne nanosized particles are generated, which might be inhaled and deposited in the respiratory tract. Knowledge of the underlying mechanisms behind observed symptoms is still partly lacking, although inflammation is suggested to play a central role. The aim of this study was to investigate the effects of welding fume particle exposure on the proteome expression level in welders suffering from respiratory symptoms, and changes in protein mediators in nasal lavage samples were analyzed. Such mediators will be helpful to clarify the pathomechanisms behind welding fume particle-induced effects. In an exposure chamber, 11 welders with work-related symptoms in the lower airways during the last month were exposed to mild-steel welding fume particles (1 mg/m 3 ) and to filtered air, respectively, in a double-blind manner. Nasal lavage samples were collected before, immediately after, and the day after exposure. The proteins in the nasal lavage were analyzed with two different mass spectrometry approaches, label-free discovery shotgun LC-MS/MS and a targeted selected reaction monitoring LC-MS/MS analyzing 130 proteins and four in vivo peptide degradation products. The analysis revealed 30 significantly changed proteins that were associated with two main pathways; activation of acute phase response signaling and activation of LXR/RXR, which is a nuclear receptor family involved in lipid signaling. Connective tissue proteins and proteins controlling the degradation of such tissues, including two different matrix metalloprotease proteins, MMP8 and MMP9, were among the significantly changed enzymes and were identified as important key players in the pathways. Exposure to mild-steel welding fume particles causes measurable changes on the proteome level in nasal lavage matrix in exposed welders, although no clinical symptoms were manifested. The

  15. Electrochemical energy storage

    CERN Document Server

    Tarascon, Jean-Marie

    2015-01-01

    The electrochemical storage of energy has become essential in assisting the development of electrical transport and use of renewable energies. French researchers have played a key role in this domain but Asia is currently the market leader. Not wanting to see history repeat itself, France created the research network on electrochemical energy storage (RS2E) in 2011. This book discusses the launch of RS2E, its stakeholders, objectives, and integrated structure that assures a continuum between basic research, technological research and industries. Here, the authors will cover the technological

  16. Electrochemical Hydrogen Evolution

    DEFF Research Database (Denmark)

    Laursen, A.B.; Varela Gasque, Ana Sofia; Dionigi, F.

    2012-01-01

    The electrochemical hydrogen evolution reaction (HER) is growing in significance as society begins to rely more on renewable energy sources such as wind and solar power. Thus, research on designing new, inexpensive, and abundant HER catalysts is important. Here, we describe how a simple experiment...... catalysts based on this. Suited for upper-level high school and first-year university students, this exercise involves using a basic two-cell electrochemical setup to test multiple electrode materials as catalysts at one applied potential, and then constructing a volcano curve with the resulting currents...

  17. Strategy BMT Al-Ittihad Using Matrix IE, Matrix SWOT 8K, Matrix SPACE and Matrix TWOS

    Directory of Open Access Journals (Sweden)

    Nofrizal Nofrizal

    2018-03-01

    Full Text Available This research aims to formulate and select BMT Al-Ittihad Rumbai strategy to face the changing of business environment both from internal environment such as organization resources, finance, member and external business such as competitor, economy, politics and others. This research method used Analysis of EFAS, IFAS, IE Matrix, SWOT-8K Matrix, SPACE Matrix and TWOS Matrix. our hope from this research it can assist BMT Al-Ittihad in formulating and selecting strategies for the sustainability of BMT Al-Ittihad in the future. The sample in this research is using purposive sampling technique that is the manager and leader of BMT Al-IttihadRumbaiPekanbaru. The result of this research shows that the position of BMT Al-Ittihad using IE Matrix, SWOT-8K Matrix and SPACE Matrix is in growth position, stabilization and aggressive. The choice of strategy after using TWOS Matrix is market penetration, market development, vertical integration, horizontal integration, and stabilization (careful.

  18. Matrix pentagons

    Science.gov (United States)

    Belitsky, A. V.

    2017-10-01

    The Operator Product Expansion for null polygonal Wilson loop in planar maximally supersymmetric Yang-Mills theory runs systematically in terms of multi-particle pentagon transitions which encode the physics of excitations propagating on the color flux tube ending on the sides of the four-dimensional contour. Their dynamics was unraveled in the past several years and culminated in a complete description of pentagons as an exact function of the 't Hooft coupling. In this paper we provide a solution for the last building block in this program, the SU(4) matrix structure arising from internal symmetry indices of scalars and fermions. This is achieved by a recursive solution of the Mirror and Watson equations obeyed by the so-called singlet pentagons and fixing the form of the twisted component in their tensor decomposition. The non-singlet, or charged, pentagons are deduced from these by a limiting procedure.

  19. Matrix pentagons

    Directory of Open Access Journals (Sweden)

    A.V. Belitsky

    2017-10-01

    Full Text Available The Operator Product Expansion for null polygonal Wilson loop in planar maximally supersymmetric Yang–Mills theory runs systematically in terms of multi-particle pentagon transitions which encode the physics of excitations propagating on the color flux tube ending on the sides of the four-dimensional contour. Their dynamics was unraveled in the past several years and culminated in a complete description of pentagons as an exact function of the 't Hooft coupling. In this paper we provide a solution for the last building block in this program, the SU(4 matrix structure arising from internal symmetry indices of scalars and fermions. This is achieved by a recursive solution of the Mirror and Watson equations obeyed by the so-called singlet pentagons and fixing the form of the twisted component in their tensor decomposition. The non-singlet, or charged, pentagons are deduced from these by a limiting procedure.

  20. Matrix algebra for higher order moments

    NARCIS (Netherlands)

    Meijer, Erik

    2005-01-01

    A large part of statistics is devoted to the estimation of models from the sample covariance matrix. The development of the statistical theory and estimators has been greatly facilitated by the introduction of special matrices, such as the commutation matrix and the duplication matrix, and the

  1. ELECTROCHEMICAL SYNTHEZIS AND CHARACTERIZATION OF POLYPYRROLE FOR DODECYLSULFATE SENSOR MEMBRANE

    Directory of Open Access Journals (Sweden)

    Abdul Haris Watoni

    2010-06-01

    Full Text Available A conducting polymer, polypyrrole, has been electrochemically synthesized from pyrrole monomer using cyclic voltammetry technique in aqueous solution in the presence of HDS dopant and KNO3 supporting electrolyte. The polymer was deposited on the surface of an Au-wire and the modified electrode obtained was then used as dodecylsulfate (DS- ion sensor electrode. The best performance PPy-DS modified-Au electrode conditioned in the air system without HDS or SDS solution gave linear potential response for the concentration range of 1.0 x 10-5 - 1.0 x 10-3 M, sensitivity of 54.5 mV/decade, detection limit of 1.0 x 10-5 M, and response time of 23 - 30 second.  The electrode showed good selectivity towards other anions, therefore can be used to determine SDS concentration in real samples system without any change of the samples matrix.   Keywords: polypyrrole, SDS, cyclic voltammetry

  2. Electrochemical Power Sources

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 6; Issue 7. Electrochemical Power Sources - Rechargeable Batteries. A K Shukla S K Martha. General Article Volume 6 Issue 7 July 2001 pp 52-63. Fulltext. Click here to view fulltext PDF. Permanent link:

  3. Electro-chemical grinding

    Science.gov (United States)

    Feagans, P. L.

    1972-01-01

    Electro-chemical grinding technique has rotation speed control, constant feed rates, and contour control. Hypersonic engine parts of nickel alloys can be almost 100% machined, keeping tool pressure at virtual zero. Technique eliminates galling and permits constant surface finish and burr-free interrupted cutting.

  4. Mixed hemimicelles solid-phase extraction based on ionic liquid-coated Fe3O4/SiO2 nanoparticles for the determination of flavonoids in bio-matrix samples coupled with high performance liquid chromatography.

    Science.gov (United States)

    He, Huan; Yuan, Danhua; Gao, Zhanqi; Xiao, Deli; He, Hua; Dai, Hao; Peng, Jun; Li, Nan

    2014-01-10

    A novel magnetic solid-phase extraction (MSPE) method based on mixed hemimicelles of room temperature ionic liquids (RTILs) coated Fe3O4/SiO2 nanoparticles (NPs) was developed for simultaneous extraction of trace amounts of flavonoids in bio-matrix samples. A comparative study on the use of RTILs (C16mimBr) and CTAB-coated Fe3O4/SiO2 NPs as sorbents was presented. Owing to bigger adsorption amounts for analytes, RTILs-coated Fe3O4/SiO2 NPs was selected as MSPE materials and three analytes luteolin, quercetin and kaempferol can be quantitatively extracted and simultaneously determined coupled with high performance liquid chromatography (HPLC) in urine samples. No interferences were caused by proteins or endogenous compounds. Good linearity (R(2)>0.9993) for all calibration curves was obtained, and the limits of detection (LOD) for luteolin, quercetin and kaempferol were 0.10 ng/mL, 0.50 ng/mL and 0.20 ng/mL in urine samples, respectively. Satisfactory recoveries (93.5-97.6%, 90.1-95.4% and 93.3-96.6% for luteolin, quercetin and kaempferol) in biological matrices were achieved. It was notable that while using a small amount of Fe3O4/SiO2 NPs (4.0 mg) and C16mimBr (1.0 mg), satisfactory preconcentration factors and extraction recoveries for the three flavonoids were obtained. To the best of our knowledge, this is the first time a mixed hemimicelles MSPE method based on RTILs and Fe3O4/SiO2 NPs magnetic separation has ever been used for pretreatment of complex biological samples. Copyright © 2013 Elsevier B.V. All rights reserved.

  5. Yersinia enterocolitica in Diagnostic Fecal Samples from European Dogs and Cats: Identification by Fourier Transform Infrared Spectroscopy and Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry

    Science.gov (United States)

    Stamm, Ivonne; Hailer, Mandy; Depner, Barbara; Kopp, Peter A.

    2013-01-01

    Yersinia enterocolitica is the main cause of yersiniosis in Europe, one of the five main bacterial gastrointestinal diseases of humans. Beside pigs, companion animals, especially dogs and cats, were repeatedly discussed in the past as a possible source of pathogenic Y. enterocolitica. To investigate the presence and types of Y. enterocolitica in companion animals, a total of 4,325 diagnostic fecal samples from dogs and 2,624 samples from cats were tested. The isolates obtained were differentiated by using matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) and Fourier transform infrared spectroscopy (FT-IR). Isolated Y. enterocolitica strains were bioserotyped. The detection of the ail gene by PCR and confirmation by FT-IR were used as a pathogenicity marker. Y. enterocolitica strains were isolated from 198 (4.6%) of the dog and 8 (0.3%) of the cat fecal samples investigated. One hundred seventy-nine isolates from dogs were analyzed in detail. The virulence factor Ail was detected in 91.6% of isolates. Isolates of biotype 4 (54.7%) and, to a lesser extent, biotypes 2 (23.5%), 3 (11.2%), and 5 (2.2%) were detected. The remaining 8.4% of strains belonged to the ail-negative biotype 1A. All 7 isolates from cats that were investigated in detail were ail positive. These results indicate that companion animals could be a relevant reservoir for a broad range of presumptively human-pathogenic Y. enterocolitica types. MALDI-TOF MS and FT-IR proved to be valuable methods for the rapid identification of Y. enterocolitica, especially in regard to the large number of samples that were investigated in a short time frame. PMID:23284028

  6. Yersinia enterocolitica in diagnostic fecal samples from European dogs and cats: identification by fourier transform infrared spectroscopy and matrix-assisted laser desorption ionization-time of flight mass spectrometry.

    Science.gov (United States)

    Stamm, Ivonne; Hailer, Mandy; Depner, Barbara; Kopp, Peter A; Rau, Jörg

    2013-03-01

    Yersinia enterocolitica is the main cause of yersiniosis in Europe, one of the five main bacterial gastrointestinal diseases of humans. Beside pigs, companion animals, especially dogs and cats, were repeatedly discussed in the past as a possible source of pathogenic Y. enterocolitica. To investigate the presence and types of Y. enterocolitica in companion animals, a total of 4,325 diagnostic fecal samples from dogs and 2,624 samples from cats were tested. The isolates obtained were differentiated by using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) and Fourier transform infrared spectroscopy (FT-IR). Isolated Y. enterocolitica strains were bioserotyped. The detection of the ail gene by PCR and confirmation by FT-IR were used as a pathogenicity marker. Y. enterocolitica strains were isolated from 198 (4.6%) of the dog and 8 (0.3%) of the cat fecal samples investigated. One hundred seventy-nine isolates from dogs were analyzed in detail. The virulence factor Ail was detected in 91.6% of isolates. Isolates of biotype 4 (54.7%) and, to a lesser extent, biotypes 2 (23.5%), 3 (11.2%), and 5 (2.2%) were detected. The remaining 8.4% of strains belonged to the ail-negative biotype 1A. All 7 isolates from cats that were investigated in detail were ail positive. These results indicate that companion animals could be a relevant reservoir for a broad range of presumptively human-pathogenic Y. enterocolitica types. MALDI-TOF MS and FT-IR proved to be valuable methods for the rapid identification of Y. enterocolitica, especially in regard to the large number of samples that were investigated in a short time frame.

  7. Electrochemically induced reactions in soils - a new approach to the in-situ remediation of contaminated soils?

    Energy Technology Data Exchange (ETDEWEB)

    Rahner, D.; Ludwig, G.; Roehrs, J. [Dresden Univ. of Technology, Inst. of Physical Chemistry and Electrochemistry (Germany); Neumann, V.; Nitsche, C.; Guderitz, I. [Soil and Groundwater Lab. GmbH, Dresden (Germany)

    2001-07-01

    Electrochemical reactions can be induced in soils if the soil matrix contains particles or films with electronic conducting properties ('microconductors'). In these cases the wet soil may act as a 'diluted' electrochemical solid bed reactor. A discussion of this reaction principle within the soil matrix will be presented here. It will be shown, that under certain conditions immobile organic contaminants may be converted. (orig.)

  8. Synthesis of graphene platelets by chemical and electrochemical route

    Energy Technology Data Exchange (ETDEWEB)

    Ramachandran, Rajendran; Felix, Sathiyanathan [Centre for Nanotechnology Research, VIT University, Vellore 632014, Tamil Nadu (India); Joshi, Girish M. [Materials Physics Division, School of Advanced Sciences, VIT University, Vellore 632014, Tamil Nadu (India); Raghupathy, Bala P.C., E-mail: balapraveen2000@yahoo.com [Centre for Nanotechnology Research, VIT University, Vellore 632014, Tamil Nadu (India); Research and Advanced Engineering Division (Materials), Renault Nissan Technology and Business Center India (P) Ltd., Chennai, Tamil Nadu (India); Jeong, Soon Kwan, E-mail: jeongsk@kier.re.kr [Climate Change Technology Research Division, Korea Institute of Energy Research, Yuseong-gu, Daejeon 305-343 (Korea, Republic of); Grace, Andrews Nirmala, E-mail: anirmalagrace@vit.ac.in [Centre for Nanotechnology Research, VIT University, Vellore 632014, Tamil Nadu (India); Climate Change Technology Research Division, Korea Institute of Energy Research, Yuseong-gu, Daejeon 305-343 (Korea, Republic of)

    2013-10-15

    Graphical abstract: A schematic showing the overall reduction process of graphite to reduced graphene platelets by chemical and electrochemical route. - Highlights: • Graphene was prepared by diverse routes viz. chemical and electrochemical methods. • NaBH{sub 4} was effective for removing oxygen functional groups from graphene oxide. • Sodium borohydride reduced graphene oxide (SRGO) showed high specific capacitance. • Electrochemical rendered a cheap route for production of graphene in powder form. - Abstract: Graphene platelets were synthesized from graphene oxide by chemical and electrochemical route. Under the chemical method, sodium borohydride and hydrazine chloride were used as reductants to produce graphene. In this paper, a novel and cost effective electrochemical method, which can simplify the process of reduction on a larger scale, is demonstrated. The electrochemical method proposed in this paper produces graphene in powder form with good yield. The atomic force microscopic images confirmed that the graphene samples prepared by all the routes have multilayers of graphene. The electrochemical process provided a new route to make relatively larger area graphene sheets, which will have interest for further patterning applications. Attempt was made to quantify the quantum of reduction using cyclic voltammetry and choronopotentiometry techniques on reduced graphene samples. As a measure in reading the specific capacitance values, a maximum specific capacitance value of 265.3 F/g was obtained in sodium borohydride reduced graphene oxide.

  9. Synthesis of graphene platelets by chemical and electrochemical route

    International Nuclear Information System (INIS)

    Ramachandran, Rajendran; Felix, Sathiyanathan; Joshi, Girish M.; Raghupathy, Bala P.C.; Jeong, Soon Kwan; Grace, Andrews Nirmala

    2013-01-01

    Graphical abstract: A schematic showing the overall reduction process of graphite to reduced graphene platelets by chemical and electrochemical route. - Highlights: • Graphene was prepared by diverse routes viz. chemical and electrochemical methods. • NaBH 4 was effective for removing oxygen functional groups from graphene oxide. • Sodium borohydride reduced graphene oxide (SRGO) showed high specific capacitance. • Electrochemical rendered a cheap route for production of graphene in powder form. - Abstract: Graphene platelets were synthesized from graphene oxide by chemical and electrochemical route. Under the chemical method, sodium borohydride and hydrazine chloride were used as reductants to produce graphene. In this paper, a novel and cost effective electrochemical method, which can simplify the process of reduction on a larger scale, is demonstrated. The electrochemical method proposed in this paper produces graphene in powder form with good yield. The atomic force microscopic images confirmed that the graphene samples prepared by all the routes have multilayers of graphene. The electrochemical process provided a new route to make relatively larger area graphene sheets, which will have interest for further patterning applications. Attempt was made to quantify the quantum of reduction using cyclic voltammetry and choronopotentiometry techniques on reduced graphene samples. As a measure in reading the specific capacitance values, a maximum specific capacitance value of 265.3 F/g was obtained in sodium borohydride reduced graphene oxide

  10. One-step electrodeposition of Au-Pt bimetallic nanoparticles on MoS2 nanoflowers for hydrogen peroxide enzyme-free electrochemical sensor

    International Nuclear Information System (INIS)

    Zhou, Juan; Zhao, Yanan; Bao, Jing; Huo, Danqun; Fa, Huanbao; Shen, Xin; Hou, Changjun

    2017-01-01

    The rationally designed sensor architecture is very important to improve the sensitivity and selectivity for H 2 O 2 enzyme-free electrochemical sensor. In this work, a sensitive H 2 O 2 biosensor was fabricated by electrochemical deposition of Au-Pt bimetallic nanoparticles (NPs) on molybdenum disulfide nanoflowers (MoS 2 NFs). Au-Pt NPs was dispersed or stabilized by the effective support matrix of MoS 2 nanosheets, which was effectively enhance the conductivity, catalytic performance and long-term stability. The experimental results show that MoS 2 -Au/Pt nanocomposites exhibit excellent catalytic activity for specific detection of H 2 O 2, and electrochemical measurement results show that the enzyme-free electrochemical sensor has large linear range of 10 μM to 19.07 mM with high sensitivity of 142.68 μA mM −1 cm −2 . This novel sensor produced satisfactory reproducibility and stability, and exhibited superior potential for the practical quantitative analysis of H 2 O 2 in serum samples.

  11. Paths correlation matrix.

    Science.gov (United States)

    Qian, Weixian; Zhou, Xiaojun; Lu, Yingcheng; Xu, Jiang

    2015-09-15

    Both the Jones and Mueller matrices encounter difficulties when physically modeling mixed materials or rough surfaces due to the complexity of light-matter interactions. To address these issues, we derived a matrix called the paths correlation matrix (PCM), which is a probabilistic mixture of Jones matrices of every light propagation path. Because PCM is related to actual light propagation paths, it is well suited for physical modeling. Experiments were performed, and the reflection PCM of a mixture of polypropylene and graphite was measured. The PCM of the mixed sample was accurately decomposed into pure polypropylene's single reflection, pure graphite's single reflection, and depolarization caused by multiple reflections, which is consistent with the theoretical derivation. Reflection parameters of rough surface can be calculated from PCM decomposition, and the results fit well with the theoretical calculations provided by the Fresnel equations. These theoretical and experimental analyses verify that PCM is an efficient way to physically model light-matter interactions.

  12. Matrix Effects in XRF Measurements

    International Nuclear Information System (INIS)

    Kandil, A.T.; Gabr, N.A.; El-Aryan, S.M.

    2015-01-01

    This research treats the matrix effect on XRF measurements. The problem is treated by preparing general oxide program, which contains many samples that represent all materials in cement factories, then by using T rail Lachance m ethod to correct errors of matrix effect. This work compares the effect of using lithium tetraborate or sodium tetraborate as a fluxing agent in terms of accuracy and economic cost

  13. Electrochemical Biosensors - Sensor Principles and Architectures

    Science.gov (United States)

    Grieshaber, Dorothee; MacKenzie, Robert; Vörös, Janos; Reimhult, Erik

    2008-01-01

    Quantification of biological or biochemical processes are of utmost importance for medical, biological and biotechnological applications. However, converting the biological information to an easily processed electronic signal is challenging due to the complexity of connecting an electronic device directly to a biological environment. Electrochemical biosensors provide an attractive means to analyze the content of a biological sample due to the direct conversion of a biological event to an electronic signal. Over the past decades several sensing concepts and related devices have been developed. In this review, the most common traditional techniques, such as cyclic voltammetry, chronoamperometry, chronopotentiometry, impedance spectroscopy, and various field-effect transistor based methods are presented along with selected promising novel approaches, such as nanowire or magnetic nanoparticle-based biosensing. Additional measurement techniques, which have been shown useful in combination with electrochemical detection, are also summarized, such as the electrochemical versions of surface plasmon resonance, optical waveguide lightmode spectroscopy, ellipsometry, quartz crystal microbalance, and scanning probe microscopy. The signal transduction and the general performance of electrochemical sensors are often determined by the surface architectures that connect the sensing element to the biological sample at the nanometer scale. The most common surface modification techniques, the various electrochemical transduction mechanisms, and the choice of the recognition receptor molecules all influence the ultimate sensitivity of the sensor. New nanotechnology-based approaches, such as the use of engineered ion-channels in lipid bilayers, the encapsulation of enzymes into vesicles, polymersomes, or polyelectrolyte capsules provide additional possibilities for signal amplification. In particular, this review highlights the importance of the precise control over the delicate

  14. Covalent attachment of aptamer onto nanocomposite as a high performance electrochemical sensing platform: Fabrication of an ultra-sensitive ibuprofen electrochemical aptasensor

    Energy Technology Data Exchange (ETDEWEB)

    Roushani, Mahmoud, E-mail: mahmoudroushani@yahoo.com; Shahdost-fard, Faezeh

    2016-11-01

    In the present study, we report a selective electrochemical aptasensor for the ultrasensitive detection of an anti-inflammatory drug, ibuprofen (IBP). The proposed system was achieved by the modification of a glassy carbon electrode (GCE) with multiwalled carbon nanotubes/ionic liquid/chitosan (MWCNTs/IL/Chit) nanocomposite and the covalent immobilization of the IBP specific aptamer (Apt) onto the modified electrode surface followed by methylene blue (MB) intercalated onto the Apt as the electrochemical redox marker. Upon the incubation of the IBP as a target in the proposed aptasensor, the peak current of MB decreases due to the formation of the Apt-IBP complex and the displacement of MB from the immobilized Apt onto the modified electrode surface. The nanocomposite not only increases the electrode surface area and accelerate the electron transfer kinetics but also it provides a highly stable matrix to enhance the loading amount of the Apt DNA sequence. Through differential pulse voltammetry (DPV) experiments, it was found that the proposed aptasensor could detect the IBP with a linear range (70 pM up to 6 μM) and the detection limit (LOD) as low as 20 pM. The results showed that the aptasensor had good sensitivity, stability, reproducibility, and specificity to detect the IBP. The proposed aptasensor was successfully applied for measuring the IBP concentration in real samples. Based on our experiments we can say that the present method proposes new horizons for the development of other aptasensors for diagnostic application in biosensing. - Highlights: • An electrochemical aptasensor is developed for ultrasensitive detection of IBP. • The aptasensor is made by covalent immobilization of aptamer on a modified GCE. • A nanocomposite as a modifier provides a specific surface with high conductivity. • This nanocomposite leads to a high density of the DNA sequence on the GCE surface. • This method proposes new horizons for development other aptasensors for

  15. Covalent attachment of aptamer onto nanocomposite as a high performance electrochemical sensing platform: Fabrication of an ultra-sensitive ibuprofen electrochemical aptasensor

    International Nuclear Information System (INIS)

    Roushani, Mahmoud; Shahdost-fard, Faezeh

    2016-01-01

    In the present study, we report a selective electrochemical aptasensor for the ultrasensitive detection of an anti-inflammatory drug, ibuprofen (IBP). The proposed system was achieved by the modification of a glassy carbon electrode (GCE) with multiwalled carbon nanotubes/ionic liquid/chitosan (MWCNTs/IL/Chit) nanocomposite and the covalent immobilization of the IBP specific aptamer (Apt) onto the modified electrode surface followed by methylene blue (MB) intercalated onto the Apt as the electrochemical redox marker. Upon the incubation of the IBP as a target in the proposed aptasensor, the peak current of MB decreases due to the formation of the Apt-IBP complex and the displacement of MB from the immobilized Apt onto the modified electrode surface. The nanocomposite not only increases the electrode surface area and accelerate the electron transfer kinetics but also it provides a highly stable matrix to enhance the loading amount of the Apt DNA sequence. Through differential pulse voltammetry (DPV) experiments, it was found that the proposed aptasensor could detect the IBP with a linear range (70 pM up to 6 μM) and the detection limit (LOD) as low as 20 pM. The results showed that the aptasensor had good sensitivity, stability, reproducibility, and specificity to detect the IBP. The proposed aptasensor was successfully applied for measuring the IBP concentration in real samples. Based on our experiments we can say that the present method proposes new horizons for the development of other aptasensors for diagnostic application in biosensing. - Highlights: • An electrochemical aptasensor is developed for ultrasensitive detection of IBP. • The aptasensor is made by covalent immobilization of aptamer on a modified GCE. • A nanocomposite as a modifier provides a specific surface with high conductivity. • This nanocomposite leads to a high density of the DNA sequence on the GCE surface. • This method proposes new horizons for development other aptasensors for

  16. Electrochemical Detection with Preconcentration: Nitroenergetic Contaminants

    Directory of Open Access Journals (Sweden)

    Brandy J. Johnson

    2014-06-01

    Full Text Available This effort evaluated the potential of two prototype devices for enhanced electrochemical detection of 2,4,6-trinitrotoluene (TNT and dinitrotoluene (DNT following preconcentration using an organosilicate sorbent. The bench-scale prototype provides adsorption of the targets from aqueous solution followed by elution in a mixture of methanol and potassium chloride (KCl. Following elution, the eluant is diluted using an aqueous KCl solution to provide sufficient electrolyte for electrochemical analysis. Concentrations of methanol greater than 50% were detrimental to sensor performance and lifetime. Calibration of the electrochemical sensor was completed and results of electrochemical analysis were compared to those of HPLC analysis over a range of concentrations and in varied matrices. TNT detection was found to be consistent and detection limits were improved from 200 ppb to 3 ppb depending on the sample volume utilized. DNT detection showed higher variability and significantly greater false response rates. On the basis of these results, a second, more advanced, prototype was developed and utilized in limited field trials with the intention of moving the technology toward in situ applications.

  17. Electrochemical characteristics of polyacetylene in organic electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Padula, A.; Scrosati, B.

    1985-01-15

    The characteristics of the electrochemical doping process of polyacetylene have been investigated in lithium cells using lithium perchlorate in propylene carbonate as electrolytic solution. The kinetics of this process are controlled by the diffusion of the dopant species throughout the polymer. Therefore, polyacetylene samples with a highly porous, extended surface should be selected for the development of efficient, rechargeable lithium batteries. In line with this, we have considered foam-type polyacetylene electrodes which have a lower density than the 'classical' Shirakawa-type film electrodes. The electrochemical behaviour of the polyacetylene foam samples has been examined by cyclic voltametry response and constant current, charge-discharge cycles. The results are described in this work.

  18. Molybdenum carbide-carbon nanocomposites synthesized from a reactive template for electrochemical hydrogen evolution

    KAUST Repository

    Alhajri, Nawal Saad

    2014-01-01

    Molybdenum carbide nanocrystals (Mo2C) with sizes ranging from 3 to 20 nm were synthesized within a carbon matrix starting from a mesoporous graphitic carbon nitride (mpg-C3N4) template with confined pores. A molybdenum carbide phase (Mo2C) with a hexagonal structure was formed using a novel synthetic method involving the reaction of a molybdenum precursor with the carbon residue originating from C3N4 under nitrogen at various temperatures. The synthesized nanocomposites were characterized using powder X-ray diffraction (XRD), temperature-programmed reaction with mass spectroscopy (MS), CHN elemental analyses, thermogravimetric analyses (TGA), nitrogen sorption, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The results indicated that the synthesized samples have different surface structures and compositions, which are accordingly expected to exhibit different electrocatalytic activities toward the hydrogen evolution reaction (HER). Electrochemical measurements demonstrated that the sample synthesized at 1323 K exhibited the highest and most stable HER current in acidic media, with an onset potential of -100 mV vs. RHE, among the samples prepared in this study. This result is attributed to the sufficiently small particle size (∼8 nm on average) and accordingly high surface area (308 m2 g-1), with less oxidized surface entrapped within the graphitized carbon matrix. © 2014 the Partner Organisations.

