bluuebunny/crossref_metadata_2025_split huggingface dataset:
The polarographic behavior of the antitumor agent tauromustine and assay of its tablets
Authors: Belal F. 
Published: May 2005

AbstractTauromustine was found to be reducible at the dropping mercury electrode (DME) over the whole pH range in Britton‐Robinson (BR) buffers. A well‐defined cathodic wave was produced in the acid range, followed by an ill‐defined, more negative additional wave starting from pH 4.0. The main reduction wave was characterized as being diffusion‐controlled, although adsorption phenomena played a limited role in the electrode process. Using either direct current or differential pulse polarographic modes, the limiting current‐concentration plot is linear over a convenient range with a minimum detectability of 5 × 10−8 M using the latter technique. Tablets containing tauromustine (20 and 50 mg) were successfully analyzed adopting the United States Pharmacopoeia (USP) content uniformity test.
The study of differential pulse adsorptive stripping voltammetry of co(II)/1‐nitroso‐2‐naphthol chelate
Authors: Han Jilin , Chen Hongyuan , Gao (H. Kao) Hong 
Published: May 2005

AbstractCobalt (II)/1‐nitroso‐2‐naphthol chelate in citrate/ammonium citrate (pH 8.6) buffer solution is studied by adsorptive stripping voltammetry on a static mercury drop electrode (SMDE). The adsorbed chelate yields one distinct peak at −0.51 V, which can be utilized to quantify trace cobalt. The interfacial and redox behavior are evaluated by cyclic voltammetry and pulse polarography. The effect of accumulation potential, accumulation time, and concentration of ligand on the reduction peak currents of the chelate have been discussed. Possible interference metal ions are also investigated. The peak current is proportional to the concentration of cobalt in the range of 10−7 to 10−9 M (correlation coefficient 0.998). The relative standard deviation is 2.6% at the concentration of Co(II) 2.2 × 10−8 M (n = 7). The detection limit of Co(II) is as low as 0.05 ppb (2‐minute accumulation).
Electrochemical determination of oxygen permeability of isolated stratum corneum membranes
Authors: Wilson Alicia L. , Emons Hendrik , Heineman William R. , Pickens William L. , Hoath Steven B. 
Published: May 2005

AbstractThe mammalian stratum corneum is a thin, highly organized polymeric membrane which is relatively impermeable to water but permeable to some gases including oxygen. Isolated stratum corneum membranes from perinatal Sprague‐Dawley rats were mounted under electrodes used to determine the rate of diffusion of oxygen through the membrane. These membranes were consistently found to be permeable to oxygen, which could be quantitatively determined at a gold electrode at −0.6 V (vs. a Ag/AgCl electrode). The stratum corneum membrane was found to be anisotropic, with greater oxygen permeability when the gas diffused toward the electrolyte from the side of the membrane which would be oriented toward the exterior of the animal than when it diffused in the opposite direction. There is also evidence of anatomic site heterogeneity in the permeability of the membranes.
Amplified vitamin C sensor based on the cyclic reaction between L ‐ ascorbic acid and dehydroascorbic acid
Authors: Uchiyama Shunichi , Hasebe Yasushi , Suzuki Shuichi 
Published: May 2005

AbstractThe current response of L‐ascorbic acid at an ascorbate‐oxidase membrane electrode (detecting the decrease of oxygen) has been amplified by adding dithiothreithol into the sample solution. The signal amplification is based on the cyclic reaction between L‐ascorbic acid and dehydroascorbic acid, which leads to the regeneration of L‐ascorbic acid. The amplification factor was increased up to 22.5 (at pH 7.5) when 5 × 10−3 M dithiothreithol solution was used. This amplification system enables the determination of not only L‐ascorbic acid but dehydroascorbic acid, and the detection limit for vitamin C was found to be 2 × 10−7 M.
Hydrogen peroxide‐sensitive electrode based on horseradish peroxidase‐modified platinized carbon
Authors: Cardosi M. F. 
Published: May 2005

AbstractElearodes are described based on horseradish peroxidase (HRP) modified platinized carbon particles which are capable of reducing hydrogen peroxide at 0.0 V (vs. SCE). The HRP was covalently attached to the surface of the carbon particles via cyanuric chloride. Energy‐dispersive X‐ray analysis confirmed the presence of cyanuric chloride on the surface of the carbon. Electrochemical studies on these electrodes indicated that they were stable for extended periods and that the bound HRP was capable of mediating the electrocatalytic reduction of hydrogen peroxide.
Use of calixarenes as modifiers of carbon paste electrodes for voltammetric analysis
Authors: Arrigan Damien W. M. , Svehla Gyula , Harris Stephen J. , McKervey M. Anthony 
Published: May 2005

