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Sample records for nanotube-enhanced flow-injection amperometric

  1. Flow-injection amperometric glucose biosensors based on graphene/Nafion hybrid electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Bong Gill, E-mail: k1811@kaist.ac.kr [Department of Chemical and Biomolecular Engineering (BK21 Program), KAIST, Daejeon 305-701 (Korea, Republic of); Im, Jinkyu, E-mail: JINQ@paran.com [Department of Chemistry and Research Institute of Basic Sciences, Kyung Hee University, 1 Hoegidong, Dongdamoongu, Seoul (Korea, Republic of); Kim, Hoon Sik, E-mail: khs2004@khu.ac.kr [Department of Chemistry and Research Institute of Basic Sciences, Kyung Hee University, 1 Hoegidong, Dongdamoongu, Seoul (Korea, Republic of); Park, HoSeok, E-mail: phs0727@khu.ac.kr [Department of Chemical Engineering, College of Engineering, Kyung Hee University, 1 Seochon-dong, Giheung-gu, Youngin-si, Gyeonggi-do 446-701 (Korea, Republic of)

    2011-11-30

    Graphical abstract: Amperometric biosensors based on graphene hybrids showed the fast, sensitive, and stable amperometric responses in the flow injection system for automatically monitoring glucose. Display Omitted Highlights: > Flow-injection amperometric glucose biosensors were fabricated using reduced graphene oxide/Nafion hybrids. > The electrochemical kinetics of biosensors were comprehensively investigated by analysing electron transfer rate, charge transfer resistance, and ion diffusion coefficient, respectively. > The biosensors exhibited the fast, sensitive, and stable amperometric responses in the flow injection system for detecting glucose. - Abstract: In this research, we demonstrated the fabrication of flow-injection amperometric glucose biosensors based on RGO/Nafion hybrids. The nanohybridization of the reduced graphene oxide (RGO) by Nafion provided the fast electron transfer (ET) for the sensitive amperometric biosensor platforms. The ET rate (k{sub s}) and the charge transfer resistance (R{sub CT}) of GOx-RGO/Nafion hybrids were evaluated to verify the accelerated ET. Moreover, hybrid biosensors revealed a quasi-reversible and surface controlled process, as confirmed by the low peak-to-peak ({Delta}E{sub p}) and linear relations between I{sub p} and scan rate ({nu}). Hybrid biosensors showed the fast response time of {approx}3 s, the sensitivity of 3.8 {mu}A mM{sup -1} cm{sup -2}, the limit of detection of 170 {mu}M, and the linear detection range of 2-20 mM for the flow-injection amperometric detection of glucose. Furthermore, interference effect of oxidizable species such as ascorbic acid (AA) and uric acid (UA) on the performance of hybrid biosensors was prevented at the operating potential of -0.20 V even under the flow injection mode. Therefore, the fast, sensitive, and stable amperometric responses of hybrid biosensors in the flow injection system make it highly suitable for automatically monitoring glucose.

  2. Cross-correlation in flow-injection analysis with parallel flow streams and amperometric detection.

    Science.gov (United States)

    McKean, R E; Curran, D J

    1992-03-01

    Cross-correlation was implemented for flow-injection analysis by using two parallel flow lines, each with amperometric detectors, and driven by peristaltic pumps. One flow line was used to generate the reference signal for an analog correlator circuit and the other to generate the analyte signal. Cross-correlation was performed by multiplying these signals together at a time delay of zero, followed by low pass filtering. Using dopamine as a test system, improvements in signal-to-noise ratios of about two orders of magnitude were found for the correlation signal over the direct measurement of the electrode current.

  3. Flow injection analysis using carbon film resistor electrodes for amperometric determination of ambroxol.

    Science.gov (United States)

    Felix, Fabiana S; Brett, Christopher M A; Angnes, Lúcio

    2008-06-30

    Flow injection analysis (FIA) using a carbon film sensor for amperometric detection was explored for ambroxol analysis in pharmaceutical formulations. The specially designed flow cell designed in the lab generated sharp and reproducible current peaks, with a wide linear dynamic range from 5x10(-7) to 3.5x10(-4) mol L(-1), in 0.1 mol L(-1) sulfuric acid electrolyte, as well as high sensitivity, 0.110 Amol(-1) L cm(-2) at the optimized flow rate. A detection limit of 7.6x10(-8) mol L(-1) and a sampling frequency of 50 determinations per hour were achieved, employing injected volumes of 100 microL and a flow rate of 2.0 mL min(-1). The repeatability, expressed as R.S.D. for successive and alternated injections of 6.0x10(-6) and 6.0x10(-5) mol L(-1) ambroxol solutions, was 3.0 and 1.5%, respectively, without any noticeable memory effect between injections. The proposed method was applied to the analysis of ambroxol in pharmaceutical samples and the results obtained were compared with UV spectrophotometric and acid-base titrimetric methods. Good agreement between the results utilizing the three methods and the labeled values was achieved, corroborating the good performance of the proposed electrochemical methodology for ambroxol analysis.

  4. Determination of available phosphorus in soils by using a new extraction procedure and a flow injection amperometric system.

    Science.gov (United States)

    Jakmunee, Jaroon; Junsomboon, Jaroon

    2009-09-15

    A new extraction procedure based on an off-line extraction column was proposed for extracting of available phosphorus from soils. The column was fabricated from a plastic syringe fitted at the bottom with a cotton wool and a piece of filter paper to support a soil sample. An aliquot (50 mL) of extracting solution (0.05 M HCl+0.0125 M H(2)SO(4)) was used to extract the sample under gravity flow and the eluate was collected in a polyethylene bottle. The extract was then analyzed for phosphorus contents by a simple flow injection amperometric system, employing a set of three-way solenoid valves as an injection valve. The method is based on the electrochemical reduction of 12-molybdophosphate which is produced on-line by the reaction of orthophosphate with acidic molybdate and the electrical current produced was directly proportional to the concentration of phosphate in range of 0.1-10.0 mg L(-1) PO(4)-P, with a detection limit of 0.02 mg L(-1). Relative standard for 11 replicate injections of 5 mg L(-1) PO(4)-P was 0.5%. A sample through put of 35 h(-1) was achieved, with consumption of 14 mg KCl, 10mg ammonium molybdate and 0.05 mL H(2)SO(4) per analysis. The detection system does not suffer from the interferences that are encountered in the photometric method such as colored substances, colloids, metal ions, silicate and refractive index effect (Schlieren effect). The results obtained by the column extraction procedure were well correlated with those obtained by the steady-state extraction procedure, but showed slightly higher extraction efficiency.

  5. Simple flow injection for determination of sulfite by amperometric detection using glassy carbon electrode modified with carbon nanotubes-PDDA-gold nanoparticles.

    Science.gov (United States)

    Amatatongchai, Maliwan; Sroysee, Wongduan; Chairam, Sanoe; Nacapricha, Duangjai

    2015-02-01

    A new approach is presented for sensitive and selective measurement of sulfite (SO3(2-)) in beverages based on a simple flow injection system with amperometric detection. In this work, the sulfite sensor was a glassy carbon electrode modified with multiwall carbon nanotubes-poly(diallyldimethylammonium chloride)-gold nanoparticles composites (CNTs-PDDA-AuNPs/GC). Electrochemical oxidation of sulfite with this electrode was first studied in 0.1M phosphate buffer (pH 7.0) using cyclic voltammetry. The results indicated that the CNTs-PDDA-AuNPs/GC electrode possesses electrocatalytic activity for the oxidation of sulfite with high sensitivity and selectivity. Sulfite was quantified using amperometric measurement with the new sensor at +0.4V vs Ag/AgCl in conjunction with flow injection. The linear working range for the quantitation of sulfite was 2-200 mg L(-1) (r(2)=0.998) with a detection limit of 0.03 mg L(-1) (3σ of blank) and an estimated precision of 1.5%.The proposed method was successfully applied to the determination of sulfite in fruit juices and wines with a sample throughput of 23 samples per hour. Copyright © 2014 Elsevier B.V. All rights reserved.

  6. Development of a chromatographic low pressure flow injection system using amperometric detection: Application to the analysis of niacin in coffee.

    Science.gov (United States)

    Santos, João Rodrigo; Rangel, António O S S

    2015-11-15

    In this work, an analytical flow system able to perform low pressure chromatography with amperometric detection is presented. As case study, the determination of niacin (vitamin B3) in coffee brewed samples was selected. The manifold comprised a 1.0 cm length monolithic column coated with didecyldimethylammonium bromide, a laboratory-made boron doped diamond electrode, and featured in-line ionic strength adjustment of the mobile phase. The figures of merit concerning the selected case study namely, detection limit, 7.90 × 10(-7) M, determination rate, ca. 10 samplesh(-1), mobile phase and ISA solution consumption, ca. 2.6 mL per analysis, and CV, below 5% for retention time and peak height, showed the competitiveness of this analytical strategy comparing to the described HPLC methods for niacin determination. The strategy displays a simple configuration, low cost, fast and easy assembling, foreseeing its use to general purpose applications. Copyright © 2015 Elsevier Ltd. All rights reserved.

  7. Determination of sulfite by pervaporation-flow injection with amperometric detection using copper hexacyanoferrate-carbon nanotube modified carbon paste electrode.

    Science.gov (United States)

    Alamo, Lori Shayne T; Tangkuaram, Tanin; Satienperakul, Sakchai

    2010-06-15

    A pervaporation-flow injection (PFI) method was developed for the determination of sulfite in selected food samples using a copper hexacyanoferrate-carbon nanotube (CuHCF-CNT)-modified carbon paste electrode. The electrochemical behavior of the modified electrode was observed using cyclic voltammetry in comparison to a CuHCF-modified carbon paste electrode and a bare carbon paste electrode at a scan rate of 100mVs(-1) in 0.10M KNO(3). The bare carbon paste electrode gave the lowest response to sulfite, while the presence of CuHCF made the detection of sulfite possible through electrocatalytic oxidation by the hexacyanoferrate in the modified electrodes. The presence of CNT in the CuHCF-CNT-modified sensor gave the most remarkable current for the detection of sulfite and was then used as a working electrode in the amperometric flow-through cell in the pervaporation flow injection system. The PFI method involves the injection of a standard or sample sulfite solution into a sulfuric acid donor stream to generate sulfur dioxide gas and evaporate into the headspace of the pervaporation unit. The sulfur dioxide diffuses through the PTFE hydrophobic membrane into a potassium nitrate acceptor stream and reverts to the sulfite form, which, subsequently, is transported to the electrochemical flow cell where it is analyzed amperometrically at a CuHCF-CNT-modified electrode at +0.55V (vs. Ag/AgCl). The detection was determined to be applicable in the sulfite concentration range of 0.5-50mgL(-1). The sensitivity, detection limit, and sample throughput were determined to be 2.105nALmg(-1), 0.40mgL(-1) and 11h(-1), respectively. The developed PFI method, coupled with the CuHCF-CNT-modified carbon paste electrode, was applied in the determination of sulfite content in sulfite-containing food products. The results agreed well with those obtained through the officially recommended differential pulse polarographic method.

  8. Fabrication of an Amperometric Flow-Injection Microfluidic Biosensor Based on Laccase for In Situ Determination of Phenolic Compounds

    Directory of Open Access Journals (Sweden)

    Juan C. Gonzalez-Rivera

    2015-01-01

    Full Text Available We aim to develop an in situ microfluidic biosensor based on laccase from Trametes pubescens with flow-injection and amperometry as the transducer method. The enzyme was directly immobilized by potential step chronoamperometry, and the immobilization was studied using cyclic voltammetry and electrochemical impedance spectroscopy. The electrode response by amperometry was probed using ABTS and syringaldazine. A shift of interfacial electron transfer resistance and the electron transfer rate constant from 18.1 kΩ to 3.9 MΩ and 4.6 × 10−2 cm s−1 to 2.1 × 10−4 cm s−1, respectively, evidenced that laccase was immobilized on the electrode by the proposed method. We established the optimum operating conditions of temperature (55°C, pH (4.5, injection flow rate (200 µL min−1, and applied potential (0.4 V. Finally, the microfluidic biosensor showed better lower limit of detection (0.149 µM and sensitivity (0.2341 nA µM−1 for ABTS than previous laccase-based biosensors and the in situ operation capacity.

  9. Evaluation of a nitrogen-incorporated tetrahedral amorphous carbon thin film for the detection of tryptophan and tyrosine using flow injection analysis with amperometric detection.

    Science.gov (United States)

    Jarošová, Romana; Rutherford, Joy; Swain, Greg M

    2016-10-17

    We report on the analytical performance of a tetrahedral amorphous carbon (ta-C:N) thin-film electrode in flow injection analysis with amperometric detection. Two model redox analytes were used to evaluate the electrode response because of their positive detection potentials and propensity (i.e., reaction products) to adsorb and foul sp 2 carbon electrodes: tyrosine and tryptophan. ta-C:N electrodes are attractive for electroanalytical applications because they possesses many of the excellent properties of boron-doped nanocrystalline diamond (BDD) and they can be deposited at or near room temperature. The results show that the ta-C:N electrode exhibits lower background current and noise than glassy carbon (GC). The electrode was stable microstructurally at the positive potentials used for detection, ∼1.1 V, of these two amino acids and it exhibited superior analytical detection figures of merit as compared to GC and as good or superior to BDD. The linear dynamic range for both analytes at ta-C:N was from 0.1 to 100 μmol L -1 , the sensitivity was 8-12 mA L mol -1 , the short-term response variability was 1-2%, and the minimum detectable concentration was 89.7 ± 0.9 nM (18.3 μg L -1 or 0.46 ng) for tryptophan and 120 ± 11 nM (21.7 μg L -1 or 0.54 ng) for tyrosine. The analytical detection figures of merit for these amino acids at GC and BDD are also presented for comparison as is characterization data for the chemical composition and microstructure of the ta-C:N film.

  10. Cost-effective flow injection amperometric system with metal nanoparticle loaded carbon nanotube modified screen printed carbon electrode for sensitive determination of hydrogen peroxide.

    Science.gov (United States)

    Reanpang, Preeyaporn; Themsirimongkon, Suwaphid; Saipanya, Surin; Chailapakul, Orawon; Jakmunee, Jaroon

    2015-11-01

    Various metal nanoparticles (NPs) decorated on carbon nanotube (CNT) was modified on the home-made screen printed carbon electrode (SPCE) in order to enhances sensitivity of hydrogen peroxide (H2O2) determination. The simple casting method was used for the electrode modification. The monometallic and bimetallic NPs modified electrodes were investigated for their electrochemical properties for H2O2 reduction. The Pd-CNT/SPCE is appropriated to measure the H2O2 reduction at a potential of -0.3 V, then this modified electrode was incorporated with a home-made flow through cell and applied in a simple flow injection amperometry (FI-Amp). Some parameters influencing the resulted modified electrode and the FI-Amp system were studied. The proposed detection system was able to detect H2O2 in the range of 0.1-1.0 mM, with detection limit of 20 µM. Relative standard deviation for 100 replicated injections of 0.6 mM H2O2 was 2.3%. The reproducibility of 6 electrodes preparing in 3 different lots was 8.2%. It was demonstrated for determination of H2O2 in disinfectant, hair colorant and milk samples. Recoveries in the range of 90-109% were observed. The developed system provided high stability, good repeatability, high sample throughput and low reagent consumption. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. Flow injection amperometric sandwich-type aptasensor for the determination of human leukemic lymphoblast cancer cells using MWCNTs-Pdnano/PTCA/aptamer as labeled aptamer for the signal amplification.

    Science.gov (United States)

    Amouzadeh Tabrizi, Mahmoud; Shamsipur, Mojtaba; Saber, Reza; Sarkar, Saeed

    2017-09-08

    In this research, we demonstrated a flow injection amperometric sandwich-type aptasensor for the determination of human leukemic lymphoblasts (CCRF-CEM) based on poly(3,4-ethylenedioxythiophene) decorated with gold nanoparticles (PEDOT-Au nano ) as a nano platform to immobilize thiolated sgc8c aptamer and multiwall carbon nanotubes decorated with palladium nanoparticles/3,4,9,10-perylene tetracarboxylic acid (MWCNTs-Pd nano /PTCA) to fabricate catalytic labeled aptamer. In the proposed sensing strategy, the CCRF-CEM cancer cells were sandwiched between immobilized sgc8c aptamer on PEDOT-Au nano modified surface electrode and catalytic labeled sgc8c aptamer (MWCNTs-Pd nano /PTCA/aptamer). After that, the concentration of CCRF-CEM cancer cells was determined in presence of 0.1 mM hydrogen peroxide (H 2 O 2 ) as an electroactive component. The attached MWCNTs-Pd nano nanocomposites to CCRF-CEM cancer cells amplified the electrocatalytic reduction of H 2 O 2 and improved the sensitivity of the sensor to CCRF-CEM cancer cells. The MWCNT-Pd nano nanocomposite was characterized with transmission electron microscopy (TEM) and energy dispersive X-ray (EDX). The electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were used to confirm the stepwise changes in the electrochemical surface properties of the electrode. The proposed sandwich-type electrochemical aptasensor exhibited an excellent analytical performance for the detection of CCRF-CEM cancer cells ranging from 1.0 × 10 1 to 5.0 × 10 5  cells mL -1 . The limit of detection was 8 cells mL -1 . The proposed aptasensor showed high selectivity toward CCRF-CEM cancer cells. The proposed aptasensor was also applied to the determination of CCRF-CEM cancer cells in human serum samples. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Flow Injection Analysis in Industrial Biotechnology

    DEFF Research Database (Denmark)

    Hansen, Elo Harald; Miró, Manuel

    2009-01-01

    Flow injection analysis (FIA) is an analytical chemical continuous-flow (CF) method which in contrast to traditional CF-procedures does not rely on complete physical mixing (homogenisation) of the sample and the reagent(s) or on attaining chemical equilibria of the chemical reactions involved. Ex...

  13. Retro-review of flow injection analysis

    DEFF Research Database (Denmark)

    Ruzicka, Jaromir; Hansen, Elo Harald

    2008-01-01

    It is indeed unusual for authors to review their own monograph – J. Ruzicka, E.H. Hansen, Flow Injection Analysis, 2nd Edition, Wiley, Chichester, West Sussex, UK, 1988. – and even more so if the book was published 20 years ago. Yet such an exercise might yield a perspective on the progress of an...

  14. Chemiluminescence detection of peroxynitrite with flow injection

    Science.gov (United States)

    Kang, Dai; Evmiridis, Nick P.; Vlessidis, Athanasios; Zhou, Yikai

    2001-09-01

    Peroxynitrite is an important derivative made by nitric oxide in vivo. It can make damages in many kinds of tissue and cells. Its research value in heart disease and cancer is a very high. A sensitive, specific method for analysis of peroxynitrite is described. In this method, chemiluminescence reaction between perodynitrite and luminol was used to detect with flow injection system. The assay has a detection limit of 2 by 10-8 mol L-1, and linear range of 5 by 10-8 mol L-1 to 5 by 10-5 mol L-1. The application o f flow injection system offers the possibility to establish biosensor for real-time detection of perodynitrite.

  15. Recent advances in flow injection analysis.

    Science.gov (United States)

    Trojanowicz, Marek; Kołacińska, Kamila

    2016-04-07

    A dynamic development of methodologies of analytical flow injection measurements during four decades since their invention has reinforced the solid position of flow analysis in the arsenal of techniques and instrumentation of contemporary chemical analysis. With the number of published scientific papers exceeding 20,000, and advanced instrumentation available for environmental, food, and pharmaceutical analysis, flow analysis is well established as an extremely vital field of modern flow chemistry, which is developed simultaneously with methods of chemical synthesis carried out under flow conditions. This review work is based on almost 300 original papers published mostly in the last decade, with special emphasis put on presenting novel achievements from the most recent 2-3 years in order to indicate current development trends of this methodology. Besides the evolution of the design of whole measuring systems, and including especially new applications of various detections methods, several aspects of implications of progress in nanotechnology, and miniaturization of measuring systems for application in different field of modern chemical analysis are also discussed.

  16. Implantable enzyme amperometric biosensors.

    Science.gov (United States)

    Kotanen, Christian N; Moussy, Francis Gabriel; Carrara, Sandro; Guiseppi-Elie, Anthony

    2012-05-15

    The implantable enzyme amperometric biosensor continues as the dominant in vivo format for the detection, monitoring and reporting of biochemical analytes related to a wide range of pathologies. Widely used in animal studies, there is increasing emphasis on their use in diabetes care and management, the management of trauma-associated hemorrhage and in critical care monitoring by intensivists in the ICU. These frontier opportunities demand continuous indwelling performance for up to several years, well in excess of the currently approved seven days. This review outlines the many challenges to successful deployment of chronically implantable amperometric enzyme biosensors and emphasizes the emerging technological approaches in their continued development. The foreign body response plays a prominent role in implantable biotransducer failure. Topics considering the approaches to mitigate the inflammatory response, use of biomimetic chemistries, nanostructured topographies, drug eluting constructs, and tissue-to-device interface modulus matching are reviewed. Similarly, factors that influence biotransducer performance such as enzyme stability, substrate interference, mediator selection and calibration are reviewed. For the biosensor system, the opportunities and challenges of integration, guided by footprint requirements, the limitations of mixed signal electronics, and power requirements, has produced three systems approaches. The potential is great. However, integration along the multiple length scales needed to address fundamental issues and integration across the diverse disciplines needed to achieve success of these highly integrated systems, continues to be a challenge in the development and deployment of implantable amperometric enzyme biosensor systems. Copyright © 2012 Elsevier B.V. All rights reserved.

  17. Electrochemical study and flow injection analysis of paracetamol in pharmaceutical formulations based on screen-printed electrodes and carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Fanjul-Bolado, Pablo [DropSens, S.L., Edificio Severo Ochoa, Campus El Cristo, 33006 Oviedo, Asturias (Spain); Lamas-Ardisana, Pedro Jose [Departamento de Quimica Fisica y Analitica, Universidad de Oviedo, Julian Claveria 8, 33006 Oviedo, Asturias (Spain); Hernandez-Santos, David [DropSens, S.L., Edificio Severo Ochoa, Campus El Cristo, 33006 Oviedo, Asturias (Spain); Costa-Garcia, Agustin, E-mail: costa@fq.uniovi.es [Departamento de Quimica Fisica y Analitica, Universidad de Oviedo, Julian Claveria 8, 33006 Oviedo, Asturias (Spain)

    2009-04-13

    Acetaminophenol or paracetamol is one of the most commonly used analgesics in pharmaceutical formulations. Acetaminophen is electroactive and voltammetric mechanistic studies for the electrode processes of the acetaminophenol/N-acetyl-p-quinoneimine redox system are presented. Carbon nanotubes modified screen-printed electrodes with enhanced electron transfer properties are used for the study of the electrochemical-chemical oxidation mechanism of paracetamol at pH 2.0. Quantitative analysis of paracetamol by using its oxidation process (in a Britton-Robinson buffer solution pH 10.0) at +0.20 V (vs. an Ag pseudoreference electrode) on an untreated screen-printed carbon electrode (SPCE) was carried out. Thus, a cyclic voltammetric based reproducible determination of acetaminophen (R.S.D., 2.2%) in the range 2.5 x 10{sup -6} M to 1 x 10{sup -3} M, was obtained. However, when SPCEs are used as amperometric detectors coupled to a flow injection analysis (FIA) system, the detection limit achieved for paracetamol was 1 x 10{sup -7} M, one order of magnitude lower than that obtained by voltammetric analysis. The repeatability of the amperometric detection with the same SPCE is 2% for 15 successive injections of 10{sup -5} M acetaminophen and do not present any memory effect. Finally, the applicability of using screen-printed carbon electrodes for the electrochemical detection of paracetamol (i.e. for quality control analysis) was demonstrated by using two commercial pharmaceutical products.

  18. Determination of Acidity Constants by Gradient Flow-Injection Titration

    Science.gov (United States)

    Conceicao, Antonio C. L.; Minas da Piedade, Manuel E.

    2006-01-01

    A three-hour laboratory experiment, designed for an advanced undergraduate course in instrumental analysis that illustrates the application of the gradient chamber flow-injection titration (GCFIT) method with spectrophotometric detection to determine acidity constants is presented. The procedure involves the use of an acid-base indicator to obtain…

  19. Dispersion behaviour of solid particles in flow-injection analysis

    NARCIS (Netherlands)

    Hulsman, M.H.F.M.; Hulsman, M.H.F.M.; Bos, M.; van der Linden, W.E.

    1997-01-01

    In order to achieve a reproducible on-line pretreatment of slurry samples in flow-injection analysis the dispersion behaviour of these samples has to be examined. This paper reports the effects of flow rate and some configurations of reaction manifolds. The reaction manifolds were a straight tube

  20. Flow Injection Analysis: A Revolution in Modern Analytical Chemistry

    DEFF Research Database (Denmark)

    Hansen, Elo Harald

    1996-01-01

    A review is made of the fundamentals of Flow Injection Analysis (FIA), and the versatility and applicability of this analytical concept is demonstrated by a series of examples, comprizing the use of different types of FIA-manifolds and various detection devices (optical and electrochemical...

  1. The Impact of Flow Injection on Modern Chemical Analysis

    DEFF Research Database (Denmark)

    Hansen, Elo Harald

    to implement procedures which previously were difficult or, actually, impossible to execute by conventional means. Clever examples are exploitation of bio-or chemiluminescence, methods relying on kinetic discrimination schemes, assay of metastable constituents, or the use of on-line separation......There is no doubt that Flow Injection Analysis (FIA) has had a profound impact on the ways and means that modern analytical chemical procedures are performed. This is amply reflected in the voluminous scientific literature, which by the middle of 2004 passed more than 14,500 FIA...

  2. Flow Injection and Atomic Absorption Spectrometry (FI-AAS) -

    DEFF Research Database (Denmark)

    Hansen, Elo Harald

    1996-01-01

    One of the advantages of the flow injection (FI) concept is that it is compatible with virtually all detection techniques. Being a versatile vehicle for enhancing the performance of the individual detection devices, the most spectacular results have possibly been obtained in conjunction with atomic...... absorption spectrometry (AAS). Initially with flame-AAS (fAAS) procedures, later for hydride generation (HG) techniques, and most recently in combination with electrothermal AAS (ETAAS). The common denominator for all these procedures is the inherently precise and strictly reproducible timing in FI from...

  3. FLOW INJECTION AMPEROMETRIC DETECTION OF OP NERVE AGENTS BASED ON AN ORGANOPHOSPHORUS-HYDROLASE BIOSENSOR DETECTOR. (R828160)

    Science.gov (United States)

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  4. Versatile Flow-Injection Amperometric Ion Detector Based on an Interface between Two Immiscible Electrolyte Solutions: Numerical and Experimental Characterization

    DEFF Research Database (Denmark)

    Deryabina, Maria; Hansen, Steen H.; Jensen, Henrik

    2011-01-01

    for different application with different requirement for detection limits and dynamic range. A disposable membrane was employed which reduces the need for surface cleaning and prevents sample carryover between different applications. For the lowest cell volumes the detection chamber approaches a thin layer...

  5. Amperometric screen-printed algal biosensor with flow injection analysis system for detection of environmental toxic compounds

    International Nuclear Information System (INIS)

    Shitanda, Isao; Takamatsu, Satoshi; Watanabe, Kunihiro; Itagaki, Masayuki

    2009-01-01

    A screen-printed algal biosensor was fabricated for evaluation of toxicity of chemicals. An algal ink was prepared by mixing unicellular microalga Chlorella vulgaris cells, carbon nanotubes and sodium alginate solution. The algal ink was immobilized directly on a screen-printed carbon electrode surface using screen-printing technique. Photosynthetically generated oxygen of the immobilized algae was monitored amperometically. Responses of the algal biosensor to four toxic compounds, 6-chloro-N-ethyl-N-isopropyl-1,3,5-triazine-2,4-diamine (atrazine) and 3-(3,4-dichlorophenyl)-1,1-diethylurea (DCMU) were evaluated as inhibition ratios of the reduction current. The concentrations that gave 50% inhibition of the oxygen reduction current (IC ' 50 ) for atrazine and DCMU were 12 and 1 μmol dm -3 , respectively. In comparison with the conventional algal biosensors, in which the algal cells were entrapped in an alginate gel and immobilized on the surface of a transparent indium tin oxide electrode, the present sensor is much smaller and less expensive, with the shorter assay time.

  6. Sensitive flow-injection spectrophotometric analysis of bromopride

    Science.gov (United States)

    Lima, Liliane Spazzapam; Weinert, Patrícia Los; Pezza, Leonardo; Pezza, Helena Redigolo

    2014-12-01

    A flow injection spectrophotometric procedure employing merging zones is proposed for direct bromopride determination in pharmaceutical formulations and biological fluids. The proposed method is based on the reaction between bromopride and p-dimethylaminocinnamaldehyde (p-DAC) in acid medium, in the presence of sodium dodecyl sulfate (SDS), resulting in formation of a violet product (λmax = 565 nm). Experimental design methodologies were used to optimize the experimental conditions. The Beer-Lambert law was obeyed in a bromopride concentration range of 3.63 × 10-7 to 2.90 × 10-5 mol L-1, with a correlation coefficient (r) of 0.9999. The limits of detection and quantification were 1.07 × 10-7 and 3.57 × 10-7 mol L-1, respectively. The proposed method was successfully applied to the determination of bromopride in pharmaceuticals and human urine, and recoveries of the drug from these media were in the ranges 99.6-101.2% and 98.6-102.1%, respectively. This new flow injection procedure does not require any sample pretreatment steps.

  7. Flow-Injection Responses of Diffusion Processes and Chemical Reactions

    DEFF Research Database (Denmark)

    Andersen, Jens Enevold Thaulov

    2000-01-01

    The technique of Flow-injection Analysis (FIA), now aged 25 years, offers unique analytical methods that are fast, reliable and consuming an absolute minimum of chemicals. These advantages together with its inherent feasibility for automation warrant the future applications of FIA as an attractiv...... be used in the resolution of FIA profiles to obtain information about the content of interference’s, in the study of chemical reaction kinetics and to measure absolute concentrations within the FIA-detector cell.......The technique of Flow-injection Analysis (FIA), now aged 25 years, offers unique analytical methods that are fast, reliable and consuming an absolute minimum of chemicals. These advantages together with its inherent feasibility for automation warrant the future applications of FIA as an attractive...... tool of automated analytical chemistry. The need for an even lower consumption of chemicals and for computer analysis has motivated a study of the FIA peak itself, that is, a theoretical model was developed, that provides detailed knowledge of the FIA profile. It was shown that the flow in a FIA...

  8. Redesigning flow injection after 40 years of development: Flow programming.

    Science.gov (United States)

    Ruzicka, Jaromir Jarda

    2018-01-01

    Automation of reagent based assays, by means of Flow Injection (FI), is based on sample processing, in which a sample flows continuously towards and through a detector for quantification of the target analyte. The Achilles heel of this methodology, the legacy of Auto Analyzer®, is continuous reagent consumption, and continuous generation of chemical waste. However, flow programming, assisted by recent advances in precise pumping, combined with the lab-on-valve technique, allows the FI manifold to be designed around a single confluence point through which sample and reagents are sequentially directed by means of a series of flow reversals. This approach results in sample/reagent mixing analogous to the traditional FI, reduces sample and reagent consumption, and uses the stop flow technique for enhancement of the yield of chemical reactions. The feasibility of programmable Flow Injection (pFI) is documented by example of commonly used spectrophotometric assays of, phosphate, nitrate, nitrite and glucose. Experimental details and additional information are available in online tutorial http://www.flowinjectiontutorial.com/. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Flow Injection as a Teaching Tool for Gravimetric Analysis

    Science.gov (United States)

    Sartini, Raquel P.; Zagatto, Elias A. G.; Oliveira, Cláudio C.

    2000-06-01

    A flow-injection system to carry out gravimetric analysis is presented. Students are faced with an instrumental approach for gravimetric procedures. Crucibles, muffle furnaces, and desiccators are not required. A flowing suspension is established by simultaneously injecting an aqueous sample and a precipitating reagent into two merging carrier streams. The precipitate is accumulated on a minifilter hanging under the plate of an analytical balance and is weighed inside the main stream. Since Archimedes' principle holds, a drying step is not needed. After measurement, the precipitate is dissolved and disposed of. As an application, the determination of phosphate based on precipitation with ammonium and magnesium ions in slightly alkaline medium is chosen. The proposed system is very stable and well suited for demonstration. When applied to analysis of fertilizer extracts with 0.10-1.00% w/v P, it yields precise results (RSD < 0.042) in agreement with an official spectrophotometric method.

  10. A flow-through amperometric sensor based on dialysis tubing and free enzyme reactors.

    Science.gov (United States)

    Böhm, S; Pijanowska, D; Olthuis, W; Bergveld, P

    2001-08-01

    A generic flow-through amperometric microenzyme sensor is described, which is based on semi-permeable dialysis tubing carrying the sample to be analyzed. This tubing (300 microm OD) is led through a small cavity, containing the working and reference electrode. By filling this cavity with a few microl of an appropriate enzyme solution, an amperometric enzyme sensor results. As the dialysis tubing is impermeable for large molecular species such as enzymes, this approach does not require any immobilization chemistry, and as a consequence the enzyme is present in its natural free form. Based on this principle, amperometric sensors for lactate, glucose, and glutamate were formed by filling cavities, precision machined in Perspex, with buffered solutions containing respectively, lactate-, glucose-, and glutamate-oxidase. All sensors showed a large linear range (0-35 mM for glucose, 0-3 mM for lactate, and 0-5 mM for glutamate) covering the complete physiological range. The lower detection limit was in the order of 15-50 microM. Applicability in flow injection analysis systems is demonstrated.

  11. Flow injection kinetic spectrofluorimetric determination of trace amounts of osmium

    Science.gov (United States)

    Tang, Bo; Zhang, Hui; Wang, Yan

    2005-07-01

    A flow injection (FI) kinetic spectrofluorimetric method is described for the determination of osmium(IV) and the possible mechanism of catalytic reaction is discussed. The method is based on the fluorescence enhancing reaction of o-vanillin furfuralhydrazone (OVFH) with potassium bromate, which is catalyzed by Os(IV) in water medium at pH 6.10 and 45 °C. OVFH is newly synthesized and its ionization, IR and elemental analysis are established. Under these experimental conditions, the oxidized product of OVFH has excitation and emission maxima at 337 and 490 nm, respectively. The linear range of this method is 0-600 ng ml -1 with the R.S.D. of 1.2%. The detection limit is 1.0 ng ml -1 of Os(IV). A high analysis rate of 24 samples h -1 is obtained by the FI method. The proposed method is applied successfully to determine Os(IV) in synthetic mixture and mineral samples, and the results are well consistent with the standard values.

  12. Flow injection analysis with simple chemiluminescence detector for hypoxanthine

    Energy Technology Data Exchange (ETDEWEB)

    Yagiuda, K.; Henmi, A.; Sakamura, K.; Ito, S.; Asano, Y. [DKK Corp., Tokyo (Japan); Hayashi, K. [Nichirei Corp., Tokyo (Japan); Karube, I. [The University of Tokyo, Tokyo (Japan). Research Center for Advanced Science and Technology

    1995-12-05

    A low cost chemiluminescence detector with a photodiode for flow injection analysis (FIA) of hypoxanthine in fish and meat was developed for quality control in food industry. In this system hypoxanthine is oxidized enzymatically to produce hydrogen peroxide during passage through the xanthine oxidase immobilized reactor. Then, chemi-luminescence caused by mixing hydrogen peroxide with chemiluminescence reagent was detected by the flow through photodiode cell that was designed to detect efficiently weak chemiluminescence. This light intensity was proportional to hypoxanthine concentration. As a result a linear working curve was obtained from 2{times}10{sup -7} to 2{times}10{sup -4} mol 1{sup -1} hypoxanthine concentration in this FIA system. The present system with the photodiode detector was applied to the determination of hypoxanthine in fish and meat samples. The results were compared with those obtained by the conventional HPLC method. Analytical results for fish samples obtained by the present FlA method were fairly in good agreement with those obtained by the conventional HPLC method. Correlation factor and regression line between both methods were 0.978 and Y = 0.89X + 0.66 respectively. The present FlA system was concluded to be available as a simple, easy-handling and reliable instrument for quality control in food industry. 16 refs., 5 figs., 1 tab.

  13. Development of flow injection analysis technique for uranium estimation

    International Nuclear Information System (INIS)

    Paranjape, A.H.; Pandit, S.S.; Shinde, S.S.; Ramanujam, A.; Dhumwad, R.K.

    1991-01-01

    Flow injection analysis is increasingly used as a process control analytical technique in many industries. It involves injection of the sample at a constant rate into a steady flowing stream of reagent and passing this mixture through a suitable detector. This paper describes the development of such a system for the analysis of uranium (VI) and (IV) and its gross gamma activity. It is amenable for on-line or automated off-line monitoring of uranium and its activity in process streams. The sample injection port is suitable for automated injection of radioactive samples. The performance of the system has been tested for the colorimetric response of U(VI) samples at 410 nm in the range of 35 to 360mg/ml in nitric acid medium using Metrohm 662 Photometer and a recorder as detector assembly. The precision of the method is found to be better than +/- 0.5%. This technique with certain modifications is used for the analysis of U(VI) in the range 0.1-3mg/ailq. by alcoholic thiocynate procedure within +/- 1.5% precision. Similarly the precision for the determination of U(IV) in the range 15-120 mg at 650 nm is found to be better than 5%. With NaI well-type detector in the flow line, the gross gamma counting of the solution under flow is found to be within a precision of +/- 5%. (author). 4 refs., 2 figs., 1 tab

  14. Flow injection analysis: Emerging tool for laboratory automation in radiochemistry

    International Nuclear Information System (INIS)

    Egorov, O.; Ruzicka, J.; Grate, J.W.; Janata, J.

    1996-01-01

    Automation of routine and serial assays is a common practice of modern analytical laboratory, while it is virtually nonexistent in the field of radiochemistry. Flow injection analysis (FIA) is a general solution handling methodology that has been extensively used for automation of routine assays in many areas of analytical chemistry. Reproducible automated solution handling and on-line separation capabilities are among several distinctive features that make FI a very promising, yet under utilized tool for automation in analytical radiochemistry. The potential of the technique is demonstrated through the development of an automated 90 Sr analyzer and its application in the analysis of tank waste samples from the Hanford site. Sequential injection (SI), the latest generation of FIA, is used to rapidly separate 90 Sr from interfering radionuclides and deliver separated Sr zone to a flow-through liquid scintillation detector. The separation is performed on a mini column containing Sr-specific sorbent extraction material, which selectively retains Sr under acidic conditions. The 90 Sr is eluted with water, mixed with scintillation cocktail, and sent through the flow cell of a flow through counter, where 90 Sr radioactivity is detected as a transient signal. Both peak area and peak height can be used for quantification of sample radioactivity. Alternatively, stopped flow detection can be performed to improve detection precision for low activity samples. The authors current research activities are focused on expansion of radiochemical applications of FIA methodology, with an ultimate goal of creating a set of automated methods that will cover the basic needs of radiochemical analysis at the Hanford site. The results of preliminary experiments indicate that FIA is a highly suitable technique for the automation of chemically more challenging separations, such as separation of actinide elements

  15. Carbon nanotube enhanced membrane distillation for online preconcentration of trace pharmaceuticals in polar solvents.

    Science.gov (United States)

    Gethard, Ken; Mitra, Somenath

    2011-06-21

    Carbon nanotube enhanced membrane distillation (MD) is presented as a novel, online analytical preconcentration method for removing polar solvents thereby concentrating the analytes, making this technique an alternate to conventional thermal evaporation. In a carbon nanotube immobilized membrane (CNIM), the CNTs serve as sorbent sites and provide additional pathways for enhanced solvent vapor transport, thus enhancing preconcentration. Enrichment using CNIM doubled compared to membranes without CNTs, while the methanol flux and mass transfer coefficients increased by 61% and 519% respectively. The carbon nanotube enhanced MD process showed excellent precision (RSD of 3-5%), linearity, and the detection limits were in the range of 0.001 to 0.009 mg L(-1) by HPLC analysis.

  16. Photo-induced flow-injection determination of nitrate in water

    Czech Academy of Sciences Publication Activity Database

    Mikuška, Pavel; Čapka, Lukáš; Večeřa, Zbyněk; Kalinichenko, I.; Kellner, J.

    2014-01-01

    Roč. 94, č. 10 (2014), s. 1038-1049 ISSN 0306-7319 Institutional support: RVO:68081715 Keywords : chemiluminescence * flow injection analysis * nitrate Subject RIV: CB - Analytical Chemistry , Separation Impact factor: 1.295, year: 2014

  17. Carbon film resistor electrode for amperometric determination of acetaminophen in pharmaceutical formulations.

    Science.gov (United States)

    Felix, Fabiana S; Brett, Christopher M A; Angnes, Lúcio

    2007-04-11

    Flow injection analysis (FIA) with amperometric detection was employed for acetaminophen quantification in pharmaceutical formulations using a carbon film resistor electrode. This sensor exhibited sharp and reproducible current peaks for acetaminophen without chemical modification of its surface. A wide linear working range (8.0x10(-7) to 5.0x10(-4) mol L(-1)) in phosphate buffer solution as well as high sensitivity (0.143 A mol(-1) L cm(-2)) and low submicromolar detection limit (1.36x10(-7) mol L(-1)) were achieved. The repeatability (R.S.D. for 10 successive injections of 5.0x10(-6) and 5.0x10(-5) mol L(-1) acetaminophen solutions) was 3.1 and 1.3%, respectively, without any memory effect between injections. The new procedure was applied to the analyses of commercial pharmaceutical products and the results were in good agreement with those obtained utilizing a spectrophotometric method. Consequently, this amperometric method has been shown to be very suitable for quality control analyses and other applications with similar requirements.

  18. Gold nanorods for surface Plasmon resonance detection of mercury (II) in flow injection analysis.

    Science.gov (United States)

    Trieu, Khang; Heider, Emily C; Brooks, Scott C; Barbosa, Fernando; Campiglia, Andres D

    2014-10-01

    This article investigates the flow injection analysis of mercury (II) ions in tap water samples via surface Plasmon resonance detection. Quantitative analysis of mercury (II) is based on the chemical interaction of metallic mercury with gold nanorods immobilized on a glass substrate. A new flow cell design is presented with the ability to accommodate the detecting substrate in the sample compartment of commercial spectrometers. Two alternatives are here considered for mercury (II) detection, namely stop-flow and continuous flow injection analysis modes. The best limit of detection (2.4 ng mL(-1)) was obtained with the continuous flow injection analysis approach. The accurate determination of mercury (II) ions in samples of unknown composition is demonstrated with a fortified tap water sample. Copyright © 2014 Elsevier B.V. All rights reserved.

  19. Automated amperometric plutonium assay system

    International Nuclear Information System (INIS)

    Burt, M.C.

    1985-01-01

    The amperometric titration for plutonium assay has been used in the nuclear industry for over twenty years and has been in routine use at the Hanford Engineering Development Laboratory since 1976 for the analysis of plutonium oxide and mixed oxide fuel material for the Fast Flux Test Facility. It has proven itself to be an accurate and reliable method. The method may be used as a direct end point titration or an excess of titrant may be added and a back titration performed to aid in determination of the end point. Due to the slowness of the PuVI-FeII reaction it is difficult to recognize when the end point is being approached and is very time consuming if the current is allowed to decay to the residual value after each titrant addition. For this reason the back titration in which the rapid FeII-CrVI reaction occurs is used by most laboratories. The back titration is performed by the addition of excess ferrous solution followed by two measured aliquots of standard dichromate with measurement of cell current after each addition

  20. Micro-flow-injection analysis (μFIA) immunoassay of herbicide residue 2,6-dichlorobenzamide

    DEFF Research Database (Denmark)

    Uthuppu, Basil; Heiskanen, Arto; Kofoed, Dan

    2015-01-01

    As a part of developing new systems for continuously monitoring the presence of pesticides in groundwater, a microfluidic amperometric immunosensor was developed for detecting the herbicide residue 2,6-dichlorobenzamide (BAM) in water. A competitive immunosorbent assay served as the sensing...... of the constructed μFIA immunosensor as an at-line monitoring system for controlling the quality of ground water supply....

  1. Mathematical modelling of a flow-injection system with a membrane separation module

    NARCIS (Netherlands)

    Kolev, S.D.; Kolev, Spas D.; van der Linden, W.E.

    1992-01-01

    A mathematical model for a flow-injection system with a membrane separation module based on the axially dispersed plug flow model was developed. It takes into account the geometrical dimensions and dispersion properties of the main sections of the manifold, the mass transfer in the channels of the

  2. Flow-injection analysis based on extraction and spectrophotometric determination of penicillins with thiazine dyes

    Czech Academy of Sciences Publication Activity Database

    Němcová, I.; Rychlovský, P.; Havelcová, Martina

    2009-01-01

    Roč. 42, č. 7 (2009), s. 989-999 ISSN 0003-2719 Institutional research plan: CEZ:AV0Z30460519 Keywords : azure A * azure B * flow-injection analysis Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 1.317, year: 2009 http://www.informaworld.com/smpp/content~db=all?content=10.1080/00032710902726088

  3. Sequential injection lab-on-valve: the third generation of flow injection analysis

    DEFF Research Database (Denmark)

    Wang, Jianhua; Hansen, Elo Harald

    2003-01-01

    Termed the third generation of flow injection analysis, sequential injection (SI)-lab-on-valve (LOV) has specific advantages and allows novel, unique applications - not least as a versatile front end to a variety of detection techniques. This review presents snd discusses progress to date of the ...

  4. Direct microcomputer controlled determination of zinc in human serum by flow injection atomic absorption spectrometry

    DEFF Research Database (Denmark)

    Simonsen, Kirsten Wiese; Nielsen, Bent; Jensen, Arne

    1986-01-01

    A procedure is described for the direct determination of zinc in human serum by fully automated, microcomputer controlled flow injection atomic absorption spectrometry (Fl-AAS). The Fl system is pumpless, using the negative pressure created by the nebuliser. It only consists of a three-way valve...

  5. Determination of uranium (IV) in cloride solutions of enrichment columns by spectrometry with flow injection

    International Nuclear Information System (INIS)

    Bastos, M.B.R.

    1988-01-01

    The utilization of Flow Injection Analysis for the U (IV) spectrophotometric determination in chloride solutions is described. The method has been shown reproducible in the range of concentrations and conditions employed with a standard deviation of about 0,3. (C.G.C.) [pt

  6. Flow injection determination of carboxylate, phosphate, and sulfhydryl compounds using metal exchange complexation.

    Science.gov (United States)

    Mansour, Fotouh R; Shafi, Mohammad A; Danielson, Neil D

    2012-06-15

    The determination of carboxylate, phosphorous, and sulfhydryl compounds has been studied using flow injection by measuring the decrease in absorbance of the Fe(III)-salicylate complex due to preferential ligand interaction with ferric ion. Targeted compounds include polycarboxylates such as sodium citrate, sodium oxalate, and EDTA, anionic phosphorous compounds such as sodium monofluoroorthophosphate, sodium trimetaphosphate, and sodium hexametaphosphate, and sulfhydryl compounds such as cysteine, glutathione, and captopril. Initial flow injection optimization has focused on citrate based on its ability to replace salicylate ion in the Fe(III)-salicylate complex causing a decrease in absorbance at 525 nm proportional to the citrate concentration. Two flow injection analysis methods are developed. In the first method, offline reaction flow injection, sodium citrate dissolved in 100 μmol L(-1) Fe-salicylate is injected in a carrier solution of 100 μmol L(-1) Fe-salicylate. The decrease in peak area is linear over a range of 1.36-109 μmol L(-1) using a flow rate of 1 mL min(-1) and an injection volume of 100 μL. The effect of pH on the Fe-salicylate complex absorbance is studied from 1 to 3.5; pH 3 shows both a high and stable complex absorbance in the visible range which provided important potential selectivity over UV detection. The limit of detection is found to be less than 57 nmol L(-1) depending on the Fe(III)-salicylate concentration used. The second method is reverse flow injection using the sample as a flowing stream in which 3 mmol L(-1) Fe(III)-salicylate is injected and the decrease in the response with increased sample concentration was monitored. The commercially available pharmaceutical product (Citroma)(®) is used to assess the accuracy and precision of the two proposed methods as compared to a reference method. Copyright © 2012 Elsevier B.V. All rights reserved.

  7. Piezoelectric detection of ion pairs between sulphonate and catecholamines for flow injection analysis of pharmaceutical preparations.

    Science.gov (United States)

    Mo, Z; Long, X; Zhang, M

    1999-03-01

    Fundamentals of ion-pair flow injection with piezoelectric detection were investigated experimentally and theoretically for the adsorption of dodecyl phenylsulfonate and interfacial ion-pair formation with epinephrine and l-dopa on silver electrode of quartz crystal microbalance. The influences of sulfonate concentration and operating parameters on the frequency response were demonstrated and provided the possibility for the discriminating determination of mixtures. The selected system of ion-pair flow injection with piezoelectric detection was applied to the determination of epinephrine and l-dopa. Calibration curves were linear in ranges 4.00-850 and 3.50-730 mug ml(-1), with detection limits of 1.22 and 1.05 mug ml(-1) and sampling frequencies of 120 samples h(-1), for epinephrine and l-dopa, respectively. The method has been satisfactorily applied to the determination of catecholamines in pharmaceutical preparations.

  8. [Determination of Flavonoids in Cycas revoluta Leaves by Chemiluminescence-Flow Injection Analysis Method].

    Science.gov (United States)

    Shi, Hong-yan; Zhu, Hai-ping; Qu, Ya-juan; Yang, Pei-jun

    2015-03-01

    To detect flavonoids from Cycas revoluta leaves by means of Chemiluminescence-Flow Injection Analysis (CL-FIA). Under alkaline condition, a CL-FIA method was established to determine flavonoids from leaves of Cycas revoluta on the basis of inhibiting effect of flavonoids to the Luminol-H2O2-Cu2+ chemiluminescence system and the reversed flow injection technique. In the range of 2. 0 x 10(-6) ~ 1. 0 x 10(-3) mg/mL, the decrease of CL intensity was correlated with flavonoids concentration while the detection limit was 0. 0265 µg/mL. Under the optimized conditions, the flavonoids of Cycas revoluta leaves were detected with its average rate reaching 1. 61% and RSD 1. 32%. Through the interference test and compared with the data of CL-FIA and UV, it is concluded that CL-FIA can be used in the analysis and detection of flavonoids from Cycas revoluta leaves.

  9. Spectrophotometric flow injection catalytic determination of molybdenum in plant digest using ion exchange resin

    International Nuclear Information System (INIS)

    Pessenda, L.C.R.

    1987-03-01

    A spectrophotometric flow injection analytical method based on the catalytic action of molybdenum on the oxidation of iodide by hydrogen peroxide in acidic medium is proposed for the molybdenum determination in plant digests. A cation exchange resin column is incorporated into a flow injection system for removal of interferents. The following system variables were investigated and optimized: reagent concentrations, sample injection volume, mixing and reaction coil lengths, temperature, sampling time, pumping rate and concentration of eluting agents. The effects of interfering species and of the acidity of samples on the molybdenum retention by the ion exchange resin column were investigated. The proposed method is characterized by good precision (r.s.d. (2.0%), a sampling rate of about 40 samples per hour, and permits the determination of molybdenum in plant digests in the range 1.0 to 40.0 μg/l. The results compare well with those obtained by graphite furnace atomic absorption spectrometry. (author) [pt

  10. Mathematical modeling of flow-injection techniques and their applications for environmental monitoring

    International Nuclear Information System (INIS)

    Begum, N.N.; Ahmed, J.

    2006-01-01

    A classification of the existing mathematical models of flow-injection (FI) manifolds based on the main principles on which they are built, have been proposed. Numerous mathematical models of FI systems employing ideas from different scientific areas (e.g. mathematical statistics, chemical engineering, chromatography) have been developed so far. The models have been compared with respect to their predictive power, the complexity of their mathematical treatment, and the requirements for computation time when applied to single-line, multi-channel and conjugated two-line FI systems. It is concluded that the axially dispersed plug flow model deserves special attention because it offers an acceptable compromise between the conflicting requirements for maximal possible mathematical simplicity and maximal possible precision. Applicability of these existing flow-injection models to single-line, multi-channel and conjugated two-line systems for environmental monitoring have been discussed. (author)

  11. Micelle-mediated methodology for the preconcentration of uranium prior to its determination by flow injection

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez Laespada, M.E.; Perez Pavon, J.L.; Moreno Cordero, B. (Univ. de Salamanca (Spain). Dept. de Quimica Analitica, Nutricion y Bromatologia)

    1993-02-01

    Cloud point extraction has been used for the preconcentration of uranium, prior to its determination by flow injection. The non-ionic surfactant employed was Triton X-114 and the reagent chosen to form a hydrophobic chelate of uranium was 1-(2-pyridylazo)-2-naphthol. The optimum conditions for the preconcentration and determination of uranium have been studied. This methodology has been applied to the determination of trace amounts of uranium in tap and river waters from Salamanca. (Author).

  12. Potentiometric electronic tongue-flow injection analysis system for the monitoring of heavy metal biosorption processes.

    Science.gov (United States)

    Wilson, D; del Valle, M; Alegret, S; Valderrama, C; Florido, A

    2012-05-15

    An automated flow injection potentiometric (FIP) system with electronic tongue detection (ET) is used for the monitoring of biosorption processes of heavy metals on vegetable wastes. Grape stalk wastes are used as biosorbent to remove Cu(2+) ions in a fixed-bed column configuration. The ET is formed by a 5-sensor array with Cu(2+) and Ca(2+)-selective electrodes and electrodes with generic response to heavy-metals, plus an artificial neural network response model of the sensor's cross-response. The real-time monitoring of both the Cu(2+) and the cation exchanged and released (Ca(2+)) in the effluent solution is performed by using flow-injection potentiometric electronic tongue system. The coupling of the electronic tongue with automation features of the flow-injection system allows us to accurately characterize the Cu(2+) ion-biosorption process, through obtaining its breakthrough curves, and the profile of the Ca(2+) ion release. In parallel, fractions of the extract solution are analysed by spectroscopic techniques in order to validate the results obtained with the reported methodology. The sorption performance of grape stalks is also evaluated by means of well-established sorption models. Copyright © 2012 Elsevier B.V. All rights reserved.

  13. Determination of uranium by an amperometric method

    International Nuclear Information System (INIS)

    John, Mary; Venkataramana, P.; Vaidyanathan, S.; Natarajan, P.R.

    1981-01-01

    An amperometric method has been standardised for the determination of uranium. Uranium is reduced to its quadrivalent state in concentrated phosphoric acid medium with ferrous iron. The excess iron is destroyed with nitric acid in presence of Mo(VI). The medium is diluted and U(IV) is titrated with standard potassium dichromate to an amperometric end point using a pair of identical plantinum wires as electrodes. The reagent volumes and uranium quantities have been scaled down to 30 ml. and 2-5 mg of uranium in the present work with a view to minimising the problems associated with recovery of plutonium. The results are quantitative with an R.S.D. of 0.2% in the present version of weight based titrations. (author)

  14. Flow-injection determination of 9,10-phenanthrenequinone with catalytic photometric detection.

    Science.gov (United States)

    Kiba, N; Suzuki, H; Goto, E; Furusawa, M

    1993-03-01

    A catalytic photometric method with a flow-injection system is described for the determination of 9,10-phenanthrenequinone. It is based on the catalytic effect of 9,10-phenanthrenequinone on the redox reaction of 1,2-dinitrobenzene with formaldehyde under alkaline conditions. 9,10-Phenanthrenequinone at the 5.0 x 10(-8)-5.0 x 10(-6)M level can be determined at a rate of 20 samples/hr. The detection limit is 1.0 x 10(-8)M (40 pg in a 10-microl injection).

  15. Flow Injection and Atomic Absorption Spectrometry - An Effective and Attractive Analytical Chemical Combination

    DEFF Research Database (Denmark)

    Hansen, Elo Harald; Nielsen, Steffen

    1998-01-01

    One of the advantages of the flow injection (FI) concept is that it is compatible with virtually all detection techniques. Being a versatile vehicle for enhancing the performance of the individual detection devices, the most spectacular results have possibly been obtained in conjunction with atomic...... for reproducible sample presentation to the AAS instrument, as a means for facilitating conversion techniques for determination of anions, for allowing on-line preconcentration procedures via incorporated column reactors or via (co)precipitation, for exploiting kinetic discrimination schemes in hydride generation...

  16. Rapid detection of milk adulteration using intact protein flow injection mass spectrometric fingerprints combined with chemometrics.

    Science.gov (United States)

    Du, Lijuan; Lu, Weiying; Cai, Zhenzhen Julia; Bao, Lei; Hartmann, Christoph; Gao, Boyan; Yu, Liangli Lucy

    2018-02-01

    Flow injection mass spectrometry (FIMS) combined with chemometrics was evaluated for rapidly detecting economically motivated adulteration (EMA) of milk. Twenty-two pure milk and thirty-five counterparts adulterated with soybean, pea, and whey protein isolates at 0.5, 1, 3, 5, and 10% (w/w) levels were analyzed. The principal component analysis (PCA), partial least-squares-discriminant analysis (PLS-DA), and support vector machine (SVM) classification models indicated that the adulterated milks could successfully be classified from the pure milks. FIMS combined with chemometrics might be an effective method to detect possible EMA in milk. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Flow injection spectrophotometric determination of low concentrations of orthosphate in natural waters employing ion exchange resin

    International Nuclear Information System (INIS)

    Pessenda, L.C.R.

    1981-01-01

    A simple and fast method for the determination of low concentrations of orthophosphate in natural waters is described. Ion exchange is incorporated into a flow injection system by usina a resin column in the sample loop of a proportion injector. Effects of sample aspiration rate, sampling time, eluting agent concentration, pumping rate of the sample carrier stream and interfaces, were investigated both using 32 PO 3- 4 or 31 PO 3- 4 with columns coupled to a gerger-muller detector and incorporated in a flow system with molybdenum blue colorinetry. (M.A.C.) [pt

  18. The potentials of the third generation of flow injection analysis for nutrient monitoring and fractionation analysis

    DEFF Research Database (Denmark)

    Miró, Manuel; Hansen, Elo Harald; Buanuam, Janya

    2006-01-01

    In the present communication, the third generation of flow injection analysis, the so-called micro sequential-injection Laboratory-on-Valve (μSI-LOV), is presented as a miniaturized, automated approach for on-line monitoring of nutrients in different environmental compartments as effected under...... enclosed and strictly controlled conditions. Special emphasis is placed on coupling μSI-LOV on-line with a recently developed microcolumn to perform dynamic fractionation schemes for ascertaining the availability of phosphorous forms in solid substrates for biota uptake under simulated environmental...

  19. [Determination of mercury in Boletus impolitus by flow injection-atomic absorption spectrometry].

    Science.gov (United States)

    Li, Tao; Wang, Yuan-Zhong

    2008-04-01

    Various test conditions and effect factors for the determination of mercury by flow injection-atomic absorption spectrometry were discussed, and a method for the determination of mercury in Boletus impolitus has been developed. The linear range for mercury is 0-60 microg x L(-1). The relative standard deviation is less than 3.0%, and the recovery is 96%-107%. This method is simple, rapid and has been applied to the determination of mercury in Boletus impolitus samples with satisfactory results.

  20. The determination of uranium(VI) by flow-injection analysis

    International Nuclear Information System (INIS)

    Jones, E.A.

    1985-01-01

    A method is described for the direct determination of uranium(VI) in waste waters and acid leach liquors by use of a flow-injection procedure and spectrophotometric measurement with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (bromo-PADAP). The interference effects of several commonly occurring elements were studied. The calibration curve is linear over concentrations of uranium(VI) from 0,5 to 20 mg/1, and the precision obtained on a synthetic leach liquor was 0,019 (relative standard deviation). The procedure is rapid and convenient, and up to 40 samples can be analysed in an hour

  1. Spectrophotometric determination of phosphorus in iron alloys employing a flow injection system

    OpenAIRE

    Gervasio,Ana P. G.; Miranda,Carlos E. S.; Luca,Gilmara C.; Tumang,Cristiane A.; Campos,Luis F. P.; Reis,Boaventura F.

    2001-01-01

    A flow-injection procedure for spectrophotometric determination of phosphorus in electrolytic iron and iron alloys is proposed. The method is based on the ammonium molybdate reaction followed by stannous chloride reduction in acidic medium. In order to circumvent the severe interference caused by the major constituents such as Fe(III) and Cr(III), a mini-column packed with AG50W-X8 resin was coupled to the manifold. A sample throughput of 40 determinations per hour, a dynamical range from P 0...

  2. Flow-injection spectrophotometric determination of palladium with DCS-arsenazo

    Energy Technology Data Exchange (ETDEWEB)

    Xing-Cun He (Guangxi Normal University, Guilin (China). Department of Chemistry); Ya-Qi Cai (Beijing Agricultural University (China). Department of Soil Chemistry); Zhi-De Hu (Lanzhou Univ., GS (China). Dept. of Chemistry)

    1992-01-15

    A flow-injection spectrophotometric method for the determination of palladium involves the measurement of the absorbance of the palladium complex with DCS-arsenazo at 635 nm. The calibration graph is linear over the range 0-8.0 {mu}g ml{sup -1}. The detection limit is 0.05 {mu}g ml{sup -1}. The sample throughput is 90 h{sup -1} with 100-{mu}l sample injections. The proposed method has been applied to the determination of palladium in metallurgical samples without preliminary simulation. (author). 7 refs.; 2 figs.; 3 tabs.

  3. Flow Injection and Atomic Absorption Spectrometry - An Effective and Attractive Analytical Chemical Combination

    DEFF Research Database (Denmark)

    Hansen, Elo Harald; Nielsen, Steffen

    1998-01-01

    One of the advantages of the flow injection (FI) concept is that it is compatible with virtually all detection techniques. Being a versatile vehicle for enhancing the performance of the individual detection devices, the most spectacular results have possibly been obtained in conjunction with atomic...... absorption spectrometry (AAS). Initially with flame-AAS (FAAS) procedures, later for hydride generation (HG) techniques, and most recently in combination with electrothermal AAS (ETAAS). The common denominator for all these procedures is the inherently precise and strictly reproducible timing that the sample...

  4. Direct determination of sodium and potassium in blood serum by flow injection and atomic absorption spectrophotometry

    International Nuclear Information System (INIS)

    Burguera, J.L.; Burguera, M.; Gallignani, M.

    1983-01-01

    A simple and reliable method for the measurement of sodium and potassium in blood serum without any sample dilution by using flow injection and atomic absorption spectrophotometry is described. A sample throughout of 100 measurements per hour is possible. The coefficient of variation for within-run determination was about 1,14 and 2,36% for sodium and potassium, respectively, in serum samples (n=10). The method is easily adaptable to pediatric research, because of the low required sample volume of 5ul. (Author) [pt

  5. Amperometric biosensor for the detection of hydrogen peroxide using catalase modified electrodes in polyacrylamide.

    Science.gov (United States)

    Varma, Shailly; Mattiasson, Bo

    2005-09-23

    A simple biosensor for the detection of hydrogen peroxide in organic solvents has been developed and coupled to a flow injection analysis (FIA) system. Catalase was entrapped in polyacrylamide gel and placed on the surface of platinum (working electrode) fixed in a Teflon holder with Ag-wire (auxiliary electrode), followed by addition of filter paper soaked in KCl. The entrapped catalase gel was held on the electrode using membranes. The effects of cellulose and polytetrafluroethylene (PTFE) membranes on the electrode response towards hydrogen peroxide have been studied. The modified electrode has been used to study the detection of hydrogen peroxide in solvents like water, dimethyl sulfoxide (DMSO), and 1,4-dioxane using amperometric techniques like cyclic voltammetry (CV) and FIA. The CV of modified catalase electrode showed a broad oxidation peak at -150 mV and a clear reduction peak at -212 mV in the presence of hydrogen peroxide. Comparison of CV with hydrogen peroxide in various solvents has been carried out. The electrode showed an irreversible kinetics with DMSO as the solvent. A flow cell has been designed in order to carry on FIA studies to obtain calibration plots for hydrogen peroxide with the modified electrode. The calibration plots in several solvents such as water, dimethyl sulfoxide, 1,4-dioxane have been obtained. The throughput of the enzyme electrode was 10 injections per hour. Due to the presence of membrane the response time of the electrode is concentration dependent.

  6. Amperometric detector for gas chromatography based on a silica sol-gel solid electrolyte.

    Science.gov (United States)

    Steinecker, William H; Miecznikowski, Krzysztof; Kulesza, Pawel J; Sandlin, Zechariah D; Cox, James A

    2017-11-01

    An electrochemical cell comprising a silica sol-gel solid electrolyte, a working electrode that protrudes into a gas phase, and reference and counter electrodes that contact the solid electrolyte comprises an amperometric detector for gas chromatography. Under potentiostatic conditions, a current related to the concentration of an analyte in the gas phase is produced by its oxidation at the three-phase boundary among the sol-gel, working electrode, and the gas phase. The sol-gel is processed to contain an electrolyte that also serves as a humidistat to maintain a constant water activity even in the presence the gas chromatographic mobile phase. Response was demonstrated toward a diverse set of analytes, namely hydrogen, 1,2-ethandithiol, phenol, p-cresol, and thioanisole. Using flow injection amperometry of hydrogen with He as the carrier gas, 90% of the steady-state current was achieved in < 1s at a flow rate of 20mLmin -1 . A separation of 1,2-ethandithiol, phenol, p-cresol, and thioanisole at a 2.2mLmin -1 flow rate was achieved with respective detection limits (k = 3 criterion) of 4, 1, 3, and 70 ppmv when the working electrode potential was 800mV. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Computer-controlled flow injection analysis system for on-line determination of distribution ratios

    International Nuclear Information System (INIS)

    Nekimken, H.L.; Smith, B.F.; Jarvinen, G.D.; Peterson, E.J.; Jones, M.M.

    1988-01-01

    An automated flow injection analysis (FIA) system has been developed for the rapid acquisition of liquid/liquid, metal ion distribution ratios (D). The system features automatic switching between aqueous metal sample and wash solutions, on-line solvent extraction, phase separation, and the simultaneous detection of the separated phases by diode-array spectrophotometry. A comparative study of manual, single-stage liquid/liquid extractions with the flow injection system was completed by using a new extraction system UO 2 2+ /benzene/TOPO (trioctylphosphine oxide)/HBMPPT (4-benzoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-thione). The batch and FIA methods yielded results generally within 5% of each other. The major differences between the two systems are that the FIA system is at least twice as fast, is less labor intensive, is more reproducible, and yields better statistics (a result of the FIA's speed and automation features). Slope analysis of the plotted data from the uranyl extraction studies indicates that the extraction complex is UO 2 (BMPPT) 2 (TOPO)

  8. Dispersion-convolution model for simulating peaks in a flow injection system.

    Science.gov (United States)

    Pai, Su-Cheng; Lai, Yee-Hwong; Chiao, Ling-Yun; Yu, Tiing

    2007-01-12

    A dispersion-convolution model is proposed for simulating peak shapes in a single-line flow injection system. It is based on the assumption that an injected sample plug is expanded due to a "bulk" dispersion mechanism along the length coordinate, and that after traveling over a distance or a period of time, the sample zone will develop into a Gaussian-like distribution. This spatial pattern is further transformed to a temporal coordinate by a convolution process, and finally a temporal peak image is generated. The feasibility of the proposed model has been examined by experiments with various coil lengths, sample sizes and pumping rates. An empirical dispersion coefficient (D*) can be estimated by using the observed peak position, height and area (tp*, h* and At*) from a recorder. An empirical temporal shift (Phi*) can be further approximated by Phi*=D*/u2, which becomes an important parameter in the restoration of experimental peaks. Also, the dispersion coefficient can be expressed as a second-order polynomial function of the pumping rate Q, for which D*(Q)=delta0+delta1Q+delta2Q2. The optimal dispersion occurs at a pumping rate of Qopt=sqrt[delta0/delta2]. This explains the interesting "Nike-swoosh" relationship between the peak height and pumping rate. The excellent coherence of theoretical and experimental peak shapes confirms that the temporal distortion effect is the dominating reason to explain the peak asymmetry in flow injection analysis.

  9. O-(β-hydroxyethylrutosides determination by micellar flow injection (FI-spectrofluorimetry

    Directory of Open Access Journals (Sweden)

    Cecilia Mariana Peralta

    2014-12-01

    Full Text Available A simple, eco-friendly, sensitive and economic flow injection spectrofluorimetric method was developed for the determination of O-(β-hydroxyethylrutosides. The procedure was based on the use of an anionic surfactant such as sodium dodecyl sulfate to provide an appreciable O-(β-hydroxyethylrutosides fluorescence enhancement, increasing considerably the sensitivity of detection. All the variables affecting the fluorescence intensity were studied and optimized. The flow rate was 5 mL/min with detection at 450 nm (after excitation at 346 nm. A linear correlation between drug amount and peak area was established for O-(β-hydroxyethylrutosides in the range of 0.01–200 µg/mL with a detection limit of 0.001 µg/mL (s/n=3. Validation processes were performed by recovering studies with satisfactory results. The new methodology can be employed for the routine analysis of O-(β-hydroxyethylrutosides in bulks as well as in commercial formulations. Keywords: O-(β-hydroxyethylrutosides, Micellar enhancement, Flow injection, Spectrofluorimetry, Pharmaceuticals

  10. Mathematical modelling of two-analyte sequential determinations by flow-injection sandwich-techniques

    International Nuclear Information System (INIS)

    Montesinos, J.L.; Poch, M.; Alonso, J.; Valle, M. del; Lima, J.L.F.C.

    1991-01-01

    Results obtained in the evaluation of a mathematical model for flow-injection sandwich systems, in which the sample is inserted between two different carrier solutions with the aid of an eight-way injection valve, are presented. The model considers the system as a tubular reactor with axially dispersed plug flow, where chemical kinetics have been included. Only a minimum of parameters are needed for the model: the dispersion coefficients, which are obtained from experimental correlations for the different hydrodynamic conditions, and the rate constants, which are determined by univariate optimization. The behaviour of the model, when applied to the case of one analyte and one reagent, was evaluated for the enzymatic determinations of glucose and glycerol. The case of two analytes determined with two reagents was also studied in the combined determination of glucose and glycerol. Experimental profiles were compared with the simulated peaks and showed good agreement. (author). 20 refs.; 11 figs.; 2 tabs

  11. DEVELOPMENT OF FLOW INJECTION METHOD FOR ONLINE DETERMINATION OF THIOCYANATE BASED ON OXIDATION BY PERMANGANATE

    Directory of Open Access Journals (Sweden)

    Hermin Sulistyarti

    2010-07-01

    Full Text Available The importance of developing method for thiocyanate becomes obvious, because thiocyanate can inhibit iodine uptake of thyroid gland leading to mumps disease. In this work, thiocyanate is oxidized by permanganate in the acid donor stream to cyanide, which is directly converted to hydrogen cyanide. Then, hydrogen cyanide diffuses through a Teflon membrane into acceptor stream containing nickel(II in ammoniacal buffer to form tetracyanonickelate(II which is detected spectrophotometrically at 267 nm. Analytical figures of merit were linear up to 50 mg L-1 for thiocyanate, with RSD of 1.34%, and detection limit of 0.07 mg L-1, respectively. Interfering anions were eliminated under stoichiometric amount of permanganate and sample throughput was 20 h-1. The method was validated for determining thiocyanate samples from synthetic and gold process waters with satisfactory results.   Keywords: Thiocyanate, flow injection, permanganate, spectrophotometry

  12. Chemiluminescence determination of ultramicro DNA with a flow-injection method

    International Nuclear Information System (INIS)

    Chen Hui; Zhou Min; Jin Xiaoyong; Song Yumin; Zhang Ziyu; Ma Yongjun

    2002-01-01

    A high sensitive flow-injection chemiluminescence method for determination of calf thymus DNA and herring sperm DNA has been developed. The method is based on the chemiluminescence reaction of Rhodamine B-cerium(IV)-thermally denatured DNAs in sulfuric acid media. The proposed procedure allows quantitation of DNAs in the range 2.6x10 -5 to 0.26 μg ml -1 for calf thymus DNA and 5.0x10 -8 to 5.0x10 -5 μg ml -1 for herring sperm DNA with correlation coefficients 0.9998 and 0.9996 (both n=11), respectively. The detection limits (3σ) are 6.5x10 -6 μg ml -1 for calf thymus DNA and 4.3x10 -8 μg ml -1 for herring sperm DNA. The possible mechanism of chemiluminescence in the system is discussed

  13. Comparison of Uric Acid Quantity with Different Food in Human Urine by Flow Injection Chemiluminescence Analysis

    Directory of Open Access Journals (Sweden)

    Jiajia Wang

    2013-01-01

    Full Text Available Based on the inhibitory effect of uric acid (UA on luminol-Co2+ chemiluminescence (CL system, a sensitive method for the determination of UA at nanomolar level by flow injection (FI CL was proposed. The proposed method was successfully applied to real-time monitoring of UA excretion in human 24 h urine with different food intake, showing that meats, vegetables, and porridge intake caused differential UA excretions of 879, 798, and 742 mg, respectively. It was also found that UA concentrations in urine under the three kinds of food intake simultaneously reached maximum at 2 h after meals with the values of 417, 318, and 288 μg mL−1, respectively. The UA concentration in human serum was also determined by this approach, and the possible mechanism of luminol-Co2+-UA CL reaction was discussed in detail.

  14. "Reagentless" flow injection determination of ammonia and urea using membrane separation and solid phase basification

    Science.gov (United States)

    Akse, J. R.; Thompson, J. O.; Sauer, R. L.; Atwater, J. E.

    1998-01-01

    Flow injection analysis instrumentation and methodology for the determination of ammonia and ammonium ions in an aqueous solution are described. Using in-line solid phase basification beds containing crystalline media. the speciation of ammoniacal nitrogen is shifted toward the un-ionized form. which diffuses in the gas phase across a hydrophobic microporous hollow fiber membrane into a pure-water-containing analytical stream. The two streams flow in a countercurrent configuration on opposite sides of the membrane. The neutral pH of the analytical stream promotes the formation of ammonium cations, which are detected using specific conductance. The methodology provides a lower limit of detection of 10 microgram/L and a dynamic concentration range spanning three orders of magnitude using a 315-microliters sample injection volume. Using immobilized urease to enzymatically promote the hydrolysis of urea to produce ammonia and carbon dioxide, the technique has been extended to the determination of urea.

  15. Determination of hydrogen peroxide in reactor moderator solutions by flow injection analysis

    Energy Technology Data Exchange (ETDEWEB)

    Whitaker, M.J.

    1991-12-31

    A flow injection analysis (FIA) method for the determination of hydrogen peroxide in reactor moderator water was developed and installed at the Savannah River Site (SRS) Water Quality Laboratory. The technique has an analytical range of 0.10 to 2.50 ppm (ug/mL) with a sampling rate of 40 samples per hour. The calibration curve is linear with a correlation coefficient of 0.999, and the precision is excellent with relative standard deviations at the 0.50% level for both 0.10 and 2.50 ppm standards. When the automated FIA procedure is compared to the manual method it demonstrates a twenty minute reduction in analysis time per sample, and the total liquid waste generated per sample analyzed is reduced by roughly 95 mL. 6 refs., 10 figs., 6 tabs.

  16. Determination of hydrogen peroxide in reactor moderator solutions by flow injection analysis

    Energy Technology Data Exchange (ETDEWEB)

    Whitaker, M.J.

    1991-01-01

    A flow injection analysis (FIA) method for the determination of hydrogen peroxide in reactor moderator water was developed and installed at the Savannah River Site (SRS) Water Quality Laboratory. The technique has an analytical range of 0.10 to 2.50 ppm (ug/mL) with a sampling rate of 40 samples per hour. The calibration curve is linear with a correlation coefficient of 0.999, and the precision is excellent with relative standard deviations at the 0.50% level for both 0.10 and 2.50 ppm standards. When the automated FIA procedure is compared to the manual method it demonstrates a twenty minute reduction in analysis time per sample, and the total liquid waste generated per sample analyzed is reduced by roughly 95 mL. 6 refs., 10 figs., 6 tabs.

  17. Flow injection fluorescence determination of dopamine using a photo induced electron transfer (PET) boronic acid derivative

    International Nuclear Information System (INIS)

    Ebru Seckin, Z.; Volkan, Muervet

    2005-01-01

    An automated flow injection analysis system was developed for the fluorometric determination of dopamine in pharmaceutical injections. The method is based on the quenching effect of dopamine on m-dansylaminophenyl boronic acid (DAPB) fluorescence due to the reverse photo induced electron transfer (PET) mechanism. Effects of pH and interfering species on the determination of dopamine were examined. Calibration for dopamine, based on quenching data, was linear in the concentration range of 1.0 x 10 -5 to 1.0 x 10 -4 M. Detection limit (3 s) of the method was found to be 3.7 x 10 -6 M. Relative standard deviation of 1.2% (n = 10) was obtained with 1.0 x 10 -5 M dopamine standard solution. The proposed method was applied successfully for the determination of dopamine in pharmaceutical injection sample. The sampling rate was determined as 24 samples per hour

  18. Filterless preconcentration, flow injection analysis and detection by inductively-coupled plasma mass spectrometry

    DEFF Research Database (Denmark)

    Andersen, Jens Enevold Thaulov

    The influence of interferences in the analysis of elements by inductively-coupled-plasma mass-spectrometry (ICP-MS) may be significantly diminished by utilising a protocol of flow-injection analysis (FIA). The method is based on filterless preconcentration of metallic elements at the walls...... of a knotted reactor that was made of nylon tubings. In the load mode, the preconcentration was accomplished by precipitation of metallic species in alkaline-buffered carriers onto the inner walls of the hydrofilic tube. After a preconcen-tration period of 40-120 seconds using sample volumes of 4-10 m...... of 10-30 were obtained in the analysis of aluminium, of chromium and of iron, which resulted in detection limits (3) down to 20 g/L at a sampling frequency of 50 per hour. The preconcentration protocol improves the selectivity thus allowing direct determination of the elements in saline media. Anionic...

