Glucose oxidase-modified carbon-felt-reactor coupled with peroxidase-modified carbon-felt-detector for amperometric flow determination of glucose

International Nuclear Information System (INIS)

Wang Yue; Hasebe, Yasushi

2012-01-01

Glucose oxidase (GOx) and horseradish peroxidase (HRP) were covalently immobilized on a porous carbon-felt (CF) by using cyanuric chloride (CC) as a linking reagent. The resulting GOx-modified-CF (GOx-ccCF) was used as column-type enzyme reactor and placed on upstream of the HRP-ccCF-based H 2 O 2 flow-detector to fabricate amperometric flow-biosensor for glucose. Sensor setting conditions and the operational conditions were optimized, and the analytical performance characteristics of the resulting flow-biosensor were evaluated. The chemical modification of the GOx via CC was found to be effective to obtain larger catalytic activity as compared with the physical adsorption. Under the optimized conditions (i.e., volume ratio of the GOx-ccCF-reactor to the HRP-ccCF-detector is 1.0; applied potential is − 0.12 V vs. Ag/AgCl; carrier pH is 6.5; and carrier flow rate is 4.3 ml/min), highly selective and quite reproducible peak current responses toward glucose were obtained: the RSD for 30 consecutive injections of 3 mM glucose was 1.04%, and no serious interferences were observed for fructose, ethanol, uric acid, urea and tartaric acid for the amperometric measurements of glucose. The magnitude of the cathodic peak currents for glucose was linear up to 5 mM (sensitivity, 6.38 ± 0.32 μA/μM) with the limit detection of 9.4 μM (S/N = 3, noise level, 20 nA). The present GOx-ccCF-reactor and HRP-ccCF-detector-coupled flow-glucose biosensor was utilized for the determination of glucose in beverages and liquors, and the analytical results by the sensor were in fairly good agreement with those by the conventional spectrophotometry. - Highlights: ► Glucose oxidase (GOx) and peroxidase (HRP) were modified on carbon-felt. ► GOx-CF reactor and HRP-CF detector-coupled flow glucose biosensor was developed. ► This flow biosensor enabled the determination of glucose in beverages and liquors.

Glucose oxidase-modified carbon-felt-reactor coupled with peroxidase-modified carbon-felt-detector for amperometric flow determination of glucose

Energy Technology Data Exchange (ETDEWEB)

Wang Yue [School of Chemical Engineering, University of Science and Technology LiaoNing, 185 Qianshan Middle Road, High-tech Zone, Anshan, LiaoNing, 114501 (China); Hasebe, Yasushi, E-mail: hasebe@sit.ac.jp [Department of Life Science and Green Chemistry, Faculty of Engineering, Saitama Institute of Technology, 1690, Fusaiji, Fukaya, Saitama 369-0293 (Japan)

2012-04-01

Glucose oxidase (GOx) and horseradish peroxidase (HRP) were covalently immobilized on a porous carbon-felt (CF) by using cyanuric chloride (CC) as a linking reagent. The resulting GOx-modified-CF (GOx-ccCF) was used as column-type enzyme reactor and placed on upstream of the HRP-ccCF-based H{sub 2}O{sub 2} flow-detector to fabricate amperometric flow-biosensor for glucose. Sensor setting conditions and the operational conditions were optimized, and the analytical performance characteristics of the resulting flow-biosensor were evaluated. The chemical modification of the GOx via CC was found to be effective to obtain larger catalytic activity as compared with the physical adsorption. Under the optimized conditions (i.e., volume ratio of the GOx-ccCF-reactor to the HRP-ccCF-detector is 1.0; applied potential is - 0.12 V vs. Ag/AgCl; carrier pH is 6.5; and carrier flow rate is 4.3 ml/min), highly selective and quite reproducible peak current responses toward glucose were obtained: the RSD for 30 consecutive injections of 3 mM glucose was 1.04%, and no serious interferences were observed for fructose, ethanol, uric acid, urea and tartaric acid for the amperometric measurements of glucose. The magnitude of the cathodic peak currents for glucose was linear up to 5 mM (sensitivity, 6.38 {+-} 0.32 {mu}A/{mu}M) with the limit detection of 9.4 {mu}M (S/N = 3, noise level, 20 nA). The present GOx-ccCF-reactor and HRP-ccCF-detector-coupled flow-glucose biosensor was utilized for the determination of glucose in beverages and liquors, and the analytical results by the sensor were in fairly good agreement with those by the conventional spectrophotometry. - Highlights: Black-Right-Pointing-Pointer Glucose oxidase (GOx) and peroxidase (HRP) were modified on carbon-felt. Black-Right-Pointing-Pointer GOx-CF reactor and HRP-CF detector-coupled flow glucose biosensor was developed. Black-Right-Pointing-Pointer This flow biosensor enabled the determination of glucose in beverages and

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

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.

Analysis of total polyphenols in wines by FIA with highly stable amperometric detection using carbon nanotube-modified electrodes.

Science.gov (United States)

Arribas, Alberto Sánchez; Martínez-Fernández, Marta; Moreno, Mónica; Bermejo, Esperanza; Zapardiel, Antonio; Chicharro, Manuel

2013-02-15

The use of glassy carbon electrodes (GCEs) modified with multi-walled carbon nanotube (CNT) films for the continuous monitoring of polyphenols in flow systems has been examined. The performance of these modified electrodes was evaluated and compared to bare GCE by cyclic voltammetry experiments and by flow injection analysis (FIA) with amperometric detection monitoring the response of gallic, caffeic, ferulic and p-coumaric acids in 0.050 M acetate buffer pH 4.5 containing 100 mM NaCl. The GCE modified with CNT dispersions in polyethyleneimine (PEI) provided lower overpotentials, higher sensitivity and much higher signal stability under a dynamic regime than bare GCEs. These properties allowed the estimation of the total polyphenol content in red and white wines with a remarkable long-term stability in the measurements despite the presence of potential fouling substances in the wine matrix. In addition, the versatility of the electrochemical methodology allowed the selective estimation of the easily oxidisable polyphenol fraction as well as the total polyphenol content just by tuning the detection potential at +0.30 or 0.70 V, respectively. The significance of the electrochemical results was demonstrated through correlation studies with the results obtained with conventional spectrophotometric assays for polyphenols (Folin-Ciocalteu, absorbance at 280 nm index and colour intensity index). Copyright © 2012 Elsevier Ltd. All rights reserved.

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...

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

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.

Perfluorinated acids as ion-pairing agents in the determination of monoamine transmitters and some prominent metabolites in rat brain by high-performance liquid chromatography with amperometric detection.

Science.gov (United States)

Patthy, M; Gyenge, R

1988-09-30

The behaviour of trifluoroacetate and heptafluorobutyrate as pairing ions for the reversed-phase ion-pair separation of monoamine transmitters and related metabolites was studied. The performance of systems with the perfluorinated acids was compared with that of systems containing sodium octyl sulphonate and was found to be better in terms of peak resolution combined with total analysis time, day-to-day reproducibility and the time required for attaining initial chromatographic equilibrium. Rat brain samples were deproteinized in the acidified mobile phase, injected directly on to a high-performance liquid chromatographic column and quantitated using an amperometric detector. Sample run times were 6-8 min, at a relatively low flow-rate. The detection limits achieved are fairly uncommon with conventional bore columns. The two perfluorinated acids studied differ in the dominant mechanisms of ion-pair formation and show selectivity differences as a result.

Fast cholesterol detection using flow injection microfluidic device with functionalized carbon nanotubes based electrochemical sensor.

Science.gov (United States)

Wisitsoraat, A; Sritongkham, P; Karuwan, C; Phokharatkul, D; Maturos, T; Tuantranont, A

2010-12-15

This work reports a new cholesterol detection scheme using functionalized carbon nanotube (CNT) electrode in a polydimethylsiloxane/glass based flow injection microfluidic chip. CNTs working, silver reference and platinum counter electrode layers were fabricated on the chip by sputtering and low temperature chemical vapor deposition methods. Cholesterol oxidase prepared in polyvinyl alcohol solution was immobilized on CNTs by in-channel flow technique. Cholesterol analysis based on flow injection chronoamperometric measurement was performed in 150-μm-wide and 150-μm-deep microchannels. Fast and sensitive real-time detection was achieved with high throughput of more than 60 samples per hour and small sample volume of 15 μl. The cholesterol sensor had a linear detection range between 50 and 400 mg/dl. In addition, low cross-sensitivities toward glucose, ascorbic acid, acetaminophen and uric acid were confirmed. The proposed system is promising for clinical diagnostics of cholesterol with high speed real-time detection capability, very low sample consumption, high sensitivity, low interference and good stability. Copyright © 2010 Elsevier B.V. All rights reserved.

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.

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.

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.

Comparison between a Direct-Flow SPR Immunosensor for Ampicillin and a Competitive Conventional Amperometric Device: Analytical Features and Possible Applications to Real Samples

Science.gov (United States)

Tomassetti, Mauro; Merola, Giovanni; Martini, Elisabetta; Campanella, Luigi; Sanzò, Gabriella; Favero, Gabriele; Mazzei, Franco

2017-01-01

In this research, we developed a direct-flow surface plasmon resonance (SPR) immunosensor for ampicillin to perform direct, simple, and fast measurements of this important antibiotic. In order to better evaluate the performance, it was compared with a conventional amperometric immunosensor, working with a competitive format with the aim of finding out experimental real advantages and disadvantages of two respective methods. Results showed that certain analytical features of the new SPR immunodevice, such as the lower limit of detection (LOD) value and the width of the linear range, are poorer than those of a conventional amperometric immunosensor, which adversely affects the application to samples such as natural waters. On the other hand, the SPR immunosensor was more selective to ampicillin, and measurements were more easily and quickly attained compared to those performed with the conventional competitive immunosensor. PMID:28394296

Comparison between amperometric and true potentiometric end-point detection in the determination of water by the Karl Fischer method.

Science.gov (United States)

Cedergren, A

1974-06-01

A rapid and sensitive method using true potentiometric end-point detection has been developed and compared with the conventional amperometric method for Karl Fischer determination of water. The effect of the sulphur dioxide concentration on the shape of the titration curve is shown. By using kinetic data it was possible to calculate the course of titrations and make comparisons with those found experimentally. The results prove that the main reaction is the slow step, both in the amperometric and the potentiometric method. Results obtained in the standardization of the Karl Fischer reagent showed that the potentiometric method, including titration to a preselected potential, gave a standard deviation of 0.001(1) mg of water per ml, the amperometric method using extrapolation 0.002(4) mg of water per ml and the amperometric titration to a pre-selected diffusion current 0.004(7) mg of water per ml. Theories and results dealing with dilution effects are presented. The time of analysis was 1-1.5 min for the potentiometric and 4-5 min for the amperometric method using extrapolation.

Second-order Data by Flow Injection Analysis with Spectrophotometric Diode-array Detection and Incorporated Gel-filtration Chromatographic Column

DEFF Research Database (Denmark)

Bechmann, Iben Ellegaard

1997-01-01

A flow injection analysis (FIA) system furnished with a gel-filtration chromatographic column and with photodiode-array detection was used for the generation of second-order data. The system presented is a model system in which the analytes are blue dextran, potassium hexacyanoferrate(III) and he......A flow injection analysis (FIA) system furnished with a gel-filtration chromatographic column and with photodiode-array detection was used for the generation of second-order data. The system presented is a model system in which the analytes are blue dextran, potassium hexacyanoferrate...

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.

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.

Bienzymatic biosensor for rapid detection of aspartame by flow injection analysis.

Science.gov (United States)

Radulescu, Maria-Cristina; Bucur, Bogdan; Bucur, Madalina-Petruta; Radu, Gabriel Lucian

2014-01-09

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.

Flow injection analysis of sulphide based on its photoelectrocatalytic oxidation at poly-methylene blue modified glassy carbon electrode

International Nuclear Information System (INIS)

Dilgin, Yusuf; Canarslan, Seda; Ayyildiz, Onder; Ertek, Bensu; Nişli, Gürel

2012-01-01

A new approach for photoelectrocatalytic determination of sulphide in a flow injection analysis (FIA) system was studied using a poly-methylene blue modified glassy carbon electrode (poly-MB/GCE). Results from electrochemical measurements have revealed that poly-MB/GCE is capable of signalling electrocatalytic and photoelectrocatalytic activity towards sulphide oxidation. When the surface of poly-MB/GCE was irradiated with a light source (250 W Halogen lamp), the electrocatalytic current increased substantially. A homemade flow electrochemical cell with a suitable transparent window for the irradiation of the electrode surface was used to perform the photoelectrocatalytic determination of sulphide in FIA system. The currents obtained from the photoamperometric measurements in the FIA system at optimum conditions (carrier solution: pH 9.0 Britton Robinson buffer solution containing 0.1 M KCl; flow rate: 1.3 mL min −1 ; transmission tubing length: 10 cm; injection volume: 100 μL; and constant applied potential: +150 mV vs. Ag/AgCl/KCl sat ) were linearly correlated with the sulphide concentration. The calibration curves were obtained for sulphide concentrations in a range of 0.5–500 μM. The detection limits were found to be 0.27 and 0.15 μM for amperometric and photoamperometric methods, respectively. The proposed method was successfully applied to different wastewaters such as municipal sewage or tannery wastewater. Finally, results from the sulphide measurements by poly-MB/GCE were in good agreement with those attained using spectrophotometric method.

Microchip electrophoresis with amperometric detection for a novel determination of phenolic compounds in olive oil.

Science.gov (United States)

Godoy-Caballero, María del Pilar; Acedo-Valenzuela, María Isabel; Galeano-Díaz, Teresa; Costa-García, Agustín; Fernández-Abedul, María Teresa

2012-11-07

The relevance of the development of microchip electrophoresis applications in the field of food analysis is considered in this work. A novel method to determine important phenolic compounds in extra virgin olive oil samples using a miniaturized chemical analysis system is presented in this paper. Three interesting phenolic compounds in olive oil and fruit (tyrosol, hydroxytyrosol and oleuropein glucoside) were studied by end-channel amperometric detection using a 100 μm gold wire as working electrode in glass microchip electrophoresis. The electrochemical behavior of these compounds was studied and the medium to carry out their detection was selected (0.1 M aqueous sulfuric acid). The best conditions for the separation were achieved in sodium tetraborate (10% methanol, pH 9.50) with different concentrations for the sample and the running buffer in order to allow the sample stacking phenomenon. The injection was carried out using 600 V for 3 s and the separation voltage was set at 1000 V. The quality of the method was evaluated through its analytical figures of merit and by its performance on real extra virgin olive oil samples. Determination of these compounds was carried out using the standard addition calibration method with good recoveries.

Biosensing of glucose in flow injection analysis system based on glucose oxidase-quantum dot modified pencil graphite electrode.

Science.gov (United States)

Sağlam, Özlem; Kızılkaya, Bayram; Uysal, Hüseyin; Dilgin, Yusuf

2016-01-15

A novel amperometric glucose biosensor was proposed in flow injection analysis (FIA) system using glucose oxidase (GOD) and Quantum dot (ZnS-CdS) modified Pencil Graphite Electrode (PGE). After ZnS-CdS film was electrochemically deposited onto PGE surface, GOD was immobilized on the surface of ZnS-CdS/PGE through crosslinking with chitosan (CT). A pair of well-defined reversible redox peak of GOD was observed at GOD/CT/ZnS-CdS/PGE based on enzyme electrode by direct electron transfer between the protein and electrode. Further, obtained GOD/CT/ZnS-CdS/PGE offers a disposable, low cost, selective and sensitive electrochemical biosensing of glucose in FIA system based on the decrease of the electrocatalytic response of the reduced form of GOD to dissolved oxygen. Under optimum conditions (flow rate, 1.3mL min(-1); transmission tubing length, 10cm; injection volume, 100μL; and constant applied potential, -500mV vs. Ag/AgCl), the proposed method displayed a linear response to glucose in the range of 0.01-1.0mM with detection limit of 3.0µM. The results obtained from this study would provide the basis for further development of the biosensing using PGE based FIA systems. Copyright © 2015 Elsevier B.V. All rights reserved.

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 ...

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)

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.

A multidimensional high performance liquid chromatography method coupled with amperometric detection using a boron-doped diamond electrode for the simultaneous determination of sulfamethoxazole and trimethoprim in bovine milk.

Science.gov (United States)

Andrade, Leonardo S; de Moraes, Marcela C; Rocha-Filho, Romeu C; Fatibello-Filho, Orlando; Cass, Quezia B

2009-11-10

The development and validation of a multidimensional HPLC method using an on-line clean-up column coupled with amperometric detection employing a boron-doped diamond (BDD) electrode for the simultaneous determination of sulfamethoxazole (SMX) and trimethoprim (TMP) in bovine milk are presented. Aliquots of pre-prepared skim-milk samples were directly injected into a RAM octyl-BSA column in order to remove proteins that otherwise would interfere with milk analysis. After exclusion of the milk proteins, SMX and TMP were transferred to the analytical column (an octyl column) and the separation of the compounds from one another and from other endogenous milk components was achieved. SMX and TMP were detected amperometrically at 1.25V vs. Ag/AgCl (3.0molL(-1) KCl). Results with good linearity in the concentration ranges 50-800 and 25-400microgL(-1) for SMX and TMP, respectively, were obtained and no fouling of the BDD electrode was observed within the experimental period of several hours. The intra- and inter-assay coefficients of variation were less than 10% for both drugs and the obtained LOD values for SMX and TMP were 25.0 and 15.0microgL(-1), respectively.

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)

Amperometric sensor for detection of bisphenol A using a pencil graphite electrode modified with polyaniline nanorods and multiwalled carbon nanotubes

International Nuclear Information System (INIS)

Poorahong, S.; Thammakhet, C.; Numnuam, A.; Kanatharana, P.; Thavarungkul, P.; Limbut, W.

2012-01-01

We report on a simple and highly sensitive amperometric method for the determination of bisphenol A (BPA) using pencil graphite electrodes modified with polyaniline nanorods and multiwalled carbon nanotubes. The modified electrodes display enhanced electroactivity for the oxidation of BPA compared to the unmodified pencil graphite electrode. Under optimized conditions, the sensor has a linear response to BPA in the 1. 0 and 400 μM concentration range, with a limit of detection of 10 nM (at S/N = 3). The modified electrode also has a remarkably stable response, and up to 95 injections are possible with a relative standard deviation of 4. 2% at 100 μM of BPA. Recoveries range from 86 to 102% for boiling water spiked with BPA from four brands of baby bottles. (author)

Flow electrochemical biosensors based on enzymatic porous reactor and tubular detector of silver solid amalgam

Energy Technology Data Exchange (ETDEWEB)

Josypčuk, Bohdan, E-mail: josypcuk@jh-inst.cas.cz [J. Heyrovský Institute of Physical Chemistry of AS CR, v.v.i., Department of Biophysical Chemistry, Dolejskova 3, Prague (Czech Republic); Barek, Jiří [Charles University in Prague, Faculty of Science, University Center of Excellence UNCE “Supramolecular Chemistry”, Department of Analytical Chemistry, UNESCO Laboratory of Environmental Electrochemistry, Albertov 6, CZ-128 43 Prague 2 (Czech Republic); Josypčuk, Oksana [J. Heyrovský Institute of Physical Chemistry of AS CR, v.v.i., Department of Biophysical Chemistry, Dolejskova 3, Prague (Czech Republic); Charles University in Prague, Faculty of Science, University Center of Excellence UNCE “Supramolecular Chemistry”, Department of Analytical Chemistry, UNESCO Laboratory of Environmental Electrochemistry, Albertov 6, CZ-128 43 Prague 2 (Czech Republic)

2013-05-17

Graphical abstract: -- Highlights: •Flow amperometric enzymatic biosensor was constructed. •The biosensor is based on a reactor of a novel material – porous silver solid amalgam. •Tubular amalgam detector was used for determination of decrease of O{sub 2} concentration. •Covalent bonds amalgam−thiol−enzyme contributed to the sensor long-term stability. •LOD of glucose was 0.01 mmol L{sup −1} with RSD = 1.3% (n = 11). -- Abstract: A flow amperometric enzymatic biosensor for the determination of glucose was constructed. The biosensor consists of a flow reactor based on porous silver solid amalgam (AgSA) and a flow tubular detector based on compact AgSA. The preparation of the sensor and the determination of glucose occurred in three steps. First, a self-assembled monolayer of 11-mercaptoundecanoic acid (MUA) was formed at the porous surface of the reactor. Second, enzyme glucose oxidase (GOx) was covalently immobilized at MUA-layer using N-ethyl-N′-(3-dimethylaminopropyl) carboimide and N-hydroxysuccinimide chemistry. Finally, a decrease of oxygen concentration (directly proportional to the concentration of glucose) during enzymatic reaction was amperometrically measured on the tubular detector under flow injection conditions. The following parameters of glucose determination were optimized with respect to amperometric response: composition of the mobile phase, its concentration, the potential of detection and the flow rate. The calibration curve of glucose was linear in the concentration range of 0.02–0.80 mmol L{sup −1} with detection limit of 0.01 mmol L{sup −1}. The content of glucose in the sample of honey was determined as 35.5 ± 1.0 mass % (number of the repeated measurements n = 7; standard deviation SD = 1.2%; relative standard deviation RSD = 3.2%) which corresponds well with the declared values. The tested biosensor proved good long-term stability (77% of the current response of glucose was retained after 35 days)

Flow injection analysis in inductively coupled plasma spectrometry

International Nuclear Information System (INIS)

Rosias, Maria F.G.G.

1995-10-01

The main features of flow injection analysis (FIA) as contribution to the inductively coupled plasma (Icp) spectrometry are described. A systematic review of researches using the combined FIA-Icp and the benefits of this association are presented. Flow systems were proposed to perform on-line Icp solution management for multielemental determination by atomic emission spectrometry (Icp-AES) or mass spectrometry. The inclusion of on-line ion exchangers in flow systems for matrix separation and/or analyte preconcentration are presented. Together with those applications the new advent of instruments with facilities for multielement detection on flow injection signals are described. (author). 75 refs., 19 figs

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

Amperometric magnetoimmunoassay for the direct detection of tumor necrosis factor alpha biomarker in human serum

Energy Technology Data Exchange (ETDEWEB)

Eletxigerra, U. [Micro-NanoFabrication Unit, IK4-Tekniker, Eibar (Spain); CIC microGUNE, Arrasate-Mondragón (Spain); Martinez-Perdiguero, J. [CIC microGUNE, Arrasate-Mondragón (Spain); Merino, S. [Micro-NanoFabrication Unit, IK4-Tekniker, Eibar (Spain); CIC microGUNE, Arrasate-Mondragón (Spain); Villalonga, R.; Pingarrón, J.M. [Departamento de Química Analítica, Facultad de CC. Químicas, Universidad Complutense de Madrid, Madrid (Spain); Campuzano, S., E-mail: susanacr@quim.ucm.es [Departamento de Química Analítica, Facultad de CC. Químicas, Universidad Complutense de Madrid, Madrid (Spain)

2014-08-01

Highlights: • Electrochemical magnetoimmunosensor for tumor necrosis factor alpha (TNFα) biomarker. • Sensitive and selective detection of TNFα in undiluted serum. • LOD achieved lower than the cut-off value established for relevant illnesses. • Useful and affordable alternative to ELISAs for TNFα determination in serum. - Abstract: An amperometric immunoassay for the determination of tumor necrosis factor alpha (TNFα) protein biomarker in human serum based on the use of magnetic microbeads (MBs) and disposable screen-printed carbon electrodes (SPCEs) has been developed. The specifically modified microbeads were magnetically captured on the working electrode surface and the amperometric responses were measured at −0.20 V (vs. Ag pseudo-reference electrode), upon addition of hydroquinone (HQ) as electron transfer mediator and H{sub 2}O{sub 2} as the enzyme substrate. After a thorough optimization of the assay, extremely low limits of detection were achieved: 2.0 pg mL{sup −1} (36 fM) and 5.8 pg mL{sup −1} (105 fM) for standard solutions and spiked human serum, respectively. The simplicity, robustness and this clinically interesting LOD proved the developed TNFα immunoassay as a good contender for real clinical application.

Amperometric magnetoimmunoassay for the direct detection of tumor necrosis factor alpha biomarker in human serum

International Nuclear Information System (INIS)

Eletxigerra, U.; Martinez-Perdiguero, J.; Merino, S.; Villalonga, R.; Pingarrón, J.M.; Campuzano, S.

2014-01-01

Highlights: • Electrochemical magnetoimmunosensor for tumor necrosis factor alpha (TNFα) biomarker. • Sensitive and selective detection of TNFα in undiluted serum. • LOD achieved lower than the cut-off value established for relevant illnesses. • Useful and affordable alternative to ELISAs for TNFα determination in serum. - Abstract: An amperometric immunoassay for the determination of tumor necrosis factor alpha (TNFα) protein biomarker in human serum based on the use of magnetic microbeads (MBs) and disposable screen-printed carbon electrodes (SPCEs) has been developed. The specifically modified microbeads were magnetically captured on the working electrode surface and the amperometric responses were measured at −0.20 V (vs. Ag pseudo-reference electrode), upon addition of hydroquinone (HQ) as electron transfer mediator and H 2 O 2 as the enzyme substrate. After a thorough optimization of the assay, extremely low limits of detection were achieved: 2.0 pg mL −1 (36 fM) and 5.8 pg mL −1 (105 fM) for standard solutions and spiked human serum, respectively. The simplicity, robustness and this clinically interesting LOD proved the developed TNFα immunoassay as a good contender for real clinical application

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...... the point of sample injection/introduction to the point of detection. Hence, in FI-fAAS this feature allows not only to obtain improved repeatability but also improved accuracy, and because the wash to sample ratio is high it permits the handling of samples with elevated salt contents - which...

Remote calorimetric detection of urea via flow injection analysis.

Science.gov (United States)

Gaddes, David E; Demirel, Melik C; Reeves, W Brian; Tadigadapa, Srinivas

2015-12-07

The design and development of a calorimetric biosensing system enabling relatively high throughput sample analysis are reported. The calorimetric biosensor system consists of a thin (∼20 μm) micromachined Y-cut quartz crystal resonator (QCR) as a temperature sensor placed in close proximity to a fluidic chamber packed with an immobilized enzyme. Layer by layer enzyme immobilization of urease is demonstrated and its activity as a function of the number of layers, pH, and time has been evaluated. This configuration enables a sensing system where a transducer element is physically separated from the analyte solution of interest and is thereby free from fouling effects typically associated with biochemical reactions occuring on the sensor surface. The performance of this biosensing system is demonstrated by detection of 1-200 mM urea in phosphate buffer via a flow injection analysis (FIA) technique. Miniaturized fluidic systems were used to provide continuous flow through a reaction column. Under this configuration the biosensor has an ultimate resolution of less than 1 mM urea and showed a linear response between 0-50 mM. This work demonstrates a sensing modality in which the sensor itself is not fouled or contaminated by the solution of interest and the enzyme immobilized Kapton® fluidic reaction column can be used as a disposable cartridge. Such a system enables reuse and reliability for long term sampling measurements. Based on this concept a biosensing system is envisioned which can perform rapid measurements to detect biomarkers such as glucose, creatinine, cholesterol, urea and lactate in urine and blood continuously over extended periods of time.

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.

A multidimensional high performance liquid chromatography method coupled with amperometric detection using a boron-doped diamond electrode for the simultaneous determination of sulfamethoxazole and trimethoprim in bovine milk

Energy Technology Data Exchange (ETDEWEB)

Andrade, Leonardo S.; Moraes, Marcela C. de; Rocha-Filho, Romeu C.; Fatibello-Filho, Orlando [Departamento de Quimica, Universidade Federal de Sao Carlos, C.P. 676, 13560-970 Sao Carlos - SP (Brazil); Cass, Quezia B., E-mail: quezia@pesquisador.cnpq.br [Departamento de Quimica, Universidade Federal de Sao Carlos, C.P. 676, 13560-970 Sao Carlos - SP (Brazil)

2009-11-10

The development and validation of a multidimensional HPLC method using an on-line clean-up column coupled with amperometric detection employing a boron-doped diamond (BDD) electrode for the simultaneous determination of sulfamethoxazole (SMX) and trimethoprim (TMP) in bovine milk are presented. Aliquots of pre-prepared skim-milk samples were directly injected into a RAM octyl-BSA column in order to remove proteins that otherwise would interfere with milk analysis. After exclusion of the milk proteins, SMX and TMP were transferred to the analytical column (an octyl column) and the separation of the compounds from one another and from other endogenous milk components was achieved. SMX and TMP were detected amperometrically at 1.25 V vs. Ag/AgCl (3.0 mol L{sup -1} KCl). Results with good linearity in the concentration ranges 50-800 and 25-400 {mu}g L{sup -1} for SMX and TMP, respectively, were obtained and no fouling of the BDD electrode was observed within the experimental period of several hours. The intra- and inter-assay coefficients of variation were less than 10% for both drugs and the obtained LOD values for SMX and TMP were 25.0 and 15.0 {mu}g L{sup -1}, respectively.

A multidimensional high performance liquid chromatography method coupled with amperometric detection using a boron-doped diamond electrode for the simultaneous determination of sulfamethoxazole and trimethoprim in bovine milk

International Nuclear Information System (INIS)

Andrade, Leonardo S.; Moraes, Marcela C. de; Rocha-Filho, Romeu C.; Fatibello-Filho, Orlando; Cass, Quezia B.

2009-01-01

The development and validation of a multidimensional HPLC method using an on-line clean-up column coupled with amperometric detection employing a boron-doped diamond (BDD) electrode for the simultaneous determination of sulfamethoxazole (SMX) and trimethoprim (TMP) in bovine milk are presented. Aliquots of pre-prepared skim-milk samples were directly injected into a RAM octyl-BSA column in order to remove proteins that otherwise would interfere with milk analysis. After exclusion of the milk proteins, SMX and TMP were transferred to the analytical column (an octyl column) and the separation of the compounds from one another and from other endogenous milk components was achieved. SMX and TMP were detected amperometrically at 1.25 V vs. Ag/AgCl (3.0 mol L -1 KCl). Results with good linearity in the concentration ranges 50-800 and 25-400 μg L -1 for SMX and TMP, respectively, were obtained and no fouling of the BDD electrode was observed within the experimental period of several hours. The intra- and inter-assay coefficients of variation were less than 10% for both drugs and the obtained LOD values for SMX and TMP were 25.0 and 15.0 μg L -1 , respectively.

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

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

[Amperometric biosensor for ethanol analysis in wines and grape must during wine fermentation].

Science.gov (United States)

Shkotova, L V; Slast'ia, E A; Zhyliakova, T A; Soldatkin, O P; Schuhmann, W; Dziadevych, S V

2005-01-01

The amperometric biosensor for ethanol determination based on alcohol oxidase immobilised by the method of electrochemical polymerization has been developed. The industrial screen-printed platinum electrodes were used as transducers for creation of amperometric alcohol biosensor. Optimal conditions for electrochemical deposition of an active membrane with alcohol oxidase has been determined. Biosensors are characterised by good reproducibility and operational stability with minimal detection limit of ethanol 8 x 10(-5) M. The good correlation of results for ethanol detection in wine and during wine fermentation by using the developed amperometric biosensor with the data obtained by the standard methods was shown (r = 0.995).

The determination of levofloxacin by flow injection analysis using UV detection, potentiometry, and conductometry in pharmaceutical preparations.

Science.gov (United States)

Altiokka, G; Atkosar, Z; Can, N O

2002-10-15

A flow injection analysis (FIA) using UV detection, potentiometry and conductometry for levofloxacin (LVF) are described in this study. The best solvent system was found to consist of 0.2 M acetate buffer at pH 3 having 10% MeOH. A flow rate of 1 ml min(-1) was pumped and active material was detected at 288 nm. The detection limit (LOD) and limit of quantification (LOQ) for FIA were calculated to be 3 x 10(-7) M (S/N = 3) and 1 x 10(-7) M (S/N = 10), respectively. In the analysis of tablets, the RSD values were found to be 0.83, 0.98 and 0.99 for FIA, potentiometric and conductometric methods, respectively. Copyright 2002 Elsevier Science B.V.

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.

Magnetic detection of ferrofluid injection zones

Energy Technology Data Exchange (ETDEWEB)

Borglin, S.; Moridis, G.; Becker, A.

1998-03-01

Ferrofluids are stable colloidal suspensions of magnetic particles that can be stabilized in various carrier liquids. In this study the authors investigate the potential of ferrofluids to trace the movement and position of liquids injected in the subsurface using geophysical methods. An ability to track and monitor the movement and position of injected liquids is essential in assessing the effectiveness of the delivery system and the success of the process. Ferrofluids can also provide a significant detection and verification tool in containment technologies, where they can be injected with the barrier liquids to provide a strong signature allowing determination of the barrier geometry, extent, continuity and integrity. Finally, ferrofluids may have unique properties as tracers for detecting preferential flow features (such as fractures) in the subsurface, and thus allow the design of more effective remediation systems. In this report the authors review the results of the investigation of the potential of ferrofluids to trace the movement and position of liquids injected in the subsurface using geophysical methods. They demonstrate the feasibility of using conventional magnetometry for detecting subsurface zones of injected ferrofluids used to trace liquids injected for remediation or barrier formation. The geometrical shapes considered were a sphere, a thin disk, a rectangular horizontal slab, and a cylinder. Simple calculations based on the principles of magnetometry are made to determine the detection depths of FTs. Experiments involving spherical, cylindrical and horizontal slabs show a very good agreement between predictions and measurements.

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

Determination of Nitrite and Nitrate in Natural Waters Using Flow Injection with Spectrophotometric Detection

International Nuclear Information System (INIS)

Yaqoob, M.; Nabi, A.

2013-01-01

A simple and sensitive flow injection spectrophotometric method is reported for the room temperature determination of nitrite and nitrate based on the Griess reaction and a copperised cadmium column for reduction of nitrate. Calibration graphs were linear over the range 2 - 1000 micro g N L /sup -1/ (R2 = 0.9997 and 0.9999, n = 9) with a limit of detection (3 s.d.) of 1.0 micro g N L and relative standard deviations (n = 10) of 0.9 and 1.2% for 50 micro g N L nitrite and nitrate respectively. The sample throughput was 50 h. The effect of reagent concentrations, physical parameters (flow rate, sample volume, reaction coil and copperised cadmium column length) and the potential interferences are reported. The effect of salinity on the blank and on the determination of nitrite and nitrate are also presented. The method was applied to natural waters (rainwater, freshwater and estuarine water) and the results for nitrite + nitrate (140 - 7310 micro g N L/sup -1/) were not significantly different (95% confidence interval) from results obtained using a segmented flow analyser reference method with spectrophotometric detection. (author)

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)

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...

Fast batch injection analysis of H{sub 2}O{sub 2} using an array of Pt-modified gold microelectrodes obtained from split electronic chips

Energy Technology Data Exchange (ETDEWEB)

Pacheco, Bruno D.; Valerio, Jaqueline [Centro de Ciencias e Humanidades - Universidade Presbiteriana Mackenzie, Rua da Consolacao, 896, 01302-907 Sao Paulo, SP (Brazil); Angnes, Lucio [Departamento de Quimica Fundamental, Instituto de Quimica da USP, Av. Prof. Lineu Prestes, 748, 05508-000 Cidade Universitaria, Sao Paulo, SP (Brazil); Pedrotti, Jairo J., E-mail: jpedrotti@mackenzie.br [Centro de Ciencias e Humanidades - Universidade Presbiteriana Mackenzie, Rua da Consolacao, 896, 01302-907 Sao Paulo, SP (Brazil)

2011-06-24

Graphical abstract: Highlights: > An array of gold microelectrodes modified with Pt was used for batch injection analysis of H{sub 2}O{sub 2} in rainwater. > The microelectrode array (n = 14) was obtained from electronic chips developed for surface mounted device technology. > The analytical frequency of the method can attain 300 determinations per hour. > The volume-weighted mean concentration of H{sub 2}O{sub 2} in rainwater investigated (n = 25) was 14.2 {mu}mol L{sup -1}. - Abstract: A fast and robust analytical method for amperometric determination of hydrogen peroxide (H{sub 2}O{sub 2}) based on batch injection analysis (BIA) on an array of gold microelectrodes modified with platinum is proposed. The gold microelectrode array (n = 14) was obtained from electronic chips developed for surface mounted device technology (SMD), whose size offers advantages to adapt them in batch cells. The effect of the dispensing rate, volume injected, distance between the platinum microelectrodes and the pipette tip, as well as the volume of solution in the cell on the analytical response were evaluated. The method allows the H{sub 2}O{sub 2} amperometric determination in the concentration range from 0.8 {mu}mol L{sup -1} to 100 {mu}mol L{sup -1}. The analytical frequency can attain 300 determinations per hour and the detection limit was estimated in 0.34 {mu}mol L{sup -1} (3{sigma}). The anodic current peaks obtained after a series of 23 successive injections of 50 {mu}L of 25 {mu}mol L{sup -1} H{sub 2}O{sub 2} showed an RSD < 0.9%. To ensure the good selectivity to detect H{sub 2}O{sub 2}, its determination was performed in a differential mode, with selective destruction of the H{sub 2}O{sub 2} with catalase in 10 mmol L{sup -1} phosphate buffer solution. Practical application of the analytical procedure involved H{sub 2}O{sub 2} determination in rainwater of Sao Paulo City. A comparison of the results obtained by the proposed amperometric method with another one which

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

Improved bacteria detection by coupling magneto-immunocapture and amperometry at flow-channel microband electrodes

DEFF Research Database (Denmark)

Laczka, Olivier; Maesa, José-María; Godino, Neus

2011-01-01

This paper describes the first immunosensing system reported for the detection of bacteria combining immunomagnetic capture and amperometric detection in a one-step sandwich format, and in a microfluidic environment. Detection is based on the electrochemical monitoring of the activity of horserad......This paper describes the first immunosensing system reported for the detection of bacteria combining immunomagnetic capture and amperometric detection in a one-step sandwich format, and in a microfluidic environment. Detection is based on the electrochemical monitoring of the activity...... product is then pumped along a microchannel, where it is amperometrically detected by a set of microelectrodes. This design avoids direct contact of the biocomponents with the electrode, which lowers the risk of electrode fouling. The whole assay can be completed in 1h. The experiments performed...... with Escherichia coli evidenced a linear response for concentrations ranging 102–108cellml−1, with a limit of detection of 55cellsml−1 in PBS, without pre-enrichment steps. Furthermore, 100cellsml−1 could be detected in milk, and with negligible interference by non-target bacteria such as Pseudomonas....

Integration of amperometric sensors for microchip capillary electrophoresis application

International Nuclear Information System (INIS)

Dicorato, F; Moore, E; Glennon, J

2011-01-01

Capillary electrophoresis is a technique for the separation and analysis of chemical compounds. Techniques adopted from the microchip technology knowledge have led to recent developments of electrophoresis system with integration on microchip. Microchip Capillary Electrophoresis (μCE) systems offer a series of advantages as easy integration for Lab-on-a-chip applications, high performance, portability, speed, minimal solvent and sample requirements. A new technological challenge aims at the development of an economic modular microchip capillary electrophoresis systems using separable and independent units concerning the sensor. In this project we worked on the development of an interchangeable amperometric sensor in order to provide a solution to such electrode passivation and facilitating the use of tailored sensors for specific analyte detection besides. Fluidic chips have been machined from cyclic olefin polymer pallets (Zeonor) using a micro-injection molding machine.

Integration of amperometric sensors for microchip capillary electrophoresis application

Energy Technology Data Exchange (ETDEWEB)

Dicorato, F; Moore, E [Life Sciences Interface Group, Tyndall National Institute, Lee Maltings, Dyke Parade, Cork (Ireland); Glennon, J, E-mail: eric.moore@tyndall.ie [Chemistry Department, University College Cork, College Road, Cork (Ireland)

2011-08-17

Capillary electrophoresis is a technique for the separation and analysis of chemical compounds. Techniques adopted from the microchip technology knowledge have led to recent developments of electrophoresis system with integration on microchip. Microchip Capillary Electrophoresis ({mu}CE) systems offer a series of advantages as easy integration for Lab-on-a-chip applications, high performance, portability, speed, minimal solvent and sample requirements. A new technological challenge aims at the development of an economic modular microchip capillary electrophoresis systems using separable and independent units concerning the sensor. In this project we worked on the development of an interchangeable amperometric sensor in order to provide a solution to such electrode passivation and facilitating the use of tailored sensors for specific analyte detection besides. Fluidic chips have been machined from cyclic olefin polymer pallets (Zeonor) using a micro-injection molding machine.

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.

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...

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.

Flow injection methods for the determination of a-tocopherol with spectrophotometric detection

International Nuclear Information System (INIS)

Rishi, L.; Waseem, A.; Yaqoob, M.; Nabi, A.; Jadoon, S.

2011-01-01

The present paper describes flow injection procedures for a-tocopherol determination in pharmaceuticals and infant milk powder based on spectrophotometric detection. These two procedures are based on the reduction of iron(III) to iron(II) and of Mo(Vi) to Mo(V) by a-tocopherol and subsequent formation of iron(II)-o-phenanthroline, and phospho molybdenum complexes which were monitored at 510 and 695 nm respectively. Calibration graphs were linear over the concentration range of 0.21-43 mu g/mL for iron(III) and 0.25-10 mu g/mL for Mo(Vi) reduction methods respectively. The limits of detection (3s) of 0.05 and 0.1 mu g/mL with sample throughput of 30 and 50/h respectively were obtained. The relative standard deviations of 1.2- 3.8% (n = 4) was achieved in the concentration range studied. The developed methods were applied to pharmaceuticals and infant milk powders and the results obtained were compared with official method and no significant difference between these methods was observed at 95% confidence level. (author)

Amperometric Self-Referencing Ceramic Based Microelectrode Arrays for D-Serine Detection.