AbstractThe use of calixarene‐based chemically modified carbon paste electrodes (CMCPEs) in voltammetric analysis is reported here. A polymeric calixarene I was incorporated successfully and used for the accumulation of lead (II), copper(II), and mercury(II) ions with subsequent anodic stripping voltammetry as the determination step. The electrode response depended on the calixarene content, the electrolyte, and the preconcentration time and analyte concentration as well as the constituents of the sample matrix. The presence of alkali metal ions in the sample solution was found to have an adverse effect on electrode response, due to the preferable binding of these ions by the calixarene units immobilized in the carbon paste. Attempts to overcome this interference employed a nonpolymeric sulfur‐containing calixarene, the thioamide II, in the electrode. The stripping current was not enhanced by introduction of this compound as an electrode modifier, perhaps due to adsorption of the calixarene on the carbon partnicles via its metal ion binding site. However, the application of calixarenes to voltammetric methods of analysis is demonstrated and provides an additional use of calixarenes in electroanalysis.
The auto‐drop static mercury electrode—a novel concept
Authors: Yarnitzky Chaim N. , Rosenzveig Mirit 
Published: May 2005

AbstractSmoothed operation of the SMDE is achieved by activating the mercury valve, detecting the natural mercury drop fall, and closing the valve after a predetermined interval. Constant area static mercury drops are obtained by this protocol without the need to resort to a mechanical knocker. This technique has proven very useful for flow electrochemical detection systems.
Computer elimination of voltammogram deformations by catalytic reaction to improve their signal for quantitative analysis. Determination of catalytic rate constant
Authors: Rievaj Miroslav , Korgová Elena , Mesároš Štefan , Bustin Dušan 
Published: May 2005

AbstractChemical reactions coupled with the electrode process lead to the change of shape and/or height of the measured voltammogram, thus complicating its application in quantitative analysis. This article describes a fractional differintegration procedure which corrects voltammograms for interference by catalytic reactions while simultaneously providing a value for the catalytic rate constants. A peocedure is proposed which utilizes the change of the shape of a reversible charge transfer voltammogram caused by slow and moderately fast catalytic reaction to the elimination of its influence on the analytical signal. It is based upon computer symmetrization of the voltammogram by fractional differentiation of the optimized order and the following correction of the signal. The procedure also enables an advantageous determination of the catalytic reaction rate constant. Since the height of the symmetrized signal is more sensitive to the catalytic process than the height of the original voltammogram, it is of special importance for lower rate constant values. Both elimination of catalytic influence and the determination of rate constant were tested with the Ti(III) NH2OH catalytic system.
Polarographic, voltammetric, and HPLC‐EC of pharmaceutically relevant cyclic compounds
Authors: Bersier Pierre M. , Bersier J. 
Published: May 2005

AbstractThis review gives a survey of the polarographic and voltammetric behavior of selected pharmaceuticals and substances of pharmaceutical relevance of various ring sizes (3–7, 14‐membered rings, polyring drugs), besides macrocyclic compounds and their determination by polarography, voltammetry, and liquid chromatography–electrochemical detection (HPLC–EC) in the practical laboratory.
Electron transfer from diaphorase in water/triton X‐100/butyl acetate microemulsion
Authors: Hall Geoffrey F. , Turner Anthony P. F. 
Published: May 2005

AbstractThe transfer of electrons from an enzyme in a microemulsion system to a glassy carbon electrode, via mediators of different solubilities, is demonstrated. A bienzymic reaction is carried out in a microemulsion formed by the nonionic detergent Triton X‐100 in butyl acetate. The enzymes used are alcohol dehydrogenase (ADH. EC 1.1.1.1) and diaphorase (EC 1.8.1.4). ADH catalyzes the conversion of primary alcohols to aldehydes with the concomitant reduction of its cofactor, nicotinamide adenine dinucleotide (NAD+) to NADH. Diaphorase reoxidizes NADH and can utilize a variety of molecules as an electron acceptor. It is demonstrated that these may be water soluble or solvent soluble.
NADH electrochemical sensor for the enzymatic determination of L‐ and D‐lactate and 3‐hydroxybutyrate using a flow injection analysis
Authors: Marrazza G. , Cagnini A. , Mascini M. 
Published: May 2005