  19. Method for 236U Determination in Seawater Using Flow Injection Extraction Chromatography and Accelerator Mass Spectrometry

    DEFF Research Database (Denmark)

    Qiao, Jixin; Hou, Xiaolin; Steier, Peter

    2015-01-01

    An automated analytical method implemented in a flow injection (FI) system was developed for rapid determination of 236U in 10 L seawater samples. 238U was used as a chemical yield tracer for the whole procedure, in which extraction chromatography (UTEVA) was exploited to purify uranium, after...... experimental parameters affecting the analytical effectiveness were investigated and optimized in order to achieve high chemical yields and simple and rapid analysis as well as low procedure background. Besides, the operational conditions for the target preparation prior to the AMS measurement were optimized......, on the basis of studying the coprecipitation behavior of uranium with iron hydroxide. The analytical results indicate that the developed method is simple and robust, providing satisfactory chemical yields (80−100%) and high analysis speed (4 h/sample), which could be an appealing alternative to conventional...

  20. Irreversibility analysis of magneto-hydrodynamic nanofluid flow injected through a rotary disk

    Directory of Open Access Journals (Sweden)

    Rashidi Mohammad Mehdi

    2015-01-01

    Full Text Available The non-linear Navier-Stokes equations governed on the nanofluid flow injected through a rotary porous disk in the presence of an external uniform vertical magnetic field can be changed to a system of non-linear partial differential equations by applying similar parameter. In this study, partial differential equations are analytically solved by the modified differential transform method, Pade differential transformation method to obtain self-similar functions of motion and temperature. A very good agreement is observed between the obtained results of Pade differential transformation method and those of previously published ones. Then it has become possible to do a comprehensive parametric analysis on the entropy generation in this case to demonstrate the effects of physical flow parameters such as magnetic interaction parameter, injection parameter, nanoparticle volume fraction, dimensionless temperature difference, rotational Brinkman number and the type of nanofluid on the problem.

  1. Are Flow Injection-based Approaches Suitable for Automated Handling of Solid Samples?

    DEFF Research Database (Denmark)

    Miró, Manuel; Hansen, Elo Harald; Cerdà, Victor

    Flow-based approaches were originally conceived for liquid-phase analysis, implying that constituents in solid samples generally had to be transferred into the liquid state, via appropriate batch pretreatment procedures, prior to analysis. Yet, in recent years, much effort has been focused...... electrolytic or aqueous leaching, on-line dialysis/microdialysis, in-line filtration, and pervaporation-based procedures have been successfully implemented in continuous flow/flow injection systems. In this communication, the new generation of flow analysis, including sequential injection, multicommutated flow...... with the potential hyphenation with modern analytical instrumentation for automated monitoring of the content of targeted species in the on-line generated extracts [3,4]. [1] Z.-L. Zhi, A. Ríos, M. Valcárcel, Crit. Rev. Anal. Chem., 26 (1996) 239. [2] M. Miró, E.H. Hansen, R. Chomchoei, W. Frenzel, TRAC-Trends Anal...

  2. Carbon paste and PVC electrodes for the flow injection potentiometric determination of dextromethorphan.

    Science.gov (United States)

    Khaled, Elmorsy; Hassan, H N A; Mohamed, Gehad G; Seleim, A A

    2010-04-15

    The construction and performance characteristics of dextromethorphan (DXM) carbon paste (CPEs) and polyvinyl chloride (PVC) electrodes are described. Different modes for electrode modification, including incorporation of ion pairs (IPs), ion pairing agent or soaking the plain electrode in IPs suspension, have been used. Matrices compositions were optimized referring to the effect of modifier and plasticizer. The fabricated electrodes work satisfactorily in the concentration range from 10(-5) to 10(-2) mol L(-1) with fast response time (1.6s) and long operational lifetime (2 months). The developed electrodes have been successfully applied for the potentiometric determination of DXM in pharmaceutical formulation under batch and flow injection analysis (FIA) conditions. Under FIA conditions, the proposed electrodes allow the analysis of 90 samples h(-1) and offer the advantage of simplicity, accuracy and automation feasibility. The solubility products of various DXM-IPs were determined conductometrically. (c) 2010 Elsevier B.V. All rights reserved.

  3. Bienzymatic Biosensor for Rapid Detection of Aspartame by Flow Injection Analysis

    Directory of Open Access Journals (Sweden)

    Maria-Cristina Radulescu

    2014-01-01

    Full Text Available A rapid, simple and stable biosensor for aspartame detection was developed. Alcohol oxidase (AOX, carboxyl esterase (CaE and bovine serum albumin (BSA were immobilised with glutaraldehyde (GA onto screen-printed electrodes modified with cobalt-phthalocyanine (CoPC. The biosensor response was fast. The sample throughput using a flow injection analysis (FIA system was 40 h−1 with an RSD of 2.7%. The detection limits for both batch and FIA measurements were 0.1 µM for methanol and 0.2 µM for aspartame, respectively. The enzymatic biosensor was successfully applied for aspartame determination in different sample matrices/commercial products (liquid and solid samples without any pre-treatment step prior to measurement.

  4. Spectrophotometric determination of uranium and thorium with arsenazo III in the flow injection system

    International Nuclear Information System (INIS)

    Andrade, M. das G.M. de.

    1986-12-01

    A simple system for flow injection analysis (FIA) with double confluence was built using a filter photocolorimeter, an analogic potentiometer, 'plexiglass' flow cuvettes, polyethylene colls and tubes, 'plexiglass' commuter and peristaltic pump to introduce solutions and gravity as flow source. The system was dimensioned and studied using only Arsenazo III solutions. Spectrophotometric methods for uranium and thorium using Arsenazo III were studied using a scanning spectrophotometer and after chosing adequate red filter, adapted to photocolorimetry using flow cuvettes and FIA. Synthetic samples, phosphate rock, and process samples from uranium recovery of dolomites were analysed. Rocks of Morro do Ferro (MG, Brazil), Caldasite (Baddeleyte + Zirconite), Zirconite, Monazite from a program for certification and certified rocks (Dunite DC-1, CANMET) were analysed without chemical separation of Th (IV) and with ion exchange separation in semi-micro columns of cation exchange resin (Dowex 50). (Author) [pt

  5. Mathematical modelling of two-analyte sequential determinations by flow-injection sandwich-techniques

    Energy Technology Data Exchange (ETDEWEB)

    Montesinos, J.L.; Poch, M. (Universitat Autonoma de Barcelona (Spain). Departament de Quimica, Unitat d' Enginyera Quimica); Alonso, J.; Valle, M. del (Universitat Autonoma de Barcelona (Spain). Departament de Quimica, Unitat de Quimica Analitica); Lima, J.L.F.C. (Universidade de Porto (Portugal). Faculdade de Farmacia, Departamento de Quimica Fisica)

    1991-11-20

    Results obtained in the evaluation of a mathematical model for flow-injection sandwich systems, in which the sample is inserted between two different carrier solutions with the aid of an eight-way injection valve, are presented. The model considers the system as a tubular reactor with axially dispersed plug flow, where chemical kinetics have been included. Only a minimum of parameters are needed for the model: the dispersion coefficients, which are obtained from experimental correlations for the different hydrodynamic conditions, and the rate constants, which are determined by univariate optimization. The behaviour of the model, when applied to the case of one analyte and one reagent, was evaluated for the enzymatic determinations of glucose and glycerol. The case of two analytes determined with two reagents was also studied in the combined determination of glucose and glycerol. Experimental profiles were compared with the simulated peaks and showed good agreement. (author). 20 refs.; 11 figs.; 2 tabs.

  6. Optimized and validated flow-injection spectrophotometric analysis of topiramate, piracetam and levetiracetam in pharmaceutical formulations.

    Science.gov (United States)

    Hadad, Ghada M; Abdel-Salam, Randa A; Emara, Samy

    2011-12-01

    Application of a sensitive and rapid flow injection analysis (FIA) method for determination of topiramate, piracetam, and levetiracetam in pharmaceutical formulations has been investigated. The method is based on the reaction with ortho-phtalaldehyde and 2-mercaptoethanol in a basic buffer and measurement of absorbance at 295 nm under flow conditions. Variables affecting the determination such as sample injection volume, pH, ionic strength, reagent concentrations, flow rate of reagent and other FIA parameters were optimized to produce the most sensitive and reproducible results using a quarter-fraction factorial design, for five factors at two levels. Also, the method has been optimized and fully validated in terms of linearity and range, limit of detection and quantitation, precision, selectivity and accuracy. The method was successfully applied to the analysis of pharmaceutical preparations.

  7. Flow Injection Analysis of 5-(Hydroxymethyl)-2-furaldehyde in Honey by a Modified Winkler Method.

    Science.gov (United States)

    Castoldi, Karine; Milani, Maria Izabel; Rossini, Eduardo L; Pezza, Leonardo; Pezza, Helena R

    2016-01-01

    One of the quality indicators for honey is 5-(hydroxymethyl)-2-furaldehyde (HMF), which is formed during the heating or aging of honey. The International Honey Commission recommends three methods for the determination of HMF in honey: the Winkler method, the White method, and determination by HPLC. The Winkler method uses the carcinogenic substance p-toluidine, which is not in accordance with the principles of Green Chemistry. The present work describes the determination of HMF in honey by flow injection analysis (FIA) using a modified Winkler method, replacing p-toluidine with p-aminobenzoic acid. The linear range was 1.00 to 40.0 mg L(-1), the limit of detection (LOD) was 0.43 mg L(-1), and the limit of quantification (LOQ) was 1.32 mg L(-1). The method is an efficient and environmentally friendly technique for the analysis of HMF in honey.

  8. Use of flow injection mass spectrometric fingerprinting and chemometrics for differentiation of three black cohosh species

    International Nuclear Information System (INIS)

    Huang, Huilian; Sun, Jianghao; McCoy, Joe-Ann; Zhong, Haiyan; Fletcher, Edward J.; Harnly, James; Chen, Pei

    2015-01-01

    Flow injection mass spectrometry (FIMS) was used to provide chemical fingerprints of black cohosh (Actaea racemosa L.) in a manner of minutes by omitting the separation step. This method has proven to be a powerful tool for botanical authentication and in this study it was used to distinguish between three Actaea species prior to a more detailed chemical analysis using ultra high-performance liquid chromatography high-resolution mass spectrometry (UHPLC–HRMS). Black cohosh has become increasingly popular as a dietary supplement in the United States for the treatment of symptoms related to menopause. However, it has been known to be adulterated with the Asian Actaea dahurica (Turcz. ex Fisch. & C.A.Mey.) Franch. species (syn. Cimicifuga dahurica (Turcz.) Maxim). Existing methods for identification of black cohosh and differentiation of Actaea species are usually lengthy, laborious, and lack robustness, often based on the comparison of a few pre-selected components. Chemical fingerprints were obtained for 77 black cohosh samples and their related species using FIMS in the negative ion mode. The analysis time for each sample was less than 2 min. All data were processed using principal component analysis (PCA). FIMS fingerprints could readily differentiate all three species. Representative samples from each of the three species were further examined using UHPLC–MS to provide detailed profiles of the chemical differences between the three species and were compared to the PCA loadings. This study demonstrates a simple, fast, and easy analytical method that can be used to differentiate A. racemosa, Actaea podocarpa, and A. dahurica. - Highlights: • Flow injection mass spectrometry (FIMS) was used to provide chemical fingerprints of black cohosh (Actaea racemosa L.) in a manner of minutes by omitting the separation step. • FIMS can discriminate between A. dahurica, A. podocarpa, and A. racemosa. • FIMS is a valuable screening tool for authentication of botanicals

  9. Use of flow injection mass spectrometric fingerprinting and chemometrics for differentiation of three black cohosh species

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Huilian [Food Composition and Methods Development Laboratory, Beltsville Human Nutrition Research Center, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD (United States); Key Laboratory of Modern Preparation of TCM, Jiangxi University of Traditional Chinese Medicine, Ministry of Education, Nanchang, Jiangxi Province (China); Sun, Jianghao [Food Composition and Methods Development Laboratory, Beltsville Human Nutrition Research Center, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD (United States); McCoy, Joe-Ann [The North Carolina Arboretum Germplasm Repository, UNC Affiliate Campus, Asheville, NC (United States); Zhong, Haiyan [College of Food Science and Engineering, Central South University of Forestry and Technology, Changsha, Hunan Province (China); Fletcher, Edward J. [Strategic Sourcing, Inc., Banner Elk, NC 28604 (United States); Harnly, James, E-mail: harnly.james@ars.usda.gov [Food Composition and Methods Development Laboratory, Beltsville Human Nutrition Research Center, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD (United States); Chen, Pei, E-mail: pei.chen@ars.usda.gov [Food Composition and Methods Development Laboratory, Beltsville Human Nutrition Research Center, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD (United States)

    2015-03-01

    Flow injection mass spectrometry (FIMS) was used to provide chemical fingerprints of black cohosh (Actaea racemosa L.) in a manner of minutes by omitting the separation step. This method has proven to be a powerful tool for botanical authentication and in this study it was used to distinguish between three Actaea species prior to a more detailed chemical analysis using ultra high-performance liquid chromatography high-resolution mass spectrometry (UHPLC–HRMS). Black cohosh has become increasingly popular as a dietary supplement in the United States for the treatment of symptoms related to menopause. However, it has been known to be adulterated with the Asian Actaea dahurica (Turcz. ex Fisch. & C.A.Mey.) Franch. species (syn. Cimicifuga dahurica (Turcz.) Maxim). Existing methods for identification of black cohosh and differentiation of Actaea species are usually lengthy, laborious, and lack robustness, often based on the comparison of a few pre-selected components. Chemical fingerprints were obtained for 77 black cohosh samples and their related species using FIMS in the negative ion mode. The analysis time for each sample was less than 2 min. All data were processed using principal component analysis (PCA). FIMS fingerprints could readily differentiate all three species. Representative samples from each of the three species were further examined using UHPLC–MS to provide detailed profiles of the chemical differences between the three species and were compared to the PCA loadings. This study demonstrates a simple, fast, and easy analytical method that can be used to differentiate A. racemosa, Actaea podocarpa, and A. dahurica. - Highlights: • Flow injection mass spectrometry (FIMS) was used to provide chemical fingerprints of black cohosh (Actaea racemosa L.) in a manner of minutes by omitting the separation step. • FIMS can discriminate between A. dahurica, A. podocarpa, and A. racemosa. • FIMS is a valuable screening tool for authentication of botanicals.

  10. Espectrofotometria de zinco em fertilizantes em fluxo Flow injection spectrophotometry of zinc in mineral fertilizers

    Directory of Open Access Journals (Sweden)

    Arnaldo Antonio Rodella

    1999-07-01

    Full Text Available Um sistema de análise química por injeção em fluxo é proposto para a determinação espectrofotométrica de zinco em amostras de misturas de fertilizantes minerais, empregando-se zincon como reagente cromogênico. O procedimento analítico envolve redução de íons metálicos por ácido ascórbico, complexação com íon cianeto, seguindo-se a descomplexação seletiva do zinco com formaldeído, liberando-o para que reaja com o zincon formando um complexo azul. A aplicação do método proposto à extratos de mistura de fertilizantes indicou que a ação de interferentes pode ser contornada e que resultados comparáveis aos da espectrometria de absorção atômica são obtidos.A flow injection system for zinc analysis in mineral fertilizer mixtures is proposed using zincon as chromogenic reagent. The effect of interfering ions such as Cu2+, Fe3+, Mn2+ was eliminated by reduction (using ascorbic acid and complexation of these metal íons with cyanide, with zinc included. Zinc is allowed to react with zincon only after the destruction of the zinc cyano complex with formaldehyde. Flow injection analysis permitted efficient control of the reaction time so that only the zinc ion is set free to produce a blue complex with zincon. Zinc was determined in 16 fertilizer mixtures (3 replicates with precision and accuracy comparable to atomic absorption spectrometry.

  11. Current Trends in Nanomaterial-Based Amperometric Biosensors

    Directory of Open Access Journals (Sweden)

    Akhtar Hayat

    2014-12-01

    Full Text Available The last decade has witnessed an intensive research effort in the field of electrochemical sensors, with a particular focus on the design of amperometric biosensors for diverse analytical applications. In this context, nanomaterial integration in the construction of amperometric biosensors may constitute one of the most exciting approaches. The attractive properties of nanomaterials have paved the way for the design of a wide variety of biosensors based on various electrochemical detection methods to enhance the analytical characteristics. However, most of these nanostructured materials are not explored in the design of amperometric biosensors. This review aims to provide insight into the diverse properties of nanomaterials that can be possibly explored in the construction of amperometric biosensors.

  12. Amperometric noise at thin film band electrodes.

    Science.gov (United States)

    Larsen, Simon T; Heien, Michael L; Taboryski, Rafael

    2012-09-18

    Background current noise is often a significant limitation when using constant-potential amperometry for biosensor application such as amperometric recordings of transmitter release from single cells through exocytosis. In this paper, we fabricated thin-film electrodes of gold and conductive polymers and measured the current noise in physiological buffer solution for a wide range of different electrode areas. The noise measurements could be modeled by an analytical expression, representing the electrochemical cell as a resistor and capacitor in series. The studies revealed three domains; for electrodes with low capacitance, the amplifier noise dominated, for electrodes with large capacitances, the noise from the resistance of the electrochemical cell was dominant, while in the intermediate region, the current noise scaled with electrode capacitance. The experimental results and the model presented here can be used for choosing an electrode material and dimensions and when designing chip-based devices for low-noise current measurements.

  13. Band-type microelectrodes for amperometric immunoassays

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ga-Yeon; Chang, Young Wook; Ko, Hyuk [Department of Materials Science and Engineering, Yonsei University, 134 Shinchon-dong, Seodaemun-gu, Seoul, 120-749 (Korea, Republic of); Kang, Min-Jung [Korea Institute of Science and Technology (KIST), Seoul (Korea, Republic of); Pyun, Jae-Chul, E-mail: jcpyun@yonsei.ac.kr [Department of Materials Science and Engineering, Yonsei University, 134 Shinchon-dong, Seodaemun-gu, Seoul, 120-749 (Korea, Republic of)

    2016-07-20

    A band-type microelectrode was made using a parylene-N film as a passivation layer. A circular-type, mm-scale electrode with the same diameter as the band-type microelectrode was also made with an electrode area that was 5000 times larger than the band-type microelectrode. By comparing the amperometric signals of 3,5,3′,5′-tetramethylbenzidine (TMB) samples at different optical density (OD) values, the band-type microelectrode was determined to be 9 times more sensitive than the circular-type electrode. The properties of the circular-type and the band-type electrodes (e.g., the shape of their cyclic voltammograms, the type of diffusion layer used, and the diffusion layer thickness per unit electrode area) were characterized according to their electrode area using the COMSOL Multiphysics software. From these simulations, the band-type electrode was estimated to have the conventional microelectrode properties, even when the electrode area was 100 times larger than a conventional circular-type electrode. These results show that both the geometry and the area of an electrode can influence the properties of the electrode. Finally, amperometric analysis based on a band-type electrode was applied to commercial ELISA kits to analyze human hepatitis B surface antigen (hHBsAg) and human immunodeficiency virus (HIV) antibodies. - Highlights: • A band-type microelectrode was made using a parylene-N film as a passivation layer. • The band-type microelectrode was 14-times more sensitive than circular-type electrode. • The influence of geometry on microelectrode properties was simulated using COMSOL. • The band-type electrode was applied to ELISA kits for hHBsAg and hHIV-antibodies.

  14. Enhancement of peroxyoxalate chemiluminescence by copper (II) in flow-injection analysis: optimization by factorial design analysis.

    NARCIS (Netherlands)

    Steijger, O.M.; den Nieuwenboer, H.C.M.; Lingeman, H.; Brinkman, U.A.T.; Holthuis, J.J.M.; Smilde, A.K.

    1996-01-01

    A flow injection analysis (FIA) system with peroxyoxalate chemiluminescence (CL) detection was optimized by factorial design analysis in the absence and presence of Cu(II) ions. The carrier stream was a mixture of acetonitrile and an aqueous imidazole solution of pH 7.0. The effect of the metal ions

  15. Comparison of Flow Injection MS, NMR, and DNA Sequencing: Methods for Identification and Authentication of Black Cohosh (Actaea racemosa)

    Science.gov (United States)

    Flow injection mass spectrometry (FIMS) and proton nuclear magnetic resonance spectrometry (1H-NMR), two metabolic fingerprinting methods, and DNA sequencing were used to identify and authenticate Actaea species. Initially, samples of Actaea racemosa L. from a single source were distinguished from ...

  16. Mass spectrometric confirmation criterion for product-ion spectra generated in flow-injection analysis. Environmental application

    NARCIS (Netherlands)

    Geerdink, R.B.; Niessen, W.M.A.; Brinkman, U.A.T.

    2001-01-01

    The suitability of a confirmation criterion recently recommended in the Netherlands for gas chromatography with mass spectrometric detection (GC-MS), was evaluated for flow-injection analysis (FIA) with atmospheric pressure chemical ionisation MS-MS detection. The main feature of the criterion is

  17. How Flow Injection Analysis (FIA) over the past 25 years has changed our way of performing chemical analyses

    DEFF Research Database (Denmark)

    Hansen, Elo Harald; Miró, Manuel

    2007-01-01

    Briefly looking back on the impact of flow injection analysis (FIA), as reflected in the rapid growth of publications in the scientific literature, and touching upon many of the novel and unique analytical chemical possibilities that FIA and its sequels, sequential injection analysis (SIA) and La...

  18. Trends and perspectives of flow injection/sequential injection on-line sample-pretreatment schemes coupled to ETAAS

    DEFF Research Database (Denmark)

    Wang, Jianhua; Hansen, Elo Harald

    2005-01-01

    Flow injection (FI) analysis, the first generation of this technique, became in the 1990s supplemented by its second generation, sequential injection (SI), and most recently by the third generation (i.e.,Lab-on-Valve). The dominant role played by FI in automatic, on-line, sample pretreatments in ...

  19. Speciation of mercury in fish samples by flow injection catalytic cold vapour atomic absorption spectrometry

    International Nuclear Information System (INIS)

    Zhang Yanlin; Adeloju, Samuel B.

    2012-01-01

    Highlights: ► Successful speciation of inorganic and organic Hg with Fe 3+ , Cu 2+ and thiourea as catalysts. ► Best sensitivity enhancement and similar sensitivity for MeHg and Hg 2+ with Fe 3+ . ► Successful use of Hg 2+ as the primary standard for quantification of inorganic and total-Hg. ► Quantitative extraction of Hg and MeHg with 2 M HCl which contained thiourea. ► Integration with FIA for rapid analysis with a sample throughput of 180 h −1 . - Abstract: A rapid flow injection catalytic cold vapour atomic absorption spectrometric (FI-CCV-AAS) method is described for speciation and determination of mercury in biological samples. Varying concentrations of NaBH 4 were employed for mercury vapour generation from inorganic and mixture of inorganic and organic (total) Hg. The presence of Fe 3+ , Cu 2+ and thiourea had catalytic effect on mercury vapour generation from methylmercury (MeHg) and, when together, Cu 2+ and thiourea had synergistic catalytic effect on the vapour generation. Of the two metal ions, Fe 3+ gave the best sensitivity enhancement, achieving the same sensitivity for MeHg and inorganic Hg 2+ . Due to similarity of resulting sensitivity, Hg 2+ was used successfully as a primary standard for quantification of inorganic and total Hg. The catalysis was homogeneous in nature, and it was assumed that the breaking of the C-Hg bond was facilitated by the delocalization of the 5d electron pairs in Hg atom. The extraction of MeHg and inorganic mercury (In-Hg) in fish samples were achieved quantitatively with hydrochloric acid in the presence of thiourea and determined by FI-CCV-AAS. The application of the method to the quantification of mercury species in a fish liver reference material DOLT-4 gave 91.5% and 102.3% recoveries for total and methyl mercury, respectively. The use of flow injection enabled rapid analysis with a sample throughput of 180 h −1 .

  20. Review of recent applications of flow injection spectrophotometry to pharmaceutical analysis

    International Nuclear Information System (INIS)

    Tzanavaras, Paraskevas D.; Themelis, Demetrius G.

    2007-01-01

    Pharmaceutical analysis is one of the most important fields in analytical chemistry. The discovery of new drugs and the on-going update of international regulations for the safety and efficacy of pharmaceutical formulations demand the continuous development of new analytical methods. Inevitably, automation plays an important role, especially when a lot of samples have to be analyzed in the minimum of time. The present study reviews the applications of flow injection (FI) spectrophotometry to the determination of active pharmaceutical ingredients (APIs) in their respective formulations. However, the topic covered in this study is important not only to pharmaceutical analytical scientists. The principles, figures of merit and 'chemistry' of the presented methods can be of interest to bio-analytical and clinical chemists as well for the analysis of biological samples, to environmental analysts that study the up-to-date demand of the determination of the fate of pharmaceuticals in the environment and even to toxicologists and forensic scientists. This review covers scientific contributions published later than 2000. A variety of FI procedures based on homogeneous (direct UV measurements, colour-forming reactions, metal-drug interactions) and heterogeneous (optical sensors and solid-phase reactors) systems are discussed. A third section covers on-line sample pretreatment (solid-phase extraction, liquid-liquid extraction, on-line digestion, etc.)

  1. Flow-injection chemiluminescence determination of diazepam by oxidation with N-bromosuccinimide.

    Science.gov (United States)

    Han, Suqin; Jia, Shize; Guo, Liang

    2013-01-01

    A rapid and sensitive flow-injection chemiluminescence (FI-CL) method is described for the determination of diazepam based on its reaction with N-bromosuccinimide (NBS) in alkaline medium in the presence of dichlorofluorescein (DCF) as an effective energy-transfer agent. Under optimum conditions, the proposed method allowed the measurement of diazepam over the range of 2.0 × 10(-6) to 2.0 × 10(-4) mol/L with a detection limit of 5.0 × 10(-7) mol/L. The relative standard deviation for 11 parallel measurements of 2.0 × 10(-5) mol/L diazepam was 2.1%. The method was applied satisfactorily for the determination of diazepam in pharmaceutical preparations, and the results agree well with those obtained by spectrophotometry. The use of the proposed system for the determination of diazepam in urine and plasma samples was also tested. The possible mechanism of the chemiluminescence reaction is discussed briefly. Copyright © 2012 John Wiley & Sons, Ltd.

  2. Investigation of the Effect of Pipeline Size on the Cross Flow Injection Process

    Directory of Open Access Journals (Sweden)

    M. Elashmawy

    2016-06-01

    Full Text Available Injection pumps constitute an essential component for many industrial applications. The main focus of this study is to predict the effect of the size of the pipeline on the cross flow injection process. A test-rig was designed, built and equipped with three different pipelines, 1½", ¾" and ½" diameters. Comparison was made under constant line pressure of 40-bar and line flow rate of 5 liter/min, with a fixed injection pump rotational speed of 100 rpm. The main parameter tested was the injection dose capacity at different pump displacements. Cross flow mixing process is also theoretically studied using 3D-CFD analysis to show the injection cross flow behavior for the same geometry and parameters used for experimental test. Results show that increasing the size of the pipeline increases injection pump doses ability. This effect is insignificant at lower injection pump displacements, while the effect of the size of the pipeline becomes dominant when increasing the displacement. By changing the size of the pipeline from ½" to 1½" diameter injection pump dose capacity increases by 3.24% at 100% pump displacement. Selecting larger pipe sizes for injection ports is recommended whenever possible.

  3. Determination of sulfate in the wet-process of phosphoric acid by reverse flow injection

    Directory of Open Access Journals (Sweden)

    Wenhui Shi

    2014-01-01

    Full Text Available An improved method based on reverse flow injection is proposed for determining sulfate concentration in the wet-process of phosphoric acid (WPA. The effect of reagent composition, flow rate, temperature, acid concentration, length of the reaction coil, and linear response range on the flow system is discussed in detail. Optimal conditions are established for determining sulfate in the WPA samples. Baseline drift is avoided by a periodic washing step with EDTA in an alkaline medium. A linear response is observed within a range of 20 - 360 mg L-1, given by the equation A = 0.0020C (mg L-1 + 0.0300, R² = 0.9991. The detection limit of the proposed method for sulfate analysis is 3 mg L-1, and the relative standard deviation (n = 12 of sulfate absorbance peak is less than 1.60%. This method has a rate of up to 29 samples per hour, and the results compare well with those obtained with gravimetric method.

  4. Flow injection determination of lead and cadmium in hair samples from workers exposed to welding fumes

    Energy Technology Data Exchange (ETDEWEB)

    Cespon-Romero, R.M. [Department of Analytical Chemistry, Nutrition and Bromatology, Faculty of Chemistry, University of Santiago de Compostela, 15782-Santiago de Compostela (Spain); Yebra-Biurrun, M.C. [Department of Analytical Chemistry, Nutrition and Bromatology, Faculty of Chemistry, University of Santiago de Compostela, 15782-Santiago de Compostela (Spain)], E-mail: qncayebi@usc.es

    2007-09-26

    A flow injection procedure involving continuous acid leaching for lead and cadmium determination in hair samples of persons in permanent contact with a polluted workplace environment by flame atomic absorption spectrometry is proposed. Variables such as sonication time, nature and concentration of the acid solution used as leaching solution, leaching temperature, flow-rate of the continuous manifold, leaching solution volume and hair particle size were simultaneously studied by applying a Plackett-Burman design approach. Results showed that nitric acid concentration (leaching solution), leaching temperature and sonication time were statistically significant variables (confidence interval of 95%). These last two variables were finally optimised by using a central composite design. The proposed procedure allowed the determination of cadmium and lead with limits of detection 0.1 and 1.0 {mu}g g{sup -1}, respectively. The accuracy of the developed procedure was evaluated by the analysis of a certified reference material (CRM 397, human hair, from the BCR). The proposed method was applied with satisfactory results to the determination of Cd and Pb in human hair samples of workers exposed to welding fumes.

  5. Chemiluminescence determination of ultramicro DNA with a flow-injection method

    Energy Technology Data Exchange (ETDEWEB)

    Chen Hui; Zhou Min; Jin Xiaoyong; Song Yumin; Zhang Ziyu; Ma Yongjun

    2002-02-12

    A high sensitive flow-injection chemiluminescence method for determination of calf thymus DNA and herring sperm DNA has been developed. The method is based on the chemiluminescence reaction of Rhodamine B-cerium(IV)-thermally denatured DNAs in sulfuric acid media. The proposed procedure allows quantitation of DNAs in the range 2.6x10{sup -5} to 0.26 {mu}g ml{sup -1} for calf thymus DNA and 5.0x10{sup -8} to 5.0x10{sup -5} {mu}g ml{sup -1} for herring sperm DNA with correlation coefficients 0.9998 and 0.9996 (both n=11), respectively. The detection limits (3{sigma}) are 6.5x10{sup -6} {mu}g ml{sup -1} for calf thymus DNA and 4.3x10{sup -8} {mu}g ml{sup -1} for herring sperm DNA. The possible mechanism of chemiluminescence in the system is discussed.

  6. Screen-printed sensor for batch and flow injection potentiometric chromium(VI) monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez-Moreno, Raul A.; Gismera, M.J.; Sevilla, M.T.; Procopio, Jesus R. [Facultad de Ciencias, Universidad Autonoma de Madrid, Departamento de Quimica Analitica y Analisis Instrumental, Madrid (Spain)

    2010-05-15

    A disposable screen-printed electrode was designed and evaluated for direct detection of chromium(VI) in batch and flow analysis. The carbon screen-printed electrode was modified with a graphite-epoxy composite. The optimal graphite-epoxy matrix contains 37.5% graphite powder, 12.5% diphenylcarbohydrazide, a selective compound for chromium(VI), and 50% epoxy resin. The principal analytical parameters of the potentiometric response in batch and flow analysis were optimized and calculated. The screen-printed sensor exhibits a response time of 20 {+-} 1 s. In flow analysis, the analytical frequency of sampling is 70 injections per hour using 0.1 M NaNO{sub 3} solution at pH 3 as the carrier, a flow rate of 2.5 mL.min{sup -1}, and an injection sample volume of 0.50 mL. The sensor shows potentiometric responses that are very selective for chromium(VI) ions and optimal detection limits in both static mode (2.1 x 10{sup -7} M) and online analysis (9.4 x 10{sup -7} M). The disposable potentiometric sensor was employed to determine toxicity levels of chromium(VI) in mineral, tap, and river waters by flow-injection potentiometry and batch potentiometry. Chromium(VI) determination was also carried out with successful results in leachates from municipal solid waste landfills. (orig.)

  7. Determination of ammonia in beers by pervaporation flow injection analysis and spectrophotometric detection.

    Science.gov (United States)

    Wang, Lijuan; Cardwell, Terence J; Cattrall, Robert W; Luque de Castro, Maria D; Kolev, Spas D

    2003-08-29

    A pervaporation flow injection (PFI) method is described for the determination of ammonia in beers. After injecting the sample into a NaOH donor solution, ammonia and other volatiles are transferred in the pervaporation unit from the donor stream to an acceptor stream containing sodium salicylate and nitroprusside, which subsequently mixes with alkaline sodium dichloroisocyanurate to allow the classical Berthelot reaction to take place. The blue-coloured complex formed is monitored spectrophotometrically at 655 nm. A linear calibration curve with a range of 0.1-40 mg l(-1) was obtained. The method has a detection limit of 0.05 mg l(-1) and is capable of a sampling frequency of 11 h(-1) at 4 mg l(-1) ammonia. It was applied successfully to the determination of ammonia in synthetic samples and unfiltered lager beers. The advantages of the present method over the ammonia ion-selective electrode method and the PFI system based on mixed indicator detection are discussed.

  8. Flow injection spectrophotometry using natural reagent from Morinda citrifolia root for determination of aluminium in tea.

    Science.gov (United States)

    Tontrong, Sopa; Khonyoung, Supada; Jakmunee, Jaroon

    2012-05-01

    A flow injection (FI) spectrophotometric method with using natural reagent extracted from Morinda citrifolia root has been developed for determination of aluminium. The extract contained anthraquinone compounds which could react with Al(3+) to form reddish complexes which had maximum absorption wavelength at 499.0nm. The extract could be used as a reagent in FI system without further purification to obtain pure compound. A sensitive method for determination of aluminium in concentration range of 0.1-1.0mgL(-1), with detection limit of 0.05mgL(-1) was achieved. Relative standard deviations of 1.2% and 1.7% were obtained for the determination of 0.1 and 0.6mgL(-1) Al(3+) (n=11). Sample throughput of 35h(-1) was achieved with the consumption of 3mL each of carrier and reagent solutions per injection. The developed method was successfully applied to tea samples, validated by the FAAS standard method. The method is simple, fast, economical and could be classified as a greener analytical method. Copyright © 2011 Elsevier Ltd. All rights reserved.

  9. Gas diffusion-flow injection determination of total inorganic carbon in water using tungsten oxide electrode.

    Science.gov (United States)

    Monser, L; Adhoum, N; Sadok, S

    2004-02-06

    A novel gas diffusion-flow injection method has been developed for the rapid and sensitive determination of total inorganic carbon (TIC) in water. The method is based on the diffusion of CO(2) across gas permeable membrane from a donor stream containing 0.1M HCl to an acceptor stream of sodium acetate (10(-5)moll(-1) and pH 10). The CO(2) trapped in the acceptor stream passes through an electrochemical flow cell contains a tungsten oxide wire and a silver/silver chloride electrode, where it was sensitively detected. The parameters affecting the sensitivity of the electrode such as buffer concentration, pH, flow rate and injected volume were studied in detail. The electrode response was linear in the concentration range from 5 to 100mugml(-1) CO(3)(2-) with a correlation coefficient (R(2)) of 0.998. Precision (R.S.D.) was 1.42% for 20mugml(-1) standard solution of CO(3)(2-) (n=10). The detection limit was 0.20mugml(-1) CO(3)(2-). The method was evaluated by the injection of real natural water samples and an average recovery of 100.1% was obtained. The sampling rate was 30 samplesh(-1). The method is simple, feasible with satisfactory accuracy and precision and thus could be used for monitoring TIC in water.

  10. Indirect flow-injection spectrophotometric determination of meloxicam, tenoxicam and piroxicam in pharmaceutical formulations.

    Science.gov (United States)

    Al-Momani, Idrees F

    2006-12-01

    A simple and sensitive indirect spectrophotometric method for the assay of meloxicam (MX), tenoxicam (TX) and piroxicam (PX) in pure and in pharmaceutical formulations by flow injection analysis (FIA) has been proposed. The method is based on the oxidation of these drugs by a known excess of N-bromosuccinimide (NBS) in an acidic medium, followed by a reaction of excess oxidant with chloranilic acid (CAA) to bleach its purple color. The absorbance values increased linearly with increasing concentrations of the drugs. Variables, such as the acidity, reagent concentrations, flow rate of reagents and other FI parameters were optimized to produce the most sensitive and reproducible results. The system obeyed Beer's low over concentration ranges of 10 - 160, 20 - 200 and 10 - 160 microg/ml for MX, TX and PX, respectively. The common excipients and additives did not interfere with their determinations. The method was successfully applied to the determinations of MX, TX and PX in various pharmaceutical preparations. The results obtained by the proposed method were found to be in good agreement with those found by the official HPLC methods.

  11. Evaluation of Antibacterial Enrofloxacin in Eggs by Matrix Solid Phase Dispersion-Flow Injection Chemiluminescence

    Directory of Open Access Journals (Sweden)

    Xiaocui Duan

    2014-01-01

    Full Text Available The study based on the chemiluminescence (CL reaction of potassium ferricyanide and luminol in sodium hydroxide medium, enrofloxacin (ENRO could dramatically enhance CL intensities and incorporated with matrix solid-phase dispersion (MSPD technique (Florisil used as dispersant, dichloromethane eluted the target compounds. A simple flow injection chemiluminescence (FL-CL method with MSPD technique for determination of ENRO in eggs was described. Under optimal conditions, the CL intensities were linearly related to ENRO concentration ranging from 4.0×10-8 g.L−1 to 5.0×10-5 g.L−1, with a correlation coefficient of 0.9989 and detection limit of 5.0×10-9 g.L−1. The relative standard deviation was 3.6% at an ENRO concentration of 2.0×10-6 g.L−1. Our testing technique can help ensure food safety, and thus, protect public health.

  12. Total polyphenols content in white wines on a microfluidic flow injection analyzer with embedded optical fibers.

    Science.gov (United States)

    Oscar, Sandoval-Ventura; Fernando, Olguín-Contreras Luis; Del Pilar, Cañizares-Macías María

    2017-04-15

    Absorbance detection in food microdevices has not been thoroughly used due to low levels of sensitivity in measurements. Thus, it is necessary to develop microfluidic methods for improving photometric detection. For this purpose, a simple coupled-optical-fiber-polydimethylsiloxane (PDMS) microdevice was developed, to quantify polyphenols content in white wine employing the Folin-Ciocalteu reaction method. A 6V and 10W halogen lamp with an optical path length of 7mm between optical fibers, which were placed into the microchip, using guides at the outlet of the flow, increased the level of sensitivity during detection. The linear range was from 0.03mmol/L to 0.18mmol/L. Thus, the corresponding equation was: Abs=4.00(±0.16) [tannic acid]+0.17(±0.017). Intra-laboratory repeatability and reproducibility percentages were 2.95% and 6.84%, respectively. Such results were compared to those obtained from applying the conventional flow-injection analysis method, based on the same type of reaction. The relative error between methods was less than 13%. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. Automated multiple flow-injection analysis in clinical chemistry: determination of total protein with Biuret reagent.

    Science.gov (United States)

    Shideler, C E; Stewart, K K; Crump, J; Wills, M R; Savory, J; Renoe, B W

    1980-09-01

    We have examined the feasibility of the automated multiple flow-injection technique for application to clinical chemistry by adapting to this system the biuret method for the determination of total protein. Samples were discretely and rapidly introduced into a continuously flowing, nonsegmented reagent stream by means of an automatic sampler and high-pressure injection valve. Pumps operating at 1380-2070 kPa (200-300 psi) were utilized to introduce the biuret reagent and saline diluent into the system separately at flow rates of 72 and 47 microL/s, respectively. Use of 20-microL sample and a 3.0-s reaction-delay coil was adequately sensitive for analysis for total protein by this method. Samples were analyzed at a rate of 150/h with no detectable between-sample carryover. Within-run precision studies yielded relative standard deviations of 2.5% and less. Total protein values obtained by this method correlated well with those obtained by centrifugal analyzer and bubble-segmented continuous-flow biuret methods.

  14. Flow-injection chemiluminescence method for the determination of naphazoline hydrochloride and oxymetazoline hydrochloride.

    Science.gov (United States)

    Wang, Nan-Nan; Shao, Yan-Qing; Tang, Yu-Hai; Yin, He-Ping; Wu, Xiao-Zhong

    2009-01-01

    A sensitive and simple flow-injection chemiluminescence (FI-CL) method, which was based on the CL intensity generated from the redoxreaction of potassium permanganate (KMnO4)-formaldehyde in vitriol (H2SO4) medium, has been developed, validated and applied for the determination of naphazoline hydrochloride and oxymetazoline hydrochloride. Besides oxidants and sensitizers, the effect of the concentration of H(2)SO(4), KMnO4 and formaldehyde was investigated. Under the optimum conditions, the linear range was 1.0 x 10(-2)-7.0 mg/L for naphazoline hydrochloride and 5.0 x 10(-2)-10.0 mg/L for oxymetazoline hydrochloride. During seven repeated inter-day and intra-day precision tests of 0.1, 1.0 and 10.0 mg/L samples, the relative standard deviations all corresponded to reference values. The detection limit was 8.69 x 10(-3) mg/L for naphazoline hydrochloride and 3.47 x 10(-2) mg/L for oxymetazoline hydrochloride (signal-to-noise ratio oxymetazoline hydrochloride in pharmaceuticals.

  15. [Research on optimization of mathematical model of flow injection-hydride generation-atomic fluorescence spectrometry].

    Science.gov (United States)

    Cui, Jian; Zhao, Xue-Hong; Wang, Yan; Xiao, Ya-Bing; Jiang, Xue-Hui; Dai, Li

    2014-01-01

    Flow injection-hydride generation-atomic fluorescence spectrometry was a widely used method in the industries of health, environmental, geological and metallurgical fields for the merit of high sensitivity, wide measurement range and fast analytical speed. However, optimization of this method was too difficult as there exist so many parameters affecting the sensitivity and broadening. Generally, the optimal conditions were sought through several experiments. The present paper proposed a mathematical model between the parameters and sensitivity/broadening coefficients using the law of conservation of mass according to the characteristics of hydride chemical reaction and the composition of the system, which was proved to be accurate as comparing the theoretical simulation and experimental results through the test of arsanilic acid standard solution. Finally, this paper has put a relation map between the parameters and sensitivity/broadening coefficients, and summarized that GLS volume, carrier solution flow rate and sample loop volume were the most factors affecting sensitivity and broadening coefficients. Optimizing these three factors with this relation map, the relative sensitivity was advanced by 2.9 times and relative broadening was reduced by 0.76 times. This model can provide a theoretical guidance for the optimization of the experimental conditions.

  16. Novel PVC-membrane electrode for flow injection potentiometric determination of Biperiden in pharmaceutical preparations.

    Science.gov (United States)

    Khaled, Elmorsy; El-Sabbagh, Inas A; El-Kholy, N G; Ghahni, E Y Abdel

    2011-12-15

    The construction and performance characteristics of Biperiden (BP) polyvinyl chloride (PVC) electrodes are described. Different methods for electrode fabrication are tested including; incorporation of BP-ion pairs (BP-IPs), incorporation of ion pairing agents, or soaking the plain electrode in BP-ion pairs suspension solution. Electrode matrices were optimized referring to the effect of modifier content and nature, plasticizer and the method of modification. The proposed electrodes work satisfactorily in the BP concentration range from 10(-5) to 10(-2)mol L(-1), with fast response time (7s) and adequate operational lifetime (28 days). The electrode potential is pH independent within the range 2.0-7.0, with good selectivity towards BP in presence of various interfering species. The developed electrodes have been applied for potentiometric determination of BP in pharmaceutical formulation under batch and flow injection analysis (FIA) conditions. FIA offers the advantages of accuracy and automation feasibility with high sampling frequency. The dissolution profile for Akineton tablets (2mg BP/tablet) was studied using the proposed electrode in comparison with the official methods. Copyright © 2011 Elsevier B.V. All rights reserved.

  17. Trace and ultratrace analysis methods for the determination of phosphorus by flow-injection techniques.

    Science.gov (United States)

    Motomizu, Shoji; Li, Zhen-Hai

    2005-04-15

    Trace (phosphorus determination by flow-injection analysis are reviewed. Most of the methods cited in this review are fundamentally based on the reaction of orthophosphate with molybdate to form heteropoly acids, such as molybdenum yellow and molybdenum blue, and some of the methods are based on the formation of such secondary reactions as ion associates and their aggregates with bulky cations, such as cationic dyes and quaternary ammonium ions. The heteropoly acids themselves can be measured by spectrophotometry, and the ion associate formed with a cationic dye, Malachite Green (MG), can be measured based on the coloration of MG. Light scattering detection methods can be used for measuring the aggregates of ion associates formed with bulky cations. Highly sensitive detection of phosphorus can be accomplished by fluorophotometry; Rhodamine B (RB) and its analogues react with molybdophosphate to form ion associates, which shows fluorescence quenching of RB: LOD is about 5 nM. The detection method based on the chemiluminescence of luminal oxidized with molybdophosphoric acids is probably the most sensitive of all the detection methods reported so far: LOD of the method is as low as 1nM. The LOD of the molybdenum blue method can be improved by using a liquid core waveguide: LOD is 0.5 nM.

  18. Spectrophotometric determination of phosphorus in iron alloys employing a flow injection system

    Directory of Open Access Journals (Sweden)

    Gervasio Ana P. G.

    2001-01-01

    Full Text Available A flow-injection procedure for spectrophotometric determination of phosphorus in electrolytic iron and iron alloys is proposed. The method is based on the ammonium molybdate reaction followed by stannous chloride reduction in acidic medium. In order to circumvent the severe interference caused by the major constituents such as Fe(III and Cr(III, a mini-column packed with AG50W-X8 resin was coupled to the manifold. A sample throughput of 40 determinations per hour, a dynamical range from P 0.25 to 6.00 mg L-1, a reagent consumption of 25 mg ammonium molybdate and 2 mg stannous chloride per determination, and a relative standard deviation < 1% (n = 10 for a typical sample with 2.20 mg L-1 P were achieved. Three different types of samples were used to evaluate system performance. Accuracy was assessed by comparing the results with certified values and no significant difference at 95 % confidence level was observed.

  19. Highly selective determination of phenolphthalein by flow injection chemiluminescence method based on a molecular imprinting polymer.

    Science.gov (United States)

    Yu, Jinghua; Ge, Lei; Dai, Ping; Zhang, Congcong; Ge, Shenguang; Huang, Jiadong

    2009-01-01

    The phenolphthalein-imprinted polymer was prepared with methacrylic acid as functional monomer and ethylene glycol dimethacrylate as cross-linker. Taking advantage of the quenching effect of phenolphthalein on the potassium permanganate-HCl-anhydrous alcohol chemiluminescence system, a new model was established to determine phenolphthalein by a highly selective flow injection chemiluminescence method. The traditional flow-though cell was replaced with a novel flow path using a Y-shaped polymethyl methacrylate column, through which the three reactants were injected simultaneously. The linear range of this assay was from 1.0 x 10(-8) to 1.0 x 10(-6) g/mL (r = 0.9978). The limit of detection was 8.9 x 10(-9) g/mL. The relative standard deviation for the determination of 1.0 x 10(-8) g/mL phenolphthalein solution was below 2.9% (n = 11). The proposed method was applied to the determination of phenolphthalein in real samples with satisfactory results.

  20. Batch and flow-injection methods for the spectrophotometric determination of olanzapine

    Energy Technology Data Exchange (ETDEWEB)

    Jasinska, A.; Nalewajko, E

    2004-04-22

    An indirect batch spectrophotometric and direct flow-injection (FI) visible spectrophotometric methods have been developed for the determination of the novel anti-psychotic drug olanzapine (OLA). The batch method is based on the oxidation of olanzapine by a known excess of potassium hexacyanoferrate(III) in the presence of the mixture of sulphuric and phosphoric acids (1:1 (v/v)). The absorbance of unreacted oxidant is measured at 425 nm. The absorbance decreases linearly with increasing concentration of the assayed drug. The FI method with detection at 540 nm is based on the direct oxidation of olanzapine one of two oxidants, cerium(IV) sulphate or potassium hexacyanoferrate(III) in acidic medium. The calibration graph were linear over the range of 2.5-40 {mu}g ml{sup -1} in the batch method and 0.05-300 and 0.5-250 {mu}g ml{sup -1} in the FI methods, used cerium (IV) sulphate and potassium hexacyanoferrate (III) respectively. Both FI methods gave similar results in terms of precision and accuracy. The relative standard deviation (R.S.D.), was <1%. The accuracy, obtained from recovery experiments, was 97.9-99.4%. The batch method gave slightly higher R.S.D. values (up to 2.3%) and lower values of accuracy (the recovery was between 96.5 and 96.6%). The methods developed were applied to the determination of olanzapine in a pharmaceutical product.

  1. Flow injection chemiluminescence determination of loxoprofen and naproxen with the acidic permanganate-sulfite system

    Directory of Open Access Journals (Sweden)

    Li-Juan Wang

    2011-02-01

    Full Text Available A novel flow injection chemiluminescence (CL method for the determination of loxoprofen and naproxen was proposed based on the CL system of KMnO4, and Na2SO3 in acid media. The CL intensity of KMnO4-Na2SO3 was greatly enhaneed in the presence of loxoprofen and naproxen. The mechanism of the CL reaction was studied by the kinetic proecss and UV-vis absorption and the conditions were optimized. Under optimized conditions, the CL intensity was linear with loxoprofen and naproxen concentration in the range of 7.0 × 10−8 – 1.0 × 10−5 g/mL and 2.0 × 10−7 – 4.0 × 10−6 g/mL with the detection limit of 2.0 × 10−8 g/mL and 3.0 × 10−8 g/mL (S/N = 3, respectively. Thc relative standard deviations were 2.39% and 1.37% for 5.0 × 10−7 g/mL naproxen and 5.0 × 10−7 g/mL loxoprofen (n = 10, respectively. The proposed method was satisfactorily applied to thc determination of loxoprofen and naproxen in pharmaceutical preparations. Keywords: chemiluminescence, KMnO4, loxoprofen, naproxen

  2. Pharmacokinetic of pseudoephedrine in rat serum with luminol-pepsin chemiluminescence system by flow injection analysis.

    Science.gov (United States)

    Luo, Kai; Li, Yajuan; Zheng, Xiaohui; Song, Zhenghua

    2015-02-01

    Pepsin (Pep) accelerated the electron transferring rate of excited 3-aminophathlate and enhanced luminol-dissolved oxygen chemiluminescence (CL) intensity, and the flow injection (FI) luminol-Pep CL system was first developed. It was found that the CL intensity of luminol-Pep reaction could be remarkably inhibited by pseudoephedrine (PE); the decrement of CL intensity was linear to the logarithm of PE concentration in the range of 0.1∼100.0 nmol L(-1) with a detection limit of 0.03 nmol mL(-1) (3σ). At a flow rate of 2.0 mL min(-1), the complete process including washing and sampling was performed within 40 s, offering a sample throughput of 90 h(-1). This proposed method was successfully applied to determining PE in rat serum for 18 h after intragastric administration with the elimination ratio of 42.34 % and recoveries from 90.3 to 110.6 %. The pharmacokinetic results showed that PE could be rapidly absorbed into serum with peak concentration (C max) of 1.45 ± 0.18 g L(-1) at the time (T max) of 1.49 ± 0.02 h; the absorption half-life (0.35 ± 0.04 h), elimination half-life (1.86 ± 0.24 h), the area under curve (109.81 ± 6.03 mg L(-1) h(-1)), mean residence time (3.82 ± 0.27 h), and elimination rate constant (2.26 ± 0.23 L g(-1) h(-1)) in rats vivo were derived, respectively. The possible CL mechanism of luminol-Pep-PE reaction was discussed by FI-CL, fluorescence, and molecular docking (MD) methods.

  3. Flow injection assessment of nitrate contents in fresh and cooked fruits and vegetables grown in Fiji.

    Science.gov (United States)

    Prasad, Surendra; Chetty, Adrian A

    2011-10-01

    Nitrates form part of the essential chemistry of soils and plants. Thus, plant roots are able to absorb nitrate directly from the soil. It has been discovered that human nitrate intake is mainly from vegetables. Vegetables play an important role in human nutrition since they are an outstanding source for vitamins, minerals, and biologically active compounds. In risk assessment of nitrate contents, this study reports the nitrate levels of 8 commonly consumed fruits and vegetables grown in Fiji, tomato (Lycopersicon esculentum), eggplant (Solanum melongena), capsicum (Capsicum annuum var. grossum), breadfruit (Artocarpus altilis), long bean (Vigna sesquipedalis), jackfruit (A. heterophyllus), pumpkin (Cucurbita pepo), and cucumber (Cucumis sativus). The effects of different types of cooking methods, baking, boiling, and frying, have also been studied. The validated flow injection analysis technique has been used to quantify the nitrate-N levels in the chosen products following nitrate extraction using the activated carbon technique. The mean values of nitrate levels in fresh products ranged from 25.83 to 281.02 mg NO(3) (-) kg(-1) . The study shows that boiling reduced nitrate contents by 65.37% to 25.25%. The frying in soy bean oil elevated nitrate contents from 354.79% to 86.69%, but after baking, nitrate contents remained almost constant with slight increasing trend in the case of tomato (19.97%). The nitrate levels published in the literature for the same types of fruits and vegetables studied have also been reviewed and compared. The average nitrate-N values were comparable or lower than overseas data, but did not present unpredictably high values, that is, they were below the risk level. © 2011 Institute of Food Technologists®

  4. Development of nanobody-based flow injection chemiluminescence immunoassay for sensitive detection of human prealbumin.

    Science.gov (United States)

    Ma, Lei; Sun, Yanyan; Kang, Xuejun; Wan, Yakun

    2014-11-15

    Nanobodies, derived from camelid heavy-chain antibodies, have novel and impactful applications in clinical diagnostics. Our objective is to develop a nanobody-based chemiluminescence immunoassay for sensitive detection of human prealbumin (PA). In this context, a phage display nanobody library is constructed via immunizing dromedary camel with human prealbumin. Three nanobodies have been identified by five successive bio-panning steps. Based on their high expression level and good affinity, two out of three are chosen for further study. Magnetic beads (MBs) were functionalized with PEI by acylamide bond formed between the carboxyl group on the surface of the MB. Then, an anti-PA nanobody (Nb1) can be effectively immobilized onto the surface of the functionalized MB using glutaradehyde as the link. The modified MBs with Nb1 can specifically capture the target PA and reacted with silica nanoparticles with co-immobilized HRP and anti-PA nanobody (Nb2). The concentration of PA was detected by flow injection chemiluminescence. When using MB/PEI as the carrier of anti-PA Nb1, the CL signal significantly increased to 4-fold compared with the signal using MB without PEI modification. The CL signal was further amplified to 5-fold when Si/Nb2 was used as the signal probe. Under optimized conditions, the present immunoassay exhibited a wide quantitative range from 0.05 to 1000 μg L(-1) with a detection limit of 0.01 μg L(-1). The sensitivity of the proposed immunoassay offers great promises in providing a sensitive, specific, time saving, and potential method for detecting PA in clinical settings. Copyright © 2014 Elsevier B.V. All rights reserved.

  5. Use of flow injection mass spectrometric fingerprinting and chemometrics for differentiation of three black cohosh species

    Science.gov (United States)

    Huang, Huilian; Sun, Jianghao; McCoy, Joe-Ann; Zhong, Haiyan; Fletcher, Edward J.; Harnly, James; Chen, Pei

    2015-03-01

    Flow injection mass spectrometry (FIMS) was used to provide chemical fingerprints of black cohosh (Actaea racemosa L.) in a manner of minutes by omitting the separation step. This method has proven to be a powerful tool for botanical authentication and in this study it was used to distinguish between three Actaea species prior to a more detailed chemical analysis using ultra high-performance liquid chromatography high-resolution mass spectrometry (UHPLC-HRMS). Black cohosh has become increasingly popular as a dietary supplement in the United States for the treatment of symptoms related to menopause. However, it has been known to be adulterated with the Asian Actaea dahurica (Turcz. ex Fisch. & C.A.Mey.) Franch. species (syn. Cimicifuga dahurica (Turcz.) Maxim). Existing methods for identification of black cohosh and differentiation of Actaea species are usually lengthy, laborious, and lack robustness, often based on the comparison of a few pre-selected components. Chemical fingerprints were obtained for 77 black cohosh samples and their related species using FIMS in the negative ion mode. The analysis time for each sample was less than 2 min. All data were processed using principal component analysis (PCA). FIMS fingerprints could readily differentiate all three species. Representative samples from each of the three species were further examined using UHPLC-MS to provide detailed profiles of the chemical differences between the three species and were compared to the PCA loadings. This study demonstrates a simple, fast, and easy analytical method that can be used to differentiate A. racemosa, Actaea podocarpa, and A. dahurica.

  6. Determination of Free and Total Sulfites in Wine using an Automatic Flow Injection Analysis System with Voltammetric Detection

    OpenAIRE

    Gonçalves, Luís Moreira; Pacheco, João Grosso; Magalhães, Paulo Jorge; Rodrigues, José António; Barros, Aquiles Araújo

    2009-01-01

    Abstract An automated Flow Injection Analysis (FIA) system based on a initial analyte separation by gas-diffusion and subsequent determination by square-wave voltammetry (SWV) in a flow cell is proposed for the determination of total and free content of sulphur dioxide (SO2) in wine. The proposed method was compared with two iodometric methodologies (the Ripper method and the simplified method commonly used by the wine industry). The developed method shown repeatability (RSD lower ...

  7. Non-enzymatic amperometric sensor for hydrogen peroxide based on a biocomposite made from chitosan, hemoglobin, and silver nanoparticles

    International Nuclear Information System (INIS)

    Tian, L.; Feng, Y.; Qi, Y.; Wang, B.; Chen, Y.; Fu, X.

    2012-01-01

    We report on a novel non-enzymatic sensor for hydrogen peroxide (HP) that is based on a biocomposite made up from chitosan (CS), hemoglobin (Hb), and silver nanoparticles (AgNPs). The AgNPs were prepared in the presence of CS and glucose in an ultrasonic bath, and CS is found to act as a stabilizing agent. They were then combined with Hb and CS to construct a carbon paste biosensor. The resulting electrode gave a well-defined redox couple for Hb, with a formal potential of about -0.17 V (vs. SCE) at pH 6. 86 and exhibited a remarkable electrocatalytic activity for the reduction of HP. The sensor was used to detect HP by flow injection analysis, and a linear response is obtained in the 0. 08 to 250 μM concentration range. The detection limit is 0.05 μM (at S/N = 3). These characteristics, along with its long-term stability make the sensor highly promising for the amperometric determination of HP. (author)

  8. A new amperometric glucose biosensor based on screen printed carbon electrodes with rhenium(IV - oxide as a mediator

    Directory of Open Access Journals (Sweden)

    ALBANA VESELI

    2012-11-01

    Full Text Available Rhenium(IV-oxide, ReO2, was used as a mediator for carbon paste (CPE and screen printed carbon (SPCE electrodes for the catalytic amperometric determination of hydro-gen peroxide, whose overpotential for the reduction could be lowered to -0.1 V vs. Ag/AgCl in flow injection analysis (FIA using phosphate buffer (0.1 M, pH=7.5 as a carrier. For hydrogen peroxide a detection limit (3σ of 0.8 mg L-1 could be obtained.ReO2-modified SPCEs were used to design biosensors with a template enzyme, i.e. glucose oxidase, entrapped in a Nafion membrane. The resulting glucose sensor showed a linear dynamic range up to 200 mg L-1 glucose with a detection limit (3σ of 0.6 mg L-1. The repeatability was 2.1 % RSD (n = 5 measurements, the reproducibility 5.4 % (n = 5 sensors. The sensor could be applied for the determination of glucose in blood serum in good agreement with a reference method.

  9. Amperometric and coulometric methods of platinum metal determination. (Review)

    International Nuclear Information System (INIS)

    Ezerskaya, N.A.

    1981-01-01

    Reviewed are works published in the period from 1957-1979, on amperometric and coulometric (potentiostatistic and amperostatistic variant) determination of platinum metals, Ru in particular. During amperometric titration of Ru the following titrantes are used: hydroquinone, thioxne thiourea, Na 2 S 2 O 3 . It is proposed to titrate Ru in the form of ruthenate-ion with hydrazine sulphate in alkal: medium according to the current of reagent oxidation. During coulometric determination of Ru the electrogenerating titrant TiCl 3 or Ti 2 (SO 4 ) 3 (for initial form of Ru [RuCl 6 ] 2- ) is used [ru

  10. Simple flow injection colorimetric system for determination of paraquat in natural water.

    Science.gov (United States)

    Chuntib, Prakit; Jakmunee, Jaroon

    2015-11-01

    A simple and low cost flow injection colorimetric system has been developed for determination of paraquat in natural water. The developed method is based on the reduction of paraquat by using sodium dithionite as a reducing agent in an alkaline medium to produce a blue free radical ion that can be detected by a simple light emitting diode-light dependent resistor (LED-LDR) colorimeter. The standard or sample solution was injected via a set of 3-way solenoid valves into a water carrier stream and flowed to merge with reagent to generate a colored product which is proportional to the concentration of paraquat ion in the solution. Under the optimum condition of the system, i.e., mixing coil length 30 cm, flow rate 2.0 mL min(-1), sample volume 100 μL, concentrations of dithionite 0.1% (w/v) and sodium hydroxide 0.06 mol L(-1), a linear calibration graph in the range of 0.2-10.0 mg L(-1) with a correlation coefficient of 0.9996, and a limit of detection of 0.15 mg L(-1) were achieved. Relative standard deviation for 9 replicate injections of 1 mg L(-1) paraquat is 3.7%. A sample throughput of 40 injections h(-1) was achieved. The limit of detection can be improved by off-line preconcentration of paraquat employing a column packed with Dowex 50WX8-100 (H) cation exchange resin and eluted with 10% (w/v) ammonium chloride in ammonium buffer solution pH 10. The eluting solution was then injected into the FI system for paraquat determination. The proposed system did not suffer from interferences of some possible ions in natural water and other herbicides. Recoveries obtained by spiking 0.5 and 5.0 mg L(-1) paraquat standard into water samples were in the range of 104-110% and 101-105%, respectively. The developed system can be conveniently applied for screening of paraquat contaminated in natural water. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. Homemade Bienzymatic-Amperometric Biosensor for Beverages Analysis

    Science.gov (United States)

    Blanco-Lopez, M. C.; Lobo-Castanon, M. J.; Miranda-Ordieres, A. J.

    2007-01-01

    The construction of an amperometric biosensor for glucose analysis is described demonstrating that the analysis is easy to perform and the biosensor gives good analytical performance. This experiment helped the students to acquire problem-solving and teamwork skills, allowing them to reach a high level of independent and critical thought.

  12. Amperometric biosensor for Salmonella typhimurium detection in milk

    Science.gov (United States)

    This paper reports an amperometric biosensor for rapid and sensitive Salmonella Typhimurium detection in milk. The biosensor was assembled from the self-assembled monolayers technique on a gold surface. In this device, polyclonal antibodies were oriented by protein A. The biosensor structure was cha...

  13. Sensitive amperometric determination of hydrazine using a carbon ...

    Indian Academy of Sciences (India)

    Sensitive amperometric determination of hydrazine using a carbon paste electrode modified with silver-doped zeolite L nanoparticles. NEDA SALEK GILANI ... The unique porous structure of nanozeolite L offers a promising catalyst support candidate for efficient electrochemical sensing of hydrazine. The sensor exhibited ...

  14. A flow-through amperometric sensor micro-analytical systems

    NARCIS (Netherlands)

    Pijanowska, D.; Pijanowska, D.G.; Sprenkels, A.J.; Olthuis, Wouter; Bergveld, Piet

    2003-01-01

    In this paper, the performance of the flow-through amperometric sensor based on semi-permeable dialysis tubing implemented in silicon is presented. The sensor is designed in the form to be an integral component of a lab-on-a-chip systems and it has been successfully incorporated into an integrated

  15. A Nafion -based co-planar electrode amperometric sensor for ...

    Indian Academy of Sciences (India)

    Administrator

    Dedicated to the memory of the late Professor S K Rangarajan ... A co-planar electrode device, fabricated with all electrodes (working, counter and reference) on the same face of a Nafion. ® polymer electrolyte membrane, is proposed for the amperometric detection of gaseous methanol using Pt as the working electrode.

  16. A Simple and Sensitive Flow Injection Optical Fibre Biosensor Based on Immobilised Enzyme for Monitoring of Pesticides

    Directory of Open Access Journals (Sweden)

    B. Kuswandi

    2007-02-01

    Full Text Available A simple and sensitive flow injection optical fibre biosensor based on immobilised enzyme for monitoring of pesticides has been developed. The optical fibre biosensor consists of immobilised acethylcholinesterase (AChE coupled with commercial pH indicator strip. The biosensing process involves the inhibition of AChE by pesticides, where the pH change has been monitored via a pH indicator strip as an optical transducer. The enzyme as a bio-recognition element has been immobilised onto solid-support material (i.e. covalently bond onto preactivated isothiocyanate glass, ICG and then packed in a thermostatic bioreactor connected to the flow-cell that contains pH indicator strip. In the presence of a constant AChE, a colour of the pH layer change and the measured reflected signal could be related to the pesticide concentration in the sample solution. The performance of the flow injection optical biosensor system has been optimized, including chemical and physical parameters. The calibration plot of the inhibition for the determination of organophosphate pesticides (dimethoate and carbamate pesticide (propoxur were in the range of 50 to 1000 µg/l for dimethoate and 10 to 100 µg/l for propoxur. The biosensor allows lower detection limits, calculated at I10%, for propoxur (4.9 µg/l than for dimethoate (24 µg/l, and produces highly reproducible response (RSD<1.5% and readily reversible in the case of carbamate pesticide. While in the case of organophosphate, the regeneration has been possible by treatment with hydroxylamine solution. The flow injection optical fibre biosensor system has been successfully applied for the determination of pesticides in the real water samples.

  17. Automated flow-injection method for cadmium determination with pre-concentration and reagent preparation on-line

    Directory of Open Access Journals (Sweden)

    María S. Di Nezio

    2005-02-01

    Full Text Available The spectrophotometric determination of Cd(II using a flow injection system provided with a solid-phase reactor for cadmium preconcentration and on-line reagent preparation, is described. It is based on the formation of a dithizone-Cd complex in basic medium. The calibration curve is linear between 6 and 300 µg L-1 Cd(II, with a detection limit of 5.4 µg L-1, an RSD of 3.7% (10 replicates in duplicate and a sample frequency of 11.4 h-1. The proposed method was satisfactorily applied to the determination of Cd(II in surface, well and drinking waters.

  18. Flow injection gas chromatography with sulfur chemiluminescence detection for the analysis of total sulfur in complex hydrocarbon matrixes.

    Science.gov (United States)

    Hua, Yujuan; Hawryluk, Myron; Gras, Ronda; Shearer, Randall; Luong, Jim

    2018-01-01

    A fast and reliable analytical technique for the determination of total sulfur levels in complex hydrocarbon matrices is introduced. The method employed flow injection technique using a gas chromatograph as a sample introduction device and a gas phase dual-plasma sulfur chemiluminescence detector for sulfur quantification. Using the technique described, total sulfur measurement in challenging hydrocarbon matrices can be achieved in less than 10 s with sample-to-sample time ideal for fast analysis or trace sulfur analysis. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Partial least-squares-discriminant analysis differentiating Chinese wolfberries by UPLC-MS and flow injection mass spectrometric (FIMS) fingerprints.

    Science.gov (United States)

    Lu, Weiying; Jiang, Qianqian; Shi, Haiming; Niu, Yuge; Gao, Boyan; Yu, Liangli Lucy

    2014-09-17

    Lycium barbarum L. fruits (Chinese wolfberries) were differentiated for their cultivation locations and the cultivars by ultraperformance liquid chromatography coupled with mass spectrometry (UPLC-MS) and flow injection mass spectrometric (FIMS) fingerprinting techniques combined with chemometrics analyses. The partial least-squares-discriminant analysis (PLS-DA) was applied to the data projection and supervised learning with validation. The samples formed clusters in the projected data. The prediction accuracies by PLS-DA with bootstrapped Latin partition validation were greater than 90% for all models. The chemical profiles of Chinese wolfberries were also obtained. The differentiation techniques might be utilized for Chinese wolfberry authentication.

  20. Cobalt phthalocyanine as a novel molecular recognition reagent for batch and flow injection potentiometric and spectrophotometric determination of anionic surfactants

    OpenAIRE

    El-Nemma, Eman M.; Badawi, Nahla M.; Hassan, Saad S. M.

    2008-01-01

    Cobalt(II) phthalocyanine [Co(II)Pc] is used as both an ionophore and chromogen for batch and flow injection potentiometric and spectrophotometric determination of anionic surfactants (SDS), respectively. The potentiometric technique involves preparation of a polymeric membrane sensor by dispersing [Co(II)Pc] in a plasticized PVC membrane. Under batch mode of operation, the sensor displays a near-Nernstian slope of −56.5 mV decade−1, wide response linear range of 7.8 × 10−4 to 8.0 × 10−7 mol ...

  1. Estimation of the quantification uncertainty from flow injection and liquid chromatography transient signals in inductively coupled plasma mass spectrometry

    International Nuclear Information System (INIS)

    Laborda, Francisco; Medrano, Jesus; Castillo, Juan R.

    2004-01-01

    The quality of the quantitative results obtained from transient signals in high-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICPMS) and flow injection-inductively coupled plasma mass spectrometry (FI-ICPMS) was investigated under multielement conditions. Quantification methods were based on multiple-point calibration by simple and weighted linear regression, and double-point calibration (measurement of the baseline and one standard). An uncertainty model, which includes the main sources of uncertainty from FI-ICPMS and HPLC-ICPMS (signal measurement, sample flow rate and injection volume), was developed to estimate peak area uncertainties and statistical weights used in weighted linear regression. The behaviour of the ICPMS instrument was characterized in order to be considered in the model, concluding that the instrument works as a concentration detector when it is used to monitorize transient signals from flow injection or chromatographic separations. Proper quantification by the three calibration methods was achieved when compared to reference materials, although the double-point calibration allowed to obtain results of the same quality as the multiple-point calibration, shortening the calibration time. Relative expanded uncertainties ranged from 10-20% for concentrations around the LOQ to 5% for concentrations higher than 100 times the LOQ

  2. Determination of inorganic arsenic and its organic metabolites in urine by flow-injection hydride generation atomic absorption spectrometry.

    Science.gov (United States)

    Hanna, C P; Tyson, J F; McIntosh, S

    1993-08-01

    A method has been developed for the determination of inorganic arsenic [As(III) and As(V)] and its organic metabolites (monomethylarsenic and dimethylarsenic) in urine by flow-injection hydride generation atomic absorption spectrometry. The nontoxic seafood-derived arsenobetaine and arsenocholine species were first separated by a solid-phase extraction procedure. The remaining sample was digested with a mixture of nitric and sulfuric acids and potassium dichromate, followed by attack with hydrogen peroxide. The resulting As(V) was reduced to As(III) with potassium iodide in hydrochloric acid before injection into the flow-injection manifold. The percentage analytical recoveries (mean +/- 95% confidence interval) of various arsenic species added to a urine specimen at 250 micrograms/L were 108 +/- 2, 112 +/- 11, 104 +/- 7, and 95 +/- 5 for As(III), As(V), monomethylarsenic, and dimethylarsenic, respectively. For the determination of arsenic in Standard Reference Material 2670 (toxic metals in human urine), results agreed with the certified value (480 +/- 100 micrograms/L). Analyses of samples for the Centre de Toxicologie du Quebec, containing seafood-derived species, demonstrated the viability of the separation procedure. Detection limits were between 0.1 and 0.2 microgram/L in the solution injected into the manifold, and precision at 10 micrograms/L was between 2% and 3% (CV). These preliminary results show that the method might be applicable to determinations of arsenic in a range of clinical urine specimens.

  3. A simple simultaneous flow injection method based on phosphomolybdenum chemistry for nitrate and nitrite determinations in water and fish samples.

    Science.gov (United States)

    Monser, L; Sadok, S; Greenway, G M; Shah, I; Uglow, R F

    2002-05-24

    A direct spectrophotometric flow injection method for the simultaneous determination of nitrite and nitrate has been developed. The method is based on the oxidation of a phosphomolybdenum blue complex by the addition of nitrite and the decrease in absorbance of the blue complex is monitored at 820 nm. The injected sample is split into two segments. One of the streams was directly reacted with the above reagent and detected as nitrite. The other stream was passed through a copperised cadmium reductor column where reduction of nitrate to nitrite occurs, and the sample was then mixed with the reagent and passed through the cell of the spectrophotometer to be detected as nitrite plus nitrate. The conditions for the flow injection manifold parameters were optimised by experimental design and the concentration of nitrite and nitrate was determined in the linear range from 0.05 to 1.15 mug ml(-1) nitrite and 0.06 to 1.6 mug ml(-1) nitrate with a detection limit of 0.01 mug ml(-1) for nitrite and 0.025 mug ml(-1) for nitrate. The method is suitable for the simultaneous determination of nitrite and nitrate in fish and water samples with a sampling rate of 25+/-2 sample per hour.

  4. Chemiluminescent determination of vanadium(IV) using a cinchomeronic hydrazide-H2O2 system and flow injection analysis

    International Nuclear Information System (INIS)

    Pradana Perez, J.A.; Alegria, J.S. Durand; Hernando, P. Fernandez; Sierra, A. Narros

    2005-01-01

    This paper proposes a new chemiluminescent flow injection analysis (FIA) method for the determination of vanadium(IV) ions in aqueous media. The method is based on the chemiluminescent reaction that occurs between cinchomeronic hydrazide (CH) and hydrogen peroxide in a strongly alkaline medium, in which vanadium(IV) acts as a catalyst. The chemical and physical variables involved in the flow injection system are optimised using a modified simplex method. Vanadium ions can be detected in the 0.08 and 1.00 μg mL -1 range; the detection limit for a signal-to-noise ratio of 3 is 0.08 μg mL -1 . Great variations in the quantum yield were observed when cobalt(II), chromium(III), copper(II) and/or nickel(II) were present in the reaction medium. The proposed method is selective and simple, and can be successfully used to analyse water samples without the need for separation or preconcentration processes

  5. Analytical Problems in Exposing Amperometric Enzyme Biosensors to Biological Fluids

    Directory of Open Access Journals (Sweden)

    Gaia Rocchitta

    2016-05-01

    Full Text Available Enzyme-based chemical biosensors are based on biological recognition. In order to operate, the enzymes must be available to catalyze a specific biochemical reaction and be stable under the normal operating conditions of the biosensor. Design of biosensors is based on knowledge about the target analyte, as well as the complexity of the matrix in which the analyte has to be quantified. This article reviews the problems resulting from the interaction of enzyme-based amperometric biosensors with complex biological matrices containing the target analyte(s. One of the most challenging disadvantages of amperometric enzyme-based biosensor detection is signal reduction from fouling agents and interference from chemicals present in the sample matrix. This article, therefore, investigates the principles of functioning of enzymatic biosensors, their analytical performance over time and the strategies used to optimize their performance. Moreover, the composition of biological fluids as a function of their interaction with biosensing will be presented.

  6. Amperometric titration of indium with edta solution in propanol

    International Nuclear Information System (INIS)

    Gevorgyan, A.M.; Talipov, Sh.T.; Khadeev, V.A.; Kostylev, V.S.; Khadeeva, L.A.

    1980-01-01

    Optimum conditions have been chosen for titration of indium with EDTA solution in anhydrous propanol and its mixtures with some aprotic solvents using amperometric and point detection. A procedure is suggested of determining indium microcontents in the presence of large amounts of other elements. The procedure is based on its extraction preseparation followed by direct titration in the extract with a standard EDTA solution [ru

  7. Interaction of molybdenum (6) with potassium benzyldithiocarbaminate during amperometric titration

    International Nuclear Information System (INIS)

    Galushko, S.V.; Usatenko, Yu.I.

