bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of the polarographic behavior of biliverdin in the presence of hydrogen peroxide
Authors: Zeng Baizhao , Zhou Xingyao 
Published: May 2005

AbstractIn hydrogen peroxide‐EDTA‐sodium phosphate solution (pH 11.0), biliverdin (BV) shows a very sensitive cathodic polarographic wave at about −0.82 V (vs. Saturated Calomel Electrode, SCE). By using derivative single‐sweep polarography, the wave height varies linearly with BV concentration over a range of 6 × 10−8 M to 2 × 10−6 M, so it can be used for the determination of BV. Various electrochemical techniques have been used to investigate the characterìstics of the wave and the electrode reaction mechanism. As a result, the polarographic wave is identified to be an adsorptive‐catalytic wave, and the electrode mechanism is considered to be a catalytic reaction coupled to an irreversible charge transfer process. In the electrochemical process, BV acts as catalyst and hydrogen peroxide as oxidizer. In this article, the rate constant of the catalytic reaction is also determined.
Electrocatalytic flow detection of amino acids at ruthenium dioxide‐modified carbon electrodes
Authors: Wang Joseph , Lin Yuebe 
Published: May 2005

AbstractFixed‐potential anodic detection of ammo acids and peptides can be carried out at ruthenium dioxide (RuO2) ‐modified carbon paste and graphite epoxy electrodes. The effect of various experimental variables on the electrocatlytic response is explored. Optimal detection is obtained under strongly alkaline conditions and a low ( + 0.45 v vs. Ag/AgCl) operating potential. With flow injection, the response is fast, linear, and reproducible )relative standard deviations of 1.5 to 1.7%, n = 32). Similar advantages are reported for the incorporation of cobalt oxide (CO3O4) into carbon paste detectors.
Amperometric detection of purine nucleotides utilizing immobilized enzyme reactors and on‐line amplification by substrate recycling
Authors: Yao Toshio , Tsureyama Kiminori 
Published: May 2005

AbstractFlow‐injection systems with an immobilized enzyme reactor are proposed for the amperometric detection of purine nucleotides. One system studied is based on the combined use of an alkaline phosphatase (AlP) immobilized reactor and a purine nucleoside phosphorylase (PNP)‐xanthine oxidase (XO) coimmobilized reactor, which responds to purine nucleotides With high selectivity. Another system with a coimmobilized AlP‐PNP‐XO reactor gives responses amplified by substrate recycling. When carrier solution was pumped at a flow rate of 0.5 mL min−1, purine nucleotides could be detected with 9 to 26 times the sensitivity in the latter system compared with the former, with the detection limit of 4 × 10−8 M for a 20 μL injection.
Voltammetric determination of nitrate with a modified carbon paste electrode
Authors: Neuhold Christian , Kalcher Kurt , Diewald Wolfgang , Cai Xiaohua , Raber Georg 
Published: May 2005

AbstractA method for the voltammetric determination of nitrate in drinking water is presented. Nitrate exerts a catalytic effect on the reduction and reoxidation of thallium (1 ↔ 0) in cyclic and differential pulse voltammetry, leading to a peak enhancement. Nitrate can be preconcentrated together with tetrachlorothallate(III) from hydrochloric acid solutions onto a carbon paste electrode modified with a liquid anion exchanger. (Amberlite LA2) under open circuit conditions. After reduction of the Tl(III) to Tl(0) at the electrode surface at a potential of −1.2 V (vs. SCE), the increase of the reoxidation current of Tl(III) to TI(I) by nitrate is exploited for analytical purposes. Linearity between current and concentration exists for 0.5 to 60 μg · mL−1 nitrate when applying anodic differential pulse vokammetry. Mechanical regeneration of the electrode surface is necessary after each measurement. The interference of other anions and the influence of methodical parameters are invistigated. The applicability of this method for the determination of nitrate in drinking wat concise overview on the the electroanalytical techniques for the Quantitative determination of nitrate is also presented.
Highly selective electrochemical detection of dopamine using interdigitated array electrodes modified with nafion/polyester lonomer layered film
Authors: Niwa Osamu , Morita Masao , Tabei Hisao 
Published: May 2005