AbstractA NADH sensor in the submicromolar range, assembled in a wall‐jet cell using a flow injection analysis (FIA) procedure, was studied and coupled with enzyme reactors. Spectroscopic graphite was used as electrode material without any mediator. The measurements were performed at an applied potential of + 500 mV vs. Ag/AgCD. L‐, D‐lactate, and 3‐hydroxybutyrate dehydrogenase were immobilized on aminopropyl‐controlled pore glass beads using glutaraldehyde in a packed‐bed enzyme reactor, L‐, D‐lactate, and 3‐hydroxybutyrate were oxidized in the presence of NAD+, and an equivalent amount of NADH was produced and measured. By careful choice of pH, buffer, and NAD+ concentration, the analytes could be measured in the range of 1 × 10−6 to 1 × 10−4 M in a few seconds. Large blank effects were evidenced with this procedure if the carrier and the sample differed in ionic strength of about 1 × 10−3 M when the total ionic strength is 0.8 M. Therefore, the use of such a system for reach samples requires further investigation.
Voltammetric behavior of 1,4‐dihydropyridine calcium antagonists
Authors: Alvarez‐Lueje A , Nuñez‐Vergara L. J. , Squella J. A. 
Published: May 2005

AbstractThe anodic electrochemical behavior of the five members of the 1,4‐dihydropyridine calcium antagonists family was studied. In all of the studied compounds (nifedipine, nitrendipine, nimodipine, nicardipine, and furaldipine), the oxidation process reveals only one anodic peak due to the twoelectron oxidation of the dihydropyridine ring to form the pyridine derivative compound. The differential pulse voltammetric technique was used for the quantitation of the 1,4‐dihydropyridines in pharmaceutical forms. The voltammetric determination developed here represents a good analytical alternative, because sample preparation is easy (no excipient separation is necessary), is not time consuming, and is adequately accurate and precise. Furthermore, the developed method can be applied as an important tool in photodegradation studies.
Fast‐pulsed electrochemical detection at noble metal electrodes: The frequency‐dependent response at gold electrodes for chromatographically separated carbohydrates
Authors: Roberts Richard E. , Johnson Dennis C. 
Published: May 2005

AbstractWaveforms used in pulsed electrochemical detection (PED) have frequencies of ca. 1 Hz when optimized to give a maximum signal‐to‐noise ratio (S/N) for carbohydrates. However, higher frequencies are desired for application of PED to capillary electrophoresis (CE) and microcolumn lipuid chromatography (MLC), which can produce narrow elution peaks. Minimization of the time periods for oxidative cleaning and reductive reactivation in PED waveforms generated by the Dionex pulsed Electrochemical Detector allows the increase in waveform frequency to ca. 3 Hz without change in the traditional time period of 200 ms, prescribed for integration of the anodic current. However, further increase in frequency requires a decrease in the integration period with a corresponding loss of signal strength.
Voltammetric studies with copper microelectrodes fabricated from borosilicate‐coated copper microwire
Authors: Bond A. M. , Brainian Kb. Z. , Loppenol M. 
Published: May 2005

AbstractCopper microwire coated with a thin film of borosilicate glass can be used to provide a new and convenient method for fabricating high quality 7 μm diameter copper microdisk electrodes. The reversible reduction of the cobaltocenium cation to cobaltocene was studied in acetonitrile to assess the quality of electrode fabrication. If electrode polishing followed by potential, wave shape, and limiting current are all as theoretically expected for a reversible steady‐state voltammogram. However, if the nitric acid treatment is believed to remove a thin film of copper oxide which acts as an insulator with respect to the reduction of the cobaltocenium caton and, therefore, effectively decreases the electrode area. Studies on glycine which represents an example of a biologically important molecule previously determined by voltammetry at conventionally sized copper electrodes also were undertaken. An extremely well‐defined response is observed for glycine at a copper microelectrode, indicating the analytical usefulness of this new class of microelectrode. Additional aspects of the glycine mechanism which intimately involve the copper electrode surface are elucidated from the microelectrode studies.
Adsorption voltammetry of the titanium‐4‐[(4‐diethylamino‐2‐hydroxyphenyl)‐azo]‐5‐hydroxynaphthalene‐2,7‐disulfonic acid (beryllon III)system
Authors: Zhao Jingzhong , Sun Dezhi , Wei Xilian , Jin Wenrui 
Published: May 2005