  19. Fabrication and application of a new modified electrochemical sensor using nano-silica and a newly synthesized Schiff base for simultaneous determination of Cd{sup 2+}, Cu{sup 2+} and Hg{sup 2+} ions in water and some foodstuff samples

    Energy Technology Data Exchange (ETDEWEB)

    Afkhami, Abbas, E-mail: afkhami@basu.ac.ir [Faculty of Chemistry, Bu-Ali Sina University, Hamedan (Iran, Islamic Republic of); Soltani-Felehgari, Farzaneh; Madrakian, Tayyebeh; Ghaedi, Hamed [Faculty of Chemistry, Bu-Ali Sina University, Hamedan (Iran, Islamic Republic of); Rezaeivala, Majid [Department of Chemical Engineering, Hamedan University of Technology, Hamedan (Iran, Islamic Republic of)

    2013-04-10

    Highlights: ► A new modified electrochemical sensor was constructed and used. ► A new Schiff base coated nano-silica was used as modifier. ► The electrochemical properties of electrode were studied. ► This modifier enhanced the electrochemical properties of electrode. ► The electrode was used for simultaneous determination of Cd{sup 2+}, Cu{sup 2+} and Hg{sup 2+} ions. -- Abstract: A new chemically modified carbon paste electrode was constructed and used for rapid, simple, accurate, selective and highly sensitive simultaneous determination of cadmium, copper and mercury using square wave anodic stripping voltammetry (SWASV). The carbon paste electrode was modified by N,N′-bis(3-(2-thenylidenimino)propyl)piperazine coated silica nanoparticles. Compared with carbon paste electrode, the stripping peak currents had a significant increase at the modified electrode. Under the optimized conditions (deposition potential, −1.100 V vs. Ag/AgCl; deposition time, 60 s; resting time, 10 s; SW frequency, 25 Hz; pulse amplitude, 0.15 V; dc voltage step height, 4.4 mV), the detection limit was 0.3, 0.1 and 0.05 ng mL{sup −1} for the determination of Cd{sup 2+}, Cu{sup 2+} and Hg{sup 2+}, respectively. The complexation reaction of the ligand with several metal cations in methanol was studied and the stability constants of the complexes were obtained. The effects of different cations and anions on the simultaneous determination of metal ions were studied and it was found that the electrode is highly selective for the simultaneous determination of Cd{sup 2+}, Cu{sup 2+} and Hg{sup 2+}. Furthermore, the present method was applied to the determination of Cd{sup 2+}, Cu{sup 2+} and Hg{sup 2+} in water and some foodstuff samples.

  20. Determinação de corantes marcadores do tipo azo e antraquinona em combustíveis por cromatografia líquida com detecção eletroquímica Determination of azo and anthraquinone dyes in fuels sample using hplc with electrochemical detection

    Directory of Open Access Journals (Sweden)

    Magno Aparecido Gonçalves Trindade

    2010-01-01

    Full Text Available An analytical method based on high-performance liquid chromatography with electrochemical detection has been developed and applied to the determination of Solvent blue 14 (SA-14 and Solvent red 24 (SV-24 in fuel samples. The dyes were better separated on C18 column, using a mobile phase composed of acetonitrile and ammonium acetate (90:10, v/v. Detection was carried out at an oxidation potential of +0.85V. The detector response was linear at concentration range of 7.50×10-8 - 1.50×10-6 mol L-1 (r = 0.997 for SA-14 and SV-24, respectively. The method was used to quantify these dyes in fuels samples with satisfactory accuracy and precision.

  1. Polarization Behavior of Squeeze Cast Al2O3 Fiber Reinforced Aluminum Matrix Composites

    International Nuclear Information System (INIS)

    Ham, S. H.; Kang, Y. C.; Cho, K. M.; Park, I. M.

    1992-01-01

    Electrochemical polarization behavior of squeeze cast Al 2 O 3 short fiber reinforced Al alloy matrix composites was investigated for the basic understanding of the corrosion properties of the composites. The composites were fabricated with variations of fiber volume fraction and matrix alloys. It was found that the reinforced composites are more susceptible to corrosion attack than the unreinforced matrix alloys in general. Corrosion resistance shows decreasing tendency with increasing Al 2 O 3 fiber volume fraction in AC8A matrix. Effect of the matrix alloys revealed that the AC8A Al matrix composite is less susceptible to corrosion attack than the 2024 and 7075 Al matrix composites. Effect of plastic deformation on electrochemical polarization behavior of the squeeze cast Al/Al 2 O 3 composites was examined after extrusion of AC8A-10v/o Al 2 O 3 . Result shows that corrosion resistance is deteriorated after plastic deformation

  2. Fungal nanoscale metal carbonates and production of electrochemical materials.

    Science.gov (United States)

    Li, Qianwei; Gadd, Geoffrey Michael

    2017-09-01

    Fungal biomineralization of carbonates results in metal removal from solution or immobilization within a solid matrix. Such a system provides a promising method for removal of toxic or valuable metals from solution, such as Co, Ni, and La, with some carbonates being of nanoscale dimensions. A fungal Mn carbonate biomineralization process can be applied for the synthesis of novel electrochemical materials. © 2017 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology.

  3. Electrochemical Sensors for Clinic Analysis

    Directory of Open Access Journals (Sweden)

    Guang Li

    2008-03-01

    Full Text Available Demanded by modern medical diagnosis, advances in microfabrication technology have led to the development of fast, sensitive and selective electrochemical sensors for clinic analysis. This review addresses the principles behind electrochemical sensor design and fabrication, and introduces recent progress in the application of electrochemical sensors to analysis of clinical chemicals such as blood gases, electrolytes, metabolites, DNA and antibodies, including basic and applied research. Miniaturized commercial electrochemical biosensors will form the basis of inexpensive and easy to use devices for acquiring chemical information to bring sophisticated analytical capabilities to the non-specialist and general public alike in the future.

  4. Synthesis and electrochemical properties of tin oxide-based composite by rheological technique

    International Nuclear Information System (INIS)

    He Zeqiang; Li Xinhai; Xiong Lizhi; Wu Xianming; Xiao Zhuobing; Ma Mingyou

    2005-01-01

    Novel rheological technique was developed to synthesize tin oxide-based composites. The microstructure, morphology, and electrochemical performance of the materials were investigated by X-ray diffraction, scanning electron microscopy and electrochemical methods. The particles of tin oxide-based materials form an inactive matrix. The average size of the particles is about 150 nm. The material delivers a charge capacity of more than 570 mAh g -1 . The capacity loss per cycle is about 0.15% after being cycled 30 times. The good electrochemical performance indicates that this kind of tin oxide-based material is promising anode for lithium-ion battery

  5. Direct electrochemical reduction of solid uranium oxide in molten fluoride salts

    Science.gov (United States)

    Gibilaro, Mathieu; Cassayre, Laurent; Lemoine, Olivier; Massot, Laurent; Dugne, Olivier; Malmbeck, Rikard; Chamelot, Pierre

    2011-07-01

    The direct electrochemical reduction of UO 2 solid pellets was carried out in LiF-CaF 2 (+2 mass.% Li 2O) at 850 °C. An inert gold anode was used instead of the usual reactive sacrificial carbon anode. In this case, oxidation of oxide ions present in the melt yields O 2 gas evolution on the anode. Electrochemical characterisations of UO 2 pellets were performed by linear sweep voltammetry at 10 mV/s and reduction waves associated to oxide direct reduction were observed at a potential 150 mV more positive in comparison to the solvent reduction. Subsequent, galvanostatic electrolyses runs were carried out and products were characterised by SEM-EDX, EPMA/WDS, XRD and microhardness measurements. In one of the runs, uranium oxide was partially reduced and three phases were observed: nonreduced UO 2 in the centre, pure metallic uranium on the external layer and an intermediate phase representing the initial stage of reduction taking place at the grain boundaries. In another run, the UO 2 sample was fully reduced. Due to oxygen removal, the U matrix had a typical coral-like structure which is characteristic of the pattern observed after the electroreduction of solid oxides.

  6. Aptamer/quantum dot-based simultaneous electrochemical detection of multiple small molecules

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Haixia [Key Laboratory on Luminescence and Real-Time Analysis, Ministry of Education, School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China); Jiang Bingying [School of Chemistry and Chemical Engineering, Chongqing University of Technology, Chongqing 400040 (China); Xiang Yun, E-mail: yunatswu@swu.edu.cn [Key Laboratory on Luminescence and Real-Time Analysis, Ministry of Education, School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China); Zhang Yuyong; Chai Yaqin [Key Laboratory on Luminescence and Real-Time Analysis, Ministry of Education, School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China); Yuan Ruo, E-mail: yuanruo@swu.edu.cn [Key Laboratory on Luminescence and Real-Time Analysis, Ministry of Education, School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China)

    2011-03-04

    A novel strategy for 'signal on' and sensitive one-spot simultaneous detection of multiple small molecular analytes based on electrochemically encoded barcode quantum dot (QD) tags is described. The target analytes, adenosine triphosphate (ATP) and cocaine, respectively, are sandwiched between the corresponding set of surface-immobilized primary binding aptamers and the secondary binding aptamer/QD bioconjugates. The captured QDs yield distinct electrochemical signatures after acid dissolution, whose position and size reflect the identity and level, respectively, of the corresponding target analytes. Due to the inherent amplification feature of the QD labels and the 'signal on' detection scheme, as well as the sensitive monitoring of the metal ions released upon acid dissolution of the QD labels, low detection limits of 30 nM and 50 nM were obtained for ATP and cocaine, respectively, in our assays. Our multi-analyte sensing system also shows high specificity to target analytes and promising applicability to complex sample matrix, which makes the proposed assay protocol an attractive route for screening of small molecules in clinical diagnosis.

  7. Assessment of Copper, Cadmium and Lead in Organical Matrix

    International Nuclear Information System (INIS)

    Gutierrez, Ariel

    2000-08-01

    In this report the electrochemical method of differential pulse anode voltametry redisolution voltametry is used to quantitative assessment of copper, cadmium and lead in solution. The methodology is described in the preparation of samples for measurement

  8. Electrochemical destruction of nitrosamines

    Energy Technology Data Exchange (ETDEWEB)

    Lejen, T; Volchek, K; Ladanowski, C; Velicogna, D; Whittaker, H [Environment Canada, Ottawa, ON (Canada). Emergencies Engineering Div.

    1996-09-01

    Treatment conditions for the electrolytic destruction of nitrosamines were studied. The joint investigation between Canada and the Ukraine was part of an assessment of hazardous contaminants at former Soviet ICBM missile sites. The electrochemical destruction of N-dimethylnitrosamines (NDMA) on carbon/platinum electrodes was studied under basic and acidic conditions by UV spectroscopy, gas chromatography, mass spectroscopy, and colorimetry. Experiments with a 100 ppm NDMA solution showed that electrolytic-reduction was pH sensitive within a range of pH 0.5 to 4.0. Electrolysis was effective for the reduction of NDMA in strong acidic conditions. 30 refs., 1 tab., 4 figs.

  9. Electrochemical Science and Technology

    CERN Document Server

    Oldham, Keith; Bond, Alan

    2011-01-01

    The book addresses the scientific principles underlying electrochemistry. Starting with the basic concepts of electricity, the early chapters discuss the physics and chemistry of the materials from which electrochemical cells are constructed and the properties that make these materials appropriate as cell components. Much of the importance of electrochemistry lies in the conversion of electrical energy into chemical energy and vice versa; the thermodynamics of these processes is described, in the context of a wide range of applications of these interconversions. An electrode is a surface at wh

  10. Electrochemical Detection in Stacked Paper Networks.

    Science.gov (United States)

    Liu, Xiyuan; Lillehoj, Peter B

    2015-08-01

    Paper-based electrochemical biosensors are a promising technology that enables rapid, quantitative measurements on an inexpensive platform. However, the control of liquids in paper networks is generally limited to a single sample delivery step. Here, we propose a simple method to automate the loading and delivery of liquid samples to sensing electrodes on paper networks by stacking multiple layers of paper. Using these stacked paper devices (SPDs), we demonstrate a unique strategy to fully immerse planar electrodes by aqueous liquids via capillary flow. Amperometric measurements of xanthine oxidase revealed that electrochemical sensors on four-layer SPDs generated detection signals up to 75% higher compared with those on single-layer paper devices. Furthermore, measurements could be performed with minimal user involvement and completed within 30 min. Due to its simplicity, enhanced automation, and capability for quantitative measurements, stacked paper electrochemical biosensors can be useful tools for point-of-care testing in resource-limited settings. © 2015 Society for Laboratory Automation and Screening.

  11. Electrochemical aptasensor for detecting tetracycline in milk

    International Nuclear Information System (INIS)

    Le, Thi Hanh; Pham, Van Phuc; La, Thi Huyen; Le, Quang Huan; Phan, Thi Binh

    2016-01-01

    A rapid, simple and sensitive biosensor system for tetracycline detection is very important in food safety. In this paper we developed a label-free aptasensor for electrochemical detection of tetracycline. According to the electrochemical impendence spectroscopy (EIS) analysis, there was a linear relationship between the concentration of tetracycline and the electron transfer resistance from 10 to 3000 ng ml −1 of the tetracycline concentration. The detection limit was 10 ng ml −1 in 15 min detection duration. The prepared aptasensor showed a good reproducibility with an acceptable stability in tetracycline detection. The recoveries of tetracycline in spiked milk samples were in the range of 88.1%–94.2%. The aptasensor has sensitivity 98% and specificity of 100%. (paper)

  12. Comparison of three-way and four-way calibration for the real-time quantitative analysis of drug hydrolysis in complex dynamic samples by excitation-emission matrix fluorescence.

    Science.gov (United States)

    Yin, Xiao-Li; Gu, Hui-Wen; Liu, Xiao-Lu; Zhang, Shan-Hui; Wu, Hai-Long

    2018-03-05

    Multiway calibration in combination with spectroscopic technique is an attractive tool for online or real-time monitoring of target analyte(s) in complex samples. However, how to choose a suitable multiway calibration method for the resolution of spectroscopic-kinetic data is a troubling problem in practical application. In this work, for the first time, three-way and four-way fluorescence-kinetic data arrays were generated during the real-time monitoring of the hydrolysis of irinotecan (CPT-11) in human plasma by excitation-emission matrix fluorescence. Alternating normalization-weighted error (ANWE) and alternating penalty trilinear decomposition (APTLD) were used as three-way calibration for the decomposition of the three-way kinetic data array, whereas alternating weighted residual constraint quadrilinear decomposition (AWRCQLD) and alternating penalty quadrilinear decomposition (APQLD) were applied as four-way calibration to the four-way kinetic data array. The quantitative results of the two kinds of calibration models were fully compared from the perspective of predicted real-time concentrations, spiked recoveries of initial concentration, and analytical figures of merit. The comparison study demonstrated that both three-way and four-way calibration models could achieve real-time quantitative analysis of the hydrolysis of CPT-11 in human plasma under certain conditions. However, it was also found that both of them possess some critical advantages and shortcomings during the process of dynamic analysis. The conclusions obtained in this paper can provide some helpful guidance for the reasonable selection of multiway calibration models to achieve the real-time quantitative analysis of target analyte(s) in complex dynamic systems. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Comparison of three-way and four-way calibration for the real-time quantitative analysis of drug hydrolysis in complex dynamic samples by excitation-emission matrix fluorescence

    Science.gov (United States)

    Yin, Xiao-Li; Gu, Hui-Wen; Liu, Xiao-Lu; Zhang, Shan-Hui; Wu, Hai-Long

    2018-03-01

    Multiway calibration in combination with spectroscopic technique is an attractive tool for online or real-time monitoring of target analyte(s) in complex samples. However, how to choose a suitable multiway calibration method for the resolution of spectroscopic-kinetic data is a troubling problem in practical application. In this work, for the first time, three-way and four-way fluorescence-kinetic data arrays were generated during the real-time monitoring of the hydrolysis of irinotecan (CPT-11) in human plasma by excitation-emission matrix fluorescence. Alternating normalization-weighted error (ANWE) and alternating penalty trilinear decomposition (APTLD) were used as three-way calibration for the decomposition of the three-way kinetic data array, whereas alternating weighted residual constraint quadrilinear decomposition (AWRCQLD) and alternating penalty quadrilinear decomposition (APQLD) were applied as four-way calibration to the four-way kinetic data array. The quantitative results of the two kinds of calibration models were fully compared from the perspective of predicted real-time concentrations, spiked recoveries of initial concentration, and analytical figures of merit. The comparison study demonstrated that both three-way and four-way calibration models could achieve real-time quantitative analysis of the hydrolysis of CPT-11 in human plasma under certain conditions. However, it was also found that both of them possess some critical advantages and shortcomings during the process of dynamic analysis. The conclusions obtained in this paper can provide some helpful guidance for the reasonable selection of multiway calibration models to achieve the real-time quantitative analysis of target analyte(s) in complex dynamic systems.

  14. Electrochemical photovoltaic cells and electrodes

    Science.gov (United States)

    Skotheim, Terje A.

    1984-01-01

    Improved electrochemical photovoltaic cells and electrodes for use therein, particularly electrodes employing amorphous silicon or polyacetylene coating are produced by a process which includes filling pinholes or porous openings in the coatings by electrochemical oxidation of selected monomers to deposit insulating polymer in the openings.

  15. Thermodynamics of irreversible electrochemical phenomena

    NARCIS (Netherlands)

    Groot, S.R. de; Mazur, P.; Tolhoek, H.A.

    1953-01-01

    A discussion from first principles is given of the energy and entropy laws in electrochemical systems. It is found that it is possible to clarify such controversial concepts as the form of the second law and the role of the electrochemical potential in the systems concerned.

  16. Electrochemical biosensors for hormone analyses.

    Science.gov (United States)

    Bahadır, Elif Burcu; Sezgintürk, Mustafa Kemal

    2015-06-15

    Electrochemical biosensors have a unique place in determination of hormones due to simplicity, sensitivity, portability and ease of operation. Unlike chromatographic techniques, electrochemical techniques used do not require pre-treatment. Electrochemical biosensors are based on amperometric, potentiometric, impedimetric, and conductometric principle. Amperometric technique is a commonly used one. Although electrochemical biosensors offer a great selectivity and sensitivity for early clinical analysis, the poor reproducible results, difficult regeneration steps remain primary challenges to the commercialization of these biosensors. This review summarizes electrochemical (amperometric, potentiometric, impedimetric and conductometric) biosensors for hormone detection for the first time in the literature. After a brief description of the hormones, the immobilization steps and analytical performance of these biosensors are summarized. Linear ranges, LODs, reproducibilities, regenerations of developed biosensors are compared. Future outlooks in this area are also discussed. Copyright © 2014 Elsevier B.V. All rights reserved.

  17. Optimized Projection Matrix for Compressive Sensing

    Directory of Open Access Journals (Sweden)

    Jianping Xu

    2010-01-01

    Full Text Available Compressive sensing (CS is mainly concerned with low-coherence pairs, since the number of samples needed to recover the signal is proportional to the mutual coherence between projection matrix and sparsifying matrix. Until now, papers on CS always assume the projection matrix to be a random matrix. In this paper, aiming at minimizing the mutual coherence, a method is proposed to optimize the projection matrix. This method is based on equiangular tight frame (ETF design because an ETF has minimum coherence. It is impossible to solve the problem exactly because of the complexity. Therefore, an alternating minimization type method is used to find a feasible solution. The optimally designed projection matrix can further reduce the necessary number of samples for recovery or improve the recovery accuracy. The proposed method demonstrates better performance than conventional optimization methods, which brings benefits to both basis pursuit and orthogonal matching pursuit.

  18. An electrochemical sensor for gallic acid based on Fe2O3/electro-reduced graphene oxide composite: Estimation for the antioxidant capacity index of wines

    International Nuclear Information System (INIS)

    Gao, Feng; Zheng, Delun; Tanaka, Hidekazu; Zhan, Fengping; Yuan, Xiaoning; Gao, Fei; Wang, Qingxiang

    2015-01-01

    A highly sensitive electrochemical sensor for gallic acid (GA), an important polyphenolic compound, was fabricated using the hybrid material of chitosan (CS), fishbone-shaped Fe 2 O 3 (fFe 2 O 3 ), and electrochemically reduced graphene oxide (ERGO) as the sensing matrix. The electrochemical characterization experiments showed that the CS–fFe 2 O 3 –ERGO modified glassy carbon electrode (CS–fFe 2 O 3 –ERGO/GCE) had large surface area, excellent electronic conductivity and high stability. The GA presented a superior electrochemical response on CS–fFe 2 O 3 –ERGO/GCE in comparison with the single-component modified electrode. The electrochemical mechanism and optimal test conditions of GA on the electrode surface were carefully investigated. Under the optimal conditions, the oxidation peak currents in differential pulse voltammetry (DPV) experiments exhibited a good linear relationship with the logarithmic values of GA concentration over the range from 1.0 × 10 −6 M to 1.0 × 10 −4 M. Based on signal-to-noise (S/N) characteristic of 3, the detection limit was estimated to be 1.5 × 10 −7 M. The proposed sensor has also been applied for estimating the antioxidant capacity index of real samples of red and white wines. - Highlights: • Fishbone-shaped Fe 2 O 3 (fFe 2 O 3 ) nanoparticles were synthesized by a simple template-free solvothermal method. • The nanocomposite of fFe 2 O 3 , graphene and chitosan was used as the sensing platform for gallic acid. • The sensor shows a wide linear range and low detection limit for gallic acid. • The antioxidant capacity index of wines was successfully evaluated by the sensor

  19. Zinc oxide nanostructures for electrochemical cortisol biosensing

    Science.gov (United States)

    Vabbina, Phani Kiran; Kaushik, Ajeet; Tracy, Kathryn; Bhansali, Shekhar; Pala, Nezih

    2014-05-01

    In this paper, we report on fabrication of a label free, highly sensitive and selective electrochemical cortisol immunosensors using one dimensional (1D) ZnO nanorods (ZnO-NRs) and two dimensional nanoflakes (ZnO-NFs) as immobilizing matrix. The synthesized ZnO nanostructures (NSs) were characterized using scanning electron microscopy (SEM), selective area diffraction (SAED) and photoluminescence spectra (PL) which showed that both ZnO-NRs and ZnO-NFs are single crystalline and oriented in [0001] direction. Anti-cortisol antibody (Anti-Cab) are used as primary capture antibodies to detect cortisol using electrochemical impedance spectroscopy (EIS). The charge transfer resistance increases linearly with increase in cortisol concentration and exhibits a sensitivity of 3.078 KΩ. M-1 for ZnO-NRs and 540 Ω. M -1 for ZnO-NFs. The developed ZnO-NSs based immunosensor is capable of detecting cortisol at 1 pM. The observed sensing parameters are in physiological range. The developed sensors can be integrated with microfluidic system and miniaturized potentiostat to detect cortisol at point-of-care.

  20. Covariance matrix estimation for stationary time series

    OpenAIRE

    Xiao, Han; Wu, Wei Biao

    2011-01-01

    We obtain a sharp convergence rate for banded covariance matrix estimates of stationary processes. A precise order of magnitude is derived for spectral radius of sample covariance matrices. We also consider a thresholded covariance matrix estimator that can better characterize sparsity if the true covariance matrix is sparse. As our main tool, we implement Toeplitz [Math. Ann. 70 (1911) 351–376] idea and relate eigenvalues of covariance matrices to the spectral densities or Fourier transforms...

  1. Challenging genosensors in food samples: The case of gluten determination in highly processed samples.

    Science.gov (United States)

    Martín-Fernández, Begoña; de-los-Santos-Álvarez, Noemí; Martín-Clemente, Juan Pedro; Lobo-Castañón, María Jesús; López-Ruiz, Beatriz

    2016-01-01

    Electrochemical genosensors have undergone an enormous development in the last decades, but only very few have achieved a quantification of target content in highly processed food samples. The detection of allergens, and particularly gluten, is challenging because legislation establishes a threshold of 20 ppm for labeling as gluten-free but most genosensors expresses the results in DNA concentration or DNA copies. This paper describes the first attempt to correlate the genosensor response and the wheat content in real samples, even in the case of highly processed food samples. A sandwich-based format, comprising a capture probe immobilized onto the screen-printed gold electrode, and a signaling probe functionalized with fluorescein isothiocyanate (FITC), both hybridizing with the target was used. The hybridization event was electrochemically monitored by adding an anti-FITC peroxidase (antiFITC-HRP) and its substrate, tetramethylbenzidine. Binary model mixtures, as a reference material, and real samples have been analyzed. DNA from food was extracted and a fragment encoding the immunodominant peptide of α2-gliadin amplified by a tailored PCR. The sensor was able to selectively detect toxic cereals for celiac patients, such as different varieties of wheat, barley, rye and oats, from non-toxic plants. As low as 0.001% (10 mg/kg) of wheat flour in an inert matrix was reliably detected, which directly compete with the current method of choice for DNA detection, the real-time PCR. A good correlation with the official immunoassay was found in highly processed food samples. Copyright © 2015 Elsevier B.V. All rights reserved.

  2. Electrochemical hydrogen Storage Systems

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Digby Macdonald

    2010-08-09

    As the global need for energy increases, scientists and engineers have found a possible solution by using hydrogen to power our world. Although hydrogen can be combusted as a fuel, it is considered an energy carrier for use in fuel cells wherein it is consumed (oxidized) without the production of greenhouse gases and produces electrical energy with high efficiency. Chemical storage of hydrogen involves release of hydrogen in a controlled manner from materials in which the hydrogen is covalently bound. Sodium borohydride and aminoborane are two materials given consideration as chemical hydrogen storage materials by the US Department of Energy. A very significant barrier to adoption of these materials as hydrogen carriers is their regeneration from 'spent fuel,' i.e., the material remaining after discharge of hydrogen. The U.S. Department of Energy (DOE) formed a Center of Excellence for Chemical Hydrogen Storage, and this work stems from that project. The DOE has identified boron hydrides as being the main compounds of interest as hydrogen storage materials. The various boron hydrides are then oxidized to release their hydrogen, thereby forming a 'spent fuel' in the form of a lower boron hydride or even a boron oxide. The ultimate goal of this project is to take the oxidized boron hydrides as the spent fuel and hydrogenate them back to their original form so they can be used again as a fuel. Thus this research is essentially a boron hydride recycling project. In this report, research directed at regeneration of sodium borohydride and aminoborane is described. For sodium borohydride, electrochemical reduction of boric acid and sodium metaborate (representing spent fuel) in alkaline, aqueous solution has been investigated. Similarly to literature reports (primarily patents), a variety of cathode materials were tried in these experiments. Additionally, approaches directed at overcoming electrostatic repulsion of borate anion from the cathode, not

  3. Electrochemical hydrogen Storage Systems

    International Nuclear Information System (INIS)

    Macdonald, Digby

    2010-01-01

    As the global need for energy increases, scientists and engineers have found a possible solution by using hydrogen to power our world. Although hydrogen can be combusted as a fuel, it is considered an energy carrier for use in fuel cells wherein it is consumed (oxidized) without the production of greenhouse gases and produces electrical energy with high efficiency. Chemical storage of hydrogen involves release of hydrogen in a controlled manner from materials in which the hydrogen is covalently bound. Sodium borohydride and aminoborane are two materials given consideration as chemical hydrogen storage materials by the US Department of Energy. A very significant barrier to adoption of these materials as hydrogen carriers is their regeneration from 'spent fuel,' i.e., the material remaining after discharge of hydrogen. The U.S. Department of Energy (DOE) formed a Center of Excellence for Chemical Hydrogen Storage, and this work stems from that project. The DOE has identified boron hydrides as being the main compounds of interest as hydrogen storage materials. The various boron hydrides are then oxidized to release their hydrogen, thereby forming a 'spent fuel' in the form of a lower boron hydride or even a boron oxide. The ultimate goal of this project is to take the oxidized boron hydrides as the spent fuel and hydrogenate them back to their original form so they can be used again as a fuel. Thus this research is essentially a boron hydride recycling project. In this report, research directed at regeneration of sodium borohydride and aminoborane is described. For sodium borohydride, electrochemical reduction of boric acid and sodium metaborate (representing spent fuel) in alkaline, aqueous solution has been investigated. Similarly to literature reports (primarily patents), a variety of cathode materials were tried in these experiments. Additionally, approaches directed at overcoming electrostatic repulsion of borate anion from the cathode, not described in the

  4. Electrochemical behavior of pitch-based activated carbon fibers for electrochemical capacitors

    International Nuclear Information System (INIS)

    Lee, Hye-Min; Kwac, Lee-Ku; An, Kay-Hyeok; Park, Soo-Jin; Kim, Byung-Joo

    2016-01-01

    Highlights: • Electrode materials for electrochemical capacitors were developed using pitch-based activated carbon fibers with steam activation. • Activated carbon fibers showed enhanced specific surface area from 1520 to 3230 m 2 /g. • The increase in the specific capacitance of the samples was determined by charged pore structure during charging and discharging. - Abstract: In the present study, electrode materials for electrochemical capacitors were developed using pitch-based activated carbon fibers with steam activation. The surface and structural characteristics of activated carbon fibers were observed using scanning electron microscopy and X-ray diffraction, respectively. Pore characteristics were investigated using N 2 /77 K adsorption isotherms. The activated carbon fibers were applied as electrodes for electrical double-layer capacitors and analyzed in relation to the activation time. The specific surface area and total pore volume of the activated carbon fibers were determined to be 1520–3230 m 2 /g and 0.61–1.87 cm 3 /g, respectively. In addition, when the electrochemical characteristics were analyzed, the specific capacitance was confirmed to have increased from 1.1 F/g to 22.5 F/g. From these results, it is clear that the pore characteristics of pitch-based activated carbon fibers changed considerably in relation to steam activation and charge/discharge cycle; therefore, it was possible to improve the electrochemical characteristics of the activated carbon fibers.

  5. Efficiency criterion for teleportation via channel matrix, measurement matrix and collapsed matrix

    Directory of Open Access Journals (Sweden)

    Xin-Wei Zha

    Full Text Available In this paper, three kinds of coefficient matrixes (channel matrix, measurement matrix, collapsed matrix associated with the pure state for teleportation are presented, the general relation among channel matrix, measurement matrix and collapsed matrix is obtained. In addition, a criterion for judging whether a state can be teleported successfully is given, depending on the relation between the number of parameter of an unknown state and the rank of the collapsed matrix. Keywords: Channel matrix, Measurement matrix, Collapsed matrix, Teleportation

  6. Extended biorthogonal matrix polynomials

    Directory of Open Access Journals (Sweden)

    Ayman Shehata

    2017-01-01

    Full Text Available The pair of biorthogonal matrix polynomials for commutative matrices were first introduced by Varma and Tasdelen in [22]. The main aim of this paper is to extend the properties of the pair of biorthogonal matrix polynomials of Varma and Tasdelen and certain generating matrix functions, finite series, some matrix recurrence relations, several important properties of matrix differential recurrence relations, biorthogonality relations and matrix differential equation for the pair of biorthogonal matrix polynomials J(A,B n (x, k and K(A,B n (x, k are discussed. For the matrix polynomials J(A,B n (x, k, various families of bilinear and bilateral generating matrix functions are constructed in the sequel.