AbstractThe highly selective electrochemical detection of dopamine has been developed using an interdigitated microarray (IDA) electrode coated with Nafion and polyester ionomer (Kodak AQ29D) layered films. Because high redox cycling of dopamine can be maintained in the AQ29D bottom layer, a low detection limit of 50 nmol/dm3 is obtained. Since the upper Nafion laybr prevents L‐ascorbic acid from diffusing into the AQ29D layer, the acid concentration in this layer rapidly decreases when potentiostating one IDA electrode (anode) above and the other (cathode) below the redox potential of dopamine. This is because L‐ascorbic acid molecules in the AQ29D layer are removed quickly by the electrochemical or electrocatalytic oxidation at the anode. On the other hand, almost all of the oxidized dopamine molecules are reduced at the cathode, which maintains a constant dopamine concentration in the film during measurement. After the potential step, the influence of L‐ascorbic acid is almost completely eliminated within a few seconds due to the reduction in acid concentration in the modified layer. As a result, dopamine can be detected quantitatively at the cathode in the presence of 100‐fold excess of L‐ascorbic acid.
pH measurements based on a palladium electrode
Authors: Shao Meijun , Xing Xuekun , Liu Chung‐Chiun 
Published: May 2005

AbstractThe feasibility of a metal palladium electrode as the pH sensor in air‐saturated aqueous solutions was evaluated. The measurement was based on an “on‐site” precleaning step and a potential decay process. The experimental results showed a linear pH response with a sensitivity of around 60 mV/pH and good reproducibiliry. The temperature effect on the measurement was also evaluated.
Integrated amino acid sensors for detection of L‐glutamate, L‐lysine, L‐arginine, and L‐histidine
Authors: Suzuki Hiroaki , Tamiya Eiichi , Karube Isao 
Published: May 2005

AbstractUsing microfabricated Clark oxygen electrodes, we integrated amperometric amino acid sensors to detect L‐glutamate, L‐lysine, L‐arginine, and L‐histidine. The oxygen electrodes consists of an anisotropically etched rectangular groove with a silver cathode and a Ag/AgCl anode, a Fluorinated Ethylene‐Propylene (FEP) gas‐permeable membrane, and a 0.1 M KCl electrolyte gel inserted after fabrication. Enzymes were immobilized on the gas‐permeable membrane. L‐glutamate was measured using L‐glutamate oxidase. To detect L‐lysine, L‐arginine, and L‐histidine, decarboxylases and autotrophic bacteria were used. The response times of the sensors ranged from 30 seconds to 10 minutes and a fairly linear relationship was observed between the output current of each sensor and the substrate concentration. We operated the sensors in the same buffer solution.
Reduction of electrooxidizable interferent effects: Optimization of the applied potential for amperometric glucose sensors
Authors: Jobnson Kirk W. , Bryan‐Poole Nancy , Mastrototaro John J. 
Published: May 2005

AbstractThe selectivity originally anticipated for enzyme‐based amperometric electrochemical sensors, specifically glucose sensors based on the oxidation of hydrogen peroxide, has not achieved due to the oxidation of interfering compounds. These interfering compounds are analytes normally present in physiological fluids or tissues that oxidize at the electrode surface and give “false” current readings. The effect of lowering the potential applied to a plantium black working electrode was studied. In vitro studies showed that lowering the applied potential from +0.60 V to +0.35 V greatly decreased the current due to oxidation of acetaminophen, a common interferent, while leaving the current output due to glucose virtually unchanged. In vivo studies revealed that the positive, constant offset observed when comparing the plasma glucose concentration to the glucose concentration indicated by an implanted glucose sensor was greatly minimized by reducing the applied potential from +0.60 V to +0.35 V. The offset was thought to be due to the oxidation of interferents. The linearity, magnitude, and stability of the sensor's in vitro and in vivo response to glucose was unchanged by the reduction in the applied potential.
Selectivity of liquid membrane electrode based on mercurated polystyrene as ion‐exchanger to anionic surfactants and soaps
Authors: Szczepaniak Walenty , Ren Maria 
Published: May 2005

AbstractAn electrode that employs a solution of mercurated polystyrene in 1,1′,2,2′ tetrachloroethane as the sensor in a liquid‐state membrane has been developed. The electrode was tested toward some common anions, anionic surfactants, and soaps. This electrode displays an unusually high level of selectivity for anionic surfactants, in particular to bis(2‐etylhexyl)sodium sulfosuccinate, sodium dodecylbenzenesulfonate, and sodium dodecylsulfate, over many common anions, such as NO, ClOF−, Cl−, and Br−. The electrode may find application in the analysis of surfactants, as an indicator electrode in the potentiometric titration and in the physicochemical studies of surfactant solutions.
A highly sensitive and selective catalytic method for the determination of ultratrace amounts of rhodium with oscillopolarographic detection
Authors: Zhi‐liang Jiang , Li‐sheng Wang 
Published: May 2005