AbstractThe behavior of Ti (IV) complex with Beryllon III, Ti (IV) A, at a mercury electrode has been investigated in acetate buffer (HOAc/NaOAc). The adsorption phenomena were observed by linear‐sweep voltammetry. The mechanism of the electrode reaction was found to be the irreversible reduction of Beryllon III in the complex adsorbed on the surface of the electrode. In 0.005 mol/LHOAc + 0.1 mol/L NaOAc and 5 × 10−10 to 1 × 10−7 mol/L, the detection limit of the method is 2.5 × 10−10 mol/L for a preconcentration time of 120 seconds. This method has been applied to samples of human hair.
Disposable electrodes for field screening of trace uranium
Authors: Wang Joseph , Baomin Tian , Setiadji Rossi 
Published: May 2005

AbstractA novel electrochemical sensor for trace (μg/L) Uranium, based on adsorptive stripping potentiometry, is described. The sensor operation relies on the adsorptive accumulation of the uranium‐cupferron complex onto a mercury‐coated screen‐printed carbon electrode. The disposable nature of these electrodes makes them very attractive for on‐site characterization of nuclear energy sites. Various variables affecting the potentiometric stripping response were characterized and optimized to yield low‐detection limit (e.g., 0.5 μg/L following a 5 minute adsorption) and good precision (relative standard deviation (RSD) = 1.4% for n = 15, 25 μg/L uranium). Convenient measurements can be carried out in nondeaerated and quiescent solutions. Applicability to the quantitation of uranium in groundwater samples is demonstrated.
Ultratrace determination of molybdenum in the presence of 2‐(2′‐thiazolylazo)‐p‐cresol by catalytic‐adsorptive stripping voltammetry
Authors: Farias Pércio A. M. , Obara Aniy K. , Nóbrega Armi W. , Gold Jon S. 
Published: May 2005

AbstractThe adsorptive collection of the molybdenum (VI) complex of 2‐(2′‐thiazolylazo)‐p‐cresok (TAC), coupled with the catalytic current of the adsorbed complex, yield an ultrasensitive voltammetric procedure for the determination of molybdenum. Optimal experimental conditions were found with the use of a stirred acetate buffer (pH 2.9) supporting electrolyte, a TAC concetration of 1.0 × 10−5 M, and a concentration of 0.1 M potassium nitrate. In addition, a preconcentration potential of −0.13 V (vs. Ag/AgCl), equilibrium time of 30 seconds, and an anodic scan rate of 200 mV/s from −0. 93 to −0. 20 was used. A catalytic effect was observed when nitrate was present. The response was found to be linear over a concentration range of 0.0 to12.0 μg L−1 Mo (VI). For a preconcentration time of 3 minutes, the detection limit was found to be 11 pM. Possible interferences by anions and other trace metals were investigated. The interference by copper may be masked by CDTA, and sequential determination with molybdenum is possible. The merits of the procedure are demonstrated in the analysis of sea and mineral water.
Bioelectrocatalysis and diffusion kinetics glucose oxidase: Glucose reaction using a water‐soluble 1,1′‐dimethylferrocene‐2‐hydroxypropyl‐β‐cyclodextrin complex
Authors: Brown R. Stephen , Luong John H. T. 
Published: May 2005

AbstractThe mediation of the glucose oxidase (GOx): glucose reaction by 1,1′‐dimethylferrocene (DMF) solubilized in 2‐hydroxypropyl‐β‐cyclodextrin (hpβCD) was studied. Cyclic voltammetry (CV) was used to examine the effects of complexation with hpβCD on the oxidation potential of DMF through the analysis of half‐wave potentials. This indicated a one‐to‐one complex between DMF and hpβCD, with a formation constant of (1.2 ± 0.3) × 103 M−1 The working potential for electrodes using the mediator complex could be reduced by minimizing the hpβCD concentration, though a lower limit of 2.5 mM was observed for the 0.5 mM DMF solutions used in this work, below which the DMF became insoluble, and its electrochemistry was not well behaved.Cyclic voltammetry measurements at different scan rates were used to determine kinetic‐parameters, resulting in a second‐order rate constant for the reaction of oxidized DMF with reduced GOx of 3.4 × 104 M−1 s−1 to 1.9 × 104 M−1 s−1 for solutions containing 4 mM to 10 mM hpβCD. These values are on the order of one‐quarter the literature value for free DMF and are in the range reported for ferrocene, indicating that the complexed DMF is able to function as an efficient mediator. The rate constant determined for 2.5 mM hpβCD was anomalously high and probably indicated insolubility of the DMF at this hpβCD concentration. A rate constant versus the hpβCD concentration plot was used as an indication of the lower limit of hpβCD concentration at which reproducible results could be obtained.
Adsorptive stripping voltammetric determination of trace tellurium in the presence of oxine
Authors: Wang Joseph , Lu Jianmin 
Published: May 2005