  7. Matrix completion by deep matrix factorization.

    Science.gov (United States)

    Fan, Jicong; Cheng, Jieyu

    2018-02-01

    Conventional methods of matrix completion are linear methods that are not effective in handling data of nonlinear structures. Recently a few researchers attempted to incorporate nonlinear techniques into matrix completion but there still exists considerable limitations. In this paper, a novel method called deep matrix factorization (DMF) is proposed for nonlinear matrix completion. Different from conventional matrix completion methods that are based on linear latent variable models, DMF is on the basis of a nonlinear latent variable model. DMF is formulated as a deep-structure neural network, in which the inputs are the low-dimensional unknown latent variables and the outputs are the partially observed variables. In DMF, the inputs and the parameters of the multilayer neural network are simultaneously optimized to minimize the reconstruction errors for the observed entries. Then the missing entries can be readily recovered by propagating the latent variables to the output layer. DMF is compared with state-of-the-art methods of linear and nonlinear matrix completion in the tasks of toy matrix completion, image inpainting and collaborative filtering. The experimental results verify that DMF is able to provide higher matrix completion accuracy than existing methods do and DMF is applicable to large matrices. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Electrochemical treatment of graphite

    Energy Technology Data Exchange (ETDEWEB)

    Podlovilin, V.I.; Egorov, I.M.; Zhernovoj, A.I.

    1983-01-01

    In the course of investigating various modes of electrochemical treatment (ECT) it has been found that graphite anode treatment begins under the ''glow mode''. A behaviour of some marks of graphite with the purpose of ECT technique development in different electrolytes has been tested. Electrolytes have been chosen of three types: highly alkaline (pH 13-14), neutral (pH-Z) and highly acidic (pH 1-2). For the first time parallel to mechanical electroerosion treatment, ECT of graphite and carbon graphite materials previously considered chemically neutral is proposed. ECT of carbon graphite materials has a number of advantages as compared with electroerrosion and mechanical ones with respect to the treatment rate and purity (ronghness) of the surface. A small quantity of sludge (6-8%) under ECT is in highly alkali electrolytes.

  9. Organic electrochemical transistors

    Science.gov (United States)

    Rivnay, Jonathan; Inal, Sahika; Salleo, Alberto; Owens, Róisín M.; Berggren, Magnus; Malliaras, George G.

    2018-02-01

    Organic electrochemical transistors (OECTs) make effective use of ion injection from an electrolyte to modulate the bulk conductivity of an organic semiconductor channel. The coupling between ionic and electronic charges within the entire volume of the channel endows OECTs with high transconductance compared with that of field-effect transistors, but also limits their response time. The synthetic tunability, facile deposition and biocompatibility of organic materials make OECTs particularly suitable for applications in biological interfacing, printed logic circuitry and neuromorphic devices. In this Review, we discuss the physics and the mechanism of operation of OECTs, focusing on their identifying characteristics. We highlight organic materials that are currently being used in OECTs and survey the history of OECT technology. In addition, form factors, fabrication technologies and applications such as bioelectronics, circuits and memory devices are examined. Finally, we take a critical look at the future of OECT research and development.

  10. Electrochemical Hydrogen Compressor

    Energy Technology Data Exchange (ETDEWEB)

    Lipp, Ludwig [FuelCell Energy, Inc., Torrington, CT (United States)

    2016-01-21

    Conventional compressors have not been able to meet DOE targets for hydrogen refueling stations. They suffer from high capital cost, poor reliability and pose a risk of fuel contamination from lubricant oils. This project has significantly advanced the development of solid state hydrogen compressor technology for multiple applications. The project has achieved all of its major objectives. It has demonstrated capability of Electrochemical Hydrogen Compression (EHC) technology to potentially meet the DOE targets for small compressors for refueling sites. It has quantified EHC cell performance and durability, including single stage hydrogen compression from near-atmospheric pressure to 12,800 psi and operation of EHC for more than 22,000 hours. Capital cost of EHC was reduced by 60%, enabling a path to meeting the DOE cost targets for hydrogen compression, storage and delivery ($2.00-2.15/gge by 2020).

  11. Fast electrochemical actuator

    International Nuclear Information System (INIS)

    Uvarov, I V; Postnikov, A V; Svetovoy, V B

    2016-01-01

    Lack of fast and strong microactuators is a well-recognized problem in MEMS community. Electrochemical actuators can develop high pressure but they are notoriously slow. Water electrolysis produced by short voltage pulses of alternating polarity can overcome the problem of slow gas termination. Here we demonstrate an actuation regime, for which the gas pressure is relaxed just for 10 μs or so. The actuator consists of a microchamber filled with the electrolyte and covered with a flexible membrane. The membrane bends outward when the pressure in the chamber increases. Fast termination of gas and high pressure developed in the chamber are related to a high density of nanobubbles in the chamber. The physical processes happening in the chamber are discussed so as problems that have to be resolved for practical applications of this actuation regime. The actuator can be used as a driving engine for microfluidics. (paper)

  12. Organic electrochemical transistors

    KAUST Repository

    Rivnay, Jonathan

    2018-01-16

    Organic electrochemical transistors (OECTs) make effective use of ion injection from an electrolyte to modulate the bulk conductivity of an organic semiconductor channel. The coupling between ionic and electronic charges within the entire volume of the channel endows OECTs with high transconductance compared with that of field-effect transistors, but also limits their response time. The synthetic tunability, facile deposition and biocompatibility of organic materials make OECTs particularly suitable for applications in biological interfacing, printed logic circuitry and neuromorphic devices. In this Review, we discuss the physics and the mechanism of operation of OECTs, focusing on their identifying characteristics. We highlight organic materials that are currently being used in OECTs and survey the history of OECT technology. In addition, form factors, fabrication technologies and applications such as bioelectronics, circuits and memory devices are examined. Finally, we take a critical look at the future of OECT research and development.

  13. Capsid protein oxidation in feline calicivirus using an electrochemical inactivation treatment

    Energy Technology Data Exchange (ETDEWEB)

    Shionoiri, Nozomi; Nogariya, Osamu; Tanaka, Masayoshi; Matsunaga, Tadashi; Tanaka, Tsuyoshi, E-mail: tsuyo@cc.tuat.ac.jp

    2015-02-11

    Highlights: • Feline calicivirus was inactivated electrochemically by a factor of >5 log. • The electrochemical treatment was performed at 0.9 V (vs. Ag/AgCl) for 15 min. • Electrochemical treatment caused oxidation of viral proteins. • Oxidation of viral proteins can lead to loss of viral structural integrity. - Abstract: Pathogenic viral infections are an international public health concern, and viral disinfection has received increasing attention. Electrochemical treatment has been used for treatment of water contaminated by bacteria for several decades, and although in recent years several reports have investigated viral inactivation kinetics, the mode of action of viral inactivation by electrochemical treatment remains unclear. Here, we demonstrated the inactivation of feline calicivirus (FCV), a surrogate for human noroviruses, by electrochemical treatment in a developed flow-cell equipped with a screen-printed electrode. The viral infectivity titer was reduced by over 5 orders of magnitude after 15 min of treatment at 0.9 V vs. Ag/AgCl. Proteomic study of electrochemically inactivated virus revealed oxidation of peptides located in the viral particles; oxidation was not observed in the non-treated sample. Furthermore, transmission electron microscopy revealed that viral particles in the treated sample had irregular structures. These results suggest that electrochemical treatment inactivates FCV via oxidation of peptides in the structural region, causing structural deformation of virus particles. This first report of viral protein damage through electrochemical treatment will contribute to broadening the understanding of viral inactivation mechanisms.

  14. Electrochemical Biosensors - Sensor Principles and Architectures

    Directory of Open Access Journals (Sweden)

    Erik Reimhult

    2008-03-01

    Full Text Available Quantification of biological or biochemical processes are of utmost importancefor medical, biological and biotechnological applications. However, converting the biologicalinformation to an easily processed electronic signal is challenging due to the complexity ofconnecting an electronic device directly to a biological environment. Electrochemical biosensorsprovide an attractive means to analyze the content of a biological sample due to thedirect conversion of a biological event to an electronic signal. Over the past decades severalsensing concepts and related devices have been developed. In this review, the most commontraditional techniques, such as cyclic voltammetry, chronoamperometry, chronopotentiometry,impedance spectroscopy, and various field-effect transistor based methods are presented alongwith selected promising novel approaches, such as nanowire or magnetic nanoparticle-basedbiosensing. Additional measurement techniques, which have been shown useful in combinationwith electrochemical detection, are also summarized, such as the electrochemical versionsof surface plasmon resonance, optical waveguide lightmode spectroscopy, ellipsometry,quartz crystal microbalance, and scanning probe microscopy.The signal transduction and the general performance of electrochemical sensors are often determinedby the surface architectures that connect the sensing element to the biological sampleat the nanometer scale. The most common surface modification techniques, the various electrochemicaltransduction mechanisms, and the choice of the recognition receptor moleculesall influence the ultimate sensitivity of the sensor. New nanotechnology-based approaches,such as the use of engineered ion-channels in lipid bilayers, the encapsulation of enzymesinto vesicles, polymersomes, or polyelectrolyte capsules provide additional possibilities forsignal amplification.In particular, this review highlights the importance of the precise control over the

  15. Electrochemically controlled iron isotope fractionation

    Science.gov (United States)

    Black, Jay R.; Young, Edward D.; Kavner, Abby

    2010-02-01

    Variations in the stable isotope abundances of transition metals have been observed in the geologic record and trying to understand and reconstruct the physical/environmental conditions that produced these signatures is an area of active research. It is clear that changes in oxidation state lead to large fractionations of the stable isotopes of many transition metals such as iron, suggesting that transition metal stable isotope signatures could be used as a paleo-redox proxy. However, the factors contributing to these observed stable isotope variations are poorly understood. Here we investigate how the kinetics of iron redox electrochemistry generates isotope fractionation. Through a combination of electrodeposition experiments and modeling of electrochemical processes including mass-transport, we show that electron transfer reactions are the cause of a large isotope separation, while mass transport-limited supply of reactant to the electrode attenuates the observed isotopic fractionation. Furthermore, the stable isotope composition of electroplated transition metals can be tuned in the laboratory by controlling parameters such as solution chemistry, reaction overpotential, and solution convection. These methods are potentially useful for generating isotopically-marked metal surfaces for tracking and forensic purposes. In addition, our studies will help interpret stable isotope data in terms of identifying underlying electron transfer processes in laboratory and natural samples.

  16. Chitosan/graphene oxide nanocomposite films with enhanced interfacial interaction and their electrochemical applications

    International Nuclear Information System (INIS)

    He, Linghao; Wang, Hongfang; Xia, Guangmei; Sun, Jing; Song, Rui

    2014-01-01

    Graphical abstract: Nanocomposites by introducing graphene oxide (GO) into chitosan (CS) matrix were prepared and the effect of GO on the crystallization, thermal stability and mechanical properties of the films were investigated. In addition, the electrochemical behavior of the CS/GO modified electrode was comparatively studied with that of the neat CS-modified electrode. - Highlights: • Graphene oxide (GO) with well dispersion in the biopolymer chitosan (CS) matrix. • Detectable interactions do exist between the GO nanosheets and CS segments. • The addition of minor GO can improve the electrochemical activity of the neat CS. - Abstract: A series of chitosan (CS) nanocomposites incorporated with graphene oxide (GO) nanosheets were facilely prepared by sonochemical method. Characterized by scanning electron microscopy, the obtained nanocomposites showed fine dispersion of GO in the CS matrix. Meanwhile, a marked interfacial interaction was also revealed as the values of glass transition temperature, the decomposition temperature and the storage modulus were significantly increased with the addition of GO. Furthermore, the well dispersed GO nanosheets could significantly improve the electrochemical activity of the CS as demonstrated by the electrochemical behaviors of pure CS and the GO/CS composite electrodes. Hence, the GO/CS nanocomposites film could be a promising candidate in the fabrication of electrochemical biosensors

  17. Corrosion performance of SiCsubp/6061 Al metal matrix composites in sodium chloride solution

    International Nuclear Information System (INIS)

    Mohmad Soib bin Selamat

    1995-01-01

    The corrosion performance of silicon carbide particle/aluminium metal matrix composites (SiCsubp/Al) were studied in sodium chloride solution by means of electrochemical, microscopic, gravimetric and analytical techniques. The materials under investigation were compocasting processed 6061 Al reinforced with increasing amounts of SiC particles. Potentiostatic polarization tests were done in 0.1M NaCl solutions that were aerated or deaerated to observe overall corrosion behaviour. It was seen that the corrosion potentials did not vary greatly in relation to the amounts of SiCsubp reinforcement. Corrosion tests showed that the degree of corrosion increased with increasing SiCsubp content. SEM analysis technique was used to study the corroded samples and the pitting morphology. By TEM, no intermetallic layer was found at SiC/Al interface. A model for pitting process was proposed

  18. The Matrix Cookbook

    DEFF Research Database (Denmark)

    Petersen, Kaare Brandt; Pedersen, Michael Syskind

    Matrix identities, relations and approximations. A desktop reference for quick overview of mathematics of matrices.......Matrix identities, relations and approximations. A desktop reference for quick overview of mathematics of matrices....

  19. Carbonate fuel cell matrix

    Science.gov (United States)

    Farooque, Mohammad; Yuh, Chao-Yi

    1996-01-01

    A carbonate fuel cell matrix comprising support particles and crack attenuator particles which are made platelet in shape to increase the resistance of the matrix to through cracking. Also disclosed is a matrix having porous crack attenuator particles and a matrix whose crack attenuator particles have a thermal coefficient of expansion which is significantly different from that of the support particles, and a method of making platelet-shaped crack attenuator particles.

  20. Matrix with Prescribed Eigenvectors

    Science.gov (United States)

    Ahmad, Faiz

    2011-01-01

    It is a routine matter for undergraduates to find eigenvalues and eigenvectors of a given matrix. But the converse problem of finding a matrix with prescribed eigenvalues and eigenvectors is rarely discussed in elementary texts on linear algebra. This problem is related to the "spectral" decomposition of a matrix and has important technical…

  1. Triangularization of a Matrix

    Indian Academy of Sciences (India)

    Much of linear algebra is devoted to reducing a matrix (via similarity or unitary similarity) to another that has lots of zeros. The simplest such theorem is the Schur triangularization theorem. This says that every matrix is unitarily similar to an upper triangular matrix. Our aim here is to show that though it is very easy to prove it ...

  2. Electrochemically active functionalization of graphene for development of prototype biosensing devices

    DEFF Research Database (Denmark)

    Halder, Arnab; Ulstrup, Jens; Chi, Qijin

    nanosheets, (2) loading of different enzymes on functionalized graphene matrix, and (3) electrochemical performances of the functionalized nanaohybrid materials based prototype sensors. These latest advancements could be crucial for the design and fabrication of low-cost, flexible and disposable biosensors....

  3. Characterization of Electrochemically Generated Silver

    Science.gov (United States)

    Adam, Niklas; Martinez, James; Carrier, Chris

    2014-01-01

    Silver biocide offers a potential advantage over iodine, the current state of the art in US spacecraft disinfection technology, in that silver can be safely consumed by the crew. Low concentrations of silver (Silver does not require hardware to remove it from a water system, and therefore can provide a simpler means for disinfecting water. The Russian segment of the International Space Station has utilized an electrochemically generated silver solution, which is colloidal in nature. To be able to reliably provide a silver biocide to drinking water by electrochemical means would reduce mass required for removing another biocide such as iodine from the water. This would also aid in crew time required to replace iodine removal cartridges. Future long term missions would benefit from electrochemically produced silver as the biocide could be produced on demand and requires only a small concentration to be effective. Since it can also be consumed safely, there is less mass in removal hardware and little consumables required for production. The goal of this project initially is to understand the nature of the electrochemically produced silver, the particle sizes produced by the electrochemical cell and the effect that voltage adjustment has on the particle size. In literature, it has been documented that dissolved oxygen and pH have an effect on the ionization of the electrochemical silver so those parameters would be measured and possibly adjusted to understand their effect on the silver.

  4. Pre-treatment technology for electrochemical detection of heavy metal lead and cadmium in food

    Directory of Open Access Journals (Sweden)

    Ke YAN

    2015-04-01

    Full Text Available Wet digestion is used as the pre-treatment technology for the electrochemical detection of heavy metals in food, and the complete wet digestion condition of food sample is optimized by electrochemical experiments. The results show that the experimental samples can be digested completely using the Nitric acid-hydrogen peroxide system and is not pre-digested after adding 10 mL nitric acid at 120~140 ℃ and adding 10~15 mL of hydrogen peroxide during the heating process. The correlation coefficient of electrochemical detect is 0.99 for digestion solution of the samples, and the recovery of standard addition is 82%~115%. Wet digestion as a pre-treatment technology of food samples. It can digest sample fully and meet the requirements of electrochemical detection.

  5. The possibility of multi-layer nanofabrication via atomic force microscope-based pulse electrochemical nanopatterning

    Science.gov (United States)

    Kim, Uk Su; Morita, Noboru; Lee, Deug Woo; Jun, Martin; Park, Jeong Woo

    2017-05-01

    Pulse electrochemical nanopatterning, a non-contact scanning probe lithography process using ultrashort voltage pulses, is based primarily on an electrochemical machining process using localized electrochemical oxidation between a sharp tool tip and the sample surface. In this study, nanoscale oxide patterns were formed on silicon Si (100) wafer surfaces via electrochemical surface nanopatterning, by supplying external pulsed currents through non-contact atomic force microscopy. Nanoscale oxide width and height were controlled by modulating the applied pulse duration. Additionally, protruding nanoscale oxides were removed completely by simple chemical etching, showing a depressed pattern on the sample substrate surface. Nanoscale two-dimensional oxides, prepared by a localized electrochemical reaction, can be defined easily by controlling physical and electrical variables, before proceeding further to a layer-by-layer nanofabrication process.

  6. Synthesis of magnetite nanoparticles using electrochemical oxidation

    Directory of Open Access Journals (Sweden)

    Ye. Ya. Levitin

    2014-08-01

    Full Text Available The monodisperse magnetite nanoparticles are promising for use in the biomedical industry for targeted drug delivery, cell separation and biochemical products, Magnetic Resonance Imaging, immunological studies, etc. Classic method for the synthesis of magnetite is the chemical condensation Elmore’s, it is simple and cheap, but it is complicated by the formation of side compounds which impair the magnetic properties of the final product. Biological and medical purposes require high purity magnetite nanoparticles. Electrochemical methods of producing nanoparticles of magnetite acquire significant spread. The kinetics of electrochemical processes are a function of a larger number of parameters than the kinetics of conventional chemical reaction, thus electrochemical reactions can be thinner and more completely adjusted to give a predetermined size nanoparticles. In the kinetics of the electrochemical oxidation and reduction the important role is played by the nature of the electrode. In many industrial processes, it is advisable to use lead dioxide anodes with titanium current lead. Purpose of the work To determine the optimum conditions of electrochemical oxidation of Fe2+ Fe3+to produce magnetite with high purity and improved magnetic characteristics. Materials and methods Electrochemical studies were carried out in a glass cell ЯСЭ-2 using a potentiostat ПИ-50-1.1 and a recording device ПДА1. Reference electrode - silver chloride ЭВЛ1М 3.1, potentials listed on the hydrogen scale. The test solution contained 80 g/ l FeSO4×7H2O and H2SO4(to pH 1. The pH of the solution was measured with a pH–meter « рН–150». Concentration ratio of Fe3+/Fe2+in the solution was measured by permanganometric method. Magnetite particle sizes were measured by an electron microscope computer ЭВМ-100Л, an increasing is 2×105. Saturation magnetization was evaluated by the magnetization curve, for the measured sample in the field with strength

  7. Electrochemical incineration of wastes

    Science.gov (United States)

    Kaba, L.; Hitchens, G. D.; Bockris, J. OM.

    1989-01-01

    The disposal of domestic organic waste in its raw state is a matter of increasing public concern. Earlier, it was regarded as permissible to reject wastes into the apparently infinite sink of the sea but, during the last 20 years, it has become clear that this is environmentally unacceptable. On the other hand, sewage farms and drainage systems for cities and for new housing developments are cumbersome and expensive to build and operate. New technology whereby waste is converted to acceptable chemicals and pollution-free gases at site is desirable. The problems posed by wastes are particularly demanding in space vehicles where it is desirable to utilize treatments that will convert wastes into chemicals that can be recycled. In this situation, the combustion of waste is undesirable due to the inevitable presence of oxides of nitrogen and carbon monoxide in the effluent gases. Here, in particular, electrochemical techniques offer several advantages including the low temperatures which may be used and the absence of any NO and CO in the evolved gases. Work done in this area was restricted to technological papers, and the present report is an attempt to give a more fundamental basis to the early stages of a potentially valuable technology.

  8. Electrochemical Hydrogen Storage in a Highly Ordered Mesoporous Carbon

    Directory of Open Access Journals (Sweden)

    Dan eLiu

    2014-10-01

    Full Text Available A highly order mesoporous carbon has been synthesized through a strongly acidic, aqueous cooperative assembly route. The structure and morphology of the carbon material were investigated using TEM, SEM and nitrogen adsorption-desorption isotherms. The carbon was proven to be meso-structural and consisted of graphitic micro-domain with larger interlayer space. AC impedance and electrochemical measurements reveal that the synthesized highly ordered mesoporous carbon exhibits a promoted electrochemical hydrogen insertion process and improved capacitance and hydrogen storage stability. The meso-structure and enlarged interlayer distance within the highly ordered mesoporous carbon are suggested as possible causes for the enhancement in hydrogen storage. Both hydrogen capacity in the carbon and mass diffusion within the matrix were improved.

  9. Electrochemical sensors based on stationary electrodes and immobilized DNA or its fragments and the assessment of their analytical potentials

    Czech Academy of Sciences Publication Activity Database

    Babkina, S. S.; Paleček, Emil; Jelen, František; Fojta, Miroslav

    2005-01-01

    Roč. 60, č. 6 (2005), s. 567-572 ISSN 1061-9348. [VII All-Russia Conference (with international participation) on Electrochemical Methods of Analysis. Ufa, 23.05.2004-27.05.2004] R&D Projects: GA MPO(CZ) 1H-PK/42 Institutional research plan: CEZ:AV0Z50040507 Keywords : electrochemical biosensor * DNA imobilization * nitrocellulose matrix Subject RIV: BO - Biophysics Impact factor: 0.496, year: 2005

  10. Synthesis and characterization of electrochemically-reduced graphene

    Indian Academy of Sciences (India)

    Graphene has superior electrical conductivity than graphite and other allotropes of carbon because of its high surface area and chemical tolerance. Electrochemically processed graphene sheets were obtained through the reduction of graphene oxide from hydrazine hydrate. The prepared samples were heated to different ...

  11. Electrochemical corrosion testing of metal waste forms

    International Nuclear Information System (INIS)

    Abraham, D. P.; Peterson, J. J.; Katyal, H. K.; Keiser, D. D.; Hilton, B. A.

    1999-01-01

    Electrochemical corrosion tests have been conducted on simulated stainless steel-zirconium (SS-Zr) metal waste form (MWF) samples. The uniform aqueous corrosion behavior of the samples in various test solutions was measured by the polarization resistance technique. The data show that the MWF corrosion rates are very low in groundwaters representative of the proposed Yucca Mountain repository. Galvanic corrosion measurements were also conducted on MWF samples that were coupled to an alloy that has been proposed for the inner lining of the high-level nuclear waste container. The experiments show that the steady-state galvanic corrosion currents are small. Galvanic corrosion will, hence, not be an important mechanism of radionuclide release from the MWF alloys

  12. Influence of the matrix composition in the Emission spectroscopic analysis of solutions with continuous nebulization of the sample and excitation of the spectrum in a high-frequency inductively coupled plasma discharge

    International Nuclear Information System (INIS)

    Zil'bershtein, K.I.; Kartasheva, M.A.; Mushkovich, G.N.

    1986-01-01

    Numerous investigations have shown that the emission spectroscopic analysis of solutions with the use of a high-frequency inductively coupled plasma discharge is characterized by the absence of an influence or the presence of a small influence of the matrix elements on the amplitudes of the analytical signals of the elements being determined and, consequently, on the results of an analysis. The influences of the first type include the influences of easily ionized elements, which, as we know, are very significant in spectroscopic analysis with the use of traditional sources for the excitation of the spectra (arcs, sparks, and flames). The influences of the second type include, in particular, the influences associated with changes in the viscosity and surface tension of the solutions as the concentration of the matrix elements in the solutions is increased. In order to obtain correct results from an analysis in the case of spectral interference, special methods for treating the spectra are used for the purpose of taking into account the background and the instances of superposition and establishing the true (''pure'') intensity of the analytical lines. Results are shown of the Determination of impurities in aqueous solutions of sodium Molybate Single Crystals (the concentration of Na 2 Mo 2 O 7 in the solution was 1 mg/ml). When the solutions being analyzed are diluted to a concentration of Na 2 Mo 2 O 7 equal to 1 mg/ml, good agreement between the results of the determination of vanadium (and other impurities) obtained with the use of reference solutions not containing the matrix elements and the results obtained with the use of reference solutions containing the matrix elements in the same concentrations as in the solutions being analyzed (1mg/ml) was guaranteed

  13. Trace detection of organic compounds in complex sample matrixes by single photon ionization ion trap mass spectrometry: real-time detection of security-relevant compounds and online analysis of the coffee-roasting process.

    Science.gov (United States)

    Schramm, Elisabeth; Kürten, Andreas; Hölzer, Jasper; Mitschke, Stefan; Mühlberger, Fabian; Sklorz, Martin; Wieser, Jochen; Ulrich, Andreas; Pütz, Michael; Schulte-Ladbeck, Rasmus; Schultze, Rainer; Curtius, Joachim; Borrmann, Stephan; Zimmermann, Ralf

    2009-06-01

    An in-house-built ion trap mass spectrometer combined with a soft ionization source has been set up and tested. As ionization source, an electron beam pumped vacuum UV (VUV) excimer lamp (EBEL) was used for single-photon ionization. It was shown that soft ionization allows the reduction of fragmentation of the target analytes and the suppression of most matrix components. Therefore, the combination of photon ionization with the tandem mass spectrometry (MS/MS) capability of an ion trap yields a powerful tool for molecular ion peak detection and identification of organic trace compounds in complex matrixes. This setup was successfully tested for two different applications. The first one is the detection of security-relevant substances like explosives, narcotics, and chemical warfare agents. One test substance from each of these groups was chosen and detected successfully with single photon ionization ion trap mass spectrometry (SPI-ITMS) MS/MS measurements. Additionally, first tests were performed, demonstrating that this method is not influenced by matrix compounds. The second field of application is the detection of process gases. Here, exhaust gas from coffee roasting was analyzed in real time, and some of its compounds were identified using MS/MS studies.

  14. Disposable Screen Printed Electrochemical Sensors: Tools for Environmental Monitoring

    Directory of Open Access Journals (Sweden)

    Akhtar Hayat

    2014-06-01

    Full Text Available Screen printing technology is a widely used technique for the fabrication of electrochemical sensors. This methodology is likely to underpin the progressive drive towards miniaturized, sensitive and portable devices, and has already established its route from “lab-to-market” for a plethora of sensors. The application of these sensors for analysis of environmental samples has been the major focus of research in this field. As a consequence, this work will focus on recent important advances in the design and fabrication of disposable screen printed sensors for the electrochemical detection of environmental contaminants. Special emphasis is given on sensor fabrication methodology, operating details and performance characteristics for environmental applications.

  15. Exploratory Technology Research Program for electrochemical energy storage

    Science.gov (United States)

    Kinoshita, Kim

    1994-09-01

    The U.S. Department of Energy's Office of Propulsion Systems provides support for an Electrochemical Energy Storage Program, that includes research and development (R&D) on advanced rechargeable batteries and fuel cells. A major goal of this program is to develop electrochemical power sources suitable for application in electric vehicles (EV's). The program centers on advanced systems that offer the potential for high performance and low life-cycle costs, both of which are necessary to permit significant penetration into commercial markets. The DOE Electrochemical Energy Storage Program is divided into two projects: the Electric Vehicle Advanced Battery Systems (EVABS) Development Program and the Exploratory Technology Research (ETR) Program. The EVABS Program management responsibility has been assigned to Sandia National Laboratories (SNL); Lawrence Berkeley Laboratory (LBL) is responsible for management of the ETR Program. The EVABS and ETR Programs include an integrated matrix of R&D efforts designed to advance progress on selected candidate electrochemical systems. The United States Advanced Battery Consortium (USABC), a tripartite undertaking between DOE, the U.S. automobile manufacturers and the Electric Power Research Institute (EPRI), was formed in 1991 to accelerate the development of advanced batteries for consumer EV's. The role of the FIR Program is to perform supporting research on the advanced battery systems under development by the USABC and EVABS Program, and to evaluate new systems with potentially superior performance, durability and/or cost characteristics. The specific goal of the ETR Program is to identify the most promising electrochemical technologies and transfer them to the USABC, the battery industry and/or the EVABS Program for further development and scale-up. This report summarizes the research, financial and management activities relevant to the ETR Program in CY 1993.

  16. Polychoric/Tetrachoric Matrix or Pearson Matrix? A methodological study

    Directory of Open Access Journals (Sweden)

    Dominguez Lara, Sergio Alexis

    2014-04-01

    Full Text Available The use of product-moment correlation of Pearson is common in most studies in factor analysis in psychology, but it is known that this statistic is only applicable when the variables related are in interval scale and normally distributed, and when are used in ordinal data may to produce a distorted correlation matrix . Thus is a suitable option using polychoric/tetrachoric matrices in item-level factor analysis when the items are in level measurement nominal or ordinal. The aim of this study was to show the differences in the KMO, Bartlett`s Test and Determinant of the Matrix, percentage of variance explained and factor loadings in depression trait scale of Depression Inventory Trait - State and the Neuroticism dimension of the short form of the Eysenck Personality Questionnaire -Revised, regarding the use of matrices polychoric/tetrachoric matrices and Pearson. These instruments was analyzed with different extraction methods (Maximum Likelihood, Minimum Rank Factor Analysis, Unweighted Least Squares and Principal Components, keeping constant the rotation method Promin were analyzed. Were observed differences regarding sample adequacy measures, as well as with respect to the explained variance and the factor loadings, for solutions having as polychoric/tetrachoric matrix. So it can be concluded that the polychoric / tetrachoric matrix give better results than Pearson matrices when it comes to item-level factor analysis using different methods.