Science.gov (United States)

Campos-Beltrán, Diana; Konradsson-Geuken, Åsa; Quintero, Jorge E; Marshall, Lisa

2018-03-06

D-serine is the major D-amino acid in the mammalian central nervous system. As the dominant co-agonist of the endogenous synaptic NMDA receptor, D-serine plays a role in synaptic plasticity, learning, and memory. Alterations in D-serine are linked to neuropsychiatric disorders including schizophrenia. Thus, it is of increasing interest to monitor the concentration of D-serine in vivo as a relevant player in dynamic neuron-glia network activity. Here we present a procedure for amperometric detection of D-serine with self-referencing ceramic-based microelectrode arrays (MEAs) coated with D-amino acid oxidase from the yeast Rhodotorula gracilis (RgDAAO). We demonstrate in vitro D-serine recordings with a mean sensitivity of 8.61 ± 0.83 pA/µM to D-serine, a limit of detection (LOD) of 0.17 ± 0.01 µM, and a selectivity ratio of 80:1 or greater for D-serine over ascorbic acid (mean ± SEM; n = 12) that can be used for freely moving studies.

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 ...

Separation of human milk oligosaccharides using high-performance anion-exchange chromatography with pulsed amperometric detection

DEFF Research Database (Denmark)

Lie, Aleksander; Pedersen, Lars Haastrup

individual mothers is considerable, ranging from as few as 23 and up to 130 different oligosaccharides. HMOs are known as beneficial for infant health and development, and have received increasing attention in recent years (Bode & Jantscher-Krenn 2012). 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 on the number of charged groups in the molecule, pH and concentration of competing anions, while PAD has sensitivity...

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

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

SQL injection detection system

OpenAIRE

Vargonas, Vytautas

2017-01-01

SQL injection detection system Programmers do not always ensure security of developed systems. That is why it is important to look for solutions outside being reliant on developers. In this work SQL injection detection system is proposed. The system analyzes HTTP request parameters and detects intrusions. It is based on unsupervised machine learning. Trained by regular request data system detects outlier user parameters. Since training is not reliant on previous knowledge of SQL injections, t...

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 mecha...

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.

Novel amperometric glucose biosensor based on MXene nanocomposite

KAUST Repository

Baby, Rakhi Raghavan; Nayuk, Pranati; Xia, Chuan; Alshareef, Husam N.

2016-01-01

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.

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...

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.

Analysis of human milk oligosaccharides using high-performance anion-exchange chromatography with pulsed amperometric detection

DEFF Research Database (Denmark)

Lie, Aleksander; Pedersen, Lars Haastrup

) 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...... on the number of charged group in the molecule, pH and concentration of competing anions, while the PAD has sensitivity for carbohydrates in the pmol-range (Lee 1990). As a basis for the development and optimisation of HPAE elution methods, the parameter space was investigated in terms of eluent concentrations...

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.

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

Wireless Amperometric Neurochemical Monitoring Using an Integrated Telemetry Circuit

Science.gov (United States)

Roham, Masoud; Halpern, Jeffrey M.; Martin, Heidi B.; Chiel, Hillel J.

2015-01-01

An integrated circuit for wireless real-time monitoring of neurochemical activity in the nervous system is described. The chip is capable of conducting high-resolution amperometric measurements in four settings of the input current. The chip architecture includes a first-order ΔΣ modulator (ΔΣM) and a frequency-shift-keyed (FSK) voltage-controlled oscillator (VCO) operating near 433 MHz. It is fabricated using the AMI 0.5 μm double-poly triple-metal n-well CMOS process, and requires only one off-chip component for operation. Measured dc current resolutions of ~250 fA, ~1.5 pA, ~4.5 pA, and ~17 pA were achieved for input currents in the range of ±5, ±37, ±150, and ±600 nA, respectively. The chip has been interfaced with a diamond-coated, quartz-insulated, microneedle, tungsten electrode, and successfully recorded dopamine concentration levels as low as 0.5 μM wirelessly over a transmission distance of ~0.5 m in flow injection analysis experiments. PMID:18990633

Wireless amperometric neurochemical monitoring using an integrated telemetry circuit.

Science.gov (United States)

Roham, Masoud; Halpern, Jeffrey M; Martin, Heidi B; Chiel, Hillel J; Mohseni, Pedram

2008-11-01

An integrated circuit for wireless real-time monitoring of neurochemical activity in the nervous system is described. The chip is capable of conducting high-resolution amperometric measurements in four settings of the input current. The chip architecture includes a first-order Delta Sigma modulator (Delta Sigma M) and a frequency-shift-keyed (FSK) voltage-controlled oscillator (VCO) operating near 433 MHz. It is fabricated using the AMI 0.5 microm double-poly triple-metal n-well CMOS process, and requires only one off-chip component for operation. Measured dc current resolutions of approximately 250 fA, approximately 1.5 pA, approximately 4.5 pA, and approximately 17 pA were achieved for input currents in the range of +/-5, +/-37, +/-150, and +/-600 nA, respectively. The chip has been interfaced with a diamond-coated, quartz-insulated, microneedle, tungsten electrode, and successfully recorded dopamine concentration levels as low as 0.5 microM wirelessly over a transmission distance of approximately 0.5 m in flow injection analysis experiments.

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)

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.

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.

Science.gov (United States)

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

2016-03-01

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, and absorbance at 225 and 283 nm. Prediction rates of 100% were achieved for all data representations by partial least-squares discriminant analysis using leave-one-sample-out cross-validation. The prediction rate for the proton nuclear magnetic resonance data by partial least-squares discriminant analysis with leave-one-sample-out cross-validation was also 100%. A new validation set of data was collected by flow-injection with ultraviolet spectroscopic detection two weeks later and predicted by partial least-squares discriminant analysis models constructed by the initial data representations with no parameter changes. The classification rates were 95% with the total ultraviolet absorbance chromatograms datasets and 100% with the other three datasets. Flow-injection with ultraviolet detection and proton nuclear magnetic resonance are simple, high throughput, and low-cost methods for discrimination studies.

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.)

The impact of interpreted flow regimes during constant head injection tests on the estimated transmissivity from injection tests and difference flow logging

Energy Technology Data Exchange (ETDEWEB)

Hjerne, Calle; Ludvigsson, Jan-Erik; Harrstroem, Johan [Geosigma AB, Uppsala (Sweden)

2013-04-15

A large number of constant head injection tests were carried out in the site investigation at Forsmark using the Pipe String System, PSS3. During the original evaluation of the tests the dominating transient flow regimes during both the injection and recovery period were interpreted together with estimation of hydraulic parameters. The flow regimes represent different flow and boundary conditions during the tests. Different boreholes or borehole intervals may display different distributions of flow regimes. In some boreholes good agreement was obtained between the results of the injection tests and difference flow logging with Posiva flow log (PFL) but in other boreholes significant discrepancies were found. The main objective of this project is to study the correlation between transient flow regimes from the injection tests and other borehole features such as transmissivity, depth, geology, fracturing etc. Another subject studied is whether observed discrepancies between estimated transmissivity from difference flow logging and injection tests can be correlated to interpreted flow regimes. Finally, a detailed comparison between transient and stationary evaluation of transmissivity from the injection tests in relation to estimated transmissivity from PFL tests in corresponding sections is made. Results from previous injection tests in 5 m sections in boreholes KFM04, KFM08A and KFM10A were used. Only injection tests above the (test-specific) measurement limit regarding flow rate are included in the analyses. For all of these tests transient flow regimes were interpreted. In addition, results from difference flow logging in the corresponding 5 m test sections were used. Finally, geological data of fractures together with rock and fracture zone properties have been used in the correlations. Flow regimes interpreted from the injection period of the tests are generally used in the correlations but deviations between the interpreted flow regimes from the injection and

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...

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.

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 atom...

Detecting subsurface fluid leaks in real-time using injection and production rates

Science.gov (United States)

Singh, Harpreet; Huerta, Nicolas J.

2017-12-01

CO2 injection into geologic formations for either enhanced oil recovery or carbon storage introduces a risk for undesired fluid leakage into overlying groundwater or to the surface. Despite decades of subsurface CO2 production and injection, the technologies and methods for detecting CO2 leaks are still costly and prone to large uncertainties. This is especially true for pressure-based monitoring methods, which require the use of simplified geological and reservoir flow models to simulate the pressure behavior as well as background noise affecting pressure measurements. In this study, we propose a method to detect the time and volume of fluid leakage based on real-time measurements of well injection and production rates. The approach utilizes analogies between fluid flow and capacitance-resistance modeling. Unlike other leak detection methods (e.g. pressure-based), the proposed method does not require geological and reservoir flow models to simulate the behavior that often carry significant sources of uncertainty; therefore, with our approach the leak can be detected with greater certainty. The method can be applied to detect when a leak begins by tracking a departure in fluid production rate from the expected pattern. The method has been tuned to detect the effect of boundary conditions and fluid compressibility on leakage. To highlight the utility of this approach we use our method to detect leaks for two scenarios. The first scenario simulates a fluid leak from the storage formation into an above-zone monitoring interval. The second scenario simulates intra-reservoir migration between two compartments. We illustrate this method to detect fluid leakage in three different reservoirs with varying levels of geological and structural complexity. The proposed leakage detection method has three novelties: i) requires only readily-available data (injection and production rates), ii) accounts for fluid compressibility and boundary effects, and iii) in addition to

An Amperometric Immunosensor Based on Multi-Walled Carbon Nanotubes-Thionine-Chitosan Nanocomposite Film for Chlorpyrifos Detection

Science.gov (United States)

Sun, Xia; Cao, Yaoyao; Gong, Zhili; Wang, Xiangyou; Zhang, Yan; Gao, Jinmei

2012-01-01

In this work, a novel amperometric immunosensor based on multi-walled carbon nanotubes-thionine-chitosan (MWCNTs-THI-CHIT) nanocomposite film as electrode modified material was developed for the detection of chlorpyrifos residues. The nanocomposite film was dropped onto a glassy carbon electrode (GCE), and then the anti-chlorpyrifos monoclonal antibody was covalently immobilized onto the surface of MWCNTs-THI-CHIT/GCE using the crosslinking agent glutaraldehyde (GA). The modification procedure was characterized by using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Under the optimized conditions, a linear relationship between the relative change in peak current of different pulse voltammetry (DPV) and the logarithm of chlorpyrifos solution concentration was obtained in the range from 0.1 to 1.0 × 105 ng/mL with a detection limit of 0.046 ng/mL. The proposed chlorpyrifos immunosensor exhibited high reproducibility, stability, and good selectivity and regeneration, making it a potential alternative tool for ultrasensitive detection of chlorpyrifos residues in vegetables and fruits. PMID:23443396

Enzymatic amplification of a flow-injected thermometric enzyme-linked immunoassay for human insulin.

Science.gov (United States)

Mecklenburg, M; Lindbladh, C; Li, H; Mosbach, K; Danielsson, B

1993-08-01

A flow-injected thermometric enzyme linked immunoassay for human insulin which employs the lactate dehydrogenase/lactate oxidase (LDH/LOD) substrate recycling system for signal amplification is described. The system is composed of two columns, an immunosorbent column containing immobilized anti-insulin antibodies for sensing and a recycling column containing immobilized LDH/LOD/Catalase for detection. The effect of flow rates, conjugate concentrations, and chromatographic support material upon the sensitivity of the assay are investigated. The assay has a detection limit of 0.025 microgram/ml and a linear range from 0.05 to 2 micrograms/ml. This corresponds to a 10-fold increase in sensitivity over the unamplified system. A recombinant human insulin-proinsulin conjugate was also tested. The results show that enzymatic amplification can be employed to increase the sensitivity and reproducibility of flow injection assay-based biosensors. The implications of these results upon on-line analysis are discussed.

Amperometric biosensor for total monoamines using a glassy carbon paste electrode modified with human monoamine oxidase B and manganese dioxide particles

International Nuclear Information System (INIS)

Aigner, Maximilian; Telsnig, Dietlind; Teubl, Christian; Ortner, Astrid; Kalcher, Kurt; Macheroux, Peter; Wallner, Silvia; Edmondson, Dale

2015-01-01

We have prepared a biosensor for the determination of the total monoamine content in complex matrices by immobilizing a human monoamine oxidase B (hMAO B) on a glassy carbon paste electrode and adding manganese dioxide microparticles as the mediator. The enzyme hMAO B (expressed in Pichia pastoris and immobilized by using a dialysis membrane) catalyzes the oxidative deamination of monoamines, and this results in the formation of the corresponding aldehyde, ammonia and hydrogen peroxide. The latter was detected at pH 7.5 at a working voltage of 400 mV (vs. Ag/AgCl) by differential pulse voltammetry and amperometrically by applying flow injection analysis. Analytical parameters were established by using phenylethylamine (PEA) as a standard substrate. Peak height and concentration of PEA are linearly related in the 0.5 to 150 μg mL −1 concentration range, and the limits of detection and of quantification are 0.15 and 0.5 μg mL −1 of PEA, respectively. Substrate specificity was investigated with different monoamines including PEA, serotonin, benzylamine, dopamine, tyramine, and norepinephrine. The applicability of the biosensor was successfully tested in a commercial fish sauce that served as a complex matrix. The total monoamine content was calculated as PEA-equivalents. (author)

Amperometric biosensor based on a single antibody of dual function for rapid detection of Streptococcus agalactiae.

Science.gov (United States)

Vásquez, Gersson; Rey, Alba; Rivera, Camilo; Iregui, Carlos; Orozco, Jahir

2017-01-15

Pathogenic bacteria are responsible for several diseases in humans and in a variety of hosts. Detection of pathogenic bacteria is imperative to avoid and/or fight their potential harmful effects. This work reports on the first amperometric biosensor for the rapid detection of Streptococcus agalactiae (S. agalactiae). The biosensor relies on a single biotinylated antibody that immobilizes the bacteria on a screen-printed carbon electrode while is further linked to a streptavidin-conjugated HRP reporter. The biotinylated antibody provides selectivity to the biosensor whereas serves as an anchoring point to the reporter for further amplification of the electrochemical signal. The resultant immunosensor is simple, responds rapidly, and allows for the selective and highly sensitive quantification of S. agalactiae cells in a concentration range of 10 1 -10 7 CFUml -1 , with a detection limit of 10CFUml -1 . The approach not only enables a rapid detection and quantification of S. agalactiae in environmental samples but also opens up new opportunities for the simple fabrication of electrochemical immunosensors for different target pathogens. Copyright © 2016 Elsevier B.V. All rights reserved.

Application of Ionic Liquids in Amperometric Gas Sensors.

Science.gov (United States)

Gębicki, Jacek; Kloskowski, Adam; Chrzanowski, Wojciech; Stepnowski, Piotr; Namiesnik, Jacek

2016-01-01

This article presents an analysis of available literature data on metrological parameters of the amperometric gas sensors containing ionic liquids as an electrolyte. Four mechanism types of signal generation in amperometric sensors with ionic liquid are described. Moreover, this article describes the influence of selected physico-chemical properties of the ionic liquids on the metrological parameters of these sensors. Some metrological parameters are also compared for amperometric sensors with GDE and SPE electrodes and with ionic liquids for selected analytes.

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

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

A multisyringe flow injection method for the determination of thorium in water samples using spectrophotometric detection

International Nuclear Information System (INIS)

Guzman-Mar, J.L.; Aracely Hernandez-Ramirez; Lopez-Chuken, U.J.; Lopez-de-Alba, P.L.; Victor Cerda

2011-01-01

A fast and simple multisyringe flow injection analysis (MSFIA) method for routine determination of thorium in water samples was developed. The methodology was based on the complexation reaction of thorium with arsenazo (III) at pH 2.0. Thorium concentrations were spectrophotometrically detected at 665 nm. Under optimal conditions, Beer's law was obeyed over the range from 0.2 to 4.5 μg mL -1 thorium, a 3σ detection limit of 0.05 μg mL -1 , and a 10σ quantification limit of 0.2 μg mL -1 were obtained. The relative standard deviations (RSD, %) at 0.5, 2.5 and 4.5 μg mL -1 was 2.8, 1.5 and 0.8%, respectively (n = 10). It was found that most of the common metal ions and anions did not interfere with the thorium determination. The proposed method was successfully applied to its analysis in various water samples. (author)

Design and development of amperometric biosensor for the detection of lead and mercury ions in water matrix-a permeability approach.

Science.gov (United States)

Gumpu, Manju Bhargavi; Krishnan, Uma Maheswari; Rayappan, John Bosco Balaguru

2017-07-01

Intake of water contaminated with lead (Pb 2+ ) and mercury (Hg 2+ ) ions leads to various toxic effects and health issues. In this context, an amperometric urease inhibition-based biosensor was developed to detect Pb 2+ and Hg 2+ ions in water matrix. The modified Pt/CeO 2 /urease electrode was fabricated by immobilizing CeO 2 nanoparticles and urease using a semi-permeable adsorption layer of nafion. With urea as a substrate, urease catalytic activity was examined through cyclic voltammetry. Further, maximum amperometric inhibitive response of the modified Pt/CeO 2 /urease electrode was observed in the presence of Pb 2+ and Hg 2+ ions due to the urease inhibition at specific potentials of -0.03 and 0 V, respectively. The developed sensor exhibited a detection limit of 0.019 ± 0.001 μM with a sensitivity of 89.2 × 10 -3  μA μM -1 for Pb 2+ ions. A detection limit of 0.018 ± 0.003 with a sensitivity of 94.1 × 10 -3  μA μM -1 was achieved in detecting Hg 2+ ions. The developed biosensor showed a fast response time (<1 s) with a linear range of 0.5-2.2 and 0.02-0.8 μM for Pb 2+ and Hg 2+ ions, respectively. The modified electrode offered a good stability for 20 days with a good repeatability and reproducibility. The developed sensor was used to detect Pb 2+ and Hg 2+ ions contaminating Cauvery river water and the observed results were in good co-ordination with atomic absorption spectroscopic data.

Amperometric sensor for carbon dioxide: design, characteristics, and perforance

International Nuclear Information System (INIS)

Evans, J.; Pletcher, D.; Warburton, P.R.G.; Gibbs, T.K.

1989-01-01

A new sensor for atmospheric carbon dioxide is described. It is an amperometric device based on a porous electrode in a three-electrode cell and the electrolyte is a copper diamine complex in aqueous potassium chloride. The platinum cathode, held at constant potential, is used to detect the formation of Cu 2+ following the change in the pH of the solution when the sensor is exposed to an atmosphere containing carbon dioxide. The sensor described is designed to monitor carbon dioxide concentrations in the range 0-5%, although with some modifications, other ranges would be possible. The response to a change in the carbon dioxide content of the atmosphere is rapid (about 10s) while the monitored current is strongly (but nonlinearly) dependent on carbon dioxide concentration. Unlike other amperometric devices for carbon dioxide, there is no interference from oxygen although other acid gases would lead to an interfering response

Quantum dots as chemiluminescence enhancers tested by sequential injection technique: Comparison of flow and flow-batch conditions

Energy Technology Data Exchange (ETDEWEB)

Sklenářová, Hana, E-mail: sklenarova@faf.cuni.cz [Charles University in Prague, Faculty of Pharmacy in Hradec Králové, Department of Analytical Chemistry, Hradec Králové (Czech Republic); Voráčová, Ivona [Institute of Analytical Chemistry of the CAS, v. v. i., Brno (Czech Republic); Chocholouš, Petr; Polášek, Miroslav [Charles University in Prague, Faculty of Pharmacy in Hradec Králové, Department of Analytical Chemistry, Hradec Králové (Czech Republic)

2017-04-15

The effect of 0.01–100 µmol L{sup −1} Quantum Dots (QDs) with different emission wavelengths (520–640 nm) and different surface modifications (mercaptopropionic, mercaptoundecanoic, thioglycolic acids and mercaptoethylamine) on permanganate-induced and luminol–hydrogen peroxide chemiluminescence (CL) was studied in detail by a sequential injection technique using a spiral detection flow cell and a flow-batch detection cell operated in flow and stop-flow modes. In permanganate CL system no significant enhancement of the CL signal was observed while for the luminol–hydrogen peroxide CL substantial increase (>100% and >90% with the spiral detection cell in flow and stop-flow modes, respectively) was attained for CdTe QDs. Enhancement exceeding 120% was observed for QDs with emissions at 520, 575 and 603 nm (sizes of 2.8 nm, 3.3 nm and 3.6 nm) using the flow-batch detection cell in the stop-flow mode. Pronounced effect was noted for surface modifications while mercaptoethylamine was the most efficient in CL enhancement compared to mercaptopropionic acid the most commonly applied coating. Significant difference between results obtained in flow and flow-batch conditions based on the entire kinetics of the extremely fast CL reaction was discussed. The increase of the CL signal was always accompanied by reduced lifetime of the CL emission thus application of QDs in flow techniques should be always coupled with the study of the CL lifetime.

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

Amperometric detection of hydrazine utilizing synergistic action of prussian blue @ silver nanoparticles / graphite felt modified electrode

International Nuclear Information System (INIS)

Zhao, Jihua; Liu, Jianxin; Tricard, Simon; Wang, Lei; Liang, Yanling; Cao, Linghua; Fang, Jian; Shen, Weiguo

2015-01-01

Highlights: • Prussian Blue (PB) deposition on Ag/GF for electrochemical hydrazine sensing; • Lower detection limit of 4.9 × 10 −7 mol L −1 , stable over 24 days; • High sensitivity: 26.06 A mol −1 L. -- Abstract: In this study, a triple-component hydrazine sensor (PB@Ag/GF) was fabricated with freestanding graphite felt (GF), silver nanoparticles (Ag) and prussian blue (PB). The Ag nanoparticles were electrodeposited on GF ultrasonically (Ag/GF), and acted as a catalyst of the chemical deposition of PB. The electrode was characterized by scanning election microscopy (SEM), infrared spectroscopy (IR), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDS). The electrochemical behavior of PB@Ag/GF was measured by cyclic voltammetry and amperometric measurements. The sensor displayed a prominent electrocatalytic activity toward hydrazine oxidation, with a fast response time of 2 s, a low detection limit of 4.9 × 10 −7 mol L −1 and very high detection sensitivity of 26.06 A mol −1 L

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.

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

Polyion selective polymeric membrane-based pulstrode as a detector in flow-injection analysis.

Science.gov (United States)

Bell-Vlasov, Andrea K; Zajda, Joanna; Eldourghamy, Ayman; Malinowska, Elzbieta; Meyerhoff, Mark E

2014-04-15

A method for the detection of polyions using fully reversible polyion selective polymeric membrane type pulstrodes as detectors in a flow-injection analysis (FIA) system is examined. The detection electrode consists of a plasticized polymeric membrane doped with 10 wt % of tridodecylmethylammonium-dinonylnaphthalene sulfonate (TDMA/DNNS) ion-exchanger salt. The pulse sequence used involves a short (1 s) galvanostatic pulse, an open-circuit pulse (0.5 s) during which the EMF of the cell is measured, and a longer (15 s) potentiostatic pulse to return the membrane to its original chemical composition. It is shown that total pulse sequence times can be optimized to yield reproducible real-time detection of injected samples of protamine and heparin at up to 20 samples/h. Further, it is shown that the same membrane detector can be employed for FIA detection of both polycations at levels ≥10 μg/mL and polyanions at levels of ≥40 μg/mL by changing the direction of the galvanostatic pulse. The methodology described may also be applicable in the detection of polyionic species at low levels in other flowing configurations, such as in liquid chromatography and capillary electrophoresis.

Determination of biogenic amines in chocolate by ion chromatographic separation and pulsed integrated amperometric detection with implemented wave-form at Au disposable electrode.

Science.gov (United States)

Pastore, Paolo; Favaro, Gabriella; Badocco, Denis; Tapparo, Andrea; Cavalli, Silvano; Saccani, Giovanna

2005-12-09

A rapid and selective cation exchange chromatographic method coupled to integrated pulsed amperometric detection (PAD) has been developed to quantify biogenic amines in chocolate. The method is based on gradient elution of aqueous methanesulfonic acid with post column addition of strong base to obtain suitable conditions for amperometric detection. A potential waveform able to keep long time performance of the Au disposable electrode was set up. Total analysis time is less than 20min. Concentration levels of dopamine, serotonin, tyramine, histamine and 2-phenylethylamine were measured, after extraction with perchloric acid from 2g samples previously defatted twice with petroleum ether. The method was used to determine the analytes in chocolate real matrices and their quantification was made with standard addition method. Only dopamine, histamine and serotonin were found in the analysed real samples. Repeatabilities of their signals, computed on their amounts in the real samples, were 5% for all of them. Repeatabilities of tyramine and phenethylamine were relative to standard additions to real samples (close to 1mg/l in the extract) and were 7 and 3%, respectively. Detection limits were computed with the 3s of the baseline noise combined with the calibration plot regression parameters. They were satisfactorily low for all amines: 3mg/kg for dopamine, 2mg/kg for tyramine, 1mg/kg for histamine, 2mg/kg for serotonin, 3mg/kg for 2-phenylethylamine.

Left coronary arterial blood flow: Noninvasive detection by Doppler US

International Nuclear Information System (INIS)

Gramiak, R.; Holen, J.; Moss, A.J.; Gutierrez, O.H.; Picone, A.L.; Roe, S.A.

1986-01-01

Continuous wave (CW) and pulsed Doppler ultrasound studies with spectral analysis were used to detect the left coronary arterial blood flow in patients who were undergoing routine echocardiography. The pulmonary artery is a stable ultrasonic landmark from which detection of the blood flow can be effected. The left coronary artery can be distinguished by its blood flow toward the cardiac apex and by specific, functional flow features. Flow patterns vary among the left main, circumflex, and anterior descending arteries; patterns also vary with respiration cycles. In the present study, coronary arterial blood flow was detected in 58 of 70 patients (83%). Findings were validated by selectively injecting an agitated saline contrast medium into the left coronary artery and, in another study, by comparing human Doppler phasic flow waveforms with electromagnetic flowmeter recordings obtained in dogs

Amperometric biosensor based on carbon nanotubes coated with polyaniline/dendrimer-encapsulated Pt nanoparticles for glucose detection

International Nuclear Information System (INIS)

Xu Lihuan; Zhu Yihua; Yang Xiaoling; Li Chunzhong

2009-01-01

A novel amperometric glucose biosensor based on the nanocomposites of multi-wall carbon nanotubes (CNT) coated with polyaniline (PANI) and dendrimer-encapsulated Pt nanoparticles (Pt-DENs) is prepared. CNT coated with protonated PANI is in situ synthesized and Pt-DENs is absorbed on PANI/CNT composite surface by self-assembly method. Then Glucose oxidase (GOx) is crosslink-immobilizated onto Pt-DENs/PANI/CNT composite film. The results show that the fabricated GOx/Pt-DENs/PANI/CNT electrode exhibits excellent response performance to glucose, such as low detection limit (0.5 μM), wide linear range (1 μM-12 mM), short response time (about 5 s), high sensitivity (42.0 μA mM -1 cm -2 ) and stability (83% remains after 3 weeks).

3D-printed and CNC milled flow-cells for chemiluminescence detection.

Science.gov (United States)

Spilstead, Kara B; Learey, Jessica J; Doeven, Egan H; Barbante, Gregory J; Mohr, Stephan; Barnett, Neil W; Terry, Jessica M; Hall, Robynne M; Francis, Paul S

2014-08-01

Herein we explore modern fabrication techniques for the development of chemiluminescence detection flow-cells with features not attainable using the traditional coiled tubing approach. This includes the first 3D-printed chemiluminescence flow-cells, and a milled flow-cell designed to split the analyte stream into two separate detection zones within the same polymer chip. The flow-cells are compared to conventional detection systems using flow injection analysis (FIA) and high performance liquid chromatography (HPLC), with the fast chemiluminescence reactions of an acidic potassium permanganate reagent with morphine and a series of adrenergic phenolic amines. Copyright © 2014 Elsevier B.V. All rights reserved.

A volumetric flow sensor for automotive injection systems

International Nuclear Information System (INIS)

Schmid, U; Krötz, G; Schmitt-Landsiedel, D

2008-01-01

For further optimization of the automotive power train of diesel engines, advanced combustion processes require a highly flexible injection system, provided e.g. by the common rail (CR) injection technique. In the past, the feasibility to implement injection nozzle volumetric flow sensors based on the thermo-resistive measurement principle has been demonstrated up to injection pressures of 135 MPa (1350 bar). To evaluate the transient behaviour of the system-integrated flow sensors as well as an injection amount indicator used as a reference method, hydraulic simulations on the system level are performed for a CR injection system. Experimentally determined injection timings were found to be in good agreement with calculated values, especially for the novel sensing element which is directly implemented into the hydraulic system. For the first time pressure oscillations occurring after termination of the injection pulse, predicted theoretically, could be verified directly in the nozzle. In addition, the injected amount of fuel is monitored with the highest resolution ever reported in the literature

A volumetric flow sensor for automotive injection systems

Science.gov (United States)

Schmid, U.; Krötz, G.; Schmitt-Landsiedel, D.

2008-04-01

For further optimization of the automotive power train of diesel engines, advanced combustion processes require a highly flexible injection system, provided e.g. by the common rail (CR) injection technique. In the past, the feasibility to implement injection nozzle volumetric flow sensors based on the thermo-resistive measurement principle has been demonstrated up to injection pressures of 135 MPa (1350 bar). To evaluate the transient behaviour of the system-integrated flow sensors as well as an injection amount indicator used as a reference method, hydraulic simulations on the system level are performed for a CR injection system. Experimentally determined injection timings were found to be in good agreement with calculated values, especially for the novel sensing element which is directly implemented into the hydraulic system. For the first time pressure oscillations occurring after termination of the injection pulse, predicted theoretically, could be verified directly in the nozzle. In addition, the injected amount of fuel is monitored with the highest resolution ever reported in the literature.

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.

Exploiting flow injection and sequential injection for trace metal determinations in conjunction with detection by electrothermal atomic absorption spectrometry and inductively coupled plasma mass spectrometry

DEFF Research Database (Denmark)

Hansen, Elo Harald

and selectivity. Either in order to separate/preconcentrate the analyte material, or because of the presence of potentially interfering matrix constituents. Such pretreatments are advantageously performed in flow injection (FI) or sequential injection (SI) manifolds, where all appropriate unit operations can...

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.

Home-Made Micro Valve for Determining Malachite Green Dye by Flow Injection Analysis

Directory of Open Access Journals (Sweden)

Amal Saadoon Majeed

2017-07-01

Full Text Available The research is included studying and designing micro flow injection system which is characterized with rapidity, simplicity, and low cost for the determination of green malachite dye. The study of flow rate of carrier stream, repeatability, dispersion coefficient, and calibration graph are conducted. It is found that the optimum conditions for the determination of mentioned dye are flow rate 4.200 mL/min, sampling rate 102 sample/h, limit of detection 0.05 ppm, linear range (0.05-18.00 ppm with linearity (R2=0.9700, RSD is 0.355, the repeatability for seven successive injections is studied for the two concentrations 5 ppm and 12 ppm, and the dispersion coefficient values are 1.73 and 1.28 at the two concentrations 2 ppm and 9 ppm respectively.

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...

[Studies on a sequential injection renewable surface reflectance spectrophotometric system using a microchip flow cell].

Science.gov (United States)

Wang, Jian-ya; Fang, Zhao-lun

2002-02-01

A microchip flow cell was developed for flow injection renewable surface assay by reflectance spectrophotometry. The flow cell was coupled to a sequential injection system and optical fiber photometric detection system. The flow cell featured a three-layer structure. The flow channel was cut into a silicone rubber membrance which formed the middle layer, and a porous filter was inlayed across a widened section of the channel to trap microbeads introduced into the flow cell. The area of the detection window of the flow cell was approximately 3.6 mm2, the volume of the bead trapped in the flow cell was 2.2 microL, the depth of the bead layer was 600 microns. A multistrand bifurcated optical fiber was coupled with incident light, detector and flow cell. The chromogenic reaction of Cr(VI) with 1,5-diphenylcarbohydrazide (DPC) which was adsorbed on trapped Polysorb C-18 beads was used as a model reaction to optimize the flow cell design and the experimental system. The reflectance of the renewable reaction surface was monitored at 540 nm. With 100 microL sample loaded and 1.0 mL.min-1 carrier flow rate, the linear response range was 0-0.6 microgram.mL-1 Cr(VI). A detection limit (3 sigma) of 6 ng.mL-1, precision of 1.5% RSD(n = 11), and a throughput of 64 samples per hour were achieved. Considerations in system and flow cell design, the influence of depth of the bead layer, weight of beads used, and the flow rates of carrier stream on the performance were discussed.

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.

Development of a flow method for the determination of phosphate in estuarine and freshwaters-Comparison of flow cells in spectrophotometric sequential injection analysis

International Nuclear Information System (INIS)

Mesquita, Raquel B.R.; Ferreira, M. Teresa S.O.B.; Toth, Ildiko V.; Bordalo, Adriano A.; McKelvie, Ian D.; Rangel, Antonio O.S.S.

2011-01-01

Highlights: → Sequential injection determination of phosphate in estuarine and freshwaters. → Alternative spectrophotometric flow cells are compared. → Minimization of schlieren effect was assessed. → Proposed method can cope with wide salinity ranges. → Multi-reflective cell shows clear advantages. - Abstract: A sequential injection system with dual analytical line was developed and applied in the comparison of two different detection systems viz; a conventional spectrophotometer with a commercial flow cell, and a multi-reflective flow cell coupled with a photometric detector under the same experimental conditions. The study was based on the spectrophotometric determination of phosphate using the molybdenum-blue chemistry. The two alternative flow cells were compared in terms of their response to variation of sample salinity, susceptibility to interferences and to refractive index changes. The developed method was applied to the determination of phosphate in natural waters (estuarine, river, well and ground waters). The achieved detection limit (0.007 μM PO 4 3- ) is consistent with the requirement of the target water samples, and a wide quantification range (0.024-9.5 μM) was achieved using both detection systems.

Development of a flow method for the determination of phosphate in estuarine and freshwaters-Comparison of flow cells in spectrophotometric sequential injection analysis

Energy Technology Data Exchange (ETDEWEB)

Mesquita, Raquel B.R. [CBQF/Escola Superior de Biotecnologia, Universidade Catolica Portuguesa, R. Dr. Antonio Bernardino de Almeida, 4200-072 Porto (Portugal); Laboratory of Hydrobiology, Institute of Biomedical Sciences Abel Salazar (ICBAS) and Institute of Marine Research (CIIMAR), Universidade do Porto, Lg. Abel Salazar 2, 4099-003 Porto (Portugal); Ferreira, M. Teresa S.O.B. [CBQF/Escola Superior de Biotecnologia, Universidade Catolica Portuguesa, R. Dr. Antonio Bernardino de Almeida, 4200-072 Porto (Portugal); Toth, Ildiko V. [REQUIMTE, Departamento de Quimica, Faculdade de Farmacia, Universidade de Porto, Rua Anibal Cunha, 164, 4050-047 Porto (Portugal); Bordalo, Adriano A. [Laboratory of Hydrobiology, Institute of Biomedical Sciences Abel Salazar (ICBAS) and Institute of Marine Research (CIIMAR), Universidade do Porto, Lg. Abel Salazar 2, 4099-003 Porto (Portugal); McKelvie, Ian D. [School of Chemistry, University of Melbourne, Victoria 3010 (Australia); Rangel, Antonio O.S.S., E-mail: aorangel@esb.ucp.pt [CBQF/Escola Superior de Biotecnologia, Universidade Catolica Portuguesa, R. Dr. Antonio Bernardino de Almeida, 4200-072 Porto (Portugal)

2011-09-02

Highlights: {yields} Sequential injection determination of phosphate in estuarine and freshwaters. {yields} Alternative spectrophotometric flow cells are compared. {yields} Minimization of schlieren effect was assessed. {yields} Proposed method can cope with wide salinity ranges. {yields} Multi-reflective cell shows clear advantages. - Abstract: A sequential injection system with dual analytical line was developed and applied in the comparison of two different detection systems viz; a conventional spectrophotometer with a commercial flow cell, and a multi-reflective flow cell coupled with a photometric detector under the same experimental conditions. The study was based on the spectrophotometric determination of phosphate using the molybdenum-blue chemistry. The two alternative flow cells were compared in terms of their response to variation of sample salinity, susceptibility to interferences and to refractive index changes. The developed method was applied to the determination of phosphate in natural waters (estuarine, river, well and ground waters). The achieved detection limit (0.007 {mu}M PO{sub 4}{sup 3-}) is consistent with the requirement of the target water samples, and a wide quantification range (0.024-9.5 {mu}M) was achieved using both detection systems.

Evaluation of different disinfectants on the performance of an on-meter dosed amperometric glucose-oxidase-based glucose meter.

Science.gov (United States)

Sarmaga, Don; Dubois, Jeffrey A; Lyon, Martha E

2011-11-01

Off-meter dosed photometric glucose-oxidase-based glucose meters have been reported to be susceptible to interference by hydrogen-peroxide-based disinfecting agents. The objective of this study was to determine if a single application of hydrogen-peroxide-containing Accel® wipe to disinfect an on-meter dosed amperometric glucose-oxidase-based glucose meter will influence its performance. The performance of five on-meter dosed amperometric glucose-oxidase-based glucose meters was determined before and after disinfecting the devices with a single application of either CaviWipes® (14.3% isopropanol and 0.23% diisobutyl-phenoxy-ethoxyethyl dimethyl benzyl ammonium chloride) or Accel (0.5% hydrogen peroxide) wipes. Replicate glucose measurements were conducted before disinfecting the devices, immediately after disinfecting, and then 1 and 2 min postdisinfecting, with measurements in triplicate. Analysis was sequentially completed for five different meters. Results were analyzed by a two-way analysis of variance (Analyze-it software). No clinical ( .05) in glucose concentration were detected when the on-meter dosed amperometric glucose-oxidase-based glucose meters were disinfected with either CaviWipes or Accel wipes and measured immediately or 1 or 2 min postdisinfecting. No clinically significant difference in glucose concentration was detected between meters (glucose oxidase amperometric-based glucose meters are not analytically susceptible to interference by a single application of hydrogen-peroxide-containing Accel disinfectant wipes. © 2011 Diabetes Technology Society.

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 ...

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.

Minicolumn field preconcentration and flow-injection flame atomic absorption spectrometric determination of cadmium in seawater

International Nuclear Information System (INIS)

Yebra-Biurrun, M.C.; Moreno-Cid, A.; Puig, L.

2004-01-01

A simple method for the continuous field preconcentration of trace dissolved cadmium in seawater samples has been developed based on the minicolumn field sampling technique. For this purpose, minicolumns containing Chelite P (aminomethylphosphonic groups) were connected to a field flow preconcentration system (FFPS). Once in the laboratory, these minicolumns are sequentially inserted into a flow-injection system for on-line cadmium elution and detection by flame atomic absorption spectrometry. Factorial designs have been used to optimise the FFPS and the flow-injection elution process. Six experimental variables were optimised: sample pH, sample flow-rate, eluent concentration, eluent volume, eluent flow-rate and minicolumn diameter. The detection limit (3F) of the procedure was 2.7 ng l -1 for a sample volume of 300 ml. The precision (expressed as relative standard deviation) for 11 independent determinations was 0.5-9.4% for cadmium solutions of 10-300 ng l -1 . Analysis of certified reference materials (SLEW-3 and NASS-5) showed good agreement with the certified values. This procedure has been successfully applied to the determination of cadmium in seawater samples from Galicia (Spain)

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.

Analysis of polyphenols in white wine by CZE with amperometric detection using carbon nanotube-modified electrodes.

Science.gov (United States)

Moreno, Mónica; Arribas, Alberto Sánchez; Bermejo, Esperanza; Zapardiel, Antonio; Chicharro, Manuel

2011-04-01

A method for the simultaneous detection of five polyphenols (caffeic, chlorogenic, ferulic and gallic acids and (+)-catechin) by CZE with electrochemical detection was developed. Separation of these polyphenols was performed in a 100 mM borate buffer (pH 9.2) within 15 min. Under optimized separation conditions, the performance of glassy carbon (GC) electrodes modified with multiwalled carbon nanotube layer obtained from different dispersions was examined. GC electrode modified with a dispersion of multi-walled carbon nanotubes (CNT) in polyethylenimine has proven to be the most suitable CNT-based electrode for its application as amperometric detector for the CZE separation of the studied compounds. The excellent electrochemical properties of this electrode allowed the detection of the selected polyphenols at +200 mV and improved the efficiency and the resolution of their CZE separation. Limits of detection below 3.1 μM were obtained with linear ranges covering the 10⁻⁵ to 10⁻⁴  M range. The proposed method has been successfully applied for the detection (ferulic, caffeic and gallic acids and (+)-catechin) and the quantification (gallic acid and (+)-catechin) of polyphenols in two different white wines without any preconcentration step. A remarkable signal stability was observed on the electrode performance despite the presence of potential fouling substances in wine. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Automated injection of slurry samples in flow-injection analysis

NARCIS (Netherlands)

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

1996-01-01

Two types of injectors are described for introducing solid samples as slurries in flow analysis systems. A time-based and a volume-based injector based on multitube solenoid pinch valves were built, both can be characterized as hydrodynamic injectors. Reproducibility of the injections of dispersed

An Effective Amperometric Biosensor Based on Gold Nanoelectrode Arrays

Directory of Open Access Journals (Sweden)

Zhu Yingchun

2008-01-01

Full Text Available Abstract A sensitive amperometric biosensor based on gold nanoelectrode array (NEA was investigated. The gold nanoelectrode array was fabricated by template-assisted electrodeposition on general electrodes, which shows an ordered well-defined 3D structure of nanowires. The sensitivity of the gold NEA to hydrogen peroxide is 37 times higher than that of the conventional electrode. The linear range of the platinum NEA toward H2O2is from 1 × 10−6to 1 × 10−2 M, covering four orders of magnitudes with detection limit of 1 × 10−7 M and a single noise ratio (S/N of four. The enzyme electrode exhibits an excellent response performance to glucose with linear range from 1 × 10−5to 1 × 10−2 M and a fast response time within 8 s. The Michaelis–Menten constantkm and the maximum current densityi maxof the enzyme electrode were 4.97 mM and 84.60 μA cm−2, respectively. This special nanoelectrode may find potential application in other biosensors based on amperometric signals.