    1975-01-01

    The paper is an amperometric study of the mechanism of interaction between molybdenum (VI) and potassium benzyl dithiocarbamate [BDTC] which was based on the use of voltamperometry, electron paramagnetic resonance, infrared spectroscopy, potentiometry and elemental analysis. In amperometric titration Mo(VI) with BDTC (pH 4-2) forms a red compound of low solubility. In more acidic media the intensity of coloration is increased and a violet hue develops. On the basis of the data obtained it is concluded that in the amperometric titration of Mo(VI) with potassium BDTC there is first formation of a Mo(VI) compound, which subsequently acquires a red colour as a result of the reduction of Mo(VI) to Mo(V). It was also established that the degree of reduction is small where titration is carried out in the range pH 4.8-0.1. Quantitative determination of Mo is performed most effectively in slightly acidic media. Mo reacts with potassium BDTC in a ratio of 1:2. (E.P.)

  8. Cobalt phthalocyanine as a novel molecular recognition reagent for batch and flow injection potentiometric and spectrophotometric determination of anionic surfactants.

    Science.gov (United States)

    El-Nemma, Eman M; Badawi, Nahla M; Hassan, Saad S M

    2009-05-15

    Cobalt(II) phthalocyanine [Co(II)Pc] is used as both an ionophore and chromogen for batch and flow injection potentiometric and spectrophotometric determination of anionic surfactants (SDS), respectively. The potentiometric technique involves preparation of a polymeric membrane sensor by dispersing [Co(II)Pc] in a plasticized PVC membrane. Under batch mode of operation, the sensor displays a near-Nernstian slope of -56.5 mV decade(-1), wide response linear range of 7.8 x 10(-4) to 8.0 x 10(-7)mol L(-1), lower detection limit of 2.5 x 10(-7)mol L(-1) and exhibits high selectivity for anionic surfactants in the presence of many common ions. Under hydrodynamic mode of operation (FIA), the slope of the calibration plot, limit of detection, and working linear range are -51.1 mV decade(-1), 5.6 x 10(-7) and 1.0 x 10(-3) to 1.0 x 10(-6)mol L(-1), respectively. The spectrophotometric method is based on the use of [Co(II)Pc] solution in dimethylsulfoxide (DMSO) as a chromogenic reagent. The maximum absorption of the reagent at 658 nm linearly decreases with the increase of anionic surfactant over the concentration range 2-30 microg mL(-1). The lower limit of detection is 1 microg mL(-1) and high concentrations of many interfering ions are tolerated. Flow injection spectrophotometric measurements are carried out by injection of the surfactant test solution in a stream of the reagent in DMSO. The sample throughput, working range and lower detection limit are 25-30 samples h(-1), 4-60 and 2 microg mL(-1), respectively. The potentiometric and spectrophotometric techniques are applied to the batch and flow injection measurements of anionic surfactants in some commercial detergent products. The results agree fairly well with data obtained using the standard methylene blue spectrophotometric method.

  9. [A novel flow injection chemiluminescence method with ferricyanide and luminol for the determination of ractopamine in biological samples].

    Science.gov (United States)

    Feng, Ting; Hu, Yu-fei; Li, Gong-ke

    2012-01-01

    A novel chemiluminescence method coupled with flow injection technique for the determination of ractopamine was developed. It was based on the enhancement of the chemiluminescence by ractopamine derived from the chemiluminescence reaction between luminol and ferricyanide in sodium hydroxide medium. The linear calibration range of the chemiluminescence intensity with respect to the ractopamine concentration covers from 4.0 x 10(-9) - 8.0 x 10(-7) g x mL(-1). The relative standard deviation for ractopamine is 5.6% (n = 11), and the detection limit is 2.5 x 10(-9) g x mL(-1). The method was firstly applied to the determination of ractopamine in biological samples with satisfactory results. The recovery was between 69.3% and 101.3%.

  10. Fluorimetric determination of arsanilic acid by flow-injection analysis using on-line photo-oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Ruiz, Tomas; Martinez-Lozano, Carmen; Tomas, Virginia; Martin, Jesus [Department of Analytical Chemistry, University of Murcia (Spain)

    2002-01-01

    A flow-injection-fluorimetric method for the determination of arsanilic acid is proposed. The assay is based on the on-line decomposition of arsanilic acid in the presence of peroxydisulfate on irradiation with UV light. The arsenate generated in the photochemical reaction was reacted with molybdate in dilute nitric acid to form arsenomolybdic acid, which oxidised thiamine to thiochrome. The thiochrome was monitored fluorimetrically at 440 nm with excitation at 375 nm. The calibration graph was linear in the range 0.10-10.8 {mu}g mL{sup -1} with a correlation coefficient of 0.999. The detection limit was 0.01 {mu}g mL{sup -1} and the sample throughput was 55 samples h{sup -1}. The applicability of the method was demonstrated by determining arsanilic acid in animal foodstuffs and water. (orig.)

  11. Extractable sulphate-sulphur, total sulphur and trace-element determinations in plant material by flow injection analysis

    Energy Technology Data Exchange (ETDEWEB)

    Heanes, D.L. (South Australian Department of Agriculture, Adelaide (Australia))

    1990-01-01

    A rapid, accurate and reproducible procedure for determining total sulphur(S) and trace elements (copper, zinc, manganese and iron) in plant material is described. Plant material is digested in culture tubes with a mixture of nitric and perchloric acids containing ammonium metavanadate and calcium chloride. In the acid digest, concentrations of total-S as sulphate are determined by turbidimetry and trace-elements by flame atomic absorption spectrophotometry using flow injection analysis. The results for a range of plant materials compare well with those obtained by conventional procedures for the same elements. The microprocessor controlled digestion and multielement assay procedure described here offers improved laboratory efficiencies in materials, time and cost effectiveness. The techniques should be particularly useful when plant tissues are in limited supply.

  12. Flow Injection Analysis of Mercury Using 4-(Dimethylamino Benzaldehyde-4-Ethylthiosemicarbazone as the Ionophore of a Coated Wire Electrode

    Directory of Open Access Journals (Sweden)

    Sulaiman Ab Ghani

    2012-11-01

    Full Text Available A flow injection analysis (FIA incorporating a thiosemicarbazone-based coated wire electrode (CWE was developed method for the determination of mercury(II. A 0.1 M KNO3 carrier stream with pH between 1 and 5 and flow rate of 1 mL·min−1 were used as optimum parameters. A linear plot within the concentration range of 5 × 10−6–0.1 M Hg(II, slope of 27.8 ± 1 mV per decade and correlation coefficient (R2 of 0.984 were obtained. The system was successfully applied for the determination of mercury(II in dental amalgam solutions and spiked environmental water samples. Highly reproducible measurements with relative standard deviation (RSD < 1% (n = 3 were obtained, giving a typical throughput of 30 samples·h−1.

  13. Flow Injection/Sequential Injection Analysis Systems: Potential Use as Tools for Rapid Liver Diseases Biomarker Study

    Directory of Open Access Journals (Sweden)

    Supaporn Kradtap Hartwell

    2012-01-01

    Full Text Available Flow injection/sequential injection analysis (FIA/SIA systems are suitable for carrying out automatic wet chemical/biochemical reactions with reduced volume and time consumption. Various parts of the system such as pump, valve, and reactor may be built or adapted from available materials. Therefore the systems can be at lower cost as compared to other instrumentation-based analysis systems. Their applications for determination of biomarkers for liver diseases have been demonstrated in various formats of operation but only a few and limited types of biomarkers have been used as model analytes. This paper summarizes these applications for different types of reactions as a guide for using flow-based systems in more biomarker and/or multibiomarker studies.

  14. A novel flow injection chemiluminescence method for automated and miniaturized determination of phenols in smoked food samples.

    Science.gov (United States)

    Vakh, Christina; Evdokimova, Ekaterina; Pochivalov, Aleksei; Moskvin, Leonid; Bulatov, Andrey

    2017-12-15

    An easily performed fully automated and miniaturized flow injection chemiluminescence (CL) method for determination of phenols in smoked food samples has been proposed. This method includes the ultrasound assisted solid-liquid extraction coupled with gas-diffusion separation of phenols from smoked food sample and analytes absorption into a NaOH solution in a specially designed gas-diffusion cell. The flow system was designed to focus on automation and miniaturization with minimal sample and reagent consumption by inexpensive instrumentation. The luminol - N-bromosuccinimide system in an alkaline medium was used for the CL determination of phenols. The limit of detection of the proposed procedure was 3·10 -8 ·molL -1 (0.01mgkg -1 ) in terms of phenol. The presented method demonstrated to be a good tool for easy, rapid and cost-effective point-of-need screening phenols in smoked food samples. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Chemiluminescence determination of ferulic acid by flow-injection analysis using cerium(IV) sensitized by rhodamine 6G

    Science.gov (United States)

    Wang, Ju Peng; Li, Nian Bing; Luo, Hong Qun

    2008-11-01

    A simple, sensitive and rapid flow-injection chemiluminescence method has been developed for the determination of ferulic acid based on the chemiluminescence reaction of ferulic acid with rhodamine 6G and ceric sulfate in sulphuric acid medium. Strong chemiluminescence signal was observed when ferulic acid was injected into the acidic ceric sulfate solution in a flow-cell. The present method allowed the determination of ferulic acid in the concentration range of 8.0 × 10 -6 to 1.0 × 10 -4 mol l -1 and the detection limit for ferulic acid was 8.7 × 10 -9 mol l -1. The relative standard deviation was 2.4% for 10 replicate analyses of 1.0 × 10 -5 mol l -1 ferulic acid. The proposed method was applied to the determination of ferulic acid in Taita Beauty Essence samples with satisfactory results.

  16. Flow injection on-line preconcentration of low levels of Cr(VI) with detection by ETAAS

    DEFF Research Database (Denmark)

    Som-aum, Waraporn; Liawruangrath, Saisunee; Hansen, Elo Harald

    2002-01-01

    A flow injection (FI) on-line sorption preconcentration procedure utilizing a packed column reactor and combined with electrothermal atomic absorption spectrometry (ETAAS) is proposed for the determination of low levels of Cr(VI) in water samples. Polytetrafluoroethylene (PTFE) beads packed...... in a mini-column is used as sorbent material. The complex formed between Cr(VI) and ammonium pyrrolidine dithiocarbamate (APDC) is sorbed on the PTFE beads, and is subsequently eluted by an air-monosegmented discrete zone of absolute ethanol (35mul), the analyte being quantified by ETAAS....... The preconcentration procedure using the proposed column significantly enhances the preconcentration efficiency as compared with the preconcentration approach incorporating an open tubular PTFE knotted reactor (KR). Comparing the two procedure for equal surface sorption area, the advantages of using a packed column...

  17. Flow-injection chemiluminescence determination of acetylsalicylic acid based on its enhancing effect on the lucigenin–hydrogen peroxide system.

    Science.gov (United States)

    Wabaidur, S M; Alam, S M; Alothmana, Z A; Eldesokya, Gaber

    2014-09-01

    A sensitive flow-injection chemiluminescence method for the determination of acetylsalicylic acid is described. It is based on the enhanced chemiluminescent emission of the alkaline lucigenin–H2O2 system by acetylsalicylic acid. The difference in chemiluminescent intensity of alkaline lucigenin–H2O2 in the presence of acetylsalicylic acid from that in the absence of acetylsalicylic acid was linear at acetylsalicylic acid concentrations in the range of 0.0029–47.37 μg/mL, with detection and quantification limits of 0.0011 and 0.0029 μg/mL, respectively. The correlation coefficient of the working curve was 0.9983. The relative standard deviation (n = 10) for 25 μg/mL acetylsalicylic acid is 1.95%. All experimental parameters were optimized. The method was successfully applied to the determination of acetylsalicylic acid in pharmaceutical preparations. The recovery results obtained by the method were satisfactory.

  18. Rapid flow injection method for the determination of sulfite in wine using the permanganate-luminol luminescence system.

    Science.gov (United States)

    Navarrro, Mercedes Villar; Payán, María Ramos; López, Miguel Angel Bello; Fernández-Torres, Rut; Mochón, Manuel Callejón

    2010-10-15

    A simple, rapid and sensitive chemiluminescence method for the determination of sulfite has been developed by combining flow-injection analysis and its sensitizing effect on the known chemiluminescence emission produced by the oxidation of luminol in alkaline medium; in this work permanganate has been proposed as oxidizing reactive. The optimum conditions for the chemiluminescence emission were established. The chemiluminescence was proportional to the sulfite concentration over the range 1.6 × 10(-5) and 4.0 × 10(-4)mol L(-1). The detection limit was 4.7 × 10(-6)mol L(-1) of sulfite. The method has been satisfactorily used for the determination of free and bound sulfite in wines. Copyright © 2010 Elsevier B.V. All rights reserved.

  19. Flow-injection chemiluminometric determination of pioglitazone HCl by its sensitizing effect on the cerium-sulfite reaction.

    Science.gov (United States)

    Al-Arfaj, Nawal A; Al-Abdulkareem, Eman A; Aly, Fatma A

    2009-03-01

    A flow injection chemiluminescent (FI-CL) method was developed for the determination of pioglitazone HCl. It is based on the sensitizing effect of the drug on the oxidation reaction of sulfite with cerium(IV). The different experimental parameters affecting the chemiluminescence intensity, such as concentration of reagents and some physical parameters of the manifold, were carefully studied and incorporated into the procedure. The method permits the determination of 0.05 - 3.0 microg ml(-1) of pioglitazone HCl with correlation coefficient r = 0.9999. The lower limit of detection (LOD) is 0.01 microg ml(-1) (S/N = 2) and the lower limit of quantitation (LOQ) is 0.05 microg ml(-1). The proposed method was compared with other reported methods and was found to be equally accurate and precise. It was successfully applied to the determination of the drug in pharmaceutical preparations and in biological fluids.

  20. Flow injection on-line spectrophotometric determination of thorium(IV) after preconcentration on XAD-4 resin impregnated with oxytetracycline

    Energy Technology Data Exchange (ETDEWEB)

    Shahida, Shabnam; Khan, Muhammad Haleem [Univ. of Azad Jammu and Kashmir, Muzaffarabad (Pakistan). Dept. of Chemistry; Ali, Akbar [Pakistan Institute of Nuclear Science and Technology, Islamabad (Pakistan). Chemistry Div.

    2014-02-15

    A very sensitive, selective and simple flow injection time-based method was developed for on-line preconcentration and determination of thorium(IV) at micro g L{sup -1} levels in environmental samples. The system operation was based on thorium(IV) ion retention at pH 4.0 in the minicolumn at a flow rate of 15.2 mL min{sup -1}. The trapped complex was then eluted with 3.6 mol L{sup -1} HCl at a flow rate of 4.9 mL min{sup -1}. The amount of thorium(IV) in the eluate was measured spectrophotometrically at 651 nm using arsenazo-III solution (0.05 % in 3.6 mol L{sup -1} HCl stabilized with 1 % triton X-100, 4.9 mL min{sup -1}) as colorimetric reagent. All chemical, and flow injection variables were optimized for the quantitative preconcentration of metal and a study of interference level of various ions was also carried out. The system offered low backpressure and improved sensitivity and selectivity. At a preconcentration time of 60 s and a sample frequency of 40 h{sup -1}, the enhancement factor was 97, the detection limit was 0.25 μg L{sup -1}, and the precision expressed as relative standard deviation was 1.08 % (at 50 μg L{sup -1}), whereas for 300 s of the preconcentration time and a sample frequency of 10 h{sup -1}, the enhancement factor of 357, the detection limit (3s) of 0.069 μg L{sup -1} and the precision of 1.32 % (at 10 μg L{sup -1}) was reported. The accuracy of the developed method was sufficient and evaluated by the analysis of certified reference material IAEA-SL-1 (Lake Sediment) and spiked water samples.

  1. Simultaneous and accurate real-time monitoring of glucose and ethanol in alcoholic drinks, must, and biomass by a dual-amperometric biosensor.

    Science.gov (United States)

    Mentana, Annalisa; Palermo, Carmen; Nardiello, Donatella; Quinto, Maurizio; Centonze, Diego

    2013-01-09

    In this work the optimization and application of a dual-amperometric biosensor for simultaneous monitoring of glucose and ethanol content, as quality markers in drinks and alcoholic fermentation media, are described. The biosensor is based on glucose oxidase (GOD) and alcohol oxidase (AOD) immobilized by co-cross-linking with bovine serum albumin (BSA) and glutaraldehyde (GLU) both onto a dual gold electrode, modified with a permselective overoxidized polypyrrole film (PPYox). Response, rejection of interferents, and stability of the dual biosensor were optimized in terms of PPYox thickness, BSA, and enzyme loading. The biosensor was integrated in a flow injection system coupled with an at-line microdialysis fiber as a sampling tool. Flow rates inside and outside the fiber were optimized in terms of linear responses (0.01-1 and 0.01-1.5 M) and sensitivities (27.6 ± 0.4 and 31.0 ± 0.6 μA·M(-1)·cm(-2)) for glucose and ethanol. Excellent anti-interference characteristics, the total absence of "cross-talk", and good response stability under operational conditions allowed application of the dual biosensor in accurate real-time monitoring (at least 15 samples/h) of alcoholic drinks, white grape must, and woody biomass.

  2. Differentiation of the four major types (C. Burmannii, C. Verum, C. cassia, And C. Loureiroi) of cinnamons using a flow-injection mass spectrometric (FIMS) fingerprinting method

    Science.gov (United States)

    A simple and efficient flow-injection mass spectrometric (FIMS) method was developed to differentiate cinnamon (Cinnamomum) bark (CB) samples of the four major species (C. burmannii, C. verum, C. aromaticum, and C. loureiroi) of cinnamon. Fifty cinnamon samples collected from China, Vietnam, Indon...

  3. Differentiation of the two major species of Echinacea (E. augustifolia and E. purpurea) using a flow injection mass spectrometric (FIMS) fingerprinting method and chemometric analysis

    Science.gov (United States)

    A rapid, simple, and reliable flow-injection mass spectrometric (FIMS) method was developed to discriminate two major Echinacea species (E. purpurea and E. angustifolia) samples. Fifty-eight Echinacea samples collected from United States were analyzed using FIMS. Principle component analysis (PCA) a...

  4. Rapid isolation of biomarkers for compound specific radiocarbon dating using high-performance liquid chromatography and flow injection analysis-atmospheric pressure chemical ionisation mass spectrometry

    NARCIS (Netherlands)

    Sinninghe Damsté, J.S.; Smittenberg, R.H.; Hopmans, E.C.; Schouten, S.

    2002-01-01

    Repeated semi-preparative normal-phase HPLC was performed to isolate selected biomarkers from sediment extracts for radiocarbon analysis. Flow injection analysis mass spectrometry was used for rapid analysis of collected fractions to evaluate the separation procedure, taking only 1 min per fraction.

  5. Flow injection on-line dilution for multi-element determination in human urine with detection by inductively coupled plasma mass spectrometry

    DEFF Research Database (Denmark)

    Wang, Jianhua; Hansen, Elo Harald; Gammelgaard, Bente

    2001-01-01

    A simple flow injection on-line dilution procedure with detection by inductively coupled plasma mass spectrometry (ICP-MS) was developed for the determination of copper, zinc, arsenic, lead, selenium, nickel and molybdenum in human urine. Matrix effects were minimized by employing a dilution factor...

  6. Rapid determination of 99Tc in environmental samples by high resolution ICP-MS coupled with on-line flow injection system

    International Nuclear Information System (INIS)

    Kim, C.K.; Kim, C.S.; Rho, B.H.; Lee, J.I.

    2002-01-01

    High resolution inductively coupled plasma mass spectrometry coupled with an on-line flow injection system (FI-HR-ICP-MS) was applied to determine the ultra-trace level 99 Tc in soil. The flow injection system (PrepLab TM ) was composed of two TEVA-Spec R resins, reduced remarkably the sample amounts and the analysis time, compared to the conventional analytical methods. In the flow injection system, Mo and Ru were sufficiently eliminated by using the flow injection system, with the decontamination factors of 1.6 x 10 4 and 9.9 x 10 5 , respectively. With the present method, it was possible to determine ultra-low level of 99 Tc in 3∼6 soil at 3-5 hours of analysis time per sample. The relative standard deviation for each sample was less than 4%. The detection limits for 99 Tc was 85 fg x ml -1 (0.05 mBq x ml -1 ), which was calculated from the three times standard deviation of the count rate of the blank. (author)

  7. Investigations into the Role of Modifiers for Entrapment of Hydrides in Flow Injection Hydride Generation Electrothermal Atomic Absorption Spectrometry as Exemplified for the Determination of Germanium

    DEFF Research Database (Denmark)

    Hilligsøe, Bo; Andersen, Jens Enevold Thaulov; Hansen, Elo Harald

    1997-01-01

    Pd-conditioned graphite tubes, placed in the furnace of an atomic absorption spectrometry instrument, are used for entrapment of germane as generated in an associated flow injection system. Two different approaches are tested with the ultimate aim to allow multiple determinations, that is...

  8. Selective Flow Injection Analysis of Ultra-trace Amounts of Cr(VI), Preconcentration of It by Solvent Extraction, and Determination by Electrothermal Atomic Absorption Spectrometry (ETAAS)

    DEFF Research Database (Denmark)

    Nielsen, Steffen; Sturup, Stefan; Spliid, Henrik

    1999-01-01

    A rapid, robust, sensitive and selective time-based flow injection (FI) on-line solvent extraction system interfaced with electrothermal atomic absorption spectrometry (ETAAS) is described for analyzing ultra-trace amounts of Cr(VI). The sample is initially mixed on-line with isobutyl methyl ketone...

  9. Raman spectroscopic analysis of cyanogenic glucosides in plants: development of a Flow Injection Surface-Enhanced Raman Scatter (FI-SERS) method for determination of cyanide

    DEFF Research Database (Denmark)

    Thygesen, Lisbeth Garbrecht; Jørgensen, Kirsten; Møller, Birger Lindberg

    2004-01-01

    -dried sorghum leaf was also obtained using this instrument. Surface-enhanced Raman Spectroscopy (SERS) was demonstrated to be a more sensitive method that enabled determination of the cyanogenic potential of plant tissue. The SERS method was optimized by flow injection (FI) using a colloidal gold dispersion...... as effluent. Potential problems and pitfalls of the method are discussed....

  10. An automatic flow injection analysis procedure for photometric determination of ethanol in red wine without using a chromogenic reagent.

    Science.gov (United States)

    Borges, Sivanildo S; Frizzarin, Rejane M; Reis, Boaventura F

    2006-05-01

    An automatic reagentless photometric procedure for the determination of ethanol in red wine is described. The procedure was based on a falling drop system that was implemented by employing a flow injection analysis manifold. The detection system comprised an infrared LED and a phototransistor. The experimental arrangement was designed to ensure that the wine drop grew between these devices, thus causing a decrease in the intensity of the radiation beam coming from the LED. Since ethanol content affected the size of the wine drop this feature was exploited to develop an analytical procedure for the photometric determination of ethanol in red wine without using a chromogenic reagent. In an attempt to prove the usefulness of the proposed procedure, a set of red wines were analysed. No significant difference between our results and those obtained with a reference method was observed at the 95% confidence level. Other advantages of our method were a linear response ranging from 0.17 up to 5.14 mol L(-1) (1.0 up to 30.0%) ethanol (R = 0.999); a limit of detection of 0.05 mol L(-1) (0.3%) ethanol; a relative standard deviation of 2.5% (n = 10) using typical wine sample containing 2.14 mol L(-1) (12.5%) ethanol; and a sampling rate of 50 determinations per hour.

  11. Reverse flow injection spectrophotometric determination of ciprofloxacin in pharmaceuticals using iron from soil as a green reagent

    Science.gov (United States)

    Palamy, Sysay; Ruengsitagoon, Wirat

    2018-02-01

    A novel reverse flow injection spectrophotometric method for the determination of ciprofloxacin was successfully combined with the on-line introduction of an iron solution extracted from soil as green reagent. The assay was optimized by a univariate method to select the optimum conditions for the highest absorbance and highest stability of the complex. Beer-Lambert's law (λmax = 440 nm) is obeyed in the range 0.5-50 μg mL- 1 with a correlation coefficient (r2) of 0.9976 and 0.9996 using soil as green reagent from Khon Kaen, Thailand and Vientiane, Laos, respectively. The average percentage recoveries were in the range of 98.55-102.14% and the precision was in the range of 0.80-1.73%. The limit of detection and the limit of quantitation were 0.20 and 0.69 μg mL- 1, respectively, with a sampling rate of over 46 samples h- 1. The method was successfully applied to the determination of ciprofloxacin in commercial pharmaceutical formulations. The results were in good agreement with those obtained by the reference HPLC method using a t-test at 95% of confidence level for comparison. This method is suitable for laboratories looking for alternative analytical methods using green reagents.

  12. Use of a computer controlled flow injection analysis system for the rapid on-line determination of distribution coefficients

    International Nuclear Information System (INIS)

    Nekimken, H.L.

    1987-01-01

    A search for simpler and more effective ways to perform various actinide and lanthanide separations is in progress. Emphasis has been on evaluating ligands for their ability to complex and extract metal ions under a variety of experimental conditions. To evaluate effectively these extractants and to ultimately correlate structural features with extraction capabilities, a large volume of distribution coefficient (Kd) data must be acquired. Kd data for each ligand should be obtained as a function of such variables as ligand and metal ion concentration, pH, and organic solvent employed. Unfortunately, batch Kd experiments are generally time consuming and tedious. A computer controlled flow injection analysis system has been developed to obtain rapid on-line Kd data. A diluter/dispenser is utilized to generate the various aqueous metal ion samples. Results indicate this FIA system can be used to effectively determine Kd values for certain chemical systems. The FIA apparatus should also be useful for other applications that require on-line extraction and/or detection (or kinetics studies). Reasonably good agreement has been obtained between batch and FIA Kd values for the extraction of Pb(II), Zn(II) and Cd(II) by dithizone. Fe(III) by 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 (PMBP) and uranyl by the 5-thione derivative of BMBP (SPMBP). A study of the uranyl-SPBMP chemical system with FIA is now nearing completion

  13. Introduction of Hydrogen Peroxide as an Oxidant in Flow Injection Analysis: Speciation of Cr(III) and Cr(VI)

    DEFF Research Database (Denmark)

    Andersen, Jens Enevold Thaulov

    1998-01-01

    Hydrogen peroxide was used as an oxidant in Flow Injection Analysis (FIA). The formation of gaseous components during the analysis was suppressed by maintaining a concentration lower than 0.15% of hydrogen peroxide in 0.1 M NaOH. By this method Cr(III) was oxidised on-line to Cr(VI) which...... was detected spectrophotometrically at 548 nm by complexation with 1,5-diphenylcarbazide (DPC). Linear responses was found for concentrations less than 20 mg/L and the sensitivities obtained of the pure species were 0.0225 ± 0.0015 L/mg for Cr(III) and 0.0420 ± 0.0015 L/mg for Cr(VI). For the speciation of Cr......(III) and Cr(VI) the analysis of both species was performed by treating them as mutual interference’s. Thus, the total amount of chromium species was measured by FIA and the total amount of chromium was measured by Graphite Atomic Absorption Spectrometry (G-AAS). The speciation was then performed...

  14. Miniaturized ionophore-based potentiometric sensors for the flow-injection determination of metformin in pharmaceutical formulations and biological fluids.

    Science.gov (United States)

    Khaled, Elmorsy; Kamel, Manal S; Hassan, Hassan N; Abd El-Alim, Sameh H; Aboul-Enein, Hassan Y

    2012-12-07

    Miniaturized potentiometric sensors based on β-cyclodextrins (β-CDs) are described for determination of metformin (Mf) in pharmaceutical preparations and biological fluids. Electrode matrix compositions are optimized on the basis of the nature and content of sensing ionophore, ionic sites and plasticizers. Coated wire electrodes (CWEs) modified with heptakis(2,3,6-tri-O-methyl)-β-CD, sodium tetrakis(4-fluorophenyl)borate (NaTFPB) and 2-fluorophenyl 2-nitrophenyl ether (f-NPE), work satisfactorily in the concentration range from 10(-6) to 10(-1) mol L(-1) with Nernstian compliance (55.7 ± 0.4 mV per decade activity) and a detection limit of 8 × 10(-7) mol L(-1). Incorporation of β-CD as a molecular recognition element improved the electrode sensitivity and selectivity due to encapsulation of Mf into the β-CD cavity (host-guest interaction). The developed electrodes have been successfully applied for the potentiometric determination of Mf under batch and flow injection analysis (FIA). FIA allows analysis of 90 samples per h offering the advantages of simplicity, accuracy and automation feasibility. The dissolution profile for metformin pharmaceutical samples (Cidophage®) was monitored using the proposed electrode in comparison with the official spectrophotometric methods. Characterization of the formed Mf-β-CD inclusion complexes is discussed in detail.

  15. Flow injection chemiluminescence determination of lercanidipine based on N-chlorosuccinimide-eosin Y post-chemiluminescence reaction.

    Science.gov (United States)

    Wang, Guowei; Zhao, Fang; Gao, Ying

    2014-12-01

    A novel post-chemiluminescence (PCL) reaction was discovered when lercanidipine was injected into the CL reaction mixture of N-chlorosuccinimide with alkaline eosin Y in the presence of cetyltrimethylammonium bromide (CTAB), where eosin Y was used as the CL reagent and CTAB as the surfactant. Based on this observation, a simple and highly sensitive PCL method combined with a flow injection (FI) technique was developed for the assay of lercanidipine. Under optimum conditions, the CL signal was linearly related to the concentration of lercanidipine in the range 7.0 × 10(-10) to 3.0 × 10(-6)  g/mL with a detection limit of 2.3 × 10(-10) g/mL (3σ). The relative standard deviation (RSD) was 2.1% for 1.0 × 10(-8) g/mL lercanidipine (n = 13). The proposed method had been applied to the estimation of lercanidipine in tablets and human serum samples with satisfactory results. The possible CL mechanism is also discussed briefly. Copyright © 2014 John Wiley & Sons, Ltd.

  16. Automated flow injection determination of salicylates using Trinder reaction for clinical analysis, assays and dissolution studies of formulations.

    Science.gov (United States)

    Koupparis, M A; Anagnostopoulou, P I

    1988-01-01

    An automated flow-injection technique is described for salicylate (25-250 or 80-800 mg l(-1)), salicylamide (30-300 mg l(-1)), methylsalicylate (100-1000 mg l(-1)) and acetylsalicylic acid (after alkaline hydrolysis), based on their colour reaction with iron (III) in weak acid medium. The method was evaluated for the determination of salicylate in serum, the assay of the drugs in commercial formulations and automated dissolution studies of drug tablets. There were decreased interferences because of the short reaction time. The precision was good with RSD less than 1% in all cases. Recoveries of salicylate from spiked sera (100-1000 mg l(-1)) varied from 96.4-102.5% (mean 99.3%), and from spiked sample solutions of acetylsalicylic acid, 97.8-103.0% (mean 99.6%). The results of the analysis of commercial drug formulations obtained with the proposed method agreed well with the current USP and BP procedures, with differences of 0.4-1.5% (mean 0.8%). High measurement rates of 180 or 95 per hour were achieved using manifolds without and with predilution respectively.

  17. A Customizable Flow Injection System for Automated, High Throughput, and Time Sensitive Ion Mobility Spectrometry and Mass Spectrometry Measurements

    Energy Technology Data Exchange (ETDEWEB)

    Orton, Daniel J. [Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, United States; Tfaily, Malak M. [Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, United States; Moore, Ronald J. [Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, United States; LaMarche, Brian L. [Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, United States; Zheng, Xueyun [Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, United States; Fillmore, Thomas L. [Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, United States; Chu, Rosalie K. [Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, United States; Weitz, Karl K. [Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, United States; Monroe, Matthew E. [Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, United States; Kelly, Ryan T. [Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, United States; Smith, Richard D. [Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, United States; Baker, Erin S. [Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, United States

    2017-12-13

    To better understand disease conditions and environmental perturbations, multi-omic studies (i.e. proteomic, lipidomic, metabolomic, etc. analyses) are vastly increasing in popularity. In a multi-omic study, a single sample is typically extracted in multiple ways and numerous analyses are performed using different instruments. Thus, one sample becomes many analyses, making high throughput and reproducible evaluations a necessity. One way to address the numerous samples and varying instrumental conditions is to utilize a flow injection analysis (FIA) system for rapid sample injection. While some FIA systems have been created to address these challenges, many have limitations such as high consumable costs, low pressure capabilities, limited pressure monitoring and fixed flow rates. To address these limitations, we created an automated, customizable FIA system capable of operating at diverse flow rates (~50 nL/min to 500 µL/min) to accommodate low- and high-flow instrument sources. This system can also operate at varying analytical throughputs from 24 to 1200 samples per day to enable different MS analysis approaches. Applications ranging from native protein analyses to molecular library construction were performed using the FIA system. The results from these studies showed a highly robust platform, providing consistent performance over many days without carryover as long as washing buffers specific to each molecular analysis were utilized.

  18. A Customizable Flow Injection System for Automated, High Throughput, and Time Sensitive Ion Mobility Spectrometry and Mass Spectrometry Measurements.

    Science.gov (United States)

    Orton, Daniel J; Tfaily, Malak M; Moore, Ronald J; LaMarche, Brian L; Zheng, Xueyun; Fillmore, Thomas L; Chu, Rosalie K; Weitz, Karl K; Monroe, Matthew E; Kelly, Ryan T; Smith, Richard D; Baker, Erin S

    2018-01-02

    To better understand disease conditions and environmental perturbations, multiomic studies combining proteomic, lipidomic, and metabolomic analyses are vastly increasing in popularity. In a multiomic study, a single sample is typically extracted in multiple ways, and various analyses are performed using different instruments, most often based upon mass spectrometry (MS). Thus, one sample becomes many measurements, making high throughput and reproducible evaluations a necessity. One way to address the numerous samples and varying instrumental conditions is to utilize a flow injection analysis (FIA) system for rapid sample injections. While some FIA systems have been created to address these challenges, many have limitations such as costly consumables, low pressure capabilities, limited pressure monitoring, and fixed flow rates. To address these limitations, we created an automated, customizable FIA system capable of operating at a range of flow rates (∼50 nL/min to 500 μL/min) to accommodate both low- and high-flow MS ionization sources. This system also functions at varying analytical throughputs from 24 to 1200 samples per day to enable different MS analysis approaches. Applications ranging from native protein analyses to molecular library construction were performed using the FIA system, and results showed a highly robust and reproducible platform capable of providing consistent performance over many days without carryover, as long as washing buffers specific to each molecular analysis were utilized.

  19. Detection of Total Phenol in Green and Black Teas by Flow Injection System and Unmodified Screen Printed Electrode

    Directory of Open Access Journals (Sweden)

    Ivanildo Luiz de Mattos

    2010-01-01

    Full Text Available A flow injection system using an unmodified gold screen-printed electrode was employed for total phenol determination in black and green teas. In order to avoid passivation of the electrode surface due to the redox reaction, preoxidation of the sample was realized by hexacyanoferrate(III followed by addition of an EDTA solution. The complex formed in the presence of EDTA minimizes or avoids polymerization of the oxidized phenols. The previously filtered tea sample and hexacyanoferrate(III reagent were introduced simultaneously into two-carrier streams producing two reproducible zones. At confluence point, the pre-oxidation of the phenolic compounds occurs while this zone flows through the coiled reactor and receives the EDTA solution before phenol detection. The consumption of ferricyanide was monitorized at 360 mV versus Ag/AgCl and reflected the total amount of phenolic compounds present in the sample. Results were reported as gallic acid equivalents (GAEs. The proposed system is robust, versatile, environmentally-friendly (since the reactive is used only in the presence of the sample, and allows the analysis of about 35–40 samples per hour with detection limit = 1 mg/L without the necessity for surface cleaning after each measurement. Precise results are in agreement with those obtained by the Folin-Ciocalteu method.

  20. Development of a chromatographic low pressure flow injection system: application to the analysis of methylxanthines in coffee.

    Science.gov (United States)

    Santos, João Rodrigo; Rangel, António O S S

    2012-02-17

    In this work, the coupling of a commercial monolithic column to a traditional low pressure FIA system is proposed for the analysis of theobromine, theophylline and caffeine in coffee brewed samples using UV detection. The parameters mobile phase composition, flow rate and loop volume were evaluated and discussed considering the various chromatographic parameters in order to enable resolution of the methylxanthines studied within the coffee brewed sample matrix. The analyses of methylxanthines in coffee brewed samples by the proposed methodology were in good agreement with those obtained by the reference procedure based on HPLC. Relative errors were below 6% for all samples analyzed. Detection limits in the selected experimental conditions were within 10(-6)M range for theobromine and theophylline, and 10(-5) M for caffeine. The determination rate of the three methylxanthines for coffee brewed samples was ca of 10 h(-1). The main advantage of the proposed flow system was the possibility to perform chromatographic separations in low pressure flow systems. This substantial improvement was achieved due to the compatibility of monolithic columns within the flow injection system surpassing in this way one of the main handicaps of traditional flow analysis systems. Additional features of the strategy presented were low cost, efficiency, high versatility and low reagent consumption comparing to HPLC methodologies usually followed in the case study herein presented. Copyright © 2011 Elsevier B.V. All rights reserved.

  1. Flow injection determination of hydrogen peroxide using catalytic effect of cobalt(II) ion on a dye formation reaction.

    Science.gov (United States)

    Kurihara, Makoto; Muramatsu, Miyuki; Yamada, Mari; Kitamura, Naoya

    2012-07-15

    A novel flow injection photometric method was developed for the determination of hydrogen peroxide in rainwater. This method is based on a cobalt(II)-catalyzed oxidative coupling of 3-methyl-2-benzothiazolinone hydrazone (MBTH) with N-ethyl-N-(2-hydroxy-3-sulfopropyl)-3,5-dimethoxyaniline (DAOS) as a modified Trinder's reagent to produce intensely colored dye (λ(max)=530nm) in the presence of hydrogen peroxide at pH 8.4. In this method, 1,2-dihydroxy-3,5-benzenedisulfonic acid (Tiron) acted as an activator for the cobalt(II)-catalyzed reaction and effectively increased the peak height for hydrogen peroxide. The linear calibration graphs were obtained in the hydrogen peroxide concentration range 5×10(-8) to 2.2×10(-6)mol dm(-3) at a sampling rate of 20h(-1). The relative standard deviations for ten determinations of 2.2×10(-6) and 2×10(-7)mol dm(-3) hydrogen peroxide were 1.1% and 3.7%, respectively. The proposed method was successfully applied to the determination of hydrogen peroxide in rainwater samples and the analytical results agreed fairly well with the results obtained by different two reference methods; peroxidase method and hydrogen peroxide electrode method. Copyright © 2012 Elsevier B.V. All rights reserved.

  2. Determination of hydrogen peroxide in water by chemiluminescence detection, (1). Flow injection type hydrogen peroxide detection system

    International Nuclear Information System (INIS)

    Yamashiro, Naoya; Uchida, Shunsuke; Satoh, Yoshiyuki; Morishima, Yusuke; Yokoyama, Hiroaki; Satoh, Tomonori; Sugama, Junichi; Yamada, Rie

    2004-01-01

    A flow injection type hydrogen peroxide detection system with a sub-ppb detection limit has been developed to determine hydrogen peroxide concentration in water sampled from a high temperature, high pressure hydrogen peroxide water loop. The hydrogen peroxide detector is based on luminol chemiluminescence spectroscopy. A small amount of sample water (20 μl) is mixed with a reagent mixture, an aqueous solution of luminol and Co 2+ catalyst, in a mixing cell which is installed just upstream from the detection cell. The optimum values for pH and the concentrations of luminol and Co 2+ ion have been determined to ensure a lower detectable limit and a higher reproducibility. The photocurrent detected by the detection system is expressed by a linear function of the hydrogen peroxide concentration in the region of lower concentration ([H 2 O 2 ] 2 O 2 ] in the region of higher concentration ([H 2 O 2 ] > 10 ppb). The luminous intensity of luminol chemiluminescence is the highest when pH of the reagent mixture is 11.0. Optimization of the major parameters gives the lowest detectable limit of 0.3 ppb. (author)

  3. Flow Injection Photosensitized Chemiluminescence of Luminol with Cu(II-Rose Bengal: Mechanistic Approach and Vitamin A and C Determination

    Directory of Open Access Journals (Sweden)

    Muhammad Asgher

    2014-01-01

    Full Text Available Rose Bengal photosensitized flow injection chemiluminescence method is reported using luminol-Cu(II for the determination of vitamins A and C in pharmaceutical formulations. The reaction is based on the enhancement effect of analyte in the production of anion radicals of Rose Bengal (RB•− which rapidly interact with dissolved oxygen and generate superoxide anions radicals (O2•− and hydrogen peroxide (H2O2. Highly reactive hydroxyl radicals (•OH were produced via dismutation of H2O2 by catalyst (Cu2+. The generated superoxide anions radicals and hydroxyl radicals thus oxidize luminol in alkaline medium to generate strong chemiluminescence. The limit of detection (3s of the blank, n=6 of vitamins A and C and RB was found to be 0.008, 0.005, and 0.05 μg mL−1, respectively. The sample throughput of 70 h−1 for vitamins A and C and 30 h−1 for RB was found. Calibration curve was linear in the range of 0.05–15, 0.01–20, and 0.1–50 μg mL−1 for vitamins A and C and RB, respectively, with relative standard deviations (RSDs; n=3 in the range 1.6–3.6%. The method was successfully applied to pharmaceutical formulations and the results obtained were in good agreement with the labeled values.

  4. Flow-injection methylene blue-based spectrophotometric method for the determination of peroxide values in edible oils.

    Science.gov (United States)

    Dhaouadi, Anissa; Monser, Lotfi; Sadok, Saloua; Adhoum, Nafaâ

    2006-08-25

    A flow-injection method for measuring the peroxide value (PV, mequiv. O2 kg(-1)) in edible oils is described. The technique is based on spectrophotometric monitoring at 660 nm of methylene blue (MB), generated from leucomethylene blue (LMB) oxidation with peroxides present in oil samples. After being optimized, the method was validated in terms of linearity, precision sensitivity and recovery. Linear calibration graph was obtained in the range 0.1-5 mequiv. O2 kg(-1), with a detection limit (S/N=3) of 0.014 mequiv. O2 kg(-1). The precision of the method (R.S.D., n=9) for within and between-days is better than 1.5% and 2.2%, respectively at 0.4 mequiv. O2 kg(-1). The method was applied successfully to the determination of PV in six edible oil samples, and compared to the classical official method. Using the linear regression test, Student's t-test and variance ratio F-test, there was no significant difference between the compared methods. The proposed method is accurate, simple, cheap and could be used to control edible oil rancidity with a high sample throughputs (30 samples h(-1)).

  5. Detection of Total Phenol in Green and Black Teas by Flow Injection System and Unmodified Screen Printed Electrode

    Science.gov (United States)

    de Mattos, Ivanildo Luiz; Zagal, José Heraclito

    2010-01-01

    A flow injection system using an unmodified gold screen-printed electrode was employed for total phenol determination in black and green teas. In order to avoid passivation of the electrode surface due to the redox reaction, preoxidation of the sample was realized by hexacyanoferrate(III) followed by addition of an EDTA solution. The complex formed in the presence of EDTA minimizes or avoids polymerization of the oxidized phenols. The previously filtered tea sample and hexacyanoferrate(III) reagent were introduced simultaneously into two-carrier streams producing two reproducible zones. At confluence point, the pre-oxidation of the phenolic compounds occurs while this zone flows through the coiled reactor and receives the EDTA solution before phenol detection. The consumption of ferricyanide was monitorized at 360 mV versus Ag/AgCl and reflected the total amount of phenolic compounds present in the sample. Results were reported as gallic acid equivalents (GAEs). The proposed system is robust, versatile, environmentally-friendly (since the reactive is used only in the presence of the sample), and allows the analysis of about 35–40 samples per hour with detection limit = 1 mg/L without the necessity for surface cleaning after each measurement. Precise results are in agreement with those obtained by the Folin-Ciocalteu method. PMID:21461407

  6. FLOW INJECTION ANALYSIS SYSTEM COUPLED WITH ICP-EOS FOR DETERMINATION OF SOME METALLIC ELEMENTS IN DRINKING WATER

    Directory of Open Access Journals (Sweden)

    Cristina Dinu

    2009-06-01

    Full Text Available The European Drinking Water Directive (98/83/EC, transposed in Romanian Legislation as Low 458/2002, amended by Low 311/2004, imposes the limit of concentration for metallic elements in water intended for human consumption. The toxic metals arsenic and selenium are among these elements and the limit value is 10 μg/L. In the paper there are presented the working conditions for determination of As and Se from drinking water using modern techniques based on the fl ow injection-hydride generation with the inductively coupled plasma atomic emission spectrometry (FIAS-ICP-EOS. The analyses were performed on Optima 5300 DV Perkin Elmer equipment with FIAS 400 Flow Injection System, Perkin Elmer type. For the hydride generation two types of solution were used: 10% (v/v HCl as a carrier solution and 0.2 % NaBH4 in 0.05%NaOH solution as a reducing agent [1]. The treatment step of the samples and standard solutions consisted in reducing with mixed solutions of KI and ascorbic acid in acidic condition (HCl for As and only with HCl and high temperature for Se [2,3]. The paper contains the characteristic parameters of the methods, such as: low detection limit, quantifi cation limit, repeatability, precision, recovery, which were evaluated using Certifi ed Reference Materials for each element.

  7. Determination of enalapril maleate and atenolol in their pharmaceutical products and in biological fluids by flow-injection chemiluminescence.

    Science.gov (United States)

    Al-Arfaj, Nawal A; Al-Abdulkareem, Eman A; Aly, Fatma A

    2009-01-01

    A chemiluminescent method using flow injection (FI) was investigated for rapid and sensitive determination of enalapril maleate and atenolol, which are used in the treatment of hypertension. The method is based on the sensitizing effect of these drugs on the Ce(IV)-sulfite reaction. The different experimental parameters affecting the chemiluminescence (CL) intensity were carefully studied and incorporated into the procedure. The method permitted the determination of 0.01-3.0 microg mL(-1) of enalapril maleate in bulk form with correlation coefficient r = 0.99993, lower limit of detection (LOD) 0.0025 microg mL(-1) (S/N = 2) and lower limit of quantitation (LOQ) 0.01 microg mL(-1). The linearity range of atenolol in bulk form was 0.01-2.0 microg mL(-1) (r = 0.99989) with LOD of 0.0003 microg mL(-1) (S/N = 2) and LOQ of 0.01 microg mL(-1). In biological fluids the linearity range of enalapril maleate was 0.1-2.0 microg mL(-1) in both urine and serum, and for atenolol the linearity range was 0.1-1.0 microg mL(-1) in both urine and serum. The method was also applied to the determination of the drugs in their pharmaceutical preparations.

  8. A metallic cobalt electrode for the indirect potentiometric determination of calcium and magnesium in natural waters using flow injection analysis.

    Science.gov (United States)

    Chen, Z; Adams, M A

    1998-11-01

    A flow injection analysis of Ca(2+) and Mg(2+) using indirect potentiometric detection in natural waters is proposed, where Ca(2+) or Mg(2+) are injected into a buffer carrier containing phosphate, resulting in the formation of Ca(3)(PO(4))(2) or Mg(3)(PO(4))(2). The consequent reduction in free phosphate in the carrier solution is detected using a metallic cobalt wire electrode. Indirect electrode response was used and the experimental conditions affecting electrode response were optimized. Responses were linear in the concentration range 5x10(-4) to 5x10(-3) M with a detection limit of 1x10(-5) M in 20 mM phosphate buffer at pH 8.0. The relative standard derivation at 1 mM of Ca(2+) and Mg(2+) were 3.9 and 3.7% (n=10), respectively. EGTA and 8-hydroxyquinoline were used as the masking agents for Ca(2+) and Mg(2+), respectively. Concentrations of Ca(2+) and Mg(2+) in natural waters were successfully determined by the proposed method.

  9. Conventional and planar chip sensors for potentiometric assay of uric acid in biological fluids using flow injection analysis.

    Science.gov (United States)

    Kamel, Ayman H

    2007-10-18

    The potentiometric response properties of several PVC-based membrane sensors using phthalocyanine complexes of cobalt(II) (CoPC) and Fe(II) (FePC) as anion carriers, towards uric acid were constructed and characterized. The sensors demonstrated fast near-Nernstian response for uric acid over the concentration ranges 9.1 x 10(-6) to 9.1 x 10(-2) and 3.1 x 10(-5) to 3.1 x 10(-2)M with detection limits 0.67 and 2.85 microg mL(-1) over pH 6.5-8 for CoPC and FePC based membrane sensors plasticized with o-NPOE and 1% TDMAC, respectively. A novel solid-state planar chip urate sensor was developed, characterized according to IUPAC recommendations, easily used in a single channel wall-jet flow injection system and compared with a tubular detector. The intrinsic characteristics of the detectors in a low dispersion manifold were determined and compared with data obtained under hydrodynamic mode of operation. Validation of the assay methods with the proposed sensors by measuring the lower limit, range, accuracy, precision, repeatability and between-day-variability revealed good performance characteristics confirming applicability for continuous determination of uric acid. The sensors were used for determining urate in biological fluids at an input rate of 50 samples per hour. The results compare favorably with data obtained by the standard spectrophotometry.

  10. Flow injection potentiometric system for the simultaneous determination of inositol phosphates and phosphate: phosphorus nutritional evaluation on seeds and grains.

    Science.gov (United States)

    Parra, Aleix; Ramon, Meritxell; Alonso, Julián; Lemos, Sherlan G; Vieira, Edivan C; Nogueira, Ana R A

    2005-10-05

    A simple flow injection potentiometric (FIP) system, which uses a tubular cobalt electrode, has been developed for phosphorus nutritional evaluation of seeds and grains. Inorganic phosphorus, P(i), is determined using a 1 x 10(-2) mol.L(-1) potassium phthalate buffer solution adjusted at pH 4. A sensitivity of 47 mV/decade and an operating range from 10 to 1000 mg.L(-1) (1 x 10(-4)-1 x 10(-2) M) of dihydrogen phosphate are obtained. The inositol phosphates amount, which is referred to the organic phosphorus, P(org), is directly determined from extracts using a 1 x 10(-2) mol.L(-1) Tris-HCl buffer solution adjusted at pH 8. A sensitivity of 127 mV/decade and an operating range of 10-1000 mg.L(-1) (2.5 x 10(-4)-5 x 10(-3) M) of P(org) (expressed as inositol hexakisphosphoric acid monocalcium) are achieved. Some samples of seed and grain are analyzed by an ICP-OES and a spectrophotometric method to compare results to the developed flow system; no significant differences at the 95% confidence level are observed using a paired t test. Other samples such as animal nursing feed, soybean meal, and corn are also analyzed with the proposed FIP system, showing a good correlation to the ICP-OES values.

  11. Flow injection determination of Se in dietary supplements using TiO2 mediated ultraviolet-photochemical volatile species generation

    Science.gov (United States)

    Nováková, E.; Linhart, O.; Červený, V.; Rychlovský, P.; Hraníček, J.

    2017-08-01

    This paper proposes a method for determination of selenium content in samples of dietary supplements using TiO2 mediated UV-photochemical vapor generation with quartz furnace atomic spectrometric detection. The flow-injection method was optimized for determination of selenium in the form of selenite or selenate ions. The limits of detection of the proposed method are 0.89 ng mL- 1 and 0.68 ng mL- 1 for selenite and selenate, respectively. Extraction in neutral medium was used for the leaching of selenate and NaOH solution was used for the leaching of selenite. The methods accuracy was verified against the declared amounts of Se in five different samples of over-the-counter dietary supplements and on NIST SRM 3280. The method was also compared to results achieved with determination by electrothermal atomization atomic absorption spectrometry following microwave decomposition. The recovery of selenium during sample preparation was tested by spiking the tablets prior to extraction and estimated to be approximately 100%. An interference study has been carried out to estimate the effect of concomitant elements on the methods accuracy.

  12. Flow Injection Analysis with Electrochemical Detection for Rapid Identification of Platinum-Based Cytostatics and Platinum Chlorides in Water

    Directory of Open Access Journals (Sweden)

    Marketa Kominkova

    2014-02-01

    Full Text Available Platinum-based cytostatics, such as cisplatin, carboplatin or oxaliplatin are widely used agents in the treatment of various types of tumors. Large amounts of these drugs are excreted through the urine of patients into wastewaters in unmetabolised forms. This phenomenon leads to increased amounts of platinum ions in the water environment. The impacts of these pollutants on the water ecosystem are not sufficiently investigated as well as their content in water sources. In order to facilitate the detection of various types of platinum, we have developed a new, rapid, screening flow injection analysis method with electrochemical detection (FIA-ED. Our method, based on monitoring of the changes in electrochemical behavior of analytes, maintained by various pH buffers (Britton-Robinson and phosphate buffer and potential changes (1,000, 1,100 and 1,200 mV offers rapid and cheap selective determination of platinum-based cytostatics and platinum chlorides, which can also be present as contaminants in water environments.

  13. Preconcentration and determination of some lanthanide elements with immobilized bacteria by flow injection inductively coupled plasma atomic emission spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Maquieira, A.; Elmahadi, H.; Puchades, R. [Universidad Politecnica de Valencia (Spain)

    1996-02-01

    The on-line combination of flow injection column preconcentration with sequential inductively coupled plasma atomic emission spectrometry is shown to provide an enrichment factor of 36 for La{sup 3+}, 34 for Ce{sup 3+} and 51 for Nd{sup 3+}, at 1 {mu}g ml{sup -1} for 5 ml of sample. The significant improvement in the (3s) detection limit by preconcentration compared with that without preconcentration demonstrates the efficiency of preconcentration with the bacterium Spirulina platensis immobilized on controlled-pore glass. Recovery of all the lanthanide cations is quantitative and the capacity was calculated. Practical application of the method was demonstrated by the determination of La{sup 3+} and Nd{sup 3+} impurities in a cerium(III) nitrate reagent. Adsorption isotherm studies were used to describe the mechanisms and the nature of the column binding sites. Isotherm plots showed a Langmuirian shape for La{sup 3+} and an anti-Lanmuirian shape for Ce{sup 3+} and Nd{sup 3+}. Equilibrium constants were also calculated. (Author).

  14. Down scaled Kjeldahl digestion and flow injection conductometric system for determination of protein content in some traditional northern Thai foods.

    Science.gov (United States)

    Yanu, Pattama; Jakmunee, Jaroon

    2017-09-01

    A flow injection conductometric (FIC) system for determination of total Kjeldahl nitrogen (TKN) was developed for estimating total protein content in food. A small scale Kjeldahl digestion was performed with a short digestion time of only 20min. The digested solution was injected into the FIC system, and TKN was converted to ammonia gas in an alkaline donor stream of the system. The gas diffused through a membrane and dissolved into an acceptor stream causing an increase in conductivity as detected by a detector and recorded as a peak. Under the optimum condition, a linear calibration graph in the range of 4.00-100.00mgL -1 was obtained with LOD of 0.05mgL -1 . A good precision (0.04% RSD, n=11, 30.00mgNL -1 ) and high sample throughput of 72h -1 was achieved. The method was applied for determination of protein in some traditional northern Thai foods, revealing that they are good sources of proteins. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Spectrophotometric flow-injection determination of sulphite in white wines involving gas diffusion through a concentric tubular membrane

    Directory of Open Access Journals (Sweden)

    Melo Denise

    2003-01-01

    Full Text Available A flow-injection system is proposed for the spectrophotometric determination of sulphite in white wines. The method involves analyte conversion to SO2, gas diffusion through a Teflon® semi-permeable membrane, collection into an alkaline stream (pH 8, reaction with Malachite green (MG and monitoring at 620 nm. With a concentric tubular membrane, the system design was simplified. Influence of reagent concentrations, pH of donor and acceptor streams, temperature, timing, surfactant addition and presence of potential interfering species of the wine matrix were investigated. A pronounced (ca. 100% enhancement in sensitivity was noted by adding cetylpyridinium chloride (CPC. The proposed system is robust and baseline drift is not observed during 4 h operating periods. Only 400 muL of sample and 0.32 mg MG are required per determination. The system handles 30 samples per hour, yielding precise results (r.s.d. < 0.015 for 1.0 - 20.0 mg L-1 SO2 in agreement with those obtained by an alternative procedure.

  16. Flow-Injection Determination of Thiabendazole Fungicide in Water Samples Using a Diperiodatocuprate(III)-Sulfuric Acid-Chemiluminescence System.

    Science.gov (United States)

    Asghar, Mohammad; Yaqoob, Mohammad; Munawar, Nusrat; Nabi, Abdul

    2016-01-01

    Chemiluminescence (CL) with a flow-injection method is reported for the determination of thiabendazole (TBZ) fungicide based on its enhancement effect on diperiodatocuprate(III) (DPC)-sulfuric acid-CL system. The calibration graph was linear in the concentration range of 1 - 2000 μg L(-1) (R(2) = 0.9999, n = 8) with a limit of detection (S/N = 3) of 0.3 μg L(-1). The injection throughput was 160 h(-1) with relative standard deviations (RSD, n = 4) of 1.1 - 2.9% in the concentration range studied. The experimental variables e.g., reagents concentrations, flow rates, sample volume, and PMT voltage were optimized, and the potential interferences were investigated individually. The method was successfully applied to the determination of TBZ in water samples showing good agreement and recovery in the range of 92 ± 2.2 - 108 ± 3% (n = 3) using dispersive liquid-liquid micro-extraction (DLLME). The possible CL reaction mechanism for DPC-sulfuric acid-TBZ is also discussed.

  17. Novel amperometric glucose biosensor based on MXene nanocomposite

    KAUST Repository

    Rakhi, R. B.

    2016-11-10

    A biosensor platform based on Au/MXene nanocomposite for sensitive enzymatic glucose detection is reported. The biosensor leverages the unique electrocatalytic properties and synergistic effects between Au nanoparticles and MXene sheets. An amperometric glucose biosensor is fabricated by the immobilization of glucose oxidase (GOx) enzyme on Nafion solubilized Au/ MXene nanocomposite over glassy carbon electrode (GCE). The biomediated Au nanoparticles play a significant role in facilitating the electron exchange between the electroactive center of GOx and the electrode. The GOx/Au/MXene/Nafion/GCE biosensor electrode displayed a linear amperometric response in the glucose concentration range from 0.1 to 18 mM with a relatively high sensitivity of 4.2 μAmM−1 cm−2 and a detection limit of 5.9 μM (S/N = 3). Furthermore, the biosensor exhibited excellent stability, reproducibility and repeatability. Therefore, the Au/MXene nanocomposite reported in this work is a potential candidate as an electrochemical transducer in electrochemical biosensors.

  18. Amperometric immunosensor for rapid detection of Mycobacterium tuberculosis

    Science.gov (United States)

    Hiraiwa, Morgan; Kim, Jong-Hoon; Lee, Hyun-Boo; Inoue, Shinnosuke; Becker, Annie L.; Weigel, Kris M.; Cangelosi, Gerard A.; Lee, Kyong-Hoon; Chung, Jae-Hyun

    2015-05-01

    Tuberculosis (TB) has been a major public health problem, which can be better controlled by using accurate and rapid diagnosis in low-resource settings. A simple, portable, and sensitive detection method is required for point-of-care (POC) settings. This paper studies an amperometric biosensor using a microtip immunoassay for a rapid and low-cost detection of Mycobacterium tuberculosis (MTB) in sputum. MTB in sputum is specifically captured on the functionalized microtip surface and detected by electric current. According to the numerical study, the current signal on the microtip surface is linearly changed with increasing immersion depth. Using a reference microtip, the immersion depth is compensated for a sensing microtip. On the microtip surface, target bacteria are concentrated and organized by a coffee-ring effect, which amplifies the electric current. To enhance the signal-to-noise ratio, both the sample processing and rinsing steps are presented with the use of deionized water as a medium for the amperometric measurement. When applied to cultured MTB cells spiked into human sputum, the detection limit was 100 CFU mL-1, comparable to a more labor-intensive fluorescence detection method reported previously.

  19. Thick-film textile-based amperometric sensors and biosensors.

    Science.gov (United States)

    Yang, Yang-Li; Chuang, Min-Chieh; Lou, Shyh-Liang; Wang, Joseph

    2010-06-01

    The incorporation of amperometric sensors into clothing through direct screen-printing onto the textile substrate is described. Particular attention is given to electrochemical sensors printed directly on the elastic waist of underwear that offers tight direct contact with the skin. The textile-based printed carbon electrodes have a well-defined appearance with relatively smooth conductor edges and no apparent defects or cracks. Convenient voltammetric and chronoamperometric measurements of 0-3 mM ferrocyanide, 0-25 mM hydrogen peroxide, and 0-100 muM NADH have been documented. The favorable electrochemical behavior is maintained under folding or stretching stress, relevant to the deformation of clothing. The electrochemical performance and tolerance to mechanical stress are influenced by the physical characteristics of the textile substrate. The results indicate the potential of textile-based screen-printed amperometric sensors for future healthcare, sport or military applications. Such future applications would benefit from tailoring the ink composition and printing conditions to meet the specific requirements of the textile substrate.

  20. Flow Injection Analysis

    DEFF Research Database (Denmark)

    Hansen, Elo Harald

    2004-01-01

    This chapter provides an introduction to automated chemical analysis, which essentially can be divided into two groups: batch assays, where the solution is stationary while the container is moved through a number of stations where various unit operations performed; and continuous-flow procedures,......, but it permits thr execution of novel and unique analytical procedures which are difficult or even impossible by conventional means. The performance and applicability of FIA, SI and LOV are illustrated by a series of practical examples....... FIA is based on the creation of a concentration gradient of the injected sample solution and on reproducible and precise timing of all events, it allows exploitation of a transient read-out. This in turn implies that not only does FIA allow the augmentation of existing analytical techniques...

  1. Flow Injection Analysis

    DEFF Research Database (Denmark)

    Hansen, Elo Harald

    1998-01-01

    Learning objectives:* To provide an introduction to automated assays* To describe the basic principles of FIA * To demonstrate the capabilities of FIA in relation to batch assays and conventional continuous flow systems* To show that FIA allows one to augment existing analytical techniques* To show...

  2. Lanthanides determination in red wine using ultrasound assisted extraction, flow injection, aerosol desolvation and ICP-MS

    Energy Technology Data Exchange (ETDEWEB)

    Bentlin, Fabrina R.S. [Universidade Federal do Rio Grande do Sul, Av. Bento Goncalves 9500, 91501.970 Porto Alegre, RS (Brazil); Santos, Clarissa M.M. dos; Flores, Erico M.M. [Departamento de Quimica Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS (Brazil); Pozebon, Dirce, E-mail: dircepoz@iq.ufrgs.br [Universidade Federal do Rio Grande do Sul, Av. Bento Goncalves 9500, 91501.970 Porto Alegre, RS (Brazil)

    2012-01-13

    Highlights: Black-Right-Pointing-Pointer Ultrasound was investigated and applied for red wine samples preparation. Black-Right-Pointing-Pointer Aliquots of 50 {mu}L of sample were nebulized and transported to plasma. Black-Right-Pointing-Pointer FI and pneumatic nebulization/aerosol desolvation were used. Black-Right-Pointing-Pointer LODs of the ICP-MS method for lanthanides determination were at ng L{sup -1} level. Black-Right-Pointing-Pointer Lanthanides concentration allowed red wines classification. - Abstract: This paper deals with the determination of the fourteen naturally occurring elements of the lanthanide series in red wine. Ultrasound (US) was used for sample preparation prior lanthanides determination using ICP-MS. Flow injection (FI) and pneumatic nebulization/aerosol desolvation were used for nebulization of aliquots of 50 {mu}L of sample and its subsequent transportation to plasma. Sample preparation procedures, matrix interference and time of sonication were evaluated. Better results for lanthanides in red wine were obtained by sonication with US probe for 90 s and sample 10-fold diluted. The limits of detection of La, Ce, Nd, Sm, Gd, Pr, Eu, Tb, Dy, Ho, Er, Tm, Lu and Yb were 6.57, 10.8, 9.97, 9.38, 2.71, 1.29, 1.22, 0.52, 2.35, 0.96, 2.30, 0.45, 0.24 and 1.35 ng L{sup -1}, respectively. Red wines of different varieties from three countries of South America were discriminated according to the country of origin by means of multivariate analysis of lanthanides concentration.

  3. A flow injection analysis system with encapsulated high-density Saccharomyces cerevisiae cells for rapid determination of biochemical oxygen demand.

    Science.gov (United States)

    Seo, Kyo Seong; Choo, Kwang Ho; Chang, Ho Nam; Park, Joong Kon

    2009-05-01

    The biochemical oxygen demand (BOD) determination was studied using a novel flow injection analysis (FIA) system with encapsulated Saccharomyces cerevisiae cells and an oxygen electrode and was compared with conventional 5-day BOD tests. S. cerevisiae cells were packed in a calcium alginate capsule at a dry cell weight of 250 g/l of capsule core. The level of dissolved oxygen (DO) was reduced due to the enhanced respiratory activity of the microbial cells when the injected nutrient passed through the bioreactor. The decrease in DO (DeltaDO) was intensified with the amount of microbial cells packed in the bioreactor. However, the specific DeltaDO decreased as the amount of cells loaded in the bioreactor increased. The DeltaDO value was dependent on the pH and temperature of the mobile phase and reached its maximum value at 35 degrees C and pH 7-8. Also, DeltaDO became larger at longer response times as the flow rate of the mobile phase decreased. The measurement of DeltaDO was repeated more than six times consecutively using a 20-ppm standard glucose and glutamic acid solution, which confirmed the reproducibility with a standard deviation of 0.95%. A strong linear correlation between DeltaDO and BOD was also observed. The 5-day BOD values of actual water and wastewater samples were in accordance with the BOD values obtained by this FIA method using encapsulated S. cerevisiae cells. Unlike the cell-immobilized bead system, there was no contamination of the bioreactor resulting from any leak of yeast cells from the sensor capsules during BOD measurements.

  4. Surface-enhanced Raman detection of RNA and DNA bases following flow-injection analysis or HPLC separation

    Science.gov (United States)

    Cotton, Therese M.; Sheng, Rong-Sheng; Ni, Fan

    1990-11-01

    The goal of this study is to develop Surface-enhanced Raman scattering (SERS) detection methods for flow injection analysis (FIA) and high performance liquid chromatography (HPLC). Nucleic acid bases have been chosen for analysis because of their importance in life processes. The advantages to the use of SERS-based detection include its sensitivity, specificity and versatility. With the development of improved methodology, the detection limits should be comparable to UV spectroscopy. However, the specificity is considerably superior to that obtained with electronic spectroscopy in that the Raman spectrum provides a molecular fingerprint of the individual analytes. Raman spectroscopy is very versatile: aqueous samples, gases and solids can be analyzed with equal facility. The results presented here demonstrate that SERS can be used as a detection method for both FIA and HPLC detection. In the following experiments Ag sols have been used as the active substrate. The effect of various parameters such as temperature, pH, flow rate, and the nature of the interface between the HPLC system and the Raman spectrometer have been examined. One of the most significant findings is that the temperature of the Ag sol/HPLC effluent mixture has a dramatic effect on the SERS intensities. This effect is a result of increased colloid aggregation at higher temperatures. Aggregation is known to produce greater enhancement in SERS and proceeds much more rapidly at elevated temperatures. An increase in the temperature of the Ag sol enables SERS detection under flowing conditions and in real time. This is a substantial improvement over many of the previous attempts to interface SERS detection to FIA or HPLC. In most of the previous studies, it was necessary to stop the flow as the analyte eluted from the chromatogram and measure the SERS spectra under static conditions.

  5. Lanthanides determination in red wine using ultrasound assisted extraction, flow injection, aerosol desolvation and ICP-MS

    International Nuclear Information System (INIS)

    Bentlin, Fabrina R.S.; Santos, Clarissa M.M. dos; Flores, Érico M.M.; Pozebon, Dirce

    2012-01-01

    Highlights: ► Ultrasound was investigated and applied for red wine samples preparation. ► Aliquots of 50 μL of sample were nebulized and transported to plasma. ► FI and pneumatic nebulization/aerosol desolvation were used. ► LODs of the ICP-MS method for lanthanides determination were at ng L −1 level. ► Lanthanides concentration allowed red wines classification. - Abstract: This paper deals with the determination of the fourteen naturally occurring elements of the lanthanide series in red wine. Ultrasound (US) was used for sample preparation prior lanthanides determination using ICP-MS. Flow injection (FI) and pneumatic nebulization/aerosol desolvation were used for nebulization of aliquots of 50 μL of sample and its subsequent transportation to plasma. Sample preparation procedures, matrix interference and time of sonication were evaluated. Better results for lanthanides in red wine were obtained by sonication with US probe for 90 s and sample 10-fold diluted. The limits of detection of La, Ce, Nd, Sm, Gd, Pr, Eu, Tb, Dy, Ho, Er, Tm, Lu and Yb were 6.57, 10.8, 9.97, 9.38, 2.71, 1.29, 1.22, 0.52, 2.35, 0.96, 2.30, 0.45, 0.24 and 1.35 ng L −1 , respectively. Red wines of different varieties from three countries of South America were discriminated according to the country of origin by means of multivariate analysis of lanthanides concentration.

  6. Electrochemical flow injection analysis of hydrazine in an excess of an active pharmaceutical ingredient: achieving pharmaceutical detection limits electrochemically.

    Science.gov (United States)

    Channon, Robert B; Joseph, Maxim B; Bitziou, Eleni; Bristow, Anthony W T; Ray, Andrew D; Macpherson, Julie V

    2015-10-06

    The quantification of genotoxic impurities (GIs) such as hydrazine (HZ) is of critical importance in the pharmaceutical industry in order to uphold drug safety. HZ is a particularly intractable GI and its detection represents a significant technical challenge. Here, we present, for the first time, the use of electrochemical analysis to achieve the required detection limits by the pharmaceutical industry for the detection of HZ in the presence of a large excess of a common active pharmaceutical ingredient (API), acetaminophen (ACM) which itself is redox active, typical of many APIs. A flow injection analysis approach with electrochemical detection (FIA-EC) is utilized, in conjunction with a coplanar boron doped diamond (BDD) microband electrode, insulated in an insulating diamond platform for durability and integrated into a two piece flow cell. In order to separate the electrochemical signature for HZ such that it is not obscured by that of the ACM (present in excess), the BDD electrode is functionalized with Pt nanoparticles (NPs) to significantly shift the half wave potential for HZ oxidation to less positive potentials. Microstereolithography was used to fabricate flow cells with defined hydrodynamics which minimize dispersion of the analyte and optimize detection sensitivity. Importantly, the Pt NPs were shown to be stable under flow, and a limit of detection of 64.5 nM or 0.274 ppm for HZ with respect to the ACM, present in excess, was achieved. This represents the first electrochemical approach which surpasses the required detection limits set by the pharmaceutical industry for HZ detection in the presence of an API and paves the wave for online analysis and application to other GI and API systems.

  7. Flow injection analysis of organic peroxide explosives using acid degradation and chemiluminescent detection of released hydrogen peroxide.

    Science.gov (United States)

    Mahbub, Parvez; Zakaria, Philip; Guijt, Rosanne; Macka, Mirek; Dicinoski, Greg; Breadmore, Michael; Nesterenko, Pavel N

    2015-10-01

    The applicability of acid degradation of organic peroxides into hydrogen peroxide in a pneumatically driven flow injection system with chemiluminescence reaction with luminol and Cu(2+) as a catalyst (FIA-CL) was investigated for the fast and sensitive detection of organic peroxide explosives (OPEs). The target OPEs included hexamethylene triperoxide diamine (HMTD), triacetone triperoxide (TATP) and methylethyl ketone peroxide (MEKP). Under optimised conditions maximum degradations of 70% and 54% for TATP and HMTD, respectively were achieved at 162 µL min(-1), and 9% degradation for MEKP at 180 µL min(-1). Flow rates were precisely controlled in this single source pneumatic pressure driven multi-channel FIA system by model experiments on mixing of easily detectable component solutions. The linear range for detection of TATP, HMTD and H2O2 was 1-200 µM (r(2)=0.98-0.99) at both flow rates, while that for MEKP was 20-200 µM (r(2)=0.97) at 180 µL min(-1). The detection limits (LODs) obtained were 0.5 µM for TATP, HMTD and H2O2 and 10 µM for MEKP. The detection times varied from 1.5 to 3 min in this FIA-CL system. Whilst the LOD for H2O2 was comparable with those reported by other investigators, the LODs and analysis times for TATP and HMTD were superior, and significantly, this is the first time the detection of MEKP has been reported by FIA-CL. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. Evaluation of permselective membranes for optimization of intracerebral amperometric glutamate biosensors

    NARCIS (Netherlands)

    Wahono, N.; Qin, S.; Oomen, P.; Cremers, T. I. F.; de Vries, M. G.; Westerink, B. H. C.

    2012-01-01

    Monitoring of extracellular brain glutamate concentrations by intracerebral biosensors is a promising approach to further investigate the role of this important neurotransmitter. However, amperometric biosensors are typically hampered by Faradaic interference caused by the presence of other

  9. Simulation Study of Nano Aqueous Flow Sensor Based on Amperometric Measurement

    Directory of Open Access Journals (Sweden)

    Zhengguo Lou

    2006-04-01

    Full Text Available In this paper, a novel nano aqueous flow sensor which consists of two closelyspaced amperometric sensors is investigated by digital simulation. The simulation resultsindicate that the ratio of the responses of two closely spaced amperometric sensors is onlyrelated to flow rates in the channel, insensitive to the analyte concentration in the solution.By comparing the output of two amperometric sensors, the flow rate in the channel can bededuced. It is not necessary to determine the analyte concentration in advance. Thesimulation results show it is able to detect flow rate by in the range of several nano-liters perminute when the distance between the working electrodes of two amperometric sensors is200 nm and the cross-section of the channel is 1 μm x 1 μm.

  10. The procedure of ethanol determination in wine by enzyme amperometric biosensor

    Directory of Open Access Journals (Sweden)

    Dzyadevych S. V.

    2009-08-01

    Full Text Available Aim. Development of the procedure of ethanol determination in wine by an enzyme amperometric biosensor. Methods. The amperometric biosensor method of ethanol analysis has been used in this work. Results. The paper presents comparative analysis of two methods of alcohol oxidase (AO immobilization for development of amperometric biosensor for ethanol determination in wine. The method of AO immobilization in glutaraldehyde vapour was chosen as optimal for this purpose. The selectivity, operational and storage stability, and pH-optimum for operation of the created biosensor were determined. The procedure of ethanol determination in wine by amperometric biosensor on the basis of platinum printed electrode SensLab and AO was optimized. The analysis of ethanol concentration in wine and must samples was carried out using the developed high-stable biosensor. A good correlation between the data obtained by the biosensor and densitometry methods was shown. Conclusion. The proposed method of ethanol analysis could be used in wine production

  11. Amperometric and impedance monitoring systems for biomedical applications

    CERN Document Server

    Punter-Villagrasa, Jaime; del Campo, Francisco J; Miribel, Pere

    2017-01-01

    The book presents the conception and realization of a pervasive electronic architecture for electrochemical applications, focusing on electronic instrumentation design and device development, particularly in electrochemical Point-of-Care and Lab-on-a-Chip devices, covering examples based on amperometric (DC) and impedance detection (AC) techniques. The presented electronics combine tailored front-end instrumentation and back-end data post-processing, enabling applications in different areas, and across a variety of techniques, analytes, transducers and environments. It addresses how the electronics are designed and implemented with special interest in the flow process: starting from electronic circuits and electrochemical biosensor design to a final validation and implementation for specific applications. Similarly, other important aspects are discussed throughout the book, such as electrochemical techniques, different analytes, targets, electronics reliability and robustness. The book also describes the use ...

  12. On-line Speciation of Cr(III) and Cr(VI) by Flow Injection Analysis With Spectrophotometric Detection and Chemometrics

    DEFF Research Database (Denmark)

    Diacu, Elena; Andersen, Jens Enevold Thaulov

    2003-01-01

    A flow injection system has been developed, for on-line speciation. of Cr(III) and Cr(VI) by the Diphenylcarbazide (DPC) method with H2O2 oxidation followed by spectrophotometric detection at the 550 nm wavelength. The data thus obtained were subjected to a chemometric analysis (PLS), which showe....../L and a maximum sampling frequency of 120 injections per hour were obtained, excluding calculations and sample pre-treatments....

  13. Application of a novel metabolomic approach based on atmospheric pressure photoionization mass spectrometry using flow injection analysis for the study of Alzheimer's disease.