  17. Pulse electrochemical meso/micro/nano ultraprecision machining technology.

    Science.gov (United States)

    Lee, Jeong Min; Kim, Young Bin; Park, Jeong Woo

    2013-11-01

    This study demonstrated meso/micro/nano-ultraprecision machining through electrochemical reactions using intermittent DC pulses. The experiment focused on two machining methods: (1) pulse electrochemical polishing (PECP) of stainless steel, and (2) pulse electrochemical nano-patterning (PECNP) on a silicon (Si) surface, using atomic force microscopy (AFM) for fabrication. The dissolution reaction at the stainless steel surface following PECP produced a very clean, smooth workpiece. The advantages of the PECP process included improvements in corrosion resistance, deburring of the sample surface, and removal of hydrogen from the stainless steel surface as verified by time-of-flight secondary-ion mass spectrometry (TOF-SIMS). In PECNP, the electrochemical reaction generated within water molecules produced nanoscale oxide textures on a Si surface. Scanning probe microscopy (SPM) was used to evaluate nanoscale-pattern processing on a Si wafer surface produced by AFM-PECNP For both processes using pulse electrochemical reactions, three-dimensional (3-D) measurements and AFM were used to investigate the changes on the machined surfaces. Preliminary results indicated the potential for advancing surface polishing techniques and localized micro/nano-texturing technology using PECP and PECNP processes.

  18. Electrochemical oxidation of organic waste

    International Nuclear Information System (INIS)

    Almon, A.C.; Buchanan, B.R.

    1990-01-01

    Both silver catalyzed and direct electrochemical oxidation of organic species are examined in analytical detail. This paper describes the mechanisms, reaction rates, products, intermediates, capabilities, limitations, and optimal reaction conditions of the electrochemical destruction of organic waste. A small bench-top electrocell being tested for the treatment of small quantities of laboratory waste is described. The 200-mL electrochemical cell used has a processing capacity of 50 mL per day, and can treat both radioactive and nonradioactive waste. In the silver catalyzed process, Ag(I) is electrochemically oxidized to Ag(II), which attacks organic species such as tributylphosphate (TBP), tetraphenylborate (TPB), and benzene. In direct electrochemical oxidation, the organic species are destroyed at the surface of the working electrode without the use of silver as an electron transfer agent. This paper focuses on the destruction of tributylphosphate (TBP), although several organic species have been destroyed using this process. The organic species are converted to carbon dioxide, water, and inorganic acids

  19. A sensitive method for electrochemical determination of molybdenum (VI in plant foodstuff samples using Ni0.5Zn0.5Fe2O4 nanocomposite modified carbon paste electrode

    Directory of Open Access Journals (Sweden)

    Abbas Afkhami

    2016-07-01

    Full Text Available In the present study, a new chemically modified carbon paste electrode (CPE is constructed for rapid, accurate, simple, highly sensitive, and selective determination of Mo (VI using differential pulse voltammetry. The electrode was prepared using magnetic nickel zinc ferrite nanocomposite (Ni0.5Zn0.5Fe2O4, as the modifier in CPE (Ni0.5Zn0.5Fe2O4/CPE. Mo (VI was determined after preconcentration at the surface of the modified electrode at -0.7 V vs. Ag/AgCl. Under the optimal conditions, the linear dynamic range and limit of detection were 0.005-1.00 and 0.003 µgmL-1, respectively. Ten successive measurements of 0.06 and 0.70 µg mL-1 of Mo (VI ions showed the relative standard deviation of 3.20 and 1.98 %, respectively. The reproducibility and stability of the electrode response were also studied. Investigation of the effects of different cations and anions on the determination of Mo (VI indicated that the electrode is highly selective. Furthermore, the present method was applied to the determination of Mo (VI in several plant foodstuff samples with satisfactory results.

  20. Cleaning the correlation matrix with a denoising autoencoder

    OpenAIRE

    Hayou, Soufiane

    2017-01-01

    In this paper, we use an adjusted autoencoder to estimate the true eigenvalues of the population correlation matrix from the sample correlation matrix when the number of samples is small. We show that the model outperforms the Rotational Invariant Estimator (Bouchaud) which is the optimal estimator in the sample eigenvectors basis when the dimension goes to infinity.

  1. Parallelism in matrix computations

    CERN Document Server

    Gallopoulos, Efstratios; Sameh, Ahmed H

    2016-01-01

    This book is primarily intended as a research monograph that could also be used in graduate courses for the design of parallel algorithms in matrix computations. It assumes general but not extensive knowledge of numerical linear algebra, parallel architectures, and parallel programming paradigms. The book consists of four parts: (I) Basics; (II) Dense and Special Matrix Computations; (III) Sparse Matrix Computations; and (IV) Matrix functions and characteristics. Part I deals with parallel programming paradigms and fundamental kernels, including reordering schemes for sparse matrices. Part II is devoted to dense matrix computations such as parallel algorithms for solving linear systems, linear least squares, the symmetric algebraic eigenvalue problem, and the singular-value decomposition. It also deals with the development of parallel algorithms for special linear systems such as banded ,Vandermonde ,Toeplitz ,and block Toeplitz systems. Part III addresses sparse matrix computations: (a) the development of pa...

  2. Neutrino mass matrix

    International Nuclear Information System (INIS)

    Strobel, E.L.

    1985-01-01

    Given the many conflicting experimental results, examination is made of the neutrino mass matrix in order to determine possible masses and mixings. It is assumed that the Dirac mass matrix for the electron, muon, and tau neutrinos is similar in form to those of the quarks and charged leptons, and that the smallness of the observed neutrino masses results from the Gell-Mann-Ramond-Slansky mechanism. Analysis of masses and mixings for the neutrinos is performed using general structures for the Majorana mass matrix. It is shown that if certain tentative experimental results concerning the neutrino masses and mixing angles are confirmed, significant limitations may be placed on the Majorana mass matrix. The most satisfactory simple assumption concerning the Majorana mass matrix is that it is approximately proportional to the Dirac mass matrix. A very recent experimental neutrino mass result and its implications are discussed. Some general properties of matrices with structure similar to the Dirac mass matrices are discussed

  3. Kelvin probe force microscopy in liquid using electrochemical force microscopy

    Directory of Open Access Journals (Sweden)

    Liam Collins

    2015-01-01

    Full Text Available Conventional closed loop-Kelvin probe force microscopy (KPFM has emerged as a powerful technique for probing electric and transport phenomena at the solid–gas interface. The extension of KPFM capabilities to probe electrostatic and electrochemical phenomena at the solid–liquid interface is of interest for a broad range of applications from energy storage to biological systems. However, the operation of KPFM implicitly relies on the presence of a linear lossless dielectric in the probe–sample gap, a condition which is violated for ionically-active liquids (e.g., when diffuse charge dynamics are present. Here, electrostatic and electrochemical measurements are demonstrated in ionically-active (polar isopropanol, milli-Q water and aqueous NaCl and ionically-inactive (non-polar decane liquids by electrochemical force microscopy (EcFM, a multidimensional (i.e., bias- and time-resolved spectroscopy method. In the absence of mobile charges (ambient and non-polar liquids, KPFM and EcFM are both feasible, yielding comparable contact potential difference (CPD values. In ionically-active liquids, KPFM is not possible and EcFM can be used to measure the dynamic CPD and a rich spectrum of information pertaining to charge screening, ion diffusion, and electrochemical processes (e.g., Faradaic reactions. EcFM measurements conducted in isopropanol and milli-Q water over Au and highly ordered pyrolytic graphite electrodes demonstrate both sample- and solvent-dependent features. Finally, the feasibility of using EcFM as a local force-based mapping technique of material-dependent electrostatic and electrochemical response is investigated. The resultant high dimensional dataset is visualized using a purely statistical approach that does not require a priori physical models, allowing for qualitative mapping of electrostatic and electrochemical material properties at the solid–liquid interface.

  4. Teaching Improvement Model Designed with DEA Method and Management Matrix

    Science.gov (United States)

    Montoneri, Bernard

    2014-01-01

    This study uses student evaluation of teachers to design a teaching improvement matrix based on teaching efficiency and performance by combining management matrix and data envelopment analysis. This matrix is designed to formulate suggestions to improve teaching. The research sample consists of 42 classes of freshmen following a course of English…

  5. Electrochemical behavior of labetalol at an ionic liquid modified carbon paste electrode and its electrochemical determination

    Directory of Open Access Journals (Sweden)

    Zhang Yan-Mei

    2013-01-01

    Full Text Available Electrochemical behavior of labetalol (LBT at carbon paste electrode (CPE and an ionic liquid1-benzyl-3-methylimidazolehexafluorophosphate([BnMIM]PF6modified carbon paste electrode([BnMIM]PF6/CPEin Britton-Robinson buffer solution (pH 2.0 was investigated by cyclic voltammetry (CV and square wave voltammetric (SWV. The experimental results showed that LBT at both the bare CPE and [BnMIM]PF6/CPEshowed an irreversible oxidation process, but at [BnMIM]PF6/CPE its oxidation peak current increased greatly and the oxidation peak potential shifted negatively. The electrode reaction process is a diffusion-controlled process involving one electron transferring accompanied by a participation of one proton at [BnMIM]PF6/CPE. At the same time, the electrochemical kinetic parameters were determined. Under the optimized electrochemical experimental conditions, the oxidation peak currents were proportional to LBT concentration in the range of 7.0 x 10-6-1.0 x 10-4 mol L-1 with the limit of detection(LOD, S/N=3 of 4.810 x 10-8 mol L-1and the limit of quantification(LOQ, S/N=10 of 1.60 x 10-7 mol L-1, respectively. The proposed method was successfully applied in the determination of LBT content in commercial tablet samples.

  6. Superhydrophobic surfaces by electrochemical processes.

    Science.gov (United States)

    Darmanin, Thierry; Taffin de Givenchy, Elisabeth; Amigoni, Sonia; Guittard, Frederic

    2013-03-13

    This review is an exhaustive representation of the electrochemical processes reported in the literature to produce superhydrophobic surfaces. Due to the intensive demand in the elaboration of superhydrophobic materials using low-cost, reproducible and fast methods, the use of strategies based on electrochemical processes have exponentially grown these last five years. These strategies are separated in two parts: the oxidation processes, such as oxidation of metals in solution, the anodization of metals or the electrodeposition of conducting polymers, and the reduction processed such as the electrodeposition of metals or the galvanic deposition. One of the main advantages of the electrochemical processes is the relative easiness to produce various surface morphologies and a precise control of the structures at a micro- or a nanoscale. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Electrochemical noise measurements under pressurized water reactor conditions

    International Nuclear Information System (INIS)

    Van Nieuwenhove, R.

    2000-01-01

    Electrochemical potential noise measurements on sensitized stainless steel pressure tubes under pressurized water reactor (PWR) conditions were performed for the first time. Very short potential spikes, believed to be associated to crack initiation events, were detected when stressing the sample above the yield strength and increased in magnitude until the sample broke. Sudden increases of plastic deformation, as induced by an increased tube pressure, resulted in slower, high-amplitude potential transients, often accompanied by a reduction in noise level

  8. Systems, methods and computer-readable media to model kinetic performance of rechargeable electrochemical devices

    Science.gov (United States)

    Gering, Kevin L.

    2013-01-01

    A system includes an electrochemical cell, monitoring hardware, and a computing system. The monitoring hardware samples performance characteristics of the electrochemical cell. The computing system determines cell information from the performance characteristics. The computing system also analyzes the cell information of the electrochemical cell with a Butler-Volmer (BV) expression modified to determine exchange current density of the electrochemical cell by including kinetic performance information related to pulse-time dependence, electrode surface availability, or a combination thereof. A set of sigmoid-based expressions may be included with the modified-BV expression to determine kinetic performance as a function of pulse time. The determined exchange current density may be used with the modified-BV expression, with or without the sigmoid expressions, to analyze other characteristics of the electrochemical cell. Model parameters can be defined in terms of cell aging, making the overall kinetics model amenable to predictive estimates of cell kinetic performance along the aging timeline.

  9. Fabrication and characterization of electrochemically prepared bioanode (polyaniline/ferritin/glucose oxidase) for biofuel cell application

    Science.gov (United States)

    ul Haque, Sufia; Inamuddin; Nasar, Abu; Asiri, Abdullah M.

    2018-01-01

    Porous matrix of polyaniline (PANI) has been electrodeposited along with the entrapment of biocompatible redox mediator ferritin (Frt) and glucose oxidase (GOx) on the surface of glassy carbon (GC) electrode. The characterizations have been carried out by X-ray Diffraction (XRD) and Transmission electron microscopy (TEM). The enhanced electrochemical signal transfer rate from enzyme to the electrode surface was due to the intimate contact of the enzyme with the electrochemically polymerized conducting PANI matrix. The PANI/Frt/GOx modified GC bioanode was used to investigate the electrocatalytic activity as a function of the concentration of glucose in the range of 10-60 mM. It was confirmed by the electrochemical impedance spectroscopy (EIS), the thick deposition of PANI layer becomes more compact due to which the charge transfer resistance of PANI matrix becomes higher. All the electrochemical measurements of the electrode were carried out by using cyclic voltammetry (CV) and linear sweep voltammetry (LSV). CV curves were recorded at different scan rates (20-100 mV/s) at 50 mM of glucose in 0.3 M potassium ferrocyanide. A normalized saturation current density of 22.3 ± 2 mA/cm2 was observed for the oxidation of 50 mM glucose at a scan rate of 100 mV/s.

  10. An electrochemical sensor for gallic acid based on Fe{sub 2}O{sub 3}/electro-reduced graphene oxide composite: Estimation for the antioxidant capacity index of wines

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Feng, E-mail: fgao1981@126.com [College of Chemistry and Environment, Fujian Province Key Laboratory of Morden Analytical Science and Separation Technology, Minnan Normal University, Zhangzhou 363000 (China); Department of Chemistry, Graduate School of Science and Engineering, Shimane University, 1060 Nishikawatsu, Matsue, Shimane 690-8504 (Japan); Zheng, Delun [College of Chemistry and Environment, Fujian Province Key Laboratory of Morden Analytical Science and Separation Technology, Minnan Normal University, Zhangzhou 363000 (China); Tanaka, Hidekazu [Department of Chemistry, Graduate School of Science and Engineering, Shimane University, 1060 Nishikawatsu, Matsue, Shimane 690-8504 (Japan); Zhan, Fengping; Yuan, Xiaoning; Gao, Fei [College of Chemistry and Environment, Fujian Province Key Laboratory of Morden Analytical Science and Separation Technology, Minnan Normal University, Zhangzhou 363000 (China); Wang, Qingxiang, E-mail: axiang236@126.com [College of Chemistry and Environment, Fujian Province Key Laboratory of Morden Analytical Science and Separation Technology, Minnan Normal University, Zhangzhou 363000 (China)

    2015-12-01

    A highly sensitive electrochemical sensor for gallic acid (GA), an important polyphenolic compound, was fabricated using the hybrid material of chitosan (CS), fishbone-shaped Fe{sub 2}O{sub 3} (fFe{sub 2}O{sub 3}), and electrochemically reduced graphene oxide (ERGO) as the sensing matrix. The electrochemical characterization experiments showed that the CS–fFe{sub 2}O{sub 3}–ERGO modified glassy carbon electrode (CS–fFe{sub 2}O{sub 3}–ERGO/GCE) had large surface area, excellent electronic conductivity and high stability. The GA presented a superior electrochemical response on CS–fFe{sub 2}O{sub 3}–ERGO/GCE in comparison with the single-component modified electrode. The electrochemical mechanism and optimal test conditions of GA on the electrode surface were carefully investigated. Under the optimal conditions, the oxidation peak currents in differential pulse voltammetry (DPV) experiments exhibited a good linear relationship with the logarithmic values of GA concentration over the range from 1.0 × 10{sup −6} M to 1.0 × 10{sup −4} M. Based on signal-to-noise (S/N) characteristic of 3, the detection limit was estimated to be 1.5 × 10{sup −7} M. The proposed sensor has also been applied for estimating the antioxidant capacity index of real samples of red and white wines. - Highlights: • Fishbone-shaped Fe{sub 2}O{sub 3} (fFe{sub 2}O{sub 3}) nanoparticles were synthesized by a simple template-free solvothermal method. • The nanocomposite of fFe{sub 2}O{sub 3}, graphene and chitosan was used as the sensing platform for gallic acid. • The sensor shows a wide linear range and low detection limit for gallic acid. • The antioxidant capacity index of wines was successfully evaluated by the sensor.

  11. Patience of matrix games

    DEFF Research Database (Denmark)

    Hansen, Kristoffer Arnsfelt; Ibsen-Jensen, Rasmus; Podolskii, Vladimir V.

    2013-01-01

    For matrix games we study how small nonzero probability must be used in optimal strategies. We show that for image win–lose–draw games (i.e. image matrix games) nonzero probabilities smaller than image are never needed. We also construct an explicit image win–lose game such that the unique optimal...

  12. Matrix comparison, Part 2

    DEFF Research Database (Denmark)

    Schneider, Jesper Wiborg; Borlund, Pia

    2007-01-01

    The present two-part article introduces matrix comparison as a formal means for evaluation purposes in informetric studies such as cocitation analysis. In the first part, the motivation behind introducing matrix comparison to informetric studies, as well as two important issues influencing such c...

  13. Unitarity of CKM Matrix

    CERN Document Server

    Saleem, M

    2002-01-01

    The Unitarity of the CKM matrix is examined in the light of the latest available accurate data. The analysis shows that a conclusive result cannot be derived at present. Only more precise data can determine whether the CKM matrix opens new vistas beyond the standard model or not.

  14. Fuzzy risk matrix

    International Nuclear Information System (INIS)

    Markowski, Adam S.; Mannan, M. Sam

    2008-01-01

    A risk matrix is a mechanism to characterize and rank process risks that are typically identified through one or more multifunctional reviews (e.g., process hazard analysis, audits, or incident investigation). This paper describes a procedure for developing a fuzzy risk matrix that may be used for emerging fuzzy logic applications in different safety analyses (e.g., LOPA). The fuzzification of frequency and severity of the consequences of the incident scenario are described which are basic inputs for fuzzy risk matrix. Subsequently using different design of risk matrix, fuzzy rules are established enabling the development of fuzzy risk matrices. Three types of fuzzy risk matrix have been developed (low-cost, standard, and high-cost), and using a distillation column case study, the effect of the design on final defuzzified risk index is demonstrated

  15. Fuzzy vulnerability matrix

    International Nuclear Information System (INIS)

    Baron, Jorge H.; Rivera, S.S.

    2000-01-01

    The so-called vulnerability matrix is used in the evaluation part of the probabilistic safety assessment for a nuclear power plant, during the containment event trees calculations. This matrix is established from what is knows as Numerical Categories for Engineering Judgement. This matrix is usually established with numerical values obtained with traditional arithmetic using the set theory. The representation of this matrix with fuzzy numbers is much more adequate, due to the fact that the Numerical Categories for Engineering Judgement are better represented with linguistic variables, such as 'highly probable', 'probable', 'impossible', etc. In the present paper a methodology to obtain a Fuzzy Vulnerability Matrix is presented, starting from the recommendations on the Numerical Categories for Engineering Judgement. (author)

  16. Electrochemical behavior of amorphous metal-silicon-carbon nanocomposites based on titanium or tungsten nanophase

    International Nuclear Information System (INIS)

    Pleskov, Yu.V.; Krotova, M.D.; Shupegin, M.L.; Bozhko, A.D.

    2009-01-01

    Electrode behavior of nanocomposite films containing titanium- or tungsten-based conducting nanophase embedded in dielectric silicon-carbon matrix, deposited onto glassceramics substrate, is studied by cyclic voltammetry and electrochemical impedance spectroscopy. As the films' resistivity decreases, their electrochemical behavior gradually changes from that of 'poor conductor' to the nearly metal-like behavior. In particular, the differential capacitance increases, the charge transfer in a model redox system [Fe(CN) 6 ] 3-/4- accelerates, which may be explained by the increasing number of metal-containing clusters at the film/electrolyte solution interface

  17. Graphene derived carbon confined sulfur cathodes for lithium-sulfur batteries: Electrochemical impedance studies

    International Nuclear Information System (INIS)

    Ganesan, Aswathi; Varzi, Alberto; Passerini, Stefano; Shaijumon, Manikoth M.

    2016-01-01

    Highlights: • Graphene-derived carbon (GDC) with distinctive porosity characteristics are prepared. • Effect of micro-/mesoporosity of GDC for improved Li-S battery performance is studied. • Impedance studies reveal insights into Li-S redox reactions and capacity fading phenomena. - Abstract: Sulfur nanocomposites are prepared by using graphene derived carbon (GDC), with controlled porosity characteristics, as confining matrix and are studied as efficient cathodes for lithium-sulfur (Li-S) batteries. To understand the effect of micro-/mesoporosity in porous carbon for the effective encapsulation of sulfur and polysulfides towards improved Li-S battery performance, two different GDC samples with controlled porosity characteristics, one with predominantly micropores (GDC-1) and a surface area of 1970 m 2 g −1 and the other with a surface area of 3239 m 2 g −1 , having more or less equal contribution of micro- and mesopores (GDC-2), are used to synthesize nanocomposite sulfur electrodes following melt diffusion process. Electrochemical studies are carried out by using cyclic voltammetry, galvanostatic charge/discharge cycling and electrochemical impedance spectroscopy (EIS). EIS spectra collected at different depth of discharge (DOD) in the first cycle as well as upon cycling give valuable insights into the Li-S redox reactions and capacity fading phenomena in these electrodes. The impedance response of GDC-S electrodes suggests a detrimental effect of the mesopores, where insoluble reaction products can easily accumulate, resulting in the loss of active material leading to capacity fading of Li-S cells.

  18. The Matrix exponential, Dynamic Systems and Control

    DEFF Research Database (Denmark)

    Poulsen, Niels Kjølstad

    The matrix exponential can be found in various connections in analysis and control of dynamic systems. In this short note we are going to list a few examples. The matrix exponential usably pops up in connection to the sampling process, whatever it is in a deterministic or a stochastic setting...... or it is a tool for determining a Gramian matrix. This note is intended to be used in connection to the teaching post the course in Stochastic Adaptive Control (02421) given at Informatics and Mathematical Modelling (IMM), The Technical University of Denmark. This work is a result of a study of the litterature....

  19. Aptamer-Based Electrochemical Sensing of Lysozyme

    Directory of Open Access Journals (Sweden)

    Alina Vasilescu

    2016-06-01

    Full Text Available Protein analysis and quantification are required daily by thousands of laboratories worldwide for activities ranging from protein characterization to clinical diagnostics. Multiple factors have to be considered when selecting the best detection and quantification assay, including the amount of protein available, its concentration, the presence of interfering molecules, as well as costs and rapidity. This is also the case for lysozyme, a 14.3-kDa protein ubiquitously present in many organisms, that has been identified with a variety of functions: antibacterial activity, a biomarker of several serious medical conditions, a potential allergen in foods or a model of amyloid-type protein aggregation. Since the design of the first lysozyme aptamer in 2001, lysozyme became one of the most intensively-investigated biological target analytes for the design of novel biosensing concepts, particularly with regards to electrochemical aptasensors. In this review, we discuss the state of the art of aptamer-based electrochemical sensing of lysozyme, with emphasis on sensing in serum and real samples.

  20. Mediated electrochemical oxidation of mixed wastes

    International Nuclear Information System (INIS)

    Chiba, Z.

    1993-04-01

    The Mediated Electrochemical Oxidation (MEO) process was studied for destroying low-level combustible mixed wastes at Rocky Flats Plant. Tests were performed with non-radioactive surrogate materials: Trimsol for contaminated cutting oils, and reagent-grade cellulose for contaminated cellulosic wastes. Extensive testing was carried out on Trimsol in both small laboratory-scale apparatus and on a large-scale system incorporating an industrial-size electrochemical cell. Preliminary tests were also carried out in the small-scale system with cellulose. Operating and system parameters that were studied were: use of a silver-nitric acid versus a cobalt-sulfuric acid system, effect of electrolyte temperature, effect of acid concentration, and effect of current density. Destruction and coulombic efficiencies were calculated using data obtained from continuous carbon dioxide monitors and total organic carbon (TOC) analysis of electrolyte samples. For Trimsol, the best performance was achieved with the silver-nitrate system at high acid concentrations, temperatures, and current densities. Destruction efficiencies of 99% or greater, and coulombic efficiencies up to 70% were obtained. For the cellulose, high destruction efficiencies and reasonable coulombic efficiencies were obtained for both silver-nitrate and cobalt-sulfate systems

  1. SUPPLEMENTARY INFORMATION A combined Electrochemical ...

    Indian Academy of Sciences (India)

    DELL

    A combined Electrochemical and Theoretical study of pyridine-based Schiff bases as novel corrosion inhibitors for mild steel in hydrochloric acid medium. PARUL DOHAREa, M A QURAISHIb* and I B OBOTb. aDepartment of Chemistry, Indian Institute of Technology, Banaras Hindu University, Varanasi, Uttar. Pradesh 221 ...

  2. Electrolytes for magnesium electrochemical cells

    Science.gov (United States)

    Burrell, Anthony K.; Sa, Niya; Proffit, Danielle Lee; Lipson, Albert; Liao, Chen; Vaughey, John T.; Ingram, Brian J.

    2017-07-04

    An electrochemical cell includes a high voltage cathode configured to operate at 1.5 volts or greater; an anode including Mg.sup.0; and an electrolyte including an ether solvent and a magnesium salt; wherein: a concentration of the magnesium salt in the ether is 1 M or greater.

  3. All-Polymer Electrochemical Sensors

    DEFF Research Database (Denmark)

    Kafka, Jan Robert

    This thesis presents fabrication strategies to produce different types of all-polymer electrochemical sensors based on electrodes made of the highly conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT). Three different systems are presented, fabricated either by using microdrilling or by hot...

  4. Electrochemical method for transferring graphene

    DEFF Research Database (Denmark)

    2015-01-01

    The present application discloses a method for separating a graphene-support layer laminate from a conducting substrate-graphene-support layer laminate, using a gentle, controllable electrochemical method. In this way, substrates which are fragile, expensive or difficult to manufacture can be used...... - and even re-used - without damage or destruction of the substrate or the graphene....

  5. Materials for electrochemical device safety

    Science.gov (United States)

    Vissers, Daniel R.; Amine, Khalil; Thackeray, Michael M.; Kahaian, Arthur J.; Johnson, Christopher S.

    2015-04-07

    An electrochemical device includes a thermally-triggered intumescent material or a gas-triggered intumescent material. Such devices prevent or minimize short circuits in a device that could lead to thermal run-away. Such devices may include batteries or supercapacitors.

  6. (Bio)electrochemical ammonia recovery

    NARCIS (Netherlands)

    Kuntke, P.; Sleutels, T.H.J.A.; Rodríguez Arredondo, M.; Georg, S.; Barbosa, S.G.; Heijne, Ter A.; Hamelers, Hubertus V.M.; Buisman, C.J.N.

    2018-01-01

    In recent years, (bio)electrochemical systems (B)ES have emerged as an energy efficient alternative for the recovery of TAN (total ammonia nitrogen, including ammonia and ammonium) from wastewater. In these systems, TAN is removed or concentrated from the wastewater under the influence of an

  7. Graphene-based electrochemical supercapacitors

    Indian Academy of Sciences (India)

    WINTEC

    been great interest in graphene, which constitutes an entirely new class of carbon. Electrical characteriza- tion of single-layer graphene has been reported. 12,13. We have investigated the use of graphene as elec- trode material in electrochemical supercapacitors. For this purpose, we have employed graphene prepared.

  8. SURFACE PROPERTIES OF ELECTROCHEMICALLY REDUCED ...

    African Journals Online (AJOL)

    DJFLEX

    A viscose rayon based activated carbon cloth (ACC) was electrochemically reduced ..... bath of liquid nitrogen at a temperature of 77 K. ... that above 59,400 c/g extent of oxidation, the ..... ACC react with aldehyde groups to produce ether.

  9. ELECTROCHEMICAL DETERMINATION OF ETHANOL, 2 ...

    African Journals Online (AJOL)

    2014-12-31

    Dec 31, 2014 ... ABSTRACT. In this work, we present the modification of a glassy carbon electrode with nickel oxide film which is performed in two successive steps. In the first one, the electrochemical deposition of metallic nickel on the glassy carbon electrode (GCE) is achieved in 0.1M boric acid; in the second step, the ...

  10. Nanomaterials application in electrochemical detection of heavy metals

    International Nuclear Information System (INIS)

    Aragay, Gemma; Merkoçi, Arben

    2012-01-01

    Highlights: ► We review the recent trends in the application of nanomaterials for electrochemical detection of heavy metals. ► Different types of nanomaterials including metal nanoparticles, different carbon nanomaterials or nanochannels have been applied on the electrochemical analysis of heavy metals in various sensing formats/configurations. ► The great properties of nanomaterials allow the new devices to show advantages in terms of sensing performance (i.e. increase the sensitivity, decrease the detection limits and improve the stability). ► Between the various electrochemical techniques, voltammetric and potentiometric based ones are particularly taking interesting advantages by the incorporation of new nanomaterials due to the improved electrocatalytic properties beside the increase of the sensor's transducing area. - Abstract: Recent trends in the application of nanomaterials for electrochemical detection of heavy metals are shown. Various nanomaterials such as nanoparticles, nanowires, nanotubes, nanochannels, graphene, etc. have been explored either as modifiers of electrodes or as new electrode materials with interest to be applied in electrochemical stripping analysis, ion-selective detection, field-effect transistors or other indirect heavy metals (bio)detection alternatives. The developed devices have shown increased sensitivity and decreased detection limits between other improvements of analytical performance data. The phenomena behind nanomaterials responses are also discussed and some typical responses data of the developed systems either in standard solutions or in real samples are given. The developed nanomaterials based electrochemical systems are giving new inputs to the existing devices or leading to the development of novel heavy metal detection tools with interest for applications in field such as diagnostics, environmental and safety and security controls or other industries.

  11. Electrochemical extraction of samarium from molten chlorides in pyrochemical processes

    International Nuclear Information System (INIS)

    Castrillejo, Y.; Fernandez, P.; Medina, J.; Hernandez, P.; Barrado, E.