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.

Flow improvers for water injection based on surfactants

Energy Technology Data Exchange (ETDEWEB)

Oskarsson, H.; Uneback, I.; Hellsten, M.

2006-03-15

In many cases it is desirable to increase the flow of injection water when an oil well deteriorates. It is very costly in offshore operation to lay down an additional water pipe to the injection site. Flow improvers for the injection water will thus be the most cost-effective way to increase the flow rate. During the last years water-soluble polymers have also been applied for this purpose. These drag-reducing polymers are however only slowly biodegraded which has been an incentive for the development of readily biodegradable surfactants as flow improvers for injection water. A combination of a zwitterionic and an anionic surfactant has been tested in a 5.5 inch, 700 m long flow loop containing sulphate brine with salinity similar to sea water. A drag reduction between 75 and 80% was achieved with 119 ppm in solution of the surfactant blend at an average velocity of 1.9 m/s and between 50 and 55% at 2.9 m/s. The surfactants in this formulation were also found to be readily biodegradable in sea water and low bio accumulating which means they have an improved environmental profile compared to the polymers used today. Due to the self-healing properties of the drag-reducing structures formed by surfactants, these may be added before the pump section - contrary to polymers which are permanently destroyed by high shear forces. (Author)

Construction of a new functional platform by grafting poly(4-vinylpyridine) in multi-walled carbon nanotubes for complexing copper ions aiming the amperometric detection of L-cysteine

International Nuclear Information System (INIS)

Carvalho Castro e Silva, Cecília de; Breitkreitz, Márcia Cristina; Santhiago, Murilo; Crispilho Corrêa, Cátia; Tatsuo Kubota, Lauro

2012-01-01

Highlights: ► Construction of new nanostructured platform based on MWCNTs–PVP to complex copper(II) ions. ► Development of an amperometric sensor for highly selective determination of Cys in food supplement samples. ► Combination of nanocomposite and the copper(II) ions causes a dramatic enhancement in the sensitivity of Cys quantification at low overpotential. - Abstract: This work describes the preparation of an amperometric sensor for electrocatalytical detection of L-cysteine (Cys). The developed sensor is based on a functional platform to complex copper ions on multi-walled carbon nanotubes (MWCNTs) modified with poly-4-vinylpyridine (PVP) through an in situ polymerization. The obtained values for the kinetic constants of heterogeneous electron transfer rate (k s ) and for chemical reaction (k obs ) between Cu 2+ and cysteine were 5.78 s −1 and 6.96 L mol −1 s −1 , respectively. The analytical curve showed a linear response range for detecting L-cysteine in concentrations from 5 to 60 μmol L −1 . The detection and quantification limits obtained were 1.50 and 5.00 μmol L −1 , respectively with a response time of 0.10 s at an applied potential of 150 mV vs SCE.

Amperometric Biosensor Based on Diamine Oxidase/Platinum Nanoparticles/Graphene/Chitosan Modified Screen-Printed Carbon Electrode for Histamine Detection.

Science.gov (United States)

Apetrei, Irina Mirela; Apetrei, Constantin

2016-03-24

This work describes the development and optimization studies of a novel biosensor employed in the detection and quantification of histamine in freshwater fish samples. The proposed biosensor is based on a modified carbon screen-printed electrode with diamineoxidase, graphene and platinum nanoparticles, which detects the hydrogen peroxide formed by the chemical process biocatalysed by the enzyme diamine oxidase and immobilized onto the nanostructurated surface of the receptor element. The amperometric measurements with the biosensor have been implemented in buffer solution of pH 7.4, applying an optimal low potential of +0.4 V. The novel biosensor shows high sensitivity (0.0631 μA·μM), low detection limit (2.54 × 10(-8) M) and a broad linear domain from 0.1 to 300 μM. The applicability in natural complex samples and the analytical parameters of this enzyme sensor have been performed in the quantification of histamine in freshwater fish. An excellent correlation among results achieved with the developed biosensor and results found with the standard method for all freshwater fish samples has been achieved.

Stopped-flow injection spectrophotometric method for determination of chlorate in soil

Directory of Open Access Journals (Sweden)

Jaroon Jakmunee

2008-06-01

Full Text Available A stopped-flow injection (FI spectrophotometric procedure based on iodometric reaction for the determination of chlorate has been developed. Standard/sample was injected into a stream of potassium iodide solution and then merged with a stream of hydrochloric acid solution to produce triiodide. By stopping the flow while the sample zone is being in a mixing coil, a slow reaction of chlorate with iodide in acidic medium was promoted to proceed with minimal dispersion of the triiodide product zone. When the flow started again, a concentrated product zone was pushed into a flow cell and a signal profile due to light absorption of the product was recorded. Employing a lab-built semi-automatic stopped-FI analyser, the analysis can be performed with higher degree of automation and low chemical consumption. Linear calibration graph in the range of 5-50 mg ClO3- L-1 was obtained, with detection limit of 1.4 mg ClO3- L-1. Relative standard deviation of 2.2% (30 mg ClO3- L-1, n=10 and sample throughput of about 20 h-1 were achieved. The system was applied to soil samples and validated by batch spectrophotometric and standard titrimetric methods.

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.

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

International Nuclear Information System (INIS)

Kanchana, P.; Lavanya, N.; Sekar, C.

2014-01-01

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 −7 to 1.0 × 10 −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

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....... Therefore, and in order to implement functions such as periodic calibration, conditioning and possible regeneration of the biosensor, and, very importantly, to yield the freedom to select the optimum detection means, it is advantageous to use these devices in a flow-through mode, particularly by employing...... the flow injection (FI) approach. The capacity of FI, as offering itself as a complementary facility to augment the performance of biosensors, and in many cases as an attractive alternative, is demonstrated by reference to selected examples, comprising assays based on enzymatic procedures with optical...

Determination of uranium in natural waters and high-purity aluminum by flow-injection on-line preconcentration and ICP-MS detection

International Nuclear Information System (INIS)

Seki, Tatsuya; Oguma, Koichi

2004-01-01

A flow injection method has been developed for the determination of uranium is natural waters and high-purity aluminum by use of on-line preconcentration on a U/TEVA TM column and ICP-MS detection. The sample solution prepared as a nitric acid solution in 3 mol l -1 was passed through the U/TEVA TM column to collect uranium and uranium adsorbed was eluted with 0.1 mol l -1 nitric acid. The effluent was introduced directly into the nebulizer of the ICP-MS and 238 U was measured. The detection limit, calculated as 3-times the standard deviation of the background noise, was 3pg and the sample throughput was about 10 per hour. The proposed method was successfully applied to the determination of uranium in river-water reference materials, a seawater reference material and high-purity aluminum reference materials. (author)

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.

Flow-injection system for automated dissolution testing of isoniazid tablets with chemiluminescence detection.

Science.gov (United States)

Li, B; Zhang, Z; Liu, W

2001-05-30

A simple and sensitive flow-injection chemiluminescence (CL) system for automated dissolution testing is described and evaluated for monitoring of dissolution profiles of isoniazid tablets. The undissolved suspended particles in the dissolved solution were eliminated via on-line filter. The novel CL system of KIO(4)-isoniazid was also investigated. The sampling frequency of the system was 120 h(-1). The dissolution profiles of isoniazid fast-release tablets from three sources were determined, which demonstrates the stability, great sensitivity, large dynamic measuring range and robustness of the system.

Development of an automated flow injection analysis system for determination of phosphate in nutrient solutions.

Science.gov (United States)

Karadağ, Sevinç; Görüşük, Emine M; Çetinkaya, Ebru; Deveci, Seda; Dönmez, Koray B; Uncuoğlu, Emre; Doğu, Mustafa

2018-01-25

A fully automated flow injection analysis (FIA) system was developed for determination of phosphate ion in nutrient solutions. This newly developed FIA system is a portable, rapid and sensitive measuring instrument that allows on-line analysis and monitoring of phosphate ion concentration in nutrient solutions. The molybdenum blue method, which is widely used in FIA phosphate analysis, was adapted to the developed FIA system. The method is based on the formation of ammonium Mo(VI) ion by reaction of ammonium molybdate with the phosphate ion present in the medium. The Mo(VI) ion then reacts with ascorbic acid and is reduced to the spectrometrically measurable Mo(V) ion. New software specific for flow analysis was developed in the LabVIEW development environment to control all the components of the FIA system. The important factors affecting the analytical signal were identified as reagent flow rate, injection volume and post-injection flow path length, and they were optimized using Box-Behnken experimental design and response surface methodology. The optimum point for the maximum analytical signal was calculated as 0.50 mL min -1 reagent flow rate, 100 µL sample injection volume and 60 cm post-injection flow path length. The proposed FIA system had a sampling frequency of 100 samples per hour over a linear working range of 3-100 mg L -1 (R 2  = 0.9995). The relative standard deviation (RSD) was 1.09% and the limit of detection (LOD) was 0.34 mg L -1 . Various nutrient solutions from a tomato-growing hydroponic greenhouse were analyzed with the developed FIA system and the results were found to be in good agreement with vanadomolybdate chemical method findings. © 2018 Society of Chemical Industry. © 2018 Society of Chemical Industry.

A multisyringe flow injection system with immobilized glucose oxidase based on homogeneous chemiluminescence detection

International Nuclear Information System (INIS)

Manera, Matias; Miro, Manuel; Estela, Jose Manuel; Cerda, Victor

2004-01-01

In this paper, enzyme containing reactors are for the first time implemented in the multisyringe flow injection analysis (MSFIA) technique interfaced with chemiluminescence detection for biochemical assays. The automated methodology is based on the on-line substrate conversion in an oxidase packed-bed reactor and the post-column chemiluminogenic catalysed-reaction of the generated oxidising species with an organic molecule (namely, 3-aminophthalhydrazide) in front of the photosensor module. Various catalysts in homogeneous phase are compared taking advantage of the benefits of the MSFIA concept. On one hand, mineral catalysts (namely, Co(II)) are assessed, on the other hand, minute and accurate volumes of soluble organic species (viz., horseradish peroxidase (HRP)) are readily handled without requiring further immobilization protocols. The potentials of the MSFIA-CL concept with immobilisation of the proper oxidase protein are demonstrated using glucose as a model of substrate. Despite the different pH and kinetic requirements for both the substrate conversion in the enzyme-reactor and the Co(II)/HRP-mediated luminol oxidation integrated in the flow system, the MSFIA approach warrants maximum yields owing to the independent optimisation of the physical and chemical parameters of the various reactions involved. Under the optimised configurations and experimental variables, dynamic working ranges from 2.5x10 -6 to 1.0x10 -3 mol l -1 glucose may be obtained for both detection schemes by proper photomultiplier gain selection. The detection and determination limits calculated at the 3σ and 10σ level were 8.6x10 -7 and 2.0x10 -6 mol l -1 glucose, respectively, for the Co(II)-luminol system, and 1.3x10 -6 and 2.3x10 -6 mol l -1 glucose, respectively, for the HRP-luminol procedure. The repeatability (n=10) at the 1.0x10 -5 mol l -1 level was slightly better for the Co(II)-catalysed reaction (2.5% versus 4.0%). The developed MSFIA-CL methodology was used for kinetic

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...

Determination of mercury by multisyringe flow injection system with cold-vapor atomic absorption spectrometry

International Nuclear Information System (INIS)

Leal, L.O.; Elsholz, O.; Forteza, R.; Cerda, V.

2006-01-01

A new software-controlled time-based multisyringe flow injection system for mercury determination by cold-vapor atomic absorption spectrometry is proposed. Precise known volumes of sample, reducing agent (1.1% SnCl 2 in 3% HCl) and carrier (3% HCl) are dispensed into a gas-liquid separation cell with a multisyringe burette coupled with one three-way solenoid valve. An argon flow delivers the reduced mercury to the spectrometer. The optimization of the system was carried out testing reaction coils and gas-liquid separators of different design as well as changing parameters, such as sample and reagents volumes, reagent concentrations and carrier gas flow rate, among others. The analytical curves were obtained within the range 50-5000 ng L -1 . The detection limit (3σ b /S) achieved is 5 ng L -1 . The relative standard deviation (R.S.D.) was 1.4%, evaluated from 16 successive injections of 250 ng L -1 Hg standard solution. The injection and sample throughput per hour were 44 and 11, respectively. This technique was validated by means of solid and water reference materials with good agreement with the certified values and was successfully applied to fish samples

3D-CFD Simulation of Confined Cross-Flow Injection Process Using Single Piston Pump

Directory of Open Access Journals (Sweden)

M. Elashmawy

2017-12-01

Full Text Available Injection process into a confined cross flow is quite important for many applications including chemical engineering and water desalination technology. The aim of this study is to investigate the performance of the injection process into a confined cross-flow of a round pipe using a single piston injection pump. A computational fluid dynamics (CFD analysis has been carried out to investigate the effect of the locations of the maximum velocity and minimum pressure on the confined cross-flow process. The jet trajectory is analyzed and related to the injection pump shaft angle of rotation during the injection duty cycle by focusing on the maximum instant injection flow of the piston action. Results indicate a low effect of the jet trajectory within the range related to the injection pump operational conditions. Constant cross-flow was used and injection flow is altered to vary the jet to line flow ratio (QR. The maximum jet trajectory exhibits low penetration inside the cross-flow. The results showed three regions of the flow ratio effect zones with different behaviors. Results also showed that getting closer to the injection port causes a significant decrease on the locations of the maximum velocity and minimum pressure.

Determination of boron in natural water and products derived from grape using an automated flow injection analysis system with piezoelectric detection

International Nuclear Information System (INIS)

Jesus, Dosil P. de; Saito, Renata M.; Lago, Claudimir L. do

2004-01-01

An automated flow injection analysis system with piezoelectric detection is proposed as a sensitive and selective method for boron. The detector is an electrode-separated piezoelectric quartz crystal coated with N-methyl-D-glucamine-modified poly(epichlorohydrin). The film ability to retain boron allows the adjustment of the linear dynamic range and the sensitivity by varying the injected sample volume. In the present work, the sample volumes were varied from 0.5 to 5.0 mL. Among several ionic species, germanate is the only one that can interfere in the method. Nevertheless, it can be eliminated by addition of sulfide to the sample. The method was successfully applied to the determination of boron concentration in samples of natural water (from 1.71 to 309 μL -1 ) and products derived from grape juice (from 2.06 to 6.21 mg L -1 ). A pretreatment with hydrogen peroxide in alkaline medium was required due to the great amount of sugars in the grape products (author)

Regional cerebral blod flow studied by xenon-133. Intra-arterial injection studies and inhalation studies using emission tomography

DEFF Research Database (Denmark)

Lassen, N A

1980-01-01

.) technique is insensitive both to hyperemia and ischemia yielding essentially only a mean flow value. A new rapidly moving single photon tomograph following D. Kuhl's principle is presented applicable to Xe-133. Preliminary clinical data show that this technique is able to detect ischemic areas both with Xe......A survey of the Xenon-133 techniques for measurement of regional cerebral blood flow, rCBF, in man is presented. The intra-arterial Xe-133 injection method is very sensitive for detecting even small hyperemic areas, but cannot "see" smaller ischemic areas. The Xe-133 inhalation (or i.v. inj......-133 intra-arterial injection and with Xe-133 inhalation. The practical and economic advantages of Xe-133 or Xe-127 tomography over positron tomography for rCBF are discussed....

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.

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

Simultaneous detection of selenium by atomic fluorescence and sulfur by molecular emission by flow-injection hydride generation with on-line reduction for the determination of selenate, sulfate and sulfite

Energy Technology Data Exchange (ETDEWEB)

Tyson, J.F., E-mail: tyson@chem.umass.edu [Department of Chemistry, University of Massachusetts, 710 North Pleasant Street, Amherst, MA 01003 (United States); Palmer, C.D. [Lead Poisoning Trace Elements Laboratory, Wadsworth Center, New York State Department of Health, P.O. Box 509, Empire State Plaza, Albany, NY 12201-0509 (United States)

2009-10-12

An inductively coupled plasma atomic fluorescence spectrometry (ICP-AFS) instrument, was modified so that it was capable of monitoring transient chromatographic or flow-injection profiles and that sulfur molecular emission and selenium atomic fluorescence could be monitored simultaneously in an argon-hydrogen diffusion flame on a glass burner. The analytes were introduced as hydrogen selenide and hydrogen sulfide, generated on a flow-injection manifold. Selenate was reduced to hydride-forming selenite by microwave-assisted on-line reaction with hydrochloric acid, and sulfate, or sulfite, was reduced to hydride-forming sulfide by a mixture of hydriodic acid, acetic acid and sodium hypophosphite. The effects of the nature of reducing agent, flow rate, microwave power and coil length were studied. The limit of detection (3 s) for selenium was 10 {mu}g L{sup -1}, and for sulfide was 70 {mu}g L{sup -1} (200-{mu}L injection volume). The calibration was linear for selenium up to 2 mg L{sup -1} and to 10 mg L{sup -1} for sulfide. The throughput was 180 h{sup -1}. The three sulfur species could be differentiated on the basis of reactivity at various microwave powers.

A microfabricated electroosmotic pump coupled to a gas-diffusion microchip for flow injection analysis of ammonia

International Nuclear Information System (INIS)

Zhu, Zaifang; Lu, Joann J.; Liu, Shaorong; Almeida, M. Inês G. S.; Kolev, Spas D.; Pu, Qiaosheng

2015-01-01

We have microfabricated two functional components toward developing a microchip flow injection analysis (FIA) system, i.e., an open-channel electroosmotic pump and a gas-diffusion chip, consisting of two microfabricated glass wafers and a porous polytetrafluoroethylene membrane. This is the first application of gas-diffusion separation in a microchip FIA system. To demonstrate the feasibility of using these two components for performing gas-diffusion FIA, we have incorporated them together with a regular FIA injection valve and a capillary electrophoresis absorbance detector in a flow injection system for determination of ammonia in environmental water samples. This system has a limit of detection of 0.10 mg L −1 NH 3 , with a good repeatability (relative standard deviation of less than 5 % for 4.0 mg L −1 NH 3 ). Parameters affecting its performance are also discussed. (author)

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

A Reagentless Amperometric Formaldehyde-Selective Chemosensor Based on Platinized Gold Electrodes.

Science.gov (United States)

Demkiv, Olha; Smutok, Oleh; Gonchar, Mykhailo; Nisnevitch, Marina

2017-05-06

Fabrication and characterization of a new amperometric chemosensor for accurate formaldehyde analysis based on platinized gold electrodes is described. The platinization process was performed electrochemically on the surface of 4 mm gold planar electrodes by both electrolysis and cyclic voltamperometry. The produced electrodes were characterized using scanning electron microscopy and X-ray spectral analysis. Using a low working potential (0.0 V vs. Ag/AgCl) enabled an essential increase in the chemosensor's selectivity for the target analyte. The sensitivity of the best chemosensor prototype to formaldehyde is uniquely high (28180 A·M -1 ·m -2 ) with a detection limit of 0.05 mM. The chemosensor remained stable over a one-year storage period. The formaldehye-selective chemosensor was tested on samples of commercial preparations. A high correlation was demonstrated between the results obtained by the proposed chemosensor, chemical and enzymatic methods ( R = 0.998). The developed formaldehyde-selective amperometric chemosensor is very promising for use in industry and research, as well as for environmental control.

Amperometric cell for subcutaneous detection of hydrogen sulfide in anesthetized experimental animals

International Nuclear Information System (INIS)

Nagy, L; Nagy, G; Filotás, D; Boros, M; Pozsgai, G; Pintér, E

2014-01-01

Hydrogen sulfide (H 2 S) is a toxic gas. It has been recognized that H 2 S evolving in biochemical reactions in living organisms has an important role in different physiologic processes. Nowadays, H 2 S is known as an endogenous messenger molecule. Natural sulfurous spring water has been proved beneficial in the therapy of diseases of the skin and other organs (Boros et al 2013). In vivo real-time detection of local H 2 S concentration is an important but challenging task. We developed a two-electrode amperometric cell for selective subcutaneous detection of H 2 S in anesthetized mice. The cell is a small size implantable gas sensor containing a platinum disc anode and a silver cathode. The selectivity is provided by a membrane permeable only by gases. There is a buffered reversible electrochemical mediator solution in an oxidized form inside the cell. As gaseous H 2 S penetrates into the cell the mediator is reduced, and +0.4 V versus the reference is employed on the platinum working electrode. The reduced mediator is oxidized on the anode surface. The current provides an analytical signal representing the concentration of H 2 S. Appropriate shape, size and membrane material were selected, and optimal working parameters—such as mediator concentration, pH and cell voltage—were determined in vitro. The lower limit of detection in the stirred sample solution at pH = 5.5 was as small as 9.4  ×  10 −7  M and a dynamic concentration range of 0–6  ×  10 –4  M could be achieved. The detecting surfaces of the cell were covered with freshly dissected mouse skin to test dermal H 2 S permeability. In other experiments, the cell was implanted subcutaneously in an anesthetized mouse and the animal was submerged in a buffer solution containing different concentrations of H 2 S so that the skin surface over the sensor was covered by the solution. Measurements of subcutaneous H 2 S concentration were taken. The experiments clearly proved that H 2 S

A novel functionalisation process for glucose oxidase immobilisation in poly(methyl methacrylate) microchannels in a flow system for amperometric determinations.

Science.gov (United States)

Cerqueira, Marcos Rodrigues Facchini; Grasseschi, Daniel; Matos, Renato Camargo; Angnes, Lucio

2014-08-01

Different materials like glass, silicon and poly(methyl methacrylate) (PMMA) are being used to immobilise enzymes in microchannels. PMMA shows advantages such as its low price, biocompatibility and attractive mechanical and chemical properties. Despite this, the introduction of reactive functional groups on PMMA is still problematic, either because of the complex chemistry or extended reaction time involved. In this paper, a new methodology was developed to immobilise glucose oxidase (GOx) in PMMA microchannels, with the benefit of a rapid immobilisation process and a very simple route. The new procedure involves only two steps, based on the reaction of 5.0% (w/w) polyethyleneimine (PEI) with PMMA in a dimethyl sulphoxide medium, followed by the immobilisation of glucose oxidase using a solution containing 100U enzymes and 1.0% (v/v) glutaraldehyde. The reactors prepared in this way were evaluated by a flowing system with amperometric detection (+0.60V) based on the oxidation of the H2O2 produced by the reactor. The microreactor proposed here was able to work with high bioconversion and a frequency of 60 samples h(-1), with detection and quantification limits of 0.50 and 1.66µmol L(-1), respectively. Michaelis-Menten parameters (Vmax and KM) were calculated as 449±47.7nmol min(-1) and 7.79±0.98mmol. Statistical evaluations were done to validate the proposed methodology. The content of glucose in natural and commercial coconut water samples was evaluated using the developed method. Comparison with spectrophotometric measurements showed that both methodologies have a very good correlation (tcalculated, 0.05, 4=1.35

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.

Dual-phase gas-permeation flow-injection thermometric analysis for the determination of carbon dioxide.

Science.gov (United States)

Liu, S J; Tubino, M

1998-11-01

A flow-injection configuration based on a dual-phase gas-permeation system from a liquid donor to a gas acceptor stream with a thermistor flow-through detector is proposed for the direct analysis of the gas in the acceptor. This system was applied for the determination of carbon dioxide (in the form of carbonate) using the following chemical reaction: CO(2)(g)+2NH(3)(g)+H(2)O(g)=(NH(4))(2)CO(3)(s), with a linear response from 1x10(-3) to 50x10(-3) mol l(-1) of CO(3)(2-). Carbon dioxide was produced in the liquid donor and permeated into the gaseous acceptor stream of air/water vapor. The detection limit is 1x10(-3) mol l(-1) of carbonate, and a sampling frequency of 60 h(-1) is achieved with a relative standard deviation of 4.1% for replicate injections. The dual-phase gas-permeation flow-injection manifold, along with the membrane and phase separations, as well as the chemical reaction, provides enhanced selectivity when compared with the system employing a liquid acceptor stream, as serious interferents in this system, for instance, acetate and formate, among others, do not interfere in the proposed system.

The Use of Flow-Injection Analysis with Chemiluminescence Detection of Aqueous Ferrous Iron in Waters Containing High Concentrations of Organic Compounds

Directory of Open Access Journals (Sweden)

Carrick M. Eggleston

2009-06-01

Full Text Available An evaluation of flow-injection analysis with chemiluminescence detection (FIA-CL to quantify Fe2+(aq in freshwaters was performed. Iron-coordinating and/or iron-reducing compounds, dissolved organic matter (DOM, and samples from two natural water systems were used to amend standard solutions of Fe2+(aq. Slopes of the response curves from ferrous iron standards (1 – 100 nM were compared to the response curves of iron standards containing the amendments. Results suggest that FIA-CL is not suitable for systems containing ascorbate, hydroxylamine, cysteine or DOM. Little or no change in sensitivity occurred in solutions of oxalate and glycine or in natural waters with little organic matter.

A new amperometric method for rapid detection of Escherichia coli density using a self-assembled monolayer-based bienzyme biosensor

International Nuclear Information System (INIS)

Tang Hui; Zhang Wen; Geng Ping; Wang Qingjiang; Jin Litong; Wu Zirong; Lou Min

2006-01-01

A new amperometric method was developed for rapid detection of Escherichia coli (E. coli) density using a bienzyme biosensor. The bienzyme biosensor was fabricated based on the covalent immobilization of laccase and horseradish peroxidase (HRP) at indium tin oxide (ITO) electrode by (3-aminopropyl) triethoxysilane (APTES) monolayer. The bienzyme biosensor showed a high sensitivity in determination of the polyphenolic compounds, which was microbially generated from the salicylic acid (SA) added into the culture medium during the course of E. coli metabolism. Since the amount of polyphenolic compounds depends on E. coli density, the bienzyme biosensor was applied for the rapid and high sensitive detection of E. coli density after the E. coli solution was incubated in culture medium with salicylic acid for 2.5 h at 37 deg. C. By chronoamperometry, the amplified response current was obtained at the bienzyme biosensor, due to the substrate recycling of the polyphenolic compounds driven by bienzyme-catalyzed oxidation and electrochemical reduction. The amplified response current at the biosensor was linear with the E. coli density ranging from 1.6 x 10 3 to 1.0 x 10 7 cells/mL. The bienzyme biosensor could detect the E. coli density with a detection limit of 9.7 x 10 2 cells/mL within 3 h

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)

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

International Nuclear Information System (INIS)

Mi Jiaping; Li Yuanqian; Zhou Xiaoli; Zheng Bo; Zhou Ying

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%∼100.9% for Iron, 92.50%∼108.0% for Copper, 93.00%∼110.5% for Cobalt, respectively with relative standard deviation (R.S.D) of 1.1%∼12.1%. The sampling rate is 45 samples h -1 . The determination results of the food samples were in good agreement between the proposed method and ICP-AES

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.

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

Science.gov (United States)

Mi, Jiaping; Li, Yuanqian; Zhou, Xiaoli; Zheng, Bo; Zhou, Ying

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%~100.9% for Iron, 92.50%~108.0% for Copper, 93.00%~110.5% for Cobalt, respectively with relative standard deviation (R.S.D) of 1.1%~12.1%. The sampling rate is 45 samples h-1. The determination results of the food samples were in good agreement between the proposed method and ICP-AES.

Classification of Spanish white wines using their electrophoretic profiles obtained by capillary zone electrophoresis with amperometric detection.

Science.gov (United States)

Arribas, Alberto Sánchez; Martínez-Fernández, Marta; Moreno, Mónica; Bermejo, Esperanza; Zapardiel, Antonio; Chicharro, Manuel

2014-06-01

A method was developed for the simultaneous detection of eight polyphenols (t-resveratrol, (+)-catechin, quercetin and p-coumaric, caffeic, sinapic, ferulic, and gallic acids) by CZE with electrochemical detection. Separation of these polyphenols was achieved within 25 min using a 200 mM borate buffer (pH 9.4) containing 10% methanol as separation electrolyte. Amperometric detection of polyphenols was carried out with a glassy carbon electrode (GCE) modified with a multiwalled carbon nanotubes (CNT) layer obtained from a dispersion of CNT in polyethylenimine. The excellent electrochemical properties of this modified electrode allowed the detection and quantification of the selected polyphenols in white wines without any pretreatment step, showing remarkable signal stability despite the presence of potential fouling substances in wine. The electrophoretic profiles of white wines, obtained using this methodology, have proven to be useful for the classification of these wines by means of chemometric multivariate techniques. Principal component analysis and discriminant analysis allowed accurate classification of wine samples on the basis of their grape varietal (verdejo and airén) using the information contained in selected zones of the electropherogram. The utility of the proposed CZE methodology based on the electrochemical response of CNT-modified electrodes appears to be promising in the field of wine industry and it is expected to be successfully extended to classification of a wider range of wines made of other grape varietals. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

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.

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

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.......g., soils, sediments, sludges), and thus, ascertaining the potential mobility, bioavailability and eventual impact of anthropogenic elements on biota [2]. In this context, the principles of sequential injection-microcolumn extraction (SI-MCE) for dynamic fractionation are explained in detail along...

Adaptation of a load-inject valve for a flow injection chemiluminescence system enabling dual-reagent injection enhances understanding of environmental Fenton chemistry

International Nuclear Information System (INIS)

Jones, Matthew R.; Nightingale, Philp D.; Turner, Suzanne M.; Liss, Peter S.

2013-01-01

Graphical abstract: -- Highlights: •Measurement of multiple components of Fenton chemistry; Fe(II) and H 2 O 2 . •Rapid, quasi-simultaneous analysis enables calculation of environmental kinetics. •Low, nano to pico-molar detection limits with dual analyte analysis. •Able to measure complex matrix samples – organically enriched seawater. •Low cost system with appreciable sensitivity compared to single analyte analysis. -- Abstract: Environmental Fenton chemistry has been poorly constrained within the marine environment at a multi-component level. A simple, unique, reconfiguration of a flow-injection analytical system combined with luminol chemiluminescence allows quasi-simultaneously the measurement, using a single load-inject valve and a single photon multiplier tube, of reduced iron, Fe(II), and hydrogen peroxide. The system enables rapid, every 22 s, measurements with good accuracy at environmentally relevant concentrations, less than 5% relative standard deviations on both a 5 nM Fe(II) standard and a 60 nM hydrogen peroxide standard. Limits of detection were as low as 40 pM Fe(II) and 100 pM hydrogen peroxide. The system showed excellent capability by measuring from within an organic rich seawater the photochemically induced production of Fe(II) and hydrogen peroxide and their subsequent cycling and Fenton like interactions

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.

Non-local electrical spin injection and detection in germanium at room temperature

Science.gov (United States)

Rortais, F.; Vergnaud, C.; Marty, A.; Vila, L.; Attané, J.-P.; Widiez, J.; Zucchetti, C.; Bottegoni, F.; Jaffrès, H.; George, J.-M.; Jamet, M.

2017-10-01

Non-local carrier injection/detection schemes lie at the very foundation of information manipulation in integrated systems. This paradigm consists in controlling with an external signal the channel where charge carriers flow between a "source" and a well separated "drain." The next generation electronics may operate on the spin of carriers in addition to their charge and germanium appears as the best hosting material to develop such a platform for its compatibility with mainstream silicon technology and the predicted long electron spin lifetime at room temperature. In this letter, we demonstrate injection of pure spin currents (i.e., with no associated transport of electric charges) in germanium, combined with non-local spin detection at 10 K and room temperature. For this purpose, we used a lateral spin valve with epitaxially grown magnetic tunnel junctions as spin injector and spin detector. The non-local magnetoresistance signal is clearly visible and reaches ≈15 mΩ at room temperature. The electron spin lifetime and diffusion length are 500 ps and 1 μm, respectively, the spin injection efficiency being as high as 27%. This result paves the way for the realization of full germanium spintronic devices at room temperature.

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)

Flow-injection fluorimetric determination of menadione using on-line photo-reduction in micellar media

Energy Technology Data Exchange (ETDEWEB)

Perez-Ruiz, Tomas; Martinez-Lozano, Carmen; Tomas, Virginia; Martin, Jesus

2004-07-01

A very sensitive fluorimetric method for the determination of menadione using a flow injection system is proposed. The method is based on the on-line reduction of menadione in dodecylsulphate micelles upon irradiation with UV light. The strong fluorescence of the reduced menadione in micellar medium is measured at 410 nm with excitation at 340 nm. The method shows a linear range between 2.42 and 245 ng ml{sup -1} and a limit of detection of 0.18 ng ml{sup -1}. The sample throughput was 90 injections per hour. The applicability of the assay was demonstrated by analysing this vitamin in commercial pharmaceutical preparations.

Flow-injection fluorimetric determination of menadione using on-line photo-reduction in micellar media

International Nuclear Information System (INIS)

Perez-Ruiz, Tomas; Martinez-Lozano, Carmen; Tomas, Virginia; Martin, Jesus

2004-01-01

A very sensitive fluorimetric method for the determination of menadione using a flow injection system is proposed. The method is based on the on-line reduction of menadione in dodecylsulphate micelles upon irradiation with UV light. The strong fluorescence of the reduced menadione in micellar medium is measured at 410 nm with excitation at 340 nm. The method shows a linear range between 2.42 and 245 ng ml -1 and a limit of detection of 0.18 ng ml -1 . The sample throughput was 90 injections per hour. The applicability of the assay was demonstrated by analysing this vitamin in commercial pharmaceutical preparations

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...

Modified and reverse radiometric flow injection analysis

Energy Technology Data Exchange (ETDEWEB)

Myint, U; Ba, H; Khin, M M; Aung, K; Thida, [Yangon Univ. (Myanmar). Dept. of Chemistry; Toelgyessy, J [Slovak Technical Univ., Bratislava (Slovakia). Dept. of Environmental Science

1994-06-01

Determination of [sup 137]Cs and [sup 60]Co by using modified and reverse radiometric flow injection analysis is described. Two component RFIA was also realized using [sup 60]Co and [sup 137]Cs radionuclides. (author) 2 refs.; 5 figs.

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.

DETERMINAÇÃO RÁPIDA E SIMPLES DE CITRATO DE SILDENAFILA (VIAGRA® E GENÉRICOS EMPREGANDO ELETRODO IMPRESSO DE CARBONO EM SISTEMAS FIA E BIA COM DETECÇÃO AMPEROMÉTRICA

Directory of Open Access Journals (Sweden)

Rafael S. Backes

Full Text Available This work presents two amperometric methods for Sildenafil Citrate (SC determination in erectile dysfunction drugs (Viagra® and Generics, using Batch Injection Analysis (BIA and Flow Injection Analysis (FIA systems with a cell for Screen Printed Electrodes (SPE. In Britton- Robinson buffer solution (pH 2, the SC presented an irreversible anodic peak at around +1.0 V vs. Ag pseudo-reference electrode, using five different working electrodes of commercial SPE. The carbon SPE (unmodified was selected as the best working electrode, providing good sensitivity, precision and low-cost. The SC amperometric detection for two proposed methods was performed at +1.1 V. The best conditions for SC determination by hydrodynamic systems were obtained through injection volumes of 50 and 150 µL at flow rates of 100 and 75 µL s-1, for BIA and FIA respectively. In these conditions, BIA system showed the best sensitivity (0.188 µA mol-1 L and theoretical analytical frequency (360 h-1 for SC determination. The repeatability studies were similar for both systems with relative standard deviation of approximately 3.0%. The SC analyses in pharmaceutical samples obtained by two proposed methods were compared to HPLC-UV method.

Indirect flow injection determination of N-acetyl-L-cysteine using cerium(IV) and ferroin

International Nuclear Information System (INIS)

Vieira, Heberth Juliano; Fatibello-Filho, Orlando

2005-01-01

An indirect flow injection spectrophotometric procedure is proposed for the determination of N-acetyl-L-cysteine in pharmaceutical formulations. In this system, ferroin ([Fe(II)-(fen) 2 ] 2+ ) in excess, with a strong absorption at 500 nm, is oxidized by cerium(IV) yielding cerium(III) and [Fe(III)-(fen) 2 ] 3+ (colorless), thus producing a baseline. When N-acetyl-L-cysteine solution is introduced into the flow injection system, it reacts with cerium(IV) increasing the analytical signal in proportion to the drug concentration. Under optimal experimental conditions, the linearity of the analytical curve for N-acetyl-L-cysteine ranged from 6.5x10 -6 to 1.3x10 -4 mol L -1 . The detection limit was 5.0x10 -6 mol L -1 and recoveries between 98.0 and 106% were obtained. The sampling frequency was 60 determinations per hour and the RSD was smaller than 1.4% for 2.2x10 -5 mol L -1 N-acetyl-L-cysteine. (author)

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 ...

Fuel cell-powered microfluidic platform for lab-on-a-chip applications: Integration into an autonomous amperometric sensing device.

Science.gov (United States)

Esquivel, J P; Colomer-Farrarons, J; Castellarnau, M; Salleras, M; del Campo, F J; Samitier, J; Miribel-Català, P; Sabaté, N

2012-11-07

The present paper reports for the first time the integration of a microfluidic system, electronics modules, amperometric sensor and display, all powered by a single micro direct methanol fuel cell. In addition to activating the electronic circuitry, the integrated power source also acts as a tuneable micropump. The electronics fulfil several functions. First, they regulate the micro fuel cell output power, which off-gas controls the flow rate of different solutions toward an electrochemical sensor through microfluidic channels. Secondly, as the fuel cell powers a three-electrode electrochemical cell, the electronics compare the working electrode output signal with a set reference value. Thirdly, if the concentration measured by the sensor exceeds this threshold value, the electronics switch on an integrated organic display. This integrated approach pushes forward the development of truly autonomous point-of-care devices relying on electrochemical detection.

A novel approach for determination of free fatty acids in vegetable oils by a flow injection system with manual injection.

Science.gov (United States)

Ayyildiz, H Filiz; Kara, Huseyin; Sherazi, S T H

2011-12-01

A non-aqueous flow injection method for determining free fatty acid (FFA) content in corn and sunflower oil samples was developed. A single-line manifold system was built by modification of an HPLC for flow injection analysis (FIA). Without pre-treatment, oil samples were injected into a n-propanol solution containing KOH and phenolphthalein (PHP). The main parameters, such as flow rate of carrier phase, length, geometry, inner diameters of the coils and reagent concentration were all optimized. The proposed FIA method was validated for precision, accuracy, linear region, limit of detection (LOD) and limit of quantification (LOQ). The intra- and inter-day measurements of the precision of the method were found to be within the limits of acceptance criteria (RSD analyst. The linear concentration range was calculated as 0.09-1.50 and 0.07-1.40 FFA% for corn and sunflower oils, correspondingly. The LOD and LOQ were found to be 7.53 × 10(-4)-2.28 × 10(-3) oleic acid % and 7.11 × 10(-4)-2.23 × 10(-3) oleic acid % for corn and sunflower oils, respectively. The results were compared with those obtained by the AOCS (Ca-5a-40) method using statistical t and F tests, and a significant difference was not observed between the methods at a 95% confidence level. The proposed method is suitable for quality control of routine applications due to its simplicity, high sample throughput, and economy of solvents and sample, offering considerable promise as a low cost analytical system that needs minimum human intervention over long periods of time.

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

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.)

Charge Injection and Current Flow in Organic Light Emitting Diodes

Science.gov (United States)

Smith, D. L.; Davids, P. S.; Heller, C. M.; Crone, B. K.; Campbell, I. H.; Barashkov, N. N.; Ferraris, J. P.

1997-03-01

We present a comparison between device model calculations and current-voltage measurements for a series of organic LED structures. The Schottky energy barrier of an injecting contact is systematically varied by changing the metal used to form that contact. The current-voltage characteristics of the structures are described using a device model that considers charge injection, transport and space charge effects in the low mobility organic material. Charge injection into the organic material is controlled by the Schottky energy barrier of the metal/organic contact. For Schottky energy barriers greater than about 0.4 eV injection into the organic material is the principal limitation to current flow. In this regime the net injected charge density is relatively small, the electric field in the structure is nearly uniform, and space charge effects are not important. For smaller energy barriers relatively large charge densities are injected into the organic material and space charge effects become the dominant limit to current flow. The measured current-voltage characteristics are quantitatively described by the device model using Schottky barrier values independently determined by internal photoemission and electroabsorption measurements.

Amperometric detection of glucose in fruit juices with polypyrrole-based biosensor with an integrated permselective layer for exclusion of interferences.