    Science.gov (United States)

    González-Domínguez, Raúl; García-Barrera, Tamara; Gómez-Ariza, José Luis

    2015-01-01

    The use of atmospheric pressure photoionization is not widespread in metabolomics, despite its considerable potential for the simultaneous analysis of compounds with diverse polarities. This work considers the development of a novel analytical approach based on flow injection analysis and atmospheric pressure photoionization mass spectrometry for rapid metabolic screening of serum samples. Several experimental parameters were optimized, such as type of dopant, flow injection solvent, and their flows, given that a careful selection of these variables is mandatory for a comprehensive analysis of metabolites. Toluene and methanol were the most suitable dopant and flow injection solvent, respectively. Moreover, analysis in negative mode required higher solvent and dopant flows (100 µl min(-1) and 40 µl min(-1), respectively) compared to positive mode (50 µl min(-1) and 20 µl min(-1)). Then, the optimized approach was used to elucidate metabolic alterations associated with Alzheimer's disease. Thereby, results confirm the increase of diacylglycerols, ceramides, ceramide-1-phosphate and free fatty acids, indicating membrane destabilization processes, and reduction of fatty acid amides and several neurotransmitters related to impairments in neuronal transmission, among others. Therefore, it could be concluded that this metabolomic tool presents a great potential for analysis of biological samples, considering its high-throughput screening capability, fast analysis and comprehensive metabolite coverage. Copyright © 2014 Elsevier B.V. All rights reserved.

  14. Evaluation of flow-injection tandem mass spectrometry for rapid and high-throughput quantitative determination of B vitamins in nutritional supplements.

    Science.gov (United States)

    Bhandari, Deepak; Van Berkel, Gary J

    2012-08-29

    The use of flow-injection electrospray ionization tandem mass spectrometry for rapid and high-throughput mass spectral analysis of selected B vitamins, viz., B1, B2, B3, B5, and B6, in nutritional formulations was demonstrated. A simple and rapid (~5 min) in-tube sample preparation was performed. Automated flow injection introduced 1 μL of the extracts directly into the mass spectrometer ion source without chromatographic separation. Sample-to-sample analysis time was 60 s. Quantitative capabilities of the flow-injection analysis were tested using the method of standard additions and SRM 3280. The quantity determined for each B vitamin in SRM 3280 was within the statistical range provided for the respective certified values. This approach was also applied to two different commercial vitamin supplement tablets and proved to be successful in the quantification of the selected B vitamins, as evidenced by an agreement with the label values and the results obtained using isotope dilution liquid chromatography/mass spectrometry.

  15. Evaluation of Flow-Injection Tandem Mass Spectrometry for Rapid and High-Throughput Quantitative Determination of B-Vitamins in Nutritional Supplements

    Energy Technology Data Exchange (ETDEWEB)

    Bhandari, Deepak [ORNL; Van Berkel, Gary J [ORNL

    2012-01-01

    The use of flow-injection electrospray ionization tandem mass spectrometry for rapid and high-throughput mass spectral analysis of selected B-vitamins, viz. B1, B2, B3, B5, and B6, in nutritional formulations was demonstrated. A simple and rapid (~5 min) in-tube sample preparation was performed by adding extraction solvent to a powdered sample aliquot followed by agitation, centrifugation, and filtration to recover an extract for analysis. Automated flow injection introduced 1 L of the extracts directly into the mass spectrometer ion source without chromatographic separation. Sample-to-sample analysis time was 60 s representing significant improvement over conventional liquid chromatography approaches which typically require 25-45 min, and often require more significant sample preparation procedures. Quantitative capabilities of the flow-injection analysis were tested using the method of standard additions and NIST standard reference material (SRM 3280) multivitamin/multielement tablets. The quantity determined for each B-vitamin in SRM 3280 was within the statistical range provided for the respective certified values. The same sample preparation and analysis approach was also applied to two different commercial vitamin supplement tablets and proved to be successful in the quantification of the selected B-vitamins as evidenced by an agreement with the labels values and the results obtained using isotope dilution liquid chromatography/mass spectrometry.

  16. Establish an automated flow injection ESI-MS method for the screening of fragment based libraries: Application to Hsp90.

    Science.gov (United States)

    Riccardi Sirtori, Federico; Caronni, Dannica; Colombo, Maristella; Dalvit, Claudio; Paolucci, Mauro; Regazzoni, Luca; Visco, Carlo; Fogliatto, Gianpaolo

    2015-08-30

    ESI-MS is a well established technique for the study of biopolymers (nucleic acids, proteins) and their non covalent adducts, due to its capacity to detect ligand-target complexes in the gas phase and allows inference of ligand-target binding in solution. In this article we used this approach to investigate the interaction of ligands to the Heat Shock Protein 90 (Hsp90). This enzyme is a molecular chaperone involved in the folding and maturation of several proteins which has been subjected in the last years to intensive drug discovery efforts due to its key role in cancer. In particular, reference compounds, with a broad range of dissociation constants from 40pM to 100μM, were tested to assess the reliability of ESI-MS for the study of protein-ligand complexes. A good agreement was found between the values measured with a fluorescence polarization displacement assay and those determined by mass spectrometry. After this validation step we describe the setup of a medium throughput screening method, based on ESI-MS, suitable to explore interactions of therapeutic relevance biopolymers with chemical libraries. Our approach is based on an automated flow injection ESI-MS method (AFI-MS) and has been applied to screen the Nerviano Medical Sciences proprietary fragment library of about 2000 fragments against Hsp90. In order to discard false positive hits and to discriminate those of them interacting with the N-terminal ATP binding site, competition experiments were performed using a reference inhibitor. Gratifyingly, this group of hits matches with the ligands previously identified by NMR FAXS techniques and confirmed by X-ray co-crystallization experiments. These results support the use of AFI-MS for the screening of medium size libraries, including libraries of small molecules with low affinity typically used in fragment based drug discovery. AFI-MS is a valid alternative to other techniques with the additional opportunities to identify compounds interacting with

  17. DIFFERENTIATION OF AURANTII FRUCTUS IMMATURUS AND FRUCTUS PONICIRI TRIFOLIATAE IMMATURUS BY FLOW-INJECTION WITH ULTRAVIOLET SPECTROSCOPIC DETECTION AND PROTON NUCLEAR MAGNETIC RESONANCE USING PARTIAL LEAST-SQUARES DISCRIMINANT ANALYSIS

    OpenAIRE

    Zhang, Mengliang; Zhao, Yang; Harrington, Peter de B.; Chen, Pei

    2015-01-01

    Two simple fingerprinting methods, flow-injection coupled to ultraviolet spectroscopy and proton nuclear magnetic resonance, were used for discriminating between Aurantii fructus immaturus and Fructus poniciri trifoliatae immaturus. Both methods were combined with partial least-squares discriminant analysis. In the flow-injection method, four data representations were evaluated: total ultraviolet absorbance chromatograms, averaged ultraviolet spectra, absorbance at 193, 205, 225, and 283 nm, ...

  18. Construction and performance characterization of ion-selective electrodes for potentiometric determination of pseudoephedrine hydrochloride applying batch and flow injection analysis techniques.

    Science.gov (United States)

    Zayed, Sayed I M; Issa, Yousry M; Hussein, Ahmed

    2006-01-01

    New pseudoephedrine selective electrodes have been constructed of the conventional polymer membrane type by incorporation of pseudoephedrine-phosphotungstate (PE-PT) or pseudoephedrine-silicotungstate (PE-SiT) ion-associates in a poly vinyl chloride (PVC) membrane plasticized with dibutyl phthalate (DBP). The electrodes were fully characterized in terms of the membrane composition, temperature, and pH. The electrodes exhibited mean slopes of calibration graphs of 57.09 and 56.10 mV concentration decade(-1) of PECl at 25 degrees C for (PE-PT) and (PE-SiT) electrodes, respectively. The electrodes showed fast, stable, and near-Nernstian response over the concentration ranges 6.31 x 10(-6)-1.00 x 10(-2) and 5.00 x 10(-5)-1.00x10(-2) M in the case of PE-PT applying batch and flow injection (FI) analysis, respectively, and 1.00 x 10(-5)-1.00 x 10(-2) and 5.00 x 10(-5)-1.00x10(-2) M in the case of PE-SiT for batch and FI analysis system, respectively. Detection limit was 5.01x 10(-6) M for PE-PT electrode and 6.31x10(-6) M for PE-SiT electrode. The electrodes were successfully applied for the potentiometric determination of pseudoephedrine hydrochloride (PECl) in pharmaceutical preparations with mean recovery 101.13 +/- 0.85% and 100.77+0.79% in case of PE-PT applying batch and flow injection systems, respectively, and 100.75+0.85% and 100.79 +/- 0.77% in case of PE-SiT for batch and flow injection systems, respectively. The electrodes exhibited good selectivity for PECl with respect to a large number of inorganic cations, sugars and amino acids.

  19. Analysis of phenolic xenoestrogens by pressurized CEC with amperometric detection.

    Science.gov (United States)

    Wu, Weimin; Yuan, Xiaomei; Wu, Xiaoping; Lin, Xucong; Xie, Zenghong

    2010-03-01

    A new method, pressurized CEC with end-column amperometric detection using carbon paste electrode, has been developed for the separation and determination of five phenolic xenoestrogens in chicken eggs and milk powder samples. Efficient separation of five analytes was performed by pressurized CEC using a mobile phase consisting of 60% v/v ACN and 40% v/v Tris buffer (5 mmol/L, pH 8.0), +6 kV of applied voltage and 7.0 MPa of supplementary pressure. Detection limits of 50, 5, 2, 10 and 20 ng/mL for pentachlorophenol, bisphenol-A, 2,4-dichlorophenol, 4-tert-octylphenol and 4-nonylphenol, respectively, were achieved using carbon paste electrode as working electrode and +0.8 V as detection potential. Matrix solid phase dispersion extraction method had been employed during sample preparation procedure, and mean recoveries ranged from 79.2 to 102.6% at different concentrations of phenolic xenoestrogens for spiked egg and milk powder samples were obtained.

  20. A Study of the Geo-Herbalism of Evodiae Fructus Based on a Flow-Injection Mass Spectrometric Fingerprinting Method Combined with Chemometrics

    Directory of Open Access Journals (Sweden)

    Yang Zhao

    2015-02-01

    Full Text Available A flow-injection mass spectrometric (FIMS fingerprinting method in combination with principal component analysis (PCA was used to study the geo-herbalism of Evodiae Fructus (EF samples. Twenty four EF samples from different regions in China were collected and analyzed. The PCA scores plot showed that the samples from Guizhou Province were scattered in different groups, however, most of the samples from other provinces were basically scattered in the same group. Nine characteristic compounds responsible for the classification of the samples were tentatively characterized. These nine compounds might help differentiating EF samples from different regions.

  1. Rapid isolation of biomarkers for compound specific radiocarbon dating using high-performance liquid chromatography and flow injection analysis-atmospheric pressure chemical ionisation mass spectrometry.

    Science.gov (United States)

    Smittenberg, Rienk H; Hopmans, Ellen C; Schouten, Stefan; Sinninghe Damsté, Jaap S

    2002-11-29

    Repeated semi-preparative normal-phase HPLC was performed to isolate selected biomarkers from sediment extracts for radiocarbon analysis. Flow injection analysis-mass spectrometry was used for rapid analysis of collected fractions to evaluate the separation procedure, taking only 1 min per fraction. In this way 100-1000 microg of glycerol dialkyl glycerol tetraethers, sterol fractions and chlorophyll-derived phytol were isolated from typically 100 g of marine sediment, i.e., in sufficient quantities for radiocarbon analysis, without significant carbon isotopic fractionation or contamination.

  2. Dilution Methods in Flow Injection Analysis. Evaluation of Different Approaches as Exemplified for the Determination of Nitrosyl in Concentrated Sulphuric Acid

    DEFF Research Database (Denmark)

    Jørgensen, Ulla Vang; Nielsen, Steffen; Hansen, Elo Harald

    1998-01-01

    in conjunction with knotted reactors of relatively large internal diameter (1.5 mm). The optimized FI-manifold was used with the Griess method for the spectrophotometric assay of nitrosyl (nitrite) in standards prepared in the matrix of concentrated sulphuric acid (detection limit 0.16 mg/l NO+-N (3s......Instigated by developing a flow injection procedure for assay of nitrosyl in concentrated sulphuric acid, different approaches for reliable and robust on-line dilution in FIA were evaluated. These comprised the application of mixing tees in conjunction with mixing coils (including knotted reactors...

  3. A Novel Amperometric Glutamate Biosensor Based on Glutamate Oxidase Adsorbed on Silicalite

    Science.gov (United States)

    Soldatkina, O. V.; Soldatkin, O. O.; Kasap, B. Ozansoy; Kucherenko, D. Yu.; Kucherenko, I. S.; Kurc, B. Akata; Dzyadevych, S. V.

    2017-04-01

    In this work, we developed a new amperometric biosensor for glutamate detection using a typical method of glutamate oxidase (GlOx) immobilization via adsorption on silicalite particles. The disc platinum electrode ( d = 0.4 mm) was used as the amperometric sensor. The procedure of biosensor preparation was optimized. The main parameters of modifying amperometric transducers with a silicalite layer were determined along with the procedure of GlOx adsorption on this layer. The biosensors based on GlOx adsorbed on silicalite demonstrated high sensitivity to glutamate. The linear range of detection was from 2.5 to 450 μM, and the limit of glutamate detection was 1 μM. It was shown that the proposed biosensors were characterized by good response reproducibility during hours of continuous work and operational stability for several days. The developed biosensors could be applied for determination of glutamate in real samples.

  4. Chemiluminescent determination of vanadium(IV) using a cinchomeronic hydrazide-H{sub 2}O{sub 2} system and flow injection analysis

    Energy Technology Data Exchange (ETDEWEB)

    Pradana Perez, J.A. [Departamento de Ciencias Analiticas, Facultad de Ciencias, Universidad Nacional de Educacion a Distancia, c/Senda del Rey 9, 28040 Madrid (Spain); Alegria, J.S. Durand [Departamento de Ciencias Analiticas, Facultad de Ciencias, Universidad Nacional de Educacion a Distancia, c/Senda del Rey 9, 28040 Madrid (Spain); Hernando, P. Fernandez [Departamento de Ciencias Analiticas, Facultad de Ciencias, Universidad Nacional de Educacion a Distancia, c/Senda del Rey 9, 28040 Madrid (Spain)]. E-mail: pfhernando@ccia.uned.es; Sierra, A. Narros [Departamento de Ingenieria Quimica y del Medio Ambiente, Escuela Tecnica Superior de Ingenieros Industriales, Universidad Politecnica de Madrid, Madrid (Spain)

    2005-04-22

    This paper proposes a new chemiluminescent flow injection analysis (FIA) method for the determination of vanadium(IV) ions in aqueous media. The method is based on the chemiluminescent reaction that occurs between cinchomeronic hydrazide (CH) and hydrogen peroxide in a strongly alkaline medium, in which vanadium(IV) acts as a catalyst. The chemical and physical variables involved in the flow injection system are optimised using a modified simplex method. Vanadium ions can be detected in the 0.08 and 1.00 {mu}g mL{sup -1} range; the detection limit for a signal-to-noise ratio of 3 is 0.08 {mu}g mL{sup -1}. Great variations in the quantum yield were observed when cobalt(II), chromium(III), copper(II) and/or nickel(II) were present in the reaction medium. The proposed method is selective and simple, and can be successfully used to analyse water samples without the need for separation or preconcentration processes.

  5. Optimization of a field flow pre-concentration system by experimental design for the determination of copper in sea water by flow-injection-atomic absorption spectrometry

    Science.gov (United States)

    Yebra, M. C.; Carro, N.; Moreno-Cid, A.

    2002-01-01

    A Plackett-Burman 2 7×3/32 design for seven factors (sample pH, sample flow rate, eluent volume, eluent concentration, eluent flow rate, ethanol percentage in the eluent and mini-column diameter) was carried out in order to find the significant variables affecting the field flow pre-concentration system (FFPS) and the flow injection elution manifold for copper determination in seawater samples by flame atomic absorption spectrometry. By using the optimized flow systems, seawater samples were collected and pre-concentrated in situ by passing them with a peristaltic pump through a mini-column packed with Amberlite XAD-4 impregnated with the complexing agent 4-(2-pyridylazo) resorcinol. Thus, copper is pre-concentrated without the interference of the saline matrix. Once in the laboratory, the mini-columns loaded with copper are incorporated into a flow injection system and eluted with a small volume of a 40% (v/v) ethanolic solution of 3 mol l -1 hydrochloric acid into the nebulizer-burner system of a flame atomic absorption spectrometer. Analysis of certified reference materials (SLEW-3 and NASS-5) showed good agreement with the certified value.

  6. Quantitative Analysis of Piroxicam Using Temperature-Controlled Ionic Liquid Dispersive Liquid Phase Microextraction Followed By Stopped-Flow Injection Spectrofluorimetry

    Directory of Open Access Journals (Sweden)

    Mohammad Reza Ganjali

    2013-07-01

    Full Text Available Background:Piroxicam (PXM belongs to the wide class of non-steroidal anti-inflammatory drugs (NSAIDs. PXM has been widely applied in the treatment of rheumatoid arthritis, gonarthrosis, osteoarthritis, backaches, neuralgia, mialgia. In the presented work, a green and benign sample pretreatment method called temperature-controlled ionic liquid dispersive liquid phase microextraction (TCIL-DLPME was followed with stopped-flow injection spectrofluorimetry (SFIS for quantitation of PXM in pharmaceutical formulations and biological samples.Methods:Temperature-controlled ionic liquid dispersive liquid phase microextraction (TCIL-DLPME was applied as an environmentally friendly sample enrichment method to extract and isolate PXM prior to quantitation. Dispersion of 1-hexyl-3-methylimidazolium hexafluorophosphate ([Hmim][PF6] ionic liquid (IL through the sample aqueous solution was performed by applying a relatively high temperature. PXM was extracted into the extractor, and after phase separation, PXM in the final solution was determined by stopped-flow injection spectrofluorimetry (SFIS.Results and Major Conclusion:Different factors affecting the designed method such as IL amount, diluting agent, pH and temperature were investigated in details and optimized. The method provided a linear dynamic range of 0.2-150 μg l-1, a limit of detection (LOD of 0.046 μg l-1 and a relative standard deviation (RSD of 3.1%. Furthermore, in order to demonstrate the analytical applicability of the recommended method, it was applied for quantitation of PXM in real samples.

  7. AN APPLICATION OF FLOW INJECTION ANALYSIS WITH GAS DIFFUSION AND SPECTROPHOTOMETRIC DETECTION FOR THE MONITORING OF DISSOLVED SULPHIDE CONCENTRATION IN ENVIRONMENTAL SAMPLES

    Directory of Open Access Journals (Sweden)

    Malwina Cykowska

    2014-10-01

    Full Text Available The monitoring of the concentration of sulphide is very important from the environment point of view because of high toxicity of hydrogen sulphide. What is more hydrogen sulphide is an important pollution indicator. In many cases the determination of sulphide is very difficult due to complicated matrix of some environmental samples, which causes that most analytical methods cannot be used. Flow injection analysis allows to avoid matrix problem what makes it suitable for a wide range of applications in analytical laboratories. In this paper determination of dissolved sulphide in environmental samples by gas-diffusion flow injection analysis with spectrophotometric detection was presented. Used gas-diffusion separation ensures the elimination of interferences caused by sample matrix and gives the ability of determination of sulphides in coloured and turbid samples. Studies to optimize the measurement conditions and to determine the value of the validation parameters (e.g. limit of detection, limit of quantification, precision, accuracy were carried out. Obtained results confirm the usefulness of the method for monitoring the concentration of dissolved sulphides in water and waste water. Full automation and work in a closed system greatly reduces time of analysis, minimizes consumption of sample and reagents and increases safety of analyst’s work.

  8. Simultaneous Determination of Iron, Copper and Cobalt in Food Samples by CCD-diode Array Detection-Flow Injection Analysis with Partial Least Squares Calibration Model

    Energy Technology Data Exchange (ETDEWEB)

    Mi Jiaping; Li Yuanqian; Zhou Xiaoli; Zheng Bo; Zhou Ying [West China School of Public Health, Sichuan University, Chengdu, 610041 (China)

    2006-01-01

    A flow injection-CCD diode array detection spectrophotometry with partial least squares (PLS) program for simultaneous determination of iron, copper and cobalt in food samples has been established. The method was based on the chromogenic reaction of the three metal ions and 2- (5-Bromo-2-pyridylazo)-5-diethylaminophenol, 5-Br-PADAP in acetic acid - sodium acetate buffer solution (pH5) with Triton X-100 and ascorbic acid. The overlapped spectra of the colored complexes were collected by charge-coupled device (CCD) - diode array detector and the multi-wavelength absorbance data was processed using partial least squares (PLS) algorithm. Optimum reaction conditions and parameters of flow injection analysis were investigated. The samples of tea, sesame, laver, millet, cornmeal, mung bean and soybean powder were determined by the proposed method. The average recoveries of spiked samples were 91.80%{approx}100.9% for Iron, 92.50%{approx}108.0% for Copper, 93.00%{approx}110.5% for Cobalt, respectively with relative standard deviation (R.S.D) of 1.1%{approx}12.1%. The sampling rate is 45 samples h{sup -1}. The determination results of the food samples were in good agreement between the proposed method and ICP-AES.

  9. Development of a Telemetric, Miniaturized Electrochemical Amperometric Analyzer

    Directory of Open Access Journals (Sweden)

    Jaehyo Jung

    2017-10-01

    Full Text Available In this research, we developed a portable, three-electrode electrochemical amperometric analyzer that can transmit data to a PC or a tablet via Bluetooth communication. We performed experiments using an indium tin oxide (ITO glass electrode to confirm the performance and reliability of the analyzer. The proposed analyzer uses a current-to-voltage (I/V converter to convert the current generated by the reduction-oxidation (redox reaction of the buffer solution to a voltage signal. This signal is then digitized by the processor. The configuration of the power and ground of the printed circuit board (PCB layer is divided into digital and analog parts to minimize the noise interference of each part. The proposed analyzer occupies an area of 5.9 × 3.25 cm2 with a current resolution of 0.4 nA. A potential of 0~2.1 V can be applied between the working and the counter electrodes. The results of this study showed the accuracy of the proposed analyzer by measuring the Ruthenium(III chloride ( Ru III concentration in 10 mM phosphate-buffered saline (PBS solution with a pH of 7.4. The measured data can be transmitted to a PC or a mobile such as a smartphone or a tablet PC using the included Bluetooth module. The proposed analyzer uses a 3.7 V, 120 mAh lithium polymer battery and can be operated for 60 min when fully charged, including data processing and wireless communication.

  10. Carbon coated magnesium oxide based amperometric glucose biosensor

    Energy Technology Data Exchange (ETDEWEB)

    Silva, L.L.; Mello, J.M.M.; Fiori, M.A.; Duarte, G.W. [Universidade Comunitaria Regional de Chapeco (UNICHAPECO), SC (Brazil); Fernandes, S.C. [Instituto Federal Catarinense (IFC), Blumenau, SC (Brazil); Riella, H.G. [Centro Universitario Barriga Verde (UNIBAVE), Orleans, SC (Brazil); Anzolin, C.; Figueiro, A.; Grando, M.C. [Universidade Federal de Santa Catarina (UFSC), SC (Brazil)

    2016-07-01

    Full text: Diabetes is a serious disease that is harmful to human health since it is related to cardiovascular and stroke events. Since the first glucose oxidase (GOx) sensor, different approaches have been explored. Carbon was used to cover nano-magnesium oxide (MgO-C) forming a core-shell which was used to improve its biocompatibility and chemical stability for the preparation of GOx biosensor. MgO nanostructures have been prepared by calcination of the gel formed by the reaction of magnesium acetate tetrahydrate dissolved in cetyltrimethylammonium with the addition of tartaric acid solution. MgO-C nanostructures were obtained by heating MgO nanoparticles previously prepared together with glucose and PEG dissolved in an aqueous suspension. Reaction conditions such as concentration of magnesium precursor, temperature and aging time show important roles in the size, morphology and growth process of the final products. The core-shell structure was evidenced by SEM/FEG and XRD and showed that the product appeared to have morphological forms of nanowires. GOx was spread onto the surface of a modified carbon paste electrode (CPE) doped with MgO-C and the effect on the biosensing properties investigated by comparing the electrochemical properties of the proposed biosensor with bare and modified CPEs by cyclic voltammetry. The amount of modifier in CPE (5-75 weight% with respect to graphite) influences the peak current and the influence of different experimental parameters (enzyme percentage, pH solution and amperometric methods) was also investigated. The results demonstrate that the GOx retains its biocatalytic activity and that the bioelectrode modified can be a possible use for other nanotechnological purposes including biomedical ones. (author)

  11. Transparent Electrode Materials for Simultaneous Amperometric Detection of Exocytosis and Fluorescence Microscopy.

    Science.gov (United States)

    Kisler, Kassandra; Kim, Brian N; Liu, Xin; Berberian, Khajak; Fang, Qinghua; Mathai, Cherian J; Gangopadhyay, Shubhra; Gillis, Kevin D; Lindau, Manfred

    2012-01-01

    We have developed and tested transparent microelectrode arrays capable of simultaneous amperometric measurement of oxidizable molecules and fluorescence imaging through the electrodes. Surface patterned microelectrodes were fabricated from three different conducting materials: Indium-tin-oxide (ITO), nitrogen-doped diamond-like carbon (DLC) deposited on top of ITO, or very thin (12-17 nm) gold films on glass substrates. Chromaffin cells loaded with lysotracker green or acridine orange dye were placed atop the electrodes and vesicle fluorescence imaged with total internal reflection fluorescence (TIRF) microscopy while catecholamine release from single vesicles was measured as amperometric spikes with the surface patterned electrodes. Electrodes fabricated from all three materials were capable of detecting amperometric signals with high resolution. Unexpectedly, amperometric spikes recorded with ITO electrodes had only about half the amplitude and about half as much charge as those detected with DLC or gold electrodes, indicating that the ITO electrodes are not as sensitive as gold or DLC electrodes for measurement of quantal catecholamine release. The lower sensitivity of ITO electrodes was confirmed by chronoamperometry measurements comparing the currents in the presence of different analytes with the different electrode materials.

  12. A flow-through amperometric sensor based on dialysis tubing and free enzyme reactors

    NARCIS (Netherlands)

    Bohm, S.; Pijanowska, D.G.; Pijanowska, D.; Olthuis, Wouter; Bergveld, Piet

    2001-01-01

    A generic flow-through amperometric microenzyme sensor is described, which is based on semi-permeable dialysis tubing carrying the sample to be analyzed. This tubing (300 μm OD) is led through a small cavity, containing the working and reference electrode. By filling this cavity with a few μl of an

  13. A Nafion®-based co-planar electrode amperometric sensor for ...

    Indian Academy of Sciences (India)

    based ... amperometric mode. The methanol detector could be operated both in a nitrogen stream and (in what is essential for practical applications) in an air atmosphere too, with estimated detection limits of 1.2 and 1.4 Torr respectively.

  14. Pulsed Amperometry for Anti-fouling of Boron-doped Diamond in Electroanalysis of β-Agonists: Application to Flow Injection for Pharmaceutical Analysis

    Directory of Open Access Journals (Sweden)

    Duangjai Nacapricha

    2006-01-01

    Full Text Available This work presents the construction and application of boron-doped diamond(BDD thin film electrode as sensor for the determination of three β-agonists, viz.salbutamol, terbutaline and clenbuterol. Although well-known as a chemically inertmaterial, BDD film however shows fouling in detection of these compounds using fixedpotentialmode amperometry. A suitable waveform for pulsed amperometric detection(PAD was developed and used to determine the agonist compounds. It was seen that thedeveloped PAD significantly refreshed the BDD surface for long-term detection in flowinjection analysis. Linear working ranges were 0.5-100 μM, 1.0-100 μM and 0.5-50 μM forsalbutamol, terbutaline and clenbuterol, respectively. The developed PAD-BDD system wasapplied to successfully determine salbutamol and terbutaline in commercial pharmaceuticalproducts. The methods were validated with a capillary electrophoresis method.

  15. Determination of formaldehyde in frozen fish with formaldehyde dehydrogenase using a flow injection system with an incorporated gel-filtration chromatrography column

    DEFF Research Database (Denmark)

    Bechmann, Iben Ell

    1996-01-01

    A flow injection analysis (FIA) system for determination of formaldehyde in frozen fish products is described. The system provides a rapid and selective determination of formaldehyde in aqueous fish extracts by the combination of a deproteinization procedure and a stopped-now enzymatic approach...... in a FIA system. The FIA system is furnished with a gel-filtration chromatography column for on-line removal of the proteins from the extract before the enzymatic analysis is performed. Compared with the standard methods for determination of formaldehyde in fish products the present method is much faster...... and less affected by interferences. The limit of detection for the proposed method is 2.5 mg/l of formaldehyde. The sampling frequency is about 10 determinations per hour....

  16. Determination of Formaldehyde in Frozen Fish with Formaldehyde Dehydrogenase Using a Flow Injection System with an Incorporated Gel-filtration Chromatography Column

    DEFF Research Database (Denmark)

    Bechmann, Iben Ellegaard

    1996-01-01

    A flow injection analysis (FIA) system for determination of formaldehyde in frozen fish products is described. The system provides a rapid and selective determination of formaldehyde in aqueous fish extracts by the combination of a deproteinization procedure and a stopped-flow enzymatic approach...... in a FIA system. The FIA system is furnished with a gel-filtration chromatography column for on-line removal of the proteins from the extract before the enzymatic analysis is performed. Compared with the standard methods for determination of formaldehyde in fish products the present method is much faster...... and less affected by interferences. The limit of detection for the proposed method is 2.5 mg/l of formaldehyde. The sampling frequency is about 10 determinations per hour....

  17. Study the effects of drying processes on chemical compositions in daylily flowers using flow injection mass spectrometric fingerprinting method and chemometrics.

    Science.gov (United States)

    Liu, Wei; Zhao, Yang; Sun, Jianghao; Li, Gaoyang; Shan, Yang; Chen, Pei

    2017-12-01

    Daylily flowers is an important vegetable in eastern Asia, widely used in many dishes. Daylily flowers are usually sold in dried forms in the supermarkets. There are a few method for processing fresh daylily flowers, however, no study has been conducted to analyze the effects of the processing methods in the composition of final products. In the present study, a flow-injection mass spectrometric fingerprinting (FIMS) method in combination with principal component analysis (PCA) was used to differentiate two species of daylily flowers (Mengzi and Chongli) with three different treatments (vacuum freeze drying, solar drying and hot-air drying treatments) for each. The results showed the fast and simple FIMS method could successfully differentiate between species (raw material) and treatments among each species. However, the two species could not be discriminated very well after being processed in hot-air drying treatment. The difference in chemical profiles of species and treatments were discussed. Copyright © 2017. Published by Elsevier Ltd.

  18. Analyte enrichment and matrix removal in flow injection analysis-inductively coupled plasma-atomic emission spectrometry: determination of phosphorus in steels

    Science.gov (United States)

    McLeod, C. W.; Cook, I. G.; Worsfold, P. J.; Davies, J. E.; Queay, J.

    A flow injection analysis (FIA) system incorporating a microcolumn of activated alumina has been devised for performing rapid analyte enrichment/matrix removal in inductively coupled plasma-atomic emission spectrometry (ICP-AES). The activated alumina has a high affinity for phosphate ions and the FIA system was tested for the determination of trace P in synthetic aqueous solutions utilizing the PI 213.62 nm line. Phosphate deposition and elution were dependent on sample acidity, column length and the nature and concentration of eluent. Linear calibration was established over the range 0-50 μgP ml -1 and the relative standard deviation was 1.6% at 20 μgP ml -1. The limit of detection was 0.6 μgP ml -1 without analyte enrichment. Application to the analysis of a standard steel (BCS 408) was demonstrated.

  19. Flow-injection analysis utilizing a spectrally segmented photodiode-array inductively coupled plasma emission spectrometer—I. Microcolumn preconcentration for the determination of molybdenum

    Science.gov (United States)

    Furuta, N.; Brushwyler, K. R.; Hieftje, G. M.

    A flow-injection analysis (FIA) system incorporating a microcolumn of activated alumina was used for the determination of molybdenum by inductively coupled plasma-atomic emission spectrometry (ICP-AES). The transient signal resulting from the injection of molybdenum was determined by a spectrally segmented photodiode-array spectrometer. Linear calibration was established for molybdenum over a concentration range 0-1000 ng ml -1. The detection capability was approximately 50 times better than that offered by comparable continuous-nebulization systems. The detection limit for molybdenum was 0.2 ng ml -1, and the relative standard deviations at 500 and 10 ng ml -1 were about 2 and 5%, respectively. The ability of the multichannel photodiode-array spectrometer to correct for background shifts which occur during the signal integration period provided improved precision and accuracy. Application to the determination of molybdenum in standard sea water (NASS-2) was demonstrated.

  20. Flow-injection analysis utilizing a spectrally segmented photodiode-array inductively coupled plasma emission spectrometer. 1: Microcolumn preconcentration for the determination of molybdenum

    Science.gov (United States)

    Furuta, Naoki; Brushwyler, K. R.; Hieftje, Gary M.

    1989-02-01

    A flow injection analysis (FIA) system incorporating a microcolumn of activated alumina was used for the determination of molybdenum by inductively coupled plasma-atomic emission spectrometry (ICP-AES). The transient signal resulting from the injection of molybdenum was determined by a spectrally segmented photodiode-array spectro-meter. Linear calibration was established for molybdenum over a concentration range 0 to 1000 ng/ml. The detection capability was approximately 50 times better than offered by comparable continuous-nebulization systems. The detection limit for molybdenum was 0.2 ng/ml, and the relative standard deviations at 500 and 10 ng/ml were about 2 and 5 percent, respectively. The ability of the multichannel photodiode array spectrometer to correct for background shifts which occur during signal integration period provided improved precision and accuracy. Application to the analysis of molybdenum in standard sea water (NASS-2) was demonstrated.

  1. Flow Injection Potentiometric Determination of Cd2+ Ions Using a Coated Graphite Plasticized PVC-Membrane Electrode Based on 1, 3-Bis(2-cyanobenzene)triazene.

    Science.gov (United States)

    Shamsipur, Mojtaba; Sahari, Shokat; Payehghadr, Mahmood; Alizadeh, Kamal

    2011-09-01

    1, 3-Bis(2-cyanobenzene)triazene, L, was used as a suitable ionophore for the fabrication of a new PVC-based polymeric membrane coated graphite electrode for selective sensing of Cd2+ ion. The electrode exhibited a selective linear Nernstian response to Cd2+ ion at an optimal pH range of 6-9 with a limit of detection of 8.0 × 10-6 M and a fast response time of about 2 s. The electrode was used as a proper detection system in flow-injection potentiometry of cadmium ion and resulted in well defined peaks for cadmium ions with stable baseline, excellent reproducibility and high sampling rates of over 100 injections per hour. It showed good stability, reproducibility and fast response time. The practical utility of the proposed system has also been reported.

  2. Flow-injection chemiluminescence determination of enalapril maleate in pharmaceuticals and biological fluids using tris(2,2'-bipyridyl)ruthenium(II).

    Science.gov (United States)

    Alarfaj, Nawal A A

    2003-08-01

    A chemiluminescence (CL) method using flow injection (FI) has been investigated for the rapid and sensitive determination of enalapril maleate. The method is based on the CL reaction of the drug with tris(2,2'-bipyridyl)ruthenium(II), Ru(bipy)3(2+) and acidic potassium permanganate. After selecting the best operating parameters, calibration graphs were obtained over concentration ranges of 0.005-0.2 microg/ml and 0.7-100 microg/ml with a detection limit (S/N=2) of 1.0 ng/ml. The average % found was 99.9 +/- 0.7 and 100.2 +/- 0.3 for the two concentration ranges respectively. %RSD (n=10) for 5.0 microg/ml was 0.44. The method was successfully applied to the determination of enalapril maleate in dosage forms and biological fluids without interferences.

  3. Rapid Quantitative Analysis of Multiple Explosive-Compound Classes on a Single Instrument via Flow-Injection Analysis Tandem Mass Spectrometry

    Science.gov (United States)

    2017-03-20

    on a Single In‐ strument via Flow‐Injection Analysis Tandem Mass  Spectrometry   Alla Ostrinskaya, Roderick R. Kunz, Michelle Clark, Rich P...alla.ostrinskaya@ll.mit.edu    ABSTRACT: A flow injection analysis (FIA) tandem mass spectrometry (MSMS) method was developed for rapid quantita- tive analysis of...and has redundant detection channels for reduced  error   rates necessary  for probative use,  (b)  is more  rapid  than existing methods to allow for

  4. On-line flow injection molecularly imprinted solid phase extraction for the preconcentration and determination of 1-hydroxypyrene in urine samples.

    Science.gov (United States)

    Serrano, Montserrat; Bartolomé, Mónica; Bravo, Juan Carlos; Paniagua, Gema; Gañan, Judith; Gallego-Picó, Alejandrina; Garcinuño, Rosa María

    2017-05-01

    New analytical strategies tend to automation of sample pre-treatment and flow analysis techniques provided a number of enhanced analytical methods allowing high throughput. Flow techniques are usually faster, more robust and more flexible than their batch equivalents. In addition, flow methods use less sample and reagent amounts and reduce analytical costs and waste. A flow injection solid-phase extraction pre-concentration system using a molecularly imprinted polymer (MIP) packed micro-column was developed for the determination of 1-hydroxypyrene in human urine with fluorescence detection. The pre-concentration of 1-hydroxypyrene on the MIP was carried out based on the specific retention of analyte by on-line introducing the sample into the micro-column system. Methanol and dichloromethane mixture was used to elute the retained analyte for fluorometric analysis. Important influencing factors were studied in detail, in batch and in flow (MISPE procedure optimisation, sample and eluent volumes, flow rate, dimensions of MIP micro-column and amounts of packing material, etc). To the best of our knowledge, this is the first on-line flow injection molecularly imprinted solid phase extraction for the pre-concentration and determination of hydroxylate PAH metabolite in urine samples. The optimised method was successfully applied to the determination of 1-Hydroxypyrene in spiked urine samples, with recoveries in the range of 74-85% and RSD0.996. We obtained limit of detection and quantification of 3.1μgL -1 and 10.5μgL -1 , respectively. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. Application of an on-line flow injection high resolution inductivity coupled plasma mass spectrometry to the determination of Pu isotopes in soil and seawater

    International Nuclear Information System (INIS)

    Kim, Chang-Kyu; Kim, Cheol-Su; Rho, Byung-Hwan; Lee, Jong-Inn

    2000-01-01

    High resolution inductively coupled plasma mass spectrometry combined with an on-line flow injection system (FI-HR-ICP-MS) was applied to the determination of ultra-trace level 239 Pu and 240 Pu and their atomic ratio ( 240 Pu/ 239 Pu) in soil and seawater samples. To reduce the interference effect of 238 U, MCN-6000(R) was used as a sample introduction system, which showed a 5-fold reduction in 238 UH + formation, compared to the conventional pneumatic nebulizer. The flow injection system (PrepLab(TM)) coupled with HR-ICP-MS, which was composed of Sr-Spec(R) and TEVA-Spec(R) resins, reduced significantly the sample volume and the analysis time, compared to the conventional method of Pu isotopes. With this method, it was possible to determine ultra-low level of Pu in only 0.5 g soil and 5L surface seawater with an analysis speed of 3 - 5 hours per sample. The accuracy of this method was verified by the spike recovery experiments and by the comparison of results obtained from the on-line FI-HR-ICP-MS method with one from alpha spectrometry. In spite of small amount sample, the RSD in the determination of 239 Pu and 240 Pu by the on-line FI-HR-ICP-MS were less than 7%. The analytical results of the NIST reference material obtained by the present method agreed with certified values within a 10% of relative error. The detection limits for 239 Pu and 240 Pu were 1.27 fg m -1 (2.92 μBq ml -1 ) and 0.88 fg ml -1 (7.38 μBq ml -1 ), respectively. (author)

  6. Rapid Quantitation of Ascorbic and Folic Acids in SRM 3280 Multivitamin/Multielement Tablets using Flow-Injection Tandem Mass Spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Bhandari, Deepak [ORNL; Kertesz, Vilmos [ORNL; Van Berkel, Gary J [ORNL

    2013-01-01

    RATIONALE: Ascorbic acid (AA) and folic acid (FA) are water-soluble vitamins and are usually fortified in food and dietary supplements. For the safety of human health, proper intake of these vitamins is recommended. Improvement in the analysis time required for the quantitative determination of these vitamins in food and nutritional formulations is desired. METHODS: A simple and fast (~5 min) in-tube sample preparation was performed, independently for FA and AA, by mixing extraction solvent with a powdered sample aliquot followed by agitation, centrifugation, and filtration to recover an extract for analysis. Quantitative detection was achieved by flow-injection (1 L injection volume) electrospray ionization tandem mass spectrometry (ESI-MS/MS) in negative ion mode using the method of standard addition. RESULTS: Method of standard addition was employed for the quantitative estimation of each vitamin in a sample extract. At least 2 spiked and 1 non-spiked sample extract were injected in triplicate for each quantitative analysis. Given an injection-to-injection interval of approximately 2 min, about 18 min was required to complete the quantitative estimation of each vitamin. The concentration values obtained for the respective vitamins in the standard reference material (SRM) 3280 using this approach were within the statistical range of the certified values provided in the NIST Certificate of Analysis. The estimated limit of detections of FA and AA were 13 and 5.9 ng/g, respectively. CONCLUSIONS: Flow-injection ESI-MS/MS was successfully applied for the rapid quantitation of FA and AA in SRM 3280 multivitamin/multielement tablets.

  7. Determination of Ultra-trace Amounts of Arsenic(III) by Flow Injection Hydride Generation Atomic Absorption Spectrometry with On-line Preconcentration by Coprecipitation with Lanthanum Hydroxide or Hafnium Hydroxide

    DEFF Research Database (Denmark)

    Nielsen, Steffen; Sloth, Jens Jørgen; Hansen, Elo Harald

    1996-01-01

    A time-based flow-injection (FI) procedure for the determination of ultra-trace amounts of inorganic arsenic(III) is described, which combines hydride generation atomic absorption spectrometry (HG-AAS) with on-line preconcentration of the analyte by inorganic coprecipitation-dissolution in a filt......A time-based flow-injection (FI) procedure for the determination of ultra-trace amounts of inorganic arsenic(III) is described, which combines hydride generation atomic absorption spectrometry (HG-AAS) with on-line preconcentration of the analyte by inorganic coprecipitation...

  8. Elaboration of new method of enzyme adsorption on silicalite and nano beta zeolite for amperometric biosensor creation

    Directory of Open Access Journals (Sweden)

    Soldatkin O. O.

    2014-07-01

    Full Text Available Aim. Optimization of a new method of enzyme immobilization for amperometric biosensor creation. Methods. The amperometric biosensor with glucose oxidase immobilized on zeolites as bioselective elements and platinum disk electrode as transducers of biochemical signal into the electric one was used in the work. Results. The biosensors based on glucose oxidase adsorbed on zeolites were characterized by a higher sensitivity to glucose and a better inter-reproducibility. The best analytical characteristics were obtained for the biosensors based on nano beta zeolite. It has been found that an increase in the amount of zeolite on the surface of amperometric transducer may change such biosensor parameters as sensitivity to the substrate and duration of the analysis. Conclusions. The proposed method of enzyme immobilization by adsorption on zeolites is shown to be quite promising in the development of amperometric biosensors and therefore should be further investigated.

  9. Discrimination of Aurantii Fructus Immaturus and Fructus Poniciri Trifoliatae Immaturus by Flow Injection UV Spectroscopy (FIUV) and 1H NMR using Partial Least-squares Discriminant Analysis (PLS-DA)

    Science.gov (United States)

    Two simple fingerprinting methods, flow-injection UV spectroscopy (FIUV) and 1H nuclear magnetic resonance (NMR), for discrimination of Aurantii FructusImmaturus and Fructus Poniciri TrifoliataeImmaturususing were described. Both methods were combined with partial least-squares discriminant analysis...

  10. Differentiation of leaf and whole-plant samples of di- and tetraploid Gynostemma pentaphyllum (Thunb.) Makino using flow-injection mass spectrometric(FIMS) fingerprinting method combined with chemometric approaches

    Science.gov (United States)

    In the present study, the feasibility and advantages of employing a flow-injection mass spectrometry (FIMS) fingerprinting method combined with chemometric analyses for assessment of di- and tetraploid leaf and whole-plant Gynostemma. pentaphyllum (Thunb.) Makino samples were investigated for the fi...

  11. Determination of As(III) and As(V) by Flow Injection-Hydride Generation-Atomic Absorption Spectrometry via On-line Reduction of As(V) by KI

    DEFF Research Database (Denmark)

    Nielsen, Steffen; Hansen, Elo Harald

    1997-01-01

    A volume-based flow injection (FI) procedure is described for the determination and speciation of trace inorganic arsenic, As(III) and As(V), via hydride generation-atomic absorption spectrometry (HG-AAS) of As(III). The determination of total arsenic is obtained by on-line reduction of As(V) to As...

  12. Amperometric Detection of Bacillus anthracis Spores: A Portable, Low-Cost Approach to the ELISA

    Directory of Open Access Journals (Sweden)

    Gabriel D. Peckham

    2013-01-01

    Full Text Available Antibody-based detection assays are generally robust, a desirable characteristic for in-the-field use. However, to quantify the colorimetric or fluorescent signal, these assays require expensive and fragile instruments which are ill-suited to in-the-field use. Lateral flow devices (LFDs circumvent these barriers to portability but suffer from poor sensitivity and subjective interpretation. Here, an antibody-based method for detecting Bacillus anthracis spores via amperometric signal generation is compared to ELISA and LFDs. This amperometric immunoassay uses antibody conjugated to magnetic beads and glucose oxidase (GOX along with the electron mediator 2, 6-dichlorophenolindophenol (DCPIP for production of a measurable current from a 0.4 V bias voltage. With similar sensitivity to ELISA, the assay can be completed in about 75 minutes while being completely powered and operated from a laptop computer. Immunoassay amperometry holds promise for bringing low-cost, quantitative detection of hazardous agents to the field.

  13. Functional materials in amperometric sensing polymeric, inorganic, and nanocomposite materials for modified electrodes

    CERN Document Server

    Seeber, Renato; Zanardi, Chiara

    2014-01-01

    Amperometric sensors, biosensors included, particularly rely on suitable electrode materials. Progress in material science has led to a wide variety of options that are available today. For the first time, these novel functional electrode coating materials are reviewed in this monograph, written by and for electroanalytical chemists. This includes intrinsically conducting, redox and ion-exchange polymers, metal and carbon nanostructures, silica based materials. Monolayers and relatively thick films are considered. The authors critically discuss preparation methods, in addition to chemical and

  14. Development of innovative competitive amperometric immunosensors as promising tools in clinical diagnosis and food safety applications

    OpenAIRE

    Costantini, Monica

    2017-01-01

    The aim of the research project was the development of competitive amperometric biosensors for clinical diagnostics and food safety applications, as a part of a research activity focused on innovations in sensing systems investigated in our laboratories of analytical chemistry. In particular, the project purpose was the development of innovative sensors for detection of serum biomarkers for HIV (Human Immunodeficiency Virus) and HCV (Hepatitis C Virus) and the development of competitive immun...

  15. Amperometric S-Nitrosothiol Sensor with Enhanced Sensitivity Based on Organoselenium Catalysts

    OpenAIRE

    Cha, Wansik; Anderson, Meredith R.; Zhang, Fenghua; Meyerhoff, Mark E.

    2008-01-01

    A new S-nitrosothiol (RSNO) detection strategy based on an electrochemical sensor is described for rapidly estimating levels of total RSNOs in blood and other biological samples. The sensor employs a cellulose dialysis membrane covalently modified with an organoselenium catalyst that converts RSNOs to NO at the distal tip of an amperometric NO sensor. The sensor is characterized by very low detection limits (< 20 nM), good long-term stability and can be employed for the rapid detection of tot...

  16. Increasing amperometric biosensor sensitivity by length fractionated single-walled carbon nanotubes

    DEFF Research Database (Denmark)

    Tasca, Federico; Gorton, Lo; Wagner, Jakob Birkedal

    2008-01-01

    chromatography. Transmission electron micrographs of different fractions of SWCNTs were collected. Diaphorase ``wired'' to an osmium redox polymer was blended with the shortened SWCNTs of different lengths. Depending on the average length of the SWCNTs the sensitivity of the amperometric biosensor model system...... limit was 1 mu M. The biosensor exhibited excellent electrocatalytic properties. Even at relatively high NADH concentrations the oxidative current was limited by the diffusion rate of NADH. (C) 2008 Elsevier B.V. All rights reserved....

  17. Ionic liquid-polymer electrolyte for amperometric solid-state NO2 sensor

    Czech Academy of Sciences Publication Activity Database

    Nádherná, Martina; Opekar, F.; Reiter, Jakub

    2011-01-01

    Roč. 56, č. 16 (2011), s. 5650-5655 ISSN 0013-4686 R&D Projects: GA AV ČR(CZ) KJB200320801; GA AV ČR(CZ) KJB200320901; GA MŠk(CZ) LC523 Institutional research plan: CEZ:AV0Z40320502 Keywords : Amperometric gas sensor * Solid-state sensor * Ionic liquid * Nitrogen dioxide * Gold minigrid Subject RIV: CA - Inorganic Chemistry OBOR OECD: Inorganic and nuclear chemistry Impact factor: 3.832, year: 2011

  18. Analogs of N-cynnamoylphenylhydroxylamine as reagents for amperometric determination of scandium

    International Nuclear Information System (INIS)

    Shvedene, N.V.; Gallaj, Z.A.; Sheina, N.M.; Zujkova, N.V.

    1978-01-01

    To decrease the detection limit of scandium and increase selectivity of amperometric determination, oxidation of 2-furylacryloyl-N-p-chlorophenylhydroxylamine (FACPhHA) and 3-styrylacryloyl-N-phenylhydroxylamine (SAPhHA) on a graphite electrode has been studied by volt-amperometry. The possibility has been established of using the oxidation current of the reagent for plotting the titration curves. The solubility of scandium complexes with FACPhHA and SAPhHA under conditions of titration against the background with pH 6.0 has been determined and equals (2.1+-0.3)x10 -6 and (5.3+-0.3)x10 -7 , respectively. The methods have been developed of amperometric determination of scandium with the use of the considered reagents against backgrounds with pH 5.5-6.5. The use of SAPhHA has decreased the limit of scandium detection down to 0.1 mgk/ml. Besides, the amperometric method makes it possible to titrate in turbid and coloured media what is an advantage of this method. The developed method is used for determination of scandium in scandium silicide

  19. Resolution of ofloxacin-ciprofloxacin and ofloxacin-norfloxacin binary mixtures by flow-injection chemiluminescence in combination with partial least squares multivariate calibration.

    Science.gov (United States)

    Murillo, J A; Alañón Molina, A; Muñoz de la Peña, A; Durán Merás, I; Jiménez Girón, A

    2007-09-01

    A flow-injection chemiluminescence (CL) method is described for the determination of ciprofloxacin (CIP), norfloxacin (NOR) and ofloxacin (OFL), commonly used antibiotics of the fluoroquinolones family. The method is based on the CL reaction of the fluoroquinolones with tris(2,2'-bipyridyl) ruthenium(II) and Ce (IV), in sulfuric acid medium. The maximum CL emission, given at 0.45 min for CIP, at 0.35 min for NOR and at 0.04 min for OFL, respectively, were measured, allowing the simple application of the proposed method to the routine analysis of the antibiotics. The methods were applied to the determination of CIP, NOR and OFL, in several pharmaceutical preparations, with very satisfactory results, and validated by a previously reported HPLC method. The time-resolved equipment allowed the measurement of the kinetic evolution of the chemiluminescence signals. In base to the differences in the kinetic behaviour of ofloxacin with respect to ciprofloxacin and norfloxacin, binary mixtures of the drugs were resolved by using the time-resolved chemiluminescence signals, in combination with first-order partial least-squares (PLS) multivariate calibration.

  20. Flow injection microfluidic device with on-line fluorescent derivatization for the determination of Cr(III) and Cr(VI) in water samples after solid phase extraction.

    Science.gov (United States)

    Peng, Guilong; He, Qiang; Lu, Ying; Huang, Jing; Lin, Jin-Ming

    2017-02-22

    In this paper, a rapid and simple method using magnetic multi-walled carbon nanotubes (MWCNTS), as a solid-phase extraction (SPE) sorbent, was successfully developed for extraction and preconcentration trace amounts of Cr(III) in water samples. The synthesized magnetic-MWCNTs nanocomposite was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). A rhodamine derivative (R1) was synthesized and characterized as a highly selective and sensitive fluorescent derivatizing agent for Cr(III). After SPE procedure, Cr(III) analysis was performed by flow injection microfluidic chip with on-line fluorescent derivatization and laser-induced fluorescence (LIF) spectroscopy detection. The parameters, which affected the efficiency of the developed method were investigated and optimized. Under the optimized conditions, the method exhibited a linear dynamic range of 0-10.0 nM, with a detection limit of 0.094 nM and an enrichment factor of 38. Furthermore, real water samples were analyzed and good recoveries were obtained from 91.0 to 101.6%. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Automated on-line renewable solid-phase extraction-liquid chromatography exploiting multisyringe flow injection-bead injection lab-on-valve analysis.

    Science.gov (United States)

    Quintana, José Benito; Miró, Manuel; Estela, José Manuel; Cerdà, Víctor

    2006-04-15

    In this paper, the third generation of flow injection analysis, also named the lab-on-valve (LOV) approach, is proposed for the first time as a front end to high-performance liquid chromatography (HPLC) for on-line solid-phase extraction (SPE) sample processing by exploiting the bead injection (BI) concept. The proposed microanalytical system based on discontinuous programmable flow features automated packing (and withdrawal after single use) of a small amount of sorbent (residues (viz., ketoprofen, naproxen, bezafibrate, diclofenac, and ibuprofen) and one metabolite (viz., salicylic acid) in surface water, urban wastewater, and urine. To this end, the copolymeric divinylbenzene-co-n-vinylpyrrolidone beads (Oasis HLB) were utilized as renewable sorptive entities in the micromachined unit. The automated analytical method features relative recovery percentages of >88%, limits of detection within the range 0.02-0.67 ng mL(-1), and coefficients of variation <11% for the column renewable mode and gives rise to a drastic reduction in operation costs ( approximately 25-fold) as compared to on-line column switching systems.

  2. On-line Speciation of Cr(III) and Cr(VI) by Flow Injection Analysis With Spectrophotometric Detection and Chemometrics

    DEFF Research Database (Denmark)

    Diacu, Elena; Andersen, Jens Enevold Thaulov

    2003-01-01

    A flow injection system has been developed, for on-line speciation. of Cr(III) and Cr(VI) by the Diphenylcarbazide (DPC) method with H2O2 oxidation followed by spectrophotometric detection at the 550 nm wavelength. The data thus obtained were subjected to a chemometric analysis (PLS), which showed...... that it was possible to obtain reliable predictions of Cr(III) and Cr(VI) species. The method was validated on samples of stainless steel. In order to facilitate analysis of stainless-steel samples it was essential to perform a step of evaporation to dryness followed by re-dissolution. The analysis showed that species...... of Cr(III) and Cr(VI) coexisted in the samples digested by this method, By spiking the samples with iron and nickel species, it was found that, although the total amount of chromium remained constant, the equilibrium of the two chromium species was displaced towards Cr(III). A detection limit of 10 mug...

  3. Flow injection on-line dilution for multi-element determination in human urine with detection by inductively coupled plasma mass spectrometry

    DEFF Research Database (Denmark)

    Wang, Jianhua; Hansen, Elo Harald; Gammelgaard, Bente

    2001-01-01

    A simple flow injection on-line dilution procedure with detection by inductively coupled plasma mass spectrometry (ICP-MS) was developed for the determination of copper, zinc, arsenic, lead, selenium, nickel and molybdenum in human urine. Matrix effects were minimized by employing a dilution factor...... of 16.5 with on-line standard addition, and sup/ 103/Rh was used as internal standard to compensate for signal fluctuation. The procedure was validated by the analysis of two standard reference materials SRM 2670 (NIST) and Seronorm(TM) Trace Elements in Urine. Recovery experiments were performed...... by spiking the reference materials as well as artificial urine. The detection limits (mug/l were 0.12, 0.96, 0.30, 0.09, 0.45, 0.08, 0.09, and the precisions (RSD,%) were 2.6, 2.3, 3.0, 3.7, 3.7, 4.9, 2.8 for Cu, Zn, As, Pb, Se, Ni and Mo, respectively. The procedure was applied to the analysis of 41 human...

  4. Design and integration of a generic disposable array-compatible sensor housing into an integrated disposable indirect microfluidic flow injection analysis system.

    Science.gov (United States)

    Rapp, Bastian E; Schickling, Benjamin; Prokop, Jürgen; Piotter, Volker; Rapp, Michael; Länge, Kerstin

    2011-10-01

    We describe an integration strategy for arbitrary sensors intended to be used as biosensors in biomedical or bioanalytical applications. For such devices ease of handling (by a potential end user) as well as strict disposable usage are of importance. Firstly we describe a generic array compatible polymer sensor housing with an effective sample volume of 1.55 μl. This housing leaves the sensitive surface of the sensor accessible for the application of biosensing layers even after the embedding. In a second step we show how this sensor housing can be used in combination with a passive disposable microfluidic chip to set up arbitrary 8-fold sensor arrays and how such a system can be complemented with an indirect microfluidic flow injection analysis (FIA) system. This system is designed in a way that it strictly separates between disposable and reusable components- by introducing tetradecane as an intermediate liquid. This results in a sensor system compatible with the demands of most biomedical applications. Comparative measurements between a classical macroscopic FIA system and this integrated indirect microfluidic system are presented. We use a surface acoustic wave (SAW) sensor as an exemplary detector in this work.

  5. A comparison of continuous pneumatic nebulization and flow injection-direct injection nebulization for sample introduction in inductively coupled plasma-mass spectrometry

    International Nuclear Information System (INIS)

    Crain, J.S.; Kiely, J.T.

    1995-08-01

    Dilute nitric acid blanks and solutions containing Ni, Cd, Pb, and U (including two laboratory waste samples) were analyzed eighteen times over a two-month period using inductively coupled plasma-mass spectrometry (ICP-MS). Two different sample introduction techniques were employed: flow injection-direct injection nebulization (FI-DIN) and continuous pneumatic nebulization (CPN). Using comparable instrumental measurement procedures, FI-DIN analyses were 33% faster and generated 52% less waste than CPN analyses. Instrumental limits of detection obtained with FI-DIN and CPN were comparable but not equivalent (except in the case of Pb) because of nebulizer-related differences in sensitivity (i.e., signal per unit analyte concentration) and background. Substantial and statistically significant differences were found between FI-DIN and CPN Ni determinations, and in the case of the laboratory waste samples, there were also small but statistically significant differences between Cd determinations. These small (2 to 3%) differences were not related to polyatomic ion interference (e.g., 95 Mo 16 O + ), but in light of the time savings and waste reduction to be realized, they should not preclude the use of FI-DIN in place of CPN for determination of Cd, Pb, U and chemically

  6. Masking Agents Evaluation for Lead Determination by Flow Injection-Hydride Generation-Atomic Fluorescence Spectrometry Technique: Effect of KI, L-Cysteine, and 1,10-Phenanthroline

    Directory of Open Access Journals (Sweden)

    Blanca G. Beltrán

    2016-01-01

    Full Text Available Hydride generation (HG of lead technique presents interferences from foreign ions of complex matrix samples. In order to minimize these interferences, the effect of masking agents such as KI, L-cysteine, and 1,10-phenanthroline was studied in the absence and in the presence of selected interfering species (As, Cr, Cu, and Fe. Different modes of addition of masking agents were accomplished, that is, to either sample or KBH4 reducing solution. The lead determinations were performed using a flow injection analysis (FIA system coupled to HG and atomic fluorescence spectrometry (AFS. The linearity of calibration curves (1–10 μg Pb L−1 was not affected by the addition of the masking agents. The use of KI in the reducing solution diminished interferences from concentrations of As and Cu, while 1,10-phenanthroline showed a positive effect on the interference by As. Moreover, Cr and Cu appeared to be the most serious interfering ions for plumbane (PbH4, because they drastically reduced the analytical signal of lead. Fe did not present any interference under the employed experimental conditions, even at high levels. The accuracy was established through the analysis of certified reference material (i.e., BCR-610, groundwater using KI as masking agent. The detection limit reached by FIA-HG-AFS proposed methodology was 0.03 μg Pb L−1.

  7. Highly sensitive determination of diclofenac based on resin beads and a novel polyclonal antibody by using flow injection chemiluminescence competitive immunoassay

    Science.gov (United States)

    Shi, Jing; Xu, Mingxia; Tang, Qinghui; Zhao, Kang; Deng, Anping; Li, Jianguo

    2018-02-01

    A novel flow injection chemiluminescence immunoassay for simple, sensitive and low-cost detection of diclofenac was established based on specific binding of antigen and antibody. Carboxylic resin beads used as solid phase carrier materials provided good biocompatibility and large surface-to-volume ratio for modifying more coating antigen. There was a competitive process between the diclofenac in solution and the immobilized coating antigen to react with the limited binding sites of the polyclonal antibody to form the immunocomplex. The second antibody labelled with horseradish peroxidase was introduced into the immunosensor and trapped by captured polyclonal antibody against diclofenac, which could effectively amplify chemiluminescence signals of luminol-PIP-H2O2. Under optimal conditions, the diclofenac could be detected quantitatively. The chemiluminescence intensity decreased linearly with the logarithm of the diclofenac concentration in the range of 0.1-100 ng mL- 1 with a detection limit of 0.05 ng mL- 1 at a signal-to-noise ratio of 3. The immunosensor exhibited high sensitivity, specificity and acceptable stability. This easy-operated and cost-effective analytical method could be valuable for the diclofenac determination in real water samples.

  8. Flow injection determination of diclofenac sodium based on its sensitizing effect on the chemiluminescent reaction of acidic potassium permanganate-formaldehyde.

    Science.gov (United States)

    Song, Jingjing; Sun, Pulv; Ji, Zhongling; Li, Jianguo

    2015-02-01

    A sensitive and simple chemiluminescent (CL) method for the determination of diclofenac sodium has been developed by combining the flow injection technique and its sensitizing effect on the weak CL reaction between formaldehyde and acidic potassium permanganate. A calibration curve is constructed for diclofenac sodium under optimized experimental parameters over the range 0.040-5.0 µg/mL and the limit of detection is 0.020 µg/mL (3σ). The inter-assay relative standard deviation for 0.040 µg/mL diclofenac sodium (n = 11) is 2.0%. This method is rapid, sensitive, simple, and shows good selectivity and reproducibility. The proposed method has been successfully applied to the determination of the studied diclofenac sodium in pharmaceutical preparations with satisfactory results. Furthermore, the possible mechanism for the CL reaction has been discussed in detail on the basis of UV and CL spectra. Copyright © 2014 John Wiley & Sons, Ltd.

  9. Fast Determination of Yttrium and Rare Earth Elements in Seawater by Inductively Coupled Plasma-Mass Spectrometry after Online Flow Injection Pretreatment

    Directory of Open Access Journals (Sweden)

    Zuhao Zhu

    2018-02-01

    Full Text Available A method for daily monitoring of yttrium and rare earth elements (YREEs in seawater using a cheap flow injection system online coupled to inductively coupled plasma-mass spectrometry is reported. Toyopearl AF Chelate 650M® resin permits separation and concentration of YREEs using a simple external calibration. A running cycle consumed 6 mL sample and took 5.3 min, providing a throughput of 11 samples per hour. Linear ranges were up to 200 ng kg−1 except Tm (100 ng kg−1. The precision of the method was <6% (RSDs, n = 5, and recoveries ranged from 93% to 106%. Limits of detection (LODs were in the range 0.002 ng kg−1 (Tm to 0.078 ng kg−1 (Ce. Good agreement between YREEs concentrations in CASS-4 and SLEW-3 obtained in this work and results from other studies was observed. The proposed method was applied to the determination of YREEs in seawater from the Jiulong River Estuary and the Taiwan Strait.

  10. Fast Determination of Yttrium and Rare Earth Elements in Seawater by Inductively Coupled Plasma-Mass Spectrometry after Online Flow Injection Pretreatment.

    Science.gov (United States)

    Zhu, Zuhao; Zheng, Airong

    2018-02-23

    A method for daily monitoring of yttrium and rare earth elements (YREEs) in seawater using a cheap flow injection system online coupled to inductively coupled plasma-mass spectrometry is reported. Toyopearl AF Chelate 650M ® resin permits separation and concentration of YREEs using a simple external calibration. A running cycle consumed 6 mL sample and took 5.3 min, providing a throughput of 11 samples per hour. Linear ranges were up to 200 ng kg -1 except Tm (100 ng kg -1 ). The precision of the method was <6% (RSDs, n = 5), and recoveries ranged from 93% to 106%. Limits of detection (LODs) were in the range 0.002 ng kg -1 (Tm) to 0.078 ng kg -1 (Ce). Good agreement between YREEs concentrations in CASS-4 and SLEW-3 obtained in this work and results from other studies was observed. The proposed method was applied to the determination of YREEs in seawater from the Jiulong River Estuary and the Taiwan Strait.

  11. Flow-injection chemiluminescence assay for ultra-trace determination of DNA using rhodamine B-Ce(IV)-DNA ternary system in sulfuric acid media

    Energy Technology Data Exchange (ETDEWEB)

    Ma Yongjun; Zhou Min; Jin Xiaoyong; Zhang Ziyu; Teng Xiulan; Chen Hui

    2004-01-09

    A novel flow-injection chemiluminescence method for the determination of DNA at ultra-trace level has been established. In 0.8 M sulfuric acid media, the chemiluminescence of the rhodamine B-cerium (IV) or Ce(IV) system is enhanced by DNA, activated previously by imidazole-HCl buffer solution (pH 7.0). The enhanced intensity of chemiluminescence is in proportion to log DNA concentration 1.0x10{sup -8} to 0.1 {mu}g ml{sup -1} for herring sperm DNA and 2.0x10{sup -6} to 0.2 {mu}g ml{sup -1} for calf thymus DNA with 3{sigma} detection limits of 8.3x10{sup -9} {mu}g ml{sup -1} for herring sperm DNA and 3.5x10{sup -7} {mu}g ml{sup -1} for calf thymus DNA, respectively. The relative standard deviation for 1.0x10{sup -4} {mu}g ml{sup -1} herring sperm DNA was 0.99% and 2.0x10{sup -3} {mu}g ml{sup -1} for calf thymus DNA was 1.1% (n=11). Using the optimized system, DNA contents in six synthetic samples has been determined with recoveries of 99.5-109.0%. The possible mechanism has also been studied in this paper.

  12. Flow-injection chemiluminescence assay for ultra-trace determination of DNA using rhodamine B-Ce(IV)-DNA ternary system in sulfuric acid media

    International Nuclear Information System (INIS)

    Ma Yongjun; Zhou Min; Jin Xiaoyong; Zhang Ziyu; Teng Xiulan; Chen Hui

    2004-01-01

    A novel flow-injection chemiluminescence method for the determination of DNA at ultra-trace level has been established. In 0.8 M sulfuric acid media, the chemiluminescence of the rhodamine B-cerium (IV) or Ce(IV) system is enhanced by DNA, activated previously by imidazole-HCl buffer solution (pH 7.0). The enhanced intensity of chemiluminescence is in proportion to log DNA concentration 1.0x10 -8 to 0.1 μg ml -1 for herring sperm DNA and 2.0x10 -6 to 0.2 μg ml -1 for calf thymus DNA with 3σ detection limits of 8.3x10 -9 μg ml -1 for herring sperm DNA and 3.5x10 -7 μg ml -1 for calf thymus DNA, respectively. The relative standard deviation for 1.0x10 -4 μg ml -1 herring sperm DNA was 0.99% and 2.0x10 -3 μg ml -1 for calf thymus DNA was 1.1% (n=11). Using the optimized system, DNA contents in six synthetic samples has been determined with recoveries of 99.5-109.0%. The possible mechanism has also been studied in this paper

  13. A catalytic spectrophotometric method for determination of nanomolar manganese in seawater using reverse flow injection analysis and a long path length liquid waveguide capillary cell.

    Science.gov (United States)

    Feng, Sichao; Yuan, Dongxing; Huang, Yongming; Lin, Kunning; Zhu, Yong; Ma, Jian

    2018-02-01

    A sensitive and precise method for determination of nanomolar manganese in seawater was developed, using reverse flow injection analysis, a long path length liquid waveguide capillary cell, and spectrophotometric detection. The reaction was based on manganese catalyzed oxidation of leucomalachite green with sodium periodate. Various experimental parameters were investigated and optimized. Foreign trace metal ions of iron, copper, zinc, nickel and aluminum did not cause obvious interference with manganese detection. Low manganese seawater was prepared and used as the blank and standards' matrix, to eliminate the seawater matrix effect. The method detection limit was 0.20nmolL -1 , and the quantification range was 0.50-10.00nmolL -1 , which should be sensitive enough and suitable for open ocean seawater analysis. The seawater certified reference material NASS-6 was used to test the accuracy, and good agreement was obtained. The proposed method was applied to analyze seawater samples collected at the SEATS station in the South China Sea. The vertical profile of the total dissolvable manganese is reported and discussed. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Subnanogram determination of aniracetam in pharmaceutical preparations and biofluids by flow injection analysis with chemiluminescence detection based on its enhancement of the myoglobin-luminol reaction.

    Science.gov (United States)

    Shao, Xiaodong; Li, Ying; Li, Fagen; Liu, Yangqin; Song, Zhenghua

    2011-01-01

    A novel flow injection chemiluminescence method with a myoglobin-luminol system is described for determining aniracetam. Myoglobin-bound aniracetam produced a complex that catalyzed the chemiluminescence reaction between luminol and myoglobin, leading to fast chemiluminescence. The chemiluminescence intensity in the presence of aniracetam was remarkably enhanced compared with that in the absence of aniracetam. Under the optimum reaction conditions the chemiluminescence increment produced was proportional to the concentration of aniracetam in the range of 0.1-1000.0 ng/mL (R2 = 0.9992), with a detection limit of 0.03 ng/mL (3delta). At a flow rate of 2.0 mL/min, the whole process, including sampling and washing, could be completed in 0.5 min, offering a sampling efficiency of 120/h; the RSD was less than 3.0% (n = 5). The method was satisfactory for determination of aniracetam in pharmaceutical preparations and human urine and serum samples. A possible mechanism of the reaction is also discussed.

  15. Immobilized stearic acid as a new sorbent for on-line preconcentration and determination of lead by flow injection flame atomic absorption spectrometry

    Directory of Open Access Journals (Sweden)

    Dadfarnia Shayessteh

    2006-01-01

    Full Text Available The present study examines the possibility of immobilization of stearic acid on microcrystalline naphthalene for preparation of microcolumn and evaluation of its potential for adsorption and preconcentration of trace amounts of metal ions. It was found that this sorbent has high affinity for lead. Consequently, a rapid on-line preconcentration technique for the determination of lead by Flow Injection Flame Atomic Absorption Spectrometry had been devised. Preconcentration was based on accumulation of analyte on immobilized stearic acid microcolumn and subsequent elution by injection of a small volume of nitric acid (250 µL of 1 mol L-1. A sample volume of 20 mL resulted in a preconcentration factor of 84, and relative standard deviations for solutions containing 40 and 200 µg L-1 were 5.1 and 1.2%, respectively. The procedure was applied to tap water, river water, sea water, apple juice, beet leaf, urine, and certified stainless steel. The accuracy was proved by performing recovery experiments, Graphite Furnace Atomic Absorption Spectrometry measurements, and analysis of a stainless steel certified reference material.

  16. A Green Analytical Method Using Ultrasound in Sample Preparation for the Flow Injection Determination of Iron, Manganese, and Zinc in Soluble Solid Samples by Flame Atomic Absorption Spectrometry

    Directory of Open Access Journals (Sweden)

    M. Carmen Yebra

    2012-01-01

    Full Text Available A simple and rapid analytical method was developed for the determination of iron, manganese, and zinc in soluble solid samples. The method is based on continuous ultrasonic water dissolution of the sample (5–30 mg at room temperature followed by flow injection flame atomic absorption spectrometric determination. A good precision of the whole procedure (1.2–4.6% and a sample throughput of ca. 25 samples h–1 were obtained. The proposed green analytical method has been successfully applied for the determination of iron, manganese, and zinc in soluble solid food samples (soluble cocoa and soluble coffee and pharmaceutical preparations (multivitamin tablets. The ranges of concentrations found were 21.4–25.61 μg g-1 for iron, 5.74–18.30 μg g-1 for manganese, and 33.27–57.90 μg g-1 for zinc in soluble solid food samples and 3.75–9.90 μg g-1 for iron, 0.47–5.05 μg g-1 for manganese, and 1.55–15.12 μg g-1 for zinc in multivitamin tablets. The accuracy of the proposed method was established by a comparison with the conventional wet acid digestion method using a paired t-test, indicating the absence of systematic errors.

  17. The use of a polymer inclusion membrane as a sorbent for online preconcentration in the flow injection determination of thiocyanate impurity in ammonium sulfate fertilizer.

    Science.gov (United States)

    Ohshima, Takumi; Kagaya, Shigehiro; Gemmei-Ide, Makoto; Cattrall, Robert W; Kolev, Spas D

    2014-11-01

    A polymer inclusion membrane (PIM) is used for the first time as a sorbent in the construction of a preconcentration column to enhance the sensitivity in flow injection analysis (FIA). The PIM-coated column is readily prepared by coating the PIM containing poly(vinyl chloride), Aliquat 336, and 1-tetradecanol onto glass beads packed in a glass tube. The determination of trace amounts of thiocyanate in ammonium sulfate fertilizer demonstrates the potential of the proposed PIM-coated column in FIA. Thiocyanate standards or samples of relatively large volume (e.g. up to 2000 µL) are injected into a nitrate carrier stream. The sample zone passes through the proposed preconcentration column where thiocyanate is concentrated in a smaller volume of a carrier solution thus resulting in up to 7.4 fold increase in sensitivity. Thiocyanate is detected spectrophotometrically after its reaction with Fe(III) downstream of the preconcentration column. The limits of detection of thiocyanate in the absence and presence of 20 g L(-1) ammonium sulfate (S/N=2) are 0.014 and 0.024 mg L(-1), respectively. Thiocyanate was successfully determined in several samples of ammonium sulfate fertilizer. Copyright © 2014 Elsevier B.V. All rights reserved.

  18. Trace mercury determination in drinking and natural water samples by room temperature ionic liquid based-preconcentration and flow injection-cold vapor atomic absorption spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Martinis, Estefania M.; Berton, Paula [Laboratory of Environmental Research and Services of Mendoza (LISAMEN), (CCT - CONICET - Mendoza), Av. Ruiz Leal S/N Parque General San Martin, CC. 131, M 5502 IRA Mendoza (Argentina); Olsina, Roberto A. [INQUISAL-CONICET, Departamento de Quimica Analitica, Facultad de Quimica, Bioquimica y Farmacia, Universidad Nacional de San Luis, San Luis (Argentina); Altamirano, Jorgelina C. [Laboratory of Environmental Research and Services of Mendoza (LISAMEN), (CCT - CONICET - Mendoza), Av. Ruiz Leal S/N Parque General San Martin, CC. 131, M 5502 IRA Mendoza (Argentina); Instituto de Ciencias Basicas, Universidad Nacional de Cuyo, Mendoza (Argentina); Wuilloud, Rodolfo G., E-mail: rwuilloud@lab.cricyt.edu.ar [Laboratory of Environmental Research and Services of Mendoza (LISAMEN), (CCT - CONICET - Mendoza), Av. Ruiz Leal S/N Parque General San Martin, CC. 131, M 5502 IRA Mendoza (Argentina); Instituto de Ciencias Basicas, Universidad Nacional de Cuyo, Mendoza (Argentina)

    2009-08-15

    A liquid-liquid extraction procedure (L-L) based on room temperature ionic liquid (RTIL) was developed for the preconcentration and determination of mercury in different water samples. The analyte was quantitatively extracted with 1-butyl-3-methylimidazolium hexafluorophosphate ([C{sub 4}mim][PF{sub 6}]) under the form of Hg-2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Hg-5-Br-PADAP) complex. A volume of 500 {mu}l of 9.0 mol L{sup -1} hydrochloric acid was used to back-extract the analyte from the RTIL phase into an aqueous media prior to its analysis by flow injection-cold vapor atomic absorption spectrometry (FI-CV-AAS). A preconcentration factor of 36 was achieved upon preconcentration of 20 mL of sample. The limit of detection (LOD) obtained under the optimal conditions was 2.3 ng L{sup -1} and the relative standard deviation (RSD) for 10 replicates at 1 {mu}g L{sup -1} Hg{sup 2+} was 2.8%, calculated with peaks height. The method was successfully applied to the determination of mercury in river, sea, mineral and tap water samples and a certified reference material (CRM).

  19. A rapid and accurate method for determining protein content in dairy products based on asynchronous-injection alternating merging zone flow-injection spectrophotometry.