AbstractA novel, highly sensitive, and selective catalytic method with oscillopolarographic detection for quantifying trace rhodium is described. The method is based on experimental results that Rh(III) has a very strong catalytic effect on the slow redox reaction between thoron and periodate in acetate buffer (pH 4.2) solution at 100°C. Thoron exhibits a sensitive oscillopolarographic wave at −0.60 V (vs. SCE). Ascorbic acid was used as interference eliminator and a quenching reagent. The detection limit of 15 ppt and calibration plot from 3.0 × 10−2 to 1.6 ppb Rh(III) were obtained by a fixed‐time procedure. Rhodium was determined in catalysts by the method with good results.
Simultaneous determination of glucose and sucrose by a dual‐working electrode multienzyme sensor flow‐injection system
Authors: Zhang Xianen , Rechnitz Garry A. 
Published: May 2005

AbstractA dual‐working electrode (K1 and K2) multienzyme sensor, made of carbon paste, glucose oxidase (GOD) membrane (on K1) and invertase (INV)/mutarotase (MUT)/GOD membrane (on K2), is proposed for simultaneous determination of glucose and sucrose. Interference to the K2 caused by H2O2 produced in the enzyme reaction on K1 can be eliminated by depositing a catalase (CAT) layer between K1 and K2. Acceleration of glucose mutarotation by MUT was found to be three times faster than by phosphate buffer. Glucose was determined directly from the response of K1, while sucrose was computed based on a formula derived from a two‐point calibration method. The maximum concentration of sucrose that could be determined depended strongly on the concentration of coexisting glucose. The activities of immobilized GOD, INV, MUT, and CAT were examined individually and found stable at room temperature for at least 1 month. The final loss of sucrose response activity was found to be due to denaturation of INV.
Amperometric biosensors for detection of L‐ and D‐amino acids based on coimmobilized peroxidase and L‐ and D‐amino acid oxidases in carbon paste electrodes
Authors: Kacaniklic V. , Johansson K. , Marko–Varga G. , Gorton L. , Jönsson–Pettersson G. , Csöregi E. 
Published: May 2005

AbstractAn apparent direct electron transfer between various electrode materials and peroxidases immobilized on the surface of the electrode has been reported in the last few years. An electrocatalytic reduction of hydrogen peroxide promoted by the immobilized peroxidase starts at about +600 mV (vs. Ag/AgCl) at neutral pH. The efficiency of the electrocatalytic current increases as the applied potential is made more negative and starts to level off it about −100 mV (vs. Ag/AgCl). Amperometric biosensors for hydrogen peroxide can be constructed with these kinds of peroxidase modified electrodes. By coimmobilizing a hydrogen peroxide‐producing oxidase with the peroxidase, amperometric biosensors can be made responding to the substrate of the oxidase within a potential range essentially free of interfering electrochemical reactions. Sensors for L‐ and D‐amino acids are shown based on coimmobilizing HRP with L‐amino acid oxidase (L‐AAOD) or D‐amino acid oxidase (D‐AAOD). The effects of the immobilization procedure, buffer (flow carrier), pH, taken amounts of enzymes, flow rate, and injection volume on the response were investigated. The addition of polyethylenimine (PEI) into the paste was found to increase the response considerably. All 20 of the most common L‐amino acids could be detected.
Resolution of ascorbic acid or catecholamine and indole alkaloid mixtures by pulse voltammetry at highly polished glassy carbon
Authors: Kamau Geoffrey N. , Rusling James F. 
Published: May 2005

AbstractMetallographic polishing of glassy carbon electrodes (GCEs) yields well‐defined oxidation peaks for two‐ and three‐component mixtures of ascorbic acid, dopamine (DA), catechol, and hydroquinone. Linear calibration plots of differential pulse voltammetric current versus concentration were obtained for each component at a range of 0.4 to 10 μM, Deterioration of voltammograms was observed when highly, polished GCE was aged in solution, resulting in positive shifts and broadening of the peaks. Lower limits of detection (LLD) in water at pH 7 were about 0.01 μM, for DA and 1 μM for AA. Highly polished GCEs were further applied to mixtures of naturally occurring indole alkaloids.
Electrochemical study of iproniazid and its analytical determination by differential pulse polarography
Authors: Martín M. E. , Borges T. M. , Arias J. J. , González S. 
Published: May 2005