Science.gov (United States)

Ayenimo, Joseph G; Adeloju, Samuel B

2017-08-15

A novel polypyrrole (PPy)-based bilayer amperometric glucose biosensor integrated with a permselective layer has been developed for detection of glucose in the presence of interferences. It comprises of a PPy-GOx film grown, in the absence of electrolyte, as an inner layer, and a permselective PPy-Cl film as an outer layer. The PPy-GOx/PPy-Cl bilayer biosensor was effective in rejecting 98% of ascorbic acid and 100% of glycine, glutamic acid and uric acid. With an outer layer thickness of 6.6nm, the bilayer biosensor gave nearly identical glucose response to that of a single layer PPy-GOx biosensor. The biosensor also exhibited good reproducibility (1.9% rsd, n=10), high stability (more than 2months), wide linear range (0.5-24mM), low K m (8.4mM), high I max (77.2μAcm -2 ), low detection limit (26.9μM) and good sensitivity (3.5μAcm -2 mM -1 ). The bilayer biosensor was successfully employed for glucose determination in various fruit juices. Copyright © 2017 Elsevier Ltd. All rights reserved.

A dilute-and-shoot flow-injection tandem mass spectrometry method for quantification of phenobarbital in urine.

Science.gov (United States)

Alagandula, Ravali; Zhou, Xiang; Guo, Baochuan

2017-01-15

Liquid chromatography/tandem mass spectrometry (LC/MS/MS) is the gold standard of urine drug testing. However, current LC-based methods are time consuming, limiting the throughput of MS-based testing and increasing the cost. This is particularly problematic for quantification of drugs such as phenobarbital, which is often analyzed in a separate run because they must be negatively ionized. This study examined the feasibility of using a dilute-and-shoot flow-injection method without LC separation to quantify drugs with phenobarbital as a model system. Briefly, a urine sample containing phenobarbital was first diluted by 10 times, followed by flow injection of the diluted sample to mass spectrometer. Quantification and detection of phenobarbital were achieved by an electrospray negative ionization MS/MS system operated in the multiple reaction monitoring (MRM) mode with the stable-isotope-labeled drug as internal standard. The dilute-and-shoot flow-injection method developed was linear with a dynamic range of 50-2000 ng/mL of phenobarbital and correlation coefficient > 0.9996. The coefficients of variation and relative errors for intra- and inter-assays at four quality control (QC) levels (50, 125, 445 and 1600 ng/mL) were 3.0% and 5.0%, respectively. The total run time to quantify one sample was 2 min, and the sensitivity and specificity of the method did not deteriorate even after 1200 consecutive injections. Our method can accurately and robustly quantify phenobarbital in urine without LC separation. Because of its 2 min run time, the method can process 720 samples per day. This feasibility study shows that the dilute-and-shoot flow-injection method can be a general way for fast analysis of drugs in urine. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Advancement of In-Flight Alumina Powder Spheroidization Process with Water Droplet Injection Using a Small Power DC-RF Hybrid Plasma Flow System

Science.gov (United States)

Jang, Juyong; Takana, Hidemasa; Park, Sangkyu; Nishiyama, Hideya

2012-09-01

The correlation between plasma thermofluid characteristics and alumina powder spheroidization processes with water droplet injection using a small power DC-RF hybrid plasma flow system was experimentally clarified. Micro-sized water droplets with a low water flow rate were injected into the tail of thermal plasma flow so as not to disturb the plasma flow directly. Injected water droplets were vaporized in the thermal plasma flow and were transported upstream in the plasma flow to the torch by the backflow. After dissociation of water, the production of hydrogen was detected by the optical emission spectroscopy in the downstream RF plasma flow. The emission area of the DC plasma jet expanded and elongated in the vicinity of the RF coils. Additionally, the emission area of RF plasma flow enlarged and was visible as red emission in the downstream RF plasma flow in the vicinity below the RF coils due to hydrogen production. Therefore, the plasma flow mixed with produced hydrogen increased the plasma enthalpy and the highest spheroidization rate of 97% was obtained at a water flow rate of 15 Sm l/min and an atomizing gas flow rate of 8 S l/min using a small power DC-RF hybrid plasma flow system.

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

The Co-axial Flow of Injectable Solid Hydrogels with Encapsulated Cells

Science.gov (United States)

Stewart, Brandon; Pochan, Darrin; Sathaye, Sameer

2013-03-01

Hydrogels are quickly becoming an important biomaterial that can be used for the safe, localized injection of cancer drugs, the injection of stem cells into areas of interest or other biological applications. Our peptides can be self-assembled in a syringe where they form a gel, sheared by injection and, once in the body, immediately reform a localized pocket of stiff gel. My project has been designed around looking at the possibility of having a co-axial strand, in which one gel can surround another. This co-axial flow can be used to change the physical properties of our gel during injection, such as stiffening our gel using hyaluronic acid or encapsulating cells in the gel and surrounding the gel with growth medium or other biological factors. Rheology on hyaluron stiffened gels and cells encapsulated in gels was performed for comparison to the results from co-axial flow. Confocal microscopy was used to examine the coaxial gels after flow and to determine how the co-axial nature of the gels is affected by the concentration of peptide.

Amperometric Noise at Thin Film Band Electrodes

DEFF Research Database (Denmark)

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

2012-01-01

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...

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.

Rhodium-Prussian Blue modified carbon paste electrode (Rh-PBMCPE for amperometric detection of hydrogen peroxide

Directory of Open Access Journals (Sweden)

Ivama Viviane Midori

2003-01-01

Full Text Available Prussian Blue was deposited at carbon paste electrode surface from a solution containing 2.0 x 10-3 mol L-1 K3[Fe(CN6], 3.0 x 10-3 mol L-1 FeCl3 and 1.0 x 10-2 mol L-1 HCl using two controlled potentials. To improve the stability of the modified electrode it was 50 times cycled in a solution containing 1.0 x 10-3 mol L-1 RhCl3, 0.50 mol L-1 KCl and 0.010 mol L-1 HCl in the potential range from - 0.40 V to 0.60 V at 60 mV s-1. The Rh - Prussian Blue carbon paste modified electrode (Rh-PBMCPE showed good stability during amperometric catalytic determination of H2O2 at 0.040 V, without ascorbic and uric acids interferences. The current changed linearly with H2O2 concentrations in the range of 5.0 x 10-5 - 8.6 x 10-4 mol L-1. The estimated detection limit was 2.8 x 10-5 mol L-1 with sensibility changing from 1.32 to 0.96 A mol-1 L cm-2 along five days (180 determinations.

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.

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.

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.

Manual and Flow-Injection Detection/Quantification of Polyquaterniums via Fully Reversible Polyion-Sensitive Polymeric Membrane-Based Ion-Selective Electrodes.

Science.gov (United States)

Ferguson, Stephen A; Meyerhoff, Mark E

2017-10-27

The detection of four different polyquaterniums (PQs) using a fully reversible potentiometric polyion sensor in three different detection modes is described. The polyion sensing "pulstrodes" serve as the detector for direct dose-response experiments, beaker titrations, and in a flow-injection analysis (FIA) system. Direct polycation response toward PQ-2, PQ-6, PQ-10, and poly(2-methacryloxyethyltrimethylammonium) chloride (PMETAC) yields characteristic information about each PQ species (e.g., relative charge densities, etc.) via syringe pump addition of each PQ species to a background electrolyte solution. Quantitative titrations are performed using a syringe pump to deliver heparin as the polyanion titrant to quantify all four PQs at μg/mL levels. Both the direct and indirect methods incorporate the use of a three-electrode system including counter, double junction reference, and working electrodes. The working electrode possesses a plasticized poly(vinyl chloride) (PVC) membrane containing the neutral lipophilic salt of dinonylnaphthalenesulfonate (DNNS - ) tridodecylmethylammonium (TDMA + ). Further, the titration method is shown to be useful to quantify PQ-6 levels in recreational swimming pool water collected in Ann Arbor, MI. Finally, a FIA system equipped with a pulstrode detector is used to demonstrate the ability to potentially quantify PQ levels via a more streamlined and semiautomated testing platform.

A novel automatic flow method with direct-injection photometric detector for determination of dissolved reactive phosphorus in wastewater and freshwater samples.

Science.gov (United States)

Koronkiewicz, Stanislawa; Trifescu, Mihaela; Smoczynski, Lech; Ratnaweera, Harsha; Kalinowski, Slawomir

2018-02-12

The novel automatic flow system, direct-injection detector (DID) integrated with multi-pumping flow system (MPFS), dedicated for the photometric determination of orthophosphates in wastewater and freshwater samples is for the first time described. All reagents and the sample were injected simultaneously, in counter-current into the reaction-detection chamber by the system of specially selected for this purpose solenoid micro-pumps. The micro-pumps provided good precision and accuracy of the injected volumes. For the determination of orthophosphates, the molybdenum blue method was employed. The developed method can be used to detect orthophosphate in the range 0.1-12 mg L -1 , with the repeatability (RSD) about 2.2% at 4 mg L -1 and a very high injection throughput of 120 injections h -1 . It was possible to achieve a very small consumption of reagents (10 μL of ammonium molybdate and 10 μL of ascorbic acid) and sample (20 μL). The volume of generated waste was only 440 μL per analysis. The method has been successfully applied, giving a good accuracy, to determination of orthophosphates in complex matrix samples: treated wastewater, lake water and reference sample of groundwater. The developed system is compact, small in both size and weight, requires 12 V in supply voltage, which are desirable for truly portable equipment used in routine analysis. The simplicity of the system should result in its greater long-time reliability comparing to other flow methods previously described.

Stopped-flow injection spectrophotometric method for determination of chlorate in soil

OpenAIRE

Jaroon Jakmunee

2008-01-01

A stopped-flow injection (FI) spectrophotometric procedure based on iodometric reaction for the determination of chlorate has been developed. Standard/sample was injected into a stream of potassium iodide solution and then merged with a stream of hydrochloric acid solution to produce triiodide. By stopping the flow while the sample zone is being in a mixing coil, a slow reaction of chlorate with iodide in acidic medium was promoted to proceed with minimal dispersion of the triiodide product z...

Multianalyte detection using a capillary-based flow immunosensor.

Science.gov (United States)

Narang, U; Gauger, P R; Kusterbeck, A W; Ligler, F S

1998-01-01

A highly sensitive, dual-analyte detection system using capillary-based immunosensors has been designed for explosive detection. This model system consists of two capillaries, one coated with antibodies specific for 2,4,6-trinitrotoluene (TNT) and the other specific for hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) combined into a single device. The fused silica capillaries are prepared by coating anti-TNT and anti-RDX antibodies onto the silanized inner walls using a hetero-bifunctional crosslinker. After immobilization, the antibodies are saturated with a suitable fluorophorelabeled antigen. A "T" connector is used to continuously flow the buffer solution through the individual capillaries. To perform the assay, an aliquot of TNT or RDX or a mixture of the two analytes is injected into the continuous flow stream. In each capillary, the target analyte displaces the fluorophore-labeled antigen from the binding pocket of the antibody. The labeled antigen displaced from either capillary is detected downstream using two portable spectrofluorometers. The limits of detection for TNT and RDX in the multi-analyte formate are 44 fmol (100 microliters of 0.1 ng/ml TNT solution) and 224 fmol (100 microliters of 0.5 ng/ml RDX solution), respectively. The entire assay for both analytes can be performed in less than 3 min.

A green synthetic strategy of nickel hexacyanoferrate nanoparticals supported on the graphene substrate and its non-enzymatic amperometric sensing application

Science.gov (United States)

xue, Zhonghua; He, Nan; Rao, Honghong; Hu, Chenxian; Wang, Xiaofen; Wang, Hui; Liu, Xiuhui; Lu, Xiaoquan

2017-02-01

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.

Flow injection spectrofluorimetric method for the determination of cadmium

International Nuclear Information System (INIS)

Bo Tang; Taixing Yue; Lili Zhang; Junsen Wu; Zhenzhen Chen

2004-01-01

A novel fluorescent reagent, o-vanillin furoylhydrazone (OVFH), was synthesized, and its infrared spectrum, elemental analysis and dissociation constant are reported. The reaction between Cd 2+ and OVFH produces an intensely fluorescent complex in ethanol-water medium of pH 10.00, and this finding has led to a simple, rapid, and sensitive flow injection (FI) spectrofluorimetric method for on-line determination of Cd 2+ . Under the optimum experimental conditions, the fluorescent complex had excitation and emission maxima at 393 and 494 nm, respectively. The linear range is from 0.025 to 8.0 μg mL -1 of Cd 2+ , the detection limit is 7.6 μg L -1 and the maximum sampling rate is 80 h -1 . The effect of interferences was studied. The method was successfully applied to the determination of cadmium in environmental samples. (author)

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.

Application of L-lactate-cytochrome c-oxidoreductase for development of amperometric biosensor for L-lactate determination

Directory of Open Access Journals (Sweden)

Dzyadevych S. V.

2009-06-01

Full Text Available Aim. Development of amperometric biosensor based on L-lactate-cytochrome c-oxidoreductase (flavocytochrome b2, FC b2 for lactate determination. Methods. All experiments were performed using the amperometric method of detection. The methods of electrochemical polymerization and immobilization in glutaraldehyde vapors were used for FC b2 immobilization on the surface of electrodes. Results. The FC b2 preparation, which demonstrated the best operational characteristics after immobilization in poly (3,4-ethylen dioxythiophene, was selected. The selectivity, operational and storage stability, and pH-optimum for operation of the created biosensor were determined. The analysis of L-lactate in the model solutions and wine samples was carried outusing the developed biosensor. Conclusion. The FC b2-based biosensor due to its high stability can be effectively used for lactate determination in blood and other liquids containing no ethanol. After the selectivity optimization, the devise can be also applied for wine analysis.

Interaction of Liquid Film Flow of Direct Vessel Injection Under the Cross Directional Gas Flow

Energy Technology Data Exchange (ETDEWEB)

Kim, Han-sol; Lee, Jae-young [Handong Global University, Pohang (Korea, Republic of); Euh, Dong-Jin [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2015-10-15

In order to obtain a proper scaling law of the flow, local information of the flow was investigated experimentally and also numerically. A series of experiments were conducted in the 1/20 modified linear scaled plate type test rig to analyze a liquid film from ECC water injection through the DVI nozzle to the downcomer wall. The present study investigates liquid film flow generated in a downcomer of direct vessel injection (DVI) system which is employed as an emergency core cooling (ECC) system during a loss of coolant accident in the Korea nuclear power plant APR1400. During the late reflooding, complicated multi-phase flow phenomena including the wavy film flow, film breakup, entrainment, liquid film shift due to interfacial drag and gas jet impingement occur. A confocal chromatic sensor was used to measure the local instantaneous liquid film thickness and a hydraulic jump in the film flow and boundaries of the film flow. It was found that CFD analysis results without surface tension model showed some difference with the data in surface tension dominated flow region. For the interaction between a liquid film and gas shear flow, CFD results make a good agreement with the real liquid film dynamics in the case of low film Reynolds number or low Weber number flow. In the 1/20 scaled plate type experiment and simulation, the deformed spreading profile results seem to accord with each other at the relatively low We and Re regime.

A new approach to flow-batch titration. A monosegmented flow titrator with coulometric reagent generation and potentiometric or biamperometric detection.

Science.gov (United States)

de Aquino, Emerson Vidal; Rohwedder, Jarbas José Rodrigues; Pasquini, Celio

2006-11-01

Monosegmented flow analysis (MSFA) has been used as a flow-batch system to produce a simple, robust, and mechanized titrator that enables true titrations to be performed without the use of standards. This paper also introduces the use of coulometry with monosegmented titration by proposing a versatile flow cell. Coulometric generation of the titrand is attractive for titrations performed in monosegmented systems, because the reagent can be added without increasing the volume of sample injected. Also, biamperomeric and potentiometric detection of titration end-points can increase the versatility of the monosegmented titrator. The cell integrates coulometric generation of the titrand with detection of end-point by potentiometry or biamperometry. The resulting titrator is a flow-batch system in which the liquid monosegment, constrained by the interfaces of the gaseous carrier stream, plays the role of a sample of known volume to be titrated. The system has been used for determination of ascorbic acid, by coulometric generation of I2 with biamperometric detection, and for determination of Fe(II), by coulometric generation of Ce(IV) with potentiometric detection of the end-point, both in feed supplements.

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

Radiometric flow injection analysis with an ASIA (Ismatec) analyzer

Energy Technology Data Exchange (ETDEWEB)

Myint, U; Win, N; San, K; Han, B; Myoe, K M [Yangon Univ. (Myanmar). Dept. of Chemistry; Toelgyessy, J [Slovak Technical Univ., Bratislava (Slovakia). Dept. of Environmental Science

1994-07-01

Radiometric Flow Injection Analysis of a radioactive ([sup 131]I) sample is described. For analysis an ASIA (Ismatec) analyzer with a NaI(Tl) scintillation detector was used. (author) 5 refs.; 3 figs.

An amperometric biosensor for glucose detection from glucose oxidase immobilized in polyaniline-polyvinylsulfonate-potassium ferricyanide film.

Science.gov (United States)

Arslan, Fatma; Beskan, Umut

2014-08-01

In this study, a novel amperometric glucose biosensor with immobilization of glucose oxidase on electrochemically polymerized polyaniline-polyvinylsulphonate-potassium ferricyanide (Pani-Pvs-Fc) films has been accomplished via the entrapment technique. Potassium ferricyanide was used as the mediator. Determination of glucose was carried out by the oxidation of potassium ferrocyanide at 0.3 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 the operational stability of the enzyme electrode were also studied.

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......, programmable from the microcomputer, to control the sample volume. No pre-treatment of the samples is necessary. The limit of detection is 0.14 mg l–1, and only small amounts of serum (

Cross-flow analysis of injection wells in a multilayered reservoir

Directory of Open Access Journals (Sweden)

Mohammadreza Jalali

2016-09-01

Natural and forced cross-flow is modeled for some injection wells in an oil reservoir located at North Sea. The solution uses a transient implicit finite difference approach for multiple sand layers with different permeabilities separated by impermeable shale layers. Natural and forced cross-flow rates for each reservoir layer during shut-in are calculated and compared with different production logging tool (PLT measurements. It appears that forced cross-flow is usually more prolonged and subject to a higher flow rate when compared with natural cross-flow, and is thus worthy of more detailed analysis.

The effects of arbitrary injection angle and flow conditions on venturi-jet mixer

Directory of Open Access Journals (Sweden)

Sundararaj S.

2012-01-01

Full Text Available This paper describes the effect of jet injection angle, cross flow Reynolds number and velocity ratio on entrainment and mixing of jet with incompressible cross flow in venturi-jet mixer. Five different jet injection angles 45o, 60o, 90o, 125o, 135o are tested to evaluate the entrainment of jet and mixing performances of the mixer. Tracer concentration along the downstream of the jet injection, cross flow velocity, jet velocity and pressure drop across the mixer are determined experimentally to characterize the mixing performance of the mixer. The experiments show that the performance of a venturi-jet-mixer substantially improves at high injection angle and can be augmented still by increasing velocity ratio. The jet deflects much and penetrates less in the cross flow as the cross flow Reynolds number is increased. The effect could contribute substantially to the better mixing index with moderate pressure drop. Normalized jet profile, concentration decay, jet velocity profile are computed from equations of conservation of mass, momentum and concentration written in natural co-ordinate systems. The comparison between the experimental and numerical results confirms the accuracy of the simulations. Correlations for jet trajectory and entrainment ratio of the mixer are obtained by multivariate-linear regression analysis using power law.

Flow regime analysis for fluid injection into a confined aquifer: implications for CO2 sequestration

Science.gov (United States)

Guo, B.; Zheng, Z.; Celia, M. A.; Stone, H.

2015-12-01

Carbon dioxide injection into a confined saline aquifer may be modeled as an axisymmetric two-phase flow problem. Assuming the two fluids segregate in the vertical direction due to strong buoyancy, and neglecting capillary pressure and miscibility, the lubrication approximation leads to a nonlinear advection-diffusion equation that describes the evolution of the sharp fluid-fluid interface. The flow behaviors in the system are controlled by two dimensionless groups: M, the viscosity ratio of the displaced fluid relative to injected fluid, and Γ , the gravity number, which represents the relative importance of buoyancy and fluid injection. Four different analytical solutions can be derived as the asymptotic approximations, representing specific values of the parameter pairs. The four solutions correspond to: (1) Γ 1; and (4) Γ >> 1, any M values. The first two of these solutions are new, while the third corresponds to the solution of Nordbotten and Celia (2006) for confined injections and the fourth corresponds to the solution of (Lyle et al., 2005) for gravity currents in an unconfined aquifer. Overall, the various axisymmetric flows can be summarized in a Γ-M regime diagram with five distinct dynamic behaviors including the four asymptotic regimes and an intermediate regime (Fig. 1). Data from a number of CO2 injection sites around the world can be used to compute the two dimensionless groups Γ and M associated with each injection. When plotted on the regime diagram, these values show the flow behavior for each injection and how the values vary from site to site. For all the CO2 injections, M is always larger than 1, while Γ can range from 0.01 up to 100. The pairs of (Γ, M) with lower Γ values correspond to solution (3), while the ones with higher Γ values can move up to the intermediate regime and the flow regime for solution (4). The higher values of Γ correspond to pilot-scale injections with low injection rates; most industrial-scale injection

Alginate copper oxide nano-biocomposite as a novel material for amperometric glucose biosensing

Energy Technology Data Exchange (ETDEWEB)

Buk, Vuslat [Ankara University, Department of Chemistry, Science Faculty, Tandoğan, Ankara 06100 (Turkey); Tyndall National Institute, University College Cork, Dyke Parade, Cork (Ireland); Emregul, Emel, E-mail: eemregul@yahoo.com [Ankara University, Department of Chemistry, Science Faculty, Tandoğan, Ankara 06100 (Turkey); Emregul, Kaan Cebesoy [Ankara University, Department of Chemistry, Science Faculty, Tandoğan, Ankara 06100 (Turkey)

2017-05-01

A novel amperometric glucose biosensor based on alginate-CuO nano-biocomposite and glucose oxidase (GOD) film was developed and characterized. The properties of the alginate-CuO-GOD film were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Amperometric measurements were employed to characterize the analytical performance of the biosensor. Several parameters including amount of alginate, concentration of GOD and cross-linkers, amount of CuO nanoparticles, and effect of pH were studied and optimized. Under optimal conditions, the developed alginate-CuO-GOD biosensor was shown to have two linear ranges; from 0.04 mM to 3 mM (with a correlation coefficient of 0.9996 and the sensitivity of 30.443 μA mM{sup −1} cm{sup −2}) and from 4 mM to 35 mM (with a correlation coefficient of 0.9994 and the sensitivity of 7.205 μA mM{sup −1} cm{sup −2}). The overall detection limit was estimated to be 1.6 μM (signal-to-noise ratio of 3) and the K{sub m} value of 2.82 mM. The biosensor exhibited rather good performance with long-term stability (remainder of activity is 78% after 15 days) and significant specificity for glucose when compared to possible interfering molecules such as ascorbic acid, uric acid and acetaminophen. - Highlights: • An amperometric biosensor was constructed by using Alginate-CuO nano-biocomposite complexed with Glucose Oxidase • Glucose Oxidase immobilized to the surface via cross-linking. • Alginate-CuO film was characterized by SEM and FTIR. • The biosensor exhibits excellent analytical performance to glucose with a wide linear range and high sensitivity.

Alginate copper oxide nano-biocomposite as a novel material for amperometric glucose biosensing

International Nuclear Information System (INIS)

Buk, Vuslat; Emregul, Emel; Emregul, Kaan Cebesoy

2017-01-01

A novel amperometric glucose biosensor based on alginate-CuO nano-biocomposite and glucose oxidase (GOD) film was developed and characterized. The properties of the alginate-CuO-GOD film were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Amperometric measurements were employed to characterize the analytical performance of the biosensor. Several parameters including amount of alginate, concentration of GOD and cross-linkers, amount of CuO nanoparticles, and effect of pH were studied and optimized. Under optimal conditions, the developed alginate-CuO-GOD biosensor was shown to have two linear ranges; from 0.04 mM to 3 mM (with a correlation coefficient of 0.9996 and the sensitivity of 30.443 μA mM −1 cm −2 ) and from 4 mM to 35 mM (with a correlation coefficient of 0.9994 and the sensitivity of 7.205 μA mM −1 cm −2 ). The overall detection limit was estimated to be 1.6 μM (signal-to-noise ratio of 3) and the K m value of 2.82 mM. The biosensor exhibited rather good performance with long-term stability (remainder of activity is 78% after 15 days) and significant specificity for glucose when compared to possible interfering molecules such as ascorbic acid, uric acid and acetaminophen. - Highlights: • An amperometric biosensor was constructed by using Alginate-CuO nano-biocomposite complexed with Glucose Oxidase • Glucose Oxidase immobilized to the surface via cross-linking. • Alginate-CuO film was characterized by SEM and FTIR. • The biosensor exhibits excellent analytical performance to glucose with a wide linear range and high sensitivity.

Low-potential sensitive H2O2 detection based on composite micro tubular Te adsorbed on platinum electrode.

Science.gov (United States)

Guascito, M R; Chirizzi, D; Malitesta, C; Mazzotta, E; M Siciliano; Siciliano, T; Tepore, A; Turco, A

2011-04-15

In this work a new original amperometric sensor for H(2)O(2) detection based on a Pt electrode modified with Te-microtubes was developed. Te-microtubes, synthesized by the simple thermal evaporation of Te powder, have a tubular structure with a hexagonal cross-section and are open ended. Modified electrode was prepared by direct drop casting of the mixture of Te-microtubes dispersed in ethanol on Pt surface. The spectroscopic characterization of synthesized Te-microtubes and Pt/Te-microtubes modified electrodes was performed by scanning electron microscopy (SEM), energy-dispersive X-rays microanalysis (EDX), X-ray diffraction analysis (XRD) and X-ray photoelectron spectroscopy (XPS). Moreover a complete electrochemical characterization of the new composite material Pt/Te-microtubes was performed by cyclic voltammetry (CV) and cronoamperometry (CA) in phosphate buffer solution (PBS) at pH 7. Electrochemical experiments showed that the presence of Te-microtubes on modified electrode was responsible for an increment of both cathodic and anodic currents in presence of H(2)O(2) with respect to bare Pt. Specifically, data collected from amperometric experiments at -150 mV vs. SCE in batch and -200 mV vs. SCE in flow injection analysis (FIA) experiments show a remarkable increment of the cathodic current. The electrochemical performances of tested sensors make them suitable for the quantitative determination of H(2)O(2) substrate both in batch and in FIA. Copyright © 2011 Elsevier B.V. All rights reserved.

Redox hydrogel based bienzyme electrode for L-glutamate monitoring.

Science.gov (United States)

Belay, A; Collins, A; Ruzgas, T; Kissinger, P T; Gorton, L; Csöregi, E

1999-02-01

Amperometric bienzyme electrodes based on coupled L-glutamate oxidase (GlOx) and horseradish peroxidase (HRP) were constructed for the direct monitoring of L-glutamate in a flow injection (FI)-system. The bienzyme electrodes were constructed by coating solid graphite rods with a premixed solution containing GlOx and HRP crosslinked with a redox polymer formed of poly(1-vinylimidazole) complexed with (osmium (4-4'-dimethylbpy)2 Cl)II/III. Poly(ethylene glycol) diglycidyl ether (PEGDGE) was used as the crosslinker and the modified electrodes were inserted as the working electrode in a conventional three electrode flow through amperometric cell operated at -0.05 V versus Ag¿AgCl (0.1 M KCl). The bienzyme electrode was optimized with regard to wire composition, Os-loading of the wires, enzyme ratios, coating procedure, flow rate, effect of poly(ethyleneimine) addition, etc. The optimized electrodes were characterized by a sensitivity of 88.36 +/- 0.14 microA mM(-1) cm(-2), a detection limit of 0.3 microM (calculated as three times the signal-to-noise ratio), a response time of less than 10 s and responded linearly between 0.3 and 250 microM (linear regression coefficient = 0.999) with an operational stability of only 3% sensitivity loss during 8 h of continuous FI operation at a sample throughput of 30 injections h(-1).

Amperometric Bioelectronic Tongue for glucose determination

Directory of Open Access Journals (Sweden)

Yazan Al-Issa

2015-03-01

Full Text Available An amperometric Bioelectronic Tongue is reported for glucose determination that contains eight sensor electrodes constructed using different metal electrodes (Pt, Au, oxidoreductase enzymes (glucose oxidase, ascorbate oxidase, uricase, and membrane coatings (Nafion, chitosan. The response to varying concentrations of glucose, ascorbic acid, uric acid, and acetaminophen was tested for two models, concentration determination by current density measurements at individual electrodes and concentration determination by a linear regression model for the entire electrode array. The reduced chi-squared for the full array model was found to be about one order of magnitude lower than that for the individual-electrode model. Discrimination of glucose from chemical interference by the other three species is accomplished through a combination of enzyme catalysis, metal electrocatalysis, and membrane surface charge. The benefit of incorporating enzyme electrodes into the sensor array is illustrated by the lower correlation coefficients between different enzyme electrodes relative to non-enzyme coated electrodes. This approach can be more generally applied to detection of other substrates of oxidoreductase enzymes.

Gas Flow Detection System

Science.gov (United States)

Moss, Thomas; Ihlefeld, Curtis; Slack, Barry

2010-01-01

This system provides a portable means to detect gas flow through a thin-walled tube without breaking into the tubing system. The flow detection system was specifically designed to detect flow through two parallel branches of a manifold with only one inlet and outlet, and is a means for verifying a space shuttle program requirement that saves time and reduces the risk of flight hardware damage compared to the current means of requirement verification. The prototype Purge Vent and Drain Window Cavity Conditioning System (PVD WCCS) Flow Detection System consists of a heater and a temperature-sensing thermistor attached to a piece of Velcro to be attached to each branch of a WCCS manifold for the duration of the requirement verification test. The heaters and thermistors are connected to a shielded cable and then to an electronics enclosure, which contains the power supplies, relays, and circuit board to provide power, signal conditioning, and control. The electronics enclosure is then connected to a commercial data acquisition box to provide analog to digital conversion as well as digital control. This data acquisition box is then connected to a commercial laptop running a custom application created using National Instruments LabVIEW. The operation of the PVD WCCS Flow Detection System consists of first attaching a heater/thermistor assembly to each of the two branches of one manifold while there is no flow through the manifold. Next, the software application running on the laptop is used to turn on the heaters and to monitor the manifold branch temperatures. When the system has reached thermal equilibrium, the software application s graphical user interface (GUI) will indicate that the branch temperatures are stable. The operator can then physically open the flow control valve to initiate the test flow of gaseous nitrogen (GN2) through the manifold. Next, the software user interface will be monitored for stable temperature indications when the system is again at

Phenylboronic acid immunoaffinity reactor coupled with flow injection chemiluminescence for determination of {alpha}-fetoprotein

Energy Technology Data Exchange (ETDEWEB)

Wu Yafeng [Jiangsu Provincial Key Lab of Biomaterials and Biodevices, School of Chemistry and Chemical Engineering, Southeast University, Nanjing 210096 (China); Zhuang Yafeng [Department of Chemistry, Changzhou Institute of Technology, Changzhou 213022 (China); Liu Songqin [Jiangsu Provincial Key Lab of Biomaterials and Biodevices, School of Chemistry and Chemical Engineering, Southeast University, Nanjing 210096 (China)], E-mail: liusq@seu.edu.cn; He Lin [Department of Chemistry, North Carolina State University, Raleigh, NC 27695-8204 (United States)

2008-12-23

A reusable and sensitive immunoassay based on phenylboronic acid immunoaffinity reactor in combination with flow injection chemiluminescence (CL) for determination of glycoprotein was described. The reactor was fabricated by immobilizing 3-aminophenylboronic acid (APBA) on glass microbeads with {gamma}-glycidoxypropyltrimethoxysilane (GPMS) as linkage. The {alpha}-fetoprotein (AFP) could be easily immobilized on the APBA coated beads through sugar-boronic interaction. After an off-line incubation, the mixture of the analyte AFP with horseradish peroxidase-labeled AFP antibody (HRP-anti-AFP) was injected into the reactor. This led the trapping of free HRP-anti-AFP by the surface coated AFP on glass beads. The trapped HRP-anti-AFP was detected by chemiluminescence due to its sensitizing effect on the reaction of luminol and hydrogen peroxide. Under optimal conditions, the chemiluminescent signal was proportional to AFP concentration in the range of 10-100 ng mL{sup -1}. The whole assay process including regeneration of the reactor could be completed within 31 min. The proposed system showed acceptable detection and fabrication reproducibility, and the results obtained with the present method were in acceptable agreement with those from parallel single-analyte test of practical clinical sera. The described method enabled a low-cost, time saving and was potential to detect the serum AFP level in clinical diagnosis.

Water injection profiling by nuclear logging

International Nuclear Information System (INIS)

Arnold, D.M.

1980-01-01

This invention relates to nuclear logging techniques for determining the volume flow rates and flow directions of injected water moving behind a wellbore casing. The apparatus includes a sonde equipped with a neutron source and dual radiation detectors. Oxygen in the neutron irradiated water is transmitted to 16 N and the resultant primary and Compton scattered gamma rays are detected in two energy windows by both detectors. Count rate data is analysed in terms of the windows to obtain linear flow velocities for water flow within and behind the casing. Volume flow rates are determined for upward and downward flow, and horizontal volume flow into the surrounding formation is calculated. A complete injection profile may thus be obtained. (U.K.)

Atrazine analysis using an amperometric immunosensor based on single-chain antibody fragments and regeneration-free multi-calibrant measurement

International Nuclear Information System (INIS)

Grennan, Kathleen; Strachan, Gillian; Porter, Andrew J.; Killard, Anthony J.; Smyth, Malcolm R.

2003-01-01

This work describes the development of an electrochemical immunosensor for the analysis of atrazine using recombinant single-chain antibody (scAb) fragments. The sensors are based on carbon paste screen-printed electrodes incorporating the conducting polymer polyaniline (PANI)/poly(vinylsulphonic acid) (PVSA), which enables direct mediatorless coupling to take place between the redox centres of antigen-labelled horseradish peroxidase (HRP) and the electrode surface. Competitive immunoassays can be performed in real-time using this separation-free system. Analytical measurements based on the pseudo-linear relationship between the slope of a real-time amperometric signal and the concentration of analyte, yield a novel immunosensor set-up capable of regenerationless amperometric analysis. Multiple, sequential measurements of standards and samples can be performed on a single scAb-modified surface in a matter of minutes. No separation of bound and unbound species was necessary prior to detection. The system is capable of measuring atrazine to a detection limit of 0.1 ppb (0.1 μg l -1 ). This system offers the potential for rapid, cost-effective immunosensing for the analysis of samples of environmental, medical and pharmaceutical significance

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.

Determination of Optimal Flow Paths for Safety Injection According to Accident Conditions

Energy Technology Data Exchange (ETDEWEB)

Yoo, Kwae Hwan; Kim, Ju Hyun; Kim, Dong Yeong; Na, Man Gyun [Chosun Univ., Gwangju (Korea, Republic of); Hur, Seop; Kim, Changhwoi [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2014-05-15

In case severe accidents happen, major safety parameters of nuclear reactors are rapidly changed. Therefore, operators are unable to respond appropriately. This situation causes the human error of operators that led to serious accidents at Chernobyl. In this study, we aimed to develop an algorithm that can be used to select the optimal flow path for cold shutdown in serious accidents, and to recover an NPP quickly and efficiently from the severe accidents. In order to select the optimal flow path, we applied a Dijkstra algorithm. The Dijkstra algorithm is used to find the path of minimum total length between two given nodes and needs a weight (or length) matrix. In this study, the weight between nodes was calculated from frictional and minor losses inside pipes. That is, the optimal flow path is found so that the pressure drop between a starting node (water source) and a destination node (position that cooling water is injected) is minimized. In case a severe accident has happened, if we inject cooling water through the optimized flow path, then the nuclear reactor will be safely and effectively returned into the cold shutdown state. In this study, we have analyzed the optimal flow paths for safety injection as a preliminary study for developing an accident recovery system. After analyzing the optimal flow path using the Dijkstra algorithm, and the optimal flow paths were selected by calculating the head loss according to path conditions.

Bi-enzyme L-arginine-selective amperometric biosensor based on ammonium-sensing polyaniline-modified electrode.

Science.gov (United States)

Stasyuk, Nataliya; Smutok, Oleh; Gayda, Galina; Vus, Bohdan; Koval'chuk, Yevgen; Gonchar, Mykhailo

2012-01-01

A novel L-arginine-selective amperometric bi-enzyme biosensor based on recombinant human arginase I isolated from the gene-engineered strain of methylotrophic yeast Hansenula polymorpha and commercial urease is described. The biosensing layer was placed onto a polyaniline-Nafion composite platinum electrode and covered with a calcium alginate gel. The developed sensor revealed a good selectivity to L-arginine. The sensitivity of the biosensor was 110 ± 1.3 nA/(mM mm(2)) with the apparent Michaelis-Menten constant (K(M)(app)) derived from an L-arginine (L-Arg) calibration curve of 1.27 ± 0.29 mM. A linear concentration range was observed from 0.07 to 0.6mM, a limit of detection being 0.038 mM and a response time - 10s. The developed biosensor demonstrated good storage stability. A laboratory prototype of the proposed amperometric biosensor was applied to the samples of three commercial pharmaceuticals ("Tivortin", "Cytrarginine", "Aminoplazmal 10% E") for L-Arg testing. The obtained L-Arg-content values correlated well with those declared by producers. Copyright © 2012 Elsevier B.V. All rights reserved.

A CMOS analog front-end chip for amperometric electrochemical sensors

International Nuclear Information System (INIS)

Li Zhichao; Chen Min; Xiao Jingbo; Chen Jie; Liu Yuntao

2015-01-01

This paper reports a complimentary metal–oxide–semiconductor (CMOS) analog front-end chip for amperometric electrochemical sensors. The chip includes a digital configuration circuit, which can communicate with an external microcontroller by employing an I 2 C interface bus, and thus is highly programmable. Digital correlative double samples technique and an incremental sigma–delta analog to digital converter (Σ–Δ ADC) are employed to achieve a new proposed system architecture with double samples. The chip has been fabricated in a standard 0.18-μm CMOS process with high-precision and high-linearity performance occupying an area of 1.3 × 1.9 mm 2 . Sample solutions with various phosphate concentrations have been detected with a step concentration of 0.01 mg/L. (paper)

Flow rate dependent extra-column variance from injection in capillary liquid chromatography.

Science.gov (United States)

Aggarwal, Pankaj; Liu, Kun; Sharma, Sonika; Lawson, John S; Dennis Tolley, H; Lee, Milton L

2015-02-06

Efficiency and resolution in capillary liquid chromatography (LC) can be significantly affected by extra-column band broadening, especially for isocratic separations. This is particularly a concern in evaluating column bed structure using non-retained test compounds. The band broadening due to an injector supplied with a commercially available capillary LC system was characterized from experimental measurements. The extra-column variance from the injection valve was found to have an extra-column contribution independent of the injection volume, showing an exponential dependence on flow rate. The overall extra-column variance from the injection valve was found to vary from 34 to 23 nL. A new mathematical model was derived that explains this exponential contribution of extra-column variance on chromatographic performance. The chromatographic efficiency was compromised by ∼130% for a non-retained analyte because of injection valve dead volume. The measured chromatographic efficiency was greatly improved when a new nano-flow pumping system with integrated injection valve was used. Copyright © 2014 Elsevier B.V. All rights reserved.

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

Re-injection feasibility study of fracturing flow-back fluid in shale gas mining

Science.gov (United States)

Kang, Dingyu; Xue, Chen; Chen, Xinjian; Du, Jiajia; Shi, Shengwei; Qu, Chengtun; Yu, Tao

2018-02-01

Fracturing flow-back fluid in shale gas mining is usually treated by re-injecting into formation. After treatment, the fracturing flow-back fluid is injected back into the formation. In order to ensure that it will not cause too much damage to the bottom layer, feasibility evaluations of re-injection of two kinds of fracturing fluid with different salinity were researched. The experimental research of the compatibility of mixed water samples based on the static simulation method was conducted. Through the analysis of ion concentration, the amount of scale buildup and clay swelling rate, the feasibility of re-injection of different fracturing fluid were studied. The result shows that the swelling of the clay expansion rate of treated fracturing fluid is lower than the mixed water of treated fracturing fluid and the distilled water, indicating that in terms of clay expansion rate, the treated fracturing flow-back fluid is better than that of water injection after re-injection. In the compatibility test, the maximum amount of fouling in the Yangzhou oilfield is 12mg/L, and the maximum value of calcium loss rate is 1.47%, indicating that the compatibility is good. For the fracturing fluid with high salinity in the Yanchang oilfield, the maximum amount of scaling is 72mg/L, and the maximum calcium loss rate is 3.50%, indicating that the compatibility is better.

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.

Interaction with Deoxyribonucleic Acid and Determination of Orientin in Lophatherum gracile Brongn by High-Performance Liquid Chromatography with Amperometric Detection

International Nuclear Information System (INIS)

Wang, Fang; Yan, Fangfang; Long, Yuling; Wang, Lili; Chen, Zilin

2015-01-01

The mechanisms of the electrochemical oxidation of orientin and its interaction with deoxyribonucleic acid have been investigated using glassy carbon electrode. The electrochemical response of orientin is due to oxidation of phenolic hydroxyl groups on orientin. The whole process is controlled by the adsorption step and concerned 4 electrons and 4 protons. Negative shift of potential and decrease of peak current for electrochemical oxidation of orientin can be observed at bare glassy carbon electrode and deoxyribonucleic acid modified electrode in 0.05 M Na_2HPO_4-KH_2PO_4 (pH 7.48), confirming the dominant electrostatic interaction between orientin and deoxyribonucleic acid. Moreover, a reliable and sensitive method of reversed-phase high-performance liquid chromatography-electrochemical detection has been developed for simultaneous determination of the isomer pair orientin/isoorientin. Chromatographic separation was carried out on a reversed-phase C_1_8 column and a mobile phase comprised of acetonitrile and acetate (0.5%, pH 2.97) by amperometric detection with a glassy carbon electrode at the working potential of +1.00 V. The method was validated for linearity, accuracy, precision, and limit of detection. Under the optimized conditions, linear regression analysis for the calibration curve showed a good linear relationship between peak area and their concentrations in the linear range of 89.2 nM to 59.5 μM for orientin with detection limit of 14.9 nM and 78.0 nM to 52.0 μM for isoorientin with a detection limit of 13.0 nM, respectively. Compared to the method using ultraviolet detection, the detection limits are greatly lowered. Finally, the proposed method has been successfully applied to the determination of orientin and isoorientin in Lophatherum gracile Brongn.