    Science.gov (United States)

    Liang, Qin-Qin; Li, Yong-Sheng

    2013-12-01

    An accurate and rapid method and a system to determine protein content using asynchronous-injection alternating merging zone flow-injection spectrophotometry based on reaction between coomassie brilliant blue G250 (CBBG) and protein was established. Main merit of our approach is that it can avoid interferences of other nitric-compounds in samples, such as melamine and urea. Optimized conditions are as follows: Concentrations of CBBG, polyvinyl alcohol (PVA), NaCl and HCl are 150 mg/l, 30 mg/l, 0.1 mol/l and 1.0% (v/v), respectively; volumes of the sample and reagent are 150 μl and 30 μl, respectively; length of a reaction coil is 200 cm; total flow rate is 2.65 ml/min. The linear range of the method is 0.5-15 mg/l (BSA), its detection limit is 0.05 mg/l, relative standard deviation is less than 1.87% (n=11), and analytical speed is 60 samples per hour. Copyright © 2013 Elsevier Ltd. All rights reserved.

  20. CuO nanosheets-enhanced flow-injection chemiluminescence system for determination of vancomycin in water, pharmaceutical and human serum

    Science.gov (United States)

    Khataee, A. R.; Hasanzadeh, A.; Iranifam, M.; Fathinia, M.; Hanifehpour, Y.; Joo, S. W.

    2014-03-01

    A novel, rapid and sensitive CuO nanosheets (NSs) amplified flow-injection chemiluminescence (CL) system, luminol-H2O2-CuO nanosheets, was developed for determination of the vancomycin hydrochloride for the first time. It was found that vancomycin could efficiently inhibit the CL intensity of luminol-H2O2-CuO nanosheets system in alkaline medium. Under the optimum conditions, the inhibited CL intensity was linearly proportional to the concentration of vancomycin over the ranges of 0.5-18.0 and 18.0-40.0 mg L-1, with a detection limit (3σ) of 0.1 mg L-1. The precision was calculated by analyzing samples containing 5.0 mg L-1 vancomycin (n = 11) and the relative standard deviation (RSD) was 2.8%. Also, a high injection throughput of 120 sample h-1 was obtained. The CuO nanosheets were synthesized by a sonochemical method. Also, X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were employed to characterize the CuO nanosheets. The method was successfully employed to determine vancomycin hydrochloride in environmental water samples, pharmaceutical formulation and spiked human serum.

  1. Preparation of Fe(3)O(4)@C@CNC multifunctional magnetic core/shell nanoparticles and their application in a signal-type flow-injection photoluminescence immunosensor.

    Science.gov (United States)

    Chu, Chengchao; Li, Meng; Li, Long; Ge, Shenguang; Ge, Lei; Yu, Jinghua; Yan, Mei; Song, Xianrang

    2013-11-01

    We describe here the preparation of carbon-coated Fe3O4 magnetic nanoparticles that were further fabricated into multifunctional core/shell nanoparticles (Fe3O4@C@CNCs) through a layer-by-layer self-assembly process of carbon nanocrystals (CNCs). The nanoparticles were applied in a photoluminescence (PL) immunosensor to detect the carcinoembryonic antigen (CEA), and CEA primary antibody was immobilized onto the surface of the nanoparticles. In addition, CEA secondary antibody and glucose oxidase were covalently bonded to silica nanoparticles. After stepwise immunoreactions, the immunoreagent was injected into the PL cell using a flow-injection PL system. When glucose was injected, hydrogen peroxide was obtained because of glucose oxidase catalysis and quenched the PL of the Fe3O4@C@CNC nanoparticles. The here proposed PL immunosensor allowed us to determine CEA concentrations in the 0.005–50 ng·mL-1 concentration range, with a detection limit of 1.8 pg·mL-1.

  2. Separation and preconcentration system based on microextraction with ionic liquid for determination of copper in water and food samples by stopped-flow injection spectrofluorimetry.

    Science.gov (United States)

    Zeeb, Mohsen; Ganjali, Mohammad Reza; Norouzi, Parviz; Kalaee, Mohamad Reza

    2011-05-01

    In this work, an efficient in situ solvent formation microextraction (ISFME) was combined with stopped-flow injection spectrofluorimetry (SFIS) for the determination of copper. In the proposed approach, thiamine was oxidized with copper(II) to form hydrophobic and highly fluorescent thiochrome (TC), which was subsequently extracted into ionic liquid as an extractant phase. A small amount of an ion-pairing agent (NaPF(6)) was added to the sample solution containing a water-miscible ionic liquid ([Hmim][BF(4)]) to obtain a hydrophobic ionic liquid ([Hmim][PF(6)]), which acted as the extraction phase. After centrifuging, phase separation was performed and the enriched analyte was determined by SFIS. ISFME is an efficient method for separation and preconcentration of metal ions from aqueous solutions with a high ionic strength. Variables affecting the analytical performance were studied and optimized. Under optimum experimental conditions, the proposed method provided a limit of detection (LOD) of 0.024μgL(-1) and a relative standard deviation (RSD) of 2.1%. The accuracy of the combined methodology was evaluated by recovery experiments and by analyzing certified reference material (GBW 07605 Tea). Finally, the proposed method was successfully applied to copper determination in water and food samples. Copyright © 2011 Elsevier Ltd. All rights reserved.

  3. One-shot flow injection spectrophotometric simultaneous determination of copper, iron and zinc in patients' sera with newly developed multi-compartment flow cell

    International Nuclear Information System (INIS)

    Teshima, Norio; Gotoh, Shingo; Ida, Kazunori; Sakai, Tadao

    2006-01-01

    We propose here an affordable flow injection method for simultaneous spectrophotometric determination of copper, iron and zinc in patients' sera. The use of a newly designed multi-compartment flow cell allowed the simultaneous determination of the three metals with a single injection ('one-shot') and a double beam spectrophotometer. The chemistry relied on the reactions of these metals with 2-(5-nitro-2-pyridylazo)-5-[N-propyl-N-(3-sulfopropyl)amino]phenol (nitro-PAPS) to form corresponding colored complexes. At pH 3.8, only copper-nitro-PAPS complex was formed in the presence of pyrophosphate as a masking agent for iron, and then the copper and iron(II) complexes were formed in the presence of reductant (ascorbic acid) at the same pH, and finally all three metals reacted with nitro-PAPS at pH 8.6. The characteristics were introduced into the flow system to determine each metal selectively and sensitively. Under the optimum conditions, linear calibration curves for the three metals were obtained in the range of 0.01-1 mg L -1 with a sample throughput rate of 20 h -1 . The limits of detection (3σ) were 3.9 μg L -1 for copper, 4.1 μg L -1 for iron and 4.0 μg L -1 for zinc. The proposed method was applied to analysis of some patients' sera

  4. Determination of phosphate in hydroponic nutrient solutions using flow injection potentiometry and a cobalt-wire phosphate ion-selective electrode.

    Science.gov (United States)

    De Marco, Roland; Phan, Cam

    2003-08-29

    The direct flow injection potentiometric (FIP) analysis of phosphate in hydroponic nutrient solution has been carried out using a cobalt-wire ion-selective electrode (ISE). Synthetic hydroponic nutrient solution, commercial hydroponic nutrient solution and working hydroponic farm nutrient solution were analysed for phosphate using the FIP technique. It is shown that FIP results compare favourably to standard methods of analysis such as spectrophotometry and indirect photometric ion-pair chromatography. Reproducible FIP response curves with a slope of -(47.57+/-0.03) mV per decade and intercept of -(169.7+/-0.1) mV were obtained for four separate calibrations in the concentration range 5.0 x 10(-4)-1.0 x 10(-2) M H(2)PO(4)(-). Anion corrections for interferences by Cl(-), NO(3)(-) and SO(4)(2-) were applied to all samples using the selectivity coefficients determined independently using a fixed interference method. Nevertheless, it was found that anion corrections were not necessary, as the deviations fell within the bounds of experimental error for the cobalt-wire ISE technique (i.e.+/-2-5% R.S.D.). The proposed FIP method enables the direct determination of phosphate in hydroponic nutrient solutions.

  5. A Green Analytical Method Using Ultrasound in Sample Preparation for the Flow Injection Determination of Iron, Manganese, and Zinc in Soluble Solid Samples by Flame Atomic Absorption Spectrometry

    Science.gov (United States)

    Yebra, M. Carmen

    2012-01-01

    A simple and rapid analytical method was developed for the determination of iron, manganese, and zinc in soluble solid samples. The method is based on continuous ultrasonic water dissolution of the sample (5–30 mg) at room temperature followed by flow injection flame atomic absorption spectrometric determination. A good precision of the whole procedure (1.2–4.6%) and a sample throughput of ca. 25 samples h–1 were obtained. The proposed green analytical method has been successfully applied for the determination of iron, manganese, and zinc in soluble solid food samples (soluble cocoa and soluble coffee) and pharmaceutical preparations (multivitamin tablets). The ranges of concentrations found were 21.4–25.61 μg g−1 for iron, 5.74–18.30 μg g−1 for manganese, and 33.27–57.90 μg g−1 for zinc in soluble solid food samples and 3.75–9.90 μg g−1 for iron, 0.47–5.05 μg g−1 for manganese, and 1.55–15.12 μg g−1 for zinc in multivitamin tablets. The accuracy of the proposed method was established by a comparison with the conventional wet acid digestion method using a paired t-test, indicating the absence of systematic errors. PMID:22567553

  6. Flow injection on-line dilution for multi-element determination in human urine with detection by inductively coupled plasma mass spectrometry

    DEFF Research Database (Denmark)

    Wang, J.H.; Hansen, E.H.; Gammelgaard, Bente

    2001-01-01

    A simple flow injection on-line dilution procedure with detection by inductively coupled plasma mass spectrometry (ICP-MS) was developed for the determination of copper, zinc, arsenic, lead, selenium, nickel and molybdenum in human urine. Matrix effects were minimized by employing a dilution fact...... of 16.5 with on-line standard addition, and Rh-103 was used as internal standard to compensate for signal fluctuation. The procedure was validated by the analysis of two standard reference materials SRM 2670 (NIST) and Seronorm (TM) Trace Elements in Urine. Recovery experiments were pet......-formed by spiking the reference materials as well as artificial urine. The detection limits (mug l(-1)) were 0.12, 0.96, 0.30, 0.09, 0.45, 0.08, 0.09, and the precisions (RSD,%) were 2.6, 2.3, 3.0, 3.7, 3.7, 4.9, 2.8 for Cu, Zn, As, Pb, Se, Ni and Mo, respectively. The procedure was applied to the analysis of 41...... human urine samples. No correlations between the concentrations of the elements were observed. (C) 2001 Elsevier Science B.V. All rights reserved...

  7. Determination of scandium in acid mine drainage by ICP-OES with flow injection on-line preconcentration using oxidized multiwalled carbon nanotubes.

    Science.gov (United States)

    Jerez, Javier; Isaguirre, Andrea C; Bazán, Cristian; Martinez, Luis D; Cerutti, Soledad

    2014-06-01

    An on-line scandium preconcentration and determination system implemented with inductively coupled plasma optical emission spectrometry associated with flow injection was studied. Trace amounts of scandium were preconcentrated by sorption on a minicolumn packed with oxidized multiwalled carbon nanotubes, at pH 1.5. The retained analyte was removed from the minicolumn with 30% (v/v) nitric acid. A total enrichment factor of 225-fold was obtained within a preconcentration time of 300 s (for a 25 mL sample volume). The overall time required for preconcentration and elution of 25 mL of sample was about 6 min; the throughput was about 10 samples per hour. The value of the detection limit was 4 ng L(-1) and the precision for 10 replicate determinations at 100 ng L(-1) Sc level was 5% relative standard deviation, calculated from the peak heights obtained. The calibration graph using the preconcentration system was linear with a correlation coefficient of 0.9996 at levels near the detection limits up to at least 10 mg L(-1). After optimization, the method was successfully applied to the determination of Sc in an acid drainage from an abandoned mine located in the province of San Luis, Argentina. Copyright © 2014 Elsevier B.V. All rights reserved.

  8. Establishment of a finite element model for extracting chemical reaction kinetics in a micro-flow injection system with high throughput sampling.

    Science.gov (United States)

    Wu, Zeng-Qiang; Du, Wen-Bin; Li, Jin-Yi; Xia, Xing-Hua; Fang, Qun

    2015-08-01

    Numerical simulation can provide valuable insights for complex microfluidic phenomena coupling mixing and diffusion processes. Herein, a novel finite element model (FEM) has been established to extract chemical reaction kinetics in a microfluidic flow injection analysis (micro-FIA) system using high throughput sample introduction. To reduce the computation burden, the finite element mesh generation is performed with different scales based on the different geometric sizes of micro-FIA. In order to study the contribution of chemical reaction kinetics under non-equilibrium condition, a pseudo-first-order chemical kinetics equation is adopted in the numerical simulations. The effect of reactants diffusion on reaction products is evaluated, and the results demonstrate that the Taylor dispersion plays a determining role in the micro-FIA system. In addition, the effects of flow velocity and injection volume on the reaction product are also simulated. The simulated results agree well with the ones from experiments. Although gravity driven flow is used to the numerical model in the present study, the FEM model also can be applied into the systems with other driving forces such as pressure. Therefore, the established FEM model will facilitate the understanding of reaction mechanism in micro-FIA systems and help us to optimize the manifold of micro-FIA systems. Copyright © 2015 Elsevier B.V. All rights reserved.

  9. Flow injection analysis-flame atomic absorption spectrometry system for indirect determination of sulfite after on-line reduction of solid-phase manganese (IV) dioxide reactor.

    Science.gov (United States)

    Zare-Dorabei, Rouholah; Boroun, Shokoufeh; Noroozifar, Meissam

    2018-02-01

    A new and simple flow injection method followed by atomic absorption spectrometry was developed for indirect determination of sulfite. The proposed method is based on the oxidation of sulfite to sulphate ion using solid-phase manganese dioxide (30% W/W suspended on silica gel beads) reactor. MnO 2 will be reduced to Mn(II) by sample injection in to the column under acidic carrier stream of HNO 3 (pH 2) with flow rate of 3.5mLmin -1 at room temperature. Absorption measurement of Mn(II) which is proportional to the concentration of sulfite in the sample was carried out by atomic absorption spectrometry. The calibration curve was linear up to 25mgL -1 with a detection limit (DL) of 0.08mgL -1 for 400µL injection sample volume. The presented method is efficient toward sulfite determination in sugar and water samples with a relative standard deviation (RSD) less than 1.2% and a sampling rate of about 60h -1 . Copyright © 2017 Elsevier B.V. All rights reserved.

  10. An automated flow injection system for metal determination by flame atomic absorption spectrometry involving on-line fabric disk sorptive extraction technique.

    Science.gov (United States)

    Anthemidis, A; Kazantzi, V; Samanidou, V; Kabir, A; Furton, K G

    2016-08-15

    A novel flow injection-fabric disk sorptive extraction (FI-FDSE) system was developed for automated determination of trace metals. The platform was based on a minicolumn packed with sol-gel coated fabric media in the form of disks, incorporated into an on-line solid-phase extraction system, coupled with flame atomic absorption spectrometry (FAAS). This configuration provides minor backpressure, resulting in high loading flow rates and shorter analytical cycles. The potentials of this technique were demonstrated for trace lead and cadmium determination in environmental water samples. The applicability of different sol-gel coated FPSE media was investigated. The on-line formed complex of metal with ammonium pyrrolidine dithiocarbamate (APDC) was retained onto the fabric surface and methyl isobutyl ketone (MIBK) was used to elute the analytes prior to atomization. For 90s preconcentration time, enrichment factors of 140 and 38 and detection limits (3σ) of 1.8 and 0.4μgL(-1) were achieved for lead and cadmium determination, respectively, with a sampling frequency of 30h(-1). The accuracy of the proposed method was estimated by analyzing standard reference materials and spiked water samples. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. Trace mercury determination in drinking and natural water samples by room temperature ionic liquid based-preconcentration and flow injection-cold vapor atomic absorption spectrometry.

    Science.gov (United States)

    Martinis, Estefanía M; Bertón, Paula; Olsina, Roberto A; Altamirano, Jorgelina C; Wuilloud, Rodolfo G

    2009-08-15

    A liquid-liquid extraction procedure (L-L) based on room temperature ionic liquid (RTIL) was developed for the preconcentration and determination of mercury in different water samples. The analyte was quantitatively extracted with 1-butyl-3-methylimidazolium hexafluorophosphate ([C(4)mim][PF(6)]) under the form of Hg-2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Hg-5-Br-PADAP) complex. A volume of 500 microl of 9.0 mol L(-1) hydrochloric acid was used to back-extract the analyte from the RTIL phase into an aqueous media prior to its analysis by flow injection-cold vapor atomic absorption spectrometry (FI-CV-AAS). A preconcentration factor of 36 was achieved upon preconcentration of 20 mL of sample. The limit of detection (LOD) obtained under the optimal conditions was 2.3ngL(-1) and the relative standard deviation (RSD) for 10 replicates at 1 microg L(-1) Hg(2+) was 2.8%, calculated with peaks height. The method was successfully applied to the determination of mercury in river, sea, mineral and tap water samples and a certified reference material (CRM).

  12. Trace mercury determination in drinking and natural water samples by room temperature ionic liquid based-preconcentration and flow injection-cold vapor atomic absorption spectrometry

    International Nuclear Information System (INIS)

    Martinis, Estefania M.; Berton, Paula; Olsina, Roberto A.; Altamirano, Jorgelina C.; Wuilloud, Rodolfo G.

    2009-01-01

    A liquid-liquid extraction procedure (L-L) based on room temperature ionic liquid (RTIL) was developed for the preconcentration and determination of mercury in different water samples. The analyte was quantitatively extracted with 1-butyl-3-methylimidazolium hexafluorophosphate ([C 4 mim][PF 6 ]) under the form of Hg-2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Hg-5-Br-PADAP) complex. A volume of 500 μl of 9.0 mol L -1 hydrochloric acid was used to back-extract the analyte from the RTIL phase into an aqueous media prior to its analysis by flow injection-cold vapor atomic absorption spectrometry (FI-CV-AAS). A preconcentration factor of 36 was achieved upon preconcentration of 20 mL of sample. The limit of detection (LOD) obtained under the optimal conditions was 2.3 ng L -1 and the relative standard deviation (RSD) for 10 replicates at 1 μg L -1 Hg 2+ was 2.8%, calculated with peaks height. The method was successfully applied to the determination of mercury in river, sea, mineral and tap water samples and a certified reference material (CRM).

  13. Vesicle Motion during Sustained Exocytosis in Chromaffin Cells: Numerical Model Based on Amperometric Measurements.

    Directory of Open Access Journals (Sweden)

    Daungruthai Jarukanont

    Full Text Available Chromaffin cells release catecholamines by exocytosis, a process that includes vesicle docking, priming and fusion. Although all these steps have been intensively studied, some aspects of their mechanisms, particularly those regarding vesicle transport to the active sites situated at the membrane, are still unclear. In this work, we show that it is possible to extract information on vesicle motion in Chromaffin cells from the combination of Langevin simulations and amperometric measurements. We developed a numerical model based on Langevin simulations of vesicle motion towards the cell membrane and on the statistical analysis of vesicle arrival times. We also performed amperometric experiments in bovine-adrenal Chromaffin cells under Ba2+ stimulation to capture neurotransmitter releases during sustained exocytosis. In the sustained phase, each amperometric peak can be related to a single release from a new vesicle arriving at the active site. The amperometric signal can then be mapped into a spike-series of release events. We normalized the spike-series resulting from the current peaks using a time-rescaling transformation, thus making signals coming from different cells comparable. We discuss why the obtained spike-series may contain information about the motion of all vesicles leading to release of catecholamines. We show that the release statistics in our experiments considerably deviate from Poisson processes. Moreover, the interspike-time probability is reasonably well described by two-parameter gamma distributions. In order to interpret this result we computed the vesicles' arrival statistics from our Langevin simulations. As expected, assuming purely diffusive vesicle motion we obtain Poisson statistics. However, if we assume that all vesicles are guided toward the membrane by an attractive harmonic potential, simulations also lead to gamma distributions of the interspike-time probability, in remarkably good agreement with experiment. We

  14. Identification of xenobiotic metabolites from biological fluids using flow injection analysis high-resolution mass spectrometry and post-acquisition data filtering.

    Science.gov (United States)

    Rathahao-Paris, Estelle; Paris, Alain; Bursztyka, Julian; Jaeg, Jean-Philippe; Cravedi, Jean-Pierre; Debrauwer, Laurent

    2014-12-30

    Concern for public health entails the need to evaluate the degree of exposure of population to toxicants. To do this, robust high-throughput approaches are required to be able to perform a large number of analyses in cohort studies. In this study, a data-filtering procedure was applied to mass spectral data acquired by direct analysis of biological fluids leading to rapid detection of metabolites in a model xenobiotic system. Flow injection analysis (FIA) coupled to negative electrospray ionization (ESI)-LTQ Orbitrap Fourier transform mass spectrometry was used to directly analyze urine of rats treated with vinclozolin. Tandem mass spectrometry (MS/MS) experiments were subsequently performed for confirmation of a new metabolite structure. The isotope filtering based on the difference between accurate masses of (35)Cl and (37)Cl was applied to the raw data for the specific detection of ions containing at least one chlorine atom. Seven metabolites of vinclozolin were manually identified thanks to the characteristic isotope pattern of dichlorinated compounds. A new metabolite of vinclozolin was detected for the first time and identified as a sulfate conjugate. The application of an isotope-filtering procedure allowed the selective extraction of pertinent signals from the data. The processed mass spectrum was greatly simplified, significantly facilitating the detection of the seven metabolites previously identified. The use of FIA-HRMS in combination with dedicated bio-informatics data processing is shown to be an efficient approach for the rapid detection of metabolites in biological fluids. This is a very promising high-throughput approach for rapid characterization of the exposure status to xenobiotics. Copyright © 2014 John Wiley & Sons, Ltd.

  15. Flow injection combined with ICP-MS for accurate high throughput analysis of elemental impurities in pharmaceutical products according to USP /.

    Science.gov (United States)

    Fischer, Lisa; Zipfel, Barbara; Koellensperger, Gunda; Kovac, Jessica; Bilz, Susanne; Kunkel, Andrea; Venzago, Cornel; Hann, Stephan

    2014-07-01

    New guidelines of the United States Pharmacopeia (USP), European Pharmacopeia (EP) and international organization (ICH, International Conference on Harmonization) regulating elemental impurity limits in pharmaceuticals seal the end of unspecific analysis of metal(oid)s as outlined in USP and EP 2.4.8. Chapter USP and EP 5.20 as well as drafts from ICH Q3D specify both daily doses and concentration limits of metallic impurities in pharmaceutical final products and in active pharmaceutical ingredients (API) and excipients. In chapters USP and EP 2.4.20 method implementation, validation and quality control during the analytical process are described. By contrast with the--by now--applied methods, substance specific quantitative analysis features new basic requirements, further, significantly lower detection limits ask for the necessity of a general changeover of the methodology toward sensitive multi element analysis by ICP-AES and ICP-MS, respectively. A novel methodological approach based on flow injection analysis and ICP-SFMS/ICP-QMS for the quick and accurate analysis of Cd, Pb, As, Hg, Ir, Os, Pd, Pt, Rh, Ru, Cr, Mo, Ni, V, Cu, Mn, Fe and Zn in drug products by prior dilution, dissolution or microwave assisted closed vessel digestion according to the regulations is presented. In comparison to the acquisition of continuous signals, this method is advantageous with respect to the unprecedented high sample throughput due to a total analysis time of approximately 30s and the low sample consumption of below 50 μL, while meeting the strict USP demands on detection/quantification limits, precision and accuracy. Copyright © 2014 Elsevier B.V. All rights reserved.

  16. Determination of phenols by flow injection and liquid chromatography with on-line quinine-sensitized photo-oxidation and quenched luminol chemiluminescence detection

    International Nuclear Information System (INIS)

    Zhang Wei; Danielson, Neil D.

    2003-01-01

    An on-line quinine-sensitized photo-oxidation with quenched chemiluminescence (CL) detection method is developed for phenols using flow injection (FI) and liquid chromatography (LC). This detection method is based on the decrease of light emission from the luminol CL reaction due to the photo-oxidation of phenols that scavenge the photogenerated reactive oxygen species (e.g. singlet oxygen ( 1 O 2 ) and superoxide (O 2 · - )). On-line photo-oxidation is achieved using a coil photo-reactor made from fluoroethylene-propylene copolymer tubing (3048 mmx0.25 mm i.d.) coiled around a mercury UV lamp. A buffer of pH 7 and a concentration of 350 μM for quinine sulfate are determined optimum for the sensitized photo-oxidation. Using a carrier system flow rate of 60 μl/min, calibration curves taken by FI for 10 phenolic compounds in aqueous solutions showed this decreasing sensitivity order: 4-chlorophenol, phenol, 4-nitrophenol, 3-hydroxy-L-kynurenine, 2-nitrophenol, salicylate, 3-nitrophenol, catechol, 2,4-dinitrophenol, and 2,4-dichlorophenol. This detection method using two tandem coil photo-reactors is also applied for the LC separation of phenol, 4-nitrophenol and 4-chlorophenol on an octadecyl (C18) silica LC column using acetonitrile-H 2 O (40:60, v/v) as a mobile phase. The quenched CL detection limits (about 1 μM or 20 pmol) for phenol and 4-chlorophenol are comparable to those for UV detection at 254 nm. Some selectivity in the quenched CL detection is evident by no interference in the FI phenol response even when benzaldehyde and phenethanol concentrations are 8 and 15 times that of phenol

  17. Slurry sampling flow injection chemical vapor generation inductively coupled plasma mass spectrometry for the determination of trace Ge, As, Cd, Sb, Hg and Bi in cosmetic lotions

    International Nuclear Information System (INIS)

    Chen, Wei-Ni; Jiang, Shiuh-Jen; Chen, Yen-Ling; Sahayam, A.C.

    2015-01-01

    Highlights: • Determination of Ge, As, Cd, Sb, Hg and Bi in cosmetic lotions in a single run. • Accurate analysis using isotope dilution and standard addition methods. • Vapor generation ICP-MS yielded superior detection limits compared to ETV-ICP-MS. • No sample dissolution increased sample through put. • Analysis of GBW09305 Cosmetic (Cream) reference material for accuracy. - Abstract: A slurry sampling inductively coupled plasma mass spectrometry (ICP-MS) method has been developed for the determination of Ge, As, Cd, Sb, Hg and Bi in cosmetic lotions using flow injection (FI) vapor generation (VG) as the sample introduction system. A slurry containing 2% m/v lotion, 2% m/v thiourea, 0.05% m/v L-cysteine, 0.5 μg mL −1 Co(II), 0.1% m/v Triton X-100 and 1.2% v/v HCl was injected into a VG-ICP-MS system for the determination of Ge, As, Cd, Sb, Hg and Bi without dissolution and mineralization. Because the sensitivities of the analytes in the slurry and that of aqueous solution were quite different, an isotope dilution method and a standard addition method were used for the determination. This method has been validated by the determination of Ge, As, Cd, Sb, Hg and Bi in GBW09305 Cosmetic (Cream) reference material. The method was also applied for the determination of Ge, As, Cd, Sb, Hg and Bi in three cosmetic lotion samples obtained locally. The analysis results of the reference material agreed with the certified value and/or ETV-ICP-MS results. The detection limit estimated from the standard addition curve was 0.025, 0.1, 0.2, 0.1, 0.15, and 0.03 ng g −1 for Ge, As, Cd, Sb, Hg and Bi, respectively, in original cosmetic lotion sample

  18. On-line solid-phase extraction and multisyringe flow injection analysis of Al(III) and Fe(III) in drinking water

    Energy Technology Data Exchange (ETDEWEB)

    Vanloot, Pierre; Boudenne, Jean-Luc; Coulomb, Bruno [Universite de Provence - Case 29, Laboratoire de Chimie et Environnement (FRE 2704), Marseille cedex 3 (France); Branger, Catherine; Margaillan, Andre [ISITV - Universite du Sud Toulon Var, Laboratoire de Chimie Appliquee MFS (EA 1356), La Garde du Var (France); Brach-Papa, Christophe [European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, Isotope Measurements Unit, Geel (Belgium)

    2007-11-15

    A new analytical method was developed for on-line monitoring of residual coagulants (aluminium and iron salts) in potable water. The determination was based on a sequential procedure coupling an extraction/enrichment step of the analytes onto a modified resin and a spectrophotometric measurement of a surfactant-sensitized binary complex formed between eluted analytes and Chrome Azurol S. The optimization of the solid phase extraction was performed using factorial design and a Doehlert matrix considering six variables: sample percolation rate, sample metal concentration, flow-through sample volume (all three directly linked to the extraction step), elution flow rate, concentration and volume of eluent (all three directly linked to the elution step). A specific reagent was elaborated for sensitive and specific spectrophotometric determination of Al(III) and Fe(III), by optimizing surfactant and ligand concentrations and buffer composition. The whole procedure was automated by a multisyringe flow injection analysis (MSFIA) system. Detection limits of 4.9 and 5.6 {mu}g L{sup -1} were obtained for Al(III) and Fe(III) determination, respectively, and the linear calibration graph up to 300 {mu}g L{sup -1} (both for Al(III) and Fe(III)) was well adapted to the monitoring of drinking water quality. The system was successfully applied to the on-site determination of Al(III) and Fe(III) at the outlet of two water treatment units during two periods of the year (winter and summer conditions). (orig.)

  19. On-line complexation/cloud point preconcentration for the sensitive determination of dysprosium in urine by flow injection inductively coupled plasma-optical emission spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Ortega, Claudia; Cerutti, Soledad; Silva, Maria F. [Departamento de Quimica Analitica, Facultad de Quimica, Bioquimica y Farmacia, Universidad Nacional de San Luis, Chacabuco y Pedernera, 5700, San Luis (Argentina); Olsina, Roberto A.; Martinez, Luis D. [Departamento de Quimica Analitica, Facultad de Quimica, Bioquimica y Farmacia, Universidad Nacional de San Luis, Chacabuco y Pedernera, 5700, San Luis (Argentina); Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), Avda. Rivadavia 1917, CP C1033AAJJ, Buenos Aires (Argentina)

    2003-01-01

    An on-line dysprosium preconcentration and determination system based on the hyphenation of cloud point extraction (CPE) to flow injection analysis (FIA) associated with ICP-OES was studied. For the preconcentration of dysprosium, a Dy(III)-2-(5-bromo-2-pyridylazo)-5-diethylaminophenol complex was formed on-line at pH 9.22 in the presence of nonionic micelles of PONPE-7.5. The micellar system containing the complex was thermostated at 30 C in order to promote phase separation, and the surfactant-rich phase was retained in a microcolumn packed with cotton at pH 9.2. The surfactant-rich phase was eluted with 4 mol L{sup -1} nitric acid at a flow rate of 1.5 mL min{sup -1}, directly in the nebulizer of the plasma. An enhancement factor of 50 was obtained for the preconcentration of 50 mL of sample solution. The detection limit value for the preconcentration of 50 mL of aqueous solution of Dy was 0.03 {mu}g L{sup -1}. The precision for 10 replicate determinations at the 2.0 {mu}g L{sup -1}Dy level was 2.2% relative standard deviation (RSD), calculated from the peak heights obtained. The calibration graph using the preconcentration system for dysprosium was linear with a correlation coefficient of 0.9994 at levels near the detection limits up to at least 100 {mu}g L {sup -1}. The method was successfully applied to the determination of dysprosium in urine. (orig.)

  20. Slurry sampling flow injection chemical vapor generation inductively coupled plasma mass spectrometry for the determination of trace Ge, As, Cd, Sb, Hg and Bi in cosmetic lotions

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Wei-Ni [Department of Chemistry, National Sun Yat-sen University, Kaohsiung 80424, Taiwan (China); Jiang, Shiuh-Jen, E-mail: sjjiang@faculty.nsysu.edu.tw [Department of Chemistry, National Sun Yat-sen University, Kaohsiung 80424, Taiwan (China); Department of Medical Laboratory Science and Biotechnology, Kaohsiung Medical University, Kaohsiung 80708, Taiwan (China); Chen, Yen-Ling [Department of Fragrance and Cosmetic Science, Kaohsiung Medical University, Kaohsiung 80708, Taiwan (China); Sahayam, A.C. [National Centre for Compositional Characterisation of Materials (CCCM), Hyderabad (India)

    2015-02-20

    Highlights: • Determination of Ge, As, Cd, Sb, Hg and Bi in cosmetic lotions in a single run. • Accurate analysis using isotope dilution and standard addition methods. • Vapor generation ICP-MS yielded superior detection limits compared to ETV-ICP-MS. • No sample dissolution increased sample through put. • Analysis of GBW09305 Cosmetic (Cream) reference material for accuracy. - Abstract: A slurry sampling inductively coupled plasma mass spectrometry (ICP-MS) method has been developed for the determination of Ge, As, Cd, Sb, Hg and Bi in cosmetic lotions using flow injection (FI) vapor generation (VG) as the sample introduction system. A slurry containing 2% m/v lotion, 2% m/v thiourea, 0.05% m/v L-cysteine, 0.5 μg mL{sup −1} Co(II), 0.1% m/v Triton X-100 and 1.2% v/v HCl was injected into a VG-ICP-MS system for the determination of Ge, As, Cd, Sb, Hg and Bi without dissolution and mineralization. Because the sensitivities of the analytes in the slurry and that of aqueous solution were quite different, an isotope dilution method and a standard addition method were used for the determination. This method has been validated by the determination of Ge, As, Cd, Sb, Hg and Bi in GBW09305 Cosmetic (Cream) reference material. The method was also applied for the determination of Ge, As, Cd, Sb, Hg and Bi in three cosmetic lotion samples obtained locally. The analysis results of the reference material agreed with the certified value and/or ETV-ICP-MS results. The detection limit estimated from the standard addition curve was 0.025, 0.1, 0.2, 0.1, 0.15, and 0.03 ng g{sup −1} for Ge, As, Cd, Sb, Hg and Bi, respectively, in original cosmetic lotion sample.

  1. Artificial neural networks study of the catalytic reduction of resazurin: stopped-flow injection kinetic-spectrophotometric determination of Cu(II) and Ni(II)

    International Nuclear Information System (INIS)

    Magni, Diana M.; Olivieri, Alejandro C.; Bonivardi, Adrian L.

    2005-01-01

    An artificial neural network (ANN) procedure was used in the development of a catalytic spectrophotometric method for the determination of Cu(II) and Ni(II) employing a stopped-flow injection system. The method is based on the catalytic action of these ions on the reduction of resazurin by sulfide. ANNs trained by back-propagation of errors allowed us to model the systems in a concentration range of 0.5-6 and 1-15 mg l -1 for Cu(II) and Ni(II), respectively, with a low relative error of prediction (REP) for each cation: REP Cu(II) = 0.85% and REP Ni(II) = 0.79%. The standard deviations of the repeatability (s r ) and of the within-laboratory reproducibility (s w ) were measured using standard solutions of Cu(II) and Ni(II) equal to 2.75 and 3.5 mg l -1 , respectively: s r [Cu(II)] = 0.039 mg l -1 , s r [Ni(II)] = 0.044 mg l -1 , s w [Ni(II)] = 0.045 mg l -1 and s w [Ni(II)] = 0.050 mg l -1 . The ANNs-kinetic method has been applied to the determination of Cu(II) and Ni(II) in electroplating solutions and provided satisfactory results as compared with flame atomic absorption spectrophotometry method. The effect of resazurin, NaOH and Na 2 S concentrations and the reaction temperature on the analytical sensitivity is discussed

  2. A novel solidified floating organic drop microextraction method for preconcentration and determination of copper ions by flow injection flame atomic absorption spectrometry.

    Science.gov (United States)

    Sahin, Ciğdem Arpa; Tokgöz, Ilknur

    2010-05-14

    A rapid, simple and cost effective solidified floating organic drop microextraction (SFODME) and flow injection flame atomic absorption spectrometric determination (FI-FAAS) method for copper was developed. In this method, a free microdrop of 1-undecanol containing 1,5-diphenyl carbazide (DPC) as the complexing agent was transferred to the surface of an aqueous sample including Cu(II) ions, while being agitated by a stirring bar in the bulk of the solution. Under the proper stirring conditions, the suspended microdrop can remain at the top-center position of the aqueous sample. After the completion of the extraction, the sample vial was cooled by placing it in a refrigerator for 10min. The solidified microdrop was then transferred into a conical vial, where it melted immediately and diluted to 300microL with ethanol. Finally, copper ions in 200microL of diluted solution were determined by FI-FAAS. Several factors affecting the microextraction efficiency, such as type of extraction solvent, pH, complexing agent concentration, extraction time, stirring rate, sample volume and temperature were investigated and optimized. Under optimized conditions for 100mL of solution, the preconcentration factor was 333 and the enrichment factor was 324. The limit of detection (3s) was 0.4ngmL(-1), the limit of quantification (10s) was 1.1ngmL(-1) and the relative standard deviation (RSD) for 10 replicate measurements of 10ngmL(-1) copper was 0.9%. The proposed method was successfully applied to the determination of copper in different water samples. Copyright 2010 Elsevier B.V. All rights reserved.

  3. Novel PVC-membrane potentiometric sensors based on a recently synthesized sulfur-containing macrocyclic diamide for Cd2+ ion. Application to flow-injection potentiometry.

    Science.gov (United States)

    Shamsipur, Mojtaba; Dezaki, Abbas Shirmardi; Akhond, Morteza; Sharghi, Hashem; Paziraee, Zahra; Alizadeh, Kamal

    2009-12-30

    A new sulfur-containing macrocyclic diamide, 1,15-diaza-3,4,12,13-dibenzo-5,11-dithia-8-oxa-1,15-(2,6-pyrido)cyclooctadecan-2,14-dione, L, was synthesized, characterized and used as an active component for fabrication of PVC-based polymeric membrane (PME), coated graphite (CGE) and coated silver wire electrodes (CWE) for sensing Cd(2+) ion. The electrodes exhibited linear Nernstian responses to Cd(2+) ion in the concentration range of 3.3 x 10(-6) to 3.3 x 10(-1)M (for PME, LOD=1.2 x 10(-6)M), 2.0 x 10(-7) to 3.3 x 10(-1)M (for CWE, LOD=1.3 x 10(-7)M) and 1.6 x 10(-8) to 1.3 x 10(-1)M (for CGE, LOD=1.0 x 10(-8)M). The CGE was used as a proper detection system in flow-injection potentiometry (FIP) with a linear Nernstian range of 3.2 x 10(-8) to 1.4 x 10(-1)M (LOD=1.3 x 10(-8)M). The optimum pH range was 3.5-7.6. The electrodes revealed fairly good discriminating ability towards Cd(2+) in comparison with a large number of alkali, alkaline earth, transition and heavy metal ions. The electrodes found to be chemically inert, showing a fast response time of <5s, and could be used practically over a period of about 2-3 months. The practical utility of the proposed system has also been reported.

  4. A novel solidified floating organic drop microextraction method for preconcentration and determination of copper ions by flow injection flame atomic absorption spectrometry

    International Nuclear Information System (INIS)

    Sahin, Cigdem Arpa; Tokgoez, Ilknur

    2010-01-01

    A rapid, simple and cost effective solidified floating organic drop microextraction (SFODME) and flow injection flame atomic absorption spectrometric determination (FI-FAAS) method for copper was developed. In this method, a free microdrop of 1-undecanol containing 1,5-diphenyl carbazide (DPC) as the complexing agent was transferred to the surface of an aqueous sample including Cu(II) ions, while being agitated by a stirring bar in the bulk of the solution. Under the proper stirring conditions, the suspended microdrop can remain at the top-center position of the aqueous sample. After the completion of the extraction, the sample vial was cooled by placing it in a refrigerator for 10 min. The solidified microdrop was then transferred into a conical vial, where it melted immediately and diluted to 300 μL with ethanol. Finally, copper ions in 200 μL of diluted solution were determined by FI-FAAS. Several factors affecting the microextraction efficiency, such as type of extraction solvent, pH, complexing agent concentration, extraction time, stirring rate, sample volume and temperature were investigated and optimized. Under optimized conditions for 100 mL of solution, the preconcentration factor was 333 and the enrichment factor was 324. The limit of detection (3 s) was 0.4 ng mL -1 , the limit of quantification (10 s) was 1.1 ng mL -1 and the relative standard deviation (RSD) for 10 replicate measurements of 10 ng mL -1 copper was 0.9%. The proposed method was successfully applied to the determination of copper in different water samples.

  5. Separation and determination of alditols and sugars by high-pH anion-exchange chromatography with pulsed amperometric detection

    DEFF Research Database (Denmark)

    Andersen, Rikke; Sørensen, A.

    2000-01-01

    Carbohydrates such as alditols (polyols or sugar alcohols), monosaccharides and disaccharides are separated as anions by anion-exchange chromatography with a sodium hydroxide eluent, MA1 CarboPac column and pulsed amperometric detection. We report a high-pH anion-exchange chromatographic-pulsed a......Carbohydrates such as alditols (polyols or sugar alcohols), monosaccharides and disaccharides are separated as anions by anion-exchange chromatography with a sodium hydroxide eluent, MA1 CarboPac column and pulsed amperometric detection. We report a high-pH anion-exchange chromatographic......-pulsed amperometric detection (HPAEC-PAD) method that determines all the polyols used as food additives in food products and the most commonly found mono- and disaccharides on a routine basis. The linearity, repeatability, internal reproducibility and accuracy are described. The applicability of the method has been...

  6. Fully automated lab-on-valve-multisyringe flow injection analysis-ICP-MS system: An effective tool for fast, sensitive and selective determination of thorium and uranium at environmental levels exploiting solid phase extraction

    OpenAIRE

    Avivar, Jessica; Ferrer, Laura; Casas, Montserrat; Cerdà, Víctor

    2012-01-01

    An on-line solid-phase extraction method linked to inductively coupled mass spectrometry (ICP-MS) has been developed for the determination of low levels of uranium and thorium in environmental samples. The hyphenation of lab-on-valve (LOV) and multisyringe flow injection analysis (MSFIA), coupled to an ICP-MS, allows the simultaneous determination of thorium and uranium in different types of environmental sample matrices achieving high selectivity and sensitivity levels. On-line separation an...

  7. Signal enhancement in amperometric peroxide detection by using graphene materials with low number of defects

    International Nuclear Information System (INIS)

    Zöpfl, Alexander; Matysik, Frank-Michael; Hirsch, Thomas; Sisakthi, Masoumeh; Eroms, Jonathan; Strunk, Christoph

    2016-01-01

    Two-dimensional carbon nanomaterials ranging from single-layer graphene to defective structures such as chemically reduced graphene oxide were studied with respect to their use in electrodes and sensors. Their electrochemical properties and utility in terms of fabrication of sensing devices are compared. Specifically, the electrodes have been applied to reductive amperometric determination of hydrogen peroxide. Low-defect graphene (SG) was obtained through mechanical exfoliation of natural graphite, while higher-defect graphenes were produced by chemical vapor deposition (CVDG) and by chemical oxidation of graphite and subsequent reduction (rGO). The carbonaceous materials were mainly characterized by Raman microscopy. They were applied as electrode material and the electrochemical behavior was investigated by chronocoulometry, cyclic voltammetry, electrochemical impedance spectroscopy and amperometry and compared to a carbon disc electrode. It is shown that the quality of the graphene has an enormous impact on the amperometric performance. The use of carbon materials with many defects (like rGO) does not result in a significant improvement in signal compared to a plain carbon disc electrode. The sensitivity is 173 mA · M −1  · cm −2 in case of using CVDG which is about 50 times better than that of a plain carbon disc electrode and about 7 times better than that of rGO. The limit of detection for hydrogen peroxide is 15.1 μM (at a working potential of −0.3 V vs SCE) for CVDG. It is concluded that the application of two-dimensional carbon nanomaterials offers large perspectives in amperometric detection systems due to electrocatalytic effects that result in highly sensitive detection. (author)

  8. Creation of a Databank for Content of Antioxidants in Food Products by an Amperometric Method

    Directory of Open Access Journals (Sweden)

    Polina A. Fedina

    2010-10-01

    Full Text Available Oxidative stress, i.e. excessive content of reactionary, oxygen, and nitrogen compounds (ROAC, including free radicals, is one of the causes of various dangerous diseases as well as premature aging. The adverse effect of free radicals can be neutralized by antioxidants. In order to carry out antioxidant therapy, one needs to know the contents of antioxidants in food products. We have created the databank for the contents of antioxidants in 1,140 food products, beverages, etc. Apart from water-soluble antioxidants, fat-soluble antioxidants in dairy and fish products, cacao, chocolate, nuts etc. were determined for the first time using an amperometric method.

  9. Amperometric titration of thorium and some lanthanoids in acetic-acid medium using two indicator electrodes

    International Nuclear Information System (INIS)

    Khadeev, V.A.; Gevorgyan, A.M.; Talipov, Sh.T.; Kostylev, V.S.

    1979-01-01

    The votammetric behaviour of nitriletrimethylphosphonic acid (NTMP) in the medium of anhydrous acetic acid with different backgrounds in the anode region of polarization of a platinum microdisk electrode, is studied. The optimal conditions are found for the amperometric titration with two indicator electrodes of thorium and same lanthanides by a NTMP solution in anhydrous acetic medium. The influence of foreign anions and cations on the results of titration by the NTPM solution in anhydrous acetic acid is studied. The selectivity of titration in anhydrous medium is higher than in aqueous

  10. Determination of As(III) and total inorganic As in water samples using an on-line solid phase extraction and flow injection hydride generation atomic absorption spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Sigrist, Mirna, E-mail: msigrist@fiq.unl.edu.ar [Laboratorio Central, Facultad de Ingenieria Quimica, Universidad Nacional del Litoral, Santiago del Estero 2654-Piso 6, (3000) Santa Fe (Argentina); Albertengo, Antonela; Beldomenico, Horacio [Laboratorio Central, Facultad de Ingenieria Quimica, Universidad Nacional del Litoral, Santiago del Estero 2654-Piso 6, (3000) Santa Fe (Argentina); Tudino, Mabel [Laboratorio de Analisis de Trazas, Departamento de Quimica Inorganica, Analitica y Quimica Fisica/INQUIMAE, Facultad de Ciencias Exactas y Naturales, Pabellon II, Ciudad Universitaria (1428), Buenos Aires (Argentina)

    2011-04-15

    A simple and robust on-line sequential injection system based on solid phase extraction (SPE) coupled to a flow injection hydride generation atomic absorption spectrometer (FI-HGAAS) with a heated quartz tube atomizer (QTA) was developed and optimized for the determination of As(III) in groundwater without any kind of sample pretreatment. The method was based on the selective retention of inorganic As(V) that was carried out by passing the filtered original sample through a cartridge containing a chloride-form strong anion exchanger. Thus the most toxic form, inorganic As(III), was determined fast and directly by AsH{sub 3} generation using 3.5 mol L{sup -1} HCl as carrier solution and 0.35% (m/v) NaBH{sub 4} in 0.025% NaOH as the reductant. Since the uptake of As(V) should be interfered by several anions of natural occurrence in waters, the effect of Cl{sup -}, SO{sub 4}{sup 2-}, NO{sub 3}{sup -}, HPO{sub 4}{sup 2-}, HCO{sub 3}{sup -} on retention was evaluated and discussed. The total soluble inorganic arsenic concentration was determined on aliquots of filtered samples acidified with concentrated HCl and pre-reduced with 5% KI-5% C{sub 6}H{sub 8}O{sub 6} solution. The concentration of As(V) was calculated by difference between the total soluble inorganic arsenic and As(III) concentrations. Detection limits (LODs) of 0.5 {mu}g L{sup -1} and 0.6 {mu}g L{sup -1} for As(III) and inorganic total As, respectively, were obtained for a 500 {mu}L sample volume. The obtained limits of detection allowed testing the water quality according to the national and international regulations. The analytical recovery for water samples spiked with As(III) ranged between 98% and 106%. The sampling throughput for As(III) determination was 60 samples h{sup -1}. The device for groundwater sampling was especially designed for the authors. Metallic components were avoided and the contact between the sample and the atmospheric oxygen was carried to a minimum. On-field arsenic species

  11. Determination of As(III) and total inorganic As in water samples using an on-line solid phase extraction and flow injection hydride generation atomic absorption spectrometry

    International Nuclear Information System (INIS)

    Sigrist, Mirna; Albertengo, Antonela; Beldomenico, Horacio; Tudino, Mabel

    2011-01-01

    A simple and robust on-line sequential injection system based on solid phase extraction (SPE) coupled to a flow injection hydride generation atomic absorption spectrometer (FI-HGAAS) with a heated quartz tube atomizer (QTA) was developed and optimized for the determination of As(III) in groundwater without any kind of sample pretreatment. The method was based on the selective retention of inorganic As(V) that was carried out by passing the filtered original sample through a cartridge containing a chloride-form strong anion exchanger. Thus the most toxic form, inorganic As(III), was determined fast and directly by AsH 3 generation using 3.5 mol L -1 HCl as carrier solution and 0.35% (m/v) NaBH 4 in 0.025% NaOH as the reductant. Since the uptake of As(V) should be interfered by several anions of natural occurrence in waters, the effect of Cl - , SO 4 2- , NO 3 - , HPO 4 2- , HCO 3 - on retention was evaluated and discussed. The total soluble inorganic arsenic concentration was determined on aliquots of filtered samples acidified with concentrated HCl and pre-reduced with 5% KI-5% C 6 H 8 O 6 solution. The concentration of As(V) was calculated by difference between the total soluble inorganic arsenic and As(III) concentrations. Detection limits (LODs) of 0.5 μg L -1 and 0.6 μg L -1 for As(III) and inorganic total As, respectively, were obtained for a 500 μL sample volume. The obtained limits of detection allowed testing the water quality according to the national and international regulations. The analytical recovery for water samples spiked with As(III) ranged between 98% and 106%. The sampling throughput for As(III) determination was 60 samples h -1 . The device for groundwater sampling was especially designed for the authors. Metallic components were avoided and the contact between the sample and the atmospheric oxygen was carried to a minimum. On-field arsenic species separation was performed through the employ of a serial connection of membrane filters and

  12. Flow-through solid-phase based optical sensor for the multisyringe flow injection trace determination of orthophosphate in waters with chemiluminescence detection

    International Nuclear Information System (INIS)

    Morais, Ines P.A.; Miro, Manuel; Manera, Matias; Estela, Jose Manuel; Cerda, Victor; Souto, M. Renata S.; Rangel, Antonio O.S.S.

    2004-01-01

    In this work, a novel flow-through solid-phase based chemiluminescence (CL) optical sensor is described for the trace determination of orthophosphate in waters exploiting the multisyringe flow injection analysis (MSFIA) concept with multicommutation. The proposed time-based injection flow system relies upon the in-line derivatisation of the analyte with ammonium molybdate in the presence of vanadate, and the transient immobilisation of the resulting heteropolyacid in a N-vinylpyrrolidone/divinylbenzene copolymer packed spiral shape flow-through cell located in front of the window of a photomultiplier tube. The simultaneous injection of well-defined slugs of luminol in alkaline medium and methanol solution towards the packed reactor is afterwards performed by proper switching of the solenoid valves. Then, the light emission from the luminol oxidation by the oxidant species retained onto the sorbent material is readily detected. At the same time, the generated molybdenum-blue compound is eluted by the minute amount of injected methanol, rendering the system prepared for a new measuring cycle. Therefore, the devised sensor enables the integration of the solid-phase CL reaction with elution and detection of the emitted light without the typical drawbacks of the molybdenum-blue based spectrophotometric procedures regarding the excess of molybdate anion, which causes high background signals due to its self-reduction. The noteworthy features of the developed CL-MSFIA system are the feasibility to accommodate reactions with different pH requirements and the ability to determine trace levels of orthophosphate in high silicate content samples (Si/P ratios up to 500). Under the optimised conditions, a dynamic linear range from 5 to 50 μg P l -1 for a 1.8 ml sample, repeatability better than 3.0% and a quantification limit of 4 μg P l -1 were attained. The flowing stream system handles 11 analysis h -1 and has been successfully applied to the determination of trace levels of

  13. Ion Imprinted Polymer for Preconcentration and Determination of Ultra-Trace Cadmium, Employing Flow Injection Analysis with Thermo Spray Flame Furnace Atomic Absorption Spectrometry.

    Science.gov (United States)

    do Lago, Ayla Campos; Marchioni, Camila; Mendes, Tássia Venga; Wisniewski, Célio; Fadini, Pedro Sergio; Luccas, Pedro Orival

    2016-11-01

    This work proposes a preconcentration method using an ion imprinted polymer (IIP) for determination of cadmium, in several samples, employing a mini-column filled with the polymer coupled into a flow injection analysis system with detection by thermospray flame furnace atomic absorption spectrometry (FIA-TS-FF-AAS). The polymer was synthesized via bulk using methacrylic acid and vinylimidazole as a functional monomer. For the FIA system initial assessment, the variables: pH, eluent concentration and buffer concentration were studied, employing a 23 full factorial design. To obtain the optimum values for each significant variable, a Doehlert matrix was employed. After the optimization conditions as: pH 5.8, eluent (HNO3) concentration of 0.48 mol L -1 and buffer concentration of 0.01 mol L -1 , were adopted. The proposed method showed a linear response in the range of 0.081-10.0 μg L -1 , limits detection and quantification of 0.024 and 0.081 μg L -1 , respectively; preconcentration factor of 165, consumptive index of 0.06 mL, concentration efficiency 132 min -1 , and frequency of readings equal to 26 readings h -1 The accuracy was checked by analysis of certified reference materials for trace metals and recovery tests. The obtained results were in agreement with 95% confidence level (t-test). The method was adequate to apply in samples of: jewelry (earrings) (2.38 ± 0.28 μg kg -1 ), black tea (1.09 ± 0.15 μg kg -1 ), green tea (3.85 ± 0.13 μg kg -1 ), cigarette tobacco (38.27 ± 0.22 μg kg -1 ), and hair (0.35 ± 0.02 μg kg -1 ). © The Author(s) 2016.

  14. New Signal Transduction Principles for Amperometric Enzyme and Antibody based Sensors

    Science.gov (United States)

    Warsinke, Axel

    2008-10-01

    The way of how the signal transfer from the analyte recognizing biocomponent to the sensor surface is performed influences strongly the characteristics of a biosensor e.g. response time, sensitivity and specificity. Most of the described amperometric enzyme sensors are using oxidases. The signal transduction is carried out simply by electrochemical indication of the produced hydrogen peroxide or via a sensor-immobilized redox polymer. However, due to the limited number of appropriate oxidases the range of detectable analytes is restricted. Hence, we have developed a new general principle for the sensitive transduction of the more than 400 different NAD(P) dependent dehydrogenase reactions. The transduction is based on a hydroxylase reaction which produces an electrochemically active substance under the consumption of NAD(P)H. The principle should be applicable to miniaturized sensor configuration and could be the basis for a new generation of point-of-care devices. For other analytes where no oxidases and dehydrogenases are available antibodies can be used as specific recognition element. We have developed a new principle of redox-labeled immunoassays called size exclusion redox-labeled immunoassay (SERI), where after the antigen antibody binding reaction the indication is carried out amperometrically without a washing step in between. The principle was proved for measurement of creatinine. At the moment the assay needs a relatively high amount of antibodies. However, in future it should be possible to reduce the amount of antibodies by using miniaturized microfluidic chips.

  15. Rapid screening of multiple antibiotic residues in milk using disposable amperometric magnetosensors.

    Science.gov (United States)

    Conzuelo, F; Ruiz-Valdepeñas Montiel, V; Campuzano, S; Gamella, M; Torrente-Rodríguez, R M; Reviejo, A J; Pingarrón, J M

    2014-04-11

    Disposable amperometric magnetosensors, involving a mixture of modified-magnetic beads (MBs), for the multiplex screening of cephalosporins (CPHs), sulfonamides (SAs) and tetracyclines (TCs) antibiotic residues in milk are reported for the first time in this work. The multiplexed detection relies on the use of a mixture of target specific modified magnetic beads (MBs) and application of direct competitive assays using horseradish peroxidase (HRP)-labeled tracers. The amperometric responses measured at -0.20 V vs. the Ag pseudo-reference electrode of screen-printed carbon electrodes (SPCE) upon the addition of H2O2 in the presence of hydroquinone (HQ) as redox mediator, were used to monitor the extent of the different affinity reactions. The developed methodology, involving a simple and short pretreatment, allowed discrimination between no contaminated UHT and raw milk samples and samples containing antibiotic residues at the maximum residue limits (MRLs). The usefulness of the multiplexed magnetosensor was demonstrated by analyzing spiked milk samples in only 5 min. The results demonstrated that a clear discrimination of milk samples contaminated with antibiotics at their MRL level or their mixtures, allowing the identification of milk not complying with current legislation. These features make the developed methodology a promising alternative in the development of user-friendly devices for on-site analysis to ensure quality control for dairy products. Copyright © 2014 Elsevier B.V. All rights reserved.

  16. Disposable amperometric magneto-immunosensor for direct detection of tetracyclines antibiotics residues in milk.

    Science.gov (United States)

    Conzuelo, Felipe; Gamella, María; Campuzano, Susana; Reviejo, A Julio; Pingarrón, José M

    2012-08-06

    The preparation and performance of a disposable amperometric magneto-immunosensor, involving the use of a selective capture antibody immobilized on the surface of protein G-functionalized magnetic beads (ProtG-MBs) and screen-printed carbon electrodes (SPCEs), for the specific detection and quantification of tetracyclines (TCs) residues in milk is reported. A direct competitive immunoassay using a tracer with horseradish peroxidase (HRP) for the enzymatic labeling was performed. The amperometric response measured at -0.2 V vs. the silver pseudo-reference electrode of the SPCE upon the addition of H(2)O(2) in the presence of hydroquinone (HQ) as redox mediator was used as transduction signal. The developed methodology showed very low limits of detection (in the low ppb level) for 4 tetracycline antibiotics tested in untreated milk samples, and a good selectivity against other antibiotic residues frequently detected in milk and dairy products. The usefulness of the magneto-immunosensor was demonstrated by analyzing UHT whole milk samples spiked with 44 ng mL(-1) tetracycline (TC) as well as a reference milk containing a certified oxytetracycline (OTC) content. These features, together with the short analysis time (30 min), the simplicity, and easy automation and miniaturization of the required instrumentation make the developed methodology a promising alternative in the development of devices for on-site analysis. Copyright © 2012 Elsevier B.V. All rights reserved.

  17. Development of amperometric L-tyrosine sensor based on Fe-doped hydroxyapatite nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Kanchana, P.; Lavanya, N.; Sekar, C., E-mail: Sekar2025@gmail.com

    2014-02-01

    A novel biosensor based on Fe-doped hydroxyapatite (Fe-HA) nanoparticles and tyrosinase has been developed for the detection of L-tyrosine. Nanostructured Fe-HA was synthesized by a simple microwave irradiation method, and its phase formation, morphology and magnetic property were examined by powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). Electrochemical performance of the nano Fe-HA/tyrosinase modified glassy carbon electrode (GCE) for detection of L-tyrosine was investigated by cyclic voltammetry (CV) and amperometric methods. The fabricated biosensor exhibited a linear response to L-tyrosine over a wide concentration range of 1.0 × 10{sup −7} to 1.0 × 10{sup −5} M with a detection limit of 245 nM at pH 7.0. In addition, the fabricated sensor showed an excellent selectivity, good reproducibility, long-term stability and anti-interference towards the determination of L-tyrosine. - Highlights: • A novel amperometric L-tyrosine biosensor has been fabricated using nanostructured Fe-HA. • The fabricated sensor exhibits a wide linear range, good stability and high reproducibility. • Fe-HA assists microenvironment and direct electron transfer between enzyme and electrode surface. • The nano Fe-HA and electrode fabrication procedure are simple and less expensive.

  18. Fabrication of amperometric xanthine biosensors based on direct chemistry of xanthine oxidase

    Energy Technology Data Exchange (ETDEWEB)

    Gao Yansheng; Shen Chunping [Department of Chemistry, Soochow University, Suzhou, Jiangsu 215123 (China); Di Junwei, E-mail: djw@suda.edu.cn [Department of Chemistry, Soochow University, Suzhou, Jiangsu 215123 (China); Tu Yifeng [Department of Chemistry, Soochow University, Suzhou, Jiangsu 215123 (China)

    2009-08-31

    The construction of amperometric xanthine biosensor by immobilization of xanthine oxidase (XOD) on the multi-wall carbon nanotubes (CNTs) modified glassy carbon (GC) electrode surface was investigated. The direct chemistry of XOD was accomplished and the formal potential was about - 0.465 V (vs SCE). The heterogeneous electron transfer rate constant was evaluated to be 2.0 {+-} 0.3 s{sup -1}. The xanthine biosensor based on XOD entrapped in silica sol-gel (SG) thin film on CNTs-modified GC electrode surface was also investigated. The XOD still maintains its activity to xanthine. The amperometric response to xanthine showed a linear relation in the range from 0.2 {mu}M to 10 {mu}M and a detection limit of 0.1 {mu}M (S/N = 3). The enzyme electrode retained 95% of its initial activity after 90 days of storage. The sensor exhibited high sensitivity, rapid response and good long-term stability.

  19. Amperometric morphine sensing using a molecularly imprinted polymer-modified electrode

    International Nuclear Information System (INIS)

    Yeh, W.-M.; Ho, K.-C.

    2005-01-01

    This study incorporates morphine into a molecularly imprinted polymer (MIP) for the amperometric detection of morphine. The polymer, poly(3,4-ethylenedioxythiophene), PEDOT, is an electroactive film that catalyzes morphine oxidation and lowers the oxidization potential on an indium tin oxide (ITO) electrode. The MIP-PEDOT modified electrode is prepared by electropolymerizing PEDOT onto an ITO electrode in a 0.1 M LiClO 4 solution with template addition (morphine). After template molecule extraction, the oxidizing current of the MIP-PEDOT modified electrode is measured in a 0.1 M KCl solution (pH = 5.3) at 0.75 V (versus Ag/AgCl/sat'd KCl) with the morphine concentration varying in the 0.1-5 mM range. A linear range, displaying the relationship between steady-state currents and morphine concentrations, from 0.1 to 1 mM, is obtained. The proposed amperometric sensor could be used for morphine detection with a sensitivity of 91.86 μA/cm 2 per mM. A detection limit of 0.2 mM at a signal-to-noise ratio of 3 is achieved. Moreover, the proposed method can discriminate between morphine and its analogs, such as codeine

  20. Batch-injection analysis with amperometric detection of the DPPH radical for evaluation of antioxidant capacity.

    Science.gov (United States)

    Oliveira, Gracy K F; Tormin, Thiago F; Sousa, Raquel M F; de Oliveira, Alberto; de Morais, Sérgio A L; Richter, Eduardo M; Munoz, Rodrigo A A

    2016-02-01

    This work proposes the application of batch-injection analysis with amperometric detection to determine the antioxidant capacity of real samples based on the measurement of DPPH radical consumption. The efficient concentration or EC50 value corresponds to the concentration of sample or standard required to scavenge 50% DPPH radicals. For the accurate determination of EC50, samples were incubated with DPPH radical for 1h because many polyphenolic compounds typically found in plants and responsible for the antioxidant activity exhibit slow kinetics. The BIA system with amperometric detection using a glassy-carbon electrode presented high precision (RSD = 0.7%, n = 12), low detection limit (1 μmol L(-1)) and selective detection of DPPH (free of interferences from antioxidants). These contributed to low detection limits for the antioxidant (0.015 and 0.19 μmol L(-1) for gallic acid and butylated hydroxytoluene, respectively). Moreover, BIA methods show great promise for portable analysis because battery-powered instrumentation (electronic micropipette and potentiostats) is commercially available. Copyright © 2015 Elsevier Ltd. All rights reserved.

  1. N-m-nitrocinnamoylphenylhydroxyl-amine as reagent for amperometric determination of yttrium

    International Nuclear Information System (INIS)

    Oliferenko, G.L.; Gallaj, Z.A.; Sheina, N.M.; Shvedene, N.V.

    1983-01-01

    Possibility of using organic reagent of unsaturated N-arylsubstituted derivatives class of hydroxamic acids N-m-nitrocinnamoyl phenylhydroxylamire (NCPHA) for amperometric titration of yttrium using indication of e.t.p. by current of reagent oxidation on graphite electrode is investigated. Metal and the NCPHA form difficultly soluble complex with ratio of yttrium to the NCPHA, which is equal to 1:3. Buffer mixtures of 0.1MNH 3 +0.1MCH 3 COOH composis tion with pH 6.3-7.5 are optimal background solutions for amperometric titration of yttrium. The proposed method permits to determine 10-600 μkg of yttrium in the volume of 10 ml. Effect of the series of strange elements on titration of yttrium with NCPHA (Ca, Mg, Mn (2), Al, CU (2), Fe (3) REE and others) is studied. The developed method is used for yttrium determination in luminophores of Casub(n)-- Ysub(m)Fsub(z)xMn(2) (1-10%) composition

  2. Amperometric Enzyme-Based Biosensors for Application in Food and Beverage Industry

    Science.gov (United States)

    Csöoregi, Elisabeth; Gáspñr, Szilveszter; Niculescu, Mihaela; Mattiasson, Bo; Schuhmann, Wolfgang

    Continuous, sensitive, selective, and reliable monitoring of a large variety of different compounds in various food and beverage samples is of increasing importance to assure a high-quality and tracing of any possible source of contamination of food and beverages. Most of the presently used classical analytical methods are often requiring expensive instrumentation, long analysis times and well-trained staff. Amperometric enzyme-based biosensors on the other hand have emerged in the last decade from basic science to useful tools with very promising application possibilities in food and beverage industry. Amperometric biosensors are in general highly selective, sensitive, relatively cheap, and easy to integrate into continuous analysis systems. A successful application of such sensors for industrial purposes, however, requires a sensor design, which satisfies the specific needs of monitoring the targeted analyte in the particular application, Since each individual application needs different operational conditions and sensor characteristics, it is obvious that biosensors have to be tailored for the particular case. The characteristics of the biosensors are depending on the used biorecognition element (enzyme), nature of signal transducer (electrode material) and the communication between these two elements (electron-transfer pathway).

  3. Development of Amperometric Biosensors Based on Nanostructured Tyrosinase-Conducting Polymer Composite Electrodes

    Directory of Open Access Journals (Sweden)

    Francisco Javier del Campo

    2013-05-01

    Full Text Available Bio-composite coatings consisting of poly(3,4-ethylenedioxythiophene (PEDOT and tyrosinase (Ty were successfully electrodeposited on conventional size gold (Au disk electrodes and microelectrode arrays using sinusoidal voltages. Electrochemical polymerization of the corresponding monomer was carried out in the presence of various Ty amounts in aqueous buffered solutions. The bio-composite coatings prepared using sinusoidal voltages and potentiostatic electrodeposition methods were compared in terms of morphology, electrochemical properties, and biocatalytic activity towards various analytes. The amperometric biosensors were tested in dopamine (DA and catechol (CT electroanalysis in aqueous buffered solutions. The analytical performance of the developed biosensors was investigated in terms of linear response range, detection limit, sensitivity, and repeatability. A semi-quantitative multi-analyte procedure for simultaneous determination of DA and CT was developed. The amperometric biosensor prepared using sinusoidal voltages showed much better analytical performance. The Au disk biosensor obtained by 50 mV alternating voltage amplitude displayed a linear response for DA concentrations ranging from 10 to 300 μM, with a detection limit of 4.18 μM.

  4. Flow-injection spectrophotometric determination of captopril in pharmaceutical formulations using a new solid-phase reactor containing AgSCN immobilized in a polyurethane resin

    Directory of Open Access Journals (Sweden)

    Fernando Campanhã Vicentini

    2012-06-01

    Full Text Available A simple flow-injection analysis procedure was developed for determining captopril in pharmaceutical formulations employing a novel solid-phase reactor containing silver thiocyanate immobilized in a castor oil derivative polyurethane resin. The method was based on silver mercaptide formation between the captopril and Ag(I in the solid-phase reactor. During such a reaction, the SCN- anion was released and reacted with Fe3+, which generated the FeSCN2+ complex that was continuously monitored at 480 nm. The analytical curve was linear in the captopril concentration range from 3.0 × 10-4 mol L-1 to 1.1 × 10-3 mol L-1 with a detection limit of 8.0 × 10-5 mol L-1. Recoveries between 97.5% and 103% and a relative standard deviation of 2% for a solution containing 6.0 × 10-4 mol L-1 captopril (n = 12 were obtained. The sample throughput was 40 h-1 and the results obtained for captopril in pharmaceutical formulations using this procedure and those obtained using a pharmacopoeia procedure were in agreement at a 95% confidence level.Um procedimento simples de análise por injeção em fluxo foi desenvolvido para a determinação de captopril em formulações farmacêuticas empregando um novo reator em fase sólida contendo tiocianato de prata imobilizado em resina poliuretana obtida a partir de óleo de mamona. O método foi baseado na formação de um mercapto composto de prata, no reator em fase sólida, obtido entre o captopril e Ag (I imobilizada. Durante a reação, íons SCN- eram liberados e reagiam com Fe3+, gerando o complexo FeSCN2+, que foi continuamente monitorado em 480 nm. A curva analítica foi linear no intervalo de concentração de captopril entre 3,0 × 10-4 a 1,1 × 10-3 mol L-1 com um limite de detecção de 8,0 × 10-5 mol L-1. Recuperações entre 97,5-103% e desvio padrão relativo de 2% para uma solução contendo 6,0 × 10-4 mol L-1 de captopril (n = 12 foram obtidos. A frequência de amostragem foi de 40 h-1 e os resultados

  5. Determinação turbidimétrica em fluxo de cloridrato de fluoxetina em formulações farmacêuticas Flow-injection turbidimetric determination of fluoxetine hydrochloride in pharmaceutical formulations

    Directory of Open Access Journals (Sweden)

    Willian Toito Suarez

    2009-01-01

    Full Text Available A simple, accurate and precise flow-injection turbidimetric procedure for the determination of fluoxetine hydrochloride in pharmaceutical formulations is reported. The procedure is based on the precipitation of chloride of fluoxetine hydrochloride with silver nitrate solution and the yielded insoluble AgCl(s was monitored at 420 nm. The analytical curve was linear in the fluoxetine hydrochloride concentration range 3.0 x 10-5 - 5.0 x 10-4 mol L-1 with a detection limit of 10 µmol L-1 and, a sample throughout of 60 h-1.

  6. Determination of Ultra-Trace Amounts of Selenium(IV) by Flow Injection Hydride Generation Atomic Absorption Spectrometry with On-line Preconcentration by Co-precipitation with Lanthanium Hydroxide. Part II. On-line Addition of Coprecipating Agent

    DEFF Research Database (Denmark)

    Nielsen, Steffen; Sloth, Jens Jørgen; Hansen, Elo Harald

    1996-01-01

    A flow injection procedure for the determination of ultra-trace amounts of selenium(IV) is described, which combines hydride generation atomic absorption spectrometry (HGAAS) with on-line preconcentration of the analyte by co-precipitation-dissolution in a filterless knotted Microline reactor...... with hydrochloric acid, allowing an ensuing determination via hydride generation. At different sample flow rates, i.e., 4.8, 6.4 and 8.8 ml/min, enrichment factors of 30, 40 and 46, respectively, were obtained at a sampling frequency of 33 samples/h. The detection limit (3s) was 0.005 µg/l at a sample flow rate...

  7. Investigation of amperometric detection of phosphate Application in seawater and cyanobacterial biofilm samples.

    Science.gov (United States)

    Quintana, Josefina Calvo; Idrissi, Laila; Palleschi, Giuseppe; Albertano, Patrizia; Amine, Aziz; El Rhazi, Mama; Moscone, Danila

    2004-06-17

    Detection of phosphate using amperometry was investigated. The phosphomolybdate complex, formed by addition of nitric acid, ammonium molybdate and phosphate, was reduced at a carbon paste electrode polarised at +0.3V (versus Ag/AgCl). The major characteristics observed were simplicity of the equipment, a limited consumption of reagents and a low detection limit (0.3mumoll(-1)), with a linear range between 1 and 20mumoll(-1). The interference of silicate was completely eliminated using an appropriate concentration of nitric acid and ammonium molybdate. The amperometric detection of orthophosphate in seawater using the batch injection analysis (BIA) technique was reported. Moreover, a carbon paste microelectrode was constructed. Its use allows the analysis of small volume of samples with little dilution in supporting electrolyte. This method was applied to the determination of orthophosphate in cyanobacterial biofilms collected from Roman catacombs. There was a good statistical correlation between results obtained with the proposed method and the standard spectrophotometric method.

  8. Amperometric Determination of Bismuth Using Gallacetophenone Phenylhydrazone with the Structural Elucidation of Complex

    Directory of Open Access Journals (Sweden)

    D. Venkataramana Reddy

    2010-01-01

    Full Text Available Gallacetophenone phenylhydrazone (GPPH has been used as an analytical reagent for amperometric determination of bismuth. Bismuth is quantitatively determined by GPPH at pH 3.0-6.0. After studying the polarographic behaviour of GPPH and bismuth(III at dropping mercury electrode (DME, applied potential was fixed at -0.4v vs. saturated calomel electrode (SCE. The method was applied for the determination of bismuth in wood’s alloy. The composition of the complex corresponds to the formula Bi(C14 H14 O3 N22. The structure of the complex was arrived from the micro analytical data of the solid complex, thermogravimetric and differential thermal analysis curves and also from the infrared spectra of the complex.

  9. Determination of uranium and plutonium in plutonium based fuels by sequential amperometric titration

    International Nuclear Information System (INIS)

    Nair, P.R.; Lohithakshan, K.V.; Xavier, M.; Marathe, S.G.; Jain, H.C.

    1988-01-01

    A method is described for the sequential determination of uranium and plutonium in plutonium bearing fuel materials. Uranium and plutonium are reduced to U(IV) and Pu(III) with titanous chloride and then titrated with dichromate to two end points which are detected amperometrically using two polarized platinum electrodes. Uranium-plutonium solutions of known concentrations containing plutonium in the proportions of 4, 30, 50, and 70% were analyzed with precisions better than 0.3%, maintaining the amounts of plutonium per aliquot in the range of 2-10 mg. No significant bias could be detected. Several samples of (U,Pu)O 2 and (U,Pu)C were analyzed by this procedure. The effects of iron, fluoride, oxalic acid and mellitic acid on the method were also studied. (author) 5 refs.; 6 tabs

  10. Simultaneous topographic and amperometric membrane mapping using an AFM probe integrated biosensor.

    Science.gov (United States)

    Stanca, Sarmiza Elena; Csaki, Andrea; Urban, Matthias; Nietzsche, Sandor; Biskup, Christoph; Fritzsche, Wolfgang

    2011-02-15

    The investigation of the plasma membrane with intercorrelated multiparameter techniques is a prerequisite for understanding its function. Presented here, is a simultaneous electrochemical and topographic study of the cell membrane using a miniaturized amperometric enzymatic biosensor. The fabrication of this biosensor is also reported. The biosensor combines a scanning force microscopy (AFM) gold-coated cantilever and an enzymatic transducer layer of peroxidases (PODs). When these enzymes are brought in contact with the substrate, the specific redox reaction produces an electric current. The intensity of this current is detected simultaneously with the surface imaging. For sensor characterization, hydroquinone-2-carboxylic acid (HQ) is selected as an intrinsic source of H(2)O(2). HQ has been electrochemically regenerated by the reduction of antraquinone-2-carboxylic acid (AQ). The biosensor reaches the steady state value of the current intensity in 1 ± 0.2s. Copyright © 2010 Elsevier B.V. All rights reserved.

  11. Determination of carbohydrates by high performance anion chromatography-pulsed amperometric detection in mushrooms.

    Science.gov (United States)

    Zhou, Shuai; Tang, Qingjiu; Luo, Xi; Xue, Jun-Jie; Liu, Yanfang; Yang, Yan; Zhang, Jingsong; Feng, Na

    2012-01-01

    A method of detecting carbohydrates (fucose, trehalose, mannitol, arabitol, mannose, glucose, galactose, fructose, and ribose) by high-performance anion chromatography-pulsed amperometric detection (HAPEC-PAD) was established. The conditions are: CarboPac MA1 column, NaOH as the eluent, temperature 30°C, Au working electrode, Ag/AgCl reference electrode, and flow rate 0.4 mL/min. These nine analytes, which yielded high resolution by this method, could be detected in 40 minutes. Mushrooms were tested and good precision, stability, and reproducibility were achieved. This method is suitable for mushroom samples and could support research and development on sugar and sugar alcohol, which contains special effects.

  12. Determination of carbohydrates using pulsed amperometric detection combined with anion exchange separations

    Energy Technology Data Exchange (ETDEWEB)

    Edwards, W.T.; Pohl, C.A.; Rubin, R.

    1987-06-01

    Carbohydrates, including the monosaccharides commonly found in wood and wood pulp hydrolyzates, are separated by anion exchange chromatography using hydroxide and acetate eluants and are determined using pulsed amperometric detection. The detection method is based on oxidizing the sugars in a flow-through electrochemical cell equipped with a gold working electrode. A repeating cycle of three potentials is used: the first to oxidize the carbohydrates and measure the current generated, and two subsequent pulses to clean the electrode surface of oxidation products. The method is fast, sensitive, and requires no pre-column derivatization. It is applied to a sample of hydrolyzed wood pulp, which can be analyzed after minimal sample preparation. Detection limits are of the order of 1 mg/kg for monosaccharides in a 50 micro L injection. (Refs. 8).