AbstractIproniazid was found to be irreversibiy reduced in two steps, involving the exchange of two electrons and two protons each, by using tast polarography, normal pulse polarography (NPP), and cyclic voltammetry (CV). The rate constants of these two steps were found to be 5.8 × 10−6 and 4.2 × 10−6 and 4.2 × 10−6 cm s−1, respectively, and their corresponding diffusion coefficients 4.5 × 10−5 and 8.3 × 10−5 cm2 s−1, Also, α, the coefficient of cathodic transfer, was found to be 0.20 to 0.25 for the first peak and 0.17 to 0.15 for the second. On the basis of the electrochemical study performed, a differential pulse polarographic method for the determination of iproniazid over the concentration range of 5 × 10−7 M to 1 × 10−4 M was developed.
Binding of cytochrome c with 4‐pyridyl derivatives modified on the gold electrode
Authors: Xie Yuanwu , Dong Shaojun 
Published: May 2005

AbstractIn this work, the adsorption or binding of cytochrome c with 4‐pyridyl derivatives modified on the gold electrode was studied. It was found that the concentrations of electrolyte had much influence on the adsorption of cytochrome c. At lower concentrations of electrolyte (i.e., 2 mmol/L), the binding of cytochrome c with 4,4′‐bipyridyl or 4‐mercaptopyridine on the modified electrode surface can be detected by using the long dipping method for 4,4′‐bipyridine or pretreating the bis(4‐pyridyl) disulfide modified electrode at more negative potentials for 4‐mercaptopyridine. When the concentrations of the electrolyte increase, the binding of cytochrome c with the 4‐pyridyl derivatives changes from irreversible to reversible.
Automatic coulometric titrator with optical indication for acidity number determination
Authors: Podhájecký Petr , Langmaier Jan , Trojánek Antonin 
Published: May 2005

AbstractThe automatic coulometric titrator with a colorimetric indication is described, and its use is demonstrated on acidity number (AN) determinations. Compared to the standard volumetric procedure, the automated procedure yields more accurate results at lower sample and reagents consumption.
Electrochemical behavior of formetanate and chlordimeform pesticides
Authors: Subbalakshmamma M. , Reddy S. Jayarama 
Published: May 2005

AbstractThe electrochemical behavior of formetanate and chlordimeform is studied by using dc polarography, cyclic voltammetry, ac polarography, and differential pulse polarography (DPP) in universal buffers of pH 2.0 to 12.0, including 1 M HCIO4 and 1 M HCl. The number of electrons is determined by millicoulometry. Kinetic parameters such as transfer coefficients, diffusion coefficients, and heterogeneous forward rate constant values are evaluated using these techniques. The results obtained suggest the nature and mechanism of the electrode process. Differential pulse polarography is used for the estimation of formetanate in formulation.
Voltammetry of macromolecular metal complexes involving a nonreversible process: The Ni(II)‐polymethacrylate system
Authors: Argudo M. , Esteban M. 
Published: May 2005

AbstractThe voltammetric behavior of Ni(II) in the presence of polymethacrylic acid (PMA) is studied by normal pulse polarography (NPP), differential pulse polarography (DPP), reverse pulse polarography (RPP), cyclic voltammetry (CV), and anodic stripping voltammetry (ASV), Results obtained seem to indicate the lability of the Ni/PMA complex. Because of the lack of a model for macromolecular metal systems including Mn+/M(Hg) couples with slow rate charge transfer the usefulness of a model assuming electrochemical reversibility has been applied to a metal ion as Ni(II) with a slow rate of charge transfer. The agreement of the experimental results with that theoretically expected upon the model allows us the determination of the apparent formation constant K of the Ni/PMA complex and its dependence on the counterion concentration and on the degree of dissociation of PMA.
Polarographic study of the herbicide metamitron
Authors: Olmedo Carlos , Deban Luis , Vázquez Dolores , Pardo Rafael , Palmero Susana 
Published: May 2005