    2011-01-01

    This work concerns the electrochemical extraction of samarium from molten chlorides. In this way, the electrochemical behaviour of samarium ions has been investigated in the eutectic LiCl-KCl at the surface of tungsten, aluminium and aluminium coated tungsten electrodes. On a W inert electrode the electro-reduction of Sm(III) takes place in only one soluble-soluble electrochemical step Sm(III)/Sm(II). The electrochemical system Sm(II)/Sm(0) has not been observed within the electrochemical window, because of the prior reduction of Li(I) ions from the solvent, which inhibits the electro-extraction of Sm species from the salt on such a substrate. Sm metal in contact with the melt react to give Li(0) according to the reaction: Sm(0) + 2Li(I) ↔ Sm(II) + 2Li(0). On the contrary, on reactive Al electrodes the electrochemical system Sm(II)/Sm(0) was observed within the electroactive range. The potential shift of the redox couple is caused by the decrease of Sm activity in the metal phase due to the formation of Sm-Al alloys at the interface. The formation mechanism of the intermetallic compounds was studied in a melt containing: (i) both Sm(III) and Al(III) ions, using W and Al coated tungsten electrodes, and (ii) Sm(III) ions using an Al electrode. Analysis of the samples after potentiostatic electrolysis by X-ray diffraction and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), allowed the identification of Al 3 Sm and Al 2 Sm.

  12. Electrochemical extraction of samarium from molten chlorides in pyrochemical processes

    Energy Technology Data Exchange (ETDEWEB)

    Castrillejo, Y., E-mail: ycastril@qa.uva.es [QUIANE/Dept Quimica Analitica, F. de Ciencias, Universidad de Valladolid, Prado de la Magdalena s/n, 47005 Valladolid (Spain); Fernandez, P. [QUIANE/Dept Quimica Analitica, F. de Ciencias, Universidad de Valladolid, Prado de la Magdalena s/n, 47005 Valladolid (Spain); Medina, J. [Dept Fisica Materia Condensada Cristalografia y Mineralogia, F. de Ciencias, Universidad de Valladolid, Prado de la Magdalena s/n, 47005 Valladolid (Spain); Hernandez, P. [Centro de Investigaciones Quimicas, Universidad Autonoma del Estado de Hidalgo, Carr. Pachuca-Tulancingo Km. 4.5, C.P. 42076 Pachuca, Hidalgo (Mexico); Barrado, E. [QUIANE/Dept Quimica Analitica, F. de Ciencias, Universidad de Valladolid, Prado de la Magdalena s/n, 47005 Valladolid (Spain)

    2011-10-01

    This work concerns the electrochemical extraction of samarium from molten chlorides. In this way, the electrochemical behaviour of samarium ions has been investigated in the eutectic LiCl-KCl at the surface of tungsten, aluminium and aluminium coated tungsten electrodes. On a W inert electrode the electro-reduction of Sm(III) takes place in only one soluble-soluble electrochemical step Sm(III)/Sm(II). The electrochemical system Sm(II)/Sm(0) has not been observed within the electrochemical window, because of the prior reduction of Li(I) ions from the solvent, which inhibits the electro-extraction of Sm species from the salt on such a substrate. Sm metal in contact with the melt react to give Li(0) according to the reaction: Sm(0) + 2Li(I) {r_reversible} Sm(II) + 2Li(0). On the contrary, on reactive Al electrodes the electrochemical system Sm(II)/Sm(0) was observed within the electroactive range. The potential shift of the redox couple is caused by the decrease of Sm activity in the metal phase due to the formation of Sm-Al alloys at the interface. The formation mechanism of the intermetallic compounds was studied in a melt containing: (i) both Sm(III) and Al(III) ions, using W and Al coated tungsten electrodes, and (ii) Sm(III) ions using an Al electrode. Analysis of the samples after potentiostatic electrolysis by X-ray diffraction and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), allowed the identification of Al{sub 3}Sm and Al{sub 2}Sm.

  13. The atomic force microscope as a mechano–electrochemical pen

    Directory of Open Access Journals (Sweden)

    Christian Obermair

    2011-10-01

    Full Text Available We demonstrate a method that allows the controlled writing of metallic patterns on the nanometer scale using the tip of an atomic force microscope (AFM as a “mechano–electrochemical pen”. In contrast to previous experiments, no voltage is applied between the AFM tip and the sample surface. Instead, a passivated sample surface is activated locally due to lateral forces between the AFM tip and the sample surface. In this way, the area of tip–sample interaction is narrowly limited by the mechanical contact between tip and sample, and well-defined metallic patterns can be written reproducibly. Nanoscale structures and lines of copper were deposited, and the line widths ranged between 5 nm and 80 nm, depending on the deposition parameters. A procedure for the sequential writing of metallic nanostructures is introduced, based on the understanding of the passivation process. The mechanism of this mechano–electrochemical writing technique is investigated, and the processes of site-selective surface depassivation, deposition, dissolution and repassivation of electrochemically deposited nanoscale metallic islands are studied in detail.

  14. The nuclear reaction matrix

    International Nuclear Information System (INIS)

    Krenciglowa, E.M.; Kung, C.L.; Kuo, T.T.S.; Osnes, E.; and Department of Physics, State University of New York at Stony Brook, Stony Brook, New York 11794)

    1976-01-01

    Different definitions of the reaction matrix G appropriate to the calculation of nuclear structure are reviewed and discussed. Qualitative physical arguments are presented in support of a two-step calculation of the G-matrix for finite nuclei. In the first step the high-energy excitations are included using orthogonalized plane-wave intermediate states, and in the second step the low-energy excitations are added in, using harmonic oscillator intermediate states. Accurate calculations of G-matrix elements for nuclear structure calculations in the Aapprox. =18 region are performed following this procedure and treating the Pauli exclusion operator Q 2 /sub p/ by the method of Tsai and Kuo. The treatment of Q 2 /sub p/, the effect of the intermediate-state spectrum and the energy dependence of the reaction matrix are investigated in detail. The present matrix elements are compared with various matrix elements given in the literature. In particular, close agreement is obtained with the matrix elements calculated by Kuo and Brown using approximate methods

  15. Change of Pore-Fracture Structure of Anthracite Modified by Electrochemical Treatment Using Micro-CT

    Directory of Open Access Journals (Sweden)

    Xianfa Kong

    2018-01-01

    Full Text Available The electrochemical method can strengthen gas desorption and seepage from coal. The study on change of the pore-fracture structure of coal after electrochemical modification can help to reveal the mechanism. Anthracite was modified by the electrochemical method using our own self-developed experiment apparatus. The pore-fracture structure of modified samples was measured by micro-CT. Combined with the Matlab software, its characteristics such as pore number, porosity, and average pore diameter were analyzed. The results show that (1 the number of fractures in modified coal samples increases. The shape of new fractures in samples in the anodic and cathodic zones was irregular voids and striola, respectively. The effect of electrochemical treatment on the section of samples close to the electrode is relatively obvious. (2 With increasing pore size, the number of pores in samples changes according to negative exponential rules. After electrochemical modification, the porosity of modified samples in the anodic zone increases from 11.88% to 31.65%, and the porosity of modified samples in the cathodic zone increases from 12.13% to 36.71%. (3 The main reason for the increase in the number of pores of coal samples in the anodic and cathodic zones is the treatment of electrolytic dissolution of minerals and electrophoretic migration of charged particles, respectively.

  16. Matrix Metalloproteinase Enzyme Family

    Directory of Open Access Journals (Sweden)

    Ozlem Goruroglu Ozturk

    2013-04-01

    Full Text Available Matrix metalloproteinases play an important role in many biological processes such as embriogenesis, tissue remodeling, wound healing, and angiogenesis, and in some pathological conditions such as atherosclerosis, arthritis and cancer. Currently, 24 genes have been identified in humans that encode different groups of matrix metalloproteinase enzymes. This review discuss the members of the matrix metalloproteinase family and their substrate specificity, structure, function and the regulation of their enzyme activity by tissue inhibitors. [Archives Medical Review Journal 2013; 22(2.000: 209-220

  17. Matrix groups for undergraduates

    CERN Document Server

    Tapp, Kristopher

    2005-01-01

    Matrix groups touch an enormous spectrum of the mathematical arena. This textbook brings them into the undergraduate curriculum. It makes an excellent one-semester course for students familiar with linear and abstract algebra and prepares them for a graduate course on Lie groups. Matrix Groups for Undergraduates is concrete and example-driven, with geometric motivation and rigorous proofs. The story begins and ends with the rotations of a globe. In between, the author combines rigor and intuition to describe basic objects of Lie theory: Lie algebras, matrix exponentiation, Lie brackets, and maximal tori.

  18. Elementary matrix theory

    CERN Document Server

    Eves, Howard

    1980-01-01

    The usefulness of matrix theory as a tool in disciplines ranging from quantum mechanics to psychometrics is widely recognized, and courses in matrix theory are increasingly a standard part of the undergraduate curriculum.This outstanding text offers an unusual introduction to matrix theory at the undergraduate level. Unlike most texts dealing with the topic, which tend to remain on an abstract level, Dr. Eves' book employs a concrete elementary approach, avoiding abstraction until the final chapter. This practical method renders the text especially accessible to students of physics, engineeri

  19. Yersinia enterocolitica in Diagnostic Fecal Samples from European Dogs and Cats: Identification by Fourier Transform Infrared Spectroscopy and Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry

    OpenAIRE

    Stamm, Ivonne; Hailer, Mandy; Depner, Barbara; Kopp, Peter A.; Rau, Jörg

    2013-01-01

    Yersinia enterocolitica is the main cause of yersiniosis in Europe, one of the five main bacterial gastrointestinal diseases of humans. Beside pigs, companion animals, especially dogs and cats, were repeatedly discussed in the past as a possible source of pathogenic Y. enterocolitica. To investigate the presence and types of Y. enterocolitica in companion animals, a total of 4,325 diagnostic fecal samples from dogs and 2,624 samples from cats were tested. The isolates obtained were differenti...

  20. Voltammetric sensor for electrochemical determination of the floral origin of honey based on a zinc oxide nanoparticle modified carbon paste electrode

    Directory of Open Access Journals (Sweden)

    K. Tiwari

    2018-04-01

    Full Text Available A new methodology based on cyclic voltammetry using a chemically modified electrode has been developed for the discrimination of the floral origin of honey. This method involves an electronic tongue with an electrochemical sensor made from a carbon paste (CPs electrode where zinc oxide (ZnO nanoparticles are used as an electroactive binder material. The bare CPs electrode is evaluated for comparison. The electrochemical response of the modified electrode in 50 samples of five different floral types of honey has been analysed by the cyclic voltammetric technique. The voltammograms of each floral variety of honey reflect the redox properties of the ZnO nanoparticles present inside the carbon paste matrix and are strongly influenced by the nectar source of honey. Thus, each type of honey provides a characteristic signal which is evaluated by using principal component analysis (PCA and an artificial neural network (ANN. The result of a PCA score plot of the transient responses obtained from the modified carbon paste electrode clearly shows discrimination among the different floral types of honey. The ANN model for floral classification of honey shows more than 90 % accuracy. These results indicate that the ZnO nanoparticles modified carbon paste (ZnO Nps modified CPs electrode can be a useful electrode for discrimination of honey samples from different floral origins.

  1. Electrochemically adsorbed Pb on Ag (111) studied with grazing- incidence x-ray scattering

    International Nuclear Information System (INIS)

    Kortright, J.B.; Ross, P.N.; Melroy, O.R.; Toney, M.F.; Borges, G.L.; Samant, M.G.

    1989-04-01

    Grazing-incidence x-ray scattering studies of the evolution of electrochemically deposited layers of lead on silver (111) as a function of applied electrochemical potential are presented. Measurements were made with the adsorbed layers in contact with solution in a specially designed sample cell. The observed lead structures are a function of the applied potential and range from an incommensurate monolayer, resulting from underpotential deposition, to randomly oriented polycrystalline bulk lead, resulting from lower deposition potentials. These early experiments demonstrate the ability of in situ x-ray diffraction measurements to determine structures associated with electrochemical deposition. 6 refs., 4 figs

  2. Design of an electrochemical cell for in situ XAS studies

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, N. [Instituto de Quimica, Universidade Estadual de Campinas (UNICAMP), Box 6154, CEP 13083-970, Campinas, SP (Brazil); Morais, J. [Instituto de Fisica, Universidade Federal do Rio Grande do Sul (UFRGS), Avenida Bento Goncalves, 9500, Bairro Agronomia, CP 15051, CEP 91501-970, Porto Alegre, RS (Brazil); Alves, M.C.M. [Instituto de Quimica, Universidade Federal do Rio Grande do Sul (UFRGS), Avenida Bento Goncalves, 9500, Bairro Agronomia, CP 15003, CEP 91501-970, Porto Alegre, RS (Brazil)], E-mail: maria@iq.ufrgs.br

    2007-05-15

    In situ X-ray absorption spectroscopy (XAS) studies have been carried out on the electrochemical insertion of Co metal particles in polypyrrole. This has become possible due to the development of an electrochemical cell to allow XAS studies in fluorescence geometry under steady-state conditions. The experimental set-up allows the in situ monitoring of the structural and electronic changes of the selected atom in a matrix. The project of the electrochemical cell is presented with the results obtained at different stages of the electrochemical process. XANES and EXAFS results showed that the initial stage of the cobalt insertion in polypyrrole took place in an ionic form, like [-[(C{sub 4}H{sub 2}N){sub 3}CH{sub 3}(CH{sub 2}){sub 11}OSO{sub 3}{sup -}]{sub 6}Co{sup 2+}] with posterior reduction to a metallic form. The quantitative analysis of the first shell shows that, at -0.60 V, the cobalt atoms are surrounded by 6 ({+-}0.5) atoms located at 2.12 ({+-}0.05) A with a large Debye-Waller factor ({sigma}{sup 2}) value of 0.0368 ({+-}0.0074). At -0.80 V, two distances of R = 1.99 ({+-}0.01) and R = 2.50 ({+-}0.01) A show the coexistence of cobalt in the oxidized and reduced (Co{sup 0}) forms. The Co-Co distance corresponds to that of bulk cobalt. At -1.20 V, the obtained values of N = 12 ({+-}0.5) and R = 2.56 ({+-}0.01) A and a Debye-Waller factor of 0.0176 ({+-}0.0004) suggest the formation of metallic cobalt in a quite disordered form.

  3. Isolation of HL-60 cancer cells from the human serum sample using MnO2-PEI/Ni/Au/aptamer as a novel nanomotor and electrochemical determination of thereof by aptamer/gold nanoparticles-poly(3,4-ethylene dioxythiophene) modified GC electrode.

    Science.gov (United States)

    Amouzadeh Tabrizi, Mahmoud; Shamsipur, Mojtaba; Saber, Reza; Sarkar, Saeed

    2018-07-01

    Herein, aptamer-modified self-propelled nanomotors were used for transportation of human promyelocytic leukemia cells (HL-60) from a human serum sample. For this purpose, the fabricated manganese oxide nanosheets-polyethyleneimine decorated with nickel/gold nanoparticles (MnO 2 -PEI/Ni/Au) as nanomotors were added to a vial containing thiolated aptamer KH1C12 solution as a capture aptamer to attach to the gold nanoparticles on the surface of nanomotors covalently. The aptamer-modified self-propelled nanomotors (aptamer KH1C12 /nanomotors) were then separated by placing the vial in a magnetic stand. The aptamer-modified self-propelled nanomotors were rinsed three times with water to remove the non-attached aptamers. Then, the resulting aptamer KH1C12 /nanomotors were applied for the on-the-fly" transporting of HL-60 cancer cell from a human serum sample. To release of the captured HL-60 cancer cells, the complementary nucleotide sequences of KH1C12 aptamer solution (releasing aptamer) that has a with capture aptamer was added to phosphate buffer solution (1 M, pH 7.4) containing HL-60/aptamer KH1C12 /nanomotors. Because of the high affinity of capture aptamer to complementary nucleotide sequences of aptamer KH1C12 , the HL-60 cancer cells released on the surface of aptamer KH1C12 /nanomotors into the solution. The second goal of the present work was determining the concentration of HL-60 cancer cell in the human serum samples. The electrochemical impedance spectroscopy technique (EIS) was used for the determination of HL-60 cancer cell. The concentration of separated cancer cell was determined by aptamer/gold nanoparticles-poly(3,4-ethylene dioxythiophene) modified GC electrode (GC/PEDOT-Au nano /aptamer KH1C12 ). The proposed aptasensor exhibited a good response to the concentration of HL-60 cancer cells in the range of 2.5 × 10 1 to 5 × 10 5 cells mL -1 with a low limit of detection of 250 cells mL -1 . Copyright © 2018 Elsevier B.V. All rights reserved.

  4. Opto-electrochemical spectroscopy of metals in aqueous solutions

    International Nuclear Information System (INIS)

    Habib, K.

    2016-01-01

    In the present investigation, holographic interferometry was utilized for the first time to determine the rate change of the electrical resistance of aluminium samples during the initial stage of anodisation processes in aqueous solution. In fact, because the resistance values in this investigation were obtained by holographic interferometry, electromagnetic method rather than electronic method, the abrupt rate change of the resistance was called electrical resistance–emission spectroscopy. The anodisation process of the aluminium samples was carried out by electrochemical impedance spectroscopy (EIS) in different sulphuric acid concentrations (1.0%–2.5% H 2 SO 4 ) at room temperature. In the meantime, the real time holographic interferometry was used to determine the difference between the electrical resistance of two subsequent values, dR, as a function of the elapsed time of the EIS experiment for the aluminium samples in 1.0%, 1.5%, 2.0%, and 2.5% H 2 SO 4 solutions. The electrical resistance–emission spectra of the present investigation represent a detailed picture of not only the rate change of the electrical resistance throughout the anodisation processes but also the spectra represent the rate change of the growth of the oxide films on the aluminium samples in different solutions. As a result, a new spectrometer was developed based on the combination of the holographic interferometry and electrochemical impedance spectroscopy for studying in situ the electrochemical behavior of metals in aqueous solutions.

  5. A PVC/polypyrrole sensor designed for beef taste detection using electrochemical methods and sensory evaluation.

    Science.gov (United States)

    Zhu, Lingtao; Wang, Xiaodan; Han, Yunxiu; Cai, Yingming; Jin, Jiahui; Wang, Hongmei; Xu, Liping; Wu, Ruijia

    2018-03-01

    An electrochemical sensor for detection of beef taste was designed in this study. This sensor was based on the structure of polyvinyl chloride/polypyrrole (PVC/PPy), which was polymerized onto the surface of a platinum (Pt) electrode to form a Pt-PPy-PVC film. Detecting by electrochemical methods, the sensor was well characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The sensor was applied to detect 10 rib-eye beef samples and the accuracy of the new sensor was validated by sensory evaluation and ion sensor detection. Several cluster analysis methods were used in the study to distinguish the beef samples. According to the obtained results, the designed sensor showed a high degree of association of electrochemical detection and sensory evaluation, which proved a fast and precise sensor for beef taste detection. Copyright © 2017 Elsevier Ltd. All rights reserved.

  6. Max–min distance nonnegative matrix factorization

    KAUST Repository

    Wang, Jim Jing-Yan; Gao, Xin

    2014-01-01

    Nonnegative Matrix Factorization (NMF) has been a popular representation method for pattern classification problems. It tries to decompose a nonnegative matrix of data samples as the product of a nonnegative basis matrix and a nonnegative coefficient matrix. The columns of the coefficient matrix can be used as new representations of these data samples. However, traditional NMF methods ignore class labels of the data samples. In this paper, we propose a novel supervised NMF algorithm to improve the discriminative ability of the new representation by using the class labels. Using the class labels, we separate all the data sample pairs into within-class pairs and between-class pairs. To improve the discriminative ability of the new NMF representations, we propose to minimize the maximum distance of the within-class pairs in the new NMF space, and meanwhile to maximize the minimum distance of the between-class pairs. With this criterion, we construct an objective function and optimize it with regard to basis and coefficient matrices, and slack variables alternatively, resulting in an iterative algorithm. The proposed algorithm is evaluated on three pattern classification problems and experiment results show that it outperforms the state-of-the-art supervised NMF methods.

  7. Max–min distance nonnegative matrix factorization

    KAUST Repository

    Wang, Jim Jing-Yan

    2014-10-26

    Nonnegative Matrix Factorization (NMF) has been a popular representation method for pattern classification problems. It tries to decompose a nonnegative matrix of data samples as the product of a nonnegative basis matrix and a nonnegative coefficient matrix. The columns of the coefficient matrix can be used as new representations of these data samples. However, traditional NMF methods ignore class labels of the data samples. In this paper, we propose a novel supervised NMF algorithm to improve the discriminative ability of the new representation by using the class labels. Using the class labels, we separate all the data sample pairs into within-class pairs and between-class pairs. To improve the discriminative ability of the new NMF representations, we propose to minimize the maximum distance of the within-class pairs in the new NMF space, and meanwhile to maximize the minimum distance of the between-class pairs. With this criterion, we construct an objective function and optimize it with regard to basis and coefficient matrices, and slack variables alternatively, resulting in an iterative algorithm. The proposed algorithm is evaluated on three pattern classification problems and experiment results show that it outperforms the state-of-the-art supervised NMF methods.

  8. Hacking the Matrix.

    Science.gov (United States)

    Czerwinski, Michael; Spence, Jason R

    2017-01-05

    Recently in Nature, Gjorevski et al. (2016) describe a fully defined synthetic hydrogel that mimics the extracellular matrix to support in vitro growth of intestinal stem cells and organoids. The hydrogel allows exquisite control over the chemical and physical in vitro niche and enables identification of regulatory properties of the matrix. Copyright © 2017 Elsevier Inc. All rights reserved.

  9. The Matrix Organization Revisited

    DEFF Research Database (Denmark)

    Gattiker, Urs E.; Ulhøi, John Parm

    1999-01-01

    This paper gives a short overview of matrix structure and technology management. It outlines some of the characteristics and also points out that many organizations may actualy be hybrids (i.e. mix several ways of organizing to allocate resorces effectively).......This paper gives a short overview of matrix structure and technology management. It outlines some of the characteristics and also points out that many organizations may actualy be hybrids (i.e. mix several ways of organizing to allocate resorces effectively)....

  10. The Exopolysaccharide Matrix

    Science.gov (United States)

    Koo, H.; Falsetta, M.L.; Klein, M.I.

    2013-01-01

    Many infectious diseases in humans are caused or exacerbated by biofilms. Dental caries is a prime example of a biofilm-dependent disease, resulting from interactions of microorganisms, host factors, and diet (sugars), which modulate the dynamic formation of biofilms on tooth surfaces. All biofilms have a microbial-derived extracellular matrix as an essential constituent. The exopolysaccharides formed through interactions between sucrose- (and starch-) and Streptococcus mutans-derived exoenzymes present in the pellicle and on microbial surfaces (including non-mutans) provide binding sites for cariogenic and other organisms. The polymers formed in situ enmesh the microorganisms while forming a matrix facilitating the assembly of three-dimensional (3D) multicellular structures that encompass a series of microenvironments and are firmly attached to teeth. The metabolic activity of microbes embedded in this exopolysaccharide-rich and diffusion-limiting matrix leads to acidification of the milieu and, eventually, acid-dissolution of enamel. Here, we discuss recent advances concerning spatio-temporal development of the exopolysaccharide matrix and its essential role in the pathogenesis of dental caries. We focus on how the matrix serves as a 3D scaffold for biofilm assembly while creating spatial heterogeneities and low-pH microenvironments/niches. Further understanding on how the matrix modulates microbial activity and virulence expression could lead to new approaches to control cariogenic biofilms. PMID:24045647

  11. Bio-inspired materials for electrochemical devices

    Science.gov (United States)

    Pawlicka, A.; Firmino, A.; Sentanin, F.; Sabadini, R. C.; Jimenez, D. E. Q.; Jayme, C. C.; Mindroiu, M.; Zgarian, R. G.; Tihan, G. T.; Rau, I.; Silva, M. M.; Nogueira, A. F.; Kanicki, J.; Kajzar, F.

    2015-10-01

    Natural macromolecules are very promising row materials to be used in modern technology including security and defense. They are abundant in nature, easy to extract and possess biocompatibility and biodegradability properties. These materials can be modified throughout chemical or physical processes, and can be doped with lithium and rare earth salts, ionic liquids, organic and inorganic acids. In this communication samples of DNA and modified DNA were doped with Prussian Blue (PB), poly(ethylene dioxythiophene) (PEDOT), europium and erbium triflate and organic dyes such as Nile Blue (NB), Disperse Red 1 (DR1) and Disperse Orange 3 (DO3). The colored or colorless membranes were characterized by electrochemical and spectroscopic measurements, and they were applied in electrochromic devices (ECDs) and dye sensitized solar cells (DSSC). ECDs change the color under applied potential, so they can modulate the intensity of transmitted light of 15 to 35%. As the electrochromic materials, WO3 or Prussian blue (PB), are usually blue colored, the color change is from transparent to blue. DNA, and the complexes: DNA-CTMA, DNA-DODA and DNAPEDOT: PSS were also investigated as either hole carrier material (HTM) or polymer electrolyte in dye-sensitized solar cells (DSSC). The DNA-based samples as HTM in small DSSCs revealed a solar energy conversion efficiency of 0.56%. Polymer electrolytes of DNA-CTMA and DNA-DODA, both with 10 wt% of LiI/I2, applied in small DSSC, exhibited the efficiencies of 0.18 and 0.66%, respectively. The obtained results show that natural macromolecules-based membranes are not only environmentally friendly but are also promising materials to be investigated for several electrochemical devices. However, to obtain better performances more research is still needed.

  12. Electrochemical sensing platforms based on the different carbon derivative incorporated interface.

    Science.gov (United States)

    Dervisevic, Muamer; Çevik, Emre; Durmuş, Zehra; Şenel, Mehmet

    2016-01-01

    their effects on the properties of these biosensors. Biosensors were prepared by Horseradish peroxidase (HRP) immobilization on the composite electrodes composed of carbon black, carbon nanofiber (CNF), extended graphite, multiwalled carbon nanotube (MWCNT), reduced graphene oxide (REGO) and poly(glycidyl methacrylateco-vinylferrocene) (P(GMA-co-VFc)) as mediator, covalent linker, and host matrix for carbon derivatives. The modified pencil graphite electrode (PGE) was used for the detection of hydrogen peroxide and to follow electrochemical behavior of different carbon derivatives which were recorded. The electrochemical characterization was investigated by cyclic voltammetry and electrochemical impedance spectroscopy methods. Amperometric measurements showed that the REGO and MWCNT modified electrodes have excellent performance in comparison with other carbon derivatives studied.

  13. Nanometer-scale mapping of irreversible electrochemical nucleation processes on solid Li-ion electrolytes

    Science.gov (United States)

    Kumar, Amit; Arruda, Thomas M.; Tselev, Alexander; Ivanov, Ilia N.; Lawton, Jamie S.; Zawodzinski, Thomas A.; Butyaev, Oleg; Zayats, Sergey; Jesse, Stephen; Kalinin, Sergei V.

    2013-01-01

    Electrochemical processes associated with changes in structure, connectivity or composition typically proceed via new phase nucleation with subsequent growth of nuclei. Understanding and controlling reactions requires the elucidation and control of nucleation mechanisms. However, factors controlling nucleation kinetics, including the interplay between local mechanical conditions, microstructure and local ionic profile remain inaccessible. Furthermore, the tendency of current probing techniques to interfere with the original microstructure prevents a systematic evaluation of the correlation between the microstructure and local electrochemical reactivity. In this work, the spatial variability of irreversible nucleation processes of Li on a Li-ion conductive glass-ceramics surface is studied with ~30 nm resolution. An increased nucleation rate at the boundaries between the crystalline AlPO4 phase and amorphous matrix is observed and attributed to Li segregation. This study opens a pathway for probing mechanisms at the level of single structural defects and elucidation of electrochemical activities in nanoscale volumes. PMID:23563856

  14. Electrochemical affinity biosensors for detection of mycotoxins: A review.

    Science.gov (United States)

    Vidal, Juan C; Bonel, Laura; Ezquerra, Alba; Hernández, Susana; Bertolín, Juan R; Cubel, Carlota; Castillo, Juan R

    2013-11-15

    This review discusses the current state of electrochemical biosensors in the determination of mycotoxins in foods. Mycotoxins are highly toxic secondary metabolites produced by molds. The acute toxicity of these results in serious human and animal health problems, although it has been only since early 1960s when the first studied aflatoxins were found to be carcinogenic. Mycotoxins affect a broad range of agricultural products, most important cereals and cereal-based foods. A majority of countries, mentioning especially the European Union, have established preventive programs to control contamination and strict laws of the permitted levels in foods. Official methods of analysis of mycotoxins normally requires sophisticated instrumentation, e.g. liquid chromatography with fluorescence or mass detectors, combined with extraction procedures for sample preparation. For about sixteen years, the use of simpler and faster analytical procedures based on affinity biosensors has emerged in scientific literature as a very promising alternative, particularly electrochemical (i.e., amperometric, impedance, potentiometric or conductimetric) affinity biosensors due to their simplicity and sensitivity. Typically, electrochemical biosensors for mycotoxins use specific antibodies or aptamers as affinity ligands, although recombinant antibodies, artificial receptors and molecular imprinted polymers show potential utility. This article deals with recent advances in electrochemical affinity biosensors for mycotoxins and covers complete literature from the first reports about sixteen years ago. Copyright © 2013 Elsevier B.V. All rights reserved.

  15. Study on the electrochemical of the metal deposition from ionic liquids for lithium, titanium and dysprosium

    International Nuclear Information System (INIS)

    Berger, Claudia A.

    2017-01-01

    The thesis was aimed to the characterization of electrochemically deposited film of lithium, titanium and dysprosium on Au(111) from different ionic liquids, finally dysprosium on neodymium-iron-boron magnate for industrial applications. The investigation of the deposits were performed using cyclic voltametry, in-situ scanning tunneling microscopy, electrochemical quartz microbalance, XPS and Auger electron spectroscopy. The sample preparation is described in detail. The deposition rate showed a significant temperature dependence.