Nonenzymatic amperometric determination of glucose by CuO nanocubes-graphene nanocomposite modified electrode.

Science.gov (United States)

Luo, Liqiang; Zhu, Limei; Wang, Zhenxin

2012-12-01

Here, we report a nonenzymatic amperometric glucose sensor based on copper oxide (CuO) nanocubes-graphene nanocomposite modified glassy carbon electrode (CuO-G-GCE). In this case, the graphene sheets were cast on the GCE directly. CuO nanocubes were obtained by oxidizing electrochemically deposited Cu on the graphene. The morphology of CuO-G nanocomposite was characterized by scanning electron microscopy. The CuO-G-GCE-based sensor exhibited excellent electrocatalytic activity and high stability for glucose oxidation. Under optimized conditions, the linearity between the current response and the glucose concentration was obtained in the range of 2μM to 4mM with a detection limit of 0.7μM (S/N=3), and a high sensitivity of 1360μAmM(-1)cm(-2). The proposed electrode showed a fast response time (less than 5s) and a good reproducibility. The as-made sensor was applied to determine the glucose levels in clinic human serum samples with satisfactory results. In addition, the effects of common interfering species, including ascorbic acid, uric acid, dopamine and other carbohydrates, on the amperometric response of the sensor were investigated and discussed in detail. Copyright © 2012 Elsevier B.V. All rights reserved.

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

Energy Technology Data Exchange (ETDEWEB)

Shitanda, Isao [Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510 (Japan)], E-mail: shitanda@rs.noda.tus.ac.jp; Takamatsu, Satoshi; Watanabe, Kunihiro; Itagaki, Masayuki [Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510 (Japan)

2009-08-30

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{sup '}{sub 50}) for atrazine and DCMU were 12 and 1 {mu}mol dm{sup -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.

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.

Application of a field flow preconcentration system with a minicolumn packed with amberlite XAD-4/1-(2-pyridylazo)-2-naphtol and a flow injection-flame atomic adsorption spectrometric system for lead determination in sea water

International Nuclear Information System (INIS)

Carmen Yebra, M. del; Rodriguez, L.; Puig, L.; Moreno-Cid, A.

2002-01-01

A field flow preconcentration technique involving a minicolumn containing Amberlite XAD-4 impregnated with the complexing agent 1-(2-pyridylazo)-2-naphthol was used to preconcentrate lead from seawater. Elution of retained lead on the minicolumns was performed by a flow-injection-flame atomic absorption spectrometric system. Factorial designs have been used to optimize the field flow preconcentration system and the flow injection elution process. Factors such as sample pH, sample flow-rate, eluent concentration and volume (hydrochloric acid), elution flow-rate and minicolumn diameter were considered. The results suggest that the sample flow-rate and the eluent volume are statistically significant factors. The detection limit (3σ) of the procedure was 5 ng/L for a sample volume of 1000 ml. The precision (expressed as relative standard deviation) for eleven independent determinations reached values of 4.0-3.1 % in lead solutions of 50-200 ng/L. This procedure has been successfully applied to the determination of lead in seawater from Galicia (Spain). (author)

Rapid dual-injection single-scan 13N-ammonia PET for quantification of rest and stress myocardial blood flows

International Nuclear Information System (INIS)

Rust, T C; DiBella, E V R; McGann, C J; Christian, P E; Hoffman, J M; Kadrmas, D J

2006-01-01

Quantification of myocardial blood flows at rest and stress using 13 N-ammonia PET is an established method; however, current techniques require a waiting period of about 1 h between scans. The objective of this study was to test a rapid dual-injection single-scan approach, where 13 N-ammonia injections are administered 10 min apart during rest and adenosine stress. Dynamic PET data were acquired in six human subjects using imaging protocols that provided separate single-injection scans as gold standards. Rest and stress data were combined to emulate rapid dual-injection data so that the underlying activity from each injection was known exactly. Regional blood flow estimates were computed from the dual-injection data using two methods: background subtraction and combined modelling. The rapid dual-injection approach provided blood flow estimates very similar to the conventional single-injection standards. Rest blood flow estimates were affected very little by the dual-injection approach, and stress estimates correlated strongly with separate single-injection values (r = 0.998, mean absolute difference = 0.06 ml min -1 g -1 ). An actual rapid dual-injection scan was successfully acquired in one subject and further demonstrates feasibility of the method. This study with a limited dataset demonstrates that blood flow quantification can be obtained in only 20 min by the rapid dual-injection approach with accuracy similar to that of conventional separate rest and stress scans. The rapid dual-injection approach merits further development and additional evaluation for potential clinical use

Determination of gallic acid with rhodanine by reverse flow injection analysis using simplex optimization.

Science.gov (United States)

Phakthong, Wilaiwan; Liawruangrath, Boonsom; Liawruangrath, Saisunee

2014-12-01

A reversed flow injection (rFI) system was designed and constructed for gallic acid determination. Gallic acid was determined based on the formation of chromogen between gallic acid and rhodanine, resulting in a colored product with a λmax at 520 nm. The optimum conditions for determining gallic acid were also investigated. Optimizations of the experimental conditions were carried out based on the so-call univariate method. The conditions obtained were 0.6% (w/v) rhodanine, 70% (v/v) ethanol, 0.9 mol L(-1) NaOH, 2.0 mL min(-1) flow rate, 75 μL injection loop and 600 cm mixing tubing length, respectively. Comparative optimizations of the experimental conditions were also carried out by multivariate or simplex optimization method. The conditions obtained were 1.2% (w/v) rhodanine, 70% (v/v) ethanol, 1.2 mol L(-1) NaOH, flow rate 2.5 mL min(-1), 75 μL injection loop and 600 cm mixing tubing length, respectively. It was found that the optimum conditions obtained by the former optimization method were mostly similar to those obtained by the latter method. The linear relationship between peak height and the concentration of gallic acid was obtained over the range of 0.1-35.0 mg L(-1) with the detection limit 0.081 mg L(-1). The relative standard deviations were found to be in the ranges 0.46-1.96% for 1, 10, 30 mg L(-1) of gallic acid (n=11). The method has the advantages of simplicity extremely high selectivity and high precision. The proposed method was successfully applied to the determination of gallic acid in longan samples without interferent effects from other common phenolic compounds that might be present in the longan samples collected in northern Thailand. Copyright © 2014 Elsevier B.V. All rights reserved.

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.

Simultaneous determination of tyramine and tryptamine and their precursor amino acids by micellar liquid chromatography and pulsed amperometric detection in wines.

Science.gov (United States)

Gil-Agustí, M; Carda-Broch, S; Monferrer-Pons, Ll; Esteve-Romero, J

2007-07-13

Two biogenic amines, tryptamine and tyramine, and their precursors, tryptophan and tyrosine, were determined by a liquid chromatographic procedure. A hybrid micellar mobile phase of sodium dodecyl sulphate (SDS) and 1-propanol, a C18 column and electrochemical detection were used. A pH study in the range of 3-9 was performed and pH 3 was finally selected in accordance with resolution and analysis time. Oxidation potential was also checked in the range 0.6-0.9V: the maximum area obtained in all those potentials was at 0.8V, which was selected to carry out the analysis using a sequence of pulsed amperometric detection waveform. The four compounds were resolved using a mobile phase of 0.15M SDS-5% 1-propanol with an analysis time of 16 min. Repeatabilities and intermediate precision were evaluated at three different concentrations for each compound with RSD values lower than 2.6 and 4.8%, respectively. Limits of detection and quantification were also obtained within the 10-40 and 33-135 ng/ml ranges, respectively. Finally, the applicability of the procedure was tested in several types of wine and no matrix effect was observed. The possibility of direct sample introduction simplifies and greatly expedites the treatments with reduced cost, improving the accuracy of the procedures.

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

Enhancement of melting heat transfer of ice slurries by an injection flow in a rectangular cross sectional horizontal duct

International Nuclear Information System (INIS)

Fujii, Kota; Yamada, Masahiko

2013-01-01

Ice slurries are now commonly used as cold thermal storage materials, and have the potential to be applied to other engineering fields such as quenching metals to control properties, emergency cooling systems, and preservation of food and biomaterials at low temperatures. Although ice slurries have been widely utilized because of their high thermal storage densities, previous studies have revealed that the latent heat of ice particles is not completely released on melting because of insufficient contact between the ice particles and a heated surface. In this study, an injection flow that was bifurcated from the main flow of an ice slurry was employed to promote melting heat transfer of ice particles on a horizontal heated surface. The effects of injection angle and injection flow rate on local heat transfer coefficients and heat transfer coefficient ratios were determined experimentally. The results show that from two to three times higher heat transfer coefficients can be obtained by using large injection flow rates and injection angles. However, low injection angles improved the utilization rate of the latent heat of ice near the injection point by approximately a factor of two compared to that without injection. -- Highlights: • Melting of ice slurries were enhanced by the injection under constant total flow rate. • Contribution of ice particles and their latent heat to heat transfer was investigated. • Effect of velocity ratio of injection to that of main flow was examined. • Effect of the angle of injection flow to the main flow was also examined. • Appropriate conditions for the use of latent heat of ice and heat transfer did not coincide

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.

Liquid sprays and flow studies in the direct-injection diesel engine under motored conditions

Science.gov (United States)

Nguyen, Hung Lee; Carpenter, Mark H.; Ramos, Juan I.; Schock, Harold J.; Stegeman, James D.

1988-01-01

A two dimensional, implicit finite difference method of the control volume variety, a two equation model of turbulence, and a discrete droplet model were used to study the flow field, turbulence levels, fuel penetration, vaporization, and mixing in diesel engine environments. The model was also used to study the effects of engine speed, injection angle, spray cone angle, droplet distribution, and intake swirl angle on the flow field, spray penetration and vaporization, and turbulence in motored two-stroke diesel engines. It is shown that there are optimum conditions for injection, which depend on droplet distribution, swirl, spray cone angle, and injection angle. The optimum conditions result in good spray penetration and vaporization and in good fuel mixing. The calculation presented clearly indicates that internal combustion engine models can be used to assess, at least qualitatively, the effects of injection characteristics and engine operating conditions on the flow field and on the spray penetration and vaporization in diesel engines.

Application of direct-injection detector integrated with the multi-pumping flow system to chemiluminescence determination of the total polyphenol index.

Science.gov (United States)

Nalewajko-Sieliwoniuk, Edyta; Iwanowicz, Magdalena; Kalinowski, Sławomir; Kojło, Anatol

2016-03-10

In this work, we present a novel chemiluminescence (CL) method based on direct-injection detector (DID) integrated with the multi-pumping flow system (MPFS) to chemiluminescence determination of the total polyphenol index. In this flow system, the sample and the reagents are injected directly into the cone-shaped detection cell placed in front of the photomultiplier window. Such construction of the detection chamber allows for fast measurement of the CL signal in stopped-flow conditions immediately after mixing the reagents. The proposed DID-CL-MPFS method is based on the chemiluminescence of nanocolloidal manganese(IV)-hexametaphosphate-ethanol system. The application of ethanol as a sensitizer, eliminated the use of carcinogenic formaldehyde. Under the optimized experimental conditions, the chemiluminescence intensities are proportional to the concentration of gallic acid in the range from 5 to 350 ng mL(-1). The DID-CL-MPFS method offers a number of advantages, including low limit of detection (0.80 ng mL(-1)), high precision (RSD = 3.3%) and high sample throughput (144 samples h(-1)) as well as low consumption of reagents, energy and low waste generation. The proposed method has been successfully applied to determine the total polyphenol index (expressed as gallic acid equivalent) in a variety of plant-derived food samples (wine, tea, coffee, fruit and vegetable juices, herbs, spices). Copyright © 2016 Elsevier B.V. All rights reserved.

An electrochemiluminescence-based fibre optic biosensor for choline flow injection analysis.

Science.gov (United States)

Tsafack, V C; Marquette, C A; Leca, B; Blum, L J

2000-01-01

A fibre optic biosensor based on luminol electrochemiluminescence (ECL) integrated in a flow injection analysis (FIA) system was developed for the detection of choline. The electrochemiluminescence of luminol was generated by a glassy carbon electrode polarised at +425 mV vs. a platinum pseudo-reference electrode. Choline oxidase (Chx) was immobilised either covalently on polyamide (ABC type) or on UltraBind preactivated membranes, or by physical entrapment in a photo-cross-linkable poly(vinyl alcohol) polymer (PVA-SbQ) alone or after absorption on a weak anion exchanger, DEAE (diethylaminoethyl) Sepharose. The optimisation of the reaction conditions and physicochemical parameters influencing the FIA biosensor response demonstrated that the choline biosensor exhibited the best performances in a 30 mM veronal buffer containing 30 mM KCl and 1.5 mM MgCl2, at pH 9. The use of a 0.5 ml min-1 flow rate enabled the measurement of choline by the membrane-based ECL biosensors in 8 or 5 min, with ABC or UltraBind membranes, respectively, whereas the measurement required only 3 min with the DEAE-PVA system. For comparison, the detection of choline was performed with Chx immobilised using the four different supports. The best performances were obtained with the DEAE-PVA-Chx sensing layer, which allowed a detection limit of 10 pmol, whereas with the ABC, the UltraBind and the PVA systems, the detection limits were 300 pmol, 75 pmol and 220 pmol, respectively. The DEAE-based system also exhibited a good operational stability since 160 repeated measurements of 3 nmol of choline could be performed with an RSD of 4.5% whereas the stability under the best conditions was 45 assays with the other supports.

Numerical investigation of the air injection effect on the cavitating flow in Francis hydro turbine

Science.gov (United States)

Chirkov, D. V.; Shcherbakov, P. K.; Cherny, S. G.; Skorospelov, V. A.; Turuk, P. A.

2017-09-01

At full and over load operating points, some Francis turbines experience strong self-excited pressure and power oscillations. These oscillations are occuring due to the hydrodynamic instability of the cavitating fluid flow. In many cases, the amplitude of such pulsations may be reduced substantially during the turbine operation by the air injection/ admission below the runner. Such an effect is investigated numerically in the present work. To this end, the hybrid one-three-dimensional model of the flow of the mixture "liquid-vapor" in the duct of a hydroelectric power station, which was proposed previously by the present authors, is augmented by the second gaseous component — the noncondensable air. The boundary conditions and the numerical method for solving the equations of the model are described. To check the accuracy of computing the interface "liquid-gas", the numerical method was applied at first for solving the dam break problem. The algorithm was then used for modeling the flow in a hydraulic turbine with air injection below the runner. It is shown that with increasing flow rate of the injected air, the amplitude of pressure pulsations decreases. The mechanism of the flow structure alteration in the draft tube cone has been elucidated, which leads to flow stabilization at air injection.

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.

Amperometric Acetylcholinesterase Biosensor Based on Multilayer Multiwall Carbon Nanotubes-chitosan Composite

Directory of Open Access Journals (Sweden)

Xia SUN

2011-11-01

Full Text Available A simple method for immobilization of acetylcholinesterase (AChE onto the glassy carbon electrode (GCE modified with five layers of multiwall carbon nanotubes (MWNTs-chitosan (CHIT composite was proposed, and thus a fast, sensitive and stable amperometric sensor for quantitative determination of pesticides was developed. Five layers of MWNTs-CHIT promoted electron transfer reactions at a lower potential and catalyzed the electro-oxidation of thiocholine, thus, it improved the detection sensitivity of biosensor. Based on the inhibition of pesticides to the enzymatic activity of AChE, using carbofuran as a model compound, under optimal conditions, the inhibition of carbofuran was proportional to its concentration in two ranges, from 5×10-4 to 7.5 μg/mL and 7.5 to 20 μg/mL with a detection limit of 1×10-4 μg/mL. The constructed biosensor showed prominent characteristics and performances such as good precision, acceptable stability, fast response and low detection limit, which provided a new promising tool for pesticide analysis.

Measurement system for nitrous oxide based on amperometric gas sensor

Science.gov (United States)

Siswoyo, S.; Persaud, K. C.; Phillips, V. R.; Sneath, R.

2017-03-01

It has been well known that nitrous oxide is an important greenhouse gas, so monitoring and control of its concentration and emission is very important. In this work a nitrous oxide measurement system has been developed consisting of an amperometric sensor and an appropriate lab-made potentiostat that capable measuring picoampere current ranges. The sensor was constructed using a gold microelectrode as working electrode surrounded by a silver wire as quasi reference electrode, with tetraethyl ammonium perchlorate and dimethylsulphoxide as supporting electrolyte and solvent respectively. The lab-made potentiostat was built incorporating a transimpedance amplifier capable of picoampere measurements. This also incorporated a microcontroller based data acquisition system, controlled by a host personal computer using a dedicated computer program. The system was capable of detecting N2O concentrations down to 0.07 % v/v.

Numerical Simulation of Polymer Injection in Turbulent Flow Past a Circular Cylinder

KAUST Repository

Richter, David; Shaqfeh, Eric S. G.; Iaccarino, Gianluca

2011-01-01

Using a code developed to compute high Reynolds number viscoelastic flows, polymer injection from the upstream stagnation point of a circular cylinder is modeled at Re = 3900. Polymer stresses are represented using the FENE-P constitutive equations. By increasing polymer injection rates within realistic ranges, significant near wake stabilization is observed. Rather than a turbulent detached shear layer giving way to a chaotic primary vortex (as seen in Newtonian flows at high Re), a much more coherent primary vortex is shed, which possesses an increased core pressure as well as a reduced level of turbulent energy. © 2011 American Society of Mechanical Engineers.

Detection of dopamine in non-treated urine samples using glassy carbon electrodes modified with PAMAM dendrimer-Pt composites

International Nuclear Information System (INIS)

Garcia, M.G.; Armendariz, G.M.E.; Godinez, Luis A.; Torres, J.; Sepulveda-Guzman, S.; Bustos, E.

2011-01-01

Composites of hydroxyl-terminated PAMAM dendrimers, generation 4.0 (64 peripheral OH groups) containing Pt nanoparticles were synthesized at different reaction times using a microwave reactor. The synthetic procedure resulted in dendrimer encapsulated nanoparticles of Pt (DENs-Pt) of 1.53 ± 0.17 nm diameter that was calculated from transmission electron microscopy, and the Pt nanoparticles had single crystal plane in (1 1 1) orientation determinate by selective area diffraction. Each composite was electrochemically immobilized on a pre-functionalized glassy carbon (GC) electrode that was incorporated as a flow injection amperometric (FIA) detector, for the selective detection and quantification of dopamine (DA) in untreated urine samples. Comparison of the analytical performance of the novel electrochemical detector revealed that the DENs-Pt modified GC electrode with the composite synthesized for 30 min in the microwave reactor, showed the best response for the detection of DA in samples of non-treated urine, being the detection and quantification limits smaller (19 and 9 ppb, respectively) than those corresponding to the naked a GC electrode (846 and 423 ppb, respectively) using the FIA detector. In addition, it was found that this electroanalytical approach suffers minimal matrix effects that arise in the analysis of DA in untreated samples of urine.

Detection of dopamine in non-treated urine samples using glassy carbon electrodes modified with PAMAM dendrimer-Pt composites

Energy Technology Data Exchange (ETDEWEB)

Garcia, M.G. [Laboratory of Bioelectrochemistry, Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, S. C., Parque Tecnologico, Queretaro, Sanfandila, Pedro Escobedo 76703, Queretaro (Mexico); Department of Chemistry, Universidad de Guanajuato, Cerro de la Venada S/N Col. Pueblito de Rocha, 36040 Guanajuato, Gto (Mexico); Armendariz, G.M.E.; Godinez, Luis A.; Torres, J. [Laboratory of Bioelectrochemistry, Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, S. C., Parque Tecnologico, Queretaro, Sanfandila, Pedro Escobedo 76703, Queretaro (Mexico); Sepulveda-Guzman, S. [Centro de Innovacion, Investigacion y Desarrollo en Ingenieria y Tecnologia, Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, Av. Universidad, San Nicolas de los Garza, Nuevo Leon, 66451 Nuevo Leon (Mexico); Bustos, E., E-mail: ebustos@cideteq.mx [Laboratory of Bioelectrochemistry, Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, S. C., Parque Tecnologico, Queretaro, Sanfandila, Pedro Escobedo 76703, Queretaro (Mexico)

2011-09-01

Composites of hydroxyl-terminated PAMAM dendrimers, generation 4.0 (64 peripheral OH groups) containing Pt nanoparticles were synthesized at different reaction times using a microwave reactor. The synthetic procedure resulted in dendrimer encapsulated nanoparticles of Pt (DENs-Pt) of 1.53 {+-} 0.17 nm diameter that was calculated from transmission electron microscopy, and the Pt nanoparticles had single crystal plane in (1 1 1) orientation determinate by selective area diffraction. Each composite was electrochemically immobilized on a pre-functionalized glassy carbon (GC) electrode that was incorporated as a flow injection amperometric (FIA) detector, for the selective detection and quantification of dopamine (DA) in untreated urine samples. Comparison of the analytical performance of the novel electrochemical detector revealed that the DENs-Pt modified GC electrode with the composite synthesized for 30 min in the microwave reactor, showed the best response for the detection of DA in samples of non-treated urine, being the detection and quantification limits smaller (19 and 9 ppb, respectively) than those corresponding to the naked a GC electrode (846 and 423 ppb, respectively) using the FIA detector. In addition, it was found that this electroanalytical approach suffers minimal matrix effects that arise in the analysis of DA in untreated samples of urine.

Electrochemical formation of InP porous nanostructures and its application to amperometric chemical sensors

International Nuclear Information System (INIS)

Sato, Taketomo; Mizohata, Akinori; Fujino, Toshiyuki; Hashizume, Tamotsu

2008-01-01

In this paper, we report the electrochemical formation of the InP porous nanostructures and their feasibility for the application to the amperometric chemical sensors. Our two step electrochemical process consists of the pore formation on a (001) n-type InP substrate and the subsequent etching of pore walls caused by changing the polarity of the InP electrode in a HCl-based electrolyte. By applying the anodic bias to the InP electrode, the high-density array of uniform nanopores was formed on the surface. Next, the cathodic bias was applied to the porous sample to reduce the wall thickness by cathodic decomposition of InP, where the thickness of InP nanowall decreased uniformly along the entire depth of the porous layer. From the amperometric measurements of the porous electrode, it was found that the electrocatalytic activity was much higher than that of the planar electrode. Furthermore, the current sensitivity for the H 2 O 2 detection was much enhanced after the cathodic decomposition process. The InP porous nanostructure formed by the present process is one of the promising structures for the application to the semiconductor-based bio/chemical sensors. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Detailed evaluation of the natural circulation mass flow rate of water propelled by using an air injection

International Nuclear Information System (INIS)

Park, Rae-Joon; Ha, Kwang-Soon; Kim, Jae-Cheol; Hong, Seong-Wan; Kim, Sang-Baik

2008-01-01

One-dimensional (1D) air-water two-phase natural circulation flow in the thermohydraulic evaluation of reactor cooling mechanism by external self-induced flow - one-dimensional' (THERMES-1D) experiment has been verified and evaluated by using the RELAP5/MOD3 computer code. Experimental results on the 1D natural circulation mass flow rate of water propelled by using an air injection have been evaluated in detail. The RELAP5 results have shown that an increase in the air injection rate to 50% of the total heat flux leads to an increase in the water circulation mass flow rate. However, an increase in the air injection rate from 50 to 100% does not affect the water circulation mass flow rate, because of the inlet area condition. As the height increases in the air injection part, the void fraction increases. However, the void fraction in the upper part of the air injector maintains a constant value. An increase in the air injection mass flow rate leads to an increase in the local void fraction, but it has no influence on the local pressure. An increase in the coolant inlet area leads to an increase in the water circulation mass flow rate. However, the water outlet area does not have an influence on the water circulation mass flow rate. As the coolant outlet moves to a lower position, the water circulation mass flow rate decreases. (author)

Decompositions of injection patterns for nodal flow allocation in renewable electricity networks

Science.gov (United States)

Schäfer, Mirko; Tranberg, Bo; Hempel, Sabrina; Schramm, Stefan; Greiner, Martin

2017-08-01

The large-scale integration of fluctuating renewable power generation represents a challenge to the technical and economical design of a sustainable future electricity system. In this context, the increasing significance of long-range power transmission calls for innovative methods to understand the emerging complex flow patterns and to integrate price signals about the respective infrastructure needs into the energy market design. We introduce a decomposition method of injection patterns. Contrary to standard flow tracing approaches, it provides nodal allocations of link flows and costs in electricity networks by decomposing the network injection pattern into market-inspired elementary import/export building blocks. We apply the new approach to a simplified data-driven model of a European electricity grid with a high share of renewable wind and solar power generation.

Modeling and flow analysis of pure nylon polymer for injection molding process

International Nuclear Information System (INIS)

Nuruzzaman, D M; Kusaseh, N; Basri, S; Hamedon, Z; Oumer, A N

2016-01-01

In the production of complex plastic parts, injection molding is one of the most popular industrial processes. This paper addresses the modeling and analysis of the flow process of the nylon (polyamide) polymer for injection molding process. To determine the best molding conditions, a series of simulations are carried out using Autodesk Moldflow Insight software and the processing parameters are adjusted. This mold filling commercial software simulates the cavity filling pattern along with temperature and pressure distributions in the mold cavity. In the modeling, during the plastics flow inside the mold cavity, different flow parameters such as fill time, pressure, temperature, shear rate and warp at different locations in the cavity are analyzed. Overall, this Moldflow is able to perform a relatively sophisticated analysis of the flow process of pure nylon. Thus the prediction of the filling of a mold cavity is very important and it becomes useful before a nylon plastic part to be manufactured. (paper)

Modeling and flow analysis of pure nylon polymer for injection molding process

Science.gov (United States)

Nuruzzaman, D. M.; Kusaseh, N.; Basri, S.; Oumer, A. N.; Hamedon, Z.

2016-02-01

In the production of complex plastic parts, injection molding is one of the most popular industrial processes. This paper addresses the modeling and analysis of the flow process of the nylon (polyamide) polymer for injection molding process. To determine the best molding conditions, a series of simulations are carried out using Autodesk Moldflow Insight software and the processing parameters are adjusted. This mold filling commercial software simulates the cavity filling pattern along with temperature and pressure distributions in the mold cavity. In the modeling, during the plastics flow inside the mold cavity, different flow parameters such as fill time, pressure, temperature, shear rate and warp at different locations in the cavity are analyzed. Overall, this Moldflow is able to perform a relatively sophisticated analysis of the flow process of pure nylon. Thus the prediction of the filling of a mold cavity is very important and it becomes useful before a nylon plastic part to be manufactured.

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.

Study of process parameters on two phase flow agitated by top blowing lance injection into a bath

Energy Technology Data Exchange (ETDEWEB)

Xia Jiliang; Ahokainen, T.; Holappa, L.

1998-12-31

Numerical investigation has been carried out for two phase flow in a bath agitated by top blowing lance injection. Eulerian two phase flow model is used. Lance immersion depth, injection gas flow rate, nozzle diameter, and bubble size have been systematically changed to examine their influence on the flow characteristics in the bath. It is found that there appear three typical flow patterns: one-vortex, two-vortex, and three-vortex type, with changing the injection gas flow rate or/and the nozzle diameter at moderate lance immersion depth. Predicted velocities are in a good agreement with Iguchi et al.`s experimental data and the main findings are also consistent with the measurements and observations of Chatterjee and Hsiao and Lehner. (orig.) 24 refs. Computational Fluid Dynamics Technology Programme

Flow injection kinetic spectrofluorimetric determination of trace amounts of osmium

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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.

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)

Transverse injection into Mach 2 flow behind a rearward-facing step - A 3-D, compressible flow test case for hypersonic combustor CFD validation

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Mcdaniel, James C.; Fletcher, Douglas G.; Hartfield, Roy J.; Hollo, Steven D.

1991-01-01

A spatially-complete data set of the important primitive flow variables is presented for the complex, nonreacting, 3D unit combustor flow field employing transverse injection into a Mach 2 flow behind a rearward-facing step. A unique wind tunnel facility providing the capability for iodine seeding was built specifically for these measurements. Two optical techniques based on laser-induced-iodine fluorescence were developed and utilized for nonintrusive, in situ flow field measurements. LDA provided both mean and fluctuating velocity component measurements. A thermographic phosphor wall temperature measurement technique was developed and employed. Data from the 2D flow over a rearward-facing step and the complex 3D mixing flow with injection are reported.

Improvement of Power Flow Calculation with Optimization Factor Based on Current Injection Method

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Lei Wang

2014-01-01

Full Text Available This paper presents an improvement in power flow calculation based on current injection method by introducing optimization factor. In the method proposed by this paper, the PQ buses are represented by current mismatches while the PV buses are represented by power mismatches. It is different from the representations in conventional current injection power flow equations. By using the combined power and current injection mismatches method, the number of the equations required can be decreased to only one for each PV bus. The optimization factor is used to improve the iteration process and to ensure the effectiveness of the improved method proposed when the system is ill-conditioned. To verify the effectiveness of the method, the IEEE test systems are tested by conventional current injection method and the improved method proposed separately. Then the results are compared. The comparisons show that the optimization factor improves the convergence character effectively, especially that when the system is at high loading level and R/X ratio, the iteration number is one or two times less than the conventional current injection method. When the overloading condition of the system is serious, the iteration number in this paper appears 4 times less than the conventional current injection method.

Bioethanol in Biofuels Checked by an Amperometric Organic Phase Enzyme Electrode (OPEE Working in “Substrate Antagonism” Format

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Mauro Tomassetti

2016-08-01

Full Text Available The bioethanol content of two samples of biofuels was determined directly, after simple dilution in decane, by means of an amperometric catalase enzyme biosensor working in the organic phase, based on substrate antagonisms format. The results were good from the point of view of accuracy, and satisfactory for what concerns the recovery test by the standard addition method. Limit of detection (LOD was on the order of 2.5 × 10−5 M.

Disposable Amperometric Immunosensor for the Determination of Human P53 Protein in Cell Lysates Using Magnetic Micro-Carriers

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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.

Recent Development in Optical Chemical Sensors Coupling with Flow Injection Analysis

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Fuensanta Sánchez Rojas

2006-10-01

Full Text Available Optical techniques for chemical analysis are well established and sensors based on thesetechniques are now attracting considerable attention because of their importance in applications suchas environmental monitoring, biomedical sensing, and industrial process control. On the other hand,flow injection analysis (FIA is advisable for the rapid analysis of microliter volume samples and canbe interfaced directly to the chemical process. The FIA has become a widespread automatic analyticalmethod for more reasons; mainly due to the simplicity and low cost of the setups, their versatility, andease of assembling. In this paper, an overview of flow injection determinations by using opticalchemical sensors is provided, and instrumentation, sensor design, and applications are discussed. Thiswork summarizes the most relevant manuscripts from 1980 to date referred to analysis using opticalchemical sensors in FIA.

Coupled Viscous Fluid Flow and Joint Deformation Analysis for Grout Injection in a Rock Joint

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Kim, Hyung-Mok; Lee, Jong-Won; Yazdani, Mahmoud; Tohidi, Elham; Nejati, Hamid Reza; Park, Eui-Seob

2018-02-01

Fluid flow modeling is a major area of interest within the field of rock mechanics. The main objective of this study is to gain insight into the performance of grout injection inside jointed rock masses by numerical modeling of grout flow through a single rock joint. Grout flow has been widely simulated using non-Newtonian Bingham fluid characterized by two main parameters of dynamic viscosity and shear yield strength both of which are time dependent. The increasing value of these properties with injection time will apparently affect the parameters representing the grouting performance including grout penetration length and volumetric injection rate. In addition, through hydromechanical coupling a mutual influence between the injection pressure from the one side and the joint opening/closing behavior and the aperture profile variation on the other side is anticipated. This is capable of producing a considerable impact on grout spread within the rock joints. In this study based on the Bingham fluid model, a series of numerical analysis has been conducted using UDEC to simulate the flow of viscous grout in a single rock joint with smooth parallel surfaces. In these analyses, the time-dependent evolution of the grout fluid properties and the hydromechanical coupling have been considered to investigate their impact on grouting performance. In order to verify the validity of these simulations, the results of analyses including the grout penetration length and the injection flow rate were compared with a well-known analytical solution which is available for the simple case of constant grout properties and non-coupled hydraulic analysis. The comparison demonstrated that the grout penetration length can be overestimated when the time-dependent hardening of grout material is not considered. Moreover, due to the HM coupling, it was shown that the joint opening induced by injection pressure may have a considerable increasing impression on the values of penetration length and

Simultaneous Voltammetric/Amperometric Determination of Sulfide and Nitrite in Water at BDD Electrode

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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.

New method for simultaneous determination of Fe(II) and Fe(III) in water using flow injection technique

International Nuclear Information System (INIS)

Kozak, J.; Gutowski, J.; Kozak, M.; Wieczorek, M.; Koscielniak, P.

2010-01-01

The method exploits the possibilities of flow injection gradient titration in a system of reversed flow with spectrophotometric detection. In the developed approach a small amount of titrant (EDTA) is injected into a stream of sample containing a mixture of indicators (sulfosalicylic acid and 1,10-phenanthroline). In acid environment sulfosalicylic acid forms a complex with Fe(III), whereas 1,10-phenanthroline forms a complex with Fe(II). Measurements are performed at wavelength λ = 530 nm when radiation is absorbed by both complexes. After injection EDTA replaces sulfosalicylic acid and forms with Fe(III) more stable colourless complex. As a result, a characteristic 'cut off' peak is registered with a width corresponding to the Fe(III) concentration and with a height corresponding to the Fe(II) concentration. Calibration was performed by titration of four two-component standard solutions of the Fe(II)/Fe(III) concentrations established in accordance with 2 2 factorial plan. The method was tested with the use of synthetic samples and then it was applied to the analysis of water samples taken from artesian wells. Under optimized experimental conditions Fe(II) and Fe(III) were determined with precision less than 0.8 and 2.5% (RSD) and accuracy less than 3.2 and 5.1% (relative error) within the concentration ranges of 0.1-3.0 and 0.9-3.5 mg L -1 of both analytes, respectively.

The efficacy of IntraFlow intraosseous injection as a primary anesthesia technique.

Science.gov (United States)

Remmers, Todd; Glickman, Gerald; Spears, Robert; He, Jianing

2008-03-01

The purpose of this study was to compare the efficacy of intraosseous injection and inferior alveolar (IA) nerve block in anesthetizing mandibular posterior teeth with irreversible pulpitis. Thirty human subjects were randomly assigned to receive either intraosseous injection using the IntraFlow system (Pro-Dex Inc, Santa Ana, CA) or IA block as the primary anesthesia method. Pulpal anesthesia was evaluated via electric pulp testing at 4-minute intervals for 20 minutes. Two consecutive 80/80 readings were considered successful pulpal anesthesia. Anesthesia success or failure was recorded and groups compared. Intraosseous injection provided successful anesthesia in 13 of 15 subjects (87%). The IA block provided successful anesthesia in 9 of 15 subjects (60%). Although this difference was not statistically significant (p = 0.2148), the results of this preliminary study indicate that the IntraFlow system can be used as the primary anesthesia method in teeth with irreversible pulpitis to achieve predictable pulpal anesthesia.

Jet flow analysis of liquid poison injection in a CANDU reactor using source term

International Nuclear Information System (INIS)

Chae, Kyung Myung; Choi, Hang Bok; Rhee, Bo Wook

2001-01-01

For the performance analysis of Canadian deuterium uranium (CANDU) reactor shutdown system number 2 (SDS2), a computational fluid dynamics model of poison jet flow has been developed to estimate the flow field and poison concentration formed inside the CANDU reactor calandria. As the ratio of calandria shell radius over injection nozzle hole diameter is so large (1055), it is impractical to develop a full-size model encompassing the whole calandria shell. In order to reduce the model to a manageable size, a quarter of one-pitch length segment of the shell was modeled using symmetric nature of the jet; and the injected jet was treated as a source term to avoid the modeling difficulty caused by the big difference of the hole sizes. For the analysis of an actual CANDU-6 SDS2 poison injection, the grid structure was determined based on the results of two-dimensional real- and source-jet simulations. The maximum injection velocity of the liquid poison is 27.8 m/s and the mass fraction of the poison is 8000 ppm (mg/kg). The simulation results have shown well-established jet flow field. In general, the jet develops narrowly at first but stretches rapidly. Then, the flow recirculates a little in r-x plane, while it recirculates largely in r-θ plane. As the time goes on, the adjacent jets contact each other and form a wavy front such that the whole jet develops in a plate form. his study has shown that the source term model can be effectively used for the analysis of the poison injection and the simulation result of the CANDU reactor is consistent with the model currently being used for the safety analysis. In the future, it is strongly recommended to analyze the transient (from helium tank to injection nozzle hole) of the poison injection by applying Bernoulli equation with real boundary conditions

Fluoroscopically Guided Extraforaminal Cervical Nerve Root Blocks: Analysis of Epidural Flow of the Injectate with Respect to Needle Tip Position

Science.gov (United States)

Shipley, Kyle; Riew, K. Daniel; Gilula, Louis A.

2013-01-01

Study Design Retrospective evaluation of consecutively performed fluoroscopically guided cervical nerve root blocks. Objective To describe the incidence of injectate central epidural flow with respect to needle tip position during fluoroscopically guided extraforaminal cervical nerve root blocks (ECNRBs). Methods Between February 19, 2003 and June 11, 2003, 132 consecutive fluoroscopically guided ECNRBs performed with contrast media in the final injected material (injectate) were reviewed on 95 patients with average of 1.3 injections per patient. Fluoroscopic spot images documenting the procedure were obtained as part of standard quality assurance. An independent observer not directly involved in the procedures retrospectively reviewed the images, and the data were placed into a database. Image review was performed to determine optimal needle tip positioning for injectate epidural flow. Results Central epidural injectate flow was obtained in only 28.9% of injections with the needle tip lateral to midline of the lateral mass (zone 2). 83.8% of injectate went into epidural space when the needle tip was medial to midline of the lateral mass (zone 3). 100% of injectate flowed epidurally when the needle tip was medial to or at the medial cortex of the lateral mass (zone 4). There was no statistically significant difference with regards to central epidural flow and the needle tip position on lateral view. Conclusion To ensure central epidural flow with ECNRBs one must be prepared to pass the needle tip medial to midplane of the lateral mass or to medial cortex of the lateral mass. Approximately 16% of ECNRBs with needle tip medial to midline of the lateral mass did not flow into epidural space. One cannot claim a nerve block is an epidural block unless epidural flow of injectate is observed. PMID:24494176

Amperometric Carbon Fiber Nitrite Microsensor for In Situ Biofilm Monitoring

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A highly selective needle type solid state amperometric nitrite microsensor based on direct nitrite oxidation on carbon fiber was developed using a simplified fabrication method. The microsensor’s tip diameter was approximately 7 µm, providing a high spatial resolution of at lea...

Flow-injection determination of thorium and uranium after on-line ion-exchange preconcentration in Dowex 50-X8

International Nuclear Information System (INIS)

Perez Pavon, J.L.; Garcia Pinto, C.G.; Rodriguez Garcia, Estrella; Moreno Cordero, Bernardo

1992-01-01

The preconcentration of thorium and uranium on Dowex 50-X8 was studied as a method for the preconcentration of these cations prior to their determination by flow injection with spectrophotometric detection using Arsenazo III in 3.6 M HCl stabilized with Triton X-100 as chromogenic reagent. The preconcentration device is a minicolumn included in the sample loop of the injection valve. A second valve contains a reducing minicolumn filled with lead powder to reduce U(VI) to U(IV) before the confluence of the sample with the reagent stream. The method can be applied to samples containing 0.5-100 μg l -1 and was tested with different spiked water samples. (author). 15 refs.; 3 figs.; 3 tabs

Detection of Benzoic Acid by an Amperometric Inhibitor Biosensor Based on Mushroom Tissue Homogenate

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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.

Chitosan-guar gum-silver nanoparticles hybrid matrix with immobilized enzymes for fabrication of beta-glucan and glucose sensing photometric flow injection system.

Science.gov (United States)

Bagal-Kestwal, Dipali R; Kestwal, Rakesh Mohan; Hsieh, Wen-Ting; Chiang, Been-Huang

2014-01-01

Simple and fast photometric flow injection analysis system was developed for sensing of β-1,3-glucan from medicinal mushroom Ganoderma lucidum during fermentation. For this purpose, the chitosan-guar gum-silver nanoparticle-beta glucanase (Ch-GG-AgNPs-βG) beads and Ch-GG-AgNPs-GOD (glucose oxidase) beads were prepared. The bead packed mini-columns were then used to assemble a flow injection analysis (FIA) system for the detection of β-(1→3)-d-glucan biomarker or glucose. This colorimetric flow system can detect glucose and glucan with detection limits as low as 50ngmL(-1) and 100ngmL(-1) (S/N=3), respectively. The analysis time of this FIA was approximately 40s, which is faster than the previously reported glucan sensors. The glucose and glucan calibration curves were obtained in the range of 0.25-1.25μgmL(-1) (R(2)=0.988) and 0.2-1.0μgmL(-1)(R(2)=0.979), respectively. The applicability of the nano-bio-composite FIA sensor system for spiked and real β-(1→3)-d-glucan samples were tested, and the accuracy of the results were greater than 95%. Thus, the designed FIA provides a simple, interference free and rapid tool for monitoring glucose and β-glucan content, which can be used for various food samples with a little modification. Copyright © 2013 Elsevier B.V. All rights reserved.