AbstractThe electrochemical characteristics of the herbicide metamitron have been studied in the pH range 1 to 9 by applying several polarographic techniques, namely DCP, TAST, and DPP, adsorptive stripping voltammetry, and cyclic voltammetry with HMDE. The reduction of this molecule evolves in four processes in pHs lower than 3, and in two steps between pH 3 and 9. All processes involve two electrons, are irreversible, and imply the reduction of the functions CN and N‐NH2 that are present in the molecule. Also, an adsorption phenomenon was observed in several processes. The quantitative determination of metamitron can be carried out in an acetate medium (pH4.6), by applying DPP, with a detection limit of 50 μg/L and using adsorptive stripping voltammetry, reaching a detection limit of 0.5 μg/L. Assays of commercial samples are illustrated.
Conductometric biosensors based on cholinesterases for sensitive detection of pesticides
Authors: Dzydevich Serge V. , Shuľga Alexander A. , Soldatkin Alexei P. , Hendji Andre' M. Nyamsi , Jaffrezic‐Renault Nicole , Martelet Claude 
Published: May 2005

AbstractDisposable conductometric microbiosensors based on immobilization of acetyl and butyrylcholinesterases (BuChEs) on interdigitated electrodes were fabricated. Enzymes were immobilized by crosslinking with bovine serum albumin and the differential output between the pair of electrodes covered with the enzyme membrane and the pair covered with albumin only was recorded. On the basis of these biosensors, a biochemical assay for pesticides in liquids was developed. Respective detection limits were 5 × 10−11 M for diisopropyl fluorophosphate (DFP), 10−7 M for trichlorfon, and 10−6 M for paracoxon‐methyl and paraoxon‐ethyl for the assays based on the enzymes tested. The presence of pesticides in the sample in concentration exceeding the detection limits can be detected after only 10 minutes of incubation, whereas, in order to extend the range of the determined pesticide concentration and to improve the accuracy of the assay, it is better to use incubation times longer than 30 minutes. Use of pyridin‐2‐aldoximide methiodide as reactivating agent allowed one to achieve the complete recovery of the sensor response when it was incubated in low‐concentrated pesticide solutions, e.g., less than 10−6 M for paraoxon‐methyl and during a short time, e.g., 10 to 20 minutes, for 10−5 M paraoxon‐methyl solution.
Characterization of a mediated amperometric biosensor for hypoxanthine using deflavo xanthine oxidase
Authors: Zhao Shishan , Luong John H. T. 
Published: May 2005

AbstractDeflavo xanthine oxidase was prepared by removing the flavine adenine dinucleotide (FAD) group from the native enzyme using 2 M CaCl2. The deflavo enzyme was effectively stabilized by 5 mM EDTA in Tris buffer solution, pH 8, and retained about 80% of its activity after several days when stored in this medium at 4°C. The deflavo enzyme was then used for the development of a mediated amperometric electrode for hypoxanthine/xanthine using 1,1′‐dimethylferricinium as mediator, and its performance characteristics were compared to a native enzyme electrode. The resulting deflavo xanthine oxidase electrode was not noticeably sensitive to oxygen in the presence of hypoxanthin while its capability to interact with ferricinium remained intact. The electrode sensor with immobilized deflavo enzyme showed high operational and storage stabilities with a detection limit of about 0.1 μM. No significant sensitivity loss was observed on the enzyme electrode after 150 repeated analyses during a 7.5 hour operation. The deflavo enzyme electrode retained 80% of its sensitivity when stored at 4°C after a month.
Electrochemical determination of ultralow levels (<10−12 M) of mercury by anodic stripping voltammetry using a chemically modified electrode
Authors: Turyan Iva , Mandler Daniel 
Published: May 2005

AbstractA glassy carbon electrode (GCE) coated with 4,7,13,16,21,24‐hexaoxa‐1,10‐diazabicyclo[8.8.8]hexacosane, Kryptofix‐222, has been used for the very sensitive and selective analysis of very low levels of mercury. A detection limit lower than 10−12 M (<0.2 ppt) was obtained applying anodic stripping voltammetry (ASV). The parameters that governed the sensitivity and possible interferences by other ions have been examined in detail. The electrode has been successfully applied for determining mercury in seawater, wastewater, and also in human saliva and amniotic fluid. The modified electrode exhibited high stability and, therefore, could be used repeatedly without mechanical regeneration.