bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of poly(ester‐sulfonic acid)‐coated microvoltammetric electrodes
Authors: Wang Joseph , Lin Meng Shan 
Published: February 2006

AbstractCoating microvoltammetric electrodes with a poly(ester‐sulfonic acid) film offers substantial improvements in their selectivity toward cationic neurotransmitters. This charged film tends to exclude anionic interferences, such as ascorbic acid or anionic biogenic amine metabolites. The temporal response of polyester‐ionomer‐coated microelectrodes is evaluated under dynamic flow‐injection conditions. Chro‐noamperometry and cyclic voltammetry are used to explore the discriminative properties of these microelectrodes under quiescent conditions. The attractive permselective, ion‐exchange, antifouling, and dynamic properties of the polyester ionomer, coupled with its low cost and strong adherence to surfaces, could be very valuable for in vivo brain electrochemistry.
Measurement of peroxide in oils by controlled‐potential coulometry using a vapor‐grown carbon fiber electrode
Authors: Uchiyama Shunichi , Shimamoto Miwa , Suzuki Shuichi , Hamamoto Osamu 
Published: February 2006

AbstractA small amount of a linoleic acid sample solution was dropped on a carbon fiber paste containing a mixture of acetic acid and methanol (1:1) saturated with potassium iodide. The present method needs no titration, and the only pretreatment needed for the sample is the dissolution of linoleic acid with an acetic acid—chloroform mixture (3:2). The complete electrolysis time of iodine produced by the reaction of iodide ion and peroxides was found to be 2–3 minutes. The results obtained by coulometry were in fairly good agreement with those obtained by conventional iodometry.
Evaluation of electrodes coated with metal hexacyanoferrate as amperometric sensors for nonelectroactive cations in flow systems
Authors: Thomsen Karsten N. , Baldwin Richard P. 
Published: February 2006

AbstractTwo electrodes modified with either nickel or cupric hexacyanoferrate films were evaluated and compared as sensors for nonelectroactive cations in a flow‐injection system. Both gave responses for group 1A and ammonium ions, but only the electrode modified with cupric hexacyanoferrate was sufficiently stable for use in flowing solutions. This electrode responded to K+, NH, Rb+, and Cs+ ions rather selectively. Within this group, the selectivity could be controlled from general to almost specific toward Cs+ by the potential at which the electrode was poised. The electrode was compatible with a mobile phase of dilute nitric acid commonly used in ion chromatography, and chromatographic detection limits of 2 × 10−7 M and linear responses over two decades were obtained. The electrode was applied to the ion chromatographic analysis of K+ and NH in urine and K+ in blood serum samples.
Electrochemical reduction of loprazolam mesilate in an aqueous medium
Authors: Arcos J. , El Jammal A. , Viré J.‐C. , Patriarche G. J. , Christian G. D. 
Published: February 2006

AbstractThe electrochemical characteristics of loprazolam mesilate have been evaluated in an aqueous solution using dc, ac, and normal and inverse pulse polarography, as well as cyclic voltammetry and controlled‐potential coulometry. This drug undergoes three different reduction steps. The first, a four‐electron transfer, corresponds to the reduction of the nitro group to give the corresponding hydroxylamine. The second, a two‐electron transfer, corresponds to the reduction of the azomethine group, either before or after (in an acidic solution) hydrolysis. The third wave corresponds to a four‐electron transfer in an acidic medium and to a two‐electron transfer in an alkaline medium. In an acidic solution, this third step involves the two‐electron reduction of the hydroxylamine group to the corresponding amine plus the two‐electron reduction of the double bond between N‐methylpiperazine and the imidazol group. In an alkaline solution, only the latter reduction takes place. Such behavior holds promise for analytical measurements of the drug.
Cathodic stripping analysis of DNA/RNA bases in nonaqueous media
Authors: Fish Judith R. , Ciszewski Aleksander , Malinski Tadeusz 
Published: February 2006