  13. Prussian blue-modified nanoporous gold film electrode for amperometric determination of hydrogen peroxide.

    Science.gov (United States)

    Ghaderi, Seyran; Mehrgardi, Masoud Ayatollahi

    2014-08-01

    In this manuscript, the electrocatalytic reduction of hydrogen peroxides on Prussian blue (PB) modified nanoporous gold film (NPGF) electrode is described. The PB/NPGF is prepared by simple anodizing of a smooth gold film followed by PB film electrodeposition method. The morphology of the PB/NPGF electrode is characterized using scanning electron microscopy (SEM). The effect of solution pH and the scan rates on the voltammetric responses of hydrogen peroxide have also been examined. The amperometric determination of H2O2 shows two linear dynamic responses over the concentration range of 1μM-10μM and 10μM-100μM with a detection limit of 3.6×10(-7)M. Furthermore, this electrode demonstrated good stability, repeatability and selectivity remarkably. Copyright © 2014 Elsevier B.V. All rights reserved.

  14. Dual enzymatic biosensor for simultaneous amperometric determination of histamine and putrescine.

    Science.gov (United States)

    Henao-Escobar, W; Del Torno-de Román, L; Domínguez-Renedo, O; Alonso-Lomillo, M A; Arcos-Martínez, M J

    2016-01-01

    A disposable electrodic system consisting of two working electrodes connected in array mode has been developed for the simultaneous determination of histamine (His) and putrescine (Put). Histamine deshydrogenase and putrescine oxidase enzymes were respectively immobilized by crosslinking on each working screen-printed electrode, both modified with tetrathiafulvalene. The dual system allowed the simultaneous amperometric determination of both species by measuring the oxidation current of the mediator in each working electrode. The effect of other potentially interfering biogenic amines was also evaluated. The capability of detection was of 8.1 ± 0.7 for His and 10 ± 0.6 μM for Put. The precision in terms of relative standard deviation was of 3.5% and 6.7% for His and Put, respectively. The developed biosensor was successfully applied to the determination of His and Put in different food samples. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. Amperometric Morphine Detection Using Pt-Co Alloy Nanowire Array-modified Electrode

    International Nuclear Information System (INIS)

    Tao, Manlan; Xu, Feng; Li, Yueting; Xu, Quanqing; Chang, Yanbing; Yang, Yunhui; Wu, Zaisheng

    2010-01-01

    Pt-Co alloy nanowire array was directly synthesized by electrochemical deposition with polycarbonate template at -1.0V and subsequent chemical etching of the template. The use of Pt-Co alloy nanowire array-modified electrode (Pt- Co NAE) for the determination of morphine (MO) is described. The morphology of the Pt-Co alloy nanowire array has been investigated by scanning electron microscopy (SEM) and energy disperse X-ray spectroscopy (EDS) analysis), respectively. The resulting Pt-Co NAE offered a linear amperometric response for morphine ranging from 2.35 x 10 -5 to 2.39 x 10 -3 M with a detection limit of 7.83 x 10 -6 M at optimum conditions. This sensor displayed high sensitivity and long-term stability

  16. An Amperometric Biosensor for Uric Acid Determination Prepared From Uricase Immobilized in Polyaniline-Polypyrrole Film

    Directory of Open Access Journals (Sweden)

    Fatma Arslan

    2008-09-01

    Full Text Available A new amperometric uric acid biosensor was developed by immobilizing uricase by a glutaraldehyde crosslinking procedure on polyaniline-polypyrrole (pani-ppy composite film on the surface of a platinum electrode. Determination of uric acid was performed by the oxidation of enzymatically generated H2O2 at 0.4 V vs. Ag/AgCl. The linear working range of the biosensor was 2.5×10-6 – 8.5×10-5 M and the response time was about 70 s. The effects of pH, temperature were investigated and optimum parameters were found to be 9.0, 55 oC, respectively. The stability and reproducibility of the enzyme electrode have been also studied.

  17. Rapid amperometric detection of coliforms based on MWNTs/Nafion composite film modified glass carbon electrode.

    Science.gov (United States)

    Cheng, Yuxiao; Liu, Yajun; Huang, Jingjing; Xian, Yuezhong; Zhang, Wen; Zhang, Zhonghai; Jin, Litong

    2008-03-15

    A multi-wall carbon nanotubes (MWNTs)/Nafion modified glassy carbon electrode (GCE) was fabricated for the rapid amperometric detection of coliforms, represented by Escherichia coli (E. coli). In the bacterial solution, beta-galactosidase which was used as an indicator of coliforms reacted with substrate, p-aminophenol-beta-galactopyranoside (PAPG), and produced p-aminophenol (PAP). PAP was detected by MWNTs/Nafion modified GCE. Due to the cation-exchange capacity of Nafion and the electrocatalytic ability of MWNTs, the detection sensitivity of PAP was improved and the detection time of coliforms was shortened. The bacterial can be detected within 5h ranging from 10 to 10(4)cfu/mL. The MWNTs/Nafion modified GCE was easy to be constructed and regenerated. To our best knowledge, it was the first time to use MWNTs/Nafion modified GCE to detect the concentration of coliforms.

  18. An amperometric enzyme biosensor for real-time measurements of cellobiohydrolase activity on insoluble cellulose

    DEFF Research Database (Denmark)

    Cruys-Bagger, Nicolaj; Guilin, Ren; Tatsumi, Hirosuke

    2012-01-01

    An amperometric enzyme biosensor for continuous detection of cellobiose has been implemented as an enzyme assay for cellulases. We show that the initial kinetics for cellobiohydrolase I, Cel7A from Trichoderma reesei, acting on different types of cellulose substrates, semi-crystalline and amorphous......) and this provided experimental access to the transient kinetics of cellobiohydrolases acting on insoluble cellulose. The response from the CDH-biosensor during enzymatic hydrolysis was corrected for the specificity of PcCDH for the β-anomer of cello-oligosaccharides and the approach were validated against HPLC....... It is suggested that quantitative, real-time data on pure insoluble cellulose substrates will be useful in attempts to probe the molecular mechanism underlying enzymatic hydrolysis of cellulose...

  19. Amperometric estimation of La3+ and Ce3+ with cupferron using d.m.e

    International Nuclear Information System (INIS)

    Pitre, K.S.; Lavale, S.C.

    1982-01-01

    Cupferron has been employed as a reagent for the amperometric titrations of La 3+ and Ce 3+ in very dilute solution using d.m.e. Hydrochloric acid (pH=2.75) has been used as supporting electrolyte. These titrations revealed cupferron to metal ratio of 1:1. Titrations are not hampered by the presence of a fairly large amount of Li + , Na + , K + , Mg 3+ , Zn 3+ , Al 3+ , Cl - , Br - , I - , NO 3 - , NO 2 - , CH 2 COO - and ClO 4 - ions. Furthermore, micro and ultramicro quantities of La 3+ and Ce 2+ have been successfully determined with an error of less than +- 0.70%. (author)

  20. Real-Time Telemetry System for Amperometric and Potentiometric Electrochemical Sensors

    Directory of Open Access Journals (Sweden)

    Ching-Hsing Luo

    2011-09-01

    Full Text Available A real-time telemetry system, which consists of readout circuits, an analog-to-digital converter (ADC, a microcontroller unit (MCU, a graphical user interface (GUI, and a radio frequency (RF transceiver, is proposed for amperometric and potentiometric electrochemical sensors. By integrating the proposed system with the electrochemical sensors, analyte detection can be conveniently performed. The data is displayed in real-time on a GUI and optionally uploaded to a database via the Internet, allowing it to be accessed remotely. An MCU was implemented using a field programmable gate array (FPGA to filter noise, transmit data, and provide control over peripheral devices to reduce power consumption, which in sleep mode is 70 mW lower than in operating mode. The readout circuits, which were implemented in the TSMC 0.18-μm CMOS process, include a potentiostat and an instrumentation amplifier (IA. The measurement results show that the proposed potentiostat has a detectable current range of 1 nA to 100 μA, and linearity with an R2 value of 0.99998 in each measured current range. The proposed IA has a common-mode rejection ratio (CMRR greater than 90 dB. The proposed system was integrated with a potentiometric pH sensor and an amperometric nitrite sensor for in vitro experiments. The proposed system has high linearity (an R2 value greater than 0.99 was obtained in each experiment, a small size of 5.6 cm × 8.7 cm, high portability, and high integration.

  1. An amperometric cholesterol biosensor based on epoxy resin membrane bound cholesterol oxidase.

    Science.gov (United States)

    Pundir, C S; Narang, Jagriti; Chauhan, Nidhi; Sharma, Preety; Sharma, Renu

    2012-10-01

    The use of epoxy resin membrane as a support for immobilization of enzyme has resulted into improved sensitivity and stability of biosensors for uric acid, ascorbic acid and polyphenols. The present work was aimed to prepare an improved amperometric biosensor for determination of serum cholesterol required in the diagnostics and management of certain pathological conditions. Epoxy resin membrane with immobilized cholesterol oxidase was mounted on the cleaned platinum (Pt) electrode with a parafilm to construct a working electrode. This working electrode along with Ag/AgCl as reference and Ag wire as an auxiliary electrode were connected through a three terminal electrometer to construct a cholesterol biosensor. The sensor showed optimum response within 25 sec at pH 7.0 and 45°C. The linear working range of biosensor was 1.0 to 8.0 mM cholesterol. K m and I max for cholesterol were 5.0 mM and 9.09 μA, respectively. The biosensor measured serum cholesterol. The minimum detection limit of the sensor was 1.0 mM. The mean analytical recoveries of added cholesterol in serum (2.84 and 4.13 mM) were 91.4 ± 2.8 and 92.3 ± 3.1 per cent (n=6), respectively. Within and between assay coefficient of variation (CV) were epoxy resin membrane as a support for immobilization of cholesterol oxidase has resulted into an improved amperometric cholesterol biosensor. The present biosensor had an advantage over the existing biosensors as it worked at comparatively lower potential.

  2. Amperometric nitrate biosensor based on Carbon nanotube/Polypyrrole/Nitrate reductase biofilm electrode

    Energy Technology Data Exchange (ETDEWEB)

    Can, Faruk; Korkut Ozoner, Seyda; Ergenekon, Pinar; Erhan, Elif, E-mail: e.erhan@gyte.edu.tr

    2012-01-01

    This study describes the construction and characterization of an amperometric nitrate biosensor based on the Polypyrrole (PPy)/Carbon nanotubes (CNTs) film. Nitrate reductase (NR) was both entrapped into the growing PPy film and chemically immobilized via the carboxyl groups of CNTs to the CNT/PPy film electrode. The optimum amperometric response for nitrate was obtained in 0.1 M phosphate buffer solution (PBS), pH 7.5 including 0.1 M lithium chloride and 7 mM potassium ferricyanide with an applied potential of 0.13 V (vs. Ag/AgCl, 3 M NaCl). Sensitivity was found to be 300 nA/mM in a linear range of 0.44-1.45 mM with a regression coefficient of 0.97. The biosensor response showed a higher linear range in comparison to standard nitrate analysis methods which were tested in this study and NADH based nitrate biosensors. A minimum detectable concentration of 0.17 mM (S/N = 3) with a relative standard deviation (RSD) of 5.4% (n = 7) was obtained for the biosensor. Phenol and glucose inhibit the electrochemical reaction strictly at a concentration of 1 {mu}g/L and 20 mg/L, respectively. The biosensor response retained 70% of its initial response over 10 day usage period when used everyday. - Highlights: Black-Right-Pointing-Pointer K{sub 3}Fe(CN){sub 6} has been used for the first time as mediator for nitrate reductase. Black-Right-Pointing-Pointer Better performance was obtained in comparison to other nitrate biosensor studies operated with various mediators. Black-Right-Pointing-Pointer Analytical parameters were better than standard nitrate analysis methods.

  3. Amperometric nitrate biosensor based on Carbon nanotube/Polypyrrole/Nitrate reductase biofilm electrode

    International Nuclear Information System (INIS)

    Can, Faruk; Korkut Ozoner, Seyda; Ergenekon, Pinar; Erhan, Elif

    2012-01-01

    This study describes the construction and characterization of an amperometric nitrate biosensor based on the Polypyrrole (PPy)/Carbon nanotubes (CNTs) film. Nitrate reductase (NR) was both entrapped into the growing PPy film and chemically immobilized via the carboxyl groups of CNTs to the CNT/PPy film electrode. The optimum amperometric response for nitrate was obtained in 0.1 M phosphate buffer solution (PBS), pH 7.5 including 0.1 M lithium chloride and 7 mM potassium ferricyanide with an applied potential of 0.13 V (vs. Ag/AgCl, 3 M NaCl). Sensitivity was found to be 300 nA/mM in a linear range of 0.44–1.45 mM with a regression coefficient of 0.97. The biosensor response showed a higher linear range in comparison to standard nitrate analysis methods which were tested in this study and NADH based nitrate biosensors. A minimum detectable concentration of 0.17 mM (S/N = 3) with a relative standard deviation (RSD) of 5.4% (n = 7) was obtained for the biosensor. Phenol and glucose inhibit the electrochemical reaction strictly at a concentration of 1 μg/L and 20 mg/L, respectively. The biosensor response retained 70% of its initial response over 10 day usage period when used everyday. - Highlights: ► K 3 Fe(CN) 6 has been used for the first time as mediator for nitrate reductase. ► Better performance was obtained in comparison to other nitrate biosensor studies operated with various mediators. ► Analytical parameters were better than standard nitrate analysis methods.

  4. Real-Time Telemetry System for Amperometric and Potentiometric Electrochemical Sensors

    Science.gov (United States)

    Wang, Wei-Song; Huang, Hong-Yi; Chen, Shu-Chun; Ho, Kuo-Chuan; Lin, Chia-Yu; Chou, Tse-Chuan; Hu, Chih-Hsien; Wang, Wen-Fong; Wu, Cheng-Feng; Luo, Ching-Hsing

    2011-01-01

    A real-time telemetry system, which consists of readout circuits, an analog-to-digital converter (ADC), a microcontroller unit (MCU), a graphical user interface (GUI), and a radio frequency (RF) transceiver, is proposed for amperometric and potentiometric electrochemical sensors. By integrating the proposed system with the electrochemical sensors, analyte detection can be conveniently performed. The data is displayed in real-time on a GUI and optionally uploaded to a database via the Internet, allowing it to be accessed remotely. An MCU was implemented using a field programmable gate array (FPGA) to filter noise, transmit data, and provide control over peripheral devices to reduce power consumption, which in sleep mode is 70 mW lower than in operating mode. The readout circuits, which were implemented in the TSMC 0.18-μm CMOS process, include a potentiostat and an instrumentation amplifier (IA). The measurement results show that the proposed potentiostat has a detectable current range of 1 nA to 100 μA, and linearity with an R2 value of 0.99998 in each measured current range. The proposed IA has a common-mode rejection ratio (CMRR) greater than 90 dB. The proposed system was integrated with a potentiometric pH sensor and an amperometric nitrite sensor for in vitro experiments. The proposed system has high linearity (an R2 value greater than 0.99 was obtained in each experiment), a small size of 5.6 cm × 8.7 cm, high portability, and high integration. PMID:22164093

  5. Amperometric detection of carbohydrates based on the glassy carbon electrode modified with gold nano-flake layer

    OpenAIRE

    Huy Du Nguyen; T. Thuy Luyen Nguyen; Khac Manh Nguyen; Anh Mai Nguyen; Quoc Hien Nguyen

    2015-01-01

    An electro-deposition approach was established to incorporate the gold nano-flakes onto the glassy carbon electrode in electrochemical cells (nano-Au/GC/ECCs). Using pulsed amperometric detection (PAD) without any gold oxidation for cleaning (non-oxidative PAD), the nano-Au/GC/ECCs were able to maintain their activity for oxidizing of carbohydrates in a normal alkaline medium. The reproducibility of peak area was about 2 relative standard deviation (RSD,%) for 6 consecutive injections. A dyna...

  6. Modification of alumina matrices through chemical etching and electroless deposition of nano-Au array for amperometric sensing

    Directory of Open Access Journals (Sweden)

    Valinčius Gintaras

    2007-01-01

    Full Text Available AbstractSimple nanoporous alumina matrix modification procedure, in which the electrically highly insulating alumina barrier layer at the bottom of the pores is replaced with the conductive layer of the gold beds, was described. This modification makes possible the direct electron exchange between the underlying aluminum support and the redox species encapsulated in the alumina pores, thus, providing the generic platform for the nanoporous alumina sensors (biosensors with the direct amperometric signal readout fabrication.

  7. Amperometric Ion-Selective Electrode for Alkali Metal Cations Based on a Room-Temperature Ionic Liquid Membrane

    Czech Academy of Sciences Publication Activity Database

    Langmaier, Jan; Trojánek, Antonín; Samec, Zdeněk

    2009-01-01

    Roč. 21, 17-18 (2009), s. 1977-1983 ISSN 1040-0397 R&D Projects: GA MŠk ME08098; GA AV ČR IAA400400704 Institutional research plan: CEZ:AV0Z40400503 Keywords : room-temperature ionic liquid * alkali metals * Crown ether * cyclic voltammetry * amperometric ion-selective elkectrode Subject RIV: CG - Electrochemistry Impact factor: 2.630, year: 2009

  8. Determination of selected persistent organic pollutants in wastewater from landfill leachates, using an amperometric biosensor

    Science.gov (United States)

    Nomngongo, Philiswa N.; Catherine Ngila, J.; Msagati, Titus A. M.; Gumbi, Bhekumuzi P.; Iwuoha, Emmanuel I.

    Landfill leachates that contain persistent organic pollutants (POPs) are a big threat to groundwater systems and are projected to have hazardous effects in the long term if proper management strategies of the landfills are not put in place by those responsible. Monitoring the levels of POPs in landfill leachates is very crucial. This work presents an amperometric biosensor for determination of selected POPs in landfill leachates. The biosensor is based on kinetic inhibition of horseradish peroxidase (HRP). The enzyme was immobilised by electrostatic attachment on a polyaniline-modified Pt electrode surface. Selected POPs inhibited HRP enzyme activity and the decrease in the enzyme activity was used to determine these environmental pollutants. Selected polybrominated diphenyl ethers (PBDEs), polybrominated biphenyls (PBBs) and polychlorinated biphenyls (PCBs) were the analytes of choice because they are commonly found in South Africa water systems. Limits of detection for the amperometric biosensor were established as 0.014, 0.018, 0.022, 0.016 and 0.019 μg l-1 for BDE-100, PBB-1, PCB-1, PCB-28 and PCB-101, respectively. The HRP biosensor system gave different linear ranges for; BDE-100 (0.424-25.8 μg l-1), PBB-1 (0.862-13.4 μg l-1), PCB-1 (0.930-18.1 μg l-1), PCB-28 (0.730-15.7 μg l-1) and PCB-101 (0.930-27.1 μg l-1). Inhibition studies on HRP biosensor response toward the reduction of H2O2 in the absence and presence of the selected POPs were carried out to investigate the inhibition kinetics and its mechanism. The results obtained indicated that the inhibition mechanism was competitive for PBDEs and non-competitive for biphenyls (PCBs and PBBs). The application of the biosensor was tested on wastewater samples obtained from landfill leachate for determination of selected POPs. The leachate samples were found to contain PCB-28 (0.28 ± 0.03 μg l-1) and PCB-101 (0.31 ± 0.02 μg l-1). The samples were also analysed by GC-MS as a cross-check method and the

  9. Amperometric microsensor for direct probing of ascorbic acid in human gastric juice

    Energy Technology Data Exchange (ETDEWEB)

    Hutton, Emily A.; Pauliukaite, Rasa; Hocevar, Samo B. [Analytical Chemistry Laboratory, National Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana (Slovenia); Ogorevc, Bozidar, E-mail: bogorevc@ki.s [Analytical Chemistry Laboratory, National Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana (Slovenia); Smyth, Malcolm R. [National Centre for Sensor Research, School of Chemical Sciences, Dublin City University, Dublin 9 (Ireland)

    2010-09-30

    This article reports on a novel microsensor for amperometric measurement of ascorbic acid (AA) under acidic conditions (pH 2) based on a carbon fiber microelectrode (CFME) modified with nickel oxide and ruthenium hexacyanoferrate (NiO-RuHCF). This sensing layer was deposited electrochemically in a two-step procedure involving an initial galvanostatic NiO deposition followed by a potentiodynamic RuHCF deposition from solutions containing the precursor salts. Several important parameters were examined to characterize and optimize the NiO-RuHCF sensing layer with respect to its current response to AA by using cyclic voltammetry, and scanning electron microscopy-energy dispersive X-ray spectroscopy methods. With the NiO-RuHCF coated CFME, the AA oxidation potential under acidic conditions was shifted to a less positive value for about 0.2 V (E{sub p} of ca. 0.23 V vs. Ag/AgCl) as compared to a bare CFME, which greatly improves the electrochemical selectivity. Using the hydrodynamic amperometry mode, the current vs. AA concentration in 0.01 M HCl, at a selected operating potential of 0.30 V, was found to be linear over a wide range of 10-1610 {mu}M (n = 22, r = 0.999) with a calculated limit of detection of 1.0 {mu}M. The measurement repeatability was satisfactory with a relative standard deviation (r.s.d.) ranging from 4% to 5% (n = 6), depending on the AA concentration, and with a sensor-to-sensor reproducibility (r.s.d.) of 6.9% at 100 {mu}M AA. The long-term reproducibility, using the same microsensor for 112 consecutive measurements of 20 {mu}M AA over 11 h of periodic probing sets over 4 days, was 16.1% r.s.d., thus showing very good stability at low AA levels and suitability for use over a prolonged period of time. Moreover, using the proposed microsensor, additionally coated with a protective cellulose acetate membrane, the calibration plot obtained in the extremely complex matrix of real undiluted gastric juice was linear from 10 to 520 {mu}M (n = 14, r = 0

  10. Amperometric microsensor for direct probing of ascorbic acid in human gastric juice

    International Nuclear Information System (INIS)

    Hutton, Emily A.; Pauliukaite, Rasa; Hocevar, Samo B.; Ogorevc, Bozidar; Smyth, Malcolm R.

    2010-01-01

    This article reports on a novel microsensor for amperometric measurement of ascorbic acid (AA) under acidic conditions (pH 2) based on a carbon fiber microelectrode (CFME) modified with nickel oxide and ruthenium hexacyanoferrate (NiO-RuHCF). This sensing layer was deposited electrochemically in a two-step procedure involving an initial galvanostatic NiO deposition followed by a potentiodynamic RuHCF deposition from solutions containing the precursor salts. Several important parameters were examined to characterize and optimize the NiO-RuHCF sensing layer with respect to its current response to AA by using cyclic voltammetry, and scanning electron microscopy-energy dispersive X-ray spectroscopy methods. With the NiO-RuHCF coated CFME, the AA oxidation potential under acidic conditions was shifted to a less positive value for about 0.2 V (E p of ca. 0.23 V vs. Ag/AgCl) as compared to a bare CFME, which greatly improves the electrochemical selectivity. Using the hydrodynamic amperometry mode, the current vs. AA concentration in 0.01 M HCl, at a selected operating potential of 0.30 V, was found to be linear over a wide range of 10-1610 μM (n = 22, r = 0.999) with a calculated limit of detection of 1.0 μM. The measurement repeatability was satisfactory with a relative standard deviation (r.s.d.) ranging from 4% to 5% (n = 6), depending on the AA concentration, and with a sensor-to-sensor reproducibility (r.s.d.) of 6.9% at 100 μM AA. The long-term reproducibility, using the same microsensor for 112 consecutive measurements of 20 μM AA over 11 h of periodic probing sets over 4 days, was 16.1% r.s.d., thus showing very good stability at low AA levels and suitability for use over a prolonged period of time. Moreover, using the proposed microsensor, additionally coated with a protective cellulose acetate membrane, the calibration plot obtained in the extremely complex matrix of real undiluted gastric juice was linear from 10 to 520 μM (n = 14, r = 0.998). These

  11. A LabVIEW®-based software for the control of the AUTORAD platform. A fully automated multisequential flow injection analysis Lab-on-Valve (MSFIA-LOV) system for radiochemical analysis

    International Nuclear Information System (INIS)

    Barbesi, Donato; Vilas, Victor Vicente; Millet, Sylvain; Sandow, Miguel; Colle, Jean-Yves; Heras, Laura Aldave de las

    2017-01-01

    A LabVIEW®-based software for the control of the fully automated multi-sequential flow injection analysis Lab-on-Valve (MSFIA-LOV) platform AutoRAD performing radiochemical analysis is described. The analytical platform interfaces an Arduino®-based device triggering multiple detectors providing a flexible and fit for purpose choice of detection systems. The different analytical devices are interfaced to the PC running LabVIEW®VI software using USB and RS232 interfaces, both for sending commands and receiving confirmation or error responses. The AUTORAD platform has been successfully applied for the chemical separation and determination of Sr, an important fission product pertinent to nuclear waste. (author)

  12. Coupling on-line preconcentration by ion-exchange with ETAAS. A novel flow injection approach based on the use of a renewable microcolumn as demonstrated for the determination of nickel in environmental and biological samples

    DEFF Research Database (Denmark)

    Wang, Jianhua; Hansen, Elo Harald

    2000-01-01

    A novel way of exploiting flow injection/sequential injection (FIA/SIA) on-line ion-exchange preconcentration with detection by electrothermal atomic absorption spectrometry (ETAAS) is described and demonstrated for the determination of trace-levels of nickel. Based on the use of a renewable micr...... was validated by determination of the nickel contents in two certified reference materials and in a human urine sample. (C) 2000 Elsevier Science B.V. All rights reserved....... sample. An enrichment factor of 72.1, a detection limit of 9 ng l(-1), along with a sampling frequency of 12 h(-1) were obtained with 150 s of sample loading time at a sample flow rate of 12 mul s(-1) (corresponding to 0.72 ml min(-1)). The relative standard deviations were 3.4%. The procedure...

  13. A LabVIEW®-based software for the control of the AUTORAD platform: a fully automated multisequential flow injection analysis Lab-on-Valve (MSFIA-LOV) system for radiochemical analysis.

    Science.gov (United States)

    Barbesi, Donato; Vicente Vilas, Víctor; Millet, Sylvain; Sandow, Miguel; Colle, Jean-Yves; Aldave de Las Heras, Laura

    2017-01-01

    A LabVIEW ® -based software for the control of the fully automated multi-sequential flow injection analysis Lab-on-Valve (MSFIA-LOV) platform AutoRAD performing radiochemical analysis is described. The analytical platform interfaces an Arduino ® -based device triggering multiple detectors providing a flexible and fit for purpose choice of detection systems. The different analytical devices are interfaced to the PC running LabVIEW ® VI software using USB and RS232 interfaces, both for sending commands and receiving confirmation or error responses. The AUTORAD platform has been successfully applied for the chemical separation and determination of Sr, an important fission product pertinent to nuclear waste.

  14. Real-Time Amperometric Recording of Extracellular H2O2 in the Brain of Immunocompromised Mice: An In Vitro, Ex Vivo and In Vivo Characterisation Study

    Science.gov (United States)

    Reid, Caroline H.; Finnerty, Niall J.

    2017-01-01

    We detail an extensive characterisation study on a previously described dual amperometric H2O2 biosensor consisting of H2O2 detection (blank) and degradation (catalase) electrodes. In vitro investigations demonstrated excellent H2O2 sensitivity and selectivity against the interferent, ascorbic acid. Ex vivo studies were performed to mimic physiological conditions prior to in vivo deployment. Exposure to brain tissue homogenate identified reliable sensitivity and selectivity recordings up to seven days for both blank and catalase electrodes. Furthermore, there was no compromise in pre- and post-implanted catalase electrode sensitivity in ex vivo mouse brain. In vivo investigations performed in anaesthetised mice confirmed the ability of the H2O2 biosensor to detect increases in amperometric current following locally perfused/infused H2O2 and antioxidant inhibitors mercaptosuccinic acid and sodium azide. Subsequent recordings in freely moving mice identified negligible effects of control saline and sodium ascorbate interference injections on amperometric H2O2 current. Furthermore, the stability of the amperometric current was confirmed over a five-day period and analysis of 24-h signal recordings identified the absence of diurnal variations in amperometric current. Collectively, these findings confirm the biosensor current responds in vivo to increasing exogenous and endogenous H2O2 and tentatively supports measurement of H2O2 dynamics in freely moving NOD SCID mice. PMID:28698470

  15. Real-Time Amperometric Recording of Extracellular H₂O₂ in the Brain of Immunocompromised Mice: An In Vitro, Ex Vivo and In Vivo Characterisation Study.

    Science.gov (United States)

    Reid, Caroline H; Finnerty, Niall J

    2017-07-08

    We detail an extensive characterisation study on a previously described dual amperometric H₂O₂ biosensor consisting of H₂O₂ detection (blank) and degradation (catalase) electrodes. In vitro investigations demonstrated excellent H₂O₂ sensitivity and selectivity against the interferent, ascorbic acid. Ex vivo studies were performed to mimic physiological conditions prior to in vivo deployment. Exposure to brain tissue homogenate identified reliable sensitivity and selectivity recordings up to seven days for both blank and catalase electrodes. Furthermore, there was no compromise in pre- and post-implanted catalase electrode sensitivity in ex vivo mouse brain. In vivo investigations performed in anaesthetised mice confirmed the ability of the H₂O₂ biosensor to detect increases in amperometric current following locally perfused/infused H₂O₂ and antioxidant inhibitors mercaptosuccinic acid and sodium azide. Subsequent recordings in freely moving mice identified negligible effects of control saline and sodium ascorbate interference injections on amperometric H₂O₂ current. Furthermore, the stability of the amperometric current was confirmed over a five-day period and analysis of 24-h signal recordings identified the absence of diurnal variations in amperometric current. Collectively, these findings confirm the biosensor current responds in vivo to increasing exogenous and endogenous H₂O₂ and tentatively supports measurement of H₂O₂ dynamics in freely moving NOD SCID mice.

  16. Field preconcentration of cadmium from seawater by using a minicolumn packed with Amberlite XAD-4/4-(2-pyridylazo) resorcinol and its flow-injection-flame atomic absorption spectrometric determination at the ng L{sup -1} Level

    Energy Technology Data Exchange (ETDEWEB)

    Yebra, M.C.; Salgado, J.; Puig, L.; Moreno-Cid, A. [Department of Analytical Chemistry, Nutrition and Bromatology, Faculty of Chemistry, University of Santiago de Compostela, 15782-Santiago de Compostela (Spain)

    2002-10-01

    A flow injection analysis-flame atomic absorption spectrometric method for the determination of cadmium in seawater was developed with the aim of yielding a sensitive assay with a low detection limit. The method employs a field flow preconcentration technique involving a minicolumn containing Amberlite XAD-4 impregnated with the complexing agent 4-(2-pyridylazo) resorcinol. A Plackett-Burman 2{sup 7} x 3/32 design for seven factors (sample pH, sample flow rate, eluent volume, eluent concentration, eluent flow rate, ethanol percentage in the eluent and minicolumn diameter) was carried out in order to find the significant variables affecting the field continuous preconcentration system (FCPS) and the flow injection elution manifold for cadmium determination in seawater samples by flame atomic absorption spectrometry. Cadmium can be preconcentrated with an enrichment factor of 1053 for a sample volume of 200 mL and a preconcentration time of 57 min. In these experimental conditions, the method provides a linear relationship between absorbance and cadmium concentration in the range from 22-1900 ng L{sup -1}, with a detection limit (3SD) of 6 ng L{sup -1}. The precision (expressed as relative standard deviation) for eleven independent determinations reached values of 8.9-0.8% in cadmium solutions of 50-700 ng L{sup -1}. Analysis of certified reference materials (SLEW-3 and NASS-5) showed good agreement with the certified value. This procedure was applied to the determination of cadmium in seawater from Galicia (Spain). (orig.)

  17. Amperometric biosensor for the determination of phenols using a crude extract of sweet potato

    Energy Technology Data Exchange (ETDEWEB)

    Cruz Vieira, I. da; Fatibello-Filho, O. [Universidade Federal de Sa Carlos (Brazil)

    1997-03-01

    An amperometric biosensor for the determination of phenols is proposed using a crude extract of sweet potato (Ipomoea batatas (L.) Lam.) as an enzymatic source of polyphenol oxidase (PPO; tyrosinase; catechol oxidase; EC 1.14.18.1). The biosensor is constructed by the immobilization of sweet potato crude extract with glutaraldehyde and bovine serum albumin onto an oxygen membrane. This biosensor provides a linear response for catechol, pyrogallol, phenol and p-cresol in the concentration ranges of 2.0 x 10{sup -5} -4.3 x 10{sup -4} mol L{sup -1}, 2.0 x 10{sup -5} -4.3 x 10{sup -4} mol L{sup -1}, 2.0 x 10{sup -5} -4.5 x 10{sup -4} mol L{sup -1} and 2.0 x 10{sup -5} -4.5 x 10{sup -4} mol L{sup -1}, respectively. The response time was about 3-5 min for the useful response range, and the lifetime of this electrode was excellent for fifteen days (over 220 determinations for each enzymatic membrane). Application of this biosensor for the determination of phenols in industrial wastewaters is presented.

  18. Amperometric biosensor for hydrogen peroxide based on hemoglobin entrapped in titania sol-gel film

    International Nuclear Information System (INIS)

    Yu Jiuhong; Ju Huangxian

    2003-01-01

    Hemoglobin (Hb) was entrapped in a titania sol-gel matrix and used as a mimetic peroxidase to construct a novel amperometric biosensor for hydrogen peroxide. The Hb entrapped titania sol-gel film was obtained with a vapor deposition method, which simplified the traditional sol-gel process for protein immobilization. The morphologies of both titania sol-gel and the Hb films were characterized using scanning electron microscopy (SEM) and proved to be chemically clean, porous, homogeneous. This matrix provided a biocompatible microenvironment for retaining the native structure and activity of the entrapped Hb and a very low mass transport barrier to the substrates. H 2 O 2 could be reduced by the catalysis of the entrapped hemoglobin at -300 mV without any mediator. The reagentless H 2 O 2 sensor exhibited a fast response (less than 5 s) and sensitivity as high as 1.29 mA mM -1 cm -2 . The linear range for H 2 O 2 determination was from 5.0x10 -7 to 5.4x10 -5 M with a detection limit of 1.2x10 -7 M. The apparent Michaelis-Menten constant of the encapsulated hemoglobin was calculated to be 0.18±0.02 mM. The stability of the biosensor was also evaluated

  19. Electrophysiological and amperometric evidence that modafinil blocks the dopamine uptake transporter to induce behavioral activation.

    Science.gov (United States)

    Federici, M; Latagliata, E C; Rizzo, F R; Ledonne, A; Gu, H H; Romigi, A; Nisticò, R; Puglisi-Allegra, S; Mercuri, N B

    2013-11-12

    Although the wake-promoting drug modafinil has been shown to bind quite exclusively to the dopamine transporter (DAT), its action in the brain has been thought to be partially independent from the facilitation of the dopaminergic signals. Here we used electrophysiological and amperometric techniques to investigate the effects of modafinil on the dopaminergic neurons of the substantia nigra pars compacta (SNpc) and on the synaptic overflow of dopamine in the dorsal striatum from the sliced tissue of wild-type and cocaine-insensitive genetically modified mice (DAT-CI). Moreover, we examined the consequences of modafinil administration on the locomotor behavior of wild-type and DAT-CI mice. In in vitro experiments, modafinil inhibited the spontaneous firing discharge of the dopaminergic neurons. More consistently, it potentiated firing inhibition and the membrane responses caused by exogenously applied dopamine on these cells. Furthermore, it augmented the stimulus-evoked outflow of DA in the striatum. Noteworthy, modafinil caused locomotor activation in wild-type mice. On the other hand, neither the electrophysiological nor the behavioral effects of modafinil were detected in DAT-CI animals. These results demonstrate that modafinil potentiates brain dopaminergic signals via DAT inhibition by acting at the same binding site of cocaine. Therefore, this mechanism of action explains most of the pharmacological properties of this compound in the clinical setting. Copyright © 2013 IBRO. All rights reserved.

  20. Simultaneous Voltammetric/Amperometric Determination of Sulfide and Nitrite in Water at BDD Electrode

    Directory of Open Access Journals (Sweden)

    Anamaria Baciu

    2015-06-01

    Full Text Available This work reported new voltammetric/amperometric-based protocols using a commercial boron-doped diamond (BDD electrode for simple and fast simultaneous detection of sulfide and nitrite from water. Square-wave voltammetry operated under the optimized working conditions of 0.01 V step potential, 0.5 V modulation amplitude and 10 Hz frequency allowed achieving the best electroanalytical parameters for the simultaneous detection of nitrite and sulfide. For practical in-field detection applications, the multiple-pulsed amperometry technique was operated under optimized conditions, i.e., −0.5 V/SCE for a duration of 0.3 s as conditioning step, +0.85 V/SCE for a duration of 3 s that assure the sulfide oxidation and +1.25 V/SCE for a duration of 0.3 s, where the nitrite oxidation occurred, which allowed the simultaneously detection of sulfide and nitrite without interference between them. Good accuracy was found for this protocol in comparison with standardized methods for each anion. Also, no interference effect was found for the cation and anion species, which are common in the water matrix.

  1. Determination of plutonium and neptunium in various materials by coulometric titration with amperometric indicating

    International Nuclear Information System (INIS)

    Moiseev, I.V.; Kuperman, A.Ya.; Borodina, N.N.; Galkina, V.N.; Nikitskaya, V.N.

    1976-01-01

    Coulometric methods of determining Pu and Np in the products of complex composition containing, in addition to Pu and Np, Cr and Nn have been developed. The methods are based on titration of Pusup((6)) and Npsup((6)) to tetravalent state in H 2 SO 4 -H 3 PO 4 with iron (2) ions generated continuously. A new variant of amperometric method has been proposed for determining end-point of titration. The methods of preparing Pusup((6)) and Npsup((6)) solutions have been developed. It has been shown that, upon dissolution of PuO 2 and NpO 2 by boiling with a mixture of nitric and perchloric acids Pusup((4)) and Npsup((4)) are oxidized quantitatively to Pusup((6)) and Npsup((6)) while Cl 2 , Crsup((6)) and Mnsup((7,4,3)) in the solution obtained are selectively reduced by CHOOH and CH 2 (COOH) 2 . In 6-8 M in terms of H 2 SO 4 solution, ammonium bichromate oxidizes Npsup((4)) to Npsup((6)), Pusup((3)) to Pusup((4)), and Mnsup((2)) to Mnsup((3)). Oxidized Mn and excess of Crsup((6)) are selectively reduced by CHOOH and H 2 C 2 O 4 in 4M in terms of H 2 SO 4 solution

  2. Preparation of cholesterol oxidase nanoparticles and their application in amperometric determination of cholesterol

    International Nuclear Information System (INIS)

    Chawla, Sheetal; Rawal, Rachna; Sonia; Ramrati; Pundir, C. S.

    2013-01-01

    The nanoparticle (NP) aggregates of commercial cholesterol oxidase (ChOx) were prepared by desolvation method. The formation and characterization of ChOxNP aggregates were studied by transmission electron microscopy and scanning electron microscopy. NP aggregates were more stable, active and had a higher shelf life than that of free enzyme. An amperometric cholesterol biosensor was constructed by immobilizing ChOxNPs onto Au electrode. The biosensor showed optimum response within 8 s at pH 6.0 and 35 °C, when polarized at +0.27 V versus Ag/AgCl. The biosensor possesses high sensitivity and measures cholesterol concentrations as low as 1.56 mg/dl. The working linear range was 12.5–700 mg/dl for cholesterol. The biosensor was evaluated and employed for measurement of total cholesterol in human serum. The enzyme electrode lost 50 % of its initial activity during its regular use for 180 times over a period of 90 days when stored in 0.1 M sodium phosphate buffer, pH 7.0 at 4 °C

  3. Separation and determination of flavonoids in three traditional chinese medicines by capillary electrophoresis with amperometric detection.

    Science.gov (United States)

    Wang, Wei; Lin, Ping; Ma, Lihong; Xu, Kaixuan; Lin, Xiuli

    2016-04-01

    Flavonoids are important active ingredients in many traditional Chinese medicines. In this paper, capillary electrophoresis with amperometric detection was employed to separate and detect eight flavonoids, rutin, quercetrin, quercetin, kaempferol, kaempferide, catechin, apigenin, and luteolin, in a home-made capillary electrophoresis device. Under the separation voltage of 2000 V, the eight flavonoids could be completely separated within 33 min in 18 mM borax running buffer at pH 10.2. Good linear relationships were obtained for all analytes and the detection limits for flavonoids ranged from 0.46 to 0.85 μM. Then, the method was applied to separate and determine the flavonoids in three traditional Chinese medicines, hippophae rhamnoides, hypericum perforatum, and cacumen platycladi. Finally, rutin, kaempferol, quercetin, and quercetrin were discovered in these medicines and the concentrations ranged from 0.28 to 9.94 mg/g. The recoveries of flavonoids ranged from 84.7 to 113%, which showed the high reliability of this method. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. p-Benzoquinone-mediated amperometric biosensor developed with Psychrobacter sp. for toxicity testing of heavy metals.

    Science.gov (United States)

    Wang, Xuejiang; Liu, Mian; Wang, Xin; Wu, Zhen; Yang, Lianzhen; Xia, Siqing; Chen, Ling; Zhao, Jianfu

    2013-03-15

    A rapid and reliable p-benzoquinone-mediated amperometric biosensor (ToxTell) incorporated with Psychrobacter sp. to detect toxicities of heavy metal ions has been developed. This ToxTell biosensor relied on the real-time monitoring of inhibition effect for metabolism by toxicant to provide early detection and assessment of the degree of toxicity to living cells. The effect of growth phase on the sensitivity of Psychrobacter sp. biosensor was studied. The results showed that at the middle of the logarithmic phase or transition from logarithmic to stationary phase, the Psychrobacter sp. ToxTell biosensor had a higher sensitivity to toxicants. The effects of pH, salinity in respiratory substrates and incubation time on the performance of Psychrobacter sp. biosensor were also investigated. EC(50) values of Cu(2+), Cd(2+), Zn(2+), Cr(6+), Hg(2+) and Pb(2+) to Psychrobacter sp. determined at incubation time 30 min were 2.6 mg/L, 47.3 mg/L, 10.9 mg/L, 14.0 mg/L, 0.8 mg/L and 110.1 mg/L, respectively. The ToxTell microbial biosensor developed in this work demonstrated excellent storage stability for more than 60 days. The biosensor could incorporate different microbial species as biocomponent to reflect the comprehensive values for toxicants in real samples and the results therefore had high degree of validity. Copyright © 2012 Elsevier B.V. All rights reserved.

  5. Characterisation of brewpub beer carbohydrates using high performance anion exchange chromatography coupled with pulsed amperometric detection.

    Science.gov (United States)

    Arfelli, Giuseppe; Sartini, Elisa

    2014-01-01

    High performance anion exchange chromatography (HPAEC) coupled with pulsed amperometric detection (PAD) was optimised in order to quantify mannose, maltose, maltotriose, maltotetraose, maltopentaose, maltohexaose and maltoheptaose content of beer. The method allows the determination of above mentioned oligosaccharides, in a single chromatographic run, without any pre-treatment. Limit of detection and limit of quantification were suitable for beer. Accuracy and repeatability were good for the entire amount considered. Once optimised HPAEC PAD for the specific matrix, the second goal of this research was to verify the possibility to discriminate beers, depending on their style. The carbohydrates content of brewpub commercial beers was very variable, ranging from 19.3 to 1469mg/L (mannose), 34.5 to 2882mg/L (maltose), 141.9 to 20731mg/L (maltotriose), 168.5 to 7650mg/L (maltotetraose), 20.1 to 2537mg/L (maltopentaose), 22.9 to 3295mg/L (maltohexaose), 8.5 to 2492mg/L (maltoeptaose), even in the same style of beer. However, the carbohydrates content was useful, jointed with other compounds amount, to discriminate different styles of beer. As a matter of fact, principal component analysis put in evidence beer differences considering some fermentation conditions and colour. Copyright © 2013 Elsevier Ltd. All rights reserved.

  6. A Differential Electrochemical Readout ASIC With Heterogeneous Integration of Bio-Nano Sensors for Amperometric Sensing.

    Science.gov (United States)

    Ghoreishizadeh, Sara S; Taurino, Irene; De Micheli, Giovanni; Carrara, Sandro; Georgiou, Pantelis

    2017-10-01

    A monolithic biosensing platform is presented for miniaturized amperometric electrochemical sensing in CMOS. The system consists of a fully integrated current readout circuit for differential current measurement as well as on-die sensors developed by growing platinum nanostructures (Pt-nanoS) on top of electrodes implemented with the top metal layer. The circuit is based on the switch-capacitor technique and includes pseudodifferential integrators for concurrent sampling of the differential sensor currents. The circuit further includes a differential to single converter and a programmable gain amplifier prior to an ADC. The system is fabricated in [Formula: see text] technology and measures current within [Formula: see text] with minimum input-referred noise of [Formula: see text] and consumes [Formula: see text] from a [Formula: see text] supply. Differential sensing for nanostructured sensors is proposed to build highly sensitive and offset-free sensors for metabolite detection. This is successfully tested for bio-nano-sensors for the measurement of glucose in submilli molar concentrations with the proposed readout IC. The on-die electrodes are nanostructured and cyclic voltammetry run successfully through the readout IC to demonstrate detection of [Formula: see text].

  7. An amperometric biosensor for fish freshness detection from xanthine oxidase immobilized in polypyrrole-polyvinylsulphonate film.

    Science.gov (United States)

    Dolmaci, Nezaket; Çete, Servet; Arslan, Fatma; Yaşar, Ahmet

    2012-08-01

    A new amperometric biosensor was developed for determining hypoxanthine in fish meat. Xanthine oxidase with pyrrole and polyvinylsulphonate was immobilized on the surface of a platinum electrode by electropolymerization. The determination of xanthine-hypoxanthine was performed by means of oxidation of uric acid liberated during the enzyme reaction on the surface of the enzyme electrode at + 0.30V (SCE). The effects of pH, substrate concentration, and temperature on the response of the xanthine-hypoxanthine biosensor were investigated. The linear working range of the enzyme electrode was 1.0 × 10(-7) -1.0 × 10(-3) M of the hypoxanthine concentration, and the detection limit was 1.0 × 10(-7)M. The apparent K(m(app)) and I(max) of the immobilized xanthine oxidase were found to be 0.0154 mM and 1.203 μA/mM, respectively. The best pH and temperature value for xanthine oxidase were selected as 7.75 and 25°C, respectively. The sensor was used for the determination of hypoxhantine in fish meat. Results show that the fish degraded very rapidly after seven days and the hypoxanthine amount was found to increase over days of storage.

  8. Amperometric Determination of Sulfite by Gas Diffusion- Sequential Injection with Boron-Doped Diamond Electrode

    Directory of Open Access Journals (Sweden)

    Orawon Chailapakul

    2008-03-01

    Full Text Available A gas diffusion sequential injection system with amperometric detection using aboron-doped diamond electrode was developed for the determination of sulfite. A gasdiffusion unit (GDU was used to prevent interference from sample matrices for theelectrochemical measurement. The sample was mixed with an acid solution to generategaseous sulfur dioxide prior to its passage through the donor channel of the GDU. Thesulfur dioxide diffused through the PTFE hydrophobic membrane into a carrier solution of 0.1 M phosphate buffer (pH 8/0.1% sodium dodecyl sulfate in the acceptor channel of theGDU and turned to sulfite. Then the sulfite was carried to the electrochemical flow cell anddetected directly by amperometry using the boron-doped diamond electrode at 0.95 V(versus Ag/AgCl. Sodium dodecyl sulfate was added to the carrier solution to preventelectrode fouling. This method was applicable in the concentration range of 0.2-20 mgSO32−/L and a detection limit (S/N = 3 of 0.05 mg SO32−/L was achieved. This method wassuccessfully applied to the determination of sulfite in wines and the analytical resultsagreed well with those obtained by iodimetric titration. The relative standard deviations forthe analysis of sulfite in wines were in the range of 1.0-4.1 %. The sampling frequency was65 h−1.

  9. AMPEROMETRIC DETERMINATION OF 8-CHLOROTHEOPHYLLINE, CAFFEINE, AND DIPHENHYDRAMINE IN A SINGLE RUN

    Directory of Open Access Journals (Sweden)

    Jhonys Machado Freitas

    Full Text Available A simple method for simultaneous determination of 8-chlorotheophylline (CTP, caffeine (CAF, and diphenhydramine (DIP using batch-injection analysis with multiple pulse amperometric detection (BIA-MPA is reported. A sequence of three potential pulses (+1.10 V, +1.40 V, and +1.70 V was applied to the boron-doped diamond working electrode with the acquisition of three distinct amperograms. CTP was detected selectively at +1.10 V, both CTP + CAF at +1.40 V and CTP + CAF + DIP at +1.70 V. The subtraction between the currents detected at the three potential pulses (with the use of correction factors was the strategy used to achieve selectivity for the determination of CAF and DIP. The proposed method is simple, inexpensive, fast (120 injections h-1, presents good precision (RSD < 0.9%; n = 20, and adequate limits of detection (0.31, 0.49, and 0.76 µmol L-1 for CTP, CAF and DIP, respectively. The results obtained by BIA-MPA were similar to those found by high-performance liquid chromatography (95% confidence level.

  10. Amperometric Immunosensor Based on a Protein A/Deposited Gold Nanocrystals Modified Electrode for Carbofuran Detection

    Directory of Open Access Journals (Sweden)

    Xia Sun

    2011-12-01

    Full Text Available In this paper, an amperometric immunosensor modified with protein A/deposited gold nanocrystals (DpAu was developed for the ultrasensitive detection of carbofuran residues. First, DpAu were electrodeposited onto the Au electrode surface to absorb protein A (PA and improve the electrode conductivity. Then PA was dropped onto the surface of DpAu film, used for binding antibody Fc fragments. Next, anti-carbofuran monoclonal antibody was immobilized on the PA modified electrode. Finally, bovine serum albumin (BSA was employed to block the possible remaining active sites avoiding any nonspecific adsorption. The fabrication procedure of the immunosensor was characterized by electrochemical impedance spectroscopy (EIS and cyclic voltammetry (CV, respectively. With the excellent electroconductivity of DpAu and the PA’s oriented immobilization of antibodies, a highly efficient immuno-reaction and detection sensitivity could be achieved. The influences of the electrodeposition time of DpAu, pH of the detection solution and incubation time on the current response of the fabricated immunosensor were investigated. Under optimized conditions, the current response was proportional to the concentration of carbofuran which ranged from 1 to 100 ng/mL and 100 ng/mL to 100 μg/mL. The detection limit was 0.1924 ng/mL. The proposed carbofuran immnuosensor exhibited high specificity, reproducibility, stability and regeneration performance, which may open a new door for ultrasensitive detection of carbofuran residues in vegetables and fruits.

  11. Improvement of Amperometric Sensor Used for Determination of Nitrate with Polypyrrole Nanowires Modified Electrode

    Directory of Open Access Journals (Sweden)

    Shi-chang Wang

    2005-12-01

    Full Text Available Polypyrrole(PPy nanowire modified electrodes were developed by template-freeelectrochemical method based on graphite electrode. The modified electrode wascharacterized by their amperometric response towards nitrate ions. Before reduction ofnitrate ions, electrochemical solid-phase extraction (EC-SPE of nitrate in/on modifiedelectrodes was conducted. It is found that the unusual nanowired structure of polypyrrolelayer (instead of well known cauliflower structure allows us to increase the effectivesurface area of the electrode and subsequently the sensitivity. And the effects ofelectrochemical preparation parameters of PPy nanowire modified electrodes on theircorresponding characters were evaluated. The experimental results show that theelectrochemical preparation parameters of the modified electrodes such as scan rate,polymerization potential, temperature of polymerization solution and polymerization timehave significantly effects on the morphology of PPy nanowires and subsequently effectivesurface area of the electrode and electroreduction current density of nitrate. Thedetermination sensitivity may be varied according to the modification parameters. Under acertain polymerization conditions, the corresponding sensitivity reaches 336.28 mA/M cm2 and the detection limit is 1.52×10-6 M. The proposed method was successfully applied in thedetection of nitrate in the real samples.

  12. An Amperometric Biosensor for Glucose Determination Prepared from Glucose Oxidase Immobilized in Polyaniline-Polyvinylsulfonate Film

    Directory of Open Access Journals (Sweden)

    Halit Arslan

    2011-08-01

    Full Text Available In this study, a novel amperometric glucose biosensor with immobilization of glucose oxidase on electrochemically polymerized polyaniline-polyvinylsulphonate (Pani-Pvs films has been accomplished via the entrapment technique. Electropolymerization of aniline on the Pt surface of the Pt electrode was carried out at constant potential (0.75 V, vs. Ag/AgCl using an electrochemical cell containing aniline and polyvinylsulphonate. Firstly, the optimum working conditions for preparing polyaniline-polyvinylsulfonate films were investigated. Determination of glucose was carried out by the oxidation of enzymatically produced H2O2 at 0.4 V vs. Ag/AgCl. The effects of pH and temperature were investigated and the optimum pH value was found to be 7.5. The storage stability and operational stability of the enzyme electrode were also studied. The results show that 75% of the response current was retained after 16 activity assays. The prepared glucose biosensor retained 80.6% of initial activity after 40 days when stored in 0.1 M phosphate buffer solution at 4 °C.

  13. An Amperometric Biosensor for Glucose Determination Prepared from Glucose Oxidase Immobilized in Polyaniline-Polyvinylsulfonate Film

    Science.gov (United States)

    Arslan, Fatma; Ustabaş, Selvin; Arslan, Halit

    2011-01-01

    In this study, a novel amperometric glucose biosensor with immobilization of glucose oxidase on electrochemically polymerized polyaniline-polyvinylsulphonate (Pani-Pvs) films has been accomplished via the entrapment technique. Electropolymerization of aniline on the Pt surface of the Pt electrode was carried out at constant potential (0.75 V, vs. Ag/AgCl) using an electrochemical cell containing aniline and polyvinylsulphonate. Firstly, the optimum working conditions for preparing polyaniline-polyvinylsulfonate films were investigated. Determination of glucose was carried out by the oxidation of enzymatically produced H2O2 at 0.4 V vs. Ag/AgCl. The effects of pH and temperature were investigated and the optimum pH value was found to be 7.5. The storage stability and operational stability of the enzyme electrode were also studied. The results show that 75% of the response current was retained after 16 activity assays. The prepared glucose biosensor retained 80.6% of initial activity after 40 days when stored in 0.1 M phosphate buffer solution at 4 °C. PMID:22164068

  14. Detection of Benzoic Acid by an Amperometric Inhibitor Biosensor Based on Mushroom Tissue Homogenate

    Directory of Open Access Journals (Sweden)

    Mustafa Kemal Sezgintürk

    2005-01-01

    Full Text Available An amperometric benzoic acid-sensing inhibitor biosensor was prepared by immobilizing mushroom (Agaricus bisporus tissue homogenate on a Clark-type oxygen electrode. The effects of the quantity of mushroom tissue homogenate, the quantity of gelatin and the effect of the crosslinking agent glutaraldehyde percent on the biosensor were studied. The optimum concentration of phenol used as substrate was 200 μM. The bioanalytical properties of the proposed biosensor, such as dependence of the biosensor response on the pH value and the temperature, were investigated. The biosensor responded linearly to benzoic acid in a concentration range of 25–100 μM. Standard deviation (s.d. was ±0.49 μM for 7 successive determinations at a concentration of 75 μM. The inhibitor biosensor based on mushroom tissue homogenate was applied for the determination of benzoic acid in fizzy lemonade, some fruits and groundwater samples. Results were compared to those obtained using AOAC method, showing a good agreement.

  15. Electrooxidation and amperometric determination of vorinostat on hierarchical leaf-like gold nanolayers.

    Science.gov (United States)

    Vais, R Dehdari; Karimian, K; Heli, H

    2018-02-01

    Hierarchical leaf-like gold nanolayers were electrodeposited using choline chloride as a shape directing agent and characterized using field emission scanning electron microscopy. The electrooxidation behavior of vorinostat was then studied on the nanolayers and the kinetic parameters of the electrodic process were obtained by voltammetric measurements in a phosphate buffer solution at pH 7.40. Vorinostat was electrooxidized on the nanolayers' surface at a lower potential and with a higher rate, compared to a polycrystalline smooth gold surface, through an irreversible process. Based on the results, an amperometric sensor was designed using the hierarchical leaf-like gold nanolayers for the determination of vorinostat. A linear dynamic range of 4.0-52μmol L -1 with a calibration sensitivity of 7.7mAmol -1 L, and a detection limit of 1.40μmolL -1 were obtained. The amperometry method was also applied to the analysis of vorinostat capsules. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Amperometric Formaldehyde Sensor Based on a Pd Nanocrystal Modified C/Co2P Electrode

    Directory of Open Access Journals (Sweden)

    Huan Wang

    2017-01-01

    Full Text Available Ultrafine Pd nanocrystals were grown on the cobalt phosphide (Co2P decorated Vulcan XC-72 carbon (C/Co2P, which is realized by first implementing the corresponding metal precursor and then the further chemical reduction process. The as-synthesized C/Co2P/Pd composite was further constructed to form a gas permeable electrode. This electrode can be applied for formaldehyde (HCHO detection. The results demonstrate that the Co2P nanocrystal can significantly improve the sensing performance of the C/Co2P/Pd electrode for catalytic oxidation of HCHO, which is considered to be attributed to the effective electron transfer from Co2P to Pd in the C/Co2P/Pd composites. Furthermore, the assembled C/Co2P/Pd sensor exhibits high sensitivity of 617 nA/ppm and good selectivity toward various interfering gases such as NO2, NO, SO2, CO2, and CO. It also shows the excellent linear response that the correlation coefficient is 0.994 in the concentration range of 1–10 ppm. Therefore, the proposed cost-effective C/Co2P/Pd nanocomposite, which owns advantages such as high activity and good stability, has the potential to be applied as an effective electrocatalyst for amperometric HCHO detection.

  17. A matched-filter algorithm to detect amperometric spikes resulting from quantal secretion.

    Science.gov (United States)

    Balaji Ramachandran, Supriya; Gillis, Kevin D

    2018-01-01

    Electrochemical microelectrodes located immediately adjacent to the cell surface can detect spikes of amperometric current during exocytosis as the transmitter released from a single vesicle is oxidized on the electrode surface. Automated techniques to detect spikes are needed in order to quantify the spike rate as a measure of the rate of exocytosis. We have developed a Matched Filter (MF) detection algorithm that scans the data set with a library of prototype spike templates while performing a least-squares fit to determine the amplitude and standard error. The ratio of the fit amplitude to the standard error constitutes a criterion score that is assigned for each time point and for each template. A spike is detected when the criterion score exceeds a threshold and the highest-scoring template and the time of peak score is identified. The search for the next spike commences only after the score falls below a second, lower threshold to reduce false positives. The approach was extended to detect spikes with double-exponential decays with the sum of two templates. Receiver Operating Characteristic plots (ROCs) demonstrate that the algorithm detects >95% of manually identified spikes with a false-positive rate of ∼2%. ROCs demonstrate that the MF algorithm performs better than algorithms that detect spikes based on a derivative-threshold approach. The MF approach performs well and leads into approaches to identify spike parameters. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Critical Evaluation of Acetylcholine Determination in Rat Brain Microdialysates using Ion-Pair Liquid Chromatography with Amperometric Detection

    Directory of Open Access Journals (Sweden)

    Yvette Michotte

    2008-08-01

    Full Text Available Liquid chromatography with amperometric detection remains the most widely used method for acetylcholine quantification in microdialysis samples. Separation of acetylcholine from choline and other matrix components on a microbore chromatographic column (1 mm internal diameter, conversion of acetylcholine in an immobilized enzyme reactor and detection of the produced hydrogen peroxide on a horseradish peroxidase redox polymer coated glassy carbon electrode, achieves sufficient sensitivity for acetylcholine quantification in rat brain microdialysates. However, a thourough validation within the concentration range required for this application has not been carried out before. Furthermore, a rapid degradation of the chromatographic columns and enzyme systems have been reported. In the present study an ion-pair liquid chromatography assay with amperometric detection was validated and its long-term stability evaluated. Working at pH 6.5 dramatically increased chromatographic stability without a loss in sensitivity compared to higher pH values. The lower limit of quantification of the method was 0.3 nM. At this concentration the repeatability was 15.7%, the inter-day precision 8.7% and the accuracy 103.6%. The chromatographic column was stable over 4 months, the immobilized enzyme reactor up to 2-3 months and the enzyme coating of the amperometric detector up to 1-2 months. The concentration of acetylcholine in 30 μl microdialysates obtained under basal conditions from the hippocampus of freely moving rats was 0.40 ± 0.12 nM (mean ± SD, n = 30. The present method is therefore suitable for acetylcholine determination in rat brain microdialysates.

  19. Simple approach for the fabrication of screen-printed carbon-based electrode for amperometric detection on microchip electrophoresis.

    Science.gov (United States)

    Petroni, Jacqueline Marques; Lucca, Bruno Gabriel; Ferreira, Valdir Souza

    2017-02-15

    This paper describes a simple method for the fabrication of screen-printed based electrodes for amperometric detection on microchip electrophoresis (ME) devices. The procedure developed is quite simple and does not require expensive instrumentation or sophisticated protocols commonly employed on the production of amperometric sensors, such as photolithography or sputtering steps. The electrodes were fabricated through manual deposition of home-made conductive carbon ink over patterned acrylic substrate. Morphological structure and electrochemical behavior of the carbon electrodes were investigated by scanning electron microscopy and cyclic voltammetry. The produced amperometric sensors were coupled to polydimethylsiloxane (PDMS) microchips at end-channel configuration in order to evaluate their analytical performance. For this purpose, electrophoretic experiments were carried out using nitrite and ascorbic acid as model analytes. Separation of these substances was successfully performed within 50s with good resolution (R = 1.2) and sensitivities (713.5 pA/μM for nitrite and 255.4 pA/μM for ascorbate). The reproducibility of the fabrication method was evaluated and revealed good values concerning the peak currents obtained (8.7% for nitrite and 9.3% for ascorbate). The electrodes obtained through this method exhibited satisfactory lifetime (ca. 400 runs) over low fabrication cost (less than $1 per piece). The feasibility of the proposed device for real analysis was demonstrated through the determination of nitrite concentration levels in drinking water samples. Based on the results achieved, the approach proposed here shows itself as an interesting alternative for simple fabrication of carbon-based electrodes. Furthermore, the devices indicate great promise for other kind of analytical applications involving ME devices. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. Development of an Amperometric Biosensor Platform for the Combined Determination of L-Malic, Fumaric, and L-Aspartic Acid.

    Science.gov (United States)

    Röhlen, Désirée L; Pilas, Johanna; Schöning, Michael J; Selmer, Thorsten

    2017-10-01

    Three amperometric biosensors have been developed for the detection of L-malic acid, fumaric acid, and L -aspartic acid, all based on the combination of a malate-specific dehydrogenase (MDH, EC 1.1.1.37) and diaphorase (DIA, EC 1.8.1.4). The stepwise expansion of the malate platform with the enzymes fumarate hydratase (FH, EC 4.2.1.2) and aspartate ammonia-lyase (ASPA, EC 4.3.1.1) resulted in multi-enzyme reaction cascades and, thus, augmentation of the substrate spectrum of the sensors. Electrochemical measurements were carried out in presence of the cofactor β-nicotinamide adenine dinucleotide (NAD + ) and the redox mediator hexacyanoferrate (III) (HCFIII). The amperometric detection is mediated by oxidation of hexacyanoferrate (II) (HCFII) at an applied potential of + 0.3 V vs. Ag/AgCl. For each biosensor, optimum working conditions were defined by adjustment of cofactor concentrations, buffer pH, and immobilization procedure. Under these improved conditions, amperometric responses were linear up to 3.0 mM for L-malate and fumarate, respectively, with a corresponding sensitivity of 0.7 μA mM -1 (L-malate biosensor) and 0.4 μA mM -1 (fumarate biosensor). The L-aspartate detection system displayed a linear range of 1.0-10.0 mM with a sensitivity of 0.09 μA mM -1 . The sensor characteristics suggest that the developed platform provides a promising method for the detection and differentiation of the three substrates.

  1. Simple approach for the fabrication of screen-printed carbon-based electrode for amperometric detection on microchip electrophoresis

    Energy Technology Data Exchange (ETDEWEB)

    Petroni, Jacqueline Marques [Instituto de Química, Universidade Federal de Mato Grosso do Sul, Campo Grande, MS, 79074-460 (Brazil); Lucca, Bruno Gabriel, E-mail: bruno.lucca@ufes.br [Departamento de Ciências Naturais, Universidade Federal do Espírito Santo, São Mateus, ES, 29932-540 (Brazil); Ferreira, Valdir Souza [Instituto de Química, Universidade Federal de Mato Grosso do Sul, Campo Grande, MS, 79074-460 (Brazil)

    2017-02-15

    This paper describes a simple method for the fabrication of screen-printed based electrodes for amperometric detection on microchip electrophoresis (ME) devices. The procedure developed is quite simple and does not require expensive instrumentation or sophisticated protocols commonly employed on the production of amperometric sensors, such as photolithography or sputtering steps. The electrodes were fabricated through manual deposition of home-made conductive carbon ink over patterned acrylic substrate. Morphological structure and electrochemical behavior of the carbon electrodes were investigated by scanning electron microscopy and cyclic voltammetry. The produced amperometric sensors were coupled to polydimethylsiloxane (PDMS) microchips at end-channel configuration in order to evaluate their analytical performance. For this purpose, electrophoretic experiments were carried out using nitrite and ascorbic acid as model analytes. Separation of these substances was successfully performed within 50s with good resolution (R = 1.2) and sensitivities (713.5 pA/μM for nitrite and 255.4 pA/μM for ascorbate). The reproducibility of the fabrication method was evaluated and revealed good values concerning the peak currents obtained (8.7% for nitrite and 9.3% for ascorbate). The electrodes obtained through this method exhibited satisfactory lifetime (ca. 400 runs) over low fabrication cost (less than $1 per piece). The feasibility of the proposed device for real analysis was demonstrated through the determination of nitrite concentration levels in drinking water samples. Based on the results achieved, the approach proposed here shows itself as an interesting alternative for simple fabrication of carbon-based electrodes. Furthermore, the devices indicate great promise for other kind of analytical applications involving ME devices. - Highlights: • A novel method to fabricate screen-printed electrodes for amperometric detection in ME is demonstrated. • No sophisticated

  2. A disposable amperometric ethanol biosensor based on screen-printed carbon electrodes mediated with ferricyanide-magnetic nanoparticle mixture

    Energy Technology Data Exchange (ETDEWEB)

    Liao, M.-H. [Department of Cosmetology Styling, Applied Science Technology Research Center, Transworld Institute of Technology, Douliou, Yunlin 64063, Taiwan (China); Guo, J.-C. [Department of Chemical Engineering, National Yunlin University of Science and Technology, 123, University Rd., Sec 3, Douliou, Yunlin 64002, Taiwan (China); Chen, W.-C. [Department of Chemical Engineering, National Yunlin University of Science and Technology, 123, University Rd., Sec 3, Douliou, Yunlin 64002, Taiwan (China)]. E-mail: chenwc@yuntech.edu.tw

    2006-09-15

    Magnetic Fe{sub 3}O{sub 4} nanoparticles were prepared by co-precipitation method and used to develop a reagentless disposable amperometric ethanol (EtOH) biosensor. The electrochemical characteristics of modified processes were analyzed by cyclic voltammetry (CV) and chronoamperometry (CA). Results showed that the presence of Fe{sub 3}O{sub 4} nanoparticles could enhance the peak currents of redox species. Moreover, the alcohol biosensor exhibited an excellent sensitivity and fast response time for EtOH with a wide linear response range from 1.0 to 9.0 mM.

  3. Amperometric detection of extended-spectrum β-lactamase activity : application to the characterization of resistant E.coli strains

    OpenAIRE

    Dequaire Rochelet, Murielle; Solanas, Sébastien; Betelli, Laetitia; Neuwirth, Catherine; Vienney, Fabienne; Hartmann, Alain

    2015-01-01

    The amperometric detection of extended-spectrum β-lactamase (ESBL) with carbon screen-printed sensors was investigated in the presence of the Nitrocefin, a commercially-available β-lactamase chromogenic cephalosporin substrate. Using an ESBL isolated from a clinical sample, it was shown for the first time that the intensity of a specific anodic pic current (EP = [similar]+0.3 V vs. Ag/AgCl) resulting from the catalytic hydrolysis of the β-lactam ring was proportional to the amount of ESBL. Th...

  4. Simple approach for the fabrication of screen-printed carbon-based electrode for amperometric detection on microchip electrophoresis

    International Nuclear Information System (INIS)

    Petroni, Jacqueline Marques; Lucca, Bruno Gabriel; Ferreira, Valdir Souza

    2017-01-01

    This paper describes a simple method for the fabrication of screen-printed based electrodes for amperometric detection on microchip electrophoresis (ME) devices. The procedure developed is quite simple and does not require expensive instrumentation or sophisticated protocols commonly employed on the production of amperometric sensors, such as photolithography or sputtering steps. The electrodes were fabricated through manual deposition of home-made conductive carbon ink over patterned acrylic substrate. Morphological structure and electrochemical behavior of the carbon electrodes were investigated by scanning electron microscopy and cyclic voltammetry. The produced amperometric sensors were coupled to polydimethylsiloxane (PDMS) microchips at end-channel configuration in order to evaluate their analytical performance. For this purpose, electrophoretic experiments were carried out using nitrite and ascorbic acid as model analytes. Separation of these substances was successfully performed within 50s with good resolution (R = 1.2) and sensitivities (713.5 pA/μM for nitrite and 255.4 pA/μM for ascorbate). The reproducibility of the fabrication method was evaluated and revealed good values concerning the peak currents obtained (8.7% for nitrite and 9.3% for ascorbate). The electrodes obtained through this method exhibited satisfactory lifetime (ca. 400 runs) over low fabrication cost (less than $1 per piece). The feasibility of the proposed device for real analysis was demonstrated through the determination of nitrite concentration levels in drinking water samples. Based on the results achieved, the approach proposed here shows itself as an interesting alternative for simple fabrication of carbon-based electrodes. Furthermore, the devices indicate great promise for other kind of analytical applications involving ME devices. - Highlights: • A novel method to fabricate screen-printed electrodes for amperometric detection in ME is demonstrated. • No sophisticated

  5. Nonenzymatic amperometric sensor for ascorbic acid based on hollow gold/ruthenium nanoshells

    Energy Technology Data Exchange (ETDEWEB)

    Jo, Ara; Kang, Minkyung; Cha, Areum; Jang, Hye Su [Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750 (Korea, Republic of); Shim, Jun Ho [Department of Chemistry, Daegu University, Gyeongsan 712-714 (Korea, Republic of); Lee, Nam-Suk [National Center for Nanomaterials Technology (NCNT), Pohang University of Science and Technology (POSTECH), Pohang 790-784 (Korea, Republic of); Kim, Myung Hwa [Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750 (Korea, Republic of); Lee, Youngmi, E-mail: youngmilee@ewha.ac.kr [Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750 (Korea, Republic of); Lee, Chongmok, E-mail: cmlee@ewha.ac.kr [Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750 (Korea, Republic of)

    2014-03-01

    Highlights: • We synthesized hollow gold/ruthenium (hAu–Ru) nanoshells for ascorbic acid sensing. • The hAu–Ru nanoshells showed sensitivity of 426 μA mM⁻¹ cm⁻² for ascorbic acid. • Good selectivity against glucose, uric acid, dopamine, 4-acetamidophenol, and NADH. • The linear dynamic range appeared from zero to 2.0 mM (R = 0.9995). • Response time (1.6 s) and low detection limit (2.2 μM) were obtained at pH 7.40. Abstract: We report a new nonenzymatic amperometric detection of ascorbic acid (AA) using a glassy carbon (GC) disk electrode modified with hollow gold/ruthenium (hAu–Ru) nanoshells, which exhibited decent sensing characteristics. The hAu–Ru nanoshells were prepared by the incorporation of Ru on hollow gold (hAu) nanoshells from Co nanoparticle templates, which enabled AA selectivity against glucose without aid of enzyme or membrane. The structure and electrocatalytic activities of the hAu–Ru catalysts were characterized by spectroscopic and electrochemical techniques. The hAu–Ru loaded on GC electrode (hAu–Ru/GC) showed sensitivity of 426 μA mM⁻¹ cm⁻² (normalized to the GC disk area) for the linear dynamic range of <5 μM to 2 mM AA at physiological pH. The response time and detection limit were 1.6 s and 2.2 μM, respectively. Furthermore, the hAu–Ru/GC electrode displayed remarkable selectivity for ascorbic acid over all potential biological interferents, including glucose, uric acid (UA), dopamine (DA), 4-acetamidophenol (AP), and nicotinamide adenine dinucleotide (NADH), which could be especially good for biological sensing.

  6. Amperometric L-glutamate biosensor based on bacterial cell-surface displayed glutamate dehydrogenase

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Bo [Laboratory for Biosensing, Key Laboratory of Biofuels, and Shandong Provinicial Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy & Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao 266101 (China); University of Chinese Academy of Sciences, 19A Yuquan Road, Beijing 100049 (China); Zhang, Shu [Laboratory for Biosensing, Key Laboratory of Biofuels, and Shandong Provinicial Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy & Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao 266101 (China); Key Laboratory of Marine Chemistry Theory and Technology of Ministry of Education, Ocean University of China, 238 Songling Road, Qingdao 266100 (China); Lang, Qiaolin [Laboratory for Biosensing, Key Laboratory of Biofuels, and Shandong Provinicial Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy & Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao 266101 (China); Song, Jianxia; Han, Lihui [Key Laboratory of Marine Chemistry Theory and Technology of Ministry of Education, Ocean University of China, 238 Songling Road, Qingdao 266100 (China); Liu, Aihua, E-mail: liuah@qibebt.ac.cn [Laboratory for Biosensing, Key Laboratory of Biofuels, and Shandong Provinicial Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy & Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao 266101 (China); University of Chinese Academy of Sciences, 19A Yuquan Road, Beijing 100049 (China)

    2015-07-16

    Highlights: • E. coli surface-dispalyed Gldh exhibiting excellent enzyme activity and stability. • Sensitive amperometric biosensor for glutamate using Gldh-bacteria and MWNTs. • The glutamate biosensor exhibited high specificity and stability. - Abstract: A novel L-glutamate biosensor was fabricated using bacteria surface-displayed glutamate dehydrogenase (Gldh-bacteria). Here the cofactor NADP{sup +}-specific dependent Gldh was expressed on the surface of Escherichia coli using N-terminal region of ice nucleation protein (INP) as the anchoring motif. The cell fractionation assay and SDS-PAGE analysis indicated that the majority of INP-Gldh fusion proteins were located on the surface of cells. The biosensor was fabricated by successively casting polyethyleneimine (PEI)-dispersed multi-walled carbon nanotubes (MWNTs), Gldh-bacteria and Nafion onto the glassy carbon electrode (Nafion/Gldh-bacteria/PEI-MWNTs/GCE). The MWNTs could not only significantly lower the oxidation overpotential towards NAPDH, which was the product of NADP{sup +} involving in the oxidation of glutamate by Gldh, but also enhanced the current response. Under the optimized experimental conditions, the current–time curve of the Nafion/Gldh-bacteria/PEI-MWNTs/GCE was performed at +0.52 V (vs. SCE) by amperometry varying glutamate concentration. The current response was linear with glutamate concentration in two ranges (10 μM–1 mM and 2–10 mM). The low limit of detection was estimated to be 2 μM glutamate (S/N = 3). Moreover, the proposed biosensor is stable, specific, reproducible and simple, which can be applied to real samples detection.

  7. Amperometric Metronidazole Sensor Based on the Supermolecular Recognition by Metalloporphyrin Incorporated In Carbon Paste Electrode

    Directory of Open Access Journals (Sweden)

    Ru-Qin Yu

    2003-03-01

    Full Text Available An amperometric metronidazole (MTZ sensor using a glycosylated metalloporphyrin as a recognition element, which was incorporated in a carbon paste electrode, is reported. For the preparation of a MTZ-sensitive active material, 5, 10, 15, 20-tetrakis [2-(2, 3, 4, 6-tetraacetyl-β-D-glucopyranosyl-1-O-phenyl]porphyrin (T(oglu PPH2 and its Mn(III complex MnT(o-gluPPCl were synthesized from the reaction of pyrrole with ortho-acetylglycosylated benzaldehyde by Lindsay’s method. The MnT(oglu PPCl-modified electrode showed excellent selectivity toward MTZ with respect to a number of interferents and exhibited stable response. The calibration graph obtained with the proposed sensor was linear over the range of 2.9×10-3-5.8×10-8 M/L, with a detection limit of 5.8×10-8 M/L for MTZ. Cyclic voltammetric measurements indicated that MnT(oglu PPCl included in graphite-epoxy resin matrices could efficiently mediate electron transfer from the base electrode to MTZ causing a decrease of reduction potential for MTZ detection. The sensor could be regenerated by simply polishing with an alumina paper, with an excellent reproducibility (RSD=1.6%. The experimental conditions such as pH and applied working potential were optimized. The prepared sensor is applied for the determination of MTZ in pharmaceutical preparations and the results agreed with the values obtained by the pharmacopoeia method.