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.

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

International Nuclear Information System (INIS)

Shahida, Shabnam; Khan, Muhammad Haleem; Ali, Akbar

2014-01-01

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"-"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"-"1. The trapped complex was then eluted with 3.6 mol L"-"1 HCl at a flow rate of 4.9 mL min"-"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"-"1 HCl stabilized with 1 % triton X-100, 4.9 mL min"-"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"-"1, the enhancement factor was 97, the detection limit was 0.25 μg L"-"1, and the precision expressed as relative standard deviation was 1.08 % (at 50 μg L"-"1), whereas for 300 s of the preconcentration time and a sample frequency of 10 h"-"1, the enhancement factor of 357, the detection limit (3s) of 0.069 μg L"-"1 and the precision of 1.32 % (at 10 μg L"-"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.

An experimental study of the flow characteristics of fluidic device in a passive safety injection tank

International Nuclear Information System (INIS)

Cho, Seok; Song, Chul Hwa; Won, Suon Yeon; Min, Kyong Ho; Chung, Moon Ki

1998-01-01

It is considered to adopt passive safety injection tank (SIT) as a enhanced safety feature in KNGR. Passive SIT employs a vortex chamber as a fluidic device, which control injection flow rate passively by the variation of flow resistance produced by vortex intensity within the vortex chamber. To investigate the flow characteristics of the vortex chamber many tests have been carried out by using small-scale test facility. In this report the effects of geometric parameters of vortex chamber on discharge flow characteristics and the velocity measurement result of flow field, measured by PIV, are presented and discussed. (author). 25 refs., 11 tabs., 31 figs

Enhanced amperometric response of a glucose oxidase and horseradish peroxidase based bienzyme glucose biosensor modified with a film of polymerized toluidine blue containing reduced graphene oxide

International Nuclear Information System (INIS)

Wang, Fang; Gong, Wencheng; Wang, Lili; Chen, Zilin

2015-01-01

Reduced graphene oxide (RGO) was used to construct a bienzyme biosensor containing horseradish peroxidase (HRP) and glucose oxidase (GOx). A poly(toluidine blue) (pTB) film containing RGO acted as both enzyme immobilization matrix and electron transfer mediator. The bienzyme biosensor was characterized by electrochemical techniques and displays a highly sensitive amperometric response to glucose and hydrogen peroxide (H 2 O 2 ) at a potential as low as −0.1 V (vs. SCE). It is shown that use of RGO causes a strong enhancement on the amperometric responses. H 2 O 2 formed by the action of GOx in the presence of oxygen can be further reduced by HRP in the pTB film contacting the RGO modified electrode. In the absence of oxygen, glucose oxidation proceeds by another mechanism in which electron transfer occurs from GOx to the electrode and with pTB acting as the mediator. Amperometric responses to glucose and H2O2 follow Michaelis-Menten kinetics. The experimental conditions were optimized, and under these conditions glucose can be determined in the 80 μM to 3.0 mM range with a detection limit of 50 μM. H 2 O 2 , in turn, can be quantified in up to 30.0 μM concentration with a detection limit of 0.2 μM. The bienzyme biosensor is reproducible, repeatable and stable. Finally, it has been successfully applied to the determination of glucose in plasma samples. (author)

Flow injection chemiluminescent determination of N-nitrosodimethylamine using photogenerated tris(2,2'-bipyridyl) ruthenium (III)

International Nuclear Information System (INIS)

Perez-Ruiz, Tomas; Martinez-Lozano, Carmen; Tomas, Virginia; Martin, Jesus

2005-01-01

A flow injection configuration was developed and evaluated for the chemiluminescent determination of N-nitrosodimethylamine. The method is based on the on-line cleavage of the N-NO bond of the nitrosamine by irradiation with ultraviolet light. The dimethylamine generated was subsequently reacted with tris(2,2'-bipyridyl) ruthenium (III), which was generated through the on-line photo-oxidation of tris(2,2'-bipyridyl) ruthenium (II) with peroxydisulfate. After selecting the best operating parameters, the emitted light showed a linear relationship with the concentration of N-nitrosodimethylamine between 1.5 and 148 ng ml -1 , with a detection limit of 0.29 ng ml -1 . The repeatability was 1.6% expressed as relative standard deviation (n = 10) and the reproducibility, studied on five consecutive days, was 3.2%. The sample throughput was 50 injections per hour. The method was applied to studying the recoveries of N-nitrosodimethylamine in water and different cured meat products

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

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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...

Label-Free Electrical Detection Using Carbon Nanotube-Based Biosensors

Directory of Open Access Journals (Sweden)

Kenzo Maehashi

2009-07-01

Full Text Available Label-free detections of biomolecules have attracted great attention in a lot of life science fields such as genomics, clinical diagnosis and practical pharmacy. In this article, we reviewed amperometric and potentiometric biosensors based on carbon nanotubes (CNTs. In amperometric detections, CNT-modified electrodes were used as working electrodes to significantly enhance electroactive surface area. In contrast, the potentiometric biosensors were based on aptamer-modified CNT field-effect transistors (CNTFETs. Since aptamers are artificial oligonucleotides and thus are smaller than the Debye length, proteins can be detected with high sensitivity. In this review, we discussed on the technology, characteristics and developments for commercialization in label-free CNT-based biosensors.

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

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.

An amperometric penicillin biosensor with enhanced sensitivity based on co-immobilization of carbon nanotubes, hematein, and β-lactamase on glassy carbon electrode

International Nuclear Information System (INIS)

Chen Bi; Ma Ming; Su Xiaoli

2010-01-01

An amperometric penicillin biosensor with enhanced sensitivity was successfully developed by co-immobilization of multi-walled carbon nanotubes (MWCNTs), hematein, and β-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 μg L -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.

Sheath-flow electrochemical detection of amino acids with a copper wire electrode in capillary electrophoresis.

Science.gov (United States)

Inoue, Junji; Kaneta, Takashi; Imasaka, Totaro

2012-09-01

Here, we report the detection of native amino acids using a sheath-flow electrochemical detector with a working electrode made of copper wire. A separation capillary that was inserted into a platinum tube in the detector acted as a grounded electrode for electrophoresis and as a flow channel for sheath liquid. Sheath liquid flowed outside the capillary to support the transport of the separated analytes to the working electrode for electrochemical detection. The copper wire electrode was aligned at the outlet of the capillary in a wall-jet configuration. Amino acids injected into the capillary were separated following elution from the end of the capillary and detection by the copper electrode. Three kinds of copper electrodes with different diameters-50, 125, and 300 μm-were examined to investigate the effect of the electrode diameter on sensitivity. The peak widths of the analytes were independent of the diameter of the working electrode, while the 300-μm electrode led to a decrease in the signal-to-noise ratio compared with the 50- and 125-μm electrodes, which showed no significant difference. The flow rate of the sheath liquid was also varied to optimize the detection conditions. The limits of detection for amino acids ranged from 4.4 to 27 μM under optimal conditions. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

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.

Automation of radiochemical analysis by flow injection techniques. Am-Pu separation using TRU-resinTM sorbent extraction column

International Nuclear Information System (INIS)

Egorov, O.; Washington Univ., Seattle, WA; Grate, J.W.; Ruzicka, J.

1998-01-01

A rapid automated flow injection analysis (FIA) procedure was developed for efficient separation of Am and Pu from each other and from interfering matrix and radionuclide components using a TRU-resin TM column. Selective Pu elution is enabled via on-column reduction. The separation was developed using on-line radioactivity detection. After the separation had been developed, fraction collection was used to obtain the separated fractions. In this manner, a FIA instrument functions as an automated separation workstation capable of unattended operation. (author)

Continuous-Flow Production of Injectable Liposomes via a Microfluidic Approach

Science.gov (United States)

Zizzari, Alessandra; Bianco, Monica; Perrone, Elisabetta; Amato, Francesco; Maruccio, Giuseppe; Rendina, Filippo; Arima, Valentina

2017-01-01

Injectable liposomes are characterized by a suitable size and unique lipid mixtures, which require time-consuming and nonstraightforward production processes. The complexity of the manufacturing methods may affect liposome solubility, the phase transition temperatures of the membranes, the average particle size, and the associated particle size distribution, with a possible impact on the drug encapsulation and release. By leveraging the precise steady-state control over the mixing of miscible liquids and a highly efficient heat transfer, microfluidic technology has proved to be an effective and direct methodology to produce liposomes. This approach results particularly efficient in reducing the number of the sizing steps, when compared to standard industrial methods. Here, Microfluidic Hydrodynamic Focusing chips were produced and used to form liposomes upon tuning experimental parameters such as lipids concentration and Flow-Rate-Ratios (FRRs). Although modelling evidenced the dependence of the laminar flow on the geometric constraints and the FRR conditions, for the specific formulation investigated in this study, the lipids concentration was identified as the primary factor influencing the size of the liposomes and their polydispersity index. This was attributed to a predominance of the bending elasticity modulus over the vesiculation index in the lipid mixture used. Eventually, liposomes of injectable size were produced using microfluidic one-pot synthesis in continuous flow. PMID:29232873

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

Stability Analysis of High-Speed Boundary-Layer Flow with Gas Injection

Science.gov (United States)

2014-06-01

laminar-turbulent transition on slender bodies in a hypersonic flow at small angles of attack is caused by amplification of acoustic waves trapped in...x decreases and slowly approaches the no-blow distribution. These CFD data demonstrate that the injection strongly affects the near-wall flow...conclusion. Figure 10 shows that the spatial growth rates ( )  are maximal for mode 0 corresponding to the Mack second mode – typical for hypersonic

Theoretical considerations of Flow Injection Analysis in the Absence of Chemical Reactions

DEFF Research Database (Denmark)

Andersen, Jens Enevold Thaulov

2000-01-01

The fundamental mechanism of flow injection analysis (FIA) is assumed to be simple dissusion and the response of the detector is included in a model description that provide information about the shape of the FIA peak in terms of, basically, five parameters. Two of the five parameters are associa...... that any deviation from the features of the present model and the results of a tentative chemical reaction with one of the test compounds, is related to chemical kinetics.......The fundamental mechanism of flow injection analysis (FIA) is assumed to be simple dissusion and the response of the detector is included in a model description that provide information about the shape of the FIA peak in terms of, basically, five parameters. Two of the five parameters...

Determination of tellurium in lead and lead alloy using flow injection-hydride generation atomic absorption spectrometry

International Nuclear Information System (INIS)

Mesko, Marcia F.; Pozebon, Dirce; Flores, Erico M.M.; Dressler, Valderi L.

2004-01-01

A method based on flow injection-hydride generation atomic absorption spectrometry (FI-HG AAS) for the determination of trace amount of Te in lead and lead alloy is described. A flow injection system (FI) and related analytical parameters as well as Te determination and interference caused by Pb, Bi and Ag on Te were investigated. The Pb interference could be overcome by using a small sample volume, while the Bi interference could be overcome by thiourea. However, it was not possible to minimise the interference caused by Ag on Te. The optimised conditions for Te determination in the analysed samples were: 6 mol l -1 HCl as sample carrier solution, 0.75% (m/v) sodium tetrahydroborate as Te reductant, 40 μl of sample solution, and 200 ml min -1 Ar flow rate as carrier gas. The limit of quantification (LOQ) was 1.0 μg g -1 Te (using 250 mg of sample in 50 ml final solution), the limit of detection (LOD) was 2.5 μg l -1 and the relative standard deviation (RSD) was 6% for five consecutive measurements of sample solution. The standard addition calibration method was used. Relatively high sample throughput (ca. 45 sample runs can be performed in a working hour), reduced sample manipulation since matrix separation is not necessary, and minor waste generation are the main advantages of the proposed method for Te determination by FI-HG AAS

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.

On-line determination of glucose and lactate concentrations in animal cell culture based on fibre optic detection of oxygen in flow-injection analysis.

Science.gov (United States)

Dremel, B A; Li, S Y; Schmid, R D

1992-01-01

A flow-injection analysis (FIA) system based on fibre optic detection of oxygen consumption using immobilized glucose oxidase (GOD) and lactate oxidase (LOD) is described for the on-line monitoring of glucose and lactate concentrations in animal cell cultures. The consumption of oxygen was determined via dynamic quenching by molecular oxygen of the fluorescence of an indicator. GOD and LOD were immobilized on controlled pore glass (CPG) in enzyme reactors which were directly linked to a specially designed fibre optic flow-through cell covering the oxygen optrode. The system is linear for 0-30 mM glucose, with an r.s.d. of 5% at 30 mM (five measurements) and for 0-30 mM lactate, with an r.s.d. of 5% at 30 mM (five measurements). The enzyme reactors used were stable for more than 4 weeks in continuous operation, and it was possible to analyse up to 20 samples per hour. The system has been successfully applied to the on-line monitoring of glucose and lactate concentrations of an animal cell culture designed for the production of recombinant human antithrombine III (AT-III). Results of the on-line measurement obtained by the FIA system were compared with the off-line results obtained by a glucose and lactate analyser from Yellow Springs Instrument Company (YSI).

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

In this work the sensitivity-increasing effect of single-walled carbon nanotubes (SWCNTs) in amperometric biosensors, depending on their average length distribution, was studied. For this purpose the SWCNTs were oxidatively shortened and subsequently length separated by size exclusion...

Nafion/lead nitroprusside nanoparticles modified carbon ceramic electrode as a novel amperometric sensor for L-cysteine.

Science.gov (United States)

Razmi, H; Heidari, H

2009-05-01

This work describes the electrochemical and electrocatalytic properties of carbon ceramic electrode (CCE) modified with lead nitroprusside (PbNP) nanoparticles as a new electrocatalyst material. The structure of deposited film on the CCE was characterized by energy dispersive X-ray (EDX), Fourier transform infrared (FTIR), and scanning electron microscopy (SEM). The cyclic voltammogram (CV) of the PbNP modified CCE showed two well-defined redox couples due to [Fe(CN)5NO](3-)/[Fe(CN)5NO](2-) and Pb(IV)/Pb(II) redox reactions. The modified electrode showed electrocatalytic activity toward the oxidation of L-cysteine and was used as an amperometric sensor. Also, to reduce the fouling effect of L-cysteine and its oxidation products on the modified electrode, a thin film of Nafion was coated on the electrode surface. The sensor response was linearly changed with L-cysteine concentration in the range of 1 x 10(-6) to 6.72 x 10(-5)mol L(-1) with a detection limit (signal/noise ratio [S/N]=3) of 0.46 microM. The sensor sensitivity was 0.17 microA (microM)(-1), and some important advantages such as simple preparation, fast response, good stability, interference-free signals, antifouling properties, and reproducibility of the sensor for amperometric determination of L-cysteine were achieved.

Elemental speciation via high-performance liquid chromatography combined with inductively coupled plasma atomic emission spectroscopic detection: application of a direct injection nebulizer

International Nuclear Information System (INIS)

LaFreniere, K.E; Fassel, V.A.; Eckels, D.E.

1987-01-01

An evaluation is presented of a direct injection nebulizer (DIN) interfaced to a high-performance liquid chromatograph (HPLC) with inductively coupled plasma atomic emission spectroscopic (ICP-AES) detection for simultaneous multielement speciation. The limits of detection (LODs) obtained with the DIN interface in the HPLC mode were found to be comparable to those obtained by continuous-flow sample introduction into the ICP, or inferior by up to only a factor of 4. In addition, the DIN allowed for the direct injection into the ICP of a variety of common HPLC solvents (up to 100% methanol, acetonitrile, methyl isobutyl ketone, pyridine, and water). The HPLC-DIN-ICP-AES system was compared to other HPLC-atomic spectroscopic detection techniques and was found to offer substantial improvement over the alternative on-line, detection methods in terms of LODs. Representative applications of the HPLC-DIN-ICP-AES system to the elemental speciation of coal process streams, shale oil, solvent refined coal, and crude oil are presented

Determination of albumin in bronchoalveolar lavage fluid by flow-injection fluorometry using chromazurol S.

Science.gov (United States)

Sato, Takaji; Saito, Yoshihiro; Chikuma, Masahiko; Saito, Yutaka; Nagai, Sonoko

2008-03-01

A highly sensitive flow injection fluorometry for the determination of albumin was developed and applied to the determination of albumin in human bronchoalveolar lavage fluids (BALF). This method is based on binding of chromazurol S (CAS) to albumin. The calibration curve was linear in the range of 5-200 microg/ml of albumin. A highly linear correlation (r=0.986) was observed between the albumin level in BALF samples (n=25) determined by the proposed method and by a conventional fluorometric method using CAS (CAS manual method). The IgG interference was lower in the CAS flow injection method than in the CAS manual method. The albumin level in BALF collected from healthy volunteers (n=10) was 58.5+/-13.1 microg/ml. The albumin levels in BALF samples obtained from patients with sarcoidosis and idiopathic pulmonary fibrosis were increased. This finding shows that the determination of albumin levels in BALF samples is useful for investigating lung diseases and that CAS flow injection method is promising in the determination of trace albumin in BALF samples, because it is sensitive and precise.

Immobilization of Tyrosinase on (3-Aminopropyltriethoxysilane-Functionalized Carbon Felt-Based Flow-Through Detectors for Electrochemical Detection of Phenolic Compounds

Directory of Open Access Journals (Sweden)

Zheng Zhou

2017-07-01

Full Text Available Tyrosinase (TYR was covalently immobilized onto amino-functionalized carbon felt (CF surface via glutaraldehyde (GA. Prior to the TYR-immobilization, primary amino group was introduced to the CF surface by treatment with 3-aminopropyltriethoxysilane (APTES. The resulting TYR-immobilized CF was used as a working electrode unit of an electrochemical flow-through detector for mono- and di-phenolic compounds (i.e., catechol, p-cresol, phenol and p-chlorophenol. Additionally, flow injection peaks based on electroreduction of the enzymatically produced o-quinone species were detected at −0.05 V vs. Ag/AgCl. The resulting TYR/GA/APTES/CF biosensor responded well to all compounds tested with limits of detection range from 7.5 to 35 nmol−1 (based on three times S/N ratio. Moreover, such modified electrode exhibits good stability and reproducibility for catechol. No serious degradation of the peak current was found over 30 consecutive injections.

Non-darcy flow behavior mean high-flux injection wells in porous and fractured formations

Energy Technology Data Exchange (ETDEWEB)

Wu, Yu-Shu

2003-04-25

This paper presents a study of non-Darcy fluid flow through porous and fractured rock, which may occur near wells during high-flux injection of waste fluids into underground formations. Both numerical and analytical models are used in this study. General non-Darcy flow is described using the Forchheimer equation, implemented in a three-dimensional, multiphase flow reservoir simulator. The non-Darcy flow through a fractured reservoir is handled using a general dual continuum approach, covering commonly used conceptual models, such as double porosity, dual permeability, explicit fracture, etc. Under single-phase flow conditions, an approximate analytical solution, as an extension of the Warren-Root solution, is discussed. The objectives of this study are (1) to obtain insights into the effect of non-Darcy flow on transient pressure behavior through porous and fractured reservoirs and (2) to provide type curves for well test analyses of non-Darcy flow wells. The type curves generated include various types of drawdown, injection, and buildup tests with non-Darcy flow occurring in porous and fractured reservoirs. In addition, non-Darcy flow into partially penetrating wells is also considered. The transient-pressure type curves for flow in fractured reservoirs are based on the double-porosity model. Type curves provided in this work for non-Darcy flow in porous and fractured reservoirs will find their applications in well test interpretation using a type-curve matching technique.

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).

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

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

Science.gov (United States)

Jarukanont, Daungruthai; Bonifas Arredondo, Imelda; Femat, Ricardo; Garcia, Martin E

2015-01-01

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 also show that

Continuous-Flow Production of Injectable Liposomes via a Microfluidic Approach

Directory of Open Access Journals (Sweden)

Alessandra Zizzari

2017-12-01

Full Text Available Injectable liposomes are characterized by a suitable size and unique lipid mixtures, which require time-consuming and nonstraightforward production processes. The complexity of the manufacturing methods may affect liposome solubility, the phase transition temperatures of the membranes, the average particle size, and the associated particle size distribution, with a possible impact on the drug encapsulation and release. By leveraging the precise steady-state control over the mixing of miscible liquids and a highly efficient heat transfer, microfluidic technology has proved to be an effective and direct methodology to produce liposomes. This approach results particularly efficient in reducing the number of the sizing steps, when compared to standard industrial methods. Here, Microfluidic Hydrodynamic Focusing chips were produced and used to form liposomes upon tuning experimental parameters such as lipids concentration and Flow-Rate-Ratios (FRRs. Although modelling evidenced the dependence of the laminar flow on the geometric constraints and the FRR conditions, for the specific formulation investigated in this study, the lipids concentration was identified as the primary factor influencing the size of the liposomes and their polydispersity index. This was attributed to a predominance of the bending elasticity modulus over the vesiculation index in the lipid mixture used. Eventually, liposomes of injectable size were produced using microfluidic one-pot synthesis in continuous flow.

Polymeric microchip for the simultaneous determination of anions and cations by hydrodynamic injection using a dual-channel sequential injection microchip electrophoresis system.

Science.gov (United States)

Gaudry, Adam J; Nai, Yi Heng; Guijt, Rosanne M; Breadmore, Michael C

2014-04-01

A dual-channel sequential injection microchip capillary electrophoresis system with pressure-driven injection is demonstrated for simultaneous separations of anions and cations from a single sample. The poly(methyl methacrylate) (PMMA) microchips feature integral in-plane contactless conductivity detection electrodes. A novel, hydrodynamic "split-injection" method utilizes background electrolyte (BGE) sheathing to gate the sample flows, while control over the injection volume is achieved by balancing hydrodynamic resistances using external hydrodynamic resistors. Injection is realized by a unique flow-through interface, allowing for automated, continuous sampling for sequential injection analysis by microchip electrophoresis. The developed system was very robust, with individual microchips used for up to 2000 analyses with lifetimes limited by irreversible blockages of the microchannels. The unique dual-channel geometry was demonstrated by the simultaneous separation of three cations and three anions in individual microchannels in under 40 s with limits of detection (LODs) ranging from 1.5 to 24 μM. From a series of 100 sequential injections the %RSDs were determined for every fifth run, resulting in %RSDs for migration times that ranged from 0.3 to 0.7 (n = 20) and 2.3 to 4.5 for peak area (n = 20). This system offers low LODs and a high degree of reproducibility and robustness while the hydrodynamic injection eliminates electrokinetic bias during injection, making it attractive for a wide range of rapid, sensitive, and quantitative online analytical applications.

Entropy Generation in a Rotating Couette Flow with Suction/Injection

Directory of Open Access Journals (Sweden)

S. Das

2015-05-01

Full Text Available The present paper is concerned with an analytical study of entropy generation in viscous incompressible Couette flow with suction/injection in a rotating frame of reference. One of the plate is held at rest and the other one moves with an uniform velocity.The flow induced by the moving plate. An exact solution of governing equations has been obtained in closed form. The entropy generation number and the Bejan number are also obtained. The influences of each of the governing parameters on velocity, temperature, entropy generation and Bejan number are discussed with the help of graphs.

Sibutramine selective electrodes for batch and flow injection determinations in pharmaceutical preparations.

Science.gov (United States)

Zayed, S I M; Issa, Y M

2010-01-01

The construction and electrochemical response characteristics of two new polyvinyl chloride (PVC) membrane sensors for the determination of sibutramine hydrochloride were described. The sensors are based on the ion association complexes of sibutramine with sodium tetraphenylborate (NaTPB) or phosphotungstic acid (PTA) using dibutyl phthalate as plasticizing solvent. The sensors display a fast, stable response over the concentration range 3.84 x 10(-5)-1.00 x 10(-2) M sibutramine hydrochloride monohydrate (SibuCl), with cationic slopes of 57.7 +/- 0.57 and 59.7 +/- 1.79 mV concentration decade(-1) and detection limits of 8.91 x 10(-6) and 1.47 x 10(-5) M in case of sibutramine-tetraphenylborate (Sibu-TPB) and sibutramine-phosphotungstate ((Sibu)(3)-PT), respectively. The proposed sensors have been successfully applied for the determination of sibutramine hydrochloride in Regitrim capsules in batch and flow injection (FI) conditions.

Detecting fetomaternal hemorrhage by flow cytometry

DEFF Research Database (Denmark)

Dziegiel, Morten Hanefeld; Nielsen, Leif Kofoed; Berkowicz, Adela

2006-01-01

The aim of this review is to summarize the most recent developments in the area of detection of fetomaternal hemorrhage by flow cytometry.......The aim of this review is to summarize the most recent developments in the area of detection of fetomaternal hemorrhage by flow cytometry....

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.

Construction of ferrocene modified conducting polymer based amperometric urea biosensor.

Science.gov (United States)

Dervisevic, Muamer; Dervisevic, Esma; Senel, Mehmet; Cevik, Emre; Yildiz, Huseyin Bekir; Camurlu, Pınar

2017-07-01

Herein, an electrochemical urea sensing bio-electrode is reported that has been constructed by firstly electropolymerizing 4-(2,5-Di(thiophen-2-yl)-1H-pyrrol-1-yl)aniline monomer (SNS-Aniline) on Pencil Graphite Electrode (PGE), then modifying the polymer coated electrode surface with di-amino-Ferrocene (DAFc) as the mediator, and lastly Urease enzyme through glutaraldehyde crosslinking. The effect of pH, temperature, polymer thickness, and applied potential on the electrode current response was investigated besides performing storage and operational stability experiments with the interference studies. The resulting urea biosensor's amperometric response was linear in the range of 0.1-8.5mM with the sensitivity of 0.54μA/mM, detection limit of 12μM, and short response time of 2s. The designed bio-electrode was tested with real human blood and urine samples where it showed excellent analytical performance with insignificant interference. Copyright © 2017 Elsevier Inc. All rights reserved.

Flow-injection analysis of nitrate by reduction to nitrite and gas-phase molecular absorption spectrometry

Energy Technology Data Exchange (ETDEWEB)

Haghighi, B.; Tavassoli, A. [Dept. of Chemistry, Inst. for Advanced Studies in Basic Sciences, Zanjan (Iran)

2001-12-01

Two flow-injection manifolds have been investigated for the determination of nitrate. These manifolds are based on the reduction of nitrate to nitrite and determination of nitrite by gas-phase molecular absorption spectrophotometry. Nitrate sample solution (300 {mu}L) which is injected to the flow line, is reduced to nitrite by reaction with hydrazine or passage through the on-line copperized cadmium (Cd-Cu) reduction column. The nitrite produced reacts with a stream of hydrochloric acid and the evolved gases are purged into the stream of O{sub 2}carrier gas. The gaseous phase is separated from the liquid phase using a gas-liquid separator and then swept into a flow-through cell which has been positioned in the cell compartment of an UV-visible spectrophotometer. The absorbance of the gaseous phase is measured at 204.7 nm. A linear relationship was obtained between the intensity of absorption signals and concentration of nitrate when Cd-Cu reduction method was used, but a logarithmic relationship was obtained when the hydrazine reduction method was used. By use of the Cd-Cu reduction method, up to 330 {mu}g of nitrate was determined. The limit of detection was 2.97 {mu}g nitrate and the relative standard deviations for the determination of 12.0, 30.0 and 150 {mu}g nitrate were 3.32, 3.87 and 3.6%, respectively. Maximum sampling rate was approximately 30 samples per hour. The Cd-Cu reduction method was applied to the determination of nitrate and the simultaneous determination of nitrate and nitrite in meat products, vegetables, urine, and a water sample. (orig.)

Water injection profiling

International Nuclear Information System (INIS)

Arnold, D.M.

1982-01-01

A method of neutron-gamma logging is described, in which water, injected in a cased well borehole with peforations, is irradiated with neutrons of 10 MeV or greater, and subsequent gamma radiation is detected by a pair of detectors along the borehole. Counting rates of detectors are analyzed in terms of two gamma ray energy windows. Linear flow velocity of fluid moving downward within the casing is used in conjunction with count rate data to determine volume flow rates of water moving in other directions. Apparatus includes a sonde with a neutron source and appropriate gamma sensors

Optimization of a flow injection analysis system for multiple solvent extraction

International Nuclear Information System (INIS)

Rossi, T.M.; Shelly, D.C.; Warner, I.M.

1982-01-01

The performance of a multistage flow injection analysis solvent extraction system has been optimized. The effect of solvent segmentation devices, extraction coils, and phase separators on performance characteristics is discussed. Theoretical consideration is given to the effects and determination of dispersion and the extraction dynamics within both glass and Teflon extraction coils. The optimized system has a sample recovery similar to an identical manual procedure and a 1.5% relative standard deviation between injections. Sample throughput time is under 5 min. These characteristics represent significant improvements over the performance of the same system before optimization. 6 figures, 2 tables

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.

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.

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.

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.

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.

Development of a Telemetric, Miniaturized Electrochemical Amperometric Analyzer

OpenAIRE

Jaehyo Jung; Jihoon Lee; Siho Shin; Youn Tae Kim

2017-01-01

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 signa...

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

A Stable Glutamate Biosensor Based on MnO2 Bulk-modified ...

African Journals Online (AJOL)

An amperometric glutamate biosensor was developed using screen-printed carbon electrodes bulk-modified with MnO2 (5%, m:m) onto which glutamate oxidase was immobilized via Nafion(R) film entrapment. The analytical performance of the biosensor was assessed in a flow injection mode and peak heights of the ...

Indications of Segmental Flow in Straight Pipes by Flow Injection with Spectrophotometric Detection

DEFF Research Database (Denmark)

Andersen, Jens Enevold Thaulov

2000-01-01

A procedure of spectrophotometric analysis of fluid flow in pipes is described and its performance is tested on three different dye compounds. The procedure follows measurement and mathematical de-convolution of the signal with an exponential function that is associated with molecular diffusion. ...

Amperometric glucose biosensor based on glucose oxidase dispersed in multiwalled carbon nanotubes/graphene oxide hybrid biocomposite

International Nuclear Information System (INIS)

Palanisamy, Selvakumar; Cheemalapati, Srikanth; Chen, Shen-Ming

2014-01-01

An amperometric glucose biosensor based on enhanced and fast direct electron transfer (DET) of glucose oxidase (GOx) at enzyme dispersed multiwalled carbon nanotubes/graphene oxide (MWCNT/GO) hybrid biocomposite was developed. The fabricated hybrid biocomposite was characterized by transmission electron microscopy (TEM), Raman and infrared spectroscopy (IR). The TEM image of hybrid biocomposite reveals that a thin layer of GOx was covered on the surface of MWCNT/GO hybrid composite. IR results validate that the hybrid biocomposite was formed through the electrostatic interactions between GOx and MWCNT/GO hybrid composite. Further, MWCNT/GO hybrid composite has also been characterized by TEM and UV–visible spectroscopy. A pair of well-defined redox peak was observed for GOx immobilized at the hybrid biocomposite electrode than that immobilized at the MWCNT modified electrode. The electron transfer rate constant (K s ) of GOx at the hybrid biocomposite was calculated to be 11.22 s −1 . The higher K s value revealed that fast DET of GOx occurred at the electrode surface. Moreover, fabricated biosensor showed a good sensitivity towards glucose oxidation over a linear range 0.05–23.2 mM. The limit of detection (LOD) was estimated to be 28 μM. The good features of the proposed biosensor could be used for the accurate detection of glucose in the biological samples. - Highlights: • An amperometric glucose biosensor has been developed at MWCNT/GO hybrid biocomposite. • Enhanced and fast direct electron transfer kinetics of glucose oxidase has been achieved at hybrid biocomposite. • Hybrid biocomposite has been characterized by TEM, IR and Raman spectroscopy. • Highly sensitive and selective for glucose determination

Amperometric glucose biosensor based on glucose oxidase dispersed in multiwalled carbon nanotubes/graphene oxide hybrid biocomposite

Energy Technology Data Exchange (ETDEWEB)

Palanisamy, Selvakumar; Cheemalapati, Srikanth; Chen, Shen-Ming, E-mail: smchen78@ms15.hinet.net

2014-01-01

An amperometric glucose biosensor based on enhanced and fast direct electron transfer (DET) of glucose oxidase (GOx) at enzyme dispersed multiwalled carbon nanotubes/graphene oxide (MWCNT/GO) hybrid biocomposite was developed. The fabricated hybrid biocomposite was characterized by transmission electron microscopy (TEM), Raman and infrared spectroscopy (IR). The TEM image of hybrid biocomposite reveals that a thin layer of GOx was covered on the surface of MWCNT/GO hybrid composite. IR results validate that the hybrid biocomposite was formed through the electrostatic interactions between GOx and MWCNT/GO hybrid composite. Further, MWCNT/GO hybrid composite has also been characterized by TEM and UV–visible spectroscopy. A pair of well-defined redox peak was observed for GOx immobilized at the hybrid biocomposite electrode than that immobilized at the MWCNT modified electrode. The electron transfer rate constant (K{sub s}) of GOx at the hybrid biocomposite was calculated to be 11.22 s{sup −1}. The higher K{sub s} value revealed that fast DET of GOx occurred at the electrode surface. Moreover, fabricated biosensor showed a good sensitivity towards glucose oxidation over a linear range 0.05–23.2 mM. The limit of detection (LOD) was estimated to be 28 μM. The good features of the proposed biosensor could be used for the accurate detection of glucose in the biological samples. - Highlights: • An amperometric glucose biosensor has been developed at MWCNT/GO hybrid biocomposite. • Enhanced and fast direct electron transfer kinetics of glucose oxidase has been achieved at hybrid biocomposite. • Hybrid biocomposite has been characterized by TEM, IR and Raman spectroscopy. • Highly sensitive and selective for glucose determination.

A Simple and Rapid Flow-Injection Chemiluminescence Method for the Determination of Noscapine with Ru(phen)32+-Ce(4) System

International Nuclear Information System (INIS)

Rezaei, B.; Mokhtari, A.; Khayamian, T.

2007-01-01

A new flow injection chemiluminescence (CL) system was used for the determination of noscapine. This technique is based on the reduction effect of noscapine on the Ru(phen) 3 3+ , which is produced by reaction between Ru(phen) 3 2+ and acidic Ce(4) solutions, and this rapid reduction produces strong CL. Calibration plots were linear over the range of 3.0x10 -7 -2.0x10 -6 mol L -1 and 2.0x10 -6 -2.0x10 -4 mol L -1 . The CL intensity was so high, that it is able to produce a detection limit of 6.6x10 -8 M noscapine (3σ). The relative standard deviation of 2.0x10 -6 M noscapine was 1.0% (n=10). The proposed method was successfully applied for the flow injection determination of noscapine in cough and Tonin syrup samples. The results of real sample analyses show good recovery percentages (97.3-102.4%). The minimum sampling rate was 100 samples per hour

Bubble-size distributions produced by wall injection of air into flowing freshwater, saltwater and surfactant solutions

Science.gov (United States)

Winkel, Eric S.; Ceccio, Steven L.; Dowling, David R.; Perlin, Marc

2004-12-01

As air is injected into a flowing liquid, the resultant bubble characteristics depend on the properties of the injector, near-wall flow, and flowing liquid. Previous research has shown that near-wall bubbles can significantly reduce skin-friction drag. Air was injected into the turbulent boundary layer on a test section wall of a water tunnel containing various concentrations of salt and surfactant (Triton-X-100, Union Carbide). Photographic records show that the mean bubble diameter decreased monotonically with increasing salt and surfactant concentrations. Here, 33 ppt saltwater bubbles had one quarter, and 20 ppm Triton-X-100 bubbles had one half of the mean diameter of freshwater bubbles.

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.

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.

Polypyrrole-based bilayer nitrate amperometric biosensor with an integrated permselective poly-ortho-phenylenediamine layer for exclusion of inorganic interferences.

Science.gov (United States)

Adeloju, Samuel B; Sohail, Manzar

2011-07-15

A bilayer amperometric nitrate biosensor with an integrated permselective layer has been developed for exclusion of inorganic anion and cation interferences. The inner PPy(polypyrrole)-NaR-NADH layer of the biosensor is formed by galvanostatic polymerization of pyrrole (Py) in presence of nitrate reductase (NaR) and nicotinamide adenine dinucleotide (NADH), followed by formation of the outer permselective poly-ortho-phenylenediamine (P-o-PDA) layer by potentiodynamic polymerization of ortho-phenylenediamine (o-PDA). The exclusion efficiency (E(eff)) of the outer layer in rejecting inorganic cation and anion interferences is evaluated by a new proposed relationship. 73-87% and 47-84% of anion and cation interferences, respectively, were efficiently rejected with the permselective layer. Further improvement in the exclusion efficiency for cations was accomplished by combining the use of the outer layer with the addition of 1mM EDTA into the measurement solution. The addition of EDTA improved the E(eff) achieved for cation rejection by 10-40% to give net E(eff) of 89-94%. The inclusion of the outer layer also aided the retention of NaR and NADH in the inner PPy-NaR-NADH layer and, hence, enabled improved amperometric detection of nitrate, achieving a detection limit of 0.20 μM and a linear concentration range of 10-500 μM with a 3.4%rsd (n=10). Copyright © 2011 Elsevier B.V. All rights reserved.

A sensitive label–free amperometric immunosensor for alpha-fetoprotein based on gold nanorods with different aspect ratio

Science.gov (United States)

Zhou, Chunyang; Liu, Dali; Xu, Lin; Li, Qingling; Song, Jian; Xu, Sai; Xing, Ruiqing; Song, Hongwei

2015-01-01

A simple and accurate label–free amperometric immunosensor for α–fetoprotein (AFP) detection is developed based on gold nanorods (GNRs) with different aspect ratio and compared with gold particles (GNPs). The positively charged GNRs and GNPs due to the surface immobilized cetyltrimethyl ammonium bromide (CTAB) can adsorb the negatively charged AFP antibody (Ab) directly. The presence of the GNRs not only enhanced the immobilized amount of biomolecules, but also improved the electrochemical properties of the immunosensor. With the aid of GNRs, the electrochemical signal was greatly enhanced in comparison with GNPs. Under optimal conditions, the proposed immunosensor could detect AFP in a linear range from 0.1 to 200 ng/mL with a detection limit of 0.04 ng/mL (signal–to–noise ratio = 3), and it also possessed good reproducibility and storage stability. Moreover, the detection of AFP in five human serum samples also showed satisfactory accuracy. The proposed methodology was potentially attractive for clinical immunoassay. PMID:25909588

Validated high-performance anion-exchange chromatography with pulsed amperometric detection method for the determination of residual keratan sulfate and other glucosamine impurities in sodium chondroitin sulfate.

Science.gov (United States)

Bottelli, Susanna; Grillo, Gianluca; Barindelli, Edoardo; Nencioni, Alessandro; Di Maria, Alessandro; Fossati, Tiziano

2017-07-07

An efficient and sensitive analytical method based on high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) was devised for the determination of glucosamine (GlcN) in sodium chondroitin sulfate (CS). Glucosamine (GlcN) is intended as marker of residual keratan sulfate (KS) and other impurities generating glucosamine by acidic hydrolyzation. The latter brings CS and KS to their respective monomers. Since GlcN is present only in KS we developed a method that separates GlcN from GalN, the principal hydrolytic product of CS, and then we validated it in order to quantify GlcN. Method validation was performed by spiking CS raw material with known amounts of KS. Detection limit was 0.5% of KS in CS (corresponding to 0.1μg/ml), and the linear range was 0.5-5% of KS in CS (corresponding to 0.1-1μg/ml). The optimized analysis was carried out on an ICS-5000 system (Dionex, Sunnyvale, CA, USA) equipped with a Dionex Amino Trap guard column (3mm×30mm), Dionex CarboPac-PA20 (3mm×30mm) and a Dionex CarboPac-PA20 analytical column (3mm×150mm) using gradient elution at a 0.5ml/min flow rate. Regression equations revealed good linear relationship (R 2 =0.99, n=5) within the test ranges. Quality parameters, including precision and accuracy, were fully validated and found to be satisfactory. The fully validated HPAEC-PAD method was readily applied for the quantification of residual KS in CS in several raw materials and USP/EP reference substance. Results confirmed that the HPAEC-PAD method is more specific than the electrophoretic method for related substance reported in EP and provides sensitive determination of KS in acid-hydrolyzed CS samples, enabling the quantitation of KS and other impurities (generating glucosamine) in CS. Copyright © 2017 Elsevier B.V. All rights reserved.

Desenvolvimento de um sistema de análise por injeção em fluxo utilizando materiais alternativos de baixo custo para fins didáticos

Directory of Open Access Journals (Sweden)

Bruna C. S. Moreira

2014-01-01

Full Text Available This work describes a simple and inexpensive flow injection analysis system in which gravity force provides fluid propulsion while needles for insulin administration or metallic wires act as electrodes for amperometric detection. The proposed system was able to demonstrate the influence of several operational parameters on the transient signals. Moreover, this system was successfully used to evaluate both the stoichiometry of Cu2+-EDTA complex and the effect of pH on the kinetics of the reaction between ferricyanide and ascorbic acid. Therefore, the proposed system can be regarded as an efficient and accessible didactic tool for the teaching of FIA principles.

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.