AbstractThe methods for the determination of nucleic acid bases by differential pulse cathodic stripping voltammetry in dimethyl sulfoxide are proposed and developed. One method uses mercury drop or film electrodes. The required anion is produced by the deprotonation of the parent molecule by added tetrabutyl‐ammonium hydroxide (TBAOH). Optimization of the method is discussed. The effects of deposition potential or time, scan rate, pulse height, TBAOH concentration, and other experimental parameters are examined. Included are the results of the determinations of thymine, uracil, cytosine, adenine, and guanine. The second method uses a mercury‐film rotating ring‐disk electrode. The anion, produced electrochemically at the disk held at a negative potential, is swept to the ring and deposited at a suitable, more positive potential. Detection limis for nucleic acid bases are 10−8 to 10−9 M.
Flow‐injection analysis of hydrogen peroxide using a horseradish peroxidase‐modified electrode detection system
Authors: Sánchez Pilar Dominguez , Blanco Paulino Tuñón , Alvarez José Maria Fernández , Smyth Malcolm R. , O'Kennedy Richard 
Published: February 2006

AbstractA flow‐injection analysis (FIA) system utilizing a horseradish peroxidase‐modified amperometric electrode is described. The enzyme was immobilized through adsorption onto a glassy carbon electrode, and the system is used to determine hydrogen peroxide at submicromolar levels. The response is based on the enzymatic reduction of hydrogen peroxide in the presence of hydroquinone acting as an electron mediator. The oxidized quinone produced in the enzymatic reaction is reduced at the electrode, and the reduction current was found to be proportional to the concentration of hydrogen peroxide. Calibration curves were found to be linear between 2.5 × 10−8 and 1.0 × 10−6 M, and the method has a detection limit of 1.0 × 10−8 M.
Application of partial least‐squares regression for signal resolution in differential pulse anodic stripping voltammetry of thallium and lead
Authors: Henrion André , Henrion René , Henrion Günter , Scholz Fritz 
Published: February 2006

AbstractThis work addresses the problem of signal resolution by partial least‐squares regression (PLS) for differential pulse stripping voltammograms. The performance of PLS is demonstrated for an example of calibration with mixtures of two analytes (Tl+and Pb2+) with strongly overlapping voltammograms. The accuracy of the determination of concentrations for validation mixtures was found to be considerably higher with PLS than with simple evaluation using currents observed at two potentials (requiring resolution of a system of two linear equations with two unknowns). Hence, PLS is recommended for computer‐assisted, on‐line voltammetric analysis of multicomponent systems.
Influence of the adsorption of organic compounds on submonoleyer stripping voltammetry of metals at solid electrodes
Authors: Hepel Maria 
Published: February 2006

AbstractThe effect of the adsorption of foreign organic compounds on the stripping voltammetry of metal adatoms deposited in submonolayer amounts at solid electrodes has been analyzed. It is shown that, for irreversible metal deposition processes, the adatom deposition current and, at a constant deposition time, the deposition charge are sensitive to the presence of the adsorbed foreign species on the electrode surface. Equations describing the dependence of the metal adatom deposition charge and the stripping peak current on the deposition potential, deposition time, concentration, and lateral exchange interactions between metal adatoms and adsorbed molecules have been derived. In the case of negligible exchange interactions, the peak current for adatom probe desorption decreases linearly with the surface coverage by foreign adsorbate. Direct evaluation of the kind and strength of exchange interactions is possible because the expression derived for the metal adatom desorption peak potential was used. It was found that the shift of the peak potential to more positive potentials is due to the lateral attraction exchange interactions, while the shift to more negative potentials was caused by the exchange repulsion interactions. No shift in the peak potential occurred in the absence of exchange interactions irrespective of the adatom surface coverage after the deposition step.
Differential pulse polarography of buspirone
Authors: Squella J. A. , Borges Y. , Bobadilla L. , Nuñez‐Vergara L. J. 
Published: February 2006

AbstractA new differential pulse polarographic method for the determination of buspirone pharmaceutical formulations is proposed. The method is based on the CN bond electroactivity of buspirone pirimidinic ring. Recovery study and content uniformity test are described. Adequate precision and accuracy were obtained. Sample preparation is easy, and no excipient separation is required.
Voltammetry of germanium telluride
Authors: Reddy K. V. Sridhar , Reddy S. Jayarama 
Published: February 2006

AbstractThe voltammetric behavior of semiconductor grade germanium telluride was studied by ac and differential pulse polarography. The electrochemical behavior and analytical procedures for the simultaneous estimation of germanium and tellurium in germanium telluride are discussed. The kinetic parameters of the electrode process are evaluated.
Electrochemical analysis for environmental control
Authors: Kalvoda R. 
Published: February 2006