  8. An improved amperometric creatinine biosensor based on nanoparticles of creatininase, creatinase and sarcosine oxidase.

    Science.gov (United States)

    Kumar, Parveen; Jaiwal, Ranjana; Pundir, C S

    2017-11-15

    An improved amperometric biosensor for detection of creatinine was developed based on immobilization of nanoparticles (NPs) of creatininase (CA), creatinase (CI), and sarcosine oxidase (SOx) onto glassy carbon (GC) electrode. Transmission electron microscopy (TEM) and fourier transform infrared spectroscopy (FTIR) were employed for characterization of enzyme nanoparticles (ENPs). The GC electrode was characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectra (EIS) at different stages of its amendment. The biosensor showed optimum response within 2s at pH 6.0 in 0.1 M sodium phosphate buffer and 25 °C, when operated at 1.0 V against Ag/AgCl. Biosensor exhibited wider linear range from 0.01 μM to 12 μM with a limit of detection (LOD) of 0.01 μM. The analytical recoveries of added creatinine in sera were 97.97 ± 0.1% for 0.1 mM and 98.76 ± 0.2% for 0.15 mM, within and between batch coefficients of variation (CV) were 2.06% and 3.09% respectively. A good correlation (R 2  = 0.99) was observed between sera creatinine values obtained by standard enzymic colorimetric method and the present biosensor. This biosensor measured creatinine level in sera of apparently healthy subjects and persons suffering from renal and muscular dysfunction. The ENPs electrode lost 10% of its initial activity within 240 days of its regular uses, when stored at 4 °C. Copyright © 2017 Elsevier Inc. All rights reserved.

  9. Self-assembled dipeptide-gold nanoparticle hybrid spheres for highly sensitive amperometric hydrogen peroxide biosensors.

    Science.gov (United States)

    Gong, Yufei; Chen, Xu; Lu, Yanluo; Yang, Wensheng

    2015-04-15

    Novel self-assembled dipeptide-gold nanoparticle (DP-AuNP) hybrid microspheres with a hollow structure have been prepared in aqueous solution by a simple one-step method. Diphenylalanine (FF) dipeptide was used as a precursor to form simultaneously peptide spheres and a reducing agent to reduce gold ions to gold nanoparticles in water at 60°C. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that formed AuNPs were localized both inside and on the surface of the dipeptide spheres. Horseradish peroxidase (HRP) as a model enzyme was further immobilized on the dipeptide-AuNP hybrid spheres to construct a mediate H2O2 amperometric biosensor. UV-vis spectroscopy showed that the immobilized HRP retained its original structure. Cyclic voltammetry characterization demonstrated that the HRP/dipeptide-AuNP hybrid spheres modified glassy carbon electrode showed high electrocatalytic activity to H2O2. The proposed biosensor exhibited a wide linear response in the range from 5.0×10(-7) to 9.7×10(-4)M with a high sensitivity of 28.3µAmM(-1). A low detection limit of 1.0×10(-7)M was estimated at S/N=3. In addition, the biosensor possessed satisfactory reproducibility and long-term stability. These results indicated that the dipeptide-AuNP hybrid sphere is a promising matrix for application in the fabrication of electrochemical biosensors due to its excellent biocompatibility and good charge-transfer ability. Copyright © 2014 Elsevier B.V. All rights reserved.

  10. Nanostructured progesterone immunosensor using a tyrosinase-colloidal gold-graphite-Teflon biosensor as amperometric transducer

    Energy Technology Data Exchange (ETDEWEB)

    Carralero, Veronica [Department of Analytical Chemistry, Faculty of Chemistry, University Complutense of Madrid, 28040 Madrid (Spain); Gonzalez-Cortes, Araceli [Department of Analytical Chemistry, Faculty of Chemistry, University Complutense of Madrid, 28040 Madrid (Spain); Yanez-Sedeno, Paloma [Department of Analytical Chemistry, Faculty of Chemistry, University Complutense of Madrid, 28040 Madrid (Spain)]. E-mail: yseo@quim.ucm.es; Pingarron, Jose M. [Department of Analytical Chemistry, Faculty of Chemistry, University Complutense of Madrid, 28040 Madrid (Spain)

    2007-07-16

    A novel progesterone immunosensor using a colloidal gold-graphite-Teflon-tyrosinase composite biosensor as amperometric transducer is reported. A sequential competitive configuration between the analyte and progesterone labelled with alkaline phosphatase (AP) was used. Phenyl phosphate was employed as the AP-substrate and the enzyme reaction product, phenol, was oxidized by tyrosinase to o-quinone, which is subsequently reduced at -0.1 V at the biocomposite electrode. Variables such as the concentration of phenyl phosphate, the amount of antibody attached to the electrode surface, immersion time in a 2% BSA solution, working pH and incubation times in progesterone and AP conjugate were optimized. A linear calibration graph for progesterone was obtained between 0 and 40 ng mL{sup -1} with a slope value of -82.3 nA ng{sup -1} mL, and a detection limit of 0.43 ng mL{sup -1}. The time needed to reach the steady-state current from the addition of phenyl phosphate was 30-40 s. These analytical characteristics improve substantially those reported for other progesterone immunosensors. A lifetime of 14 days with no need to apply any regeneration procedure was also achieved. The usefulness of the immunosensor was evaluated by determining progesterone in milk samples spiked with the analyte at 5.0 and 1.5 ng mL{sup -1} concentration levels. Following a very simple procedure, involving only sample dilution, mean recoveries (n = 7) of 98 {+-} 3% and 99 {+-} 3%, respectively, were obtained.

  11. A Doped Polyaniline Modified Electrode Amperometric Biosensor for Gluconic Acid Determination in Grapes

    Science.gov (United States)

    Albanese, Donatella; Malvano, Francesca; Sannini, Adriana; Pilloton, Roberto; Di Matteo, Marisa

    2014-01-01

    In winemaking gluconic acid is an important marker for quantitative evaluation of grape infection by Botrytis cinerea. A screen-printed amperometric bienzymatic sensor for the determination of gluconic acid based on gluconate kinase (GK) and 6-phospho-D-gluconate dehydrogenase (6PGDH) coimmobilized onto polyaniline/poly (2-acrylamido-2-methyl-1-propanesulfonic acid; PANI-PAAMPSA) is reported in this study. The conductive polymer electrodeposed on the working electrode surface allowed the detection of NADH at low potential (0.1 V) with a linear range from 4 × 10−3 to 1 mM (R2 = 0.99) and a sensitivity of 419.44 nA·mM−1. The bienzymatic sensor has been optimized with regard to GK/6PGDH enzymatic unit ratio and ATP/NADP+ molar ratio which resulted equal to 0.33 and 1.2, respectively. Under these conditions a sensitivity of 255.2 nA·mM−1, a limit of detection of 5 μM and a Relative Standard Deviation (RSD) of 4.2% (n = 5) have been observed. Finally, the biosensor has been applied for gluconic acid measurements in must grape samples and the matrix effect has been taken into consideration. The results have been compared with those obtained on the same samples with a commercial kit based on a spectrophotometric enzyme assay and were in good agreement, showing the capability of the bienzymatic PANI-PAAMPSA biosensor for gluconic acid measurements and thus for the evaluation of Botrytis cinerea infection in grapes. PMID:24960084

  12. Covalent modification of multiwalled carbon nanotubes with neutral red for the fabrication of an amperometric hydrogen peroxide sensor

    International Nuclear Information System (INIS)

    Jeykumari, D R Shobha; Narayanan, S Sriman

    2007-01-01

    The nanoscale dimensions, graphitic surface chemistry and electronic properties of multiwalled carbon nanotubes (MWNTs) make them an ideal candidate for chemical and biochemical sensing. In this paper we explore a covalent chemical strategy for functionalization of MWNTs with neutral red through carbodiimide coupling between the primary amine of neutral red and carboxyl groups of the carbon nanotubes. The construction of an amperometric sensor was achieved by abrasive immobilization of the functionalized MWNTs on a paraffin impregnated graphite electrode followed by a coating of a thin film of nafion. The neutral red functionalized MWNTs were characterized by spectroscopic and electroanalytical methods. From the voltammetric studies, MWNTs were found to exhibit a higher accessible surface area in electrochemical reactions. The modified electrode exhibited stable electrocatalytic activity toward hydrogen peroxide reduction in a wide potential range. A significant decrease in overvoltage for the reduction of hydrogen peroxide, as well as a dramatic increase in the peak currents in comparison with a bare graphite electrode were observed. Such an ability of neutral red functionalized carbon nanotubes to promote the hydrogen peroxide electron transfer reaction with a short response time (<4 s) and long-term stability, a low detection limit, an extended linear concentration range and a high sensitivity suggest great promise for dehydrogenase and oxidase based amperometric biosensors

  13. Covalent modification of multiwalled carbon nanotubes with neutral red for the fabrication of an amperometric hydrogen peroxide sensor

    Energy Technology Data Exchange (ETDEWEB)

    Jeykumari, D R Shobha; Narayanan, S Sriman [Department of Analytical Chemistry, School of Chemical Sciences, University of Madras, Guindy Campus, Chennai-600 025 (India)

    2007-03-28

    The nanoscale dimensions, graphitic surface chemistry and electronic properties of multiwalled carbon nanotubes (MWNTs) make them an ideal candidate for chemical and biochemical sensing. In this paper we explore a covalent chemical strategy for functionalization of MWNTs with neutral red through carbodiimide coupling between the primary amine of neutral red and carboxyl groups of the carbon nanotubes. The construction of an amperometric sensor was achieved by abrasive immobilization of the functionalized MWNTs on a paraffin impregnated graphite electrode followed by a coating of a thin film of nafion. The neutral red functionalized MWNTs were characterized by spectroscopic and electroanalytical methods. From the voltammetric studies, MWNTs were found to exhibit a higher accessible surface area in electrochemical reactions. The modified electrode exhibited stable electrocatalytic activity toward hydrogen peroxide reduction in a wide potential range. A significant decrease in overvoltage for the reduction of hydrogen peroxide, as well as a dramatic increase in the peak currents in comparison with a bare graphite electrode were observed. Such an ability of neutral red functionalized carbon nanotubes to promote the hydrogen peroxide electron transfer reaction with a short response time (<4 s) and long-term stability, a low detection limit, an extended linear concentration range and a high sensitivity suggest great promise for dehydrogenase and oxidase based amperometric biosensors.

  14. Highly sensitive amperometric biosensor based on electrochemically-reduced graphene oxide-chitosan/hemoglobin nanocomposite for nitromethane determination.

    Science.gov (United States)

    Wen, Yunping; Wen, Wei; Zhang, Xiuhua; Wang, Shengfu

    2016-05-15

    Nitromethane (CH3NO2) is an important organic chemical raw material with a wide variety of applications as well as one of the most common pollutants. Therefore it is pretty important to establish a simple and sensitive detection method for CH3NO2. In our study, a novel amperometric biosensor for nitromethane (CH3NO2) based on immobilization of electrochemically-reduced graphene oxide (rGO), chitosan (CS) and hemoglobin (Hb) on a glassy carbon electrode (GCE) was constructed. Scanning electron microscopy, infrared spectroscopy and electrochemical methods were used to characterize the Hb-CS/rGO-CS composite film. The effects of scan rate and pH of phosphate buffer on the biosensor have been studied in detail and optimized. Due to the graphene and chitosan nanocomposite, the developed biosensor demonstrating direct electrochemistry with faster electron-transfer rate (6.48s(-1)) and excellent catalytic activity towards CH3NO2. Under optimal conditions, the proposed biosensor exhibited fast amperometric response (<5s) to CH3NO2 with a wide linear range of 5 μM~1.46 mM (R=0.999) and a low detection limit of 1.5 μM (S/N=3). In addition, the biosensor had high selectivity, reproducibility and stability, providing the possibility for monitoring CH3NO2 in complex real samples. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Amperometric Immunosensor for Carbofuran Detection Based on MWCNTs/GS-PEI-Au and AuNPs-Antibody Conjugate

    Directory of Open Access Journals (Sweden)

    Xiangyou Wang

    2013-04-01

    Full Text Available In this paper, an amperometric immunosensor for the detection of carbofuran was developed. Firstly, multiwall carbon nanotubes (MWCNTs and graphene sheets-ethyleneimine polymer-Au (GS-PEI-Au nanocomposites were modified onto the surface of a glass carbon electrode (GCE via self-assembly. The nanocomposites can increase the surface area of the GCE to capture a large amount of antibody, as well as produce a synergistic effect in the electrochemical performance. Then the modified electrode was coated with gold nanoparticles-antibody conjugate (AuNPs-Ab and blocked with BSA. The monoclonal antibody against carbofuran was covalently immobilized on the AuNPs with glutathione as a spacer arm. The morphologies of the GS-PEI-Au nanocomposites and the fabrication process of the immunosensor were characterized by X-ray diffraction (XRD, ultraviolet and visible absorption spectroscopy (UV-vis and scanning electron microscopy (SEM, respectively. Under optimal conditions, the immunosensor showed a wide linear range, from 0.5 to 500 ng/mL, with a detection limit of 0.03 ng/mL (S/N = 3. The as-constructed immunosensor exhibited notable performance features such as high specificity, good reproducibility, acceptable stability and regeneration performance. The results are mainly due to the excellent properties of MWCNTs, GS-PEI-Au nanocomposites and the covalent immobilization of Ab with free hapten binding sites for further immunoreaction. It provides a new avenue for amperometric immunosensor fabrication.

  16. Amperometric Gas Sensors as a Low Cost Emerging Technology Platform for Air Quality Monitoring Applications: A Review.

    Science.gov (United States)

    Baron, Ronan; Saffell, John

    2017-11-22

    This review examines the use of amperometric electrochemical gas sensors for monitoring inorganic gases that affect urban air quality. First, we consider amperometric gas sensor technology including its development toward specifically designed air quality sensors. We then review recent academic and research organizations' studies where this technology has been trialed for air quality monitoring applications: early studies showed the potential of electrochemical gas sensors when colocated with reference Air Quality Monitoring (AQM) stations. Spatially dense networks with fast temporal resolution provide information not available from sparse AQMs with longer recording intervals. We review how this technology is being offered as commercial urban air quality networks and consider the remaining challenges. Sensors must be sensitive, selective, and stable; air quality monitors/nodes must be electronically and mechanically well designed. Data correction is required and models with differing levels of sophistication are being designed. Data analysis and validation is possibly the biggest remaining hurdle needed to deliver reliable concentration readings. Finally, this review also considers the roles of companies, urban infrastructure requirements, and public research in the development of this technology.

  17. An Amperometric Biosensor Based on Alanine Dehydrogenase for the Determination of Low Level of Ammonium Ion in Water

    Directory of Open Access Journals (Sweden)

    Tan Ling Ling

    2011-01-01

    Full Text Available An amperometric electrochemical biosensor has been developed for ammonium (NH4+ ion detection by immobilising alanine dehydrogenase (AlaDH enzyme in a photocurable methacrylic membrane made up of poly(2-hydroxyethyl methacrylate (pHEMA on a screen-printed carbon paste electrode (SPE. The current detected was based on the electrocatalytic oxidation of nicotinamide adenine dinucleotide reduced (NADH that is proportional to the consumption of NH4+ ion whilst enzymatic amination of AlaDH and pyruvate is taking place. The biosensor was operated amperometrically at a potential of +0.6 V and optimum pH 7. The NH4+ biosensor demonstrated linear response to NH4+ ion concentration in the range of 0.03–1.02 mg/L with a limit of detection (LOD of 8.52 μg/L. The proposed method has been successfully applied to the determination of NH4+ ion in river water samples without any pretreatment. The levels of possible interferents in the waters were negligible to cause any interference on the proposed method. The analytical performance of the biosensor was comparable to the colorimetric method using Nesslerisation but with much lower detection limit and linear response range at ppb level.

  18. Disposable Amperometric Immunosensor for the Determination of Human P53 Protein in Cell Lysates Using Magnetic Micro-Carriers

    Directory of Open Access Journals (Sweden)

    María Pedrero

    2016-11-01

    Full Text Available An amperometric magnetoimmunosensor for the determination of human p53 protein is described in this work using a sandwich configuration involving the covalent immobilization of a specific capture antibody onto activated carboxylic-modified magnetic beads (HOOC-MBs and incubation of the modified MBs with a mixture of the target protein and horseradish peroxidase-labeled antibody (HRP-anti-p53. The resulting modified MBs are captured by a magnet placed under the surface of a disposable carbon screen-printed electrode (SPCE and the amperometric responses are measured at −0.20 V (vs. an Ag pseudo-reference electrode, upon addition of hydroquinone (HQ as a redox mediator and H2O2 as the enzyme substrate. The magnetoimmunosensing platform was successfully applied for the detection of p53 protein in different cell lysates without any matrix effect after a simple sample dilution. The results correlated accurately with those provided by a commercial ELISA kit, thus confirming the immunosensor as an attractive alternative for rapid and simple determination of this protein using portable and affordable instrumentation.

  19. An amperometric affinity penicillin-binding protein magnetosensor for the detection of β-lactam antibiotics in milk.

    Science.gov (United States)

    Gamella, M; Campuzano, S; Conzuelo, F; Esteban-Torres, M; de las Rivas, B; Reviejo, A J; Muñoz, R; Pingarrón, J M

    2013-04-07

    The preparation, characterization and performance evaluation of an amperometric affinity disposable magnetosensor, based on the use of a recombinant penicillin-binding protein (PBP) and screen-printed carbon electrodes (SPCEs), for the specific detection and quantification of β-lactam antibiotic residues in milk are reported. The PBP was immobilized onto His-Tag-Isolation-modified magnetic beads (His-Tag-Isolation-MBs), and a direct competitive assay using a tracer with horseradish peroxidase (HRP) for the enzymatic labeling was performed. The amperometric response obtained at -0.20 V vs. the Ag pseudo-reference electrode of the SPCE after the addition of H2O2 in the presence of hydroquinone (HQ) was used as the transduction signal. The developed methodology showed very low detection limits (in the low ppb level) for the 6 antibiotics tested in untreated milk samples, and a good selectivity against other antibiotic residues frequently detected in milk and dairy products. Due to the bioreceptor employed, this methodology was able to detect only the active form of β-lactam antibiotics with high affinities for both penicillins and cephalosporins. Moreover, the analysis took only 30 min.

  20. A novel, disposable, screen-printed amperometric biosensor for glucose in serum fabricated using a water-based carbon ink.

    Science.gov (United States)

    Crouch, Eric; Cowell, David C; Hoskins, Stephen; Pittson, Robin W; Hart, John P

    2005-11-15

    Screen-printed amperometric glucose biosensors have been fabricated using a water-based carbon ink. The enzyme glucose oxidase (GOD) and the electro-catalyst cobalt phthalocyanine were mixed with the carbon ink prior to the screen-printing process; therefore, biosensors are prepared in a one-step fabrication procedure. Optimisation of the biosensor performance was achieved by studying the effects of pH, buffer strength, and applied potential on the analytical response. Calibration studies were performed under optimum conditions, using amperometry in stirred solution, with an operating potential of +500 mV versus SCE. The sensitivity was found to be 1170 nA mM(-1), with a linear range of 0.025-2 mM; the former represents the detection limit. The disposable amperometric biosensor was evaluated by carrying out replicate determinations on a sample of bovine serum. This was achieved by the method of multiple standard additions and included a correction for background currents arising from oxidizable serum components. The mean serum concentration was calculated to be 8.63 mM and compared well with the supplier's value of 8.3 mM; the coefficient of variation was calculated to be 3.3% (n=6).

  1. Improved in vivo performance of amperometric oxygen (PO2) sensing catheters via electrochemical nitric oxide generation/release.

    Science.gov (United States)

    Ren, Hang; Coughlin, Megan A; Major, Terry C; Aiello, Salvatore; Rojas Pena, Alvaro; Bartlett, Robert H; Meyerhoff, Mark E

    2015-08-18

    A novel electrochemically controlled release method for nitric oxide (NO) (based on electrochemical reduction of nitrite ions) is combined with an amperometric oxygen sensor within a dual lumen catheter configuration for the continuous in vivo sensing of the partial pressure of oxygen (PO2) in blood. The on-demand electrochemical NO generation/release method is shown to be fully compatible with amperometric PO2 sensing. The performance of the sensors is evaluated in rabbit veins and pig arteries for 7 and 21 h, respectively. Overall, the NO releasing sensors measure both venous and arterial PO2 values more accurately with an average deviation of -2 ± 11% and good correlation (R(2) = 0.97) with in vitro blood measurements, whereas the corresponding control sensors without NO release show an average deviation of -31 ± 28% and poor correlation (R(2) = 0.43) at time points >4 h after implantation in veins and >6 h in arteries. The NO releasing sensors induce less thrombus formation on the catheter surface in both veins and arteries (p < 0.05). This electrochemical NO generation/release method could offer a new and attractive means to improve the biocompatibility and performance of implantable chemical sensors.

  2. Automatic bionalyzer using an integrated amperometric biosensor for the determination of L-malic acid in wines.

    Science.gov (United States)

    Vargas, E; Ruiz, M A; Ferrero, F J; Campuzano, S; Ruiz-Valdepeñas Montiel, V; Reviejo, A J; Pingarrón, J M

    2016-09-01

    A new automatic bioanalyzer for L-malic acid using an integrated amperometric biosensor as detector is reported for the first time in this work. The biosensor is constructed by gold film sputtering deposition on a stainless steel disk electrode and co-immobilization of the enzymes malate dehydrogenase (MDH) and diaphorase (DP) together with the redox mediator tetrathiafulvalene (TTF) by means of dialysis membrane. The analytical performance of the biosensor was evaluated when it was used as amperometric detector in three different analytical methodologies: stirred solutions, semiautomatic FIA system and automatic bioanalyzer. The bienzyme biosensor exhibited great analytical performance in terms of sensitivity, selectivity and reproducibility of the measurements and its usefulness was demonstrated by analyzing wine reference materials with certified content of L-malic acid. The attractive analytical and operational characteristics demonstrated by the automatic bioanalyzer make it a promising simple, rapid and field-based tool for routine wine and fruit control. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. Non-invasive determination of glucose directly in raw fruits using a continuous flow system based on microdialysis sampling and amperometric detection at an integrated enzymatic biosensor.

    Science.gov (United States)

    Vargas, E; Ruiz, M A; Campuzano, S; Reviejo, A J; Pingarrón, J M

    2016-03-31

    A non-destructive, rapid and simple to use sensing method for direct determination of glucose in non-processed fruits is described. The strategy involved on-line microdialysis sampling coupled with a continuous flow system with amperometric detection at an enzymatic biosensor. Apart from direct determination of glucose in fruit juices and blended fruits, this work describes for the first time the successful application of an enzymatic biosensor-based electrochemical approach to the non-invasive determination of glucose in raw fruits. The methodology correlates, through previous calibration set-up, the amperometric signal generated from glucose in non-processed fruits with its content in % (w/w). The comparison of the obtained results using the proposed approach in different fruits with those provided by other method involving the same commercial biosensor as amperometric detector in stirred solutions pointed out that there were no significant differences. Moreover, in comparison with other available methodologies, this microdialysis-coupled continuous flow system amperometric biosensor-based procedure features straightforward sample preparation, low cost, reduced assay time (sampling rate of 7 h(-1)) and ease of automation. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Design and Development of a Microfluidic Amperometric Immunosensor for the Quantitative Detection of 2,6-dichlorobenzamide (BAM) Herbicide Residue in Ground Water

    DEFF Research Database (Denmark)

    Uthuppu, Basil

    and it is a novel characteristic of the microfluidic device prototype. The microfluidic device was automated using Lego® Mindstorms® servomotors to control its micro pumps and valves. By confirming (amperometrically) the regeneration capability of the optimized immunosurface and generating a standard curve for BAM...

  5. Design, Preparation and Performance Study of On-Chip Flow-Through Amperometric Sensors with an Integrated Ag/AgCl Reference Electrode

    Directory of Open Access Journals (Sweden)

    He Zhang

    2018-03-01

    Full Text Available To improve the reference potential stability of on-chip amperometric sensors, we propose a novel integrated Ag/AgCl reference electrode structure. This structure can refresh the saturated potassium chloride filling solution surrounding the Ag/AgCl electrode. We then designed a flow-through amperometric sensor and a multilayer microfluidic chip based on the integrated reference electrode. In order to improve the detection signal strength of the flow-through sensor, a numerical simulation model was established. The simulation results showed that a combination of (1 using a step-type detection cell structure that maintains micro-channel width while reducing micro-channel height, and (2 controlling the sample flow rate to limit the mass transfer of the sensor surface effectively, improves the detection signal strength. The step-type detection cell structure had dimensions of 200 μm × 200 μm × 100 μm (length × width × height, and the electroosmotic flow driving voltage was 120 V/cm. Finally, successful trace detection of Mg2+ and Pb2+ in the water was achieved using the amperometric sensor and microfluidic chip: detection limits were 5 μmol/L and 84 μmol/L. The preparation of an on-chip flow-through amperometric sensor with an integrated Ag/AgCl reference electrode will facilitate improved portability of microfluidic detection technology.

  6. On-line solid-phase extraction using a C₁₈ minicolumn coupled to a flow injection system for determination of caffeine in green and roasted coffee beans.

    Science.gov (United States)

    Salinas-Vargas, María E; Cañizares-Macías, María P

    2014-03-15

    A novel and fast method based on the solid phase extraction (SPE) coupled to a flow injection system for the determination of caffeine in coffee beans was developed. The caffeine extraction of coffee beans was carried out with hot water. A C18 reverse-phase mini-column was coupled to a continuous flow manifold to carry out the on-line SPE and the quantification of caffeine from aqueous extracts. Column length, retention time, elution volume, extracting solution and injection volume were evaluated. The retention time was of 90s and the elution was carried out with 400 μL of a methanol:water mixture (25:75). The proposed on-line SPE was compared against a chloroform extraction from aqueous extracts. With the proposed method the sample preparation was minimised and the sample throughput was increased (10 determination/h) because no dilution was required. Green coffee beans and beans with different roasting degree were analyzed. Copyright © 2013 Elsevier Ltd. All rights reserved.

  7. An enzymatic method for the rapid measurement of the hemoglobin A1c by a flow-injection system comprised of an electrochemical detector with a specific enzyme-reactor and a spectrophotometer

    International Nuclear Information System (INIS)

    Nanjo, Yoko; Hayashi, Ryuzo; Yao, Toshio

    2007-01-01

    A flow-injection analytical (FIA) system, comprised of an electrochemical detector with a fructosyl-peptide oxidase (FPOX-CET) reactor and a flow-type spectrophotometer, was proposed for the simultaneous measurement of glycohemoglobin and total hemoglobin in blood cell. The blood cell samples were hemolyzed with a surfactant and then treated with protease. In the first stage of operation, total hemoglobin in digested sample was determined spectrophotometrically. In the second stage, fructosyl valyl histidine (FVH) released from glycohemoglobin by the selective proteolysis was determined specifically using the electrochemical detector with the FPOX-CET reactor. The FIA system could be automatically processed at an analytical speed of 40 samples per hour. The proposed assay method could determine selectively only the glycated N-terminal residue of β-chain in glycohemoglobin and total hemoglobin in blood cell. The enzymatic hemoglobin A 1c (HbA 1c ) value calculated by the concentration ratio of the FVH to total hemoglobin, was closely correlated with the HbA 1c values certified by the Japan Diabetic Society (JDS) and the International Federation of Clinical Chemistry (IFCC)

  8. Flow injection spectrophotometric analysis of human salivary α-amylase activity using an enzyme degradation of starch-iodine complexes in flow channel and its application to human stress testing.

    Science.gov (United States)

    Ohtomo, Takao; Igarashi, Shukuro; Takagai, Yoshitaka

    2013-01-01

    Flow injection spectrophotometric analysis (FIA) of human salivary α-amylase was developed using an enzyme degradation reaction of starch-iodine complexes. In this proposed method, the salivary α-amylase, known as a human stress indicator, is directly and rapidly determined without any pretreatment. In this study, the optimum starch-iodine complexes (i.e., optimum molecular weight and amylase-amylopectin compounding ratio) were selected, and their rapid degradation in the flow channel was investigated to determine salivary amylase in the FIA system. The determination range of α-amylase was obtained from 0.25 to 5.0 kilo Novo unit per milliliter (KNU/mL), and these concentrations were equivalent to the real concentration of amylase in human saliva. The quantitative values obtained by this method were found to be highly reproducible with 1.6% (n=25) of the relative standard deviation for 1.0 KNU/mL. The detection limit (3σ) was 60 NU/mL. In addition, the method requires small volume of a sample (20 µL), and 30 samples was sequentially measured within one hour. Real human saliva collected before and after exercise was utilized to demonstrate the feasibility of human stress test and analytical performance of this approach.

  9. Sensitivity improvement of ammonia determination based on flow-injection indophenol spectrophotometry with manganese(II) ion as a catalyst and analysis of exhaust gas of thermal power plant.

    Science.gov (United States)

    Tsuboi, Tomonori; Hirano, Yoshio; Shibata, Yoshinori; Motomizu, Shoji

    2002-10-01

    The sensitivity improvement of a flow-injection spectrophotometric method for the determination of ammonia was examined based on an indophenol blue coloration reaction with salicylate and hypochlorite in the presence of manganese(II) as a reaction promotion catalyst. The optimal conditions for achieving higher sensitivity of ammonia determination were examined using a three-line flow system. The limit of detection corresponding to a signal-to-noise ratio (S/N) of 3 was 0.005 mg l(-1) (approximately equal to 5 ppb) of NH4+. A calibration graph was linear in the range from 5 ppb to 1,000 ppb of ammonium ion. The relative standard deviations (n = 9) for 50 ppb and 100 ppb of ammonium ion were 6.4% and 2.2%, respectively. The proposed method was applied to the determination of ammonia in the exhaust gas of a thermal power plant. Prior to the FIA determination, ammonia in the exhaust gas was absorbed into a boric acid solution; the absorption solution was then analyzed by the proposed FIA.

  10. Amperometric biosensors for detection of sugars based on the electrical wiring of different pyranose oxidases and pyranose dehydrogenases with osmium redox polymer on graphite electrodes

    Czech Academy of Sciences Publication Activity Database

    Tasca, F.; Timur, S.; Ludwig, R.; Haltrich, D.; Volc, Jindřich; Antiochia, R.; Gorton, L.

    2007-01-01

    Roč. 19, 2-3 (2007), s. 294-302 ISSN 1040-0397 Institutional research plan: CEZ:AV0Z50200510 Keywords : nonselective sugar oxidizing enzyme * flow injection analysis * biofuel cell anode Subject RIV: EE - Microbiology, Virology Impact factor: 2.949, year: 2007

  11. Flow injection potentiometric determination of chlorpromazine.

    Science.gov (United States)

    Sales, M Goreti F; Tomás, José F C; Lavandeira, Sandra R

    2006-06-16

    New chlorpromazine selective electrodes with a tubular arrangement and no internal reference solution are proposed. Selective membranes are of poly(vinyl chloride) (PVC) with the tetraphenylborate.chlorpromazine (TPB.CPZ) ion-exchanger dissolved in o-nitrophenyl octyl ether (oNPOE). Analytical features of the electrodes were evaluated on a single-channel flow assembly having 500 microl injection volumes and flow-rates of 4.5 ml min(-1). For a carrier solution of 3.3 x 10(-3)M in sodium sulphate, Nernstian response was observed over the concentration range 1.0 x 10(-5) to 1.0 x 10(-2)M. Average slopes were about 59 mV decade(-1) and squared correlation coefficients were >0.9984. Slight hiper-Nernstian behaviour was observed in buffer solutions of 4.4 pH; average slopes were of 62.06 mV decade(-1). The electrode displayed a good selectivity for CPZ, with respect to, several foreign inorganic and organic species. The selective electrodes were successfully applied to the analysis of pure solutions and pharmaceutical preparations. Proposed method allows the analysis of 84 samples h(-1), producing wastewaters of low toxicity. The proposed method offers the advantage of simplicity, accuracy, applicability to coloured and turbid samples, and automation feasibility.

  12. Assessment of cadmium and iron adsorption in sediment, employing a flow injection analysis system with on line filtration and detection by flame atomic absorption spectrometry and thermospray flame furnace atomic absorption spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Fagner Moreira de; Marchioni, Camila; Barros, Juan A. V de A. [Universidade Federal de Alfenas (UNIFAL-MG), Instituto de Química, Rua GabrielMonteiro da Silva, 714, CEP 37130-000, Alfenas-MG (Brazil); Lago, Ayla Campos do [Universidade Federal de São Carlos (UFSCar-SP), Departamento de Química, 10Rodovia Washington Luís, Km 235-SP 310, CEP 16565-905, São Carlos-SP (Brazil); Wisniewski, Célio [Universidade Federal de Alfenas (UNIFAL-MG), Instituto de Química, Rua GabrielMonteiro da Silva, 714, CEP 37130-000, Alfenas-MG (Brazil); Luccas, Pedro Orival, E-mail: pedro.luccas@unifal-mg.edu.br [Universidade Federal de Alfenas (UNIFAL-MG), Instituto de Química, Rua GabrielMonteiro da Silva, 714, CEP 37130-000, Alfenas-MG (Brazil)

    2014-01-27

    Graphical abstract: -- Highlights: •A FIA system with on-line filtration for isotherms adsorption studies was proposed. •Isotherms for iron and cadmium elements in bottom lake sediment were done. •Inferences about adsorption/desorption mechanisms were feasible. •The proposed method turns the isotherm studies fast and reliable. -- Abstract: This work presents an evaluation of iron and cadmium adsorption in sediment of the Furnas Hydroelectric Plant Reservatory located in Alfenas, Minas Gerais (Brazil). The metal determination was done employing a flow injection analysis (FIA) with an on-line filtering system. As detection techniques, flame atomic absorption spectrometry (FAAS) for iron and thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) for cadmium determinations were used. The developed methodology presented good limits of detection, being 190 μg L{sup −1} for iron and 1.36 μg L{sup −1} for cadmium, and high sampling frequency for both metals 144 and 60 readings h{sup −1} for iron and cadmium, respectively. Both metals obey the Langmuir model, with maximum adsorptive capacity of 0⋅169 mg g{sup −1} for iron and 7⋅991 mg g{sup −1} for cadmium. For iron, a pseudo-first-order kinetic model was obtained with a theoretical Q{sub e} = 9⋅8355 mg g{sup −1} (experimental Q{sub e} = 9⋅5432 mg g{sup −1}), while for cadmium, a pseudo-second-order kinetic model was obtained, with a theoretical Q{sub e} = 0.3123 mg g{sup −1} (experimental Q{sub e} = 0⋅3052 mg g{sup −1})

  13. Determination of inorganic mercury and total mercury in biological and environmental samples by flow injection-cold vapor-atomic absorption spectrometry using sodium borohydride as the sole reducing agent

    International Nuclear Information System (INIS)

    Rio Segade, Susana; Tyson, Julian F.

    2003-01-01

    A simple, fast, precise and accurate method to determine inorganic mercury and total mercury in biological and environmental samples was developed. The optimized flow-injection mercury system permitted the separate determination of inorganic mercury and total mercury using sodium borohydride as reducing agent. Inorganic mercury was selectively determined after reduction with 10 -4 % w/v sodium borohydride, while total mercury was determined after reduction with 0.75% w/v sodium borohydride. The calibration graphs were linear up to 30 ng ml -1 . The detection limits of the method based on three times the standard deviation of the blank were 24 and 3.9 ng l -1 for total mercury and inorganic mercury determination, respectively. The relative standard deviation was less than 1.5% for a 10 ng ml -1 mercury standard. As a means of checking method performance, deionized water and pond water samples were spiked with methylmercury and inorganic mercury; quantitative recovery for total mercury and inorganic mercury was obtained. The accuracy of the method was verified by analyzing alkaline and acid extracts of five biological and sediment reference materials. Microwave-assisted extraction procedures resulted in higher concentrations of recovered mercury species, lower matrix interference with mercury determination and less time involved in sample treatment than conventional extraction procedures. The standard addition method was only needed for calibration when biological samples were analyzed. The detection limits were in the range of 1.2-19 and 6.6-18 ng g -1 in biological and sediment samples for inorganic mercury and total mercury determination, respectively

  14. Double injection/single detection asymmetric flow injection manifold for spectrophotometric determination of ascorbic acid and uric acid: Selection the optimal conditions by MCDM approach based on different criteria weighting methods

    Science.gov (United States)

    Boroumand, Samira; Chamjangali, Mansour Arab; Bagherian, Ghadamali

    2017-03-01

    A simple and sensitive double injection/single detector flow injection analysis (FIA) method is proposed for the simultaneous kinetic determination of ascorbic acid (AA) and uric acid (UA). This method is based upon the difference between the rates of the AA and UA reactions with Fe3 + in the presence of 1, 10-phenanthroline (phen). The absorbance of Fe2 +/1, 10-phenanthroline (Fe-phen) complex obtained as the product was measured spectrophotometrically at 510 nm. To reach a good accuracy in the differential kinetic determination via the mathematical manipulations of the transient signals, different criteria were considered in the selection of the optimum conditions. The multi criteria decision making (MCDM) approach was applied for the selection of the optimum conditions. The importance weights of the evaluation criteria were determined using the analytic hierarchy process, entropy method, and compromised weighting (CW). The experimental conditions (alternatives) were ranked by the technique for order preference by similarity to an ideal solution. Under the selected optimum conditions, the obtained analytical signals were linear in the ranges of 0.50-5.00 and 0.50-4.00 mg L- 1 for AA and UA, respectively. The 3σ detection limits were 0.07 mg L- 1 for AA and 0.12 mg L- 1 for UA. The relative standard deviations for four replicate determinations of AA and UA were 2.03% and 3.30% respectively. The method was also applied for the analysis of analytes in the blood serum, Vitamine C tablets, and tap water with satisfactory results.

  15. Separation of human milk oligosaccharides using high-performance anion-exchange chromatography with pulsed amperometric detection

    DEFF Research Database (Denmark)

    Lie, Aleksander; Pedersen, Lars Haastrup

    Human Milk Oligosaccharides (HMOs) are composed of 5 different monosaccharides: D-glucose, D galactose, L-fucose, N-acetylneuraminic acid and N-acetylglucosamine. Approximately 200 unique structures have been identified, ranging in degree of polymerization from 3 to 22. The diversity among......) with pulsed amperometric detection (PAD) is an analysis method highly suited for carbohydrates. HPAE with alkaline eluents results in retention of neutral carbohydrates depending on the number of charged groups in the molecule, pH and concentration of competing anions, while PAD has sensitivity...... for carbohydrates in the pmol-range (Lee 1990). In the present study, the aim is to develop analysis methods that can provide separation and quantification of the common structural constituents mentioned, as well as the disaccharide lactose and oligosaccharides such as lacto-N-triose II, lacto-N-tetraose and lacto...

  16. Simultaneous determination of electroactive and non-electroactive food preservatives by novel capillary electrophoresis with amperometric detection.

    Science.gov (United States)

    Wang, Weiyu; Wang, Yiping; Zhang, Junbo; Chu, Qingcui; Ye, Jiannong

    2010-09-23

    A novel capillary electrophoresis and amperometric detection method was achieved by adding an electroactive additive (3,4-dihydroxybenzylamine, 3,4-DHBA) to the running buffer, so that both electroactive and non-electroactive food preservatives were simultaneously determined. Under the selected optimum conditions, four electroactive preservatives (methylparaben, ethylparaben, propylparaben and butylparaben) and two non-electroactive preservatives (potassium sorbate and sodium lactate) were well separated and sensitively detected with detection limits (S/N=3) ranging from 1.06×10(-8) to 2.73×10(-6) g mL(-1). This method has been successfully employed for the determination of both electroactive and non-electroactive preservatives in several food commodities. Copyright © 2010 Elsevier B.V. All rights reserved.

  17. Determination of Patulin Using Amperometric Tyrosinase Biosensors Based on Electrodes Modified with Carbon Nanotubes and Gold Nanoparticles

    Directory of Open Access Journals (Sweden)

    R.M. Varlamova

    2016-06-01

    Full Text Available New amperometric biosensors based on platinum screen printed electrodes modified with multi-walled carbon nanotubes, gold nanoparticles, and immobilized enzyme – tyrosinase have been developed for determination of patulin in the concentrations of 1·10–6 – 8·10–12 mol/L with an error of no more than 0.063. The best conditions for obtaining gold nanoparticles have been chosen. The conditions for immobilization of multi-walled carbon nanotubes and gold nanoparticles on the surface of the planar electrode have been revealed. The conditions for functioning of the proposed biosensors have been identified. The results have been used to control the content of patulin in food products within and lower than the maximum allowable levels.

  18. Amperometric Detection of Sub-ppm Formaldehyde Using Single-Walled Carbon Nanotubes and Hydroxylamines: A Referenced Chemiresistive System.

    Science.gov (United States)

    Ishihara, Shinsuke; Labuta, Jan; Nakanishi, Takashi; Tanaka, Takeshi; Kataura, Hiromichi

    2017-10-27

    We report amperometric detection of formaldehyde (HCHO) using hydroxylamine hydrochloride and single-walled carbon nanotubes (SWCNTs). Hydroxylamine hydrochloride reacts with HCHO to emit HCl vapor, which injects a hole carrier into semiconducting SWCNTs. The increase of conductivity in SWCNTs is easily monitored using an ohmmeter. The debundling of SWCNTs with a metallo-supramolecular polymer (MSP) increased the active surface area in the SWCNTs network, leading to excellent sensitivity to HCHO with a limit of detection (LoD) of 0.016 ppm. The response of sensor is reversible, and the sensor is reusable. The selectivity to HCHO is 10 5 -10 6 times higher than interferences with other volatiles such as water, methanol, and toluene. Moreover, false-positive responses caused by a significant variation of humidity and/or temperature are successfully discriminated from true-positive responses by using two sensors, one with and the other without hydroxylamine hydrochloride, in a referenced system.

  19. Amperometric L-lysine biosensor based on carboxylated multiwalled carbon nanotubes-SnO2 nanoparticles-graphene composite

    Science.gov (United States)

    Kaçar, Ceren; Erden, Pınar Esra; Kılıç, Esma

    2017-10-01

    A novel matrix, carboxylated multiwalled carbon nanotubes-tin oxide nanoparticles-graphene-chitosan (c-MWCNTs-SnO2-GR-CS) composite, was prepared for biosensor construction. Lysine oxidase (LOx) enzyme was immobilized covalently on the surface of c-MWCNTs-GR-SnO2-CS composite modified glassy carbon electrode (GCE) using N-ethyl-N‧-(3-dimethyaminopropyl) carbodiimide (EDC) and N-hydroxyl succinimide (NHS). Effects of electrode composition and buffer pH on biosensor response were investigated to optimize the working conditions. The biosensor exhibited wide linear range (9.9 × 10-7 M-1.6 × 10-4 M), low detection limit (1.5 × 10-7 M), high sensitivity (55.20 μA mM-1 cm-2) and fast amperometric response (alternative for L-lysine biosensing. The practical applicability of the biosensor in two dietary supplements has also been addressed.

  20. A glassy carbon electrode modified with graphene oxide and silver nanoparticles for amperometric determination of hydrogen peroxide

    International Nuclear Information System (INIS)

    Noor, An’amt Mohamed; Shahid, Muhammad Mehmood; Rameshkumar, Perumal; Huang, Nay Ming

    2016-01-01

    The article describes a glassy carbon electrode (GCE) modified with a nanocomposite consisting of graphene oxide and silver nanoparticles, and its application to amperometric determination of hydrogen peroxide (H 2 O 2 ). Cyclic voltammetry with this modified electrode reveals efficient electrocatalytic reduction of H 2 O 2 . The response to H 2 O 2 at a working potential of −0.3 V (vs. Ag/AgCl) is linear in the 100 μM to 11 mM concentration range at pH 7.2. The limit of detection is 28.3 μM (at an S/N ratio of 3). Good selectivity is observed over physiological interferents such as dopamine, ascorbic acid, uric acid and glucose. (author)

  1. Effect of yeast pretreatment on the characteristics of yeast-modified electrodes as mediated amperometric biosensors for lactic acid.

    Science.gov (United States)

    Garjonyte, R; Melvydas, V; Malinauskas, A

    2008-11-01

    Carbon paste electrode modified with baker' and wine yeast Saccharomyces cerevisiae (a source of flavocytochrome b(2)) were investigated as amperometric biosensors for L-lactic acid. Before immobilization on the electrode surface, yeast cells were pretreated with various electrolytes, alcohols and weak organic acids. Electrode responses to L-lactic acid were tested in the presence of various mediators (potassium ferricyanide, phenazine methosulfate, 2,6-dichlorophenolindophenol sodium salt hydrate, 1,2-naphthoquinone-4-sulfonic acid sodium salt). The highest (144+/-7 nA per 0.2 mM L-lactic acid) and the most stable responses were obtained after yeast pretreatment with 30% ethanol using potassium ferricyanide as a mediator. Different electrode sensitivities with mediator phenazine methosulphate probably reflected diverse changes in yeast membrane (and/or cell wall).

  2. An experimental design approach to optimize an amperometric immunoassay on a screen printed electrode for Clostridium tetani antibody determination.

    Science.gov (United States)

    Patris, Stéphanie; Vandeput, Marie; Kenfack, Gersonie Momo; Mertens, Dominique; Dejaegher, Bieke; Kauffmann, Jean-Michel

    2016-03-15

    An immunoassay for the determination of anti-tetani antibodies has been developed using a screen printed electrode (SPE) as solid support for toxoid (antigen) immobilization. The assay was performed in guinea pig serum. The immunoreaction and the subsequent amperometric detection occurred directly onto the SPE surface. The assay consisted of spiking the anti-tetani sample directly onto the toxoid modified SPE, and then a second antibody, i.e. a HRP-labeled anti-immunoglobulin G, was deposited onto the biosensor. Subsequent amperometric detection was realized by spiking 10 µL of a hydroquinone (HQ) solution into 40 µL of buffer solution containing hydrogen peroxide. An experimental design approach was implemented for the optimization of the immunoassay. The variables of interest, such as bovine serum albumin (BSA) concentration, incubation times and labeled antibody dilution, were optimized with the aid of the response surface methodology using a circumscribed central composite design (CCCD). It was observed that two factors exhibited the greatest impact on the response, i.e. the anti-tetani incubation time and the dilution factor of the labeled antibody. It was discovered that in order to maximize the response, the dilution factor should be small, while the anti-tetani antibody incubation time should be long. The BSA concentration and the HRP-anti-IgG incubation had very limited influence. Under the optimized conditions, the immunoassay had a limit of detection of 0.011 IU/mL and a limit of quantification of 0.012 IU/mL. These values were below the protective human antibody limit of 0.06 IU/mL. Copyright © 2015 Elsevier B.V. All rights reserved.

  3. Cleanup and analysis of sugar phosphates in biological extracts by using solid phase extraction and anion-exchange chromatography with pulsed amperometric detection

    DEFF Research Database (Denmark)

    Smith, Hans Peter; Cohen, A.; Buttler, T.

    1998-01-01

    A cleanup method based on anion-exchange solid-phase extraction (SPE) was developed to render biological extracts suitable for the analysis of hexose phosphates with a modified anion-exchange chromatography method and pulsed amperometric detection. The method was applied to cell extracts of Sacch......A cleanup method based on anion-exchange solid-phase extraction (SPE) was developed to render biological extracts suitable for the analysis of hexose phosphates with a modified anion-exchange chromatography method and pulsed amperometric detection. The method was applied to cell extracts...... of Saccharomyces cerevisiae obtained by using cold methanol as quenching agent and chloroform as extraction solvent. It was shown that pretreatment of the cell extract with SPE markedly improved the quality of the liquid chromatography analysis with recoveries of the sugar phosphates close to 100%. Furthermore...

  4. High-Performance Gas Sensing of CO:  Comparative Tests for Semiconducting (SnO(2)-Based) and for Amperometric Gas Sensors.

    Science.gov (United States)

    Bârsan, N; Stetter, J R; Findlay, M; Göpel, W

    1999-07-01

    A comparison of the stability and sensitivity for two different sensor types (semiconductor SnO(2) devices, amperometric electrochemical sensors) has been performed. Sensitivities and drifts in the signal and in the background for various concentrations of CO have been studied for thick-film SnO(2) sensors (Pt and Pd doped) for a period in excess of 8 months. Similar performance data have been recorded for commercial amperometric sensors for a period in excess of 4 years. The two different sensor types investigated here were also compared to the well-known commercial Figaro TGS 822 sensor at similar concentrations. An objective approach for comparing different types of sensors has been developed using the "analytical sensitivity".

  5. An ICP-MS procedure to determine Cd, Co, Cu, Ni, Pb and Zn in oceanic waters using in-line flow-injection with solid-phase extraction for preconcentration.

    Science.gov (United States)

    O'Sullivan, Jeanette E; Watson, Roslyn J; Butler, Edward C V

    2013-10-15

    An automated procedure including both in-line preconcentration and multi-element determination by an inductively coupled plasma mass spectrometer (ICP-MS) has been developed for the determination of Cd, Co, Cu, Ni, Pb and Zn in open-ocean samples. The method relies on flow injection of the sample through a minicolumn of chelating (iminodiacetate) sorbent to preconcentrate the trace metals, while simultaneously eliminating the major cations and anions of seawater. The effectiveness of this step is tested and reliability in results are secured with a rigorous process of quality assurance comprising 36 calibration and reference samples in a run for analysis of 24 oceanic seawaters in a 6-h program. The in-line configuration and procedures presented minimise analyst operations and exposure to contamination. Seawater samples are used for calibration providing a true matrix match. The continuous automated pH measurement registers that chelation occurs within a selected narrow pH range and monitors the consistency of the entire analytical sequence. The eluent (0.8M HNO3) is sufficiently strong to elute the six metals in 39 s at a flow rate of 2.0 mL/min, while being compatible for prolonged use with the mass spectrometer. Throughput is one sample of 7 mL every 6 min. Detection limits were Co 3.2 pM, Ni 23 pM, Cu 46 pM, Zn 71 pM, Cd 2.7 pM and Pb 1.5 pM with coefficients of variation ranging from 3.4% to 8.6% (n=14) and linearity of calibration established beyond the observed concentration range of each trace metal in ocean waters. Recoveries were Co 96.7%, Ni 102%, Cu 102%, Zn 98.1%, Cd 92.2% and Pb 97.6%. The method has been used to analyse ~800 samples from three voyages in the Southern Ocean and Tasman Sea. It has the potential to be extended to other trace elements in ocean waters. © 2013 Elsevier B.V. All rights reserved.

  6. Simultaneous determination of 13 carbohydrates using high-performance anion-exchange chromatography coupled with pulsed amperometric detection and mass spectrometry.

    Science.gov (United States)

    Zhao, Dan; Feng, Feng; Yuan, Fei; Su, Jin; Cheng, Yan; Wu, Hanqiu; Song, Kun; Nie, Bo; Yu, Lian; Zhang, Feng

    2017-04-01

    A simple, accurate, and highly sensitive method was developed for the determination of 13 carbohydrates in polysaccharide of Spirulina platensis based on high-performance anion-exchange chromatography coupled with pulsed amperometric detection and mass spectrometry. Samples were extracted with deionized water using ultrasonic-assisted extraction, and the ultrasound-assisted extraction conditions were optimized by Box-Behnken design. Then the extracted polysaccharide was hydrolyzed by adding 1 mol/L trifluoroacetic acid before determination by high-performance anion-exchange chromatography coupled with pulsed amperometric detection and confirmed by high-performance anion-exchange chromatography coupled with mass spectrometry. The high-performance anion-exchange chromatography coupled with pulsed amperometric detection method was performed on a CarboPac PA20 column by gradient elution using deionized water, 0.1 mol/L sodium hydroxide solution, and 0.4 mol/L sodium acetate solution. Excellent linearity was observed in the range of 0.05-10 mg/L. The average recoveries ranged from 80.7 to 121.7%. The limits of detection and limits of quantification for 13 carbohydrates were 0.02-0.10 and 0.2-1.2  μg/kg, respectively. The developed method has been successfully applied to ambient samples, and the results indicated that high-performance anion-exchange chromatography coupled with pulsed amperometric detection and mass spectrometry could provide a rapid and accurate method for the simultaneous determination of carbohydrates. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. The use of different glucose oxidases for the development of an amperometric reagentless glucose biosensor based on gold nanoparticles covered by polypyrrole

    International Nuclear Information System (INIS)

    German, Natalija; Kausaite-Minkstimiene, Asta; Ramanavicius, Arunas; Semashko, Tatiana; Mikhailova, Raisa; Ramanaviciene, Almira

    2015-01-01

    Graphical abstract: Display Omitted -- ABSTRACT: The amperometric glucose biosensors based on adsorbed electron transfer mediator (ETM) tetrathiafulvalene (TTF) or 1,10-phenanthroline-5,6-dione (PD) and glucose oxidase (GOx) from Aspergillus niger (GOx A.niger ), Penicillium adametzii (GOx P.adametzii ) or Penicillium funiculosum (GOx P.funiculosum ) cross-linked with glutaraldehyde were investigated. ETM and enzyme were immobilized layer by layer on bare graphite rod electrode (GR) premodified with gold nanoparticles (AuNP) of (i) 3.5 nm (GOx/ETM/AuNP 3.5 /GR), (ii) 6.0 nm (GOx/ETM/AuNP 6.0 /GR) and (iii) 13.0 nm (GOx/ETM/AuNP 13.0 /GR) size. The amperometric signals for all the developed biosensors were higher using PD in comparison with TTF. The biosensor based on GOx P.funiculosum showed higher analytical signal to glucose in a comparison to biosensors based on GOx A.niger and GOx P.adametzii . The registered current to glucose using GOx P.funiculosum /PD/AuNP 3.5 /GR electrode was linear in the glucose range from 0.1 to 10.0 mmol L −1 and the limit of detection was 0.024 mmol L −1 . Enzymatical synthesis of polypyrrole (Ppy) layer on the electrode was applied in order to expand the linear glucose detection range. After 22 h of polymerization the amperometric signal was linear in the glucose concentration range from 0.1 to 25.0 mmol L −1 , while after 69 h this rage was increased up to 50.0 mmol L −1 . Additionally Ppy layer on the electrode surface reduced the influence of interfering species on the amperometric signal. The performance of developed biosensor was investigated in human serum samples

  8. Magnetic Beads-Based Sensor with Tailored Sensitivity for Rapid and Single-Step Amperometric Determination of miRNAs

    Directory of Open Access Journals (Sweden)

    Eva Vargas

    2017-11-01

    Full Text Available This work describes a sensitive amperometric magneto-biosensor for single-step and rapid determination of microRNAs (miRNAs. The developed strategy involves the use of direct hybridization of the target miRNA (miRNA-21 with a specific biotinylated DNA probe immobilized on streptavidin-modified magnetic beads (MBs, and labeling of the resulting heteroduplexes with a specific DNA–RNA antibody and the bacterial protein A (ProtA conjugated with an horseradish peroxidase (HRP homopolymer (Poly-HRP40 as an enzymatic label for signal amplification. Amperometric detection is performed upon magnetic capture of the modified MBs onto the working electrode surface of disposable screen-printed carbon electrodes (SPCEs using the H2O2/hydroquinone (HQ system. The magnitude of the cathodic signal obtained at −0.20 V (vs. the Ag pseudo-reference electrode demonstrated linear dependence with the concentration of the synthetic target miRNA over the 1.0 to 100 pM range. The method provided a detection limit (LOD of 10 attomoles (in a 25 μL sample without any target miRNA amplification in just 30 min (once the DNA capture probe-MBs were prepared. This approach shows improved sensitivity compared with that of biosensors constructed with the same anti-DNA–RNA Ab as capture instead of a detector antibody and further labeling with a Strep-HRP conjugate instead of the Poly-HRP40 homopolymer. The developed strategy involves a single step working protocol, as well as the possibility to tailor the sensitivity by enlarging the length of the DNA/miRNA heteroduplexes using additional probes and/or performing the labelling with ProtA conjugated with homopolymers prepared with different numbers of HRP molecules. The practical usefulness was demonstrated by determination of the endogenous levels of the mature target miRNA in 250 ng raw total RNA (RNAt extracted from human mammary epithelial normal (MCF-10A and cancer (MCF-7 cells and tumor tissues.

  9. Application of a macrocycle immobilized silica gel sorbent to flow injection on-line microcolumn preconcentration and separation coupled with flame atomic absorption spectrometry for interference-free determination of trace lead in biological and environmental samples.

    Science.gov (United States)

    Yan, X P; Sperling, M; Welz, B

    1999-10-01

    A simple and highly selective flow injection on-line pre-concentration and separation-flame atomic absorption spectrometric method was developed for routine analysis of trace amounts of lead in biological and environmental samples. The selective preconcentration of lead was achieved in a wide range of sample acidity (0.075 to > or = 3 mol L(-1)HNO3) on a microcolumn (145 microL) packed with a macrocycle immobilized on silica gel. The lead retained on the column was effectively eluted with an EDTA solution (0.03 mol L(-1), pH 10.5). Three kinds of potential interferences, i.e., preconcentration inferences from metal ions with an ionic radius similar to that of Pb(II) due to their competition for the cavity of the macrocyle, elution kinetic interferences from ions which form stable complexes with EDTA due to their competition for EDTA, and interferences in the atomizer from residual matrix, were evaluated and compared in view of the read-out mode of the analyte response (peak area vs peak height), column wash step (with vs without), column capacity (50 vs 145 microL), and column shape (conical vs cylindrical). The results showed that a combination of increase in column capacity, quantitation based on peak area, and use of dilute nitric acid for column wash before elution efficiently avoid the above-mentioned potential interferences. With the use of a 145 microL column the present system tolerated up to 0.1 g L(-1) Ba(II), 1 g L(-1) Sr(II), and at least 10 g L(-1) Fe(III), Cu(II), Ni(II), Zn(II), Cd(II), Al(III), K(I), Na(I), CaII), and Mg(II) in the sample digest. Further improvement of the interference tolerance can be achieved by increasing column capacity if more complicated samples need to be analyzed. At a sample loading rate of 3.9 mL min(-1) with 30-s preconcentration, an enrichment factor of 52, a detection limit (3s) of 5 micrograms L(-1) Pb in the digest and a sampling frequency of 63 h(-1) were obtained. The precision (RSD, n = 11) at the 200 micrograms L

  10. An amperometric uric acid biosensor based on Bis[sulfosuccinimidyl] suberate crosslinker/3-aminopropyltriethoxysilane surface modified ITO glass electrode

    International Nuclear Information System (INIS)

    Ahuja, Tarushee; Rajesh; Kumar, Devendra; Tanwar, Vinod Kumar; Sharma, Vikash; Singh, Nahar; Biradar, Ashok M.

    2010-01-01

    A label free, amperometric uric acid biosensor is described by immobilizing enzyme uricase through a self assembled monolayer (SAM) of 3-aminopropyltriethoxysilane (APTES) using a crosslinker, Bis[sulfosuccinimidyl]suberate (BS 3 ) on an indium-tin-oxide (ITO) coated glass plate. The biosensor (uricase/BS 3 /APTES/ITO) was characterized by, scanning electron microscopy (SEM), atomic force microscopy (AFM) and electrochemical techniques. Chronoamperometric response was measured as a function of uric acid concentration in aqueous solution (pH 7.4). The biosensor shows a linear response over a concentration range of 0.05 to 0.58 mM with a sensitivity of 39.35 μA mM -1 . The response time is 50 s reaching to a 95% steady state current value and about 90% of enzyme activity is retained for about 7 weeks. These results indicate an efficient binding of enzyme with the crosslinker over the surface of APTES modified ITO glass plates, which leads to an improved sensitivity and shelf life of the biosensor.

  11. Analysis of human milk oligosaccharides using high-performance anion-exchange chromatography with pulsed amperometric detection

    DEFF Research Database (Denmark)

    Lie, Aleksander; Pedersen, Lars Haastrup

    Human Milk Oligosaccharides (HMOs) are composed of 5 different monosaccharides: D-glucose, D-galactose, L-fucose, N-acetylneuraminic acid and N-acetylglucosamine. Approximately 200 unique structures have been identified, ranging in the degree of polymerization from 3 to 22. The diversity among......-based molecules necessitates analysis methods that can provide separation and quantification of the common structural constituents mentioned, as well as the disaccharide lactose (Galβ1-4Glc) and oligosaccharides such as lacto-N-triose II (GlcNAcβ1-3Galβ1-4Glc), lacto-N-tetraose (Galβ1-3GlcNAcβ1-3Galβ1-4Glc......) and lacto-N-neotetraose (Galβ1-4GlcNAcβ1-3Galβ1-4Glc), among others. High-performance anion-exchange chromatography (HPAE) with pulsed amperometric detection (PAD) is an analysis method highly suited for carbohydrates. HPAE with alkaline eluents results in retention of neutral carbohydrates depending...

  12. Novel amperometric sensor using metolcarb-imprinted film as the recognition element on a gold electrode and its application

    Energy Technology Data Exchange (ETDEWEB)

    Pan Mingfei; Fang Guozhen; Liu Bing; Qian Kun [Key Laboratory of Food Nutrition and Safety, Ministry of Education of China, Tianjin University of Science and Technology, Tianjin 300457 (China); Wang Shuo, E-mail: pmf2006@126.com [Key Laboratory of Food Nutrition and Safety, Ministry of Education of China, Tianjin University of Science and Technology, Tianjin 300457 (China)

    2011-04-01

    A molecularly imprinted film is electrochemically synthesized on a gold electrode using cyclic voltammetry to electropolymerize o-aminothiophenol in the presence of metolcarb (MTMC). The mechanism of the imprinting process and a number of factors affecting the activity of the imprinted film are discussed and optimized. Scanning electron microscope observations and binding measurements have proved that an MTMC-imprinted film (with a thickness of nearly 100 nm) was formed on the surface of the gold electrode. The film exhibited high binding affinity and selectivity towards the template MTMC, as well as good penetrability, reproducibility and stability. A novel amperometry sensor using the imprinted film as recognition element was developed for MTMC determination in food samples. Under the experimental conditions, the MTMC standard is linear within the concentration range studied (r{sup 2} = 0.9906). The limit of detection (S/N = 3) of the modified electrode was achieved to 1.34 x 10{sup -8} mol L{sup -1}. Recoveries of MTMC from spiked apple juice, cabbage and cucumber samples for the developed electrochemical assay ranged from 94.80% to 102.43%, which was with great correlation coefficient (0.9929) with results from high-performance liquid chromatography. In practical application, the prepared amperometric sensor also showed good reproducibility and long lifetime for storage. The research in this study has offered a rapid, accurate and sensitive electrochemical method for quantitative determination of MTMC in food products.

  13. Microfluidic device for the detection of glucose using a micro direct methanol fuel cell as an amperometric detection power source.

    Science.gov (United States)

    Ito, Takeshi; Kunimatsu, Masayuki; Kaneko, Satoru; Ohya, Seishiro; Suzuki, Koji

    2007-02-15

    We designed and prepared a novel microbiosensing system consisting of a microbioreactor fabricated using photosensitive sheets intercalated between Pyrex wafers as a dam structure, together with a micro fuel cell as a power source device between the electrodes for amperometric detection. The dam structure retains enzyme (glucose oxidase, GOx)-immobilized microbeads in a microchannel. Microelectrodes are used as an integrated detector within a microchannel located downstream of the dam structure, and these are used to detect the oxidation current of hydrogen peroxide produced from a glucose sample and GOx. A micro direct methanol fuel cell (mu-DMFC, i.d. 500 microm) was fabricated on a polymeric substrate and was used to supply a potential for the electrochemical detector. In this case, two mu-DMFCs were stacked on one substrate to increase the voltage for the oxidation of hydrogen peroxide. A linear response curve was obtained in range from 0.1 to 10 mM glucose for the designed microbiosensing system. These results show that a microfluidic biosensing system designed with a mu-DMFC device is useful and has the potential to assist minuaturization and simplification of the sensing system, in addition to increasing disposability of the device.

  14. Detection of Waterborne and Airborne Formaldehyde: From Amperometric Chemosensing to a Visual Biosensor Based on Alcohol Oxidase

    Directory of Open Access Journals (Sweden)

    Sasi Sigawi

    2014-02-01

    Full Text Available A laboratory prototype of a microcomputer-based analyzer was developed for quantitative determination of formaldehyde in liquid samples, based on catalytic chemosensing elements. It was shown that selectivity for the target analyte could be increased by modulating the working electrode potential. Analytical parameters of three variants of the amperometric analyzer that differed in the chemical structure/configuration of the working electrode were studied. The constructed analyzer was tested on wastewater solutions that contained formaldehyde. A simple low-cost biosensor was developed for semi-quantitative detection of airborne formaldehyde in concentrations exceeding the threshold level. This biosensor is based on a change in the color of a solution that contains a mixture of alcohol oxidase from the yeast Hansenula polymorpha, horseradish peroxidase and a chromogen, following exposure to airborne formaldehyde. The solution is enclosed within a membrane device, which is permeable to formaldehyde vapors. The most efficient and sensitive biosensor for detecting formaldehyde was the one that contained alcohol oxidase with an activity of 1.2 U·mL−1. The biosensor requires no special instrumentation and enables rapid visual detection of airborne formaldehyde at concentrations, which are hazardous to human health.

  15. Microfluidics and nanoparticles based amperometric biosensor for the detection of cyanobacteria (Planktothrix agardhii NIVA-CYA 116) DNA.

    Science.gov (United States)

    Ölcer, Zehra; Esen, Elif; Ersoy, Aylin; Budak, Sinan; Sever Kaya, Dilek; Yağmur Gök, Mehmet; Barut, Serkan; Üstek, Duran; Uludag, Yildiz

    2015-08-15

    Some of the cyanobacteria produce protease inhibitor oligopeptides such as cyanopeptolins and cause drinking water contamination; hence, their detection has great importance to monitor the well-being of water sources that is used for human consumption. In the current study, a fast and sensitive nucleic acid biosensor assay has been described where cyanopeptolin coding region of one of the cyanobacteria (Planktothrix agardhii NIVA-CYA 116) genome has been used as target for monitoring of the fresh water resources. A biochip that has two sets of Au electrode arrays, each consist of shared reference/counter electrodes and 3 working electrodes has been used for the assay. The biochip has been integrated to a microfluidics system and all steps of the assay have been performed during the reagent flow to achieve fast and sensitive DNA detection. On-line hybridization of the target on to the capture probe immobilized surface resulted in a very short assay duration with respect to the conventional static assays. The binding of the avidin and enzyme modified Au nanoparticles to the biotinylated detection probe and the subsequent injection of the substrate enabled a real-time amperometric measurement with a detection limit of 6×10(-12) M target DNA (calibration curve r(2)=0.98). The developed assay enables fast and sensitive detection of cyanopeptolin producing cyanobacteria from freshwater samples and hence shows a promising technology for toxic microorganism detection from environmental samples. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. An amperometric immunosensor with a DNA polyion complex membrane/gold nanoparticles-backbone for antibody immobilisation

    Energy Technology Data Exchange (ETDEWEB)

    Li Na [Chongqing Key Laboratory of Analytical Chemistry, College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China); Zhao Hongwen [Department of kidney, Southwest Hospital, The Third Military Medical University, Chongqing 400038 (China); Yuan Ruo [Chongqing Key Laboratory of Analytical Chemistry, College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China)], E-mail: yuanruo@swu.edu.cn; Peng Kanfu [Department of kidney, Southwest Hospital, The Third Military Medical University, Chongqing 400038 (China)], E-mail: talkmanpeng@sohu.com; Chai Yaqin [Chongqing Key Laboratory of Analytical Chemistry, College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China)

    2008-12-30

    A new and effective strategy for constructing a mediator-type amperometric immunosensor based on the unique characteristics of DNA-PDDA polyion complex membrane and gold nanoparticles was described. A poly(toluidine blue O) (PTOB) film deposited on a DNA-PDDA polyion complex membrane surface, exhibited excellent electrochemical redox property. Stable and well-defined redox peaks for the PTOB redox couple were obtained in pH 6.5 phosphate buffer solution (PBS). The introduction of DNA-PDDA polyion complex film not only enhanced the electrode surface area for construction of efficient biosensors, but also acted as a charge carrier to facilitate the electron transfer. Moreover, as a host matrix, the DNA-PDDA polyion complex could firmly immobilise the PTOB membrane on the surface of electrode by strong interaction. With carcinoembryonic antigen (CEA) as a model antigen, the presence of gold nanoparticles provided a congenial microenvironment for adsorbing biomolecules and decreased the electron transfer impedance. The fabrication process of the immunosensor was characterized by atomic force microscopy (AFM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The immunosensor displayed a high-sensitivity for the detection of CEA and had good correlation for the detection of CEA in the range of 0.5-120.0 ng/ml with a detection limit of 0.3 ng/ml (estimated at a signal-to-noise ratio of 3). The proposed immunosensor showed a broader linear range, good reproducibility, and storage stability.

  17. Amperometric detection of carbohydrates based on the glassy carbon electrode modified with gold nano-flake layer

    Directory of Open Access Journals (Sweden)

    Huy Du Nguyen

    2015-09-01

    Full Text Available An electro-deposition approach was established to incorporate the gold nano-flakes onto the glassy carbon electrode in electrochemical cells (nano-Au/GC/ECCs. Using pulsed amperometric detection (PAD without any gold oxidation for cleaning (non-oxidative PAD, the nano-Au/GC/ECCs were able to maintain their activity for oxidizing of carbohydrates in a normal alkaline medium. The reproducibility of peak area was about 2 relative standard deviation (RSD,% for 6 consecutive injections. A dynamic range of carbohydrates was obtained over a concentration range of 5–80 mg L−1 and the limits of detection (LOD were of 2 mg L−1 for fructose and lactose and 1 mg L−1 for glucose and galactose. Moreover, the nano-Au/GC/ECC using the non-oxidative PAD was able to combine with the internal standard method for determination of lactose in fresh cow milk sample.

  18. Layer-by-layer assemblies of chitosan/multi-wall carbon nanotubes and glucose oxidase for amperometric glucose biosensor applications

    International Nuclear Information System (INIS)

    Wu Baoyan; Hou Shihua; Yu Min; Qin Xia; Li, Sha; Chen Qiang

    2009-01-01

    A novel amperometric glucose biosensor based on multilayer films containing chitosan, multi-wall carbon nanotubes (MWCNTs) and glucose oxidase (GOD) was developed. MWCNTs were solubilized in chitosan (Chit-MWCNTs) used to interact with GOD. Poly (allylamine) (PAA) and polyvinylsulfuric acid potassium salt (PVS) were alternately deposited on the cleaned Pt electrode surface ((PVS/PAA) 3 /Pt). The (PVS/PAA) 3 /Pt electrode was alternately immersed in Chit-MWCNTs and GOD to assemble different layers of multilayer films. PBS washing was applied at the end of each assembly deposition for dissociating the weak adsorption. Micrographs of MWCNTs were obtained by scanning electron microscope, and properties of the resulting biosensors were measured by electrochemical measurements. Among the resulting biosensors, the biosensor based on eight layers of multilayer films was best. The resulting biosensor was able to efficiently monitor glucose, with the response time within 8 s, a detection limit of 21 μM estimated at a signal-to-noise ratio of 3, a linear range of 1-10 mM, the sensitivity of 0.45 μA/mM, and well stability. The study can provide a feasible simple approach on developing a new immobilization matrix for biosensors and surface functionalization

  19. Amperometric catechol biosensor based on laccase immobilized on nitrogen-doped ordered mesoporous carbon (N-OMC)/PVA matrix

    Science.gov (United States)

    Guo, Meiqing; Wang, Hefeng; Huang, Di; Han, Zhijun; Li, Qiang; Wang, Xiaojun; Chen, Jing

    2014-06-01

    A functionalized nitrogen-containing ordered mesoporous carbon (N-OMC), which shows good electrical properties, was synthesized by the carbonization of polyaniline inside a SBA-15 mesoporous silica template. Based on this, through entrapping laccase onto the N-OMC/polyvinyl alcohol (PVA) film a facilely fabricated amperometric biosensor was developed. Laccase from Trametes versicolor was assembled on a composite film of a N-OMC/PVA modified Au electrode and the electrochemical behavior was investigated. The results indicated that the N-OMC modified electrode exhibits electrical properties towards catechol. The optimum experimental conditions of a biosensor for the detection of catechol were studied in detail. Under the optimal conditions, the sensitivity of the biosensor was 0.29 A*M-1 with a detection limit of 0.31 μM and a linear detection range from 0.39 μM to 8.98 μM for catechol. The calibration curve followed the Michaelis-Menten kinetics and the apparent Michaelis-Menten \\left( K_{M}^{app} \\right) was 6.28 μM. This work demonstrated that the N-OMC/PVA composite provides a suitable support for laccase immobilization and the construction of a biosensor.

  20. Amperometric catechol biosensor based on laccase immobilized on nitrogen-doped ordered mesoporous carbon (N-OMC)/PVA matrix

    International Nuclear Information System (INIS)

    Guo, Meiqing; Wang, Hefeng; Huang, Di; Han, Zhijun; Wang, Xiaojun; Li, Qiang; Chen, Jing

    2014-01-01

    A functionalized nitrogen-containing ordered mesoporous carbon (N-OMC), which shows good electrical properties, was synthesized by the carbonization of polyaniline inside a SBA-15 mesoporous silica template. Based on this, through entrapping laccase onto the N-OMC/polyvinyl alcohol (PVA) film a facilely fabricated amperometric biosensor was developed. Laccase from Trametes versicolor was assembled on a composite film of a N-OMC/PVA modified Au electrode and the electrochemical behavior was investigated. The results indicated that the N-OMC modified electrode exhibits electrical properties towards catechol. The optimum experimental conditions of a biosensor for the detection of catechol were studied in detail. Under the optimal conditions, the sensitivity of the biosensor was 0.29 A*M −1 with a detection limit of 0.31 μM and a linear detection range from 0.39 μM to 8.98 μM for catechol. The calibration curve followed the Michaelis–Menten kinetics and the apparent Michaelis–Menten (K M app ) was 6.28 μM. This work demonstrated that the N-OMC/PVA composite provides a suitable support for laccase immobilization and the construction of a biosensor. (papers)

  1. Amperometric catechol biosensor based on laccase immobilized on nitrogen-doped ordered mesoporous carbon (N-OMC)/PVA matrix.

    Science.gov (United States)

    Guo, Meiqing; Wang, Hefeng; Huang, Di; Han, Zhijun; Li, Qiang; Wang, Xiaojun; Chen, Jing

    2014-06-01

    A functionalized nitrogen-containing ordered mesoporous carbon (N-OMC), which shows good electrical properties, was synthesized by the carbonization of polyaniline inside a SBA-15 mesoporous silica template. Based on this, through entrapping laccase onto the N-OMC/polyvinyl alcohol (PVA) film a facilely fabricated amperometric biosensor was developed. Laccase from Trametes versicolor was assembled on a composite film of a N-OMC/PVA modified Au electrode and the electrochemical behavior was investigated. The results indicated that the N-OMC modified electrode exhibits electrical properties towards catechol. The optimum experimental conditions of a biosensor for the detection of catechol were studied in detail. Under the optimal conditions, the sensitivity of the biosensor was 0.29 A*M -1 with a detection limit of 0.31 μ M and a linear detection range from 0.39 μ M to 8.98 μ M for catechol. The calibration curve followed the Michaelis-Menten kinetics and the apparent Michaelis-Menten [Formula: see text] was 6.28 μ M. This work demonstrated that the N-OMC/PVA composite provides a suitable support for laccase immobilization and the construction of a biosensor.