Spectrofluorimetric determination of cerium by flow injection analysis

International Nuclear Information System (INIS)

Liu Shaorong; Meng Jian; Liu Wenhua

1990-01-01

A spectrofluorimetric method for the determination of cerium (λ ex/em:251/365 nm) in hydrochloric acid solution by flow injection analysis is presented. It has well developed the normal spectrofluorimetric method for determination of cerium and has made: 1, the determination procedure shortened; 2, the determination speed increased to about 180 samples per hour; 3, the determination range widened to 0.05-100.0 ppm CeO 2 , abouot two times as wide as the normal spectrofluorimetric method; and 4, the relative standard deviation lessened (about 0.47% for 0.1 ppm CeO 2 , n = 13)

On-line dynamic fractionation and automatic determination of inorganic phosphorous in environmental solid substrates exploiting sequential injection microcolumn extraction and flow injection analysi

DEFF Research Database (Denmark)

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

2006-01-01

Sequential injection microcolumn extraction (SI-MCE) based on the implementation of a soil containing microcartridge as external reactor in a sequential injection network is, for the first time, proposed for dynamic fractionation of macronutrients in environmental solids, as exemplified by the pa......Sequential injection microcolumn extraction (SI-MCE) based on the implementation of a soil containing microcartridge as external reactor in a sequential injection network is, for the first time, proposed for dynamic fractionation of macronutrients in environmental solids, as exemplified...... by the partitioning of inorganic phosphorous in agricultural soils. The on-line fractionation method capitalises on the accurate metering and sequential exposure of the various extractants to the solid sample by application of programmable flow as precisely coordinated by a syringe pump. Three different soil phase...... associations for phosphorus, that is, exchangeable, Al- and Fe-bound and Ca-bound fractions, were elucidated by accommodation in the flow manifold of the 3 steps of the Hietjles-Litjkema (HL) scheme involving the use of 1.0 M NH4Cl, 0.1 M NaOH and 0.5 M HCl, respectively, as sequential leaching reagents...

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......, can be monitored directly and in real-time by an enzyme-modified electrode based on cellobiose dehydrogenase (CDH) from Phanerochaete chrysosporium (Pc). PcCDH was cross-linked and immobilized on the surface of a carbon paste electrode which contained a mediator, benzoquinone. An oxidation current...... of the reduced mediator, hydroquinone, produced by the CDH-catalyzed reaction with cellobiose, was recorded under constant-potential amperometry at +0.5 V (vs. Ag/AgCl). The CDH-biosensors showed high sensitivity (87.7 µA mM−1 cm−2), low detection limit (25 nM), and fast response time (t95% ∼ 3 s...

MHD flow over a permeable stretching/shrinking sheet of a nanofluid with suction/injection

Directory of Open Access Journals (Sweden)

Sandeep Naramgari

2016-06-01

Full Text Available In this study we analyzed the influence of thermal radiation and chemical reaction on two dimensional steady magnetohydrodynamic flow of a nanofluid past a permeable stretching/shrinking sheet in the presence of suction/injection. We considered nanofluid volume fraction on the boundary is submissive controlled, which makes the present study entirely different from earlier studies and physically more realistic. The equations governing the flow are solved numerically. Effects of non-dimensional governing parameters on velocity, temperature and concentration profiles are discussed and presented through graphs. Also, coefficient of skin friction and local Nusselt number is investigated for stretching/shrinking and suction/injection cases separately and presented through tables. Comparisons with existed results are presented. Present results have an excellent agreement with the existed studies under some special assumptions. Results indicate that the enhancement in Brownian motion and thermophoresis parameters depreciates the nanoparticle concentration and increases the mass transfer rate. Dual solutions exist only for certain range of stretching/shrinking and suction/injection parameters.

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

Polymer based amperometric hydrogen sensor

International Nuclear Information System (INIS)

Ramesh, C.; Periaswami, G.; Mathews, C.K.; Shankar, P.

1993-01-01

A polymer based amperometric hydrogen sensor has been developed for measuring hydrogen in argon. Polyvinyl alcohol-phosphoric acid serves as the solid electrolyte for proton conduction. The electrolyte is sandwiched between two palladium films. Short circuit current between the film at room temperature is measured and is found to be linearly dependant on hydrogen concentration in argon to which one side of the film is exposed. The other side is exposed to air. The response time of the sensor is found to be improved on application of a D.C. potential of 200 mV in series. The sensitivity of the sensor is in ppm range. This may be sufficient for monitoring cover gas hydrogen in FBTR. Work is underway to improve the long-term stability of the sensor. (author)

Bulletin of the Chemical Society of Ethiopia - Vol 7, No 2 (1993)

African Journals Online (AJOL)

Effect of Na2S04 and Fe2(S04)3 on the oxidation behaviour of aisi-303alloy at 900 · EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT ... Flow injection spectrophotometric and amperometric determinations of ammonia with glutamate dehydrogenase reactor · EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT

Assessment of leak detection capability of Candu 6 annulus gas system using moisture injection tests

International Nuclear Information System (INIS)

Nho, Ki Man; Kim, Wang Bae

1998-01-01

The Candu 6 reactor assembly consists of an array of 380 pressure tubes, which are installed horizontally in a large cylindrical vessel, the Calandria, containing the low pressure heavy water moderator. The pressure tube is located inside calandria tube and the annulus between these tubes, which forms a closed loop with CO 2 gas recirculating, is called the Annulus Gas System (AGS). It is designed to give an alarm to the operator even for a small pressure tube leak by a very sensitive dew point meter so that he can take a preventive action for the pressure tbe rupture incident. To judge whether the operator action time is enough or not in the design of Wolsung 2, 3, and 4, the Leak Before Break (LBB) assessment is required for the analysis of the pressure tube failure accident. In order to provide the required data for the LBB assessment of Wolsung Units 2, 3, 4, a series of leak detection capability tests was performed by injecting controlled rates of heavy water vapour. The data of increased dew point and rates of rise were measured to determine the alarm set point for dew point rate of rise of Wolsung Unit 2. It was found that the response of the dew point depends on the moisture injection rate, CO 2 gas flow rate and the leak location. The test showed that Candu 6 AGS can detect the very small leaks less than few g/hr and dew point rate of rise alarm can be the most reliable alarm signal to warn the operator. Considering the present results, the first response time of dew point to the AGS CO 2 flow rate is approximated. (author)

Flow visualization and simulation of the filling process during injection molding

DEFF Research Database (Denmark)

Guerrier, Patrick; Tosello, Guido; Hattel, Jesper Henri

2017-01-01

To directly compare experimental moldings from an injection molding machine with simulations, a special mold has been produced with a glass window. The injection plane is perpendicular to the opening and closing planes, in order for the 55. mm thick glass window to be easily visible from the side....... These two had significant effects on the filling times and injection pressure calculated by the simulations. Other effects investigated included transient thermal management of the mold, pressure dependent viscosity and wall slip, but their effect were not remarkably large in this work. The obtained....... A high speed camera recording 500 frames per second was employed, and the mold had three thermocouples and two pressure sensors installed. The molded part is a 2. mm thick plate with a 0.5. mm thin section, which creates a characteristic V-shaped flow pattern. Two different materials were employed...

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

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.

Double electrochemical covalent coupling method based on click chemistry and diazonium chemistry for the fabrication of sensitive amperometric immunosensor.

Science.gov (United States)

Qi, Honglan; Li, Min; Zhang, Rui; Dong, Manman; Ling, Chen

2013-08-20

A double electrochemical covalent coupling method based on click chemistry and diazonium chemistry for the fabrication of sensitive amperometric immunosensor was developed. As a proof-of-concept, a designed alkyne functionalized human IgG was used as a capture antibody and a HRP-labeled rabbit anti-goat IgG was used as signal antibody for the determination of the anti-human IgG using the sandwich model. The immunosensor was fabricated by electrochemically grafting a phenylazide on the surface of a glassy carbon electrode, and then, by coupling the alkyne functionalized human IgG with the phenylazide group through an electro-click chemistry in the presence of Cu(II). The amperometric measurement for the determination of the anti-human IgG was performed after the fabricated immunosensor was incubated with the target anti-human IgG and then with the HRP-labeled anti-goat IgG at -0.25V in 0.10M PBS (pH 7.0) containing 0.1mM hydroquinone and 2.0mM H2O2. The results showed that the increased current was linear with the logarithm of the concentration of the anti-human IgG in the range from 1.0×10(-10)g mL(-1) to 1.0×10(-8)g mL(-1) with a detection limit of 3×10(-11)g mL(-1). Furthermore, the feasibility of the double electrochemical covalent coupling method proposed in this work for fabricating the amperometric immunosensor array was explored. This work demonstrates that the double electrochemical covalent coupling method is a promising approach for the fabrication of the immunosensor and immunosensor array. Copyright © 2013 Elsevier B.V. All rights reserved.

Three-dimensional simulation of flow and combustion for pulverised coal injection

Energy Technology Data Exchange (ETDEWEB)

Guo, B.Y.; Zulli, P.; Rogers, H.; Mathieson, J.G.; Yu, A.B. [BlueScope Steel Research, Port Kembla, NSW (Australia)

2005-07-01

A three-dimensional numerical model of pulverised coal injection has been developed for simulating coal flow and combustion in the tuyere and raceway of a blast furnace. The model has been used to simulate previously reported combustion tests, which feature an inclined co-axial lance with an annular cooling gas. The predicted coal burnout agrees well with that measured for three coals with volatile contents and particle size ranging between 20.2-36.4% and particle sizes 1-200 {mu}m. Many important phenomena including flow asymmetry, recirculating flow and particle dispersion in the combustion chamber have been predicted. The current model can reproduce the experimental observations including the effects on burnout of coal flowrate and the introduction of methane for lance cooling.

Determination of ammonium ion using a reagentless amperometric biosensor based on immobilized alanine dehydrogenase.

Science.gov (United States)

Tan, Ling Ling; Musa, Ahmad; Lee, Yook Heng

2011-01-01

The use of the enzyme alanine dehydrogenase (AlaDH) for the determination of ammonium ion (NH(4)(+)) usually requires the addition of pyruvate substrate and reduced nicotinamide adenine dinucleotide (NADH) simultaneously to effect the reaction. This addition of reagents is inconvenient when an enzyme biosensor based on AlaDH is used. To resolve the problem, a novel reagentless amperometric biosensor using a stacked methacrylic membrane system coated onto a screen-printed carbon paste electrode (SPE) for NH(4)(+) ion determination is described. A mixture of pyruvate and NADH was immobilized in low molecular weight poly(2-hydroxyethyl methacrylate) (pHEMA) membrane, which was then deposited over a photocured pHEMA membrane (photoHEMA) containing alanine dehydrogenase (AlaDH) enzyme. Due to the enzymatic reaction of AlaDH and the pyruvate substrate, NH(4)(+) was consumed in the process and thus the signal from the electrocatalytic oxidation of NADH at an applied potential of +0.55 V was proportional to the NH(4)(+) ion concentration under optimal conditions. The stacked methacrylate membranes responded rapidly and linearly to changes in NH(4)(+) ion concentrations between 10-100 mM, with a detection limit of 0.18 mM NH(4)(+) ion. The reproducibility of the amperometrical NH(4)(+) biosensor yielded low relative standard deviations between 1.4-4.9%. The stacked membrane biosensor has been successfully applied to the determination of NH(4)(+) ion in spiked river water samples without pretreatment. A good correlation was found between the analytical results for NH(4)(+) obtained from the biosensor and the Nessler spectrophotometric method.

Optimization of Large Volume Injection for Improved Detection of Polycyclic Aromatic Hydrocarbons (PAH) in Mussels

DEFF Research Database (Denmark)

Duedahl-Olesen, Lene; Ghorbani, Faranak

2008-01-01

Detection of PAH of six benzene rings is somewhat troublesome and lowering the limits of detection (LODs) for these compounds in food is necessary. For this purpose, we optimized a Programmable-Temperature-Vaporisation (PTV) injection with Large Volume Injection (LVI) with regard to the GC-MS det...

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.

Numerical simulation of effects of a non-ionized fluid injection and suction on the MHD flow in a circular channel

International Nuclear Information System (INIS)

Rahimi Eosboee, M.; Pourmahmoud, N.; Mirzaie, I.; Mohajeri Khameneh, P.; Majidyfar, S.

2012-01-01

Control of a fluid flow velocity profile by injection and suction of a non-ionized fluid in presence of a uniform steady magnetic field has important technical applications. In this paper, the unsteady incompressible and viscous conducting fluid flow has been investigated in a circular channel. The channel walls are assumed to be non-conducting and porous. They are subjected to a uniform steady magnetic field which is perpendicular to the axis of channel, then and suction and injection are applied at the walls. The well known equations of Magnetohydrodynamics are governed to the motion of an electrically conducting fluid flow that is subjected to magnetic field. The numerical solution is carried out by finite difference approach. The results of present numerical simulation shown that the flow injection and suction through the wall can be controlled effectively, the main flow in channel especially in industrial purposes. The results are obtained for different values of the injected and sucked non-ionized flow rate and the effect of Hartman number on the velocity profile is investigated. Finally, a good agreement is seen between the presented results and the corresponding data of finite element method.

Amperometric Enzyme-based Gas Sensor for Formaldehyde: Impact of Possible Interferences

Directory of Open Access Journals (Sweden)

Ralf Moos

2007-02-01

Full Text Available In this work, cross-sensitivities and environmental influences on the sensitivityand the functionality of an enzyme-based amperometric sensor system for the directdetection of formaldehyde from the gas phase are studied. The sensor shows a linearresponse curve for formaldehyde in the tested range (0 - 15 vppm with a sensitivity of1.9 μA/ppm and a detection limit of about 130 ppb. Cross-sensitivities by environmentalgases like CO2, CO, NO, H2, and vapors of organic solvents like methanol and ethanol areevaluated as well as temperature and humidity influences on the sensor system. The sensorshowed neither significant signal to CO, H2, methanol or ethanol nor to variations in thehumidity of the test gas. As expected, temperature variations had the biggest influence onthe sensor sensitivity with variations in the sensor signal of up to 10 % of the signal for 5vppm CH2O in the range of 25 - 30 °C.

Ultrasound extracted flavonoids from four varieties of Portuguese red grape skins determined by reverse-phase high-performance liquid chromatography with electrochemical detection.

Science.gov (United States)

Novak, Ivana; Janeiro, Patricia; Seruga, Marijan; Oliveira-Brett, Ana Maria

2008-12-23

Several flavonoids present in red grape skins from four varieties of Portuguese grapes were determined by reverse-phase high-performance liquid chromatography (RP-HPLC) with electrochemical detection (ECD). Extraction of flavonoids from red grape skins was performed by ultrasonication, and hydrochloric acid in methanol was used as extraction solvent. The developed RP-HPLC method used combined isocratic and gradient elution with amperometric detection with a glassy carbon-working electrode. Good peak resolution was obtained following direct injection of a sample of red grape extract in a pH 2.20 mobile phase. Eleven different flavonoids: cyanidin-3-O-glucoside (kuromanin), delphinidin-3-O-glucoside (myrtillin), petunidin-3-O-glucoside, peonidin-3-O-glucoside, malvidin-3-O-glucoside (oenin), (+)-catechin, rutin, fisetin, myricetin, morin and quercetin, can be separated in a single run by direct injection of sample solution. The limit of detection obtained for these compounds by ECD was 20-90 pg/L, 1000 times lower when compared with photodiode array (PDA) limit of detection of 12-55 ng/L. RP-HPLC-ECD was characterized by an excellent sensitivity and selectivity, and appropriate for the simultaneous determination of these electroactive phenolic compounds present in red grape skins.

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.

Theoretical Study on the Flow of Refilling Stage in a Safety Injection Tank

Energy Technology Data Exchange (ETDEWEB)

Park, Jun Sang [Halla Univ. Daejeon (Korea, Republic of)

2017-10-15

In this study, a theoretical analysis was performed to the flow of refilling stage in a safety injection tank, which is the core cooling system of nuclear power plant in an emergency. A theoretical model was proposed with a nonlinear governing equation defining on the flow of the refilling process of the coolant. Utilizing the Taylor-series expansion, the 1st - order approximation flow equation was obtained, along with its analytic solution of closed type, which could predict accurately the variations of free surface height and flow rate of the coolant. The availability of theoretical result was confirmed by comparing with previous experimental results.

Propulsor pneumático versátil e isento de pulsação para sistemas de análise em fluxo

Directory of Open Access Journals (Sweden)

Matos Renato C.

2001-01-01

Full Text Available Aquarium air pumps are proposed and evaluated as pneumatic liquid propulsion devices for flow injection and continuos flow analysis (FIA and CFA systems. This kind of pump is widely available at a very low cost and it can sustain a pressure around of 4 psi (0.28 bar indefinitely. By applying this air pressure onto a solution contained in a reservoir flask, it is possible to reach flow rates of up to 12.5 mL min-1 for circuits comprising reactors, made from 0.8 i.d. tubing with a length of 100 cm. The precise adjustment of flow rate below the maximum one can be made with a simplified needle valve or inserting in series a short length of capillary tube. The absence of flow pulsation is a definite advantage in comparison with peristaltic pumps, especially when amperometric detection is elected, as confirmed experimentally in FIA and CF applications.

Wavelet transform for the evaluation of peak intensities in flow-injection analysis

NARCIS (Netherlands)

Bos, M.; Hoogendam, E.

1992-01-01

The application of the wavelet transform in the determination of peak intensities in flow-injection analysis was studied with regard to its properties of minimizing the effects of noise and baseline drift. The results indicate that for white noise and a favourable peak shape a signal-to-noise ratio

Wavelett transform for the evaluation of peak intensities in flow-injection analysis

NARCIS (Netherlands)

Bos, M.; Hoogendam, E.; Hoogendam, E.

1992-01-01

The application of the wavelet transform in the determination of peak intensities in flow-injection analysis was studied with regard to its properties of minimizing the effects of noise and baseline drift. The results indicate that for white noise and a favourable peak shape a signal-to-noise ratio

Simultaneous determination of amino acids and carbohydrates in culture media of Clostridium thermocellum by valve-switching ion chromatography.

Science.gov (United States)

Fa, Yun; Yang, Haiyan; Ji, Chengshuai; Cui, He; Zhu, Xinshu; Du, Juan; Gao, Jun

2013-10-10

An improved method for the simultaneous determination of 20 amino acids and 7 carbohydrates using one-valve switching after injection, ion chromatography, and integrated pulsed amperometric detection is proposed. The resolution of the amino acids and carbohydrates in the cation trap column was investigated. In addition, parameters including flow liquid type, flow rate, concentration, and valve-switch timing were optimized. The method is time-saving, effective, and accurate for the simultaneous separation of amino acids and carbohydrates, with a mean correlation coefficient of >0.99 and repeatability of 0.5-4.6% for eight replicates. The method was successfully applied in the analysis of amino acids and carbohydrates in aseptic media and in extracellular culture media of three phenotypes of Clostridium thermocellum. Copyright © 2013 Elsevier B.V. All rights reserved.

[Amperometric biosensor for lactate analysis in wines and grape must during fermentation].

Science.gov (United States)

Shkotova, L V; Horiushkina, T B; Slast'ia, E A; Soldatkin, O P; Tranh-Minh, S; Chovelon, J M; Dziadevych, S V

2005-01-01

The amperometric biosensor based on lactate oxidase for determination of lactate has been developed, and two methods of immobilization of lactate oxidase on the surface of industrial screen-printed platinum electrodes SensLab were compared. A sensor with immobilized in the Resydrol polymer lactate oxidase by the method of physical adsorption is characterized of narrow dynamic range and greater response value in comparison with a biosensor based on immobilised in poly(3,4-ethylenedioxythiophene) lactate oxidase by the method of electrochemical polymerization. Operational stability of the biosensor developed was studied and it was shown, that the immobilization method does not influence their stability. The analysis of the lactate in wine and during wine fermentation has been conducted. High correlation of the data obtained by means of amperometric lactate biosensor and a standard method of an ionic chromatography has been shown. The developed biosensor could be applied in the food industry for the control and optimization of the wine fermentation process, and quality control of wine.

Simple system for isothermal DNA amplification coupled to lateral flow detection.

Directory of Open Access Journals (Sweden)

Kristina Roskos

Full Text Available Infectious disease diagnosis in point-of-care settings can be greatly improved through integrated, automated nucleic acid testing devices. We have developed an early prototype for a low-cost system which executes isothermal DNA amplification coupled to nucleic acid lateral flow (NALF detection in a mesofluidic cartridge attached to a portable instrument. Fluid handling inside the cartridge is facilitated through one-way passive valves, flexible pouches, and electrolysis-driven pumps, which promotes a compact and inexpensive instrument design. The closed-system disposable prevents workspace amplicon contamination. The cartridge design is based on standard scalable manufacturing techniques such as injection molding. Nucleic acid amplification occurs in a two-layer pouch that enables efficient heat transfer. We have demonstrated as proof of principle the amplification and detection of Mycobacterium tuberculosis (M.tb genomic DNA in the cartridge, using either Loop Mediated Amplification (LAMP or the Exponential Amplification Reaction (EXPAR, both coupled to NALF detection. We envision that a refined version of this cartridge, including upstream sample preparation coupled to amplification and detection, will enable fully-automated sample-in to answer-out infectious disease diagnosis in primary care settings of low-resource countries with high disease burden.

Detecting Distributed SQL Injection Attacks in a Eucalyptus Cloud Environment

Science.gov (United States)

Kebert, Alan; Barnejee, Bikramjit; Solano, Juan; Solano, Wanda

2013-01-01

The cloud computing environment offers malicious users the ability to spawn multiple instances of cloud nodes that are similar to virtual machines, except that they can have separate external IP addresses. In this paper we demonstrate how this ability can be exploited by an attacker to distribute his/her attack, in particular SQL injection attacks, in such a way that an intrusion detection system (IDS) could fail to identify this attack. To demonstrate this, we set up a small private cloud, established a vulnerable website in one instance, and placed an IDS within the cloud to monitor the network traffic. We found that an attacker could quite easily defeat the IDS by periodically altering its IP address. To detect such an attacker, we propose to use multi-agent plan recognition, where the multiple source IPs are considered as different agents who are mounting a collaborative attack. We show that such a formulation of this problem yields a more sophisticated approach to detecting SQL injection attacks within a cloud computing environment.

Amperometric Determination of Glucose at Parts per Million Levels with Immobilized Glucose Oxidase.

Science.gov (United States)

Sittampalam, G.; Wilson, G. S.

1982-01-01

An experiment on the operation and utility of an amperometric immobilized enzyme electrode (or probe) is described, including advantages of the experiment, equipment, reagents, preparation of phosphate buffer, enzyme immobilization techniques, laboratory procedures, precautions, and discussion of experimental results. (SK)

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.

An amperometric enzyme electrode and its biofuel cell based on a glucose oxidase-poly(3-anilineboronic acid)-Pd nanoparticles bionanocomposite for glucose biosensing.

Science.gov (United States)

Sun, Lingen; Ma, Yixuan; Zhang, Pei; Chao, Long; Huang, Ting; Xie, Qingji; Chen, Chao; Yao, Shouzhuo

2015-06-01

A new amperometric enzyme electrode and its biofuel cell were fabricated based on a glucose oxidase (GOx)-poly(3-anilineboronic acid) (PABA)-Pd nanoparticles (PdNPs) bionanocomposite for biosensing of glucose. Briefly, Pd was electroplated on a multiwalled carbon nanotubes (MWCNTs)-modified Au electrode, and the GOx-PABA-PdNPs bionanocomposite was prepared on the Pd(plate)/MWCNTs/Au electrode through the chemical oxidation of a GOx-3-anilineboronic acid adduct by Na2PdCl4, followed by electrode-modification with an outer-layer chitosan (CS) film. The thus-prepared CS/GOx-PABA-PdNPs/Pd(plate)/MWCNTs/Au electrode exhibited a linear amperometric response to glucose concentration from 2.0 μM to 4.5 mM with a sensitivity of 160 μA/mM/cm(2), sub-μM detection limit, and excellent operation/storage stability in the first-generation biosensing mode, as well as excellent analytical performance in the second-generation biosensing mode. The good recoveries of glucose obtained from spiked urine samples revealed the application potential of our amperometric enzyme electrode. In addition, a glucose/O2 biofuel cell was constructed using this enzyme electrode as the anode and a Pt/MWCNTs/Au electrode as the cathode, and this biofuel cell as a self-powered biosensing device showed a linear voltage response to glucose concentration from 100 μM to 13.5 mM with a sensitivity of 43.5 mV/mM/cm(2) and excellent operation/storage stability. Copyright © 2015 Elsevier B.V. All rights reserved.

Detection of recombinant EPO in blood and urine samples with EPO WGA MAIIA, IEF and SAR-PAGE after microdose injections.

Science.gov (United States)

Dehnes, Yvette; Shalina, Alexandra; Myrvold, Linda

2013-01-01

The misuse of microdoses of performance enhancing drugs like erythropoietin (EPO) constitutes a major challenge in doping analysis. When injected intravenously, the half-life of recombinant human EPO (rhEPO) like epoetin alfa, beta, and zeta is only a few hours and hence, the window for direct detection of rhEPO in urine is small. In order to investigate the detection window for rhEPO directly in blood and urine with a combined affinity chromatography and lateral flow immunoassay (EPO WGA MAIIA), we recruited nine healthy people who each received six intravenously injected microdoses (7.5 IU/kg) of NeoRecormon (epoetin beta) over a period of three weeks. Blood and urine samples were collected in the days following the injections and analyzed with EPO WGA MAIIA as well as the current validated methods for rhEPO; isoelectric focusing (IEF) and sarcosyl polyacrylamide gel electrophoresis (SAR-PAGE). For samples collected 18 h after a microdose, the sensitivity of the EPO WGA MAIIA assay was 100% in plasma and 87.5% in urine samples at the respective 98% specificity threshold levels. In comparison, the sensitivity in plasma and urine was 75% and 100%, respectively, with IEF, and 87.5% in plasma and 100% in urine when analyzed with SAR-PAGE. We conclude that EPO WGA MAIIA is a sensitive assay for the detection of rhEPO, with the potential of being a fast, supplemental screening assay for use in doping analysis.

Determinação potenciométrica em fluxo de cloreto de cetilpiridinio em desinfectantes bucais Potentiometric determination of cetylpyridinium chloride in oral desinfectants by flow injection analysis

Directory of Open Access Journals (Sweden)

Paula C. S. Baptista

2003-08-01

Full Text Available The work describes a new procedure for cetylpyridinium chloride determination in oral disinfectants, based on a flow-injection system with potentiometric detection. The determination was based on the measurement of picrate concentration decrease as result of ion-pair reaction with the analyte present in the injected sample. In the optimised set-up the sample injection volume was kept at 400 µL and merged downstream with the reagent solution containing 1,0 x10-5 mol/L of picrate adjusted to pH 5.0 with citrate/citric acid buffer. The flow rate was fixed at 8 mL/min and the reactor length at 40 cm. The proposed procedure enables the determination of cetylpyridinium in the analytical range of 5,0x10-6 - 7,5x10-5 mol/L at a sampling rate of 60/h. The results for real samples had a precision better than 3% and were comparable to the labelled values.

Direct Zinc Determination in Brazilian Sugar Cane Spirit by Solid-Phase Extraction Using Moringa oleifera Husks in a Flow System with Detection by FAAS

OpenAIRE

Alves, Vanessa N.; Borges, Simone S. O.; Coelho, Nivia M. M.

2011-01-01

This paper reports a method for the determination of zinc in Brazilian sugar cane spirit, (cachaça in Portuguese), using solid-phase extraction with a flow injection analysis system and detection by FAAS. The sorbent material used was activated carbon obtained from Moringa oleifera husks. Flow and chemical variables of the proposed system were optimized through multivariate designs. The factors selected were sorbent mass, sample pH, sample flow rate, and eluent concentration. The optimum extr...

Numerical simulation of the gas-solid flow in a square circulating fluidized bed with secondary air injection

Energy Technology Data Exchange (ETDEWEB)

Wang, Zhengyang [Harbin Institute of Technology, Harbin (China). Post-doctor Station of Civil Engineering; Harbin Institute of Technology, Harbin (China). Combustion Engineering Research Inst.; Sun, Shaozeng; Zhao, Ningbo; Wu, Shaohua [Harbin Institute of Technology, Harbin (China). Combustion Engineering Research Inst.; Tan, Yufei [Harbin Institute of Technology, Harbin (China). School of Municipal and Environmental Engineering

2013-07-01

The dynamic behavior of gas-solid flow in an experimental square circulating fluidized bed setup (0.25 m x 0.25 m x 6.07 m) is predicted with numerical simulation based on the theory of Euler-Euler gas-solid two-phase flow and the kinetic theory of granular flows. The simulation includes the operation cases with secondary injection and without air-staging. The pressure drop profile, local solids concentration and particle velocity was compared with experimental results. Both simulation and experimental results show that solids concentration increases significantly below the secondary air injection ports when air-staging is adopted. Furthermore, the flow asymmetry in the solid entrance region of the bed was investigated based on the particle concentration/velocity profile. The simulation results are in agreement with the experimental results qualitatively.

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

Energy Technology Data Exchange (ETDEWEB)

Peng, Guilong [Key Laboratory of Eco-Environment of Three Gorges Region of Ministry of Education, Chongqing University, Chongqing, 400045 (China); Department of Chemistry, Beijing Key Laboratory of Microanalytical Methods and Instrumentation, Tsinghua University, Beijing, 100084 (China); He, Qiang, E-mail: heqiang0980@163.com [Key Laboratory of Eco-Environment of Three Gorges Region of Ministry of Education, Chongqing University, Chongqing, 400045 (China); Lu, Ying [Department of Mathematics and Physics, Armed Police College, Chengdu, 610213 (China); Huang, Jing [Research Center for Advanced Computation, College of Science, Xihua University, Chengdu, 610039 (China); Lin, Jin-Ming, E-mail: jmlin@mail.tsinghua.edu.cn [Department of Chemistry, Beijing Key Laboratory of Microanalytical Methods and Instrumentation, Tsinghua University, Beijing, 100084 (China)

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%. - Graphical abstract: Flow injection microfluidic device with on-line fluorescent derivatization and detection coupled to LIF. - Highlights: • A highly selective and sensitive derivatizing reagent for Cr(III) was synthesized and characterized. • The magnetic-MWCNTs nanocomposite as a SPE sorbent was successfully synthesized and characterized. • A new portable detection system was developed for microfluidic chip FIA platform.

Glassy carbon electrodes modified with hemin-carbon nanomaterial films for amperometric H2O2 and NO2− detection

International Nuclear Information System (INIS)

Valentini, Federica; Cristofanelli, Lara; Carbone, Marilena; Palleschi, Giuseppe

2012-01-01

In this work a new chemical sensor for the H 2 O 2 and nitrite amperometric detection was assembled, using a glassy carbon (GC) bare electrode modified by two different nanocomposite materials. The nanocomposite films were prepared by casting a functionalised carbon nanofiber (CNF-COOH) and single-walled carbon nanotubes (SWCNT-OH, for comparison) on the glassy carbon electrode surface; then an iron(III) protoporphyrin IX (Fe(III)P) was adsorbed on these modified surfaces. A morphological investigation of the nanocomposite layers was also carried out, using the Scanning Electron Microscopy (SEM). The electrochemical characterization, performed optimising several electro-analytical parameters (such as different medium, pH, temperature, scan rate, and potential window), demonstrated that the direct electrochemistry of the Fe(III)P/Fe(II)P redox couple involves 1e − /1H + process. A kinetic evaluation of the electron-transfer reaction mechanism was also carried out, demonstrating that the heterogeneous electron transfer rate constant resulted higher at CNF/hemin/GC biosensor than that evaluated at SWCNT/hemin/GC modified electrode. Finally, the electrocatalytic activity toward the H 2 O 2 reduction was also demonstrated for both sensors but better results were observed working at CNF/hemin/GC modified electrode, especially in terms of an extended linearity (ranging from 50 to 1000 μM), a lower detection limit (L.O.D. = 3σ) of 2.0 × 10 −6 M, a higher sensitivity of 2.2 × 10 −3 A M −1 cm −2 , a fast response time (9 s), a good reproducibility (RSD% −3 to 2.5 × 10 −1 M), a lower detection limit (L.O.D. = 3σ) of 3.18 × 10 −4 M, a higher sensitivity of 1.2 × 10 −2 A M −1 cm −2 , a fast response time of 10 s, a good reproducibility (RSD% <1, n = 3) and finally a good operational stability.

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.

Development of capillary electrophoresis methods for quantitative determination of taurine in vehicle system and biological media.

Science.gov (United States)

da Silva, Dayse L P; Rüttinger, Hans H; Mrestani, Yahia; Baum, Walter F; Neubert, Reinhard H H

2006-06-01

CE methods have been developed for the determination of taurine in pharmaceutical formulation (microemulsion) and in biological media such as sweat. The CE system with end-column pulsed amperometric detection has been found to be an interesting method in comparison with UV and fluorescence detection for its simplicity and rapidity. A gold-disk electrode of 100 mm diameter was used as the working electrode. The effects of a field decoupler at the end of the capillary, separation voltage, injection and pressure times were investigated. A detection limit of 4 x 10(-5) mol/L was reached using integrated pulsed amperometric detection, a method successfully applied to taurine analysis of the biological samples such as sweat. For taurine analysis of oil-in-water microemulsion, fluorescence detector was the favored method, the detection limit of which was 4 x 10(-11) mol/L.

Numerical simulation of flow characteristics of lean jet to cross-flow in safety injection of reactor cooling system

International Nuclear Information System (INIS)

Wang Haijun; He Huining; Luo Yushan; Wang Weishu

2011-01-01

In the present work, a numerical simulation was performed to study the flow characteristics of lean jet to cross flow in a main tube in the safety injection of reactor cooling system. The influence scope and mixing characteristics of the confined lean jet in cross-flow were studied. It can be concluded that three basic flow regimes are marked, namely the attached lean jet, lift-off lean jet and impinging lean jet. The velocity ratio V R is the key factor in the flow state. The depth and region of jet to main flow are enhanced with the increase of the velocity ratio. The jet flow penetrates through the main flow with the increase of the velocity ratio. At higher velocity ratio, the jet flow strikes the main flow bottom and circumfluence happens in upriver of main flow. The vortex flow characteristics dominate the flow near region of jet to cross-flow and the mixture of jet to cross-flow. At different velocity ratio V R , the vortex grows from the same displacement, but the vortex type and the vortex is different. At higher velocity ratio, the vortex develops fleetly, wears off sharp and dies out sharp. The study is very important to the heat transfer experiments of cross-flow jet and thermal stress analysis in the designs of nuclear engineering. (authors)

A study on nozzle flow and spray characteristics of piezo injector for next generation high response injection

International Nuclear Information System (INIS)

Lee, Jin Wook; Min, Kyoung Doug

2006-01-01

Most diesel injector, which is currently used in high-pressure common rail fuel injection system of diesel engine, is driven by the solenoid coil energy for its needle movement. The main disadvantage of this solenoid-driven injector is a high power consumption, high power loss through solenoid coil and relatively fixed needle response's problem. In this study, a prototype piezo-driven injector, as a new injector mechanism driven by piezoelectric energy based on the concept of inverse piezo-electric effect, has been designed and fabricated to know the effect of piezo-driven injection processes on the diesel spray structure and internal nozzle flow. Firstly we investigated the spray characteristics in a constant volume chamber pressurized by nitrogen gas using the back diffusion light illumination method for high-speed temporal photography and also analyzed the inside nozzle flow by a fully transient simulation with cavitation model using VOF(Volume Of Fraction) method. The numerical calculation has been performed to simulate the cavitating flow of 3-dimensional real size single hole nozzle along the injection duration. Results were compared between a conventional solenoid-driven injector and piezo-driven injector, both equipped with the same micro-sac multi-hole injection nozzle. The experimental results show that the piezo-driven injector has short injection delay and a faster spray development and produces higher injection velocity than the solenoid-driven injector. And the predicted simulation results with the degree of cavitation's generation inside nozzle for faster needle response in a piezo-driven injector were reflected to spray development in agreement with the experimental spray images

Integrated hydraulic and organophosphate pesticide injection simulations for enhancing event detection in water distribution systems.

Science.gov (United States)

Schwartz, Rafi; Lahav, Ori; Ostfeld, Avi

2014-10-15

As a complementary step towards solving the general event detection problem of water distribution systems, injection of the organophosphate pesticides, chlorpyrifos (CP) and parathion (PA), were simulated at various locations within example networks and hydraulic parameters were calculated over 24-h duration. The uniqueness of this study is that the chemical reactions and byproducts of the contaminants' oxidation were also simulated, as well as other indicative water quality parameters such as alkalinity, acidity, pH and the total concentration of free chlorine species. The information on the change in water quality parameters induced by the contaminant injection may facilitate on-line detection of an actual event involving this specific substance and pave the way to development of a generic methodology for detecting events involving introduction of pesticides into water distribution systems. Simulation of the contaminant injection was performed at several nodes within two different networks. For each injection, concentrations of the relevant contaminants' mother and daughter species, free chlorine species and water quality parameters, were simulated at nodes downstream of the injection location. The results indicate that injection of these substances can be detected at certain conditions by a very rapid drop in Cl2, functioning as the indicative parameter, as well as a drop in alkalinity concentration and a small decrease in pH, both functioning as supporting parameters, whose usage may reduce false positive alarms. Copyright © 2014 Elsevier Ltd. All rights reserved.

Magnetohydrodynamics effect on three-dimensional viscous incompressible flow between two horizontal parallel porous plates and heat transfer with periodic injection/suction

Directory of Open Access Journals (Sweden)

R. C. Chaudhary

2004-11-01

Full Text Available We investigate the hydromagnetic effect on viscous incompressible flow between two horizontal parallel porous flat plates with transverse sinusoidal injection of the fluid at the stationary plate and its corresponding removal by periodic suction through the plate in uniform motion. The flow becomes three dimensional due to this injection/suction velocity. Approximate solutions are obtained for the flow field, the pressure, the skin-friction, the temperature field, and the rate of heat transfer. The dependence of solution on M (Hartmann number and λ (injection/suction is investigated by the graphs and tables.

Leak detection device for control rod drive and detection method therefor

International Nuclear Information System (INIS)

Imasaki, Yoshio.

1997-01-01

The present invention provides a detection device for leak of cooling water from a sealed axial portion of control rod drives (CRD) disposed in a BWR type reactor and a monitoring method therefor. Namely, the CRD transfers rotation at the sealed axial portion and elevates/lowers a piston to insert/withdraw control rod into/from the reactor core. High pressure water is injected upon occurrence of scram to urge the piston upwardly thereby rapidly inserting the control rods. Leak detection pipelines are laid from the sealed axial portion. A flow glass is connected to the leak detection pipelines. Then, cooling water leaked from the sealed axial portion flows in the leak detection pipelines and flows into the flow glass. The flow rate of cooling water leaked from the sealed axial portion of the CRD can thus be detected by monitoring the flow glass. In addition, a flowmeter is connected to the leak detection pipelines, or the flowmeter and the flow glass are connected, and a flowmeter is connected downstream. Then, the flow rate of the leaked cooling water can be detected automatically. (I.S.)

Pencil graphite leads as simple amperometric sensors for microchip electrophoresis.

Science.gov (United States)

Natiele Tiago da Silva, Eiva; Marques Petroni, Jacqueline; Gabriel Lucca, Bruno; Souza Ferreira, Valdir

2017-11-01

In this work we demonstrate, for the first time, the use of inexpensive commercial pencil graphite leads as simple amperometric sensors for microchip electrophoresis. A PDMS support containing one channel was fabricated through soft lithography and sanded pencil graphite leads were inserted into this channel to be used as working electrodes. The electrochemical and morphological characterization of the sensor was carried out. The graphite electrode was coupled to PDMS microchips in end-channel configuration and electrophoretic experiments were performed using nitrite and ascorbate as probe analytes. The analytes were successfully separated and detected in well-defined peaks with satisfactory resolution using the microfluidic platform proposed. The repeatability of the pencil graphite electrode was satisfactory (RSD values of 1.6% for nitrite and 12.3% for ascorbate, regarding the peak currents) and its lifetime was estimated to be ca. 700 electrophoretic runs over a cost of ca. $ 0.05 per electrode. The limits of detection achieved with this system were 2.8 μM for nitrite and 5.7 μM for ascorbate. For proof of principle, the pencil graphite electrode was employed for the real analysis of well water samples and nitrite was successfully quantified at levels below its maximum contaminant level established in Brazil and US. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Flow injection on-line dilution for zinc determination in human saliva with electrothermal atomic absorption spectrometry detection

Energy Technology Data Exchange (ETDEWEB)

Burguera-Pascu, Margarita [Department of Oral Medicine, School of Dentistry, University of Granada, Granada (Spain)], E-mail: margaburpas@hotmail.com; Rodriguez-Archilla, Alberto [Department of Oral Medicine, School of Dentistry, University of Granada, Granada (Spain); Burguera, Jose Luis; Burguera, Marcela; Rondon, Carlos; Carrero, Pablo [Department of Chemistry, Faculty of Sciences, University of Los Andes, Merida (Venezuela)

2007-09-26

An automated method is described for the determination of zinc in human saliva by electrothermal atomic absorption spectrometry (ET AAS) after on-line dilution of samples with a significant reduction of sample consumption per analysis (<0.4 mL including the dead volume of the system). In order to fulfill this aim without changing the sample transport conduits during the experiments, a flow injection (FI) dilution system was constructed. Its principal parts are: one propulsion device (peristaltic pump, PP) for either samples, standards or washing solution all located in an autosampler tray and for the surfactant solution (Triton X-100) used as diluent, and a two-position time based solenoid injector (TBSI{sub 1}) which allowed the introduction of 10 {mu}L of either solution in the diluent stream. To avoid unnecessary waste of samples, the TBSI{sub 1} also permitted the recirculation of the solutions to their respective autosampler cups. The downstream diluted solution fills a home made sampling arm assembly. The sequential deposition of 20 {mu}L aliquots of samples or standards on the graphite tube platform was carried out by air displacement with a similar time based solenoid injector (TBSI{sub 2}). The dilution procedure and the injection of solutions into the atomizer are computer controlled and synchronized with the operation of the temperature program. Samples or standards solutions were submitted to two drying steps (at 90 and 130 deg. C), followed by pyrolysis and atomization at 700 and 1700 deg. C, respectively. The aqueous calibration was linear up to 120.0 {mu}g L{sup -1} for diluted standard solutions/samples and its slope was similar (p > 0.05) to the standard addition curve, indicating lack of matrix effect. The precision tested by repeated analysis of real saliva samples was less than 3% and the detection limit (3{sigma}) was of 0.35 {mu}g L{sup -1}. To test the accuracy of the proposed procedure, recovery tests were performed, obtaining mean recovery

Exact solution for flow in a porous pipe with unsteady wall suction and/or injection

Science.gov (United States)

Tsangaris, S.; Kondaxakis, D.; Vlachakis, N. W.