AbstractElectroanalysis is widely used for environmental monitoring. This review summarizes the most progressive electroanalytical methods and the development of novel sensors that are the primary part of monitors and analyzers for environmental purposes. The utility of voltammetry, pentiometry, conductometry, and coulometry for environmental monitoring is surveyed and 64 references are provided.
Lactate‐dehydrogenase‐based biosensors for glyoxylate and NADH determination: A novel principle of analyte recyling
Authors: Schubert Florian , Scheller Frieder , Krasteva Nikolina G. 
Published: February 2006

AbstractTwo types of bienzyme electrodes based on the oxidation of glyoxylate to oxalate by NAD+ in the presence of lactate dehydrogenase (LDH) are described. The enzymes were entrapped in gelatin membranes and combined with an oxygen probe. A sequence sensor using LDH coupled with oxalate oxidase is useful for the determination of glyoxylate between 1 × 10−5 and 2.5 × 10−3 M. The sensor performance was optimized with respect to pH and cofactor concentration. As a novel approach to internal analyte recycling in biosensors, the LDH‐catalyzed recycling of NADH/NAD+ during the parallel oxidation of glyoxylate and reduction of pyruvate is utilized in a sensor for highly sensitive NADH measurement. Lactate monooxygenase was coupled as an auxiliary enzyme to indicate the lactate formed from pyruvate. The calibration curve of the proposed sensor is linear between 7 × 10−6 and 1.8 × 10−3 M NADH in the absence of glyoxylate (i.e., without analyte recycling) and between 3 × 10−8 and 2 × 10−6 M in the presence of glyoxylate (i.e., with analyte recycling).
Electrochemical cell design and experimental procedures for measuring electrode reaction kinetics at low and variable temperatures
Authors: Mu Xi Hai , Schultz Franklin A. 
Published: February 2006

AbstractAn electrochemical cell is described for measuring electrode reaction kinetics at low and variable temperatures in nonaqueous solvents. The cell contains a working electrode of conventional size (at which the standard heterogeneous electron transfer rate constant is determined by cyclic voltammetry) and a microelectrode (at which the diffusion coefficient is measured by steady‐state microelectrode voltammetry). Uncompensated solution resistance is minimized by a combination of close placement of the reference electrode salt bridge tip and the working electrode surface and instrumental positive feedback. Cell performance is evaluated by an examination of ferrocene oxidation and manganese(III) (tetraphenylporphyrin) chloride reduction at temperatures between 229 and 298 K. Comparison of the responses from these reversible and quasi‐reversible redox couples in the same solution demonstrates that the effects of uncompensated solution resistance are absent from the experimental measurements and that increases in the cyclic voltammetric peak potential separation with sweep rate are due entirely to the kinetics of the Mn(III)/Mn(II) electrode reaction.
Electrochemical NO2 gas sensors: Model and mechanism for the electroreduction of NO2
Authors: Chang Si‐Chung , Stetter Joseph R. 
Published: February 2006

AbstractTwo types of sensing devices have been studied in order to elucidate the mechanism of response of amperometric gas sensors. A high‐surface‐area electrode (HSAE) sensor produces fast electrode reactions, and the steady‐state sensor signals are controlled either by permeation or by the supply of analyte to the sensor. For low‐surface‐area electrode (LSAE) sensors, a kinetically controlled signal is observed. A mechanism that involves a “chemically” induced changes in the gold electrode surface oxide coverage is proposed, and the activation energy for NO2 reduction at a gold electrocatalyst is calculated. A general model of sensor response is proposed that can describe the behavior of the steady‐state response for both HSAE and LSAE sensors.
Polarography of penem carbapenem antibiotics and the azetidinone intermediate
Authors: Bersier Pierre M. , Bersier Jacques , Sedelmeier Gottfried , Hungerbühler Ernst 
Published: February 2006

AbstractVarious penems, structurally closely related carbapenems, and the intermediate 4‐acetoxyazetidin‐2‐one were studied by direct current sampled dc, differential pulse polarography (DPP), cyclic voltammetry, and ac tensammetry. Optimum pH ranges for the determination of 4‐acetoxyazetidin‐2‐one and the various penems are discussed. In Britton—Robinson buffer (BRP) penems exhibit (pH 3) one stable reduction wave, which can be exploited analytically. Carbapenems exhibit stability problems in BRP (pH 3). They can be determined after conversion by hydrolysis into a stable imine form. Useful linear concentration ranges are 10 to 140 μg/mL for 4‐acetoxyazetidin‐2‐one and 20 to 170 and 0.5 to 70 μg/mL for penems using dc polarography and DPP, respectively. The precision of the proposed analytical methods is acceptable, with relative standard deviations around 2.5% for the assay of 4‐acetoxyazetidin‐2‐one and 2.5 and 2–5% for the penem and carbapenem, respectively.
Poly(ester‐sulfonic acid)‐coated mercury film electrodes for anodic stripping voltammetry
Authors: Wang Joseph , Taha Ziad 
Published: February 2006

