bluuebunny/crossref_metadata_2025_split huggingface dataset:
Behavior of cathodically pretreated platinum on Fe(CN) electroreduction in KNO3: Dependence on pretreatment
Authors: Pillai K. Chandrasekara , Thangamuthu Rangasamy , Ilangovan Govindasamy 
Published: May 2005

AbstractPlatinum electrode, cathodically pretreated by polarizing it in the hydrogen evolution region, has been studied in detail for its electrode activity towards Fe(CN) electroreduction in 1 M KNO3. HClO4 acid has been used to cathodically pretreat the Pt electrode in order to avoid specific adsorption effect of anions, so that the intrinsic electrochemical activity of cathodically pretreated Pt electrode is assessed. Similar studies have been carried out with anodically pretreated and heat treated electrodes. Cyclic voltammetry (CV) and rotating disk electrode techniques (RDE) have been used to evaluate kinetic parameters and the results indicate that the adsorbed H‐adatoms on Pt surface retard Fe (CN) reduction by two orders. This has been explained in terms of a double layer effect and enhanced adsorption of the impurities by adsorbed H‐adatoms on the surface. Effect of potential cycling as a pretreatment method has also been examined.
From polarography of DNA to microanalysis with nucleic acid‐modified electrodes
Authors: Paleček Emil 
Published: May 2005

AbstractNucleic acids are electroactive species producing well developed voltammetric peaks on the mercury electrode sensitively reflecting small damages to the double‐helical DNA. Nucleic acid‐modified electrodes can easily be prepared by immersing the electrode into a 5 μL drop of the DNA and/or RNA solution. Such nucleic acid‐modified electrodes strongly decrease the quantities of DNA and RNA required for analysis. They offer a number of other advantages which may be of use in biochemical and molecular biological research. Past, present and future aspects of nucleic acid voltammetric analysis are reviewed.
Electrochecmical biosensors for DNA sequence detection
Authors: Mikkelsen Susan R. 
Published: May 2005

AbstractA review of reported biosensors for the sequence‐selective detection of analyte DNA sequences shows that signal transduction based on electrogenerated chemiluminescence, potentiometry and voltammetry are all capable of detecting analyte DNA at attomole levels. In contrast, optical and piezoelectric transducers detect DNA at picomole and femtomole levels, respectively. The principles and applications of these promising electrochemical DNA biosensors are described and discussed.
Studies of electroreduction of nitropentane and nitrohexane on mercury electrodes in the presence of adsorbed aliphatic alcohols
Authors: Xuan Hai Trinh , Maksymiuk Krzysztof , Stroka Jadwiga , Galus Zbigniew 
Published: May 2005

AbstractElectroreduction of 1‐nitropentane and 1‐nitrohexane was studied on mercury electrodes in aqueous solutions, together with the inhibitors: n‐pentanol, n‐hexanol and n‐heptanol. The electrode behavior of these species was not found to be influenced by inhibitors at concentrations lower than 10 mM and 2 mM for n‐pentanol and n‐hexanol, respectively, because adsorption of nitrocompounds is stronger than that of alcohols. For high alcohol concentrations, when a total surface coverage by inhibitor molecules is almost achieved, the reaction of nitroalkanes is inhibited. Steric factors evaluated using the dependence of rate constant on inhibitor concentration were used in the determination of the orientation of reactant molecule on the electrode. For alcohol concentrations near saturation, the rate constant becomes independent of inhibitor concentration. In this case a reaction of nitroalkanes dissolved in the surface organic phase was postulated.
Cathodic stripping voltammetry of D‐penicillamine and N‐acetylcysteine in the presence of nickel ion
Authors: Ion Ana , Bǎnicǎ Florinel G. , Fogg Arnold G. , Kozlowski Henryk 
Published: May 2005

AbstractD‐Penicillamine (Pen) can be preconcentrated on a hanging mercury drop electrode in the presence of NiII (0.5 mM) at potentials between 0.0 and −0.4V vs. Ag/AgCl, (3 M KCl). Pen is adsorbed either as the mercury thiolate or as the NiII Pen complex. Accumulation as the nickel complex occurs at the more negative potentials in this range, i.e., near −0.4V, where mercury thiolate is not formed. When the mercury thiolate has been accumulated and mercury ion is reduced during the scan, Pen is released to form the nickel(II) complex. This overall accumulation behavior is typical of thiol compounds that form strong chelate complexes with NiII.Pen in the adsorbed state catalyzes the reduction of NiII giving a differential pulse cathodic stripping voltammetric peak at −0.6V (pH 7). Pen can be determined at concentrations down to 15 nM. N‐Acetylcysteine (Ac‐CysH) which has no catalytic properties for the reduction of NiII, can be determined at pH 7 in phosphate‐acetate buffer, using the reduction peak of its accumulated mercury thiolate salt. The mutual interferences of Pen and Ac‐CysH are negligible.
An electrochemical and spectrophotometric study of some charge‐transfer complexes involving drug molecules in acetonitrile
Authors: Ball Rowena V. , Eckert George M. , Gutmann Felix , Wong Danny K. Y. 
Published: May 2005

AbstractThe electron donating properties of the drugs, amiodarone, desethylamiodarone, promethazine and codeine have been studied using the electrochemical technique of conductivity titration, complemented by electronic absorption spectroscopy. All were found to form charge transfer complexes in vitro with the electron acceptor iodine in acetonitrile. A quantitative explanation has been proposed to account for the observed temperature dependence of the conductivity. This is based on consideration of the opposing effects of charge mobility and the temperature‐dependent donor‐acceptor equilibrium. An assessment of the use of the hydrochloride form, instead of free base, of drugs in examining the model systems for the study of drug donor‐acceptor interactions is also presented.
Method for determination of gold in solutions with high oxidation/reduction potential
Authors: Viltchinskaia Elena A. , Zeigman Lev L. 
Published: May 2005