  2. Indirect amperometric sensing of dopamine using a redox-switchable naphthoquinone-terminated self-assembled monolayer on gold electrode

    International Nuclear Information System (INIS)

    Hammami, Asma; Raouafi, Noureddine; Sahli, Rihab

    2016-01-01

    We report on the design of a simple yet sensitive and selective electrode for amperometric determination of dopamine at a cathodic potential as low as −0.30 V vs. Ag/AgCl. The electrode was obtained by self-assembly of ω-mercaptopropyl naphthoquinone (NQ-SAM) on the surface of a polycrystalline gold electrode. The presence of dopamine induces an increase of the reduction current peak at −0.30 V corresponding to the reduction of naphthoquinone to hydronaphthoquinone. Dopamine and dopamine-quinone accumulate on the surface to form a 3D network linked by hydrogen bonds. Raman and infrared spectroscopy as well as atomic force microscopy confirmed the multilayer formation. The method allows dopamine to be indirectly detected at a working potential that is lower by 0.50 V than the standard oxidation potential at a bare gold electrode. The sensor shows distinct oxidation potentials for dopamine (120 mV), ascorbic acid (280 mV) and uric acid (520 mV) which makes the method fairly selective. The analytical range extends from 1 to 100 μM concentrations of dopamine, and the limits of detection and quantification are 0.040 and 0.134 μM, respectively. (author)

  3. An Amperometric Acetylcholinesterase Sensor Based on the Bio-templated Synthesis of Hierarchical Mesoporous Bioactive Glass Microspheres

    Science.gov (United States)

    Lv, Zhuo; Luo, Ruiping; Xi, Lijuan; Chen, Yang; Wang, Hongsu

    2017-11-01

    This work describes the synthesis of three-dimensional hollow hierarchical mesoporous bioactive glass (HMBG) microspheres based on Herba leonuri pollen grains via a hydrothermal method. The HMBG microspheres perfectly copied the hierarchical porous structure and inner hollow structure constituting the double-layer surface of the natural Herba leonuri pollen grains. This structural mimicry of the pollen grains resulted in a higher degree of adsorption of acetylcholinesterase (AChE) on HMBG microspheres in comparison with mesoporous bioactive glass. Subsequently, an amperometric biosensor for the detection of Malathion was fabricated by immobilizing AChE onto an HMBG microspheres-modified carbon paste electrode. The biosensor response exhibited two good linear ranges during an incubation time of 10 min in the malathion concentration ranges of 0.02-50 ppb and 50-600 ppb, with a detection limit of 0.0135 ppb ( S/ N = 3). Overall, the prepared enzymatic biosensor showed high sensitivity in the rapid detection of Malathion and could be applied to detect pesticide residues in vegetable matter.

  4. Influence of aspect ratio and surface defect density on hydrothermally grown ZnO nanorods towards amperometric glucose biosensing applications

    Science.gov (United States)

    Shukla, Mayoorika; Pramila; Dixit, Tejendra; Prakash, Rajiv; Palani, I. A.; Singh, Vipul

    2017-11-01

    In this work, hydrothermally grown ZnO Nanorods Array (ZNA) has been synthesized over Platinum (Pt) coated glass substrate, for biosensing applications. In-situ addition of strong oxidizing agent viz KMnO4 during hydrothermal growth was found to have profound effect on the physical properties of ZNA. Glucose oxidase (GOx) was later immobilized over ZNA by means of physical adsorption process. Further influence of varying aspect ratio, enzyme loading and surface defects on amperometric glucose biosensor has been analyzed. Significant variation in biosensor performance was observed by varying the amount of KMnO4 addition during the growth. Moreover, investigations revealed that the suppression of surface defects and aspect ratio variation of the ZNA played key role towards the observed improvement in the biosensor performance, thereby significantly affecting the sensitivity and response time of the fabricated biosensor. Among different biosensors fabricated having varied aspect ratio and surface defect density of ZNA, the best electrode resulted into sensitivity and response time to be 18.7 mA cm-2 M-1 and bio-sensing applications.

  5. On the Electrooxidation and Amperometric Detection of NO Gas at the Pt/Nafion® Electrode

    Directory of Open Access Journals (Sweden)

    Jin-Cherng Yang

    2003-08-01

    Full Text Available The electrochemical oxidation of nitric oxide (NO gas at the Pt/Nafion® electrode has been studied at a concentration of 500 ppm. The electrooxidation of NO taking place over a wide potential range can be described by a transcendental equation, from which the half-wave potential of the reaction can be determined. For NO oxidation with appreciable overpotentials but negligible mass-transfer effects, the Tafel kinetics applies. The obtained charge transfer coefficient (a and the exchange current density (io are 0.77 and 14 mA/cm2, respectively. An amperometric NO gas sensor based on the Pt/Nafion® electrode has been fabricated and tested over the NO concentration range from 0 to 500 ppm. The Pt/Nafion® electrode was used as an anode at a fixed potential, preferably 1.15 V (vs. Ag/AgCl/sat. KCl, which assures current limitation by diffusion only. The sensitivity of the electrochemical sensor was found to be 1.86 mA/ppm/cm2. The potential interference by other gases, such as nitrogen dioxide (NO2 and carbon monoxide (CO, was also studied in the range 0-500 ppm. Both sensitivity for NO and selectivity of NO over NO2/CO show significant enhancement upon using a cyclic voltammetric (CV activation, or cleaning procedure.

  6. Carbon Fiber Ultramicrodic Electrode Electrodeposited with Over-Oxidized Polypyrrole for Amperometric Detection of Vesicular Exocytosis from Pheochromocytoma Cell

    Directory of Open Access Journals (Sweden)

    Li Wang

    2015-01-01

    Full Text Available Vesicular exocytosis is ubiquitous, but it is difficult to detect within the cells’ communication mechanism. For this purpose, a 2 µm ultramicrodic carbon fiber electrode was fabricated in this work based on electrodeposition with over-oxidized polypyrrole nanoparticle (PPyox-CFE, which was applied successfully for real-time monitoring of quantal exocytosis from individual pheochromocytoma (PC12 cells. PPyox-CFE was evaluated by dopamine (DA solutions through cyclic voltammetry and amperometry electrochemical methods, and results revealed that PPyox-CFE improved the detection limit of DA. In particular, the sensitivity of DA was improved to 24.55 µA·µM−1·µm−2 using the PPyox-CFE. The ultramicrodic electrode combined with the patch-clamp system was used to detect vesicular exocytosis of DA from individual PC12 cells with 60 mM K+ stimulation. A total of 287 spikes released from 7 PC12 cells were statistically analyzed. The current amplitude (Imax and the released charge (Q of the amperometric spikes from the DA release by a stimulated PC12 cell is 45.1 ± 12.5 pA and 0.18 ± 0.04 pC, respectively. Furthermore, on average ~562,000 molecules were released in each vesicular exocytosis. PPyox-CFE, with its capability of detecting vesicular exocytosis, has potential application in neuron communication research.

  7. Field-amplified sample injection in capillary electrophoresis with amperometric detection for the ultratrace analysis of diastereomeric ephedrine alkaloids.

    Science.gov (United States)

    Chen, Xiaoyan; Tang, Yanxia; Wang, Shaoyun; Song, Yunping; Tang, Fengxiang; Wu, Xiaoping

    2015-08-01

    A coupling method of field-amplified sample injection (FASI) CE with amperometric detection is developed for ultratrace analysis of ephedrine alkaloids stereoisomers. FASI was introduced by injecting electrokinetically the sample solution for 10 s into the capillary filled with highly conductive background electrolyte (BGE). The diastereomeric selectivity and the detection sensitivity were improved by using borate buffer of high ionic strength as BGE. Parameters affecting FASI and CE separation were investigated to achieve the optimal conditions. Four analytes were separated within 15 min using 200 mmol/L borate buffer (pH 9.5) and separation voltage of +18 kV, with detection potential at +1.0 V (vs. Ag/AgCl) and carbon disc electrode as working electrode. Excellent linearity was observed between peak current and concentration of analytes in the range of 0.1-100 ng/mL. The LODs (S/N = 3) for (-)-ephedrine, (+)-pseudoephedrine, (-)-N-methylephedrine and (+)-N-methylpseudoephedrine were 39.3, 54.9, 30.8, and 44.1 pg/mL, respectively. The proposed method was successfully applied to the determination of alkaloids in Ephedra sinica, with results agreed well with HPLC method. Mean recoveries of 102.1-109.7% and RSDs less than 6% were found. And the merits of high sensitivity and selectivity, as well as a simple and stable operation, have been demonstrated. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Determination of sugar compounds in olive plant extracts by anion-exchange chromatography with pulsed amperometric detection.

    Science.gov (United States)

    Cataldi, T R; Margiotta, G; Iasi, L; Di Chio, B; Xiloyannis, C; Bufo, S A

    2000-08-15

    We describe a chromatographic method that uses isocratic elution and pulsed amperometric detection to determine soluble carbohydrates in plant tissues. Such a method provides a rapid and convenient means to obtain a complete profile of the sugar components of leaves and roots from olive (Olea europaea L. cv. Coratina) plants. A simple purification of plant extracts using pure water was developed, which is far less time-consuming and retains a high level of accuracy. Excellent separation of myo-inositol, galactinol, mannitol, galactose, glucose, fructose, sucrose, raffinose, and stachyose was achieved with an anion-exchange column and 12 mM NaOH spiked with 1 mM barium acetate as an eluent. At a flow rate of 1.0 mL/min, the time of analysis was less than 25 min, and repeatability of the method on the order of 2.2% as RSD or better for retention times and lower than 5.2% for peak areas. Recoveries approximated 100% (range 97.2-104.5%), and the method provided good precision with a coefficient of variation which ranged between 0.9 and 3.3%. Among identified carbohydrates extracted from leaves and roots of olive plants, glucose and mannitol were major compounds. Their molar ratio was estimated to be 1.2+/-0.1 and 2.2+/-0.3 for olive leaves and roots, respectively. The occurrence of soluble galactinol in plant tissues was also validated.

  9. Nano-Au/cMWCNT ModifiedspeBGene Specific Amperometric Sensor for Rapidly DetectingStreptococcus pyogenescausing Rheumatic Heart Disease.

    Science.gov (United States)

    Kaushal, Ankur; Singh, Swati; Kumar, Ashok; Kumar, Dinesh

    2017-03-01

    A specific 5' NH 2 labeled DNA probe of speB gene was immobilized onto the gold nanoparticles/carboxylated multi walled carbon nanotubes (Nano-Au/cMWCNT) screen printed electrode using EDC/NHS cross linking chemistry. This was followed by hybridization with 0.5-50 ng/6 µl of single stranded genomic DNA Streptococcus pyogenes infected patient throat swab samples. Electrochemical amperometric assay was deciphered by using cyclic voltammetry (CV) with methylene blue a redox indicator. The sensor had a sensitivity of 104.7 µA cm -2  ng -1 using CV with a R 2 of 0.907 and 0.01 ng/6 µl as the limit of detection (LOD). The modified electrode surface morphology was characterized using scanning electron microscopy. The stability of the electrode was seen at 4 °C for 180 days having 6% loss in the initial current. The sensor is speB gene specific and can detect the pathogen within 30 min.

  10. Capillary electrophoresis with amperometric detection of curcumin in Chinese herbal medicine pretreated by solid-phase extraction.

    Science.gov (United States)

    Sun, Xiuhua; Gao, Changlu; Cao, Weidong; Yang, Xiurong; Wang, Erkang

    2002-07-12

    In the present study, curcumin from Chinese herbal medicine turmeric was determined by capillary electrophoresis with amperometric detection (CE-AD) pretreated by a self-designed, simple, inexpensive solid-phase extraction (SPE) cartridge based on the material of tributyl phosphate resin. An average concentration factor of 9 with the recovery of > 80% was achieved when applied to the analysis of curcumin in extracts of tumeric. Under the optimized CE-AD conditions: a running buffer composed of 15 mM phosphate buffer at a pH 9.7, separation voltage at 16 kV, injection for 6 s at 9 kV and detection at 1.20 V, CE-AD with SPE exhibited low detection limit as 3 x 10(-8) mol/l (S/N = 3), high efficiency of 1.0 x 10(5) N, linear range of 7 x 10(-4) -3 x 10(-6) mol/l (r = 0.9986) for curcumin extracted from light petroleum. The method developed resulted in enhancement of the detection sensitivity and reduction of interference from sample matrix in complicated samples and exhibited the potential application for routine analysis, especially in food, because a relatively complete process of sample treatment and analysis was described.

  11. Simultaneous Determination of the Main Peanut Allergens in Foods Using Disposable Amperometric Magnetic Beads-Based Immunosensing Platforms

    Directory of Open Access Journals (Sweden)

    Víctor Ruiz-Valdepeñas Montiel

    2016-06-01

    Full Text Available In this work, a novel magnetic beads (MBs-based immunosensing approach for the rapid and simultaneous determination of the main peanut allergenic proteins (Ara h 1 and Ara h 2 is reported. It involves the use of sandwich-type immunoassays using selective capture and detector antibodies and carboxylic acid-modified magnetic beads (HOOC-MBs. Amperometric detection at −0.20 V was performed using dual screen-printed carbon electrodes (SPdCEs and the H2O2/hydroquinone (HQ system. This methodology exhibits high sensitivity and selectivity for the target proteins providing detection limits of 18.0 and 0.07 ng/mL for Ara h 1 and Ara h 2, respectively, with an assay time of only 2 h. The usefulness of the approach was evaluated by detecting the endogenous content of both allergenic proteins in different food extracts as well as trace amounts of peanut allergen (0.0001% or 1.0 mg/kg in wheat flour spiked samples. The developed platform provides better Low detection limits (LODs in shorter assay times than those claimed for the allergen specific commercial ELISA kits using the same immunoreagents and quantitative information on individual food allergen levels. Moreover, the flexibility of the methodology makes it readily translate to the detection of other food-allergens.

  12. Amperometric sensing of anti-HIV drug zidovudine on Ag nanofilm-multiwalled carbon nanotubes modified glassy carbon electrode

    Energy Technology Data Exchange (ETDEWEB)

    Rafati, Amir Abbas, E-mail: aa_rafati@basu.ac.ir; Afraz, Ahmadreza

    2014-06-01

    The zidovudine (ZDV) is the first drug approved for the treatment of HIV virus infection. The detection and determination of this drug are very importance in human serum because of its undesirable effects. A new ZDV sensor was fabricated on the basis of nanocomposite of silver nanofilm (Ag-NF) and multiwalled carbon nanotubes (MWCNTs) immobilized on glassy carbon electrode (GCE). The modified electrodes were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), cyclic voltammetry (CV), and linear sweep voltammetry (LSV) techniques. Results showed that the electrodeposited silver has a nanofilm structure and further electrochemical studies showed that the prepared nanocomposite has high electrocatalytic activity and is appropriate for using in sensors. The amperometric technique under optimal conditions is used for the determination of ZDV ranging from 0.1 to 400 ppm (0.37 μM–1.5 mM) with a low detection limit of 0.04 ppm (0.15 μM) (S/N = 3) and good sensitivity. The prepared sensor possessed accurate and rapid response to ZDV and shows an average recovery of 98.6% in real samples. - Highlights: • New anti-HIV drug sensor was fabricated on the basis of nanomaterials composite. • The GCE modified by prepared hydrophilic MWCNT silver nanoparticles. • Silver nanofilm electrodeposited on MWCNT/GCE and characterized by SEM, EDX, CV and LSV • Response of electrode to ZDV was thoroughly investigated by electrochemical techniques.

  13. Determinação espectrofotométrica de vitamina B2 (riboflavina) em formulações farmacêuticas empregando sistema de análises por injeção em fluxo Spectrophotometric determination of vitamin B2 (riboflavin) in pharmaceutical formulations using flow injection analysis

    OpenAIRE

    Clezio Aniceto; Larissa de Souza Canaes; Orlando Fatibello-Filho; Carla C. S. Cavalheiro

    2000-01-01

    A flow injection spectrophotometric procedure exploiting merging zones is proposed for determining vitamin B2 (riboflavin) in pharmaceutical preparations. The determination is based on the red-colored complex formation between vitamin B2 and silver(I) which was measured at 520 nm. Vitamin B2 was determined in four pharmaceutical preparations in the 1.0 to 50.0 mg L-1 concentration range, with a detection limit of 0.5 mg L-1. The recovery from three samples ranged from 98.0 to 104.0 %. The ana...

  14. Development of a novel biosensor based on a polypyrrole-dodecylbenzene sulphonate (PPy-DBS) film for the determination of amperometric cholesterol.

    Science.gov (United States)

    Özer, Bayram Oğuz; Çete, Servet

    2017-06-01

    Herein a novel amperometric biosensor based on a conducting polymer with anionic dopant modified electrode was successfully developed for detection of cholesterol. Polypyrrole is deposited on a platinum surface and the sodium dodecylbenzene sulphonate (DBS) ion-doped polypyrrole film was electrochemically prepared by scanning the electrode potential between -0.8 and +0.8 V at a scan rate of 20 mV/s. The present electrochemical biosensor was optimized in terms of working potential, number of cycles, concentrations of monomer, and anionic dopant. Cholesterol oxidase (ChOx) was physically entrapped in PPy-DBS to construct an amperometric cholesterol biosensor. Amperometric determination is based on the electrochemical detection of H 2 O 2 generated in the enzymatic reaction of cholesterol. Kinetic parameters, operational and storage stabilities, pH, and temperature dependencies were determined. Km and Imax were calculated as 0.11 μM and 0.967 nM/min, respectively. The operational stability results showed that 90.0% of the response current was retained after 30 activity assays. Morphology of electrodes was characterized by SEM and AFM. Additionally, contact angle measurements were made with 1 μL water of polymer film and enzyme electrode. As a result, the cholesterol biosensor suggested in this study is easy to prepare and is highly cost-effective. This composite (PPy-DBS) can supply a biocompatible and electrochemical microenvironment for immobilization of the enzyme, making this material a good candidate for the fabrication of highly sensitive and selective cholesterol biosensors.

  15. Detection and quantification of new psychoactive substances (NPSs) within the evolved "legal high" product, NRG-2, using high performance liquid chromatography-amperometric detection (HPLC-AD).

    Science.gov (United States)

    Zuway, Khaled Y; Smith, Jamie P; Foster, Christopher W; Kapur, Nikil; Banks, Craig E; Sutcliffe, Oliver B

    2015-09-21

    The global increase in the production and abuse of cathinone-derived New Psychoactive Substances (NPSs) has developed the requirement for rapid, selective and sensitive protocols for their separation and detection. Electrochemical sensing of these compounds has been demonstrated to be an effective method for the in-field detection of these substances, either in their pure form or in the presence of common adulterants, however, the technique is limited in its ability to discriminate between structurally related cathinone-derivatives (for example: (±)-4′-methylmethcathinone (4-MMC, 2a) and (±)-4′-methyl-N-ethylmethcathinone (4-MEC, 2b) when they are both present in a mixture. In this paper we demonstrate, for the first time, the combination of HPLC-UV with amperometric detection (HPLC-AD) for the qualitative and quantitative analysis of 4-MMC and 4-MEC using either a commercially available impinging jet (LC-FC-A) or custom-made iCell channel (LC-FC-B) flow-cell system incorporating embedded graphite screen-printed macroelectrodes. The protocol offers a cost-effective, reproducible and reliable sensor platform for the simultaneous HPLC-UV and amperometric detection of the target analytes. The two systems have similar limits of detection, in terms of amperometric detection [LC-FC-A: 14.66 μg mL(-1) (2a) and 9.35 μg mL(-1) (2b); LC-FC-B: 57.92 μg mL(-1) (2a) and 26.91 μg mL(-1) (2b)], to the previously reported oxidative electrochemical protocol [39.8 μg mL(-1) (2a) and 84.2 μg mL(-1) (2b)], for two synthetic cathinones, prevalent on the recreational drugs market. Though not as sensitive as standard HPLC-UV detection, both flow cells show a good agreement, between the quantitative electroanalytical data, thereby making them suitable for the detection and quantification of 4-MMC and 4-MEC, either in their pure form or within complex mixtures. Additionally, the simultaneous HPLC-UV and amperometric detection protocol detailed herein shows a marked improvement

  16. Amperometric detection of carbohydrates and thiols by using a glassy carbon electrode coated with Co oxide/multi-wall carbon nanotubes catalytic system.

    Science.gov (United States)

    Buratti, Susanna; Brunetti, Barbara; Mannino, Saverio

    2008-07-15

    A glassy carbon electrode coated with cobalt oxide/multi-wall carbon nanotubes (MWCNT) system was used for the detection of carbohydrates and thiols. The modification of the glassy carbon electrode increased the anodic current response of these organic compounds and decreased their overvoltage. The amperometric responses were extremely stable with no loss of sensitivity over many days of storage. Such attractive performance characteristics indicate great promise for using this new catalytic system for monitoring in fast and simple way compounds of great interest for food industry, biotechnology and clinical diagnostics.

  17. Development of an Analytical Protocol for Determination of Cyanide in Human Biological Samples Based on Application of Ion Chromatography with Pulsed Amperometric Detection

    OpenAIRE

    Jaszczak, Ewa; Ruman, Marek; Narkowicz, Sylwia; Namieśnik, Jacek; Polkowska, Żaneta

    2017-01-01

    A simple and accurate ion chromatography (IC) method with pulsed amperometric detection (PAD) was proposed for the determination of cyanide ion in urine, sweat, and saliva samples. The sample pretreatment relies on alkaline digestion and application of Dionex OnGuard II H cartridge. Under the optimized conditions, the method showed good linearity in the range of 1–100 μg/L for urine, 5–100 μg/L for saliva, and 3–100 μg/L for sweat samples with determination coefficients (R) > 0.992. Low detec...

  18. Complexing of heavy metals with DNA and new bioaffinity method of their determination based on amperometric DNA-based biosensor.

    Science.gov (United States)

    Babkina, S S; Ulakhovich, N A

    2005-09-01

    The immobilized single-stranded DNA (ssIDNA) has been found to be a very effective biospecific analytical reagent when used in a newly developed bioaffinity method of the determination of heavy metals based on the amperometric DNA-based biosensor. This has been concluded from the comparative study of the complexing of heavy metals with double-stranded DNA, single-stranded DNA, and ssIDNA, using Fe(III) and Cu(II) as a model (metal/nucleotide ratio and stability constants are maximum for ssIDNA), from the study of adsorption of Fe(III), Cu(II), Pb(II), and Cd(II) on nitrocellulose membranes, containing single-stranded DNA, and from the determination of their binding constants with ssIDNA. According to these data, the chosen heavy metals can be lined up in a series of binding strengths with ssIDNA: Cu(II) > Pb(II) > Fe(III) > Cd(II). The method of the determination of heavy metals is based on biospecific preconcentration of metal ions on the biosensor followed by the destruction of DNA-metal complexes with ethylenediaminetetraacetate and voltammogram recording has been proposed. The lower detection limits are 4.0 x 10(-11), 1.0 x 10(-10), 1.0 x 10(-9), and 5.0 x 10(-9) M for Cu(II), Pb(II), Cd(II), and Fe(III), respectively. The heavy metals have been assayed in multicomponent environmental and biological systems such as natural and drinking water, milk, and blood serum samples.

  19. Determination of total creatine kinase activity in blood serum using an amperometric biosensor based on glucose oxidase and hexokinase.

    Science.gov (United States)

    Kucherenko, I S; Soldatkin, O O; Lagarde, F; Jaffrezic-Renault, N; Dzyadevych, S V; Soldatkin, A P

    2015-11-01

    Creatine kinase (CK: adenosine-5-triphosphate-creatine phosphotransferase) is an important enzyme of muscle cells; the presence of a large amount of the enzyme in blood serum is a biomarker of muscular injuries, such as acute myocardial infarction. This work describes a bi-enzyme (glucose oxidase and hexokinase based) biosensor for rapid and convenient determination of CK activity by measuring the rate of ATP production by this enzyme. Simultaneously the biosensor determines glucose concentration in the sample. Platinum disk electrodes were used as amperometric transducers. Glucose oxidase and hexokinase were co-immobilized via cross-linking with BSA by glutaraldehyde and served as a biorecognition element of the biosensor. The biosensor work at different concentrations of CK substrates (ADP and creatine phosphate) was investigated; optimal concentration of ADP was 1mM, and creatine phosphate - 10 mM. The reproducibility of the biosensor responses to glucose, ATP and CK during a day was tested (relative standard deviation of 15 responses to glucose was 2%, to ATP - 6%, to CK - 7-18% depending on concentration of the CK). Total time of CK analysis was 10 min. The measurements of creatine kinase in blood serum samples were carried out (at 20-fold sample dilution). Twentyfold dilution of serum samples was chosen as optimal for CK determination. The biosensor could distinguish healthy and ill people and evaluate the level of CK increase. Thus, the biosensor can be used as a test-system for CK analysis in blood serum or serve as a component of multibiosensors for determination of important blood substances. Determination of activity of other kinases by the developed biosensor is also possible for research purposes. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. A non-enzymatic amperometric hydrogen peroxide sensor based on iron nanoparticles decorated reduced graphene oxide nanocomposite.

    Science.gov (United States)

    Amanulla, Baishnisha; Palanisamy, Selvakumar; Chen, Shen-Ming; Velusamy, Vijayalakshmi; Chiu, Te-Wei; Chen, Tse-Wei; Ramaraj, Sayee Kannan

    2017-02-01

    A simple and facile green process was used for the synthesis of iron nanoparticles (FeNPs) decorated reduced graphene oxide (rGO) nanocomposite by using Ipomoea pes-tigridis leaf extract as a reducing and stabilizing agent. The as-prepared rGO/FeNPs nanocomposite was characterized by transmission electron microscopy, X-ray spectroscopy and Fourier transform infrared spectroscopy. The nanocomposite was further modified on the glassy carbon electrode and used for non-enzymatic sensing of hydrogen peroxide (H 2 O 2 ). Cyclic voltammetry results reveal that rGO/FeNPs nanocomposite has excellent electro-reduction behavior to H 2 O 2 when compared to the response of FeNPs and rGO modified electrodes. Furthermore, the nanocomposite modified electrode shows 9 and 6 folds enhanced reduction current response to H 2 O 2 than that of rGO and FeNPs modified electrodes. Amperometric method was further used to quantify the H 2 O 2 using rGO/FeNPs nanocomposite, and the response was linear over the concentration ranging from 0.1μM to 2.15mM. The detection limit and sensitivity of the sensor were estimated as 0.056μM and 0.2085μAμM -1 cm -2 , respectively. The fabricated sensor also utilized for detection of H 2 O 2 in the presence of potentially active interfering species, and found high selectivity towards H 2 O 2 . Copyright © 2016 Elsevier Inc. All rights reserved.

  1. Pulsed amperometric detection at glassy carbon electrodes: A new waveform for sensitive and reproducible determination of electroactive compounds.

    Science.gov (United States)

    Nardiello, Donatella; Palermo, Carmen; Natale, Anna; Quinto, Maurizio; Centonze, Diego

    2015-09-24

    In this work, the application of a new pulsed amperometric detection (PAD) waveform at a glassy carbon electrode, operating in typical chromatographic mobile phases, is proposed for the sensitive and reproducible determination of arylethanolaminic and phenolic moiety based compounds (e.g. beta-agonists and polyphenols). Preliminary experiments by cyclic voltammetry were carried out to investigate the electrochemical behaviour and to select the detection and cleaning electrode potentials. The proposed potential-time profile was designed to prevent the carbon electrode fouling under repeated analyses, thus ensuring a reproducible and sensitive quantitative determination, without the need of any mechanical or chemical electrode cleaning procedure. The waveform electrochemical parameters, including detection and delay times, were optimized in terms of sensitivity, limit of detection and response stability. The optimized waveform allowed the sensitive and stable detection of model compounds, such as clenbuterol and caffeic acid, that showed detection limits of 0.1 μg L(-1) and 14 μg L(-1), quantification limits of 0.4 μg L(-1) and 46 μg L(-1), and linearity up to 100 μg L(-1) (r = 0.9993) and 10 mg L(-1) (r = 0.9998), respectively. Similar results were obtained for other compounds of the same classes, with precision values under repeatability conditions ranging from 3.0 to 5.9%. The proposed method can be then considered as an excellent alternative to the post-column detection of beta-agonists, phenols and polyphenols. Copyright © 2015 Elsevier B.V. All rights reserved.

  2. A green synthetic strategy of nickel hexacyanoferrate nanoparticals supported on the graphene substrate and its non-enzymatic amperometric sensing application

    Energy Technology Data Exchange (ETDEWEB)

    Xue, Zhonghua, E-mail: xzh@nwnu.edu.cn [Key Laboratory of Bioelectrochemistry & Environmental Analysis of Gansu Province, College of Chemistry & Chemical Engineering, Northwest Normal University, Lanzhou 730070 (China); He, Nan [Key Laboratory of Bioelectrochemistry & Environmental Analysis of Gansu Province, College of Chemistry & Chemical Engineering, Northwest Normal University, Lanzhou 730070 (China); Rao, Honghong [College of Chemistry and Chemical Engineering, Lanzhou City University, Lanzhou, 730070 (China); Hu, Chenxian; Wang, Xiaofen; Wang, Hui; Liu, Xiuhui [Key Laboratory of Bioelectrochemistry & Environmental Analysis of Gansu Province, College of Chemistry & Chemical Engineering, Northwest Normal University, Lanzhou 730070 (China); Lu, Xiaoquan, E-mail: luxq@nwnu.edu.cn [Key Laboratory of Bioelectrochemistry & Environmental Analysis of Gansu Province, College of Chemistry & Chemical Engineering, Northwest Normal University, Lanzhou 730070 (China)

    2017-02-28

    Highlights: • A sensitive non-enzymatic glucose sensor was explored by using a facile and green strategy. • Well dispersed and uniform NiHCF nanoparticles can be effectively produced by the introduction of electrochemical reduction graphene oxide films. • Metal hexacyanoferrate as a potential electron mediator was proposed and applied into non-enzymatic sensing. - Abstract: Rapid glucose detection is a key requirement for both diagnosis and treatment of diabetes. A facile and green strategy to achieve spherical-shaped nickel hexacyanoferrate (NiHCF) nanoparticals supported on electrochemical reduction graphene oxide by using electrochemical cyclic voltammetry is explored. As a sensing substrate, electrochemical reduction graphene oxide deposited on a glassy carbon electrode surface exhibited obvious positive effect on the electrodeposition of NiHCF nanoparticals with spherical structure and thus effectively improved the electrical conductivity and electrochemical sensing of the proposed amperometric sensor. Proof-concept experiments demonstrated that the proposed nanocomposites modified electrode exhibited excellent sensitivity toward glucose oxidation as well as with a satisfying detection limit of 0.11 μM. More importantly, we also explore that as a simple, green and facile method, electrochemical technology can be employed and provide a new strategy for developing GO and metal hexacyanoferrate based amperometric sensing platform toward glucose and other biomolecules.

  3. Layer-by-Layer Self-Assembling Gold Nanorods and Glucose Oxidase onto Carbon Nanotubes Functionalized Sol-Gel Matrix for an Amperometric Glucose Biosensor

    Directory of Open Access Journals (Sweden)

    Baoyan Wu

    2015-09-01

    Full Text Available A novel amperometric glucose biosensor was fabricated by layer-by-layer self-assembly of gold nanorods (AuNRs and glucose oxidase (GOD onto single-walled carbon nanotubes (SWCNTs-functionalized three-dimensional sol-gel matrix. A thiolated aqueous silica sol containing SWCNTs was first assembled on the surface of a cleaned Au electrode, and then the alternate self-assembly of AuNRs and GOD were repeated to assemble multilayer films of AuNRs-GOD onto SWCNTs-functionalized silica gel for optimizing the biosensor. Among the resulting glucose biosensors, the four layers of AuNRs-GOD-modified electrode showed the best performance. The sol-SWCNTs-(AuNRs- GOD4/Au biosensor exhibited a good linear range of 0.01–8 mM glucose, high sensitivity of 1.08 μA/mM, and fast amperometric response within 4 s. The good performance of the proposed glucose biosensor could be mainly attributed to the advantages of the three-dimensional sol-gel matrix and stereo self-assembly films, and the natural features of one-dimensional nanostructure SWCNTs and AuNRs. This study may provide a new facile way to fabricate the enzyme-based biosensor with high performance.

  4. Layer-by-Layer Self-Assembling Gold Nanorods and Glucose Oxidase onto Carbon Nanotubes Functionalized Sol-Gel Matrix for an Amperometric Glucose Biosensor.

    Science.gov (United States)

    Wu, Baoyan; Hou, Shihua; Miao, Zhiying; Zhang, Cong; Ji, Yanhong

    2015-09-18

    A novel amperometric glucose biosensor was fabricated by layer-by-layer self-assembly of gold nanorods (AuNRs) and glucose oxidase (GOD) onto single-walled carbon nanotubes (SWCNTs)-functionalized three-dimensional sol-gel matrix. A thiolated aqueous silica sol containing SWCNTs was first assembled on the surface of a cleaned Au electrode, and then the alternate self-assembly of AuNRs and GOD were repeated to assemble multilayer films of AuNRs-GOD onto SWCNTs-functionalized silica gel for optimizing the biosensor. Among the resulting glucose biosensors, the four layers of AuNRs-GOD-modified electrode showed the best performance. The sol-SWCNTs-(AuNRs- GOD)₄/Au biosensor exhibited a good linear range of 0.01-8 mM glucose, high sensitivity of 1.08 μA/mM, and fast amperometric response within 4 s. The good performance of the proposed glucose biosensor could be mainly attributed to the advantages of the three-dimensional sol-gel matrix and stereo self-assembly films, and the natural features of one-dimensional nanostructure SWCNTs and AuNRs. This study may provide a new facile way to fabricate the enzyme-based biosensor with high performance.

  5. Investigation of the interaction between Tc85-11 protein and antibody anti-T. cruzi by AFM and amperometric measurements

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira, A.A.P. [UNESP, Institute of Chemistry, CP 355, 14801-970 Araraquara, SP (Brazil); Colli, W. [USP, Institute of Chemistry, Av. Prof. Lineu Prestes 748, 05508-900 Sao Paulo, SP (Brazil); Alves, M.J.M. [USP, Institute of Chemistry, Av. Prof. Lineu Prestes 748, 05508-900 Sao Paulo, SP (Brazil); Oliveira, D.R. [USP, Institute of Chemistry, Av. Prof. Lineu Prestes 748, 05508-900 Sao Paulo, SP (Brazil); Costa, P.I. [UNESP, Faculty of Pharmaceutical Sciences, Rodovia Araraquara/Jau Km 1, 14801-902 Araraquara, SP (Brazil); Gueell, A.G. [CBEN, University of Barcelona, Scientific Park of Barcelona, C/ Josep Samitier 1-5, 08028 Barcelona (Spain); Sanz, F. [CBEN, University of Barcelona, Scientific Park of Barcelona, C/ Josep Samitier 1-5, 08028 Barcelona (Spain); Benedetti, A.V. [UNESP, Institute of Chemistry, CP 355, 14801-970 Araraquara, SP (Brazil); Yamanaka, H. [UNESP, Institute of Chemistry, CP 355, 14801-970 Araraquara, SP (Brazil)]. E-mail: hidekoy@iq.unesp.br

    2006-07-15

    This present work reports on development of an amperometric immunosensor for the diagnosis of Chagas' disease using a specific glycoprotein of the trypomastigote surface, which belongs to the Tc85-11 protein family of Trypanosoma cruzi (T. cruzi). An atomically flat gold surface on a silicon substrate and gold screen-printed electrodes were functionalized with cystamine and later activated with glutaraldehyde (GA), which was used to form covalent bonds with the purified recombinant antigen (Tc85-11). The antigen reacts with the antibody from the serum, and the affinity reaction was monitored directly using atomic force microscopy or amperometry through a secondary antibody tagged to peroxidase (HRP). Surface imaging allowed to us to differentiate the modification steps and antigen-antibody interaction allowed to distinguish the affinity reactions. In the amperometric immunosensor, peroxidase catalyses the L{sub 2} formation in the presence of hydrogen peroxide and potassium iodide, and the reduction current intensity was measured at a given potential with screen-printed electrodes. The immunosensor was applied to sera of chagasic patients and patients having different systemic diseases.

  6. Glassy carbon electrode modified with 7,7,8,8-tetracyanoquinodimethane and graphene oxide triggered a synergistic effect: Low-potential amperometric detection of reduced glutathione.

    Science.gov (United States)

    Yuan, Baiqing; Xu, Chunying; Zhang, Renchun; Lv, Donghui; Li, Sujuan; Zhang, Daojun; Liu, Lin; Fernandez, Carlos

    2017-10-15

    A sensitive electrochemical sensor based on the synergistic effect of 7,7,8,8-tetracyanoquinodimethane (TCNQ) and graphene oxide (GO) for low-potential amperometric detection of reduced glutathione (GSH) in pH 7.2 phosphate buffer solution (PBS) has been reported. This is the first time that the combination of GO and TCNQ have been successfully employed to construct an electrochemical sensor for the detection of glutathione. The surface of the glassy carbon electrode (GCE) was modified by a drop casting using TCNQ and GO. Cyclic voltammetric measurements showed that TCNQ and GO triggered a synergistic effect and exhibited an unexpected electrocatalytic activity towards GSH oxidation, compared to GCE modified with only GO, TCNQ or TCNQ/electrochemically reduced GO. Three oxidation waves for GSH were found at -0.05, 0.1 and 0.5V, respectively. Amperometric techniques were employed to detect GSH sensitively using a GCE modified with TCNQ/GO at -0.05V. The electrochemical sensor showed a wide linear range from 0.25 to 124.3μM and 124.3μM to 1.67mM with a limit of detection of 0.15μM. The electroanalytical sensor was successfully applied towards the detection of GSH in an eye drop solution. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. A green synthetic strategy of nickel hexacyanoferrate nanoparticals supported on the graphene substrate and its non-enzymatic amperometric sensing application

    International Nuclear Information System (INIS)

    Xue, Zhonghua; He, Nan; Rao, Honghong; Hu, Chenxian; Wang, Xiaofen; Wang, Hui; Liu, Xiuhui; Lu, Xiaoquan

    2017-01-01

    Highlights: • A sensitive non-enzymatic glucose sensor was explored by using a facile and green strategy. • Well dispersed and uniform NiHCF nanoparticles can be effectively produced by the introduction of electrochemical reduction graphene oxide films. • Metal hexacyanoferrate as a potential electron mediator was proposed and applied into non-enzymatic sensing. - Abstract: Rapid glucose detection is a key requirement for both diagnosis and treatment of diabetes. A facile and green strategy to achieve spherical-shaped nickel hexacyanoferrate (NiHCF) nanoparticals supported on electrochemical reduction graphene oxide by using electrochemical cyclic voltammetry is explored. As a sensing substrate, electrochemical reduction graphene oxide deposited on a glassy carbon electrode surface exhibited obvious positive effect on the electrodeposition of NiHCF nanoparticals with spherical structure and thus effectively improved the electrical conductivity and electrochemical sensing of the proposed amperometric sensor. Proof-concept experiments demonstrated that the proposed nanocomposites modified electrode exhibited excellent sensitivity toward glucose oxidation as well as with a satisfying detection limit of 0.11 μM. More importantly, we also explore that as a simple, green and facile method, electrochemical technology can be employed and provide a new strategy for developing GO and metal hexacyanoferrate based amperometric sensing platform toward glucose and other biomolecules.

  8. An amperometric penicillin biosensor with enhanced sensitivity based on co-immobilization of carbon nanotubes, hematein, and {beta}-lactamase on glassy carbon electrode

    Energy Technology Data Exchange (ETDEWEB)

    Chen Bi; Ma Ming [Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research (Ministry of Education of China), College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha 410081 (China); Su Xiaoli, E-mail: xsu@hunnu.edu.cn [Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research (Ministry of Education of China), College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha 410081 (China)

    2010-07-26

    An amperometric penicillin biosensor with enhanced sensitivity was successfully developed by co-immobilization of multi-walled carbon nanotubes (MWCNTs), hematein, and {beta}-lactamase on glassy carbon electrode using a layer-by-layer assembly technique. Under catalysis of the immobilized enzyme, penicillin was hydrolyzed, decreasing the local pH. The pH change was monitored amperometrically with hematein as a pH-sensitive redox probe. MWCNTs were used as an electron transfer enhancer as well as an efficient immobilization matrix for the sensitivity enhancement. The effects of immobilization procedure, working potential, enzyme quantity, buffer concentration, and sample matrix were investigated. The biosensor offered a minimum detection limit of 50 nM (19 {mu}g L{sup -1}) for penicillin V, lower than those of the conventional pH change-based biosensors by more than two orders of magnitude. The electrode-to-electrode variation of the response sensitivity was 7.0% RSD.

  9. Sensitive endpoint detection for coulometric titration of microgram amounts of plutonium. Part II: Use of amperometric indication for the end point detection

    International Nuclear Information System (INIS)

    Chitnis, R.T.; Talnikar, S.G.; Thakur, V.A.

    1981-01-01

    Subsequent to the work on polarized indicator electrodes in the coulometric titration of PuO 2 2+ with electrolytically generated Fe 2+ , the possibility of applying amperometry for the endpoint detection in the same titration was explored. Earlier Moiseen et al used the amperometric indication in the coulometric titration of plutonium and have reported coefficient of variation of 0.4% for the titration of 1 mg of plutonium. The lowest amount of plutonium determined was in the range of 100 micrograms. In the present method, using similar analytical technique, the titrations of 25 micrograms and lower amounts of plutonium are reported. While titrating microgram amounts using amperometric indication, the residual currents due to the supporting electrolyte affect the titrations to a considerable extent. However, it is shown that by proper choice of the potential to be applied to the indicating electrode, the interference, due to the supporting electrolyte can be minimised. Using this technique, it is possible to titrate even a fraction of a microgram of plutonium. The precision at 0.5 microgram level is found to be about 6% and that for 5 micrograms, about 1%. (author)

  10. An amperometric H2O2 biosensor based on hemoglobin nanoparticles immobilized on to a gold electrode.

    Science.gov (United States)

    Narwal, Vinay; Yadav, Neelam; Thakur, Manisha; Pundir, Chandra S

    2017-08-31

    The nanoparticles (NPs) of hemoglobin (Hb) were prepared by desolvation method and characterized by transmission electron microscopy (TEM), UV spectroscopy and Fourier-transform IR (FTIR) spectroscopy. An amperometric H 2 O 2 biosensor was constructed by immobilizing HbNPs covalently on to a polycrystalline Au electrode (AuE). HbNPs/AuE were characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectra (EIS) before and after immobilization of HbNPs. The HbNPs/AuE showed optimum response within 2.5 s at pH 6.5 in 0.1 M sodium phosphate buffer (PB) containing 100 μM H 2 O 2 at 30°C, when operated at -0.2 V against Ag/AgCl. The HbNPs/AuE exhibited V max of 5.161 ± 0.1 μA cm -2 with apparent Michaelis-Menten constant ( K m ) of 0.1 ± 0.01 mM. The biosensor showed lower detection limit (1.0 μM), high sensitivity (129 ± 0.25 μA cm -2 mM -1 ) and wider linear range (1.0-1200 μM) for H 2 O 2 as compared with earlier biosensors. The analytical recoveries of added H 2 O 2 in serum (0.5 and 1.0 μM) were 97.77 and 98.01% respectively, within and between batch coefficients of variation (CV) were 3.16 and 3.36% respectively. There was a good correlation between sera H 2 O 2 values obtained by standard enzymic colorimetric method and the present biosensor (correlation coefficient, R 2 =0.99). The biosensor measured H 2 O 2 level in sera of apparently healthy subjects and persons suffering from diabetes type II. The HbNPs/AuE lost 10% of its initial activity after 90 days of regular use, when stored dry at 4°C. © 2017 The Author(s).

  11. Bulletin of the Chemical Society of Ethiopia - Vol 7, No 2 (1993)

    African Journals Online (AJOL)

    Flow injection spectrophotometric and amperometric determinations of ammonia with glutamate dehydrogenase reactor · EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. Ghirma Moges, Theodros Solomon, Gillis Johansson ...

  12. Determinação turbidimétrica de dipirona em fluxo utilizando um reator contendo cloreto de prata imobilizado em resina poliéster Flow injection turbidimetric determination of dipyrone using a solid-phase reactor containing silver chloride immobilized in a polyester resin

    Directory of Open Access Journals (Sweden)

    Luiz H. Marcolino-Jr.

    2005-10-01

    Full Text Available A simple flow injection procedure was developed for determining dipyrone (1-phenyl-2,3-dimethyl-4-methylaminomethano-5-pyrazolone sodium, metamizol, analgin in pharmaceutical formulations. The determination is based on the reduction of Ag+ ions to Ag0 by dipyrone. A colloidal suspension of Ag0 produced was transported by carrier solution (0.01 mol L-1 NaOH and turbidimetrically detected at 425 nm. The analytical curve for dipyrone was linear in the range from 5.0 x 10-4 to 2.5 x 10-3 mol L-1 with a correlation coefficient of 0.9990. The detection limit was 1.3 x 10-4 mol L-1 (3sigmaB/slope. The relative standard deviation for ten successive measurements was 1.8% and an analytical frequency of 45 h-1 was obtained. The recovery values from three samples ranged from 96.0 to 102%.

  13. Sistema de injeção em fluxo espectrofotométrico para monitorar peróxido de hidrogênio em processo de fotodegradação por reação foto-Fenton Flow injection spectrophotometric system for hydrogen peroxide monitoring in photo-Fenton degradation processes

    Directory of Open Access Journals (Sweden)

    Mirela C. Oliveira

    2001-04-01

    Full Text Available A flow injection spectrophotometric system was projected for monitoring hydrogen peroxide during photodegradation of organic contaminants in photo-Fenton processes (Fe2+/H2O2/UV. Sample is injected manually in a carrier stream and then receives by confluence a 0.1 mol L-1 NH4VO3 solution in 0.5 mol L-1 H2SO4 medium. The product formed shows absorption at 446 nm which is recorded as a peak with height proportional to H2O2 concentration. The performance of the proposed system was evaluated by monitoring the consumption of H2O2 during the photodegradation of dichloroacetic acid solution by foto-Fenton reaction.

  14. Determinação enzimática de dopamina em formulações farmacêuticas utilizando sistema de análise por injeção em fluxo com extrato bruto de abacate (Persea americana Enzimatic determination of dopamine in pharmaceutical formulations using a flow injection analysis system with avocado (Persea americana crude extract

    Directory of Open Access Journals (Sweden)

    Karina Omuro Lupetti

    2003-03-01

    Full Text Available In this work, a spectrophotometric flow injection analysis system using a crude extract of avocado (Persea americana as a source of polyphenol oxidase to dopamine determination was developed. The substrates and enzyme concentrations from 2.4x10-7 to 5.3x10-4 mol L-1 and 28 to 332 units mL-1 were evaluated, respectively. In addition, the FIA parameters such as sample loop (50 to 500 µL, flow rate (1.4 to 4.3 mL min-1 and reactor length (100 to 500 cm were also evaluated in a 0.1 mol L-1 phosphate buffer solution (pH 7.0. Dopamine solution concentrations were determined using 277 units mL-1 enzyme solution, 400 mL enzyme loop, 375 µL sample loop, 2.2 mL min-1 flow rate and a reactor of 350 cm. The analytical curve showed a linearity from 5.3x10-5 to 5.3x10-4 mol L-1 dopamine with a detection limit of 1.3x10-5 mol L-1. The analytical frequency was 46 h-1 and the RSD lower than 0.5% for 5.3x10-4 mol L-1 dopamine solution (n=10. A paired t-test showed that all results obtained for dopamine in commercial formulations using the proposed flow injection procedure and a spectrophotometric procedure agree at the 95% confidence level.

  15. Disposable amperometric magnetoimmunosensor for the sensitive detection of the cardiac biomarker amino-terminal pro-B-type natriuretic peptide in human serum

    Energy Technology Data Exchange (ETDEWEB)

    Esteban-Fernández de Ávila, Berta, E-mail: berta.efa@quim.ucm.es; Escamilla-Gómez, Vanessa, E-mail: vaneeg@quim.ucm.es; Campuzano, Susana, E-mail: susanacr@quim.ucm.es; Pedrero, María, E-mail: mpedrero@quim.ucm.es; Pingarrón, José M., E-mail: pingarro@quim.ucm.es

    2013-06-19

    Graphical abstract: -- Highlights: •Novel and sensitive amperometric magnetoimmunosensor for NT-proBNP detection. •Indirect competitive immunoassay onto HOOC-MBs and Au/SPEs as transducers. •Excellent analytical performance at levels clinically relevant in human serum. •Useful in clinical diagnosis and prognosis of cardiac diseases. -- Abstract: A novel amperometric magnetoimmunosensor using an indirect competitive format is developed for the sensitive detection of the amino-terminal pro-B-type natriuretic peptide (NT-proBNP). The immunosensor design involves the covalent immobilization of the antigen onto carboxylic-modified magnetic beads (HOOC-MBs) activated with N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide (EDC) and N-hydroxysulfosuccinimide (sulfo-NHS), and further incubation in a mixture solution containing variable concentrations of the antigen and a fixed concentration of an HRP-labeled detection antibody. Accordingly, the target NT-proBNP in the sample and that immobilized on the MBs compete for binding to a fixed amount of the specific HRP-labeled secondary antibody. The immunoconjugate-bearing MBs are captured by a magnet placed under the surface of a disposable gold screen-printed electrode (Au/SPE). The amperometric responses measured at –0.10 V (vs. a Ag pseudo-reference electrode), upon addition of 3,3′,5,5′-tetramethylbenzidine (TMB) as electron transfer mediator and H{sub 2}O{sub 2} as the enzyme substrate, are used to monitor the affinity reaction. The developed magnetoimmunosensor provides attractive analytical characteristics in 10-times diluted human serum samples, exhibiting a linear range of clinical usefulness (0.12–42.9 ng mL{sup −1}) and a detection limit of 0.02 ng mL{sup −1}, which can be used in clinical diagnosis of chronic heart failure in the elderly and for classifying patients at risk of death after heart transplantation. The magnetoimmunosensor was successfully applied to the analysis of spiked human serum

  16. Use of different buffers for detection and separation in determination of physio-active components in oolong tea infusion by CZE with amperometric detection.

    Science.gov (United States)

    Yang, Zhiyong; Li, Zicheng; Zhu, Jinkun; Wang, Qingjiang; He, Pingang; Fang, Yuzhi

    2010-05-01

    With a view of simultaneous determination of physio-active ingredients in oolong tea infusion: sugars, amino acids, epigallocatechin gallate and ascorbic acid, a novel CZE with amperometric detection method was studied. Operated in a wall-jet configuration, 100 mmol/L NaOH was used in detecting cell to lead the electrocatalysis oxidation behaviors of the analytes on a 300 mum diameter copper-disc electrode (working electrode), while in separating capillary, a mild alkaline running buffer consisting in a mixture of 30 mmol/L borate and 40 mmol/L phosphates charged and carried analytes to detecting end. The methodology research was performed for system stability and suitability. Under the optimal CE conditions, analytes could be separated within moderate time period. Good linearity between peak area and concentration existed over three orders of magnitude; lower RSD and LOD were achieved. The oolong tea infusion was assayed and result was satisfactory.

  17. Determination of sucralose in Splenda and a sugar-free beverage using high-performance anion-exchange chromatography with pulsed amperometric detection.

    Science.gov (United States)

    Hanko, Valoran P; Rohrer, Jeffrey S

    2004-07-14

    Sucralose is a chlorinated carbohydrate nonnutritive sweetener of food and beverage products. The determination of sucralose in food and beverages is important to ensure consistency in product quality. Sucralose was determined in two commercial products without sample preparation using high-performance anion-exchange (HPAE) chromatography coupled with pulsed amperometric detection (PAD). Sucralose was determined with a 10 min isocratic separation. To determine sucralose and other carbohydrates (e.g., dextrose) simultaneously, a gradient separation was developed. The linear range of electrochemical response extended over 3 orders of magnitude, from 0.01 (LOD) to 40 microM (16 microg/mL; 25 microL injection). High precision, high spike recovery, and method ruggedness were observed for both samples.

  18. Glassy carbon electrodes modified with composites of starburst-PAMAM dendrimers containing metal nanoparticles for amperometric detection of dopamine in urine.

    Science.gov (United States)

    Bustos, Erika Bustos; Jiménez, Ma Guadalupe García; Díaz-Sánchez, Blanca R; Juaristi, Eusebio; Chapman, Thomas W; Godínez, Luis A

    2007-06-15

    Composites of hydroxyl-terminated PAMAM dendrimers, generation 4.0 (64 peripheral OH groups) containing either Ir, Pt or Rh nanoparticles were synthesized and characterized in solution. Each one of these composites was then immobilized on a glassy carbon electrode (GC) and incorporated as an amperometric detector for dopamine in a high-performance liquid chromatograph (HPLC). Comparison of the analytical performance of the novel electrochemical detectors with a typical UV-vis optical detector for dopamine revealed that the sensitivity of the GC electrode modified with dendrimer-Rh composite is comparable to that of the spectroscopic detector, with a detection limit of 0.15muM, and is linear up to at least 1.0mM (R(2)=0.998). Furthermore, it was found that the electroanalytical approach suffers minimal matrix effects that arise in the analysis of dopamine in samples of urine.

  19. Development of an Analytical Protocol for Determination of Cyanide in Human Biological Samples Based on Application of Ion Chromatography with Pulsed Amperometric Detection.

    Science.gov (United States)

    Jaszczak, Ewa; Ruman, Marek; Narkowicz, Sylwia; Namieśnik, Jacek; Polkowska, Żaneta

    2017-01-01

    A simple and accurate ion chromatography (IC) method with pulsed amperometric detection (PAD) was proposed for the determination of cyanide ion in urine, sweat, and saliva samples. The sample pretreatment relies on alkaline digestion and application of Dionex OnGuard II H cartridge. Under the optimized conditions, the method showed good linearity in the range of 1-100  μ g/L for urine, 5-100  μ g/L for saliva, and 3-100  μ g/L for sweat samples with determination coefficients ( R ) > 0.992. Low detection limits (LODs) in the range of 1.8  μ g/L, 5.1  μ g/L, and 5.8  μ g/L for urine, saliva, and sweat samples, respectively, and good repeatability (CV < 3%, n = 3) were obtained. The proposed method has been successfully applied to the analysis of human biological samples.

  20. Development of an Analytical Protocol for Determination of Cyanide in Human Biological Samples Based on Application of Ion Chromatography with Pulsed Amperometric Detection

    Directory of Open Access Journals (Sweden)

    Ewa Jaszczak

    2017-01-01

    Full Text Available A simple and accurate ion chromatography (IC method with pulsed amperometric detection (PAD was proposed for the determination of cyanide ion in urine, sweat, and saliva samples. The sample pretreatment relies on alkaline digestion and application of Dionex OnGuard II H cartridge. Under the optimized conditions, the method showed good linearity in the range of 1–100 μg/L for urine, 5–100 μg/L for saliva, and 3–100 μg/L for sweat samples with determination coefficients (R>0.992. Low detection limits (LODs in the range of 1.8 μg/L, 5.1 μg/L, and 5.8 μg/L for urine, saliva, and sweat samples, respectively, and good repeatability (CV < 3%, n=3 were obtained. The proposed method has been successfully applied to the analysis of human biological samples.

  1. Cytosine-assisted synthesis of gold nanochains and gold nanoflowers for the construction of a microperoxidase-11 based amperometric biosensor for hydrogen peroxide

    International Nuclear Information System (INIS)

    Zhang, Qian-Li; Zhou, Dan-Ling; Wang, Ai-Jun; Qin, Su-Fang; Feng, Jiu-Ju; Li, Yong-Fang

    2014-01-01

    A simple method was developed for synthesis of network-like gold nanochains and gold nanoflowers in the presence of cytosine by reduction of tetrachloroauric acid with sodium borohydride and ascorbic acid, respectively. The resulting gold nanocrystals were coated with microperoxidase-11 via electrostatic interactions. Electrodes modified with protein-coated gold nanochains or nanoflowers display well-defined and quasi reversible redox peaks and enhanced high electrocatalytic activity toward the reduction of H 2 O 2 that is due to direct electron transfer to the protein. The effects were exploited for the amperometric detection of H 2 O 2 with a linear response from 0.5 μM to 0.13 mM (for the gold nanochains) and from 1.0 μM to 0.11 mM (for the gold nanoflowers), respectively. The sensor shows lower detection limit and faster response time than sensors based on the use of spherical gold nanoparticles. (author)

  2. Single-Step Incubation Determination of miRNAs in Cancer Cells Using an Amperometric Biosensor Based on Competitive Hybridization onto Magnetic Beads

    Directory of Open Access Journals (Sweden)

    Eva Vargas

    2018-03-01

    Full Text Available This work reports an amperometric biosensor for the determination of miRNA-21, a relevant oncogene. The methodology involves a competitive DNA-target miRNA hybridization assay performed on the surface of magnetic microbeads (MBs and amperometric transduction at screen-printed carbon electrodes (SPCEs. The target miRNA competes with a synthetic fluorescein isothiocyanate (FITC-modified miRNA with an identical sequence for hybridization with a biotinylated and complementary DNA probe (b-Cp immobilized on the surface of streptavidin-modified MBs (b-Cp-MBs. Upon labeling, the FITC-modified miRNA attached to the MBs with horseradish peroxidase (HRP-conjugated anti-FITC Fab fragments and magnetic capturing of the MBs onto the working electrode surface of SPCEs. The cathodic current measured at −0.20 V (versus the Ag pseudo-reference electrode was demonstrated to be inversely proportional to the concentration of the target miRNA. This convenient biosensing method provided a linear range between 0.7 and 10.0 nM and a limit of detection (LOD of 0.2 nM (5 fmol in 25 μL of sample for the synthetic target miRNA without any amplification step. An acceptable selectivity towards single-base mismatched oligonucleotides, a high storage stability of the b-Cp-MBs, and usefulness for the accurate determination of miRNA-21 in raw total RNA (RNAt extracted from breast cancer cells (MCF-7 were demonstrated.

  3. Amperometric biosensor based on prussian blue and nafion modified screen-printed electrode for screening of potential xanthine oxidase inhibitors from medicinal plants.

    Science.gov (United States)

    El Harrad, Loubna; Amine, Aziz

    2016-04-01

    A simple and sensitive amperometric biosensor was developed for the screening of potential xanthine oxidase inhibitors from medicinal plants. This biosensor was prepared by immobilization of xanthine oxidase on the surface of prussian blue modified screen-printed electrodes using nafion and glutaraldehyde. The developed biosensor showed a linear amperometric response at an applied potential of +0.05 V toward the detection of hypoxanthine from 5 μM to 45 μM with a detection limit of 0.4 μM (S/N=3) and its sensitivity was found to be 600 mA M(-1) cm(-2). In addition, the biosensor exhibited a good storage stability. The inhibition of xanthine oxidase by allopurinol was studied under the optimized conditions. The linear range of allopurinol concentration is obtained up to 2.5 μM with an estimated 50% of inhibitionI50=1.8 μM. The developed biosensor was successfully applied to the screening of xanthine oxidase inhibitors from 13 medicinal plants belonging to different families. Indeed, Moroccan people traditionally use these plants as infusion for the treatment of gout and its related symptoms. For this purpose, water extracts obtained from the infusion of these plants were used for the experiments. In this work, 13 extracts were assayed and several of them demonstrated xanthine oxidase inhibitory effect, with an inhibition greater than 50% compared to spectrophotometry measurements that only few extracts showed an inhibition greater than 50%. Copyright © 2016 Elsevier Inc. All rights reserved.

  4. New amperometric and potentiometric immunosensors based on gold nanoparticles/tris(2,2'-bipyridyl)cobalt(III) multilayer films for hepatitis B surface antigen determinations.

    Science.gov (United States)

    Tang, Dianping; Yuan, Ruo; Chai, Yaqin; Fu, Yingzi; Dai, Jianyuan; Liu, Yan; Zhong, Xia

    2005-10-15

    Two generic, fast, sensitive and novel electrochemical immunosensors have been developed. Initially, a layer of plasma-polymerized Nafion film (PPF) was deposited on the platinum electrode surface, then positively charged tris(2,2'-bipyridyl)cobalt(III) (Co(bpy)(3)(3+)) and negatively charged gold nanoparticles were assembled on the PPF-modified Pt electrode by layer-by-layer technique. Finally, hepatitis B surface antibody (HBsAb) was electrostatically adsorbed on the gold nanoparticles surface. Electrochemical behavior of the {Au/Co(bpy)(3)(3+)}(n) multilayer film-modified electrodes was studied. Cyclic voltammetry, electrochemical impedance spectroscopy (EIS) were adopted to monitor the regular growth of the multilayer films. The performance and factors influencing the performance of the resulting immunosensors were studied in detail. The multilayer film-modified immunosensor was used for hepatitis B surface antigen (HBsAg) determination via the amperometric and potentiometric immunosensor systems, and both systems provided the same linear ranges from 0.05 to 4.5 microg/mL with different detection limits for the amperometric system 0.005 microg/mL and for the potentiometric system 0.015 microg/mL. The immunosensors were used to analyse HBsAg in human serum samples. Analytical results of clinical samples show that the developed immunoassay is comparable with the enzyme-linked immunosorbent assays (ELISAs) method, implying a promising alternative approach for detecting HBsAg in the clinical diagnosis. In addition, the multilayer films also showed better stability for 1 month at least.

  5. Horseradish peroxidase-catalyzed polymerization of L-DOPA for mono-/bi-enzyme immobilization and amperometric biosensing of H2O2 and uric acid.

    Science.gov (United States)

    Dai, Mengzhen; Huang, Ting; Chao, Long; Xie, Qingji; Tan, Yueming; Chen, Chao; Meng, Wenhua

    2016-01-01

    Horseradish peroxidase (HRP)-catalyzed polymerization of L-DOPA (vs. dopamine) in the presence of H2O2 (and uricase (UOx)) was exploited to immobilize mono-/bi-enzymes for hydroquinone-mediated amperometric biosensing of H2O2 and uric acid (UA). The relevant polymeric biocomposites (PBCs) were prepared in phosphate buffer solution containing HRP and L-DOPA (or plus UOx) after adding H2O2. The mono-/bi-enzyme amperometric biosensors were prepared simply by casting some of the PBCs on Au-plated Au (Au(plate)/Au) electrodes, followed by coating with an outer-layer chitosan (CS) film for each. UV-vis spectrophotometry, scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy were used for film characterization and/or process monitoring. The HRP immobilized by enzyme catalysis well preserved its bioactivity, as confirmed by UV-vis spectrophotometry. Under optimized conditions, the monoenzyme CS/HRP-poly(L-DOPA) (PD)/Au(plate)/Au electrode potentiostated at -0.1V responded linearly to H2O2 concentration from 0.001 to 1.25mM with a sensitivity of 700μA mM(-1)cm(-2) and a limit of detection (LOD) of 0.1μM, and the bienzyme CS/UOx-HRP-PD/Au(plate)/Au electrode at -0.1V responded linearly to UA concentration from 0.001 to 0.4mM with a sensitivity of 349μA mM(-1)cm(-2) and a LOD of 0.1μM. The mono-/bi-enzyme biosensors based on biosynthesized PD performed better than many reported analogues and those based on similarly biosynthesized polydopamine. Copyright © 2015 Elsevier B.V. All rights reserved.

  6. A sensitive and selective on-line amperometric sulfite biosensor using sulfite oxidase immobilized on a magnetite-gold-folate nanocomposite modified carbon-paste electrode.

    Science.gov (United States)

    Sroysee, Wongduan; Ponlakhet, Kitayanan; Chairam, Sanoe; Jarujamrus, Purim; Amatatongchai, Maliwan

    2016-08-15

    We describe a novel amperometric sulfite biosensor, comprising a carbon-paste electrode (Fe3O4@Au-Cys-FA/CPE) modified with immobilized sulfite oxidase (SOx) on a gold-coated magnetite nanoparticle core, encased within a conjugated folic acid (FA) cysteine (Cys) shell. The biosensor electrode was fabricated using a polydimethylsiloxane (PDMS) and mineral oil mixture as binder, which also enhances the physical stability and sensitivity of the electrode. The developed biosensor displays good electrocatalytic activity toward oxidation of H2O2, which occurs by an enzymatic reaction between SOx and sulfite. The Fe3O4@Au-Cys-FA electrode exhibits good electrocatalytic activity, and has good retention of chemisorbed SOx on the electrode because of its large surface area. Sulfite was quantified using amperometric measurements from the Fe3O4@Au-Cys-FA/CPE biosensor, and using an in-house assembled flow cell at +0.35V (vs. Ag/AgCl), with a phosphate buffer carrier (0.10M, pH 7.0) at a flow rate of 0.8mLmin(-1). The system detects sulfite over the range 0.1-200mgL(-1) (r(2)=0.998), with a detection limit of 10µgL(-1) (3σ of blank). The system exhibits acceptable precision (%R.S.D.=3.1%), rapid sample throughput (109samplesh(-1)), and good stability (2w). The developed biosensor shows satisfactory tolerance to potential interferences, such as sugars, anions, ascorbic acid, and ethanol. We applied the developed method to the determination of sulfite content in wines and pickled food extracts, and our results are in good agreement with those obtained by the standard iodometric method. Copyright © 2016 Elsevier B.V. All rights reserved.

  7. Author Details

    African Journals Online (AJOL)

    Abstract PDF · Vol 8, No 2 (1994) - Articles Flow injection determinations of glucose and adenosine-5'¬-triphosphate (ATP) based on a packed-bed glucokinase reactor. Abstract PDF · Vol 7, No 2 (1993) - Articles Flow injection spectrophotometric and amperometric determinations of ammonia with glutamate dehydrogenase ...

  8. Biossensores amperométricos para determinação de compostos fenólicos em amostras de interesse ambiental Amperometric biosensors for phenolic compounds determination in the environmental interess samples

    Directory of Open Access Journals (Sweden)

    Simone Soares Rosatto

    2001-02-01

    Full Text Available Phenols are widely used in many areas and commonly found as industrial by-products. A great number of agricultural and industrial activities realise phenolic compounds in the environmental. Waste phenols are produced mainly by the wood-pulp industry and during production of synthetic polymers, drugs, plastics, dyes, pesticides and others. Phenols are also released into the environmental by the degradation of pesticides with phenolic skeleton. The phenols level control is very important for the environmental protection. Amperometric biosensor has shown the feasibility to complement laboratory-based analytical methods for the determination of phenolic compounds, providing alternatives to conventional methods which have many disadvantages. This brief review considers the evolution of an approach to amperometric measurement using the catalytic properties of some enzymes for phenolic compounds monitoring.

  9. Carbon nanotubes enhanced the lead toxicity on the freshwater fish

    International Nuclear Information System (INIS)

    Martinez, D S T; Alves, O L; Barbieri, E

    2013-01-01

    Carbon nanotubes are promising nanostructures for many applications in materials industry and biotechnology. However, it is mandatory to evaluate their toxicity and environmental implications. We evaluated nitric acid treated multiwalled carbon nanotubes (HNO 3 -MWCNT) toxicity in Nile tilapia (Oreochromis niloticus) and also the lead (Pb) toxicity modulation after the nanotube interaction. Industrial grade multiwalled carbon nanotubes [Ctube 100, CNT Co. Ltd] were treated with 9M HNO 3 for 12h at 150°C to generate oxygenated groups on the nanotube surface, to improve water dispersion and heavy metal interaction. The HNO 3 -treated multiwalled carbon nanotubes were physico-chemically characterized by several techniques [e.g. TEM, FE-SEM, TGA, ζ-potential and Raman spectroscopy]. HNO 3 -MWCNT did not show toxicity on Nile tilapia when the concentration ranged from 0.1 to 3.0 mg/L, and the maximum exposure time was 96h. After 24, 48, 72 and 96h the LC50 values of Pb were 1.65, 1.32, 1.10 and 0.99 mg/L, respectively. To evaluate the Pb-nanotube interaction influence on the ecotoxicity, we submitted the Nile tilapia to different concentrations of Pb mixed with a non-toxic concentration of HNO 3 -MWCNT (1.0 mg/L). After 24, 48, 72, 96 h the LC50 values of Pb plus nanotubes were: 0.32, 0.25, 0.20, 0.18 mg/L, respectively. These values showed a synergistic effect after Pb-nanotube interaction since Pb toxicity increased over five times. X-ray energy dispersive spectroscopy (EDS) was used to confirm lead adsorption on the carbon nanotube oxidized surface. The exposure of Nile tilapia to Pb plus HNO 3 -MWCNT caused both oxygen consumption and ammonium excretion decrease, when compared to the control. Finally, our results show that carbon nanotubes interact with classical pollutants drawing attention to the environmental implications.

  10. Water desalination using carbon-nanotube-enhanced membrane distillation.

    Science.gov (United States)

    Gethard, Ken; Sae-Khow, Ornthida; Mitra, Somenath

    2011-02-01

    Carbon nanotube (CNT) enhanced membrane distillation is presented for water desalination. It is demonstrated that the immobilization of the CNTs in the pores of a hydrophobic membrane favorably alters the water-membrane interactions to promote vapor permeability while preventing liquid penetration into the membrane pores. For a salt concentration of 34 000 mg L(-1) and at 80 °C, the nanotube incorporation led to 1.85 and 15 times increase in flux and salt reduction, respectively.

  11. Self Assembled Carbon Nanotube Enhanced Ultracapacitors, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The objective of this NASA STTR program is to develop single wall carbon nanotube (SWCNT) based ultracapacitors for energy storage devices (ESD) application, using...

  12. Determinação espectrofotométrica de vitamina B2 (riboflavina em formulações farmacêuticas empregando sistema de análises por injeção em fluxo Spectrophotometric determination of vitamin B2 (riboflavin in pharmaceutical formulations using flow injection analysis

    Directory of Open Access Journals (Sweden)

    Clezio Aniceto

    2000-10-01

    Full Text Available A flow injection spectrophotometric procedure exploiting merging zones is proposed for determining vitamin B2 (riboflavin in pharmaceutical preparations. The determination is based on the red-colored complex formation between vitamin B2 and silver(I which was measured at 520 nm. Vitamin B2 was determined in four pharmaceutical preparations in the 1.0 to 50.0 mg L-1 concentration range, with a detection limit of 0.5 mg L-1. The recovery from three samples ranged from 98.0 to 104.0 %. The analytical frequency was 42 h-1 and r.s.d. were lower than 1% for solutions containing 10.0, 30.0 and 50.0 mg L-1 vitamin B2 (n= 10. The results obtained in commercial formulations using the FIA procedure were in good agreement with those obtained by using a conventional fluorimetric procedure (r=0.9998 and also with the label values (r= 0.9997.

  13. Emprego de nebulizador pneumático de ICP-MS como câmara de diluição em sistemas de injeção em fluxo para determinações multielementares Pneumatic nebulizer as a dilution chamber in a flow-injection system for multielement analysis by ICP-MS

    Directory of Open Access Journals (Sweden)

    José Anchieta Gomes Neto

    1998-07-01

    Full Text Available An automatic dispenser based on a flow-injection system used to introduce sample and analytical solution into an inductively coupled plasma mass spectrometer through a spray chamber is proposed. Analytical curves were constructed after the injection of 20 to 750 µL aliquots of a multielement standard solution (20.0 µg L-1 in Li, Be, Al, V, Cr, Mn, Ni, Co, Cu, Zn, As, Se, Sr, Ag, Cd, Ba, Tl, Pb and the acquisition of the integrated transient signals. The linear concentration range could be extended to ca. five decades. The performance of the system was checked by analyzing a NIST 1643d reference material. Accuracy could be improved by the proper selection of the injected volume. Besides good precision (r.s.d. < 2%, the results obtained with the proposed procedure were closer to the certified values of the reference material than those obtained by direct aspiration or by injecting 125 µL of several analytical solutions and samples.

  14. Determinação espectrofotométrica de alumínio em concentrados salinos utilizados em hemodiálise empregando pré-concentração em fluxo Spectrophotometric aluminium determination in high salts concentrations solution used in hemodyalisis emploing preconcentration in flow injection

    Directory of Open Access Journals (Sweden)

    Maria do Socorro Silva Pereira

    2002-11-01

    Full Text Available An automatic flow injection procedure for spectrophotometric aluminium determination in purified water and solutions containing high salts concentrations used for hemodyalisis treatment was developed. The method was base on reaction of Al3+ with cianine eriochrome R (ECR after preconcentration using the AG50W-X8 cationic-exchange resin. Elution was carried out using a 1 % (m/v calcium chloride solution. The manifold comprised an automatic proporcional injector controlled by a computer equipped with an eletronic interface and software written in QuicBASIC 4.5 with facilities to control the injector and perform data acquisition. Samples with concentration ranging from 4.96 to 19.90 µg L-1 Al were analyzed and recoveries between 88 and 113% were obtained by using the standard addition method. Other profitable analytical characteristics such as a relative standard deviation 1.3 % (n = 10 for a typical sample 14.5 µg L-1 Al, a linear response ranging up to 60.0 µg L-1Al, and a sampling throughput of 10 determinations per hour were achieved. A detection limit of 4.2 µg L-1 Al was estimated as suggested by IUPAC.

  15. Determination of nitrate in water by flow-injection analysis

    Czech Academy of Sciences Publication Activity Database

    Mikuška, Pavel; Večeřa, Zbyněk

    2001-01-01

    Roč. 8, č. 1 (2001), s. 115-120 ISSN 1231-7098 R&D Projects: GA ČR GA203/98/0943 Grant - others:COPERNICUS(BE) SUB-AERO EVK2-1999-000327 Institutional research plan: CEZ:AV0Z4031919 Keywords : nitrate * chemiluminescence * water Subject RIV: CB - Analytical Chemistry, Separation

  16. Combination of Flow Injection and Electrothermal Atomic Absorption Spectrometry

    DEFF Research Database (Denmark)

    Hansen, Elo Harald; Nielsen, Steffen

    1999-01-01

    The paper discusses the advantages gained by exploiting this combination, FI-ETAAS. Emphasis is placed on illlustrating various avenues to perform on-line preconcentration of metal ions in order to obtain very low limits of detection of the measurand, and ways and means to enhance the selectivity...

  17. Principles and Applications of Flow Injection Analysis in Biosensors

    DEFF Research Database (Denmark)

    Hansen, Elo Harald

    1996-01-01

    In practical applications biosensors are often forced to operate under less than optimal conditions. Because of their construction, and the physical processes and chemical reactions involved in their operation, compromise conditions are frequently required to synchronize all events taking place. ...

  18. Fast fluorometric flow injection analysis of formaldehyde in atmospheric water

    Energy Technology Data Exchange (ETDEWEB)

    Dong, S.; Dasgupta, P.K.

    1987-06-01

    Formaldehyde can be determined in aqueous solution at a rate of 45 samples/h with a small sample requirement (100 ..mu..L). The fluorescence of 3,5-diacetyl-1,4-dihydrolutidine formed upon reaction of formaldehyde with ammonium acetate and 2,4-pentanedione (25 s, 95 /sup 0/C) is monitored with a filter fluorometer. The detection limit is 0.1 ..mu..M (3 ..mu..g/L) or 10 pmol of HCHO. The response is linear up to 3.3 ..mu..M (100 ..mu..g/L), the departure from linearity at 0.33 mM is 21%, but high levels are satisfactorily determined with a second-order calibration equation. Interference from S(IV) has been investigated in detail and completely eliminated by addition of H/sub 2/O/sub 2/ before rendering the sample alkaline. There are no effects from commonly occurring metal ions and anions; the method is very selective to formaldehyde compared to other carbonyl compounds. A S(IV)-containing preservative has been formulated for the stabilization of low concentrations of HCHO. Results are presented for fogwater samples. 8 figures, 41 references.

  19. Partially hydrolyzed guar gum characterization and sensitive quantification in food matrices by high performance anion exchange chromatography with pulsed amperometric detection--validation using accuracy profile.

    Science.gov (United States)

    Mercier, G; Campargue, C

    2012-11-02

    Interest concerning functional ingredients and especially dietary fibres has been growing in recent years. At the same time, the variety of ingredient accepted as dietary fibres and their mixing at low level in complex matrices have considerably complicated their quantitative analysis by approved AOAC methods. These reasons have led to the specific development of an innovative analytical method performed by high-performance anion-exchange chromatography (HPAEC) with pulsed amperometric detection (PAD) to detect and quantify partially hydrolyzed guar gum (PHGG) in fruit preparation and dairy matrices. The analytical methodology was divided in two steps which could be deployed separately or in conjunction. The first, consists in a complete characterization of PHGG by size exclusion chromatography (SEC) with multi-angle light scattering and refractive index detection and HPAEC-PAD to determine its physico-chemical properties and galactomannans content, and the second step is the development of a new HPAEC-PAD method for PHGG direct quantification in complex matrices (dairy product). Validation in terms of detection and quantification limits, linearity of the analytical range, average accuracy (recovery, trueness) and average uncertainty were statistically carried out with accuracy profile. Overall, this new chromatographic method has considerably improved the possibility to quantify without fractionation treatment, low level of dietary fibres emerging from specific galactomannans, in complex matrices and many foodstuffs. Copyright © 2012 Elsevier B.V. All rights reserved.

  20. Amperometric biosensor based on denatured DNA for the study of heavy metals complexing with DNA and their determination in biological, water and food samples.

    Science.gov (United States)

    Babkina, S S; Ulakhovich, N A

    2004-06-01

    Amperometric biosensor (BS) has been elaborated based on the stationary mercury-film electrode (SMFE) with silver support and cellulose nitrate (CN) membrane containing immobilized single-stranded DNA (ssIDNA). The sorption isotherms and ssDNA-heavy metal binding constants have been obtained with the BS. According to these data, the chosen heavy metals form the following series of binding strength with ssIDNA: Pb(II)>Fe(III)>Cd(II). It has been found that upon the competitive adsorption, there exists practically simultaneous sorption of different ions at ssIDNA containing membrane. The method of the determination of heavy metals based on preconcentration of metal ions on the BS followed by the destruction of DNA-metal complexes with ethylenediamine tetraacetate (EDTA) and voltammogram recording has been proposed. The lower limits of detectable contents are 1.0x10(-10), 1.0x10(-9) and 1.0x10(-7) mol l(-1) for Pb(II), Cd(II) and Fe(III), respectively. Heavy metals have been assayed in natural and drinking water, milk and blood serum samples even under simultaneous presence with a selectivity factor of 1:10. The effect of matrix components has been estimated.