AbstractThe antifouling properties of poly(ester‐sulfonic acid) coatings are explored for stripping voltammetric measurements of trace metals in the presence of organic surfactants. Up to at least 100 mg/L of gelatin, Triton X‐100, albumin, or humic acid does not affect the stripping response of heavy metals. A relative standard deviation of 4% is obtained for 20 successive measurements of 5 × 10−7 M lead in the presence of 50 mg/L Triton X‐100. Experimental variables, including film thickness, rotation speed, analyte, and surfactant concentrations, are explored. Potential for speciation work and assays of clinical samples is also indicated. The resistance to surfactant interferences, coupled with the simple coating procedure, good mechanical stability, and low cost, make poly(ester‐sulfonic acid) coatings very attractive for anodic stripping voltammetry.
The electrochemical determination of free CuO in YBaCuO superconductor materials
Authors: Gruner Wolfgang , Stahlberg Rudi , Brainina Khjena Z. , Akselrod Nadeshda L. , Kamyshov Valentin M. 
Published: February 2006

AbstractUsing a carbon paste electroactive electrode (CPEE), the mechanism of cathodic and anodic electrochemical processes on several copper oxide compounds in 0.1–1.0 mol/L hydrochloric acid media has been investigated. It is shown that the cathodic reaction of CuO is much more sensitive under selected conditions than that of other copper‐containing phases, which results in the variation of the preparation procedure of YBaCuO superconducting materials. A quantitative analysis is thus possible to determine the free CuO with a content of 0.5–10 wt% YBa2Cu3O7‐x with about 10–20% relative standard deviation. The cathodic reduction reaction by chemical—electrochemical mechanisms or by solid state conversion is also discussed.
Development of a computerized electrochemical system for stripping voltammetry
Authors: Hernández‐Brito J. J. , Cardona‐Castellano P. , Pérez‐Peña J. , Gelado‐Caballero Ma. D. 
Published: February 2006

AbstractA computer‐controlled electrochemical system has been developed to determine heavy metal using stripping voltammetry. The system consists of a potentiostat (which we have designed and developed), a polarographic static mercury electrode (303A, PAR), an analog‐digital conversion board (DT2801‐A), a personal computer, and an HP7440 plotter. The potentiostat runs between −2.0 to +2.0 V with multirange current selection between ±50 nA and ±100 μA. There are various outlet channels with different time constants and noise levels. The fastest channel can detect processes on the order of 200 μs with a noise level of ±2.0 nA, while for 30 ms processes the noise is ±100 pA. The software developed controls the sequences of potentials, acquires and stores the currents, and plots them at its convenience. The system has been tested successfully in the determination of different metals using anodic and cathodic stripping voltammetry with different types of waveforms.
Uncertainty in the potential of a reference interface in liquid/liquid measurements
Authors: Vanýsek Petr 
Published: February 2006

AbstractElectrochemical research on interfaces between two immiscible electrolytes often relies on establishing the so‐called reference interface. This interface is formed by two immiscible solvents, each with a dissolved electrolyte. The electrolytes are chosen such that the two solvents share one common ion. The potential of the interface is then determined by a calculation. In this study, it is shown that this ionsensitive interface does not always have the commonly accepted potential value. Reasons for this and corrective actions are given.
Polarographic estimation of conjugated enes
Authors: Husain Sajid , Sastry G. S. R. , Prasad P. Ravi , Sarma G. V. R. 
Published: February 2006

AbstractA polarographic method for the estimation of styrene, isoprene, and 1,3‐cyclohexadiene using 0.02 M tetrabutyl ammonium iodide in N,N‐dimethylformamide as supporting electrolyte has been developed. The method is useful for the quality assurance of conjugated enes as well as for determining trace quantities of these compounds in industrial products such as polymers, elastomers, or adhesives.
An instrument for alternating current voltammetry featuring a digital phase‐sensitive detector: Application to flow‐injection analysis using ac amperometry
Authors: Curran David J. , Gelbert Mark B. , Kingsley Edward D. 
Published: February 2006