2007-10-01

This paper presents an extension of the exact solution of the steady laminar axisymmetric flow in a straight pipe of circular cross section with porous wall, given by R.M. Terrill, to the case of unsteady wall injection and/or suction. The cases of the pulsating parabolic profile and of the developed pulsating flow are investigated as examples. The pulsating flow in porous ducts has many applications in biomedical engineering and in other engineering areas.

Determination of glutamine and glutamic acid in mammalian cell cultures using tetrathiafulvalene modified enzyme electrodes.

Science.gov (United States)

Mulchandani, A; Bassi, A S

1996-01-01

Tetrathiafulvalene (TTF) mediated amperometric enzyme electrodes have been developed for the monitoring of L-glutamine and L-glutamic acid in growing mammalian cell cultures. The detection of glutamine was accomplished by a coupled enzyme system comprised of glutaminase plus glutamate oxidase, while the detection of glutamic acid was carried out by a single enzyme, glutamate oxidase. The appropriate enzyme(s) were immoblized on the Triton-X treated surface of tetrathiafulvalene modified carbon paste electrodes by adsorption, in conjunction with entrapment by an electrochemically deposited copolymer film of 1,3-phenylenediamine and resorcinol. Operating conditions for the glutamine enzyme electrode were optimized with respect to the amount of enzymes immoblized, pH, temperature and mobile phase flow rate for operation in a flow injection (FIA) system. When applied to glutamine and glutamic acid measurements in mammalian cell culture in FIA, the results obtained with enzyme electrodes were in excellent agreement with those determined by enzymatic analysis.

Stopped-flow injection method for determination of phosphate in soils and fertilisers

Directory of Open Access Journals (Sweden)

Jaroon Jakmunee

2008-02-01

Full Text Available A stopped-flow injection system for the determination of phosphate has been developed. It involves the phosphate-molybdate-ascorbic acid reactions in the molybdenum blue method. The system is controlled by a semi-automatic stopped-FI analyser with a light emitting diode (LED-colorimeter for monitoring the absorbance change relating to the concentration of a reaction product formed during the stopping period while the injected zone of a standard or sample is being in the flow cell. The slope of the FIAgram obtained is linearly proportional to the reaction rate, which depends on the phosphate concentration. Effects of concentration of reagents, viz. sodium molybdate, ascorbic acid and nitric acid, on the slope of the FIAgram were studied. The suitable concentration is 0.02 M, 0.25 %w/v and 0.15 M, respectively. A linear calibration graph in the range of 0.3-6.0 mg P L-1 was employed for the determination of phosphate in soil and fertiliser samples. The results obtained agree well with those from a standard spectrophotometric method.

Kepler Planet Detection Metrics: Pixel-Level Transit Injection Tests of Pipeline Detection Efficiency for Data Release 25

Science.gov (United States)

Christiansen, Jessie L.

2017-01-01

This document describes the results of the fourth pixel-level transit injection experiment, which was designed to measure the detection efficiency of both the Kepler pipeline (Jenkins 2002, 2010; Jenkins et al. 2017) and the Robovetter (Coughlin 2017). Previous transit injection experiments are described in Christiansen et al. (2013, 2015a,b, 2016).In order to calculate planet occurrence rates using a given Kepler planet catalogue, produced with a given version of the Kepler pipeline, we need to know the detection efficiency of that pipeline. This can be empirically determined by injecting a suite of simulated transit signals into the Kepler data, processing the data through the pipeline, and examining the distribution of successfully recovered transits. This document describes the results for the pixel-level transit injection experiment performed to accompany the final Q1-Q17 Data Release 25 (DR25) catalogue (Thompson et al. 2017)of the Kepler Objects of Interest. The catalogue was generated using the SOC pipeline version 9.3 and the DR25 Robovetter acting on the uniformly processed Q1-Q17 DR25 light curves (Thompson et al. 2016a) and assuming the Q1-Q17 DR25 Kepler stellar properties (Mathur et al. 2017).

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.

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

International Nuclear Information System (INIS)

Cespon-Romero, R.M.; Yebra-Biurrun, M.C.

2007-01-01

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 μg g -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

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

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.

Construção de eletrodo de grafite retirado de pilha comum: aplicações didáticas

Directory of Open Access Journals (Sweden)

José Augusto Fragale Baio

2014-07-01

Full Text Available This paper presents a proposal for using recycled graphite electrodes obtained from exhausted commercial 1.5 V batteries and its application in electroanalysis. The electrode could be prepared by the students and applied in the simple didactic experiments suggested, such as determination of active electrode area, cyclic voltammetry and useful potential range (also called "potential window", demonstration and effect of scan rate on cyclic voltammograms. The possibility of using the graphite electrode in quantitative analysis was also demonstrated using the ferricyanide/ferrocyanide reversible redox couple ([Fe(CN6]3-/[Fe(CN6]4- as an electrochemical probe by the dependence of peak current with the analyte concentration and flow injection analysis with amperometric detection.

Numerical Simulation of Magnetic Nanoparticles Injection into Two–phase Flow in a Porous Medium

KAUST Repository

El-Amin, Mohamed; Saad, Ahmed M.; Sun, Shuyu; Salama, Amgad

2017-01-01

In this paper, the problem of magnetic nanoparticles injection into a water–oil two–phase flow under an external permanent magnetic field is investigated. The mathematical model of the problem under consideration has been developed. We treat

Integrated electrochemical gluconic acid biosensor based on self-assembled monolayer-modified gold electrodes. Application to the analysis of gluconic acid in musts and wines.

Science.gov (United States)

Campuzano, S; Gamella, M; Serra, B; Reviejo, A J; Pingarrón, J M

2007-03-21

An integrated amperometric gluconic acid biosensor constructed using a gold electrode (AuE) modified with a self-assembled monolayer (SAM) of 3-mercaptopropionic acid (MPA) on which gluconate dehydrogenase (GADH, 0.84 U) and the mediator tetrathiafulvalene (TTF, 1.5 micromol) were coimmobilized by covering the electrode surface with a dialysis membrane is reported. The working conditions selected were Eapp=+0.15 V and 25+/-1 degrees C. The useful lifetime of one single TTF-GADH-MPA-AuE was surprisingly long. After 53 days of continuous use, the biosensor exhibited 86% of the original sensitivity. A linear calibration plot was obtained for gluconic acid over the 6.0x10(-7) to 2.0x10(-5) M concentration range, with a limit of detection of 1.9x10(-7) M. The effect of potential interferents (glucose, fructose, galactose, arabinose, and tartaric, citric, malic, ascorbic, gallic, and caffeic acids) on the biosensor response was evaluated. The behavior of the biosensor in a flow-injection system in connection with amperometric detection was tested. The analytical usefulness of the biosensor was evaluated by determining gluconic acid in wine and must samples, and the results obtained were validated by comparison with those provided by using a commercial enzyme test kit.

A study on nozzle flow and spray characteristics of piezo injector for next generation high response injection

Energy Technology Data Exchange (ETDEWEB)

Lee, Jin Wook [Korea Institue of Machinery and Materials, Daejeon (Korea, Republic of); Min, Kyoung Doug [Seoul National University, Seoul (Korea, Republic of)

2006-06-15

Most diesel injector, which is currently used in high-pressure common rail fuel injection system of diesel engine, is driven by the solenoid coil energy for its needle movement. The main disadvantage of this solenoid-driven injector is a high power consumption, high power loss through solenoid coil and relatively fixed needle response's problem. In this study, a prototype piezo-driven injector, as a new injector mechanism driven by piezoelectric energy based on the concept of inverse piezo-electric effect, has been designed and fabricated to know the effect of piezo-driven injection processes on the diesel spray structure and internal nozzle flow. Firstly we investigated the spray characteristics in a constant volume chamber pressurized by nitrogen gas using the back diffusion light illumination method for high-speed temporal photography and also analyzed the inside nozzle flow by a fully transient simulation with cavitation model using VOF(Volume Of Fraction) method. The numerical calculation has been performed to simulate the cavitating flow of 3-dimensional real size single hole nozzle along the injection duration. Results were compared between a conventional solenoid-driven injector and piezo-driven injector, both equipped with the same micro-sac multi-hole injection nozzle. The experimental results show that the piezo-driven injector has short injection delay and a faster spray development and produces higher injection velocity than the solenoid-driven injector. And the predicted simulation results with the degree of cavitation's generation inside nozzle for faster needle response in a piezo-driven injector were reflected to spray development in agreement with the experimental spray images.

Capillary electrophoresis microchip coupled with on-line chemiluminescence detection

International Nuclear Information System (INIS)

Su Rongguo; Lin Jinming; Qu Feng; Chen Zhifeng; Gao Yunhua; Yamada, Masaaki

2004-01-01

In the present work, chemiluminescence detection was integrated with capillary electrophoresis microchip. The microchip was designed on the principle of flow-injection chemiluminescence system and capillary electrophoresis. It has three main channels, five reservoirs and a detection cell. As model samples, dopamine and catechol were separated and detected using a permanganate chemiluminescent system on the prepared microchip. The samples were electrokinetically injected into the double-T cross section, separated in the separation channel, and then oxidized by chemiluminescent reagent delivered by a home-made micropump to produce light in the detection cell. The electroosmotic flow could be smoothly coupled with the micropump flow. The detection limits for dopamine and catechol were 20.0 and 10.0 μM, respectively. Successful separation and detection of dopamine and catechol demonstrated the distinct advantages of integration of chemiluminescent detection on a microchip for rapid and sensitive analysis

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).

Abnormal traffic flow data detection based on wavelet analysis

Directory of Open Access Journals (Sweden)

Xiao Qian

2016-01-01

Full Text Available In view of the traffic flow data of non-stationary, the abnormal data detection is difficult.proposed basing on the wavelet analysis and least squares method of abnormal traffic flow data detection in this paper.First using wavelet analysis to make the traffic flow data of high frequency and low frequency component and separation, and then, combined with least square method to find abnormal points in the reconstructed signal data.Wavelet analysis and least square method, the simulation results show that using wavelet analysis of abnormal traffic flow data detection, effectively reduce the detection results of misjudgment rate and false negative rate.

Start-up assist by magnetized plasma flow injection in TPE-RX reversed-field pinch

Energy Technology Data Exchange (ETDEWEB)

Asai, T. [College of Science and Technology, Nihon University, 1-8 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8308 (Japan)]. E-mail: asai@phys.cst.nihon-u.ac.jp; Nagata, M. [Graduate School of Engineering, University of Hyogo, Himeji (Japan); Koguchi, H. [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba (Japan); Hirano, Y. [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba (Japan); Sakakita, H. [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba (Japan); Yambe, K. [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba (Japan); Kiyama, S. [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba (Japan)

2006-11-15

A reversed-field pinch (RFP) start-up assisted by a magnetized plasma flow injection was demonstrated for the first time on a TPE-RX machine. This sequence of experiments aimed to establish a new method of ionization, gas-fill and helicity injection in the start-up phase of an RFP. In this start-up method, magnetized and well-ionized plasma is formed by a magnetized coaxial plasma gun and injected into the torus chamber as an initial pre-ionized plasma for RFP formation. In the initial experiments, attenuated density pump-out and comparatively slow decay of the toroidal flux and plasma current were observed as evidence of its being an effective start-up method.

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.

Carbon nanotubes and graphene modified screen-printed carbon electrodes as sensitive sensors for the determination of phytochelatins in plants using liquid chromatography with amperometric detection.

Science.gov (United States)

Dago, Àngela; Navarro, Javier; Ariño, Cristina; Díaz-Cruz, José Manuel; Esteban, Miquel

2015-08-28

Nanomaterials are of great interest for the development of electrochemical sensors. Multi-walled carbon nanotubes and graphene were used to modify the working electrode surface of different screen-printed carbon electrodes (SPCE) with the aim of improving the sensitivity of the SPCE and comparing it with the conventional glassy carbon electrode. To assay the usability of these sensors, a HPLC methodology with amperometric detection was developed to analyze several phytochelatins in plants of Hordeum vulgare and Glycine max treated with Hg(II) or Cd(II) giving detection limits in the low μmolL(-1) range. Phytochelatins are low molecular weight peptides with the general structure γ-(Glu-Cys)n-Gly (n=2-5) which are synthesized in plants in the presence of heavy metal ions. These compounds can chelate heavy metal ions by the formation of complexes which, are transported to the vacuoles, where the toxicity is not threatening. For this reason phytochelatins are essential in the detoxification of heavy metal ions in plants. The developed HPLC method uses a mobile phase of 1% of formic acid in water with KNO3 or NaCl (pH=2.00) and 1% of formic acid in acetonitrile. Electrochemical detection at different carbon-based electrodes was used. Among the sensors tested, the conventional glassy carbon electrode offers the best sensitivity although modification improves the sensitivity of the SPCE. Glutathione and several isoforms of phytochelatin two were found in plant extracts of both studied species. Copyright © 2015 Elsevier B.V. All rights reserved.

The Optimisation of Processing Condition for Injected Mould Polypropylene-Nanoclay-Gigantochloa Scortechinii based on Melt Flow Index

Science.gov (United States)

Othman, M. H.; Rosli, M. S.; Hasan, S.; Amin, A. M.; Hashim, M. Y.; Marwah, O. M. F.; Amin, S. Y. M.

2018-03-01

The fundamental knowledge of flow behaviour is essential in producing various plastic parts injection moulding process. Moreover, the adaptation of advanced polymer-nanocomposites such as polypropylene-nanoclay with natural fibres, for instance Gigantochloa Scortechinii may boost up the mechanical properties of the parts. Therefore, this project was proposed with the objective to optimise the processing condition of injected mould polypropylene-nanoclay-Gigantochloa Scortechini fibres based on the flow behaviour, which was melt flow index. At first, Gigantochloa Scortechinii fibres have to be preheated at temperature 120°C and then mixed with polypropylene, maleic anhydride modified polypropylene oligomers (PPgMA) and nanoclay by using Brabender Plastograph machine. Next, forms of pellets were produced from the samples by using Granulator machine for use in the injection moulding process. The design of experiments that was used in the injection moulding process was Taguchi Method Orthogonal Array -L934. Melt Flow Index (MF) was selected as the response. Based on the results, the value of MFI increased when the fiber content increase from 0% to 3%, which was 17.78 g/10min to 22.07 g/10min and decreased from 3% to 6%, which was 22.07 g/10min to 20.05 g/10min and 3%, which gives the highest value of MFI. Based on the signal to ratio analysis, the most influential parameter that affects the value of MFI was the melt temperature. The optimum parameter for 3% were 170°C melt temperature, 35% packing pressure, 30% screw speed and 3 second filling time.

Detection of pyrrolizidine alkaloids using flow analysis with both acidic potassium permanganate and tris(2,2'-bipyridyl)ruthenium(II) chemiluminescence

International Nuclear Information System (INIS)

Gorman, Bree A.; Barnett, Neil W.; Bos, Richard

2005-01-01

For the first time, analytically useful chemiluminescence was elicited from the reactions of the pyrrolizidine alkaloids. Heliotrine, retronecine, supinine, monocrotaline and echinatine N-oxide yielded chemiluminescence upon reaction with tris(2,2'-bipyridyl)ruthenium(II) whilst lasiocarpine, its N-oxide and supinine elicited light upon reaction with acidic potassium permanganate. Detection limits for heliotrine were 1.25 x 10 -7 M and 9 x 10 -9 M for tris(2,2'-bipyridyl)ruthenium(III) perchlorate with flow injection analysis (FIA) and the silica-immobilised reagent (4-[4-(dichloromethylsilanyl)-butyl]-4'-methyl-2,2'-bipyridine)bis (2,2'-bipyridyl)ruthenium(II) with sequential injection analysis (SIA), respectively. Lasiocarpine was detectable at 1.4 x 10 -7 M using acidic potassium permanganate with FIA. Additionally, the silica-immobilised reagent was optimised with respect to the oxidant (ammonium ceric nitrate) concentration and the aspiration times which afforded a detection limit for codeine of 5 x 10 -10 M using SIA

The use of the cardiopulmonary flow index to detect cardiac defects in man and animal

International Nuclear Information System (INIS)

Cilliers, G.D.

1982-01-01

The efficiency of the cardiopulmonary flow index (CPFI) to detect cardiac defects and to evaluate therapy in man and animal is tested. The CPFI seems to be sensitive enough to evaluate vasodilator and inotropic therapy during cardiac failure with 'gousiekte' sheep. Pulmonary emboli in sheep is induced by injecting coagulated blood into the pulmonary circulation. These pulmonary emboli caused a decrease in the CPFI. CPFI recordings were made on patients, before and after aorta- and mitralvalve replacements. The CPFI is sensitive enough to detect the valve inefficiency and also to detect the improvement in the pump efficiency of the heart after the double valve replacement. The results obtained prove that the CPFI could have a proper place in modern cardiology to evaluate therapy (clinical and surgical) and also to distinguish between cardiac defects and pulmonary emboli

Assessment of effect of intravitreal ranibizumab injection on the ocular blood flow in patients with neovascular age-related macular degeneration

Directory of Open Access Journals (Sweden)

V. V. Neroev

2014-07-01

Full Text Available Purpose: To evaluate the effect of intravitreal ranibizumab injection on the ocular blood flow in patients with neovascular agerelatedmacular degeneration (AMD.Methods: 35 patients with wet AMD undergone intravitreal 0.5 mg ranibizumab injection. Color Doppler Imaging (CDI and dopplerographywere used to measure hemodynamic parameters including the peak systolic velocity (Vsyst, cm / s, end-diastolic velocity (V diast, cm / s, and resistance index (RI of blood flow in the central retinal artery (CRA, the short posterior ciliary arteries (PCA, and the ophthalmic artery (OA. All patients were examined before and after injection on day 1‑7 and 30 day during the 3‑month follow up period.Results: Before intravitreal injection Vsyst was decreased in short PCA (p<0.05, RI in CRA and in short PCA significantly increased in comparison with normal index in same vessels. The peak systolic velocity in OA, in CRA and in short PCA was not significantly changed. After second injection resistance index in CRA and in short PCA was normalized.Conclusion: There was not impairment of ocular blood flow in retinal and choroidal after monthly intravitreal injection of ranibizumab during the 3‑month follow up period.

Assessment of effect of intravitreal ranibizumab injection on the ocular blood flow in patients with neovascular age-related macular degeneration

Directory of Open Access Journals (Sweden)

V. V. Neroev

2013-01-01

Full Text Available Purpose: To evaluate the effect of intravitreal ranibizumab injection on the ocular blood flow in patients with neovascular agerelatedmacular degeneration (AMD.Methods: 35 patients with wet AMD undergone intravitreal 0.5 mg ranibizumab injection. Color Doppler Imaging (CDI and dopplerographywere used to measure hemodynamic parameters including the peak systolic velocity (Vsyst, cm / s, end-diastolic velocity (V diast, cm / s, and resistance index (RI of blood flow in the central retinal artery (CRA, the short posterior ciliary arteries (PCA, and the ophthalmic artery (OA. All patients were examined before and after injection on day 1‑7 and 30 day during the 3‑month follow up period.Results: Before intravitreal injection Vsyst was decreased in short PCA (p<0.05, RI in CRA and in short PCA significantly increased in comparison with normal index in same vessels. The peak systolic velocity in OA, in CRA and in short PCA was not significantly changed. After second injection resistance index in CRA and in short PCA was normalized.Conclusion: There was not impairment of ocular blood flow in retinal and choroidal after monthly intravitreal injection of ranibizumab during the 3‑month follow up period.

Modelling and Simulation of Structural Deformation of Isothermal Subsurface Flow and Carbon Dioxide Injection

KAUST Repository

El-Amin, Mohamed; Negara, Ardiansyah; Salama, Amgad; Sun, Shuyu

2011-01-01

force term. The flux continuity condition is used at interfaces between different permeability layers of the heterogeneous medium. We analyze the vertical migration of a CO2 plume injected into a 2D layered reservoir. Analysis of distribution of flow

The determination, by flow-injection analysis, of iron, sulphate, silver and cadmium

International Nuclear Information System (INIS)

Jones, E.A.

1983-01-01

This report describes the spectrophotometric determination by flow-injection analysis including, where necessary, liquid-liquid extraction of iron with 1,10-phenanthroline; of sulphate by its catalytic effect on the methylthymol blue-zirconium reaction; of silver with bromopyrogallol red and 1,10-phenanthroline; and of cadmium with dithizone. Optimum conditions for each system are established, and sensitivities and ranges of determination are given

Modelling and Simulation of Structural Deformation of Isothermal Subsurface Flow and Carbon Dioxide Injection

KAUST Repository

El-Amin, Mohamed

2011-05-15

Injection of CO2 in hydrocarbon reservoir has double benefit. On the one hand, it is a profitable method due to issues related to global warming, and on the other hand it is an effective mechanism to enhance hydrocarbon recovery. Such injection associates complex processes involving, e.g., solute transport of dissolved materials, in addition to local changes in density of the phases. Also, increasing carbon dioxide injection may cause a structural deformation of the medium, so it is important to include such effect into the model. The structural deformation modelling in carbon sequestration is important to evaluate the medium stability to avoid CO2 leakage to the atmosphere. On the other hand, geologic formation of the medium is usually heterogeneous and consists of several layers of different permeability. In this work we conduct numerical simulation of two-phase flow in a heterogeneous porous medium domain with dissolved solute transport as well as structural deformation effects. The solute transport of the dissolved component is described by concentration equation. The structural deformation for geomechanics is derived from a general local differential balance equation with neglecting the local mass balance of solid phase and the inertial force term. The flux continuity condition is used at interfaces between different permeability layers of the heterogeneous medium. We analyze the vertical migration of a CO2 plume injected into a 2D layered reservoir. Analysis of distribution of flow field components such as saturation, pressures, velocities, and CO2 concentration are presented.

An investigation of flow properties of metal matrix composites suspensions for injection molding

International Nuclear Information System (INIS)

Ahmad, F.; Bevis, M.J.

1997-01-01

Flow properties of metal matrix composites suspensions have significant effects on the fibre orientation during mould filling. The results presented in this paper relate to the flow properties of aluminium powder and glass fibres compounded into a sacrificial thermoplastics binder. For this purpose, a range of aluminium compounds and aluminium composite suspensions were investigated over a wide shear rate range expected to occur during injection mould process. Aluminium composites wee prepared by substituting glass fibres for aluminium in aluminium compound. Aluminium composite containing a maximum critical volume fraction of fibres which did not exhibit an increase n viscosity was determined. The effect of temperature on the flow behaviour of aluminium composite was also investigated. (author)

Three-dimensional analysis of internal flow characteristics in the injection nozzle tip of direct-injection diesel engines; Sanjigen suchi kaiseki ni yoru DI diesel kikan no nenryo funsha nozzle nai ryudo tokusei no kaimei

Energy Technology Data Exchange (ETDEWEB)

Ogawa, H; Matsui, Y; Kimura, S [Nissan Motor Co. Ltd. Tokyo (Japan)

1997-10-01

To reduce the exhaust emissions and fuel consumption of direct-injection diesel engines, it is essential to optimize the fuel injection equipment closely related to combustion and emission characteristics. In this study, three-dimensional computation has been applied to investigate the effects of the injection nozzle specifications (e.g., sac volume, round shape at the inlet of the nozzle hole) and needle tip deviation on internal flow characteristics. The computational results revealed that the effects of the nozzle specifications and needle tip deviation with a smaller needle lift on internal flow characteristics and a general approach to optimize the injection nozzle specifications were obtained. 3 refs., 10 figs., 1 tab.

The effect of intralesional steroid injections on the volume and blood flow in periocular capillary haemangiomas.

Science.gov (United States)

Verity, David H; Rose, Geoffrey E; Restori, M

2008-01-01

To examine the effect of steroid therapy on the volume estimates and blood flow characteristics of childhood periorbital capillary haemangiomas. Children at risk of amblyopia due to periorbital haemangiomas were treated with intralesional steroid injections (between 1 and 4 courses) and serial assessment of the volume and blood-flow characteristics of the lesions measured using colour Doppler ultrasonography. The characteristics of the haemangiomas in these children were compared with a cohort of untreated cases. Eight of nine treated children were female, this proportion being significantly different from the equal sex distribution of an untreated cohort (p suppression persisting for several months (between 5 and 20) before the lesion later displays the cyclic fluctuations in volume and flow seen with untreated lesions. All treated haemangiomas had some residual vascular anomaly, detectable on ultrasonography, at last follow-up--this being despite absence of clinical signs in most cases. Periorbital capillary haemangiomas requiring steroid therapy for risk of amblyopia were significantly commoner in females, were larger lesions and presented at an earlier age. Intralesional steroids appear to cause a reduction of blood flow, with a transient reduction in volume and a suppression of the natural cyclic variation seen without treatment. The changes after a course of steroid therapy appear to last for between 5 and 20 months, this period of suppression of the lesion probably being particularly useful during infancy and early childhood when the child is at greatest risk of amblyopia.

Cold water injection nozzles

International Nuclear Information System (INIS)

Kura, Masaaki; Maeda, Masamitsu; Endo, Takio.

1979-01-01

Purpose: To inject cold water in a reactor without applying heat cycles to a reactor container and to the inner wall of a feedwater nozzle by securing a perforated plate at the outlet of the cold water injection nozzle. Constitution: A disc-like cap is secured to the final end of a return nozzle of a control rod drive. The cap prevents the flow of a high temperature water flowing downward in the reactor from entering into the nozzle. The cap is perforated with a plurality of bore holes for injecting cold water into the reactor. The cap is made to about 100 mm in thickness so that the cold water passing through the bore holes is heated by the heat conduction in the cap. Accordingly, the flow of high temperature water flowing downwardly in the reactor is inhibited by the cap from backward flowing into the nozzle. Moreover, the flow of the cold water in the nozzle is controlled and rectified when passed through the bore holes in the cap and then injected into the reactor. (Yoshino, Y.)

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...

Intraperitoneal xenon for the detection of early intestinal ischemia: effect of ascites, adhesions, and misdirected injections

International Nuclear Information System (INIS)

Gharagozloo, F.; Bulkley, G.B.; LaFrance, N.; Zuidema, G.D.

1983-01-01

Significant delay in the washout of intraperitoneal xenon ( 133 Xe) in rats and dogs with decreased splanchnic blood flow (bowel strangulation, superior mesenteric artery and vein occlusion) has been previously demonstrated as the basis for radionuclide imaging to detect early (prenecrotic) intestinal ischemia. In this study, the effect of ascites, adhesions, and misdirected injections on the validity of this technique is evaluated. Xenon-133 (0.6 mCi) in 3 ml saline was injected into the peritoneal cavity of anesthetized rats and the washout of gamma activity monitored externally for 90 min. Gamma camera images were obtained at 30-min intervals. After 60 min, only 12 +/- 2% of injected activity remained in the controls. Sham option (13 +/- 1%) and simple obstruction (12 +/- 2) had been previously shown not to significantly slow washout, but segmental strangulation had done so dramatically (32 +/- 2%, P less than 0.0001). In these experiments, ascitic fluid (Ringer's lactate) in volumes of 10 ml (13 +/- 1%), 20 ml (13 +/- 1%), and 40 ml (13 +/- 1%), did not significantly slow washout in nonischemic rats. Sixty and eighty milliliters produced very tense ascites and slight but significant delay in washout (14 +/- 1%, 17 +/- 1%, respectively, P less than 0.05). Moderate (11 +/- 1%) and severe (11 +/- 1%) adhesions produced by serosal scarification did not delay washout nor affect imaging. Injections of isotope intentionally misdirected into the abdominal wall (32 +/- 2%), bowel wall (18 +/- 1%), and bowel lumen (19 +/- 2%), each significantly (P less than 0.001) slowed washout. However, such misdirected injections were easily recognizable as such on the 1-min gamma camera images and could thereby be excluded as artifactual. It is concluded that the intraperitoneal xenon technique is not invalidated by mild to moderate ascites nor by moderate to severe adhesions

Intraperitoneal xenon for the detection of early intestinal ischemia: effect of ascites, adhesions, and misdirected injections

Energy Technology Data Exchange (ETDEWEB)

Gharagozloo, F.; Bulkley, G.B.; LaFrance, N.; Zuidema, G.D.

1983-06-01

Significant delay in the washout of intraperitoneal xenon (/sup 133/Xe) in rats and dogs with decreased splanchnic blood flow (bowel strangulation, superior mesenteric artery and vein occlusion) has been previously demonstrated as the basis for radionuclide imaging to detect early (prenecrotic) intestinal ischemia. In this study, the effect of ascites, adhesions, and misdirected injections on the validity of this technique is evaluated. Xenon-133 (0.6 mCi) in 3 ml saline was injected into the peritoneal cavity of anesthetized rats and the washout of gamma activity monitored externally for 90 min. Gamma camera images were obtained at 30-min intervals. After 60 min, only 12 +/- 2% of injected activity remained in the controls. Sham option (13 +/- 1%) and simple obstruction (12 +/- 2) had been previously shown not to significantly slow washout, but segmental strangulation had done so dramatically (32 +/- 2%, P less than 0.0001). In these experiments, ascitic fluid (Ringer's lactate) in volumes of 10 ml (13 +/- 1%), 20 ml (13 +/- 1%), and 40 ml (13 +/- 1%), did not significantly slow washout in nonischemic rats. Sixty and eighty milliliters produced very tense ascites and slight but significant delay in washout (14 +/- 1%, 17 +/- 1%, respectively, P less than 0.05). Moderate (11 +/- 1%) and severe (11 +/- 1%) adhesions produced by serosal scarification did not delay washout nor affect imaging. Injections of isotope intentionally misdirected into the abdominal wall (32 +/- 2%), bowel wall (18 +/- 1%), and bowel lumen (19 +/- 2%), each significantly (P less than 0.001) slowed washout. However, such misdirected injections were easily recognizable as such on the 1-min gamma camera images and could thereby be excluded as artifactual. It is concluded that the intraperitoneal xenon technique is not invalidated by mild to moderate ascites nor by moderate to severe adhesions.

Amperometric biosensor for lactate analysis in wine and must during fermentation

OpenAIRE

Shkotova , L.V.; Goriushkina , T.B.; Tran-Minh , Canh; Chovelon , Jean-Marc; Soldatkin , A.P.; Dzyadevych , S.V.

2008-01-01

MADICA 2006 Conference, Fifth Maghreb-Europe Meeting on Materials and their Applicatons for Devices and Physical, Chemical and Biological Sensors, MADICA 2006 Conference, Fifth Maghreb-Europe Meeting on Materials and their Applicatons for Devices and Physical, Chemical and Biological Sensors; International audience; A lactate oxidase-based amperometric biosensor is designed for lactate determination. Two methods of lactate oxidase immobilization on the surface of commercial SensLab platinum p...

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.

The effect of saturation on resin flow in injection pultrusion: a preliminary numerical study

DEFF Research Database (Denmark)

Spangenberg, Jon; Larsen, Martin; R. Rodríguez, Rosa

. The implemented saturation and relative permeability curves are adopted from relationships presented in the literature. The results of the numerical model highlights the importance of accurately determining thesaturation curve when included in a numerical solver that is used to predict the resin flow in injection...

Assessing preferential flow by simultaneously injecting nanoparticle and chemical tracers

KAUST Repository

Subramanian, S. K.; Li, Yan; Cathles, L. M.

2013-01-01

The exact manner in which preferential (e.g., much faster than average) flow occurs in the subsurface through small fractures or permeable connected pathways of other kinds is important to many processes but is difficult to determine, because most chemical tracers diffuse quickly enough from small flow channels that they appear to move more uniformly through the rock than they actually do. We show how preferential flow can be assessed by injecting 2 to 5 nm carbon particles (C-Dots) and an inert KBr chemical tracer at different flow rates into a permeable core channel that is surrounded by a less permeable matrix in laboratory apparatus of three different designs. When the KBr tracer has a long enough transit through the system to diffuse into the matrix, but the C-Dot tracer does not, the C-Dot tracer arrives first and the KBr tracer later, and the separation measures the degree of preferential flow. Tracer sequestration in the matrix can be estimated with a Peclet number, and this is useful for experiment design. A model is used to determine the best fitting core and matrix dispersion parameters and refine estimates of the core and matrix porosities. Almost the same parameter values explain all experiments. The methods demonstrated in the laboratory can be applied to field tests. If nanoparticles can be designed that do not stick while flowing through the subsurface, the methods presented here could be used to determine the degree of fracture control in natural environments, and this capability would have very wide ranging value and applicability.

Photoacoustic imaging to detect rat brain activation after cocaine hydrochloride injection

Science.gov (United States)

Jo, Janggun; Yang, Xinmai

2011-03-01

Photoacoustic imaging (PAI) was employed to detect small animal brain activation after the administration of cocaine hydrochloride. Sprague Dawley rats were injected with different concentrations (2.5, 3.0, and 5.0 mg per kg body) of cocaine hydrochloride in saline solution through tail veins. The brain functional response to the injection was monitored by photoacoustic tomography (PAT) system with horizontal scanning of cerebral cortex of rat brain. Photoacoustic microscopy (PAM) was also used for coronal view images. The modified PAT system used multiple ultrasonic detectors to reduce the scanning time and maintain a good signal-to-noise ratio (SNR). The measured photoacoustic signal changes confirmed that cocaine hydrochloride injection excited high blood volume in brain. This result shows PAI can be used to monitor drug abuse-induced brain activation.

Computerized flow monitors detect small kicks

Energy Technology Data Exchange (ETDEWEB)

McCann, D.; White, D. (Sedco Forex, Paris (FR))

1992-02-24

This paper reports on a smart alarm system installed on a number of offshore rigs and one land rig which can detect kicks more quickly than conventional systems. This rapid kick detection improves rig safety because the smaller the detected influx, the easier it is to control the well. The extensive computerized monitoring system helps drilling personnel detect fluid influxes and fluid losses before the changes in flow would normally be apparent.

colour-flow ultrasound in the detection of penetrating vascular

African Journals Online (AJOL)

To determine the sensitivity of colour-flow ultrasound in the detection of penetrating vascular injuries of ... Colour-flow ultrasound is sensitive in detecting vascular injuries and is suitable as a screening .... injury, ultrasound appears to be sensitive in detecting these lesions. However there is a risk of missing more central.

[Properties of modified amperometric biosensors based on methanol dehydrogenase and Methylobacterium nodulans cells].

Science.gov (United States)

Kuznetsova, T A; Beschastnyĭ, A P; Alferov, S V; Trotsenko, Iu A

2013-01-01

The properties of amperometric biosensors based on methanol dehydrogenase (MDH), Methylobacterium nodulans cells, and the ferrocene-modified carbon paste electrode were investigated. It was shown that the addition ofhydroxyapatite (HA) to a carbon paste increased the sensitivity and operating stability of MDH biosensors. The linear range of the electrode was 0.0135-0.5 and 0.032-1.5 mM for methanol and formaldehyde, respectively. The detection limit of methanol and formaldehyde was 4.5 and 11.0 microM, respectively. The loss of activity of the electrode within 10 days of storage in the presence of 2.0 mM KCN did not exceed 12%. Cyanide (10 mM) completely inhibited the sensor responses to formaldehyde (1.0 mM), which allowed for the selective determination of methanol in the presence of formaldehyde. The biosensor based on cells exhibited lower stability and sensitivity toward methanol and formaldehyde; the sensitivity coefficients were 980 and 21 nA/mM, respectively.

Determination of pH by flow-injection analysis and by fiber-optrode analysis

International Nuclear Information System (INIS)

Pia, S.H.; Waltman, D.P.; Hillman, D.C.

1988-07-01

Two new procedures for measuring pH were developed. The first measures pH colorimetrically using a proprietary indicator-dye mixture in a flow injection analysis (FIA) procedure. The second measures pH using a fiber-optic chemical sensor (FOCS) specifically developed for pH determinations. The FOCS method measures pH by monitoring the fluorescence of a fluorescein derivative bonded to the distal end of a fiber-optic cable called an optrade. The FIA method currently has a precision and accuracy of about + or - 0.2 pH units and can measure 100 samples/hour. The FOCS method has a precision of + or - 0.05-0.20 pH units and an accuracy of + or - 0.1 to 0.6 pH units. About 10 to 60 samples can be analyzed. The characteristics of the FOCS Method will vary significantly with individual optrodes. The experimental results indicate that either flow-injection analysis or fiber optic chemical sensor analysis could form the basis for an alternative to electrometric measurement of pH in certain circumstances

Detection of pyrrolizidine alkaloids using flow analysis with both acidic potassium permanganate and tris(2,2'-bipyridyl)ruthenium(II) chemiluminescence

Energy Technology Data Exchange (ETDEWEB)

Gorman, Bree A. [School of Biological and Chemical Sciences, Deakin University, Geelong, Vic. 3217 (Australia); Barnett, Neil W. [School of Biological and Chemical Sciences, Deakin University, Geelong, Vic. 3217 (Australia)]. E-mail: barnie@deakin.edu.au; Bos, Richard [School of Biological and Chemical Sciences, Deakin University, Geelong, Vic. 3217 (Australia)

2005-06-13

For the first time, analytically useful chemiluminescence was elicited from the reactions of the pyrrolizidine alkaloids. Heliotrine, retronecine, supinine, monocrotaline and echinatine N-oxide yielded chemiluminescence upon reaction with tris(2,2'-bipyridyl)ruthenium(II) whilst lasiocarpine, its N-oxide and supinine elicited light upon reaction with acidic potassium permanganate. Detection limits for heliotrine were 1.25 x 10{sup -7} M and 9 x 10{sup -9} M for tris(2,2'-bipyridyl)ruthenium(III) perchlorate with flow injection analysis (FIA) and the silica-immobilised reagent (4-[4-(dichloromethylsilanyl)-butyl]-4'-methyl-2,2'-bipyridine)bis (2,2'-bipyridyl)ruthenium(II) with sequential injection analysis (SIA), respectively. Lasiocarpine was detectable at 1.4 x 10{sup -7} M using acidic potassium permanganate with FIA. Additionally, the silica-immobilised reagent was optimised with respect to the oxidant (ammonium ceric nitrate) concentration and the aspiration times which afforded a detection limit for codeine of 5 x 10{sup -10} M using SIA.

Amperometric xanthine biosensors using glassy carbon electrodes modified with electrografted porous silica nanomaterials loaded with xanthine oxidase

International Nuclear Information System (INIS)

Saadaoui, Maroua; Sánchez, Alfredo; Díez, Paula; Raouafi, Noureddine; Pingarrón, José M.; Villalonga, Reynaldo

2016-01-01

Glassy carbon electrodes were modified with silica materials such as silica nanoparticles, mesoporous silica nanoparticles and mesoporous silica thin films with the aim to introduce scaffolds suitable for the immobilization of enzymes. Xanthine oxidase was selected as a model enzyme, and xanthine as the target analyte. A comparison of the modified electrodes showed the biosensor prepared with mesoporous silica nanoparticles to perform best. By using the respective biosensor, xanthine can be amperometrically determined (via measurement of enzymatically formed hydrogen peroxide) at a working voltage of 0.7 V (vs. Ag/AgCl) with a 0.28 μM detection limit. The biosensor was evaluated in terms of potential interferences, reproducibility and stability, and applied to the determination of fish freshness via sensing of xanthine. (author)

Carbohydrate and alditol analysis by high-performance anion-exchange chromatography coupled with electrochemical detection at a cobalt-modified electrode.

Science.gov (United States)

Casella, Innocenzo G; Contursi, Michela

2003-07-01

A cobalt oxyhydroxide film dispersed on a carbon electrode surface was characterized and proposed as an amperometric sensor for determination of alditols and carbohydrates in flowing streams. Complex mixtures of carbohydrates were separated by anion-exchange chromatography using a moderately alkaline solution as mobile phase. The cobalt modified electrode (GC-Co) was employed under a constant applied potential of 0.5 V (vs Ag/AgCl). Under these experimental conditions the detection limits (S/N=3) for all analyzed electroactive molecules ranged between 0.3 micromol L(-1) and 1.5 micromol L(-1) and the dynamic linear ranges spanned generally three orders of magnitude above the relevant detection limits. Analytical determinations of carbohydrates and alditols in red and white wines, are reported.

Quantitative assessment of hepatic and splenic blood flow detected by Tc-99m-Sn colloid liver scintigraphy

International Nuclear Information System (INIS)

Narabayashi, Isamu; Nishiyama, Shoji; Sugimura, Kazuro

1983-01-01