  16. Continuous glucose monitoring microsensor with a nanoscale conducting matrix and redox mediator

    Science.gov (United States)

    Pesantez, Daniel

    vitro testing for glucose shows increasing current with increasing analyte concentration. Testing the glucose microsensor with known concentrations of glucose over a period of 48 hours demonstrated both the potential durability and sensitivity of the device. Unknown/blind in vitro glucose experiments showed the reproducibility and accuracy of the microsensor to detect various glucose levels. Thinner polymer matrix films lead to better sensing performance during in vitro tests (0.6nA/mM lower limit sensitivity and 0.2nA/mM upper limit sensitivity). In vitro experiments using electroactive ascorbic acid (AA) and uric acid (UA) showed the selectivity of the sensor for glucose. In an effort to reduce the sensor's oxidation potential (0.7V) and noise, a second generation electron transfer approach was developed by incorporating into a modified Platinum WE with a nanoscale PPy and GOx matrix, a redox mediator. Ferrocene (Fc) was selected as the artificial electron carrier, substituting molecular oxygen in the enzymatic reaction. The incorporation of Fc into the polymer matrix is done by a simple electrochemical synthesis. Modifications in the microsensor design, materials and fabrication process are presented. Experiments with the new sensor generation resulted in higher sensitivity values (22.8nA/mM lower limit sensitivity and 12.5nA/mM upper limit sensitivity) for glucose and noise was further eliminated by operating the sensor at a lower oxidation potential (0.3V). The final experimental work consisted of preliminary ex vivo tests with the MetaSense microdevice on bovine kidney samples, which showed a qualitatively correlation between glucose consumption trend profile during preservation and viability histology outcome.

  17. Electrochemical treatment of liquid wastes

    International Nuclear Information System (INIS)

    Hobbs, D.

    1996-01-01

    Electrochemical treatment processes are being evaluated and developed for the destruction of organic compounds and nitrates/nitrites and the removal of other hazardous species from liquid wastes stored throughout the DOE complex. This activity consists of five major tasks: (1) evaluation of different electrochemical reactors for the destruction and removal of hazardous waste components, (2) development and validation of engineering process models, (3) radioactive laboratory-scale tests, (4) demonstration of the technology in an engineering-scale size reactor, and (5) analysis and evaluation of testing data. The development program team is comprised of individuals from federal, academic, and private industry. Work is being carried out in DOE, academic, and private industrial laboratories

  18. Recent Advances in Electrochemical Glycobiosensing

    Directory of Open Access Journals (Sweden)

    Germarie Sánchez-Pomales

    2011-01-01

    Full Text Available Biosensors based on electrochemical transduction mechanisms have recently made advances into the field of glycan analysis. These glyco-biosensors offer simple, rapid, sensitive, and economical approaches to the measurement need for rapid glycan analysis for biomarker detection, cancer and disease diagnostics, and bioprocess monitoring of therapeutic glycoproteins. Although the prevalent methods of glycan analysis (high-performance liquid chromatography, mass spectrometry, and nuclear magnetic resonance spectroscopy provide detailed identification and structural analysis of glycan species, there are significantly few low-cost, rapid glycan assays available for diagnostic and screening applications. Here we review instances in which glyco-biosensors have been used for glycan analysis using a variety of electrochemical transduction mechanisms (e.g., amperometric, potentiometric, impedimetric, and voltammetric, selective binding agents (e.g., lectins and antibodies, and redox species (e.g., enzyme substrates, inorganic, and nanomaterial.

  19. Ultrasensitive multi-analyte electrochemical immunoassay based on GNR-modified heated screen-printed carbon electrodes and PS@PDA-metal labels for rapid detection of MMP-9 and IL-6.

    Science.gov (United States)

    Shi, Jian-Jun; He, Ting-Ting; Jiang, Fang; Abdel-Halim, E S; Zhu, Jun-Jie

    2014-05-15

    An ultrasensitive electrochemical immunoassay was developed for rapid detection of interleukin-6 (IL-6) and matrix metallopeptidase-9 (MMP-9); the method utilized PS@PDA-metal nanocomposites based on graphene nanoribbon (GNR)-modified heated screen-printed carbon electrode (HSPCE). Because of the good hydrophilicity and low toxicity, GNRs were used to immobilize antibodies (Ab) and amplify the electrochemical signal. PS@PDA-metal was used to label antibodies and generate a strong electrochemical signal in acetic buffer. A sandwich strategy was adopted to achieve simultaneous detection of MMP-9 and IL-6 based on HSPCE without cross-talk between adjacent electrodes in the range of 10(-5) to 10(3) ng mL(-1) with detection limits of 5 fg mL(-1) and 0.1 pg mL(-1) (S/N=3), respectively. The proposed method showed wide detection range, low detection limit, acceptable stability and good reproducibility. Satisfactory results were also obtained in the practical samples, thus showing this is a promising technique for simultaneous clinical detection of biocomponent proteins. © 2013 Elsevier B.V. All rights reserved.

  20. Electrochemical Applications in Metal Bioleaching.

    Science.gov (United States)

    Tanne, Christoph Kurt; Schippers, Axel

    2017-12-10

    Biohydrometallurgy comprises the recovery of metals by biologically catalyzed metal dissolution from solids in an aqueous solution. The application of this kind of bioprocessing is described as "biomining," referring to either bioleaching or biooxidation of sulfide metal ores. Acidophilic iron- and sulfur-oxidizing microorganisms are the key to successful biomining. However, minerals such as primary copper sulfides are recalcitrant to dissolution, which is probably due to their semiconductivity or passivation effects, resulting in low reaction rates. Thus, further improvements of the bioleaching process are recommendable. Mineral sulfide dissolution is based on redox reactions and can be accomplished by electrochemical technologies. The impact of electrochemistry on biohydrometallurgy affects processing as well as analytics. Electroanalysis is still the most widely used electrochemical application in mineralogical research. Electrochemical processing can contribute to bioleaching in two ways. The first approach is the coupling of a mineral sulfide to a galvanic partner or electrocatalyst (spontaneous electron transfer). This approach requires only low energy consumption and takes place without technical installations by the addition of higher redox potential minerals (mostly pyrite), carbonic material, or electrocatalytic ions (mostly silver ions). Consequently, the processed mineral (often chalcopyrite) is preferentially dissolved. The second approach is the application of electrolytic bioreactors (controlled electron transfer). The electrochemical regulation of electrolyte properties by such reactors has found most consideration. It implies the regulation of ferrous and ferric ion ratios, which further results in optimized solution redox potential, less passivation effects, and promotion of microbial activity. However, many questions remain open and it is recommended that reactor and electrode designs are improved, with the aim of finding options for simplified

  1. Composite Electrodes for Electrochemical Supercapacitors

    OpenAIRE

    Li, Jun; Yang, QuanMin; Zhitomirsky, Igor

    2010-01-01

    Abstract Manganese dioxide nanofibers with length ranged from 0.1 to 1 μm and a diameter of about 4–6 nm were prepared by a chemical precipitation method. Composite electrodes for electrochemical supercapacitors were fabricated by impregnation of the manganese dioxide nanofibers and multiwalled carbon nanotubes (MWCNT) into porous Ni plaque current collectors. Obtained composite electrodes, containing 85% of manganese dioxide and 15 mass% of MWCNT, as a conductive additive, with to...

  2. Electrochemical Design of Optical Nanoantennas

    Directory of Open Access Journals (Sweden)

    Vasilchenko V.E.

    2015-01-01

    Full Text Available Electrochemical techniques for fabricating tapered gold nanoantennas (tips are discussed. In the paper, the tunable design of nanoantennas is demonstrated. Tip parameters such as a tip apex curvature, mesoscopic morphology, aspect ratio and enhancement factor can be varied with etching electrolyte and applied voltage. The low-cost method makes tipehnahced optical spectroscopy and microscopy feasible for routine optical measurements beyond the diffraction limit.

  3. Electrodeposition as a sample preparation technique for TXRF analysis

    International Nuclear Information System (INIS)

    Griesel, S.; Reus, U.; Prange, A.

    2000-01-01

    TXRF analysis of trace elements at concentrations in the μg/L range and below in high salt matrices normally requires a number of sample preparation steps that include separation of the salt matrix and preconcentration of the trace elements. A neat approach which allows samples to be prepared straightforwardly in a single step involves the application of electrochemical deposition using the TXRF sample support itself as an electrode. For this work a common three-electrode arrangement (radiometer analytical) with a rotating disc electrode as the working electrode, as is frequently employed in voltametric analysis, has been used. A special electrode tip has been constructed as a holder for the sample carrier which consists of polished glassy carbon. This material has been proven to be suitable for both its electrical and chemical properties. Measurements of the trace elements were performed using the ATOMIKA 8030C TXRF spectrometer, with the option of variable incident angles. In first experiments an artificial sea water matrix containing various trace elements in the μg/L range has been used. Elements such as Cr, Mn, Fe, Co, Ni, Cu, Zn, Ag, Cd, Hg, and Pb deposited on glassy carbon carriers. The deposition can be optimized by controlling the potential of the working electrode with respect to the reference electrode. Metal ions with a suitable standard potential are reduced to the metallic state and plated onto the electrode surface. When deposition is finished the sample carrier is demounted, rinsed with ultra-pure water and measured directly. Deposition yields for the elements under investigation are quite similar, and with an appropriate choice of the reference element, quantification can be achieved directly by internal standardization. The influence of parameters such as time, pH value, and trace element concentration on the deposition yield has been examined, and the results will be presented along with reproducibility studies. (author)

  4. Ferrocene-Functionalized 4-(2,5-Di(thiophen-2-yl-1H-pyrrol-1-ylaniline: A Novel Design in Conducting Polymer-Based Electrochemical Biosensors

    Directory of Open Access Journals (Sweden)

    Rukiye Ayranci

    2015-01-01

    Full Text Available Herein, we report a novel ferrocenyldithiophosphonate functional conducting polymer and its use as an immobilization matrix in amperometric biosensor applications. Initially, 4-(2,5-di(thiophen-2-yl-1H-pyrrol-1-ylamidoferrocenyldithiophosphonate was synthesized and copolymerized with 4-(2,5-di(thiophen-2-yl-1H-pyrrol-1-ylbenzenamine at graphite electrodes. The amino groups on the polymer were utilized for covalent attachment of the enzyme glucose oxidase. Besides, ferrocene on the backbone was used as a redox mediator during the electrochemical measurements. Prior to the analytical characterization, optimization studies were carried out. The changes in current signals at +0.45 V were proportional to glucose concentration from 0.5 to 5.0 mM. Finally, the resulting biosensor was applied for glucose analysis in real samples and the data were compared with the spectrophotometric Trinder method.

  5. Study of theophylline stability on polymer matrix

    International Nuclear Information System (INIS)

    Rodrigues, Kiriaki M.S.; Parra, Duclerc F.; Oliveira, Maria Jose A.; Bustillos, Oscar V.; Lugao, Ademar B.

    2007-01-01

    Theophylline is a bronchodilator, commonly known and used as a drug model in the development of pharmaceutical formulations. The stability of the drug and the matrix, scope of this study, was evaluated in the solid formulation. Polymeric matrix based on PHB containing the drug (theophylline) was prepared and submitted to radiation sterilization at different doses of: 5, 10, 20 and 25 kGy using a Cobalt- 60 source. The modified drug release of theophylline sterilized tablets has been studied. Modern techniques of HPLC (High Pressure Liquid Chromatography), DSC (Differential scanning calorimetry) and TGA (Thermogravimetry analysis) were employed. The results have shown the influence of sterilization by radiation process in both the theophylline and the polymeric drug delivery matrix samples. The increasing of polymeric matrix crosslinking under radiation conditions retards the drug release while the theophylline structure is stable under the radiation (author)

  6. Electrochemical studies of ruthenium compounds

    International Nuclear Information System (INIS)

    Kumar Ghosh, B.; Chakravorty, A.

    1989-01-01

    In many ways the chemistry of transition metals is the chemistry of multiple oxidation states and the associated redox phenomena. If a particular element were to be singeld out to illustrate this viewpoint, a model choice would be ruthenium - an element that is directly or indirectly the active centre of a plethora of redox phenomena encompassing ten different oxidation states and a breathtaking diversity of structure and bonding. In the present review the authors are primarily concerned with the oxidation states of certain ligands coordinated to ruthenium. This choice is deliberate since this is one area where the unique power of electrochemical methods is splendidly revealed. Without these methods, development in this area would have been greatly hampered. A brief summary of metal oxidation states is also included as a prelude to the main subject of this review. The authors have generally emphasize the information derived which is of chemical interest leaving the details of formal electrochemical arguments in the background. The authors have reviewed the pattern and systematics of ligand redox in ruthenium complexes. The synergistic combination of electrochemical and spectroscopic methods have vastly increased our understanding of ligand phenomena during the last 15 years or so. This in turn has led to better understanding and new developments in other fields. Photophysics and photochemistry could be cited as examples. (author). 176 refs.; 10 figs.; 10 tabs

  7. Neutron dosimetry using electrochemical etching

    International Nuclear Information System (INIS)

    Su, S.J.; Stillwagon, G.B.; Morgan, K.Z.

    1977-01-01

    Registration of α-tracks and fast-neutron-induced recoils tracks by the electrochemical etching technique as applied to sensitive polymer foils (e.g., polycarbonate) provides a simple, sensitive and inexpensive means of fast neutron personnel dosimetry as well as a valuable research tool for microdosimetry. When tracks were amplified by our electrochemical technique and the etching results compared with conventional etching technique a striking difference was noted. The electrochemically etched tracks were of much larger diameter (approx. 100 μm) and gave superior contrast. Two optical devices--the transparency projector and microfiche reader--were adapted to facilitate counting of the tracks appearing on our polycarbonate foils. The projector produced a magnification of 14X for a screen to projector distance of 5.0 meter and read's magnification was 50X. A Poisson distribution was determined for the number of tracks located in a particular area of the foil and experimentally verified by random counting of quarter sections of the microfiche reader screen. Finally, in an effort to determine dose equivalent (rem), a conversion factor is being determined by finding the sensitivity response (tracks/neutron) of recoil particle induced tracks as a function of monoenergetic fast neutrons and comparing results with those obtained by others

  8. Electrochemical deposition of Prussian blue on hydrogen terminated silicon(111)

    International Nuclear Information System (INIS)

    Zhao Jianwei; Zhang Yan; Shi Chuanguo; Chen, Hongyuan; Tong Lianming; Zhu Tao; Liu Zhongfan

    2006-01-01

    Electrochemical deposition of Prussian blue (PB) was performed by cyclic voltammetry on hydrogen terminated n-type Si(111) surface. The characterization of the samples based on atomic force microscopy and X-ray diffraction spectroscopy showed a nanocrystal form of the PB films on the silicon surface. The thickness of PB films as a function of the potential cycling number was monitored simultaneously by Raman spectroscopy, proving that the growth of the films is in a good controllable manner

  9. Influence of electrochemical pre-treatment on highly reactive carbon nitride thin films deposited on stainless steel for electrochemical applications

    International Nuclear Information System (INIS)

    Benchikh, A.; Debiemme-Chouvy, C.; Cachet, H.; Pailleret, A.; Saidani, B.; Beaunier, L.; Berger, M.H.

    2012-01-01

    In this work, a-CNx films prepared by DC magnetron sputtering on stainless steel substrate have been investigated as electrode materials. While their wide potential window was confirmed as a property shared by boron doped diamond (BDD) electrodes, their electrochemical activity with respect to fast and reversible redox systems, [Ru(NH 3 ) 6 ] 3+/2+ , [Fe(CN) 6 ] 3−/4− and [IrCl 6 ] 2−/3− , was assessed by Electrochemical Impedance Spectroscopy (EIS) after cathodic or anodic electrochemical pre-treatments or for as grown samples. It was shown for the three systems that electrochemical reactivity of the a-CNx films was improved after the cathodic pre-treatment and degraded after the anodic one, the apparent heterogeneous rate constant k 0app being decreased by at least one order of magnitude for the latter case. A high k 0app value of 0.11 cm s −1 for [IrCl 6 ] 2−/3− was obtained, close to the highest values found for BDD electrodes.

  10. Electrochemical Biosensor for Nitrite Based on Polyacrylic-Graphene Composite Film with Covalently Immobilized Hemoglobin

    Directory of Open Access Journals (Sweden)

    Raja Zaidatul Akhmar Raja Jamaluddin

    2018-04-01

    Full Text Available A new biosensor for the analysis of nitrite in food was developed based on hemoglobin (Hb covalently immobilized on the succinimide functionalized poly(n-butyl acrylate-graphene [poly(nBA-rGO] composite film deposited on a carbon-paste screen-printed electrode (SPE. The immobilized Hb on the poly(nBA-rGO conducting matrix exhibited electrocatalytic ability for the reduction of nitrite with significant enhancement in the reduction peak at −0.6 V versus Ag/AgCl reference electrode. Thus, direct determination of nitrite can be achieved by monitoring the cathodic peak current signal of the proposed polyacrylic-graphene hybrid film-based voltammetric nitrite biosensor. The nitrite biosensor exhibited a reproducible dynamic linear response range from 0.05–5 mg L−1 nitrite and a detection limit of 0.03 mg L−1. No significant interference was observed by potential interfering ions such as Ca2+, Na+, K+, NH4+, Mg2+, and NO3− ions. Analysis of nitrite in both raw and processed edible bird’s nest (EBN samples demonstrated recovery of close to 100%. The covalent immobilization of Hb on poly(nBA-rGO composite film has improved the performance of the electrochemical nitrite biosensor in terms of broader detection range, lower detection limit, and prolonged biosensor stability.

  11. A novel bi-enzyme electrochemical biosensor for selective and sensitive determination of methyl salicylate.

    Science.gov (United States)

    Fang, Yi; Umasankar, Yogeswaran; Ramasamy, Ramaraja P

    2016-07-15

    An amperometric sensor based on a bi-enzyme modified electrode was fabricated to detect methyl salicylate, a volatile organic compound released by pathogen-infected plants via systemic response. The detection is based on cascadic conversion reactions that result in an amperometric electrochemical signal. The bi-enzyme electrode is made of alcohol oxidase and horseradish peroxidase enzymes immobilized on to a carbon nanotube matrix through a molecular tethering method. Methyl salicylate undergoes hydrolysis to form methanol, which is consumed by alcohol oxidase to form formaldehyde while simultaneously reducing oxygen to hydrogen peroxide. The hydrogen peroxide will be further reduced to water by horseradish peroxidase, which results in an amperometric signal via direct electron transfer. The bi-enzyme biosensor was evaluated by cyclic voltammetry and constant potential amperometry using hydrolyzed methyl salicylate as the analyte. The sensitivity of the bi-enzyme biosensor as determined by cyclic voltammetry and constant potential amperometry were 112.37 and 282.82μAcm(-2)mM(-1) respectively, and the corresponding limits of detection were 22.95 and 0.98μM respectively. Constant potential amperometry was also used to evaluate durability, repeatability and interference from other compounds. Wintergreen oil was used for real sample study to establish the application of the bi-enzyme sensor for selective determination of plant pathogen infections. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Matrix Information Geometry

    CERN Document Server

    Bhatia, Rajendra

    2013-01-01

    This book is an outcome of the Indo-French Workshop on Matrix Information Geometries (MIG): Applications in Sensor and Cognitive Systems Engineering, which was held in Ecole Polytechnique and Thales Research and Technology Center, Palaiseau, France, in February 23-25, 2011. The workshop was generously funded by the Indo-French Centre for the Promotion of Advanced Research (IFCPAR).  During the event, 22 renowned invited french or indian speakers gave lectures on their areas of expertise within the field of matrix analysis or processing. From these talks, a total of 17 original contribution or state-of-the-art chapters have been assembled in this volume. All articles were thoroughly peer-reviewed and improved, according to the suggestions of the international referees. The 17 contributions presented  are organized in three parts: (1) State-of-the-art surveys & original matrix theory work, (2) Advanced matrix theory for radar processing, and (3) Matrix-based signal processing applications.  

  13. Kinetic mechanism for modeling of electrochemical reactions.

    Science.gov (United States)

    Cervenka, Petr; Hrdlička, Jiří; Přibyl, Michal; Snita, Dalimil

    2012-04-01

    We propose a kinetic mechanism of electrochemical interactions. We assume fast formation and recombination of electron donors D- and acceptors A+ on electrode surfaces. These mediators are continuously formed in the electrode matter by thermal fluctuations. The mediators D- and A+, chemically equivalent to the electrode metal, enter electrochemical interactions on the electrode surfaces. Electrochemical dynamics and current-voltage characteristics of a selected electrochemical system are studied. Our results are in good qualitative agreement with those given by the classical Butler-Volmer kinetics. The proposed model can be used to study fast electrochemical processes in microsystems and nanosystems that are often out of the thermal equilibrium. Moreover, the kinetic mechanism operates only with the surface concentrations of chemical reactants and local electric potentials, which facilitates the study of electrochemical systems with indefinable bulk.

  14. A high-performance flexible fibre-shaped electrochemical capacitor based on electrochemically reduced graphene oxide.

    Science.gov (United States)

    Li, Yingru; Sheng, Kaixuan; Yuan, Wenjing; Shi, Gaoquan

    2013-01-11

    A fibre-shaped solid electrochemical capacitor based on electrochemically reduced graphene oxide has been fabricated, exhibiting high specific capacitance and rate capability, long cycling life and attractive flexibility.

  15. Applications of Nonlinear Electrochemical Impedance Spectroscopy (NLEIS)

    KAUST Repository

    Adler, S. B.

    2013-08-31

    This paper reviews the use of nonlinear electrochemical impedance spectroscopy (NLEIS) in the analysis of SOFC electrode reactions. By combining EIS and NLEIS, as well as other independent information about an electrode material, it becomes possible to establish quantitative links between electrochemical kinetics and materials properties, even when systems are unstable with time. After a brief review of the method, this paper summarizes recent results analyzing the effects of Sr segregation in thin-film LSC electrodes. © The Electrochemical Society.

  16. Fabrication of Micro Components by Electrochemical Deposition

    DEFF Research Database (Denmark)

    Tang, Peter Torben

    The main issue of this thesis is the combination of electrochemical deposition of metals and micro machining. Processes for electroplating and electroless plating of nickel and nickel alloys have been developed and optimised for compatibility with microelectronics and silicon based micromechanics...... of electrochemical machining and traditional machining is compared to micro machining techniques as performed in the field of microelectronics. Various practical solutions and equipment for electrochemical deposition of micro components are demonstrated, as well as the use and experience obtained utilising...

  17. Management of processes of electrochemical dimensional processing

    Science.gov (United States)

    Akhmetov, I. D.; Zakirova, A. R.; Sadykov, Z. B.

    2017-09-01

    In different industries a lot high-precision parts are produced from hard-processed scarce materials. Forming such details can only be acting during non-contact processing, or a minimum of effort, and doable by the use, for example, of electro-chemical processing. At the present stage of development of metal working processes are important management issues electrochemical machining and its automation. This article provides some indicators and factors of electrochemical machining process.

  18. Electrochemical ion separation in molten salts

    Science.gov (United States)

    Spoerke, Erik David; Ihlefeld, Jon; Waldrip, Karen; Wheeler, Jill S.; Brown-Shaklee, Harlan James; Small, Leo J.; Wheeler, David R.

    2017-12-19

    A purification method that uses ion-selective ceramics to electrochemically filter waste products from a molten salt. The electrochemical method uses ion-conducting ceramics that are selective for the molten salt cations desired in the final purified melt, and selective against any contaminant ions. The method can be integrated into a slightly modified version of the electrochemical framework currently used in pyroprocessing of nuclear wastes.

  19. A facile electrochemical intercalation and microwave assisted exfoliation methodology applied to screen-printed electrochemical-based sensing platforms to impart improved electroanalytical outputs.

    Science.gov (United States)

    Pierini, Gastón D; Foster, Christopher W; Rowley-Neale, Samuel J; Fernández, Héctor; Banks, Craig E

    2018-06-12

    Screen-printed electrodes (SPEs) are ubiquitous with the field of electrochemistry allowing researchers to translate sensors from the laboratory to the field. In this paper, we report an electrochemically driven intercalation process where an electrochemical reaction uses an electrolyte as a conductive medium as well as the intercalation source, which is followed by exfoliation and heating/drying via microwave irradiation, and applied to the working electrode of screen-printed electrodes/sensors (termed EDI-SPEs) for the first time. This novel methodology results in an increase of up to 85% of the sensor area (electrochemically active surface area, as evaluated using an outer-sphere redox probe). Upon further investigation, it is found that an increase in the electroactive area of the EDI-screen-printed based electrochemical sensing platforms is critically dependent upon the analyte and its associated electrochemical mechanism (i.e. adsorption vs. diffusion). Proof-of-concept for the electrochemical sensing of capsaicin, a measure of the hotness of chillies and chilli sauce, within both model aqueous solutions and a real sample (Tabasco sauce) is demonstrated in which the electroanalytical sensitivity (a plot of signal vs. concentration) is doubled when utilising EDI-SPEs over that of SPEs.

  20. Electrochemical Systems for Renewable Energy Conversion from Salinity and Proton Gradients

    OpenAIRE

    Morais, William G.; Lima, Gilberto; Gomes, Wellington J. A. S.; Huguenin, Fritz

    2018-01-01

    Ever-rising energy demand, fossil fuel dependence, and climate issues have harmful consequences to the society. Exploring clean and renewable energy to diversify the world energy matrix has become an urgent matter. Less explored or unexplored renewable energy sources like the salinity and proton gradient energy are an attractive alternative with great energy potential. This paper discusses important electrochemical systems for energy conversion from natural and artificial concentration gradie...

  1. 2016 MATRIX annals

    CERN Document Server

    Praeger, Cheryl; Tao, Terence

    2018-01-01

    MATRIX is Australia’s international, residential mathematical research institute. It facilitates new collaborations and mathematical advances through intensive residential research programs, each lasting 1-4 weeks. This book is a scientific record of the five programs held at MATRIX in its first year, 2016: Higher Structures in Geometry and Physics (Chapters 1-5 and 18-21); Winter of Disconnectedness (Chapter 6 and 22-26); Approximation and Optimisation (Chapters 7-8); Refining C*-Algebraic Invariants for Dynamics using KK-theory (Chapters 9-13); Interactions between Topological Recursion, Modularity, Quantum Invariants and Low-dimensional Topology (Chapters 14-17 and 27). The MATRIX Scientific Committee selected these programs based on their scientific excellence and the participation rate of high-profile international participants. Each program included ample unstructured time to encourage collaborative research; some of the longer programs also included an embedded conference or lecture series. The artic...

  2. Matrix interdiction problem

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Feng [Los Alamos National Laboratory; Kasiviswanathan, Shiva [Los Alamos National Laboratory

    2010-01-01

    In the matrix interdiction problem, a real-valued matrix and an integer k is given. The objective is to remove k columns such that the sum over all rows of the maximum entry in each row is minimized. This combinatorial problem is closely related to bipartite network interdiction problem which can be applied to prioritize the border checkpoints in order to minimize the probability that an adversary can successfully cross the border. After introducing the matrix interdiction problem, we will prove the problem is NP-hard, and even NP-hard to approximate with an additive n{gamma} factor for a fixed constant {gamma}. We also present an algorithm for this problem that achieves a factor of (n-k) mUltiplicative approximation ratio.

  3. Dynamic Matrix Rank

    DEFF Research Database (Denmark)

    Frandsen, Gudmund Skovbjerg; Frandsen, Peter Frands

    2009-01-01

    We consider maintaining information about the rank of a matrix under changes of the entries. For n×n matrices, we show an upper bound of O(n1.575) arithmetic operations and a lower bound of Ω(n) arithmetic operations per element change. The upper bound is valid when changing up to O(n0.575) entries...... in a single column of the matrix. We also give an algorithm that maintains the rank using O(n2) arithmetic operations per rank one update. These bounds appear to be the first nontrivial bounds for the problem. The upper bounds are valid for arbitrary fields, whereas the lower bound is valid for algebraically...... closed fields. The upper bound for element updates uses fast rectangular matrix multiplication, and the lower bound involves further development of an earlier technique for proving lower bounds for dynamic computation of rational functions....

  4. MATLAB matrix algebra

    CERN Document Server

    Pérez López, César

    2014-01-01

    MATLAB is a high-level language and environment for numerical computation, visualization, and programming. Using MATLAB, you can analyze data, develop algorithms, and create models and applications. The language, tools, and built-in math functions enable you to explore multiple approaches and reach a solution faster than with spreadsheets or traditional programming languages, such as C/C++ or Java. MATLAB Matrix Algebra introduces you to the MATLAB language with practical hands-on instructions and results, allowing you to quickly achieve your goals. Starting with a look at symbolic and numeric variables, with an emphasis on vector and matrix variables, you will go on to examine functions and operations that support vectors and matrices as arguments, including those based on analytic parent functions. Computational methods for finding eigenvalues and eigenvectors of matrices are detailed, leading to various matrix decompositions. Applications such as change of bases, the classification of quadratic forms and ...

  5. Graphene-Paper Based Electrochemical Sensors

    DEFF Research Database (Denmark)

    Zhang, Minwei; Halder, Arnab; Cao, Xianyi

    2017-01-01

    in electrochemical sensors and energy technologies amongothers. In this chapter, we present some examples to overview recent advances in theresearch and development of two-dimensional (2D) graphene papers as new materialsfor electrochemical sensors. The chapter covers the design, fabrication, functionalizationand...... functionalization ofgraphene papers with polymer and nanoscale functional building blocks for electrochemical-sensing purposes. In terms of electrochemical-sensing applications, the emphasis ison enzyme-graphene and nanoparticle-graphene paper-based systems for the detectionof glucose. We finally conclude...

  6. V2O5 xerogel-poly(ethylene oxide) hybrid material: Synthesis, characterization, and electrochemical properties

    International Nuclear Information System (INIS)

    Guerra, Elidia M.; Ciuffi, Katia J.; Oliveira, Herenilton P.

    2006-01-01

    In this work, we report the synthesis, characterization, and electrochemical properties of vanadium pentoxide xerogel-poly(ethylene oxide) (PEO) hybrid materials obtained by varying the average molecular weight of the organic component as well as the components' ratios. The materials were characterized by X-ray diffraction, ultraviolet/visible and infrared spectroscopies, thermogravimetric analysis, scanning electron microscopy, electron paramagnetic resonance, and cyclic voltammetry. Despite the presence of broad and low intensity peaks, the X-ray diffractograms indicate that the lamellar structure of the vanadium pentoxide xerogel is preserved, with increase in the interplanar spacing, giving evidence of a low-crystalline structure. We found that the electrochemical behaviour of the hybrid materials is quite similar to that found for the V 2 O 5 xerogel alone, and we verified that PEO leads to stabilization and reproducibility of the Li + electrochemical insertion/de-insertion into the V 2 O 5 xerogel structure, which makes these materials potential components of lithium ion batteries. - Graphical abstract: The synthesis, structural and electrochemical properties of vanadium pentoxide xerogel-poly(ethylene oxide) hybrid materials have been described. Despite the presence of broad and low intensity peaks, the X-ray diffractograms indicate that the lamellar structure of the vanadium pentoxide xerogel is preserved. The cyclic voltammetry technique demonstrated that PEO intercalation provides an improvement in the electrochemical properties, mainly with respect to the lithium electroinsertion process into the oxide matrix

  7. Elementary matrix algebra

    CERN Document Server

    Hohn, Franz E

    2012-01-01

    This complete and coherent exposition, complemented by numerous illustrative examples, offers readers a text that can teach by itself. Fully rigorous in its treatment, it offers a mathematically sound sequencing of topics. The work starts with the most basic laws of matrix algebra and progresses to the sweep-out process for obtaining the complete solution of any given system of linear equations - homogeneous or nonhomogeneous - and the role of matrix algebra in the presentation of useful geometric ideas, techniques, and terminology.Other subjects include the complete treatment of the structur

  8. Complex matrix model duality

    International Nuclear Information System (INIS)

    Brown, T.W.