AbstractUltratrace levels of rellurium can be determined after adsorptive collection of the tellurium‐oxine complex on a hanging mercury drop electrode. The adsorptive‐catalytic stripping voltammetric procedure is optimized to give an extremely low detection limit of 8 ng/L (6.4 × 10−11 M) tellurium following 10 minutes accumulation. The improved sensitivity (over conventional stripping methods for tellurium) is coupled with high selectivity and precision. For example, the response is not affected by a large excess of selenium, which commonly interferes in analogous anodic stripping measurements. The relative standard deviation (at the 500 ng/L level) is 1.9%.
Electrochemical behavior of redox proteins entrapped in nafion films
Authors: Bianco Pierre , Haladjian Jean 
Published: May 2005

AbstractSeveral redox proteins are studied at Nafion‐coated pyrolytic graphite (PG) electrodes. The electrochemical behavior of polyheme c‐type cytochromes and spinach ferredoxin is described using cyclic and square‐wave voltammetry (SWV). No signals are detected when Nafion‐coated electrodes are exposed to the protein solutions. In contrast, electrochemical responses are observed when droplets of protein solutions, deposited on the PG surface are dried then entrapped in Nafion layer. These Nafion‐modified electrodes permit one to detect very small amounts (1 μg) of cytochrome c3. The stability of entrapped molecules upon repetitive cycling has been investigated. Such modified electrodes offer new perspectives for studying proteins confined at electrode surfaces.
Investigation on mechanisms for the electrooxidation of some bile pigments by spectroelectrochemistry
Authors: Niu Jianjun , Dong Shaojun 
Published: May 2005

AbstractThe electrooxidation behavior of bilirubin (BR), biliverdin (BV), purpurin (Pu), and choletelin (Ch) in dimethylformamide (DMF) have been investigated by voltammetry, in situ electron spin resonance (ESR) thin‐layer spectroelectrochemistry and especially in situ rapid scan spectrometer. Radical cations and multiple chemical reactions were found to occur during the electrooxidation processes of these bile pigments The proposed oxidation mechanism of BR corresponds to mixed processes of ECECC and ECECEC, while that of BV and Pu are all ECECC.
Surfactant modified carbon paste electrode: Part 2: Analytical performances
Authors: Digua K. , Kauffmann J.‐M. , Khodari M. 
Published: May 2005

AbstractThe hexadecylsulfonic acid (sodium salt) modified carbon paste electrode (HDSNa‐CPE) has been studied in batch and flowing systems, and its analytical performance has been established in comparison with a conventional carbon paste electrode (CPE). Amperometry, linear scan, and preconcentration voltammetry have been used for the investigation of several analytes of pharmacological interest. Because of the presence of surface functionalities, markedly different electrode responses have been observed at the HDSNa‐CPE depending on the nature (hydrophobicity and charge) of the investigated molecule. The HDSNa‐CPE showed, in linear scan voltammetry and for all the species investigated, higher responses compared to the CPE. The HDSNa‐CPE showed important current enhancements in voltammetric analysis of hydrophobic organic cations in acidic media and at low ionic strength.
Voltammetric determination of the antioxidant tert‐butylhydroxytoluene (BHT) at a carbon paste electrode modified with nickel phthalocyanine
Authors: Ruiz M. Asunción , áńez‐Sedeń Paloma , Pingarrón José M. 
Published: May 2005

AbstractThe voltammetric behaviar of the antioxidant tert–butyltydroxytoluene (BHT) at a carbon paste electrode modified with nickel phthalocyanine is described, and method for the determination of this antioxidant based on its oxidations at the modified electrode it proposed. Cyclic voltammograms showed a well defined oxidations peak for BHT at potentials approximately. 200 mV lower than the poorly defined peck obtained in the absence of the electocatalyst. A 35%, methanol :water medium, a modifier concentrations of 2%, and pH 2 were chosen as working conditions. Results obtained suggest that the oxidation signal arisen as a result of BHT chemically reducing Ni(II)to Ni(I) in the phthalocyanine, and the subsequent electrochemical oxidations of the latter. Using differential pulse voltammetry at ΔE =50 mV, a linear calibration range was obtained between 1 and 50 mg L−1 BHT with a detection limit of 0.17 mg L−1 BHT interferences from other substances commonly present in commercial antioxidant mixtures were tested. The developed method was applied to the determinations of BHT in stabilized diethyl ether.