AbstractThis article proposes a method for detecting the concentration of gold ions in solutions with high oxidation/reduction potential (ORP), such as aqua regia, a hypochlorite‐iodine mixture, and a new proprietary liquid bromine carrier solution, by direct current anodic stripping voltammetry (DCASV). The working electrode is a graphite electrode impregnated with a mixture of epoxy resin and polyethylene amine. The article discusses: possible cause of a double stripping peak for gold appearing in voltammograms in aqua regia solution with electrolysis potentials less than −0.4 V; differences in coefficients of the working electrode's sensitivity in the above mentioned solutions. A relative standard deviation of the results in determining gold concentration in solutions of rock (ORP > 0.9 V), which were obtained by the proposed method and by atomic‐absorption spectrophotometry, did not exceed 0.2.
Preparation and characterization of Ag‐intercalated copper hexacyanoferrate films on electrodes
Authors: Malik Marcin A. , Kulesza Pawel J. 
Published: May 2005

AbstractWe demonstrate the possibility of preparation of a mixed metal hexacyanoferrate system, silver‐containing copper hexacyanoferrate, in the form of a thin film on glassy carbon electrode substrate. This novel microstructure is characterized using conventional cyclic voltammetry, visible absorption spectrophotometry, as well as solid‐state electrochemistry in the absence of contact with liquid electrolyte. The results imply distinct physicochemical identity of the system in comparison to silver‐free copper hexacyanoferrate. Incorporation of Ag influences the selectivity of counter‐cation transport which supports redox reactions of the modified electrode in alkali metal supporting electrolytes. Thus the Ag‐intercalated material may be considered for ion‐exchange applications. Following in situ electroanalytical determinations, based on coulometry and stripping‐like voltammetry, we postulate stoichiometries, AgICuIIFeIII(CN)6 and KAgICuIIFeIII(CN)6, for the oxidized and reduced structures.
A model for a redox species confined to a thin layer with a variable diffusion coefficient
Authors: Cassidy John , McCormac Timothy 
Published: May 2005

AbstractA numerical simulation has been carried out for a redox couple confined to a thin layer under potential step or cyclic voltammetric conditions where the diffusion coefficient is determined by the relative amounts of the oxidized form (of diffusion coefficient D1)and reduced form (of diffusion coefficient D2). An overall layer diffusion coefficient D is determined by the mole fractions of species 1 and 2; D(n1 +n2)=n1D1 +n2D2. This layer diffusion coefficient is proposed as an alternative model to that of interaction parameters used to characterize nonidealities during potential step and cyclic voltammetric experiments of surface confined redox species.
Applications of self‐assembled monolayers in electroanalytical chemistry
Authors: Mandler Daniel , Turyan Iva 
Published: May 2005

AbstractThe different approaches in which self‐assembled monolayers (SAMs) have been applied in electroanalytical chemistry are reviewed. Three principal concepts have been used and can be categorized according to the mechanism of attachment of the monolayer to the electrode. These include the formation of covalent bonds between reactive organic molecules, such as chlorosilanes, with activated surfaces, the formation of lipid and bilayer lipid membranes that self‐assemble on conductive surfaces and the adsorption of functionalized alkanes, e.g., alkanethiols, on well ordered surfaces. Systems for detecting inorganic, organic and biological species are described and conclusions are drawn.
Alternating current investigations at the mercury drop electrode on the adsorption potential of metal complexes
Authors: Sander Sylvia , Henze Günter 
Published: May 2005

AbstractIn adsorptive stripping voltammetry (AdSV) the analyte is accumulated on the electrode surface in the form of a metal complex and the determination step is carried out voltammetrically. Usually the technique is sensitive to the effects of other absorbable organic substances. Alternating‐current (AC) investigations on the complexes of uranium, vanadium and antimony with chloranilic acid, uranium with cupferron and cobalt and nickel with dimethylglyoxime gave information about their adsorption behavior on the electrode surface. Furthermore the AC voltammetric behavior of the nonionic surfactant Triton X100 was shown. By knowing the adsorption potential and range of adsorption, predictions about the effects of organic adsorbates can be made. Importantly the optimal accumulation potential of the complex for its AdSV‐determination may be obtained. With appropriate potential control the selective accumulation of the analyte complex can be achieved and so avoid the influence of these other adsorbates in favorable cases.
The catalytic polarographic prewave of nickel(II) induced by 2‐methylbenzimidazole
Authors: Calzón Josefa García , Ordieres Arturo J. Miranda , Alvarez Jesús L. MuňÍz , Fonseca Juan M. López 
Published: May 2005

AbstractA comprehensive study of the prewave of NiII induced by 2‐methylbenzimidazole in sodium barbital/nitric acid/potassium sulfate media was carried out by using various polarographic techniques in order to establish the mechanism via which the underlying electrode reaction proceeds. Based in the proposed mechanism, the formation of the catalytic complexes is a surface process involving deprotonated 2‐methylbenzimidazole; the adsorption of this compound over the catalyst concentration where the prewaves are well‐defined conforms to a Langmuir isotherm. Accordingly, a plot of the reciprocal of the limiting current for the prewave against the reciprocal of the ligand‐catalyst concentration is a straight line. This finding was exploited for the determination of 2‐methylbenzimidazole at concentrations from 5 × 10−7 to 5 × 10−5 M from NiII prepeaks recorded