    2010-11-01

    The same complex matrix model calculates both tachyon scattering for the c=1 non-critical string at the self-dual radius and certain correlation functions of half-BPS operators in N=4 super- Yang-Mills. It is dual to another complex matrix model where the couplings of the first model are encoded in the Kontsevich-like variables of the second. The duality between the theories is mirrored by the duality of their Feynman diagrams. Analogously to the Hermitian Kontsevich- Penner model, the correlation functions of the second model can be written as sums over discrete points in subspaces of the moduli space of punctured Riemann surfaces. (orig.)

  9. Complex matrix model duality

    Energy Technology Data Exchange (ETDEWEB)

    Brown, T.W.

    2010-11-15

    The same complex matrix model calculates both tachyon scattering for the c=1 non-critical string at the self-dual radius and certain correlation functions of half-BPS operators in N=4 super- Yang-Mills. It is dual to another complex matrix model where the couplings of the first model are encoded in the Kontsevich-like variables of the second. The duality between the theories is mirrored by the duality of their Feynman diagrams. Analogously to the Hermitian Kontsevich- Penner model, the correlation functions of the second model can be written as sums over discrete points in subspaces of the moduli space of punctured Riemann surfaces. (orig.)

  10. Study on the Efficient Disintegration of HTGR Fuel Elements by Electrochemical Method

    International Nuclear Information System (INIS)

    Piao Nan; Chen Ji; Xiao Cuiping; We Mingfen; Che Jing

    2014-01-01

    The spent fuel elements in High- temperature gas-cooled reactor (HTGR) have a special structure, so the head-end process of the spent fuel reprocessing is different from the process of water reactor spent fuel. The first step of head-end process of the HTGR spent fuel reprocessing process is disintegration of the graphite matrix and separation of the coated fuel particles. Electrochemical method with nitrate solution as an electrolyte for fuel element disintegration has been conducted by the Institute of Nuclear and New Energy Technology in Tsinghua University. This method allows a total disintegration of graphite matrix, while still preserving the integrity of TRISO particles. The influences of the pretreatment methods such as heating oxidation of graphite, hydrothermal and oxidants oxidation were investigated in the present work. The experimental results showed that there were no significant effects on increasing the disintegration rate when pretreatment methods were used ahead of electrochemical disintegration. This phenomenon indicated that the fuel elements which were calcined at 1073 K and pressed under 300 MPa are too compact to be broken by these pretreatment methods. And the electrochemical disintegration is an effective but slow method in breaking the graphite matrix. (author)

  11. Electrometallurgical treatment of aluminum-matrix fuels

    International Nuclear Information System (INIS)

    Willit, J.L.; Gay, E.C.; Miller, W.E.; McPheeters, C.C.; Laidler, J.J.

    1996-01-01

    The electrometallurgical treatment process described in this paper builds on our experience in treating spent fuel from the Experimental Breeder Reactor (EBR-II). The work is also to some degree, a spin-off from applying electrometallurgical treatment to spent fuel from the Hanford single pass reactors (SPRs) and fuel and flush salt from the Molten Salt Reactor Experiment (MSRE) in treating EBR-II fuel, we recover the actinides from a uranium-zirconium fuel by electrorefining the uranium out of the chopped fuel. With SPR fuel, uranium is electrorefined out of the aluminum cladding. Both of these processes are conducted in a LiCl-KCl molten-salt electrolyte. In the case of the MSRE, which used a fluoride salt-based fuel, uranium in this salt is recovered through a series of electrochemical reductions. Recovering high-purity uranium from an aluminum-matrix fuel is more challenging than treating SPR or EBR-II fuel because the aluminum- matrix fuel is typically -90% (volume basis) aluminum

  12. Symmetries of the 2D magnetic particle imaging system matrix

    International Nuclear Information System (INIS)

    Weber, A; Knopp, T

    2015-01-01

    In magnetic particle imaging (MPI), the relation between the particle distribution and the measurement signal can be described by a linear system of equations. For 1D imaging, it can be shown that the system matrix can be expressed as a product of a convolution matrix and a Chebyshev transformation matrix. For multidimensional imaging, the structure of the MPI system matrix is not yet fully explored as the sampling trajectory complicates the physical model. It has been experimentally found that the MPI system matrix rows have symmetries and look similar to the tensor products of Chebyshev polynomials. In this work we will mathematically prove that the 2D MPI system matrix has symmetries that can be used for matrix compression. (paper)

  13. Electrochemical depth profiling of multilayer metallic structures: An aluminum brazing sheet

    International Nuclear Information System (INIS)

    Afshar, F. Norouzi; Ambat, R.; Kwakernaak, C.; Wit, J.H.W. de; Mol, J.M.C.; Terryn, H.

    2012-01-01

    Highlights: ► Localized electrochemical cell and glow discharge optical emission spectrometry were used. ► An electrochemical depth profile of an aluminum brazing sheet was obtained. ► The electrochemical responses were correlated to the microstructural features. - Abstract: Combinatory localized electrochemical cell and glow discharge optical emission spectrometry (GDOES) measurements were performed to obtain a thorough in depth electrochemical characterization of an aluminum brazing sheet. By defining electrochemical criteria i.e. breakdown potential, corrosion potential, cathodic and anodic reactivities, and tracking their changes as a function of depth, the evolution of electrochemical responses through out the material thickness were analyzed and correlated to the corresponding microstructural features. Polarization curves in 1 wt% NaCl solution at pH 2.8 were obtained at different depths from the surface using controlled sputtering in a glow discharge optical emission spectrometer as a sample preparation technique. The anodic and cathodic reactivity of the top surface areas were significantly higher than that of the bulk, thus indicating these areas to be more susceptible to localized attack. Consistent with this, optical microscopy and scanning electron microscope analysis revealed a relatively high density of fine intermetallic and silicon particles at these areas. The corrosion mechanism of the top layers was identified to be intergranular and pitting corrosion, while lower sensitivity to these localized attacks were detected toward the brazing sheet core. The results highlight the successful application of the electrochemical depth profiling approach in prediction of the corrosion behavior of the aluminum brazing sheet and the importance of the electrochemical activity of the outer 10 μm in controlling the corrosion performance of the aluminum brazing sheet.

  14. Matrix digestion of soil and sediment samples for extraction of lead, cadmium and antimony and their direct determination by inductively coupled plasma-mass spectrometry and atomic emission spectrometry

    International Nuclear Information System (INIS)

    Chattopadhyay, P.; Fisher, A.S.; Henon, D.N.; Hill, S.J.

    2004-01-01

    An environmentally friendly and simple method has been developed for complete digestion of lead, cadmium and antimony from soil samples using a magnesium nitrate assisted dry ashing procedure. Statistical data for a series of experiments with standard reference materials are presented, and precision values are found to be comparable for inductively coupled plasma-mass spectrometry and for inductively coupled plasma-atomic emission spectrometry. From a single digest solution all analytes are quantified without involving any preconcentration routes. Inter-method comparison of inductively coupled plasma-mass spectrometry (ICP-MS) and inductively coupled plasma-atomic emission spectrometry (ICP-AES) shows that the probability of the results being different is less than 99 %. (author)

  15. Evaluation of the capabilities of atmospheric pressure chemical ionization source coupled to tandem mass spectrometry for the determination of dioxin-like polychlorobiphenyls in complex-matrix food samples.

    Science.gov (United States)

    Portolés, T; Sales, C; Abalos, M; Sauló, J; Abad, E

    2016-09-21

    The use of the novel atmospheric pressure chemical ionization (APCI) source for gas chromatography (GC) coupled to triple quadrupole using tandem mass spectrometry (MS/MS) and its potential for the simultaneous determination of the 12 dioxin-like polychlorobiphenyls (DL-PCBs) in complex food and feed matrices has been evaluated. In first place, ionization and fragmentation behavior of DL-PCBs on the APCI source under charge transfer conditions has been studied followed by their fragmentation in the collision cell. Linearity, repeatability and sensitivity have been studied obtaining instrumental limits of detection and quantification of 0.0025 and 0.005 pg μL(-1) (2.5 and 5 fg on column) respectively for every DL-PCB. Finally, application to real samples has been carried out and DL-PCB congeners (PCB 77, 81, 105, 114, 118, 123, 126, 156, 157, 167, 169, 189) have been detected in the different samples in the range of 0.40-10000 pg g(-1). GC-(APCI)MS/MS has been proved as a suitable alternative to the traditionally accepted confirmation method based on the use of high resolution mass spectrometry and other triple quadrupole tandem mass spectrometry techniques operating with electron ionization. The development of MS/MS methodologies for the analysis of dioxins and DL-PCBs is nowadays particularly important, since this technique was included as a confirmatory method in the present European Union regulations that establish the requirements for the determination of these compounds in food and feed matrices. Copyright © 2016 Elsevier B.V. All rights reserved.

  16. Electrochemical depth profiling of multilayer metallic structures: An aluminum brazing sheet

    DEFF Research Database (Denmark)

    Afshar, F. Norouzi; Ambat, R.; Kwakernaak, C.

    2012-01-01

    Combinatory localized electrochemical cell and glow discharge optical emission spectrometry (GDOES) measurements were performed to obtain a thorough in depth electrochemical characterization of an aluminum brazing sheet. By defining electrochemical criteria i.e. breakdown potential, corrosion...... potential, cathodic and anodic reactivities, and tracking their changes as a function of depth, the evolution of electrochemical responses through out the material thickness were analyzed and correlated to the corresponding microstructural features. Polarization curves in 1wt% NaCl solution at pH 2.8 were...... obtained at different depths from the surface using controlled sputtering in a glow discharge optical emission spectrometer as a sample preparation technique. The anodic and cathodic reactivity of the top surface areas were significantly higher than that of the bulk, thus indicating these areas to be more...

  17. Electrochemical modeling of hydrogen storage in hydride-forming electrodes

    NARCIS (Netherlands)

    Ledovskikh, A.; Danilov, D.; Vermeulen, P.; Notten, P.H.L.

    2009-01-01

    An electrochemical kinetic model (EKM) is developed, describing the electrochemical hydrogen storage in hydride-forming materials under equilibrium conditions. This model is based on first principles of electrochemical reaction kinetics and statistical thermodynamics and describes the complex,

  18. Mediated electrochemical hazardous waste destruction

    International Nuclear Information System (INIS)

    Hickman, R.G.; Farmer, J.C.; Wang, F.T.

    1992-03-01

    There are few permitted processes for mixed waste (radioactive plus chemically hazardous) treatment. We are developing an electrochemical process, based upon mediated electrochemical oxidation (MEO), that converts toxic organic components of mixed waste to water, carbon dioxide, and chloride or chloride precipitates. Aggressive oxidizer ions such as Ag 2+ , Co 3+ , or Fe 3+ are produced at an anode. These can attack organic molecules directly, and may also produce hydroxyl free radicals that promote destruction. Solid and liquid radioactive waste streams containing only inorganic radionuclide forms may be treated with existing technology and prepared for final disposal. The coulombic efficiency of the process has been determined, as well as the destruction efficiency for ethylene glycol, a surrogate waste. In addition, hazardous organic materials are becoming very expensive to dispose of and when they are combined with transuranic radioactive elements no processes are presently permitted. Mediated electrochemical oxidation is an ambient- temperature aqueous-phase process that can be used to oxidize organic components of mixed wastes. Problems associated with incineration, such as high-temperature volatilization of radionuclides, are avoided. Historically, Ag(II) has been used as a mediator in this process. Fe(III) and Co(III) are attractive alternatives to Ag(II) since they form soluble chlorides during the destruction of chlorinated solvents. Furthermore, silver itself is toxic heavy metal. Quantitative data have been obtained for the complete oxidation of ethylene glycol by Fe(III) and Co(III). Though ethylene glycol is a nonhalogenated organic, these data have enabled us to make direct comparisons of activities of Fe(III) and Co(III) with Ag(II). Very good quantitative data for the oxidation of ethylene glycol by Ag(II) had already been collected

  19. Electrochemical properties of quaternary ammonium salts for electrochemical capacitors

    Energy Technology Data Exchange (ETDEWEB)

    Ue, Makoto; Takeda, Masayuki; Takehara, Masahiro; Mori, Shoichiro [Mitsubishi Chemical Corp., Inashiki, Ibaraki (Japan). Tsukuba Research Center

    1997-08-01

    The limiting reduction and oxidation potentials and electrolytic conductivities of new quaternary ammonium salts were examined for electrochemical capacitor applications, whose anions have already been tested as lithium salts for lithium battery applications. The anodic stability was in the following order BR{sub 4}{sup {minus}} < ClO{sub 4}{sup {minus}} {le} CF{sub 3}SO{sub 3}{sup {minus}} < (CF{sub 3}SO{sub 2}){sub 2}N{sup {minus}} {le} C{sub 4}F{sub 9}SO{sub 3}{sup {minus}} < BF{sub 4}{sup {minus}} < PF{sub 6}{sup {minus}} {le} AsF{sub 6}{sup {minus}} < SbF{sub 6}{sup {minus}}. The electrolytic conductivities of Me{sub 4{minus}n}Et{sub n}N(CF{sub 3}SO{sub 2}){sub 2}N (n = 0--4) were examined in comparison with Me{sub 4{minus}n}Et{sub n}NBF{sub 4} counterparts. These imide salts showed good solubility, relatively high conductivity, and anodic stability in propylene carbonate. Et{sub 4}N(CF{sub 3}SO{sub 2}){sub 2}N was found to be a good supporting salt for low permittivity organic solvents, and it afforded a highly conductive electrolyte system based on the ethylene carbonate-dimethyl carbonate mixed solvent, which is useful for electrochemical capacitor applications.

  20. Electrochemical behaviour of polyphenol rich fruit juices using disposable screen-printed carbon electrodes: towards a rapid sensor for antioxidant capacity and individual antioxidants.

    Science.gov (United States)

    Bordonaba, Jordi Giné; Terry, Leon A

    2012-02-15

    The analysis of antioxidants in different foodstuffs and especially fruits has become an active area of research which has lead to numerous antioxidant-assays being recently developed. Many antioxidants exhibit inherent electroactivity, and hence employing electrochemical methods could be a viable approach for evaluating the overall antioxidant capacity of a fresh produce matrix without the need for added reactive species. This work shows the possibility of using square wave voltammetry (SWV) and other electrochemical methods with disposable screen-printed carbon electrodes, to quantify and assess antioxidant activity and abundance of specific antioxidants, mainly polyphenols in selected soft fruit juices. Freshly squeezed black currant and strawberry juices of different cultivars and maturity stages were chosen according to known differences in their antioxidant profile. As a result of the increasing applied potential (0-1000 mV vs. Ag/AgCl) the electroactive compounds present in the juices were oxidised leading to a characteristic voltammetric profile for each of the samples analysed. Generally, black currant juices had greater oxidation peaks at lower potentials (<400 mV) which were indicators of higher antioxidant capacities. The relationship between sensor cumulative responses at different applied potentials and total or individual antioxidants, as determined by conventional spectrophotometric methods (FRAP, Folin-Ciocalteu) and HPLC (individual anthocyanins and ascorbate), respectively, are discussed in the context of the development of a rapid sensor for antioxidants. Copyright © 2011 Elsevier B.V. All rights reserved.

  1. Ethical Matrix Manual

    NARCIS (Netherlands)

    Mepham, B.; Kaiser, M.; Thorstensen, E.; Tomkins, S.; Millar, K.

    2006-01-01

    The ethical matrix is a conceptual tool designed to help decision-makers (as individuals or working in groups) reach sound judgements or decisions about the ethical acceptability and/or optimal regulatory controls for existing or prospective technologies in the field of food and agriculture.

  2. Combinatorial matrix theory

    CERN Document Server

    Mitjana, Margarida

    2018-01-01

    This book contains the notes of the lectures delivered at an Advanced Course on Combinatorial Matrix Theory held at Centre de Recerca Matemàtica (CRM) in Barcelona. These notes correspond to five series of lectures. The first series is dedicated to the study of several matrix classes defined combinatorially, and was delivered by Richard A. Brualdi. The second one, given by Pauline van den Driessche, is concerned with the study of spectral properties of matrices with a given sign pattern. Dragan Stevanović delivered the third one, devoted to describing the spectral radius of a graph as a tool to provide bounds of parameters related with properties of a graph. The fourth lecture was delivered by Stephen Kirkland and is dedicated to the applications of the Group Inverse of the Laplacian matrix. The last one, given by Ángeles Carmona, focuses on boundary value problems on finite networks with special in-depth on the M-matrix inverse problem.

  3. Visualizing Matrix Multiplication

    Science.gov (United States)

    Daugulis, Peteris; Sondore, Anita

    2018-01-01

    Efficient visualizations of computational algorithms are important tools for students, educators, and researchers. In this article, we point out an innovative visualization technique for matrix multiplication. This method differs from the standard, formal approach by using block matrices to make computations more visual. We find this method a…

  4. Challenging the CSCW matrix

    DEFF Research Database (Denmark)

    Jørnø, Rasmus Leth Vergmann; Gynther, Karsten; Christensen, Ove

    2014-01-01

    useful information, we question whether the axis of time and space comprising the matrix pertains to relevant defining properties of the tools, technology or learning environments to which they are applied. Subsequently we offer an example of an Adobe Connect e-learning session as an illustration...

  5. Nanoporous carbon for electrochemical capacitors.

    Energy Technology Data Exchange (ETDEWEB)

    Siegal, Michael P.; Bunker, Bruce Conrad; Limmer, Steven J.; Yelton, William Graham

    2010-05-01

    Nanoporous carbon (NPC) is a purely graphitic material with highly controlled densities ranging from less than 0.1 to 2.0 g/cm3, grown via pulsed-laser deposition. Decreasing the density of NPC increases the interplanar spacing between graphene-sheet fragments. This ability to tune the interplanar spacing makes NPC an ideal model system to study the behavior of carbon electrodes in electrochemical capacitors and batteries. We examine the capacitance of NPC films in alkaline and acidic electrolytes, and measure specific capacitances as high as 242 F/g.

  6. Nanoelectrode array for electrochemical analysis

    Energy Technology Data Exchange (ETDEWEB)

    Yelton, William G [Sandia Park, NM; Siegal, Michael P [Albuquerque, NM

    2009-12-01

    A nanoelectrode array comprises a plurality of nanoelectrodes wherein the geometric dimensions of the electrode controls the electrochemical response, and the current density is independent of time. By combining a massive array of nanoelectrodes in parallel, the current signal can be amplified while still retaining the beneficial geometric advantages of nanoelectrodes. Such nanoelectrode arrays can be used in a sensor system for rapid, non-contaminating field analysis. For example, an array of suitably functionalized nanoelectrodes can be incorporated into a small, integrated sensor system that can identify many species rapidly and simultaneously under field conditions in high-resistivity water, without the need for chemical addition to increase conductivity.

  7. Nanoporous carbon for electrochemical capacitors.

    Energy Technology Data Exchange (ETDEWEB)

    Overmyer, Donald L.; Siegal, Michael P.; Bunker, Bruce Conrad; Limmer, Steven J.; Yelton, William Graham

    2010-04-01

    Nanoporous carbon (NPC) is a purely graphitic material with highly controlled densities ranging from less than 0.1 to 2.0 g/cm3, grown via pulsed-laser deposition. Decreasing the density of NPC increases the interplanar spacing between graphene-sheet fragments. This ability to tune the interplanar spacing makes NPC an ideal model system to study the behavior of carbon electrodes in electrochemical capacitors and batteries. We examine the capacitance of NPC films in alkaline and acidic electrolytes, and measure specific capacitances as high as 242 F/g.

  8. Electrochemical characterization of liquid resistors

    International Nuclear Information System (INIS)

    Wilson, J.M.; Whiteley, R.V.

    1983-01-01

    During the first two years of operation of Sandia's Particle Beam Fusion Accelerator (PBFA I) the reliability of the CuSO 4 solution resistors in the Marx Generator Energy Storage System has been unsatisfactory. Resistor failure, which is characterized by a large increase in resistance, has been attributed to materials, production techniques, and operating parameters. The problems associated with materials and production techniques have been identified and solutions are proposed. Non-ideal operating parameters are shown to cause polarization of the cathode in the resistor. This initiates electrochemical reactions in the resistor. These reactions often lead to resistance changes and to eventual resistor failure

  9. Lead-nickel electrochemical batteries

    CERN Document Server

    Glaize, Christian

    2012-01-01

    The lead-acid accumulator was introduced in the middle of the 19th Century, the diverse variants of nickel accumulators between the beginning and the end of the 20th Century. Although old, these technologies are always very present on numerous markets. Unfortunately they are still not used in optimal conditions, often because of the misunderstanding of the internal electrochemical phenomena.This book will show that batteries are complex systems, made commercially available thanks to considerable amounts of scientific research, empiricism and practical knowledge. However, the design of

  10. Electrochemical behavior of titanium implanted with platinum

    International Nuclear Information System (INIS)

    Thompson, N.G.; Lichter, B.D.; Appleton, B.R.; Kelly, E.J.; White, C.W.

    1979-01-01

    The following conclusions apply to Ti(Pt) near-surface alloys studied. (1) Open-circuit corrosion measurements show that accumulation of platinum may occur at a surface concentration of 0.32 atomic percent Pt while no accumulation occurs at 0.16 atomic percent Pt. However, these results do not allow a distinction as to cause of accumulation to be made between concentration effects and effects due to the presence of an oxide film. (2) Potentiostatic corrosion at -0.450 V (active corrosion) establish that little or no accumulation of platinum occurs at an oxide-free surface for concentrations less than 0.086 atomic percent Pt; whereas, a large amount of accumulation occurs for a distribution with a peak concentration of 0.83 atomic percent Pt. (3) An initial distribution having a peak concentration of 0.32 atomic percent platinum is sufficient to induce natural passivity in titanium and bring a freely corroding sample to a potential of 0.269 V. This is nearly the applicable reversible potential (-0.260 V) for the hydrogen reaction in 1N H 2 SO 4 . (4) Of three samples which showed accumulation, platinum was eventually lost for two of these samples (0.32 atomic percent, open-circuit corrosion; 0.83 atomic percent, potentiostatic corrosion). The remaining sample (9.1 atomic percent, open-circuit corrosion) maintained the maximum possible potential of -0.260 V for the length of the experiment (approx. 30 days). (5) For samples which had been polarized at -0.300 to -0.340 V and which had eventually reverted to the behavior of pure Ti, post corrosion RBS measurements reveal that a substantial fraction of the Pt fluence is retained on the surface in an electrochemically inactive state

  11. 3,5-Diamino-1,2,4-triazole@electrochemically reduced graphene oxide film modified electrode for the electrochemical determination of 4-nitrophenol

    International Nuclear Information System (INIS)

    Kumar, Deivasigamani Ranjith; Kesavan, Srinivasan; Baynosa, Marjorie Lara; Shim, Jae-Jin

    2017-01-01

    Highlights: •Triazole film was formed on electrochemically reduced graphene oxide. •pDAT@ERGO/GC was utilized for the electrochemical determination of 4-nitrophenol. •pDAT@ERGO/GC electrode offered wide concentration and nanomolar detection limit. •The fabricated electrode was employed in water sample analyses. -- Abstract: In this study, an eco-friendly benign method for the modification of electrochemically reduced graphene oxide (ERGO) on glassy carbon (GC) surface and electrochemical polymerized 3,5-diamino-1,2,4-triazole (DAT) film composite (pDAT@ERGO/GC) electrode was developed. The surface morphologies of the pDAT@ERGO/GC modified electrode were analyzed by field emission scanning electron microscopy (FESEM). FESEM images indicated that the ERGO supported pDAT has an almost homogeneous morphology structure with a size of 70 to 80 nm. It is due to the water oxidation reaction occurred while pDAT@ERGO/GC fabrication peak at +1.4 V leads to O 2 evolution and oxygen functional group functionalization on ERGO, which confirmed by X-ray photoelectron spectroscopy (XPS). In contrast, the bare GC modified with pDAT showed randomly arranged irregular bulky morphology structure compared to those of pDAT@ERGO/GC. Electrochemical reduction of graphene oxide was confirmed by Raman spectroscopy, XPS, and electrochemical impedance spectroscopy (EIS). The pDAT@ERGO/GC modified electrode was used for the electrochemical determination of 4-nitrophenol (4-NP). The 4-NP oxidation peak was observed at +0.25 V, and the differential pulse voltammetry demonstrated wide concentration range (5–1500 μM), high sensitivity (0.7113 μA μM −1 ), and low limit of detection (37 nM). Moreover, the pDAT@ERGO/GC electrode was applied to real water sample analysis by standard addition method, where in good recoveries (97.8% to 102.4%) were obtained.

  12. Evaluation of the capabilities of atmospheric pressure chemical ionization source coupled to tandem mass spectrometry for the determination of dioxin-like polychlorobiphenyls in complex-matrix food samples

    International Nuclear Information System (INIS)

    Portolés, T.; Sales, C.; Abalos, M.; Sauló, J.; Abad, E.

    2016-01-01

    The use of the novel atmospheric pressure chemical ionization (APCI) source for gas chromatography (GC) coupled to triple quadrupole using tandem mass spectrometry (MS/MS) and its potential for the simultaneous determination of the 12 dioxin-like polychlorobiphenyls (DL-PCBs) in complex food and feed matrices has been evaluated. In first place, ionization and fragmentation behavior of DL-PCBs on the APCI source under charge transfer conditions has been studied followed by their fragmentation in the collision cell. Linearity, repeatability and sensitivity have been studied obtaining instrumental limits of detection and quantification of 0.0025 and 0.005 pg μL"−"1 (2.5 and 5 fg on column) respectively for every DL-PCB. Finally, application to real samples has been carried out and DL-PCB congeners (PCB 77, 81, 105, 114, 118, 123, 126, 156, 157, 167, 169, 189) have been detected in the different samples in the range of 0.40–10000 pg g"−"1. GC-(APCI)MS/MS has been proved as a suitable alternative to the traditionally accepted confirmation method based on the use of high resolution mass spectrometry and other triple quadrupole tandem mass spectrometry techniques operating with electron ionization. The development of MS/MS methodologies for the analysis of dioxins and DL-PCBs is nowadays particularly important, since this technique was included as a confirmatory method in the present European Union regulations that establish the requirements for the determination of these compounds in food and feed matrices. - Highlights: • GC-(APCI)MS/MS with QqQ: a suitable alternative to GC-(EI)HRMS for DL-PCBs determination. • LODs and LOQs as low as 0.0025 and 0.005 pg μL"−"1 respectively achieved for each DL-PCB congener. • Enhanced sensitivity and specificity of APCI in comparison with EI source in QqQ instruments.

  13. Evaluation of the capabilities of atmospheric pressure chemical ionization source coupled to tandem mass spectrometry for the determination of dioxin-like polychlorobiphenyls in complex-matrix food samples

    Energy Technology Data Exchange (ETDEWEB)

    Portolés, T., E-mail: tportole@uji.es [Research Institute for Pesticides and Water, University Jaume I, Avda. Sos Baynat, E-12071 Castellón (Spain); Sales, C. [Research Institute for Pesticides and Water, University Jaume I, Avda. Sos Baynat, E-12071 Castellón (Spain); Abalos, M.; Sauló, J.; Abad, E. [Laboratory of Dioxins, IDAEA, CSIC, Jordi Girona 18-26, E-08034 Barcelona (Spain)

    2016-09-21

    The use of the novel atmospheric pressure chemical ionization (APCI) source for gas chromatography (GC) coupled to triple quadrupole using tandem mass spectrometry (MS/MS) and its potential for the simultaneous determination of the 12 dioxin-like polychlorobiphenyls (DL-PCBs) in complex food and feed matrices has been evaluated. In first place, ionization and fragmentation behavior of DL-PCBs on the APCI source under charge transfer conditions has been studied followed by their fragmentation in the collision cell. Linearity, repeatability and sensitivity have been studied obtaining instrumental limits of detection and quantification of 0.0025 and 0.005 pg μL{sup −1} (2.5 and 5 fg on column) respectively for every DL-PCB. Finally, application to real samples has been carried out and DL-PCB congeners (PCB 77, 81, 105, 114, 118, 123, 126, 156, 157, 167, 169, 189) have been detected in the different samples in the range of 0.40–10000 pg g{sup −1}. GC-(APCI)MS/MS has been proved as a suitable alternative to the traditionally accepted confirmation method based on the use of high resolution mass spectrometry and other triple quadrupole tandem mass spectrometry techniques operating with electron ionization. The development of MS/MS methodologies for the analysis of dioxins and DL-PCBs is nowadays particularly important, since this technique was included as a confirmatory method in the present European Union regulations that establish the requirements for the determination of these compounds in food and feed matrices. - Highlights: • GC-(APCI)MS/MS with QqQ: a suitable alternative to GC-(EI)HRMS for DL-PCBs determination. • LODs and LOQs as low as 0.0025 and 0.005 pg μL{sup −1} respectively achieved for each DL-PCB congener. • Enhanced sensitivity and specificity of APCI in comparison with EI source in QqQ instruments.