AbstractAn instrument, which incorporates a lock‐in amplifier based on a digital phase sensitive detector, has been designed and constructed for ac electrochemical measurements of solutions containing low concentrations of analyte. The performance of the lock‐in amplifier was characterized experimentally. Phase angle resolution is better than 0.01°, and signal capture ratios up to about 80,000 can be attained. An up/down counter replaces the multiplier of the typical analog phase‐sensitive detector. Provision was made to sum the net count over a preselected number of cycles of the reference signal to improve the sensitivity and signal‐to‐noise ratio of the phase‐sensitive detector. The lock‐in amplifier output can be read on a recorder via a digital‐to‐analog converter or sent to a computer. Overall instrument performance is demonstrated using ac amperometry at a carbon paste electrode and flow injection techniques to determine o‐dianisidine. Peak currents corresponding to a solution concentration of 6 nM in the detector were successfully measured.
A clay‐modified electrode for ion‐exchange voltammetry
Authors: Wielgos Todd , Fitch Alanah 
Published: February 2006

AbstractClay modified electrodes are characterized and optimized for their analytical use in ion‐exchange voltammetry using Ru(NH3) as a test ion. The effect of electrolyte concentration on the conductivity of the film, the time for signal development, the amount of clay coating, and rinsing procedures are investigated. The linear range of the clay‐modified electrode was found to be four orders of magnitude, and 100 pmol of the complex were sensed.
Study of electrochemical reduction of selenium (+4) using square wave voltammetry
Authors: Zelić Marina , Branica Marko 
Published: February 2006

AbstractThe electrochemical reduction of selenium (+ 4) on hanging mercury drop electrode (HMDE) has been studied using square wave voltammetry (SWV). The product of the first, very complex electrode reaction can be further reduced in a process characterized by reactant and product adsorption. The height of the stripping peak increases up to four times with the addition of Cu2+ ions, although the electrode reaction becomes less reversible. The square wave cathodic stripping peak currents are an order of magnitude higher than the corresponding differential pulse values, but the detection limit (3 × 10−10 mol/L) is practically the same for both techniques. The concentration of selenium (+ 4) in rainwater samples has been determined.
The construction of two long‐optical‐path spectroelectrochemical cells
Authors: Shi Minglian , Gao Xiaoxia 
Published: February 2006

AbstractThe construction and operation of two novel, long‐optical‐path‐length spectroelectrochemical cells are described. In addition to giving a sensitive optical response, the cells are more convenient to use than conventional designs. Model systems are used to demonstrate that the cell with a gold foil working electrode functions well at positive potentials while the pure mercury working electrode is particularly attractive for studies in negative potential ranges.
Voltammetric determination of thiram following adsorptive accumulation on a rotating gold disk electrode
Authors: Sevilla M. Teresa , Procopio Jesús Rodriguez , Pinilla Jose M. , Hernandez Lucas 
Published: February 2006

AbstractThe oxidation of thiram was studied by cyclic voltammetry on a rotating gold disk electrode. The oxidation process involves the adsorption of thiram. The limit of detection obtained was 0.04 μg/mL and the method was applied to thiram determination in formulations. The spontaneous adsorption of thiram on the rotating gold disk electrode produces a substantial enhancement of the voltammetric signal. This effect can be exploited as an effective accumulation step prior to the voltammetric measurement. The best results are obtained thiram solutions adjusted to pH 1 with phosphoric‐acetic acid buffer, an accumulation potential of 0.0 V, and a scan rate of 400 mV/s for the voltammetric step. Under these conditions, the detection limit was 0.3 ng/mL after 10 minutes of accumulation. The method was applied to the determination of thiram in water with good results.
Amperometric investigation of nickel and cobalt complexes with cephalexin
Authors: Kapetanović V. , Sužnjević D. , Veselinović D. 
Published: February 2006

AbstractCephalexin complexes with Ni(II) and Co(II) ions have been studied polarographically in an aqueous medium with a pH of 7–7.5, and an ionic strength of 0.2. It is shown that Ni(II) and Co(II) ions and cephalexin form [NiCEF]+ and [CoCEF]+ complexes under the experimental conditions cited. The stoichiometric composition of the complexes and the stability constants, log K′ = 3.16 for Ni(II)‐cephalexin and log K′ = 3.09 for Co(II) cephalexin, were determined by the Leden method.