  14. Whitby Mudstone, flow from matrix to fractures

    Science.gov (United States)

    Houben, Maartje; Hardebol, Nico; Barnhoorn, Auke; Boersma, Quinten; Peach, Colin; Bertotti, Giovanni; Drury, Martyn

    2016-04-01

    Fluid flow from matrix to well in shales would be faster if we account for the duality of the permeable medium considering a high permeable fracture network together with a tight matrix. To investigate how long and how far a gas molecule would have to travel through the matrix until it reaches an open connected fracture we investigated the permeability of the Whitby Mudstone (UK) matrix in combination with mapping the fracture network present in the current outcrops of the Whitby Mudstone at the Yorkshire coast. Matrix permeability was measured perpendicular to the bedding using a pressure step decay method on core samples and permeability values are in the microdarcy range. The natural fracture network present in the pavement shows a connected network with dominant NS and EW strikes, where the NS fractures are the main fracture set with an orthogonal fracture set EW. Fracture spacing relations in the pavements show that the average distance to the nearest fracture varies between 7 cm (EW) and 14 cm (NS), where 90% of the matrix is 30 cm away from the nearest fracture. By making some assumptions like; fracture network at depth is similar to what is exposed in the current pavements and open to flow, fracture network is at hydrostatic pressure at 3 km depth, overpressure between matrix and fractures is 10% and a matrix permeability perpendicular to the bedding of 0.1 microdarcy, we have calculated the time it takes for a gas molecule to travel to the nearest fracture. These input values give travel times up to 8 days for a distance of 14 cm. If the permeability is changed to 1 nanodarcy or 10 microdarcy travel times change to 2.2 years or 2 hours respectively.

  15. Molecularly imprinted electrochemical sensor based on nickel nanoparticle-modified electrodes for phenobarbital determination

    International Nuclear Information System (INIS)

    Yu, Hui Cheng; Huang, Xue Yi; Lei, Fu Hou; Tan, Xue Cai; Wei, Yi Chun; Li, Hao

    2014-01-01

    Highlights: • Uniform Ni nanoparticles were synthesized. • A Ni nanoparticle-modified imprinted sensor was developed to detect phenobarbital. • The modified sensor exhibited high sensitivity for phenobarbital. • The electrochemical properties of the modified sensor were investigated. • The prepared sensor was applied to detect phenobarbital in fish samples. - Abstract: Uniform nickel nanoparticles were applied to improve the sensitivity of sensors for phenobarbital (PB) determination. A Ni nanoparticle-modified imprinted electrochemical sensor was developed by thermal polymerization with the use of methacrylic acid as the functional monomer and ethylene glycol maleic rosinate acrylate as the crosslinking agent. The chemical structures and morphologies of the imprinted films were characterized using Fourier transform infrared spectroscopy and scanning electron microscopy. The success of the fabrication of Ni nanoparticles, as well as the Ni nanoparticle-modified imprinted electrochemical sensor, was confirmed by the analytical results. The electrochemical properties of the modified molecularly imprinted and non-imprinted polymer sensors were investigated by cyclic voltammetry, differential pulse voltammetry, electrochemical impedance spectroscopy, and chronoamperometry. Results showed that the electrochemical properties of the molecularly imprinted sensor were remarkably different from those of the non-imprinted sensor. Linear responses of the imprinted sensor to PB were observed for concentrations ranging from 1.4 × 10 −7 mol L −1 to 1.3 × 10 −4 mol L −1 (r 2 = 0.9976), with a detection limit of 8.2 × 10 −9 mol L −1 (S/N = 3). The imprinted electrochemical sensor was used to determine PB in actual fish samples, in which average recoveries between 95.60% and 104.67% were achieved. The developed Ni nanoparticle-modified electrochemical sensor exhibited high sensitivity, high selectivity, and good recovery

  16. Comparative DEMS study on the electrochemical oxidation of carbon blacks

    DEFF Research Database (Denmark)

    Ashton, Sean James; Arenz, Matthias

    2012-01-01

    Publication year: 2012 Source:Journal of Power Sources, Volume 217 Sean J. Ashton, Matthias Arenz The intention of the study presented here is to compare the electrochemical oxidation tendencies of a pristine Ketjen Black EC300 high surface area (HSA) carbon black, and four graphitised counterparts...... heat-treated between 2100 and 3200 °C, such as those typically used as corrosion resistant carbon (CRC) supports for polymer electrolyte membrane fuel cell (PEMFC) catalysts. A methodology combining cyclic voltammetry (CV) and differential electrochemical mass spectrometry (DEMS) is used, which allows......; however, CRC samples graphitised =2800 °C did not exhibit this same behaviour. Highlights ¿ We quantitatively determine electrooxidation of carbon support materials. ¿ We can distinguish between the total and partial electrooxidation. ¿ Non or mildly heat treated carbon forms passivating layer. ¿ Heat...

  17. Electrochemical Multi-Coloration of Molybdenum Oxide Bronzes

    International Nuclear Information System (INIS)

    Lee, Sangmin; Saji, Viswanathan S.; Lee, Chiwoo

    2013-01-01

    We report a simple electrochemical approach in fabricating multiple colored molybdenum (Mo) oxide bronzes on the surface of a Mo-quartz electrode. A three step electrochemical batch process consisting of linear sweep voltammetry and anodic oxidation followed by cathodic reduction in neutral K 2 SO 4 electrolyte at different end potentials, viz. -0.62, -0.80 and -1.60 V (vs. Hg/HgSO 4 ) yielded red, blue and yellow colored bronzes. The samples produced were analyzed by XRD, EDS, and SIMS. The color variation was suggested to be associated with the cations intercalation into the oxide formed and the simultaneous structural changes that occurred during the cathodic reduction in neutral aqueous medium

  18. Electrochemical Multi-Coloration of Molybdenum Oxide Bronzes

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sangmin; Saji, Viswanathan S.; Lee, Chiwoo [Korea Univ., Seoul (Korea, Republic of)

    2013-08-15

    We report a simple electrochemical approach in fabricating multiple colored molybdenum (Mo) oxide bronzes on the surface of a Mo-quartz electrode. A three step electrochemical batch process consisting of linear sweep voltammetry and anodic oxidation followed by cathodic reduction in neutral K{sub 2}SO{sub 4} electrolyte at different end potentials, viz. -0.62, -0.80 and -1.60 V (vs. Hg/HgSO{sub 4}) yielded red, blue and yellow colored bronzes. The samples produced were analyzed by XRD, EDS, and SIMS. The color variation was suggested to be associated with the cations intercalation into the oxide formed and the simultaneous structural changes that occurred during the cathodic reduction in neutral aqueous medium.

  19. The low temperature electrochemical performances of LiFePO4/C/graphene nanofiber with 3D-bridge network structure

    International Nuclear Information System (INIS)

    Xie, Dong; Cai, Guanglan; Liu, Zhichao; Guo, Ruisong; Sun, Dandan; Zhang, Chao; Wan, Yizao; Peng, Jianhong; Jiang, Hong

    2016-01-01

    Highlights: • Highly conductive graphene nanofibers were introduced into the LiFePO 4 /C matrix. • Graphene nanofiber modification improved the discharge capacity at low temperatures. • Graphene nanofiber reduced the polarization of the electrodes at low temperatures. • Modified electrodes exhibited decreased charge-transfer resistance. • Graphene nanofiber modified samples exhibited higher diffusion coefficient of lithium ions. - Abstract: Three-dimensionally assembled LiFePO 4 /C/graphene nanofiber composites were successfully prepared via a suspension mixing method followed by heat-treatment at 400 °C. A faster electron transfer, lower electrochemical polarization as well as higher diffusion coefficient of Li + are obtained with the assistance of graphene nanofibers. The 5 wt% graphene nanofibers modified electrode (G-5) delivers the best electrochemical kinetics including the lowest charge transfer resistance and highest diffusion coefficient of Li + at 0 °C and −20 °C, respectively. Likewise, the G-5 exhibits the highest charge-discharge capability and the most stable cycling performance at low operation temperatures compared with those of LiFePO 4 /C, 3 wt% and 7 wt% graphene nanofibers modified LiFePO 4 /C (G-3 and G-7) composites. The G-5 electrode shows a capacity of 92.8 mAh g −1 with 92.0% capacity retention after 200 cycles at 1C at −20 °C. The reasons for the significant improvement of the low operation temperatures electrochemical performances can be ascribed to the enhanced conductivity and reduced agglomeration of pristine particles due to the introduction of graphene nanofibers. These excellent low temperature performances show that graphene nanofibers modified LiFePO 4 /C electrodes are promising cathode candidates for lithium-ion batteries applications at low temperatures.

  20. Optical, Nanomechanical and Electrochemical Sensing on a DVD Disc

    DEFF Research Database (Denmark)

    Boisen, Anja

    2014-01-01

    platform in order to study and count larger objects such as cells. In this way it will be possible to analyze a given sample for several parameters simultaneously. Electrodes can also be integrated on the spinning platform [4] and hereby it is possible to perform electrochemical measurements at the same...... combined with sensitive and compact read-out possibilities from optical pick-up heads makes it possible to realize full sample pretreatment and read-out in a both fast and compact manner. References: 1. M. Madou et al., Lab on a CD, Annual Review of Biomedical Engineering, Vol. 8: 601-628, 2016 2. F...

  1. Electrochemical properties of polyaniline-modified sodium vanadate nanomaterials

    International Nuclear Information System (INIS)

    Reddy Channu, V.S.; Holze, Rudolf; Yeo, In-Hyeong; Mho, Sun-il; Kalluru, Rajamohan R.

    2011-01-01

    Sodium vanadate nanomaterials were synthesized at different pH-values of a sodium hydroxide solution of vanadium pentoxide. Polyaniline-modified sodium vanadate nanomaterials were prepared at room temperature and at 3 C by a chemical polymerization method. The crystal structure and phase purity of the samples have been examined by powder XRD. The samples were identified as HNaV 6 O 16 .4H 2 O and Na 1.1 V 3 O 7.9 . The electrochemical measurements show that polyaniline-modified sodium vanadate hydrated nanomaterials provide higher current density than the sodium vanadate nanomaterials. (orig.)

  2. Morphology of the porous silicon obtained by electrochemical anodization method

    Science.gov (United States)

    Bertel H, S. D.; Dussán C, A.; Diaz P, J. M.

    2018-04-01

    In this report, the dependence of porous silicon with the synthesis parameters and their correlation with the optical and morphological properties is studied. The P-type silicon-crystalline samples and orientation were prepared by electrochemical anodization and were characterized using SEM in order to know the evolution of the pore morphology. It was observed that the porosity and thickness of the samples increased with the increase of the concentration in the solution and a high pore density (70%) with a pore size between 40nm and 1.5μm.

  3. Electrochemical Promotion of Catalytic Reactions Using

    DEFF Research Database (Denmark)

    Petrushina, Irina; Bjerrum, Niels; Cleemann, Lars Nilausen

    2007-01-01

    This paper presents the results of a study on electrochemical promotion (EP) of catalytic reactions using Pt/C/polybenzimidazole(H3PO4)/Pt/C fuel cell performed by the Energy and Materials Science Group (Technical University of Denmark) during the last 6 years[1-4]. The development of our...... understanding of the nature of the electrochemical promotion is also presented....

  4. Three dimensional electrochemical system for neurobiological studies

    DEFF Research Database (Denmark)

    Vazquez, Patricia; Dimaki, Maria; Svendsen, Winnie Edith

    2009-01-01

    In this work we report a novel three dimensional electrode array for electrochemical measurements in neuronal studies. The main advantage of working with these out-of-plane structures is the enhanced sensitivity of the system in terms of measuring electrochemical changes in the environment...

  5. The Strategic Electrochemical Research Center in Denmark

    DEFF Research Database (Denmark)

    Mogensen, Mogens Bjerg; Hansen, Karin Vels

    2011-01-01

    A 6-year strategic electrochemistry research center (SERC) in fundamental and applied aspects of electrochemical cells with a main emphasis on solid oxide cells was started in Denmark on January 1st, 2007 in cooperation with other Danish and Swedish Universities. Furthermore, 8 Danish companies...... are presented. ©2011 COPYRIGHT ECS - The Electrochemical Society...

  6. Electrochemical Reduction Process for Pyroprocessing

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Eun-Young; Hong, Sun-Seok; Park, Wooshin; Im, Hun Suk; Oh, Seung-Chul; Won, Chan Yeon; Cha, Ju-Sun; Hur, Jin-Mok [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2014-06-15

    Nuclear energy is expected to meet the growing energy demand while avoiding CO{sub 2} emission. However, the problem of accumulating spent fuel from current nuclear power plants which is mainly composed of uranium oxides should be addressed. One of the most practical solutions is to reduce the spent oxide fuel and recycle it. Next-generation fuel cycles demand innovative features such as a reduction of the environmental load, improved safety, efficient recycling of resources, and feasible economics. Pyroprocessing based on molten salt electrolysis is one of the key technologies for reducing the amount of spent nuclear fuel and destroying toxic waste products, such as the long-life fission products. The oxide reduction process based on the electrochemical reduction in a LiCl-Li{sub 2}O electrolyte has been developed for the volume reduction of PWR (Pressurized Water Reactor) spent fuels and for providing metal feeds for the electrorefining process. To speed up the electrochemical reduction process, the influences of the feed form for the cathode and the type of anode shroud on the reduction rate were investigated.

  7. Electrochemical treatment of liquid wastes

    Energy Technology Data Exchange (ETDEWEB)

    Hobbs, D.T. [Savannah River Technology Center, Aiken, SC (United States)

    1997-10-01

    Under this task, electrochemical treatment processes are being evaluated and developed for the destruction of organic compounds and nitrates/nitrites and the removal of other hazardous species from liquid wastes stored throughout the DOE complex. This technology targets the (1) destruction of nitrates, nitrites and organic compounds; (2) removal of radionuclides; and (3) removal of RCRA metals. The development program consists of five major tasks: (1) evaluation of electrochemical reactors for the destruction and removal of hazardous waste components, (2) development and validation of engineering process models, (3) radioactive laboratory-scale tests, (4) demonstration of the technology in an engineering-scale reactor, and (5) analysis and evaluation of test data. The development program team is comprised of individuals from national laboratories, academic institutions, and private industry. Possible benefits of this technology include: (1) improved radionuclide separation as a result of the removal of organic complexants, (2) reduction in the concentrations of hazardous and radioactive species in the waste (e.g., removal of nitrate, mercury, chromium, cadmium, {sup 99}Tc, and {sup 106}Ru), (3) reduction in the size of the off-gas handling equipment for the vitrification of low-level waste (LLW) by reducing the source of NO{sub x} emissions, (4) recovery of chemicals of value (e.g. sodium hydroxide), and (5) reduction in the volume of waste requiring disposal.

  8. Electrochemical Reduction of Zinc Phosphate

    International Nuclear Information System (INIS)

    Kim, Chang Hwan; Lee, Jung Hyun; Shin, Woon Sup

    2010-01-01

    We demonstrated first that the electrochemical reduction of zinc phosphate in neutral phosphate buffer is possible and potentially applicable to bio-compatible rechargeable battery. The actual redox component is Zn(s)/Zn phosphate(s) and the future research about the control of crystal formation for the better cyclability is required. In lead-acid battery, the electrochemical redox reaction of Pb (s) /PbSO 4(s) is used by reducing Pb(II) and oxidizing Pb(0) in sulfate rich solution. Since both reduced form and oxidized form are insoluble, they cannot diffuse to the opposite electrodes and react. It is a very common strategy to make a stable battery electrode that a metal element is reduced and oxidized in solution containing an abundance of anion readily precipitating with the metal ion. For the application of this strategy to construction of rechargeable battery using bio-compatible electrode materials and electrolytes, the use of phosphate ion can be considered as anion readily precipitating with metal ions. If phosphate buffer with neutral pH is used as electrolyte, the better bio-compatibility will be achieved than most of rechargeable battery using strong acid, strong base or organic solvent as electrolyte solution. There are many metal ions readily precipitating with phos-phate ion, and zinc is one of them

  9. Solid oxide electrochemical reactor science.

    Energy Technology Data Exchange (ETDEWEB)

    Sullivan, Neal P. (Colorado School of Mines, Golden, CO); Stechel, Ellen Beth; Moyer, Connor J. (Colorado School of Mines, Golden, CO); Ambrosini, Andrea; Key, Robert J. (Colorado School of Mines, Golden, CO)

    2010-09-01

    Solid-oxide electrochemical cells are an exciting new technology. Development of solid-oxide cells (SOCs) has advanced considerable in recent years and continues to progress rapidly. This thesis studies several aspects of SOCs and contributes useful information to their continued development. This LDRD involved a collaboration between Sandia and the Colorado School of Mines (CSM) ins solid-oxide electrochemical reactors targeted at solid oxide electrolyzer cells (SOEC), which are the reverse of solid-oxide fuel cells (SOFC). SOECs complement Sandia's efforts in thermochemical production of alternative fuels. An SOEC technology would co-electrolyze carbon dioxide (CO{sub 2}) with steam at temperatures around 800 C to form synthesis gas (H{sub 2} and CO), which forms the building blocks for a petrochemical substitutes that can be used to power vehicles or in distributed energy platforms. The effort described here concentrates on research concerning catalytic chemistry, charge-transfer chemistry, and optimal cell-architecture. technical scope included computational modeling, materials development, and experimental evaluation. The project engaged the Colorado Fuel Cell Center at CSM through the support of a graduate student (Connor Moyer) at CSM and his advisors (Profs. Robert Kee and Neal Sullivan) in collaboration with Sandia.

  10. Nanodevices in nature: Electrochemical aspects

    International Nuclear Information System (INIS)

    Volkov, Alexander G.; Volkova-Gugeshashvili, Maya I.; Brown-McGauley, Courtney L.; Osei, Albert J.

    2007-01-01

    Electrochemical multielectron reactions in photosynthesis and respiration are evaluated by thermodynamic and kinetic analysis. Kharkats and Volkov [Yu.I. Kharkats, A.G. Volkov, Biochim. Biophys. Acta 891 (1987) 56] were the first to present proof that cytochrome c oxidase reduces molecular oxygen by synchronous multielectron mechanism without O 2 - intermediate formation. After this pioneering observation, it became clear that the first step of oxygen reduction is two-electron concerted process. The energy for the H + -pump of cytochrome oxidase is liberated when the third and fourth electrons are added in the last two steps of water formation independent of the reaction pathway. Electrochemical principles govern many biological properties of organisms, such as the generation of electric fields, and the conduction of fast excitation waves. These properties are supported by the function of a variety of natural nanodevices. Ionic channels, as natural nanodevices, control the plasma membrane potential, and the movement of ions across membranes; thereby, regulating various biological functions. Some voltage-gated ion channels work as plasma membrane nanopotentiostats. In plants, excitation waves are possible mechanisms for intercellular and intracellular communication in response to environmental changes. The role of electrified nanointerface of the plasma membrane in signal transduction is discussed as well

  11. Buffered Electrochemical Polishing of Niobium

    Energy Technology Data Exchange (ETDEWEB)

    Ciovati, Gianluigi [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Tian, Hui [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); College of William and Mary, Williamsburg, VA (United States); Corcoran, Sean [Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States)

    2011-03-01

    The standard preparation of superconducting radio-frequency (SRF) cavities made of pure niobium include the removal of a 'damaged' surface layer, by buffered chemical polishing (BCP) or electropolishing (EP), after the cavities are formed. The performance of the cavities is characterized by a sharp degradation of the quality factor when the surface magnetic field exceeds about 90 mT, a phenomenon referred to as 'Q-drop.' In cavities made of polycrystalline fine grain (ASTM 5) niobium, the Q-drop can be significantly reduced by a low-temperature (? 120 °C) 'in-situ' baking of the cavity if the chemical treatment was EP rather than BCP. As part of the effort to understand this phenomenon, we investigated the effect of introducing a polarization potential during buffered chemical polishing, creating a process which is between the standard BCP and EP. While preliminary results on the application of this process to Nb cavities have been previously reported, in this contribution we focus on the characterization of this novel electrochemical process by measuring polarization curves, etching rates, surface finish, electrochemical impedance and the effects of temperature and electrolyte composition. In particular, it is shown that the anodic potential of Nb during BCP reduces the etching rate and improves the surface finish.

  12. Optical and structural properties of porous zinc oxide fabricated via electrochemical etching method

    International Nuclear Information System (INIS)

    Ching, C.G.; Lee, S.C.; Ooi, P.K.; Ng, S.S.; Hassan, Z.; Hassan, H. Abu; Abdullah, M.J.

    2013-01-01

    Highlights: • Hillock like porous structure zinc oxide was obtained via electrochemical etching. • Anisotropic dominance etching process by KOH etchant. • Reststrahlen features are sensitive to multilayer porous structure. • Determination of porosity from IR reflectance spectrum. -- Abstract: We investigated the optical and structural properties of porous zinc oxide (ZnO) thin film fabricated by ultraviolet light-assisted electrochemical etching. This fabrication process used 10 wt% potassium hydroxide solution as an electrolyte. Hillock-like porous ZnO films were successfully fabricated according to the field emission scanning electron microscopy results. The cross-sectional study of the sample indicated that anisotropic-dominated etching process occurred. However, the atomic force microscopic results showed an increase in surface roughness of the sample after electrochemical etching. A resonance hump induced by the porous structure was observed in the infrared reflectance spectrum. Using theoretical modeling technique, ZnO porosification was verified, and the porosity of the sample was determined

  13. Bussing Structure In An Electrochemical Cell

    Science.gov (United States)

    Romero, Antonio L.

    2001-06-12

    A bussing structure for bussing current within an electrochemical cell. The bussing structure includes a first plate and a second plate, each having a central aperture therein. Current collection tabs, extending from an electrode stack in the electrochemical cell, extend through the central aperture in the first plate, and are then sandwiched between the first plate and second plate. The second plate is then connected to a terminal on the outside of the case of the electrochemical cell. Each of the first and second plates includes a second aperture which is positioned beneath a safety vent in the case of the electrochemical cell to promote turbulent flow of gasses through the vent upon its opening. The second plate also includes protrusions for spacing the bussing structure from the case, as well as plateaus for connecting the bussing structure to the terminal on the case of the electrochemical cell.

  14. Nanomaterial-based Electrochemical Sensors for the Detection of Glucose and Cholesterol

    Science.gov (United States)

    Ahmadalinezhad, Asieh

    Electrochemical detection methods are highly attractive for the monitoring of glucose, cholesterol, cancer, infectious diseases, and biological warfare agents due to their low cost, high sensitivity, functionality despite sample turbidity, easy miniaturization via microfabrication, low power requirements, and a relatively simple control infrastructure. The development of implantable biosensors is laden with great challenges, which include longevity and inherent biocompatibility, coupled with the continuous monitoring of analytes. Deficiencies in any of these areas will necessitate their surgical replacement. In addition, random signals arising from non-specific adsorption events can cause problems in diagnostic assays. Hence, a great deal of effort has been devoted to the specific control of surface structures. Nanotechnology involves the creation and design of structures with at least one dimension that is below 100 nm. The optical, magnetic, and electrical properties of nanostructures may be manipulated by altering their size, shape, and composition. These attributes may facilitate improvements in biocompatibility, sensitivity and the specific attachment of biomaterials. Thus, the central theme of this dissertation pertains to highlighting the critical roles that are played by the morphology and intrinsic properties of nanomaterials when they are applied in the development of electrochemical biosensors. For this PhD project, we initially designed and fabricated a novel amperometric glucose biosensor based on the immobilization of glucose oxidase (GOx) on a Prussian blue modified nanoporous gold surface, which exhibited a rapid response and a low detection limit of 2.5 microM glucose. The sensitivity of the biosensor was found to be very high (177 microA/mM) and the apparent Michaelis--Menten constant was calculated to be 2.1 mM. Our study has demonstrated that nanoporous gold provides an excellent matrix for enzyme immobilization. To adopt these advanced

  15. Electrochemical Oxidation of PAHs in Water from Harbor Sediment Purification

    DEFF Research Database (Denmark)

    Muff, Jens; Søgaard, Erik Gydesen

    2010-01-01

    generated oxidant solution with a free chlorine concentration of 2 gL-1. Both strategies resulted in a successful degradation of 5 PAHs to fulfil the discharge limit on 0.010 µgL-1. The intermixing-with-oxidant approach can also be applied as a method to address the actual sediment matrix....... of the discharge water addressing primarily polycyclic aromatic hydrocarbons (PAHs). PAHs are by-products of incomplete combustion of organic materials with recalcitrant and strong mutagenic/carcinogenic properties, due to their benzene analogue structures. PAHs are hydrophobic compounds and their persistence...... evidence for the importance of the indirect oxidation mechanism in the degradation of the PAHs. The proof-of-concept study was conducted both by a direct treatment approach and an intermixing-with-oxidant approach, where the contaminated water was intermixed in different ratios with an electrochemically...

  16. Surface Characterization and Electrochemical Oxidation of Metal Doped Uranium Dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jeongmook; Kim, Jandee; Youn, Young-Sang; Kim, Jong-Goo; Ha, Yeong-Keong; Kim, Jong-Yun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2016-10-15

    Trivalent element in UO{sub 2} matrix makes the oxygen vacancy from loss of oxygen for charge compensation. Tetravalent element alters lattice parameter of UO{sub 2} due to diameter difference between the tetravalent element and replaced U. These structural changes have significant effect on not only relevant fuel performance but also the kinetics of fuel oxidation. Park and Olander explained the stabilization of Ln (III)-doped UO{sub 2} against oxidation based on oxygen potential calculations. In this work, we have been investigated the effect of Gd{sup 3+} and Th{sup 4+} doping on the UO{sub 2} structure with Raman spectroscopy and X-ray diffraction to characterize the surface structure of nuclear fuel material. For Gd doped UO{sub 2}, its electrochemical oxidation behaviors are also investigated. The Gd and Th doped uranium dioxide solid solution pellets with various doping level were investigated by XRD, Raman spectroscopy, SEM, electrochemical experiments to investigate surface structure and electro chemical oxidation behaviors. The lattice parameter evaluated from XRD spectra indicated the formation of solid solutions. Raman spectra showed the existence of the oxygen vacancy. SEM images showed the grain structure on the surface of Gd doped uranium dioxide depending on doping level and oxygen-to-metal ratio.

  17. Electrochemical and Infrared Absorption Spectroscopy Detection of SF₆ Decomposition Products.

    Science.gov (United States)

    Dong, Ming; Zhang, Chongxing; Ren, Ming; Albarracín, Ricardo; Ye, Rixin

    2017-11-15

    Sulfur hexafluoride (SF₆) gas-insulated electrical equipment is widely used in high-voltage (HV) and extra-high-voltage (EHV) power systems. Partial discharge (PD) and local heating can occur in the electrical equipment because of insulation faults, which results in SF₆ decomposition and ultimately generates several types of decomposition products. These SF₆ decomposition products can be qualitatively and quantitatively detected with relevant detection methods, and such detection contributes to diagnosing the internal faults and evaluating the security risks of the equipment. At present, multiple detection methods exist for analyzing the SF₆ decomposition products, and electrochemical sensing (ES) and infrared (IR) spectroscopy are well suited for application in online detection. In this study, the combination of ES with IR spectroscopy is used to detect SF₆ gas decomposition. First, the characteristics of these two detection methods are studied, and the data analysis matrix is established. Then, a qualitative and quantitative analysis ES-IR model is established by adopting a two-step approach. A SF₆ decomposition detector is designed and manufactured by combining an electrochemical sensor and IR spectroscopy technology. The detector is used to detect SF₆ gas decomposition and is verified to reliably and accurately detect the gas components and concentrations.

  18. Investigating electrochemical removal of bacterial biofilms from stainless steel substrates.

    Science.gov (United States)

    Dargahi, Mahdi; Hosseinidoust, Zeinab; Tufenkji, Nathalie; Omanovic, Sasha

    2014-05-01

    Electrochemical removal of biofilms deserves attention because of its ease of use and environmentally friendly nature. We investigated the influence of electrode potential and treatment time on the removal of a 10-day old Pseudomonas aeruginosa biofilm formed on stainless steel 316 L substrates. At electrode potentials more positive than -1.5 V vs. Ag/AgCl, lower removal rates were observed and only partial removal of the biofilm was achieved during a 1-min time interval. Electrostatic repulsion between the film and electrode surface is believed to drive biofilm detachment under these conditions. However, when the biofilm-coated substrates were treated at potentials negative of -1.5 V vs. Ag/AgCl, complete removal of a biofilm was achieved within seconds. Under these conditions, vigorous evolution of hydrogen gas is believed to be responsible for the film removal, mechanically detaching the bacteria and extracellular polymeric matrix from the substrate. Stainless steel substrates were also subjected to repeated cycles of biofilm formation and electrochemical removal. High removal efficiencies were maintained throughout this process suggesting the potential of the proposed technology for application on conductive surfaces in various industrial settings. Copyright © 2014 Elsevier B.V. All rights reserved.

  19. Monitoring dynamic electrochemical processes with in situ ptychography

    Science.gov (United States)

    Kourousias, George; Bozzini, Benedetto; Jones, Michael W. M.; Van Riessen, Grant A.; Dal Zilio, Simone; Billè, Fulvio; Kiskinova, Maya; Gianoncelli, Alessandra

    2018-03-01

    The present work reports novel soft X-ray Fresnel CDI ptychography results, demonstrating the potential of this method for dynamic in situ studies. Specifically, in situ ptychography experiments explored the electrochemical fabrication of Co-doped Mn-oxide/polypyrrole nanocomposites for sustainable and cost-effective fuel-cell air-electrodes. Oxygen-reduction catalysts based on Mn-oxides exhibit relatively high activity, but poor durability: doping with Co has been shown to improve both reduction rate and stability. In this study, we examine the chemical state distribution of the catalytically crucial Co dopant to elucidate details of the Co dopant incorporation into the Mn/polymer matrix. The measurements were performed using a custom-made three-electrode thin-layer microcell, developed at the TwinMic beamline of Elettra Synchrotron during a series of experiments that were continued at the SXRI beamline of the Australian Synchrotron. Our time-resolved ptychography-based investigation was carried out in situ after two representative growth steps, controlled by electrochemical bias. In addition to the observation of morphological changes, we retrieved the spectroscopic information, provided by multiple ptychographic energy scans across Co L3-edge, shedding light on the doping mechanism and demonstrating a general approach for the molecular-level investigation complex multimaterial electrodeposition processes.

  20. Partially separable t matrix

    International Nuclear Information System (INIS)

    Sasakawa, T.; Okuno, H.; Ishikawa, S.; Sawada, T.

    1982-01-01

    The off-shell t matrix is expressed as a sum of one nonseparable and one separable terms so that it is useful for applications to more-than-two body problems. All poles are involved in this one separable term. Both the nonseparable and the separable terms of the kernel G 0 t are regular at the origin. The nonseparable term of this kernel vanishes at large distances, while the separable term behaves asymptotically as the spherical Hankel function. These properties make our expression free from defects inherent in the Jost or the K-matrix expressions, and many applications are anticipated. As the application, a compact expression of the many-level formula is presented. Also the application is suggested to the breakup threebody problem based on the Faddeev equation. It is demonstrated that the breakup amplitude is expressed in a simple and physically interesting form and we can calculate it in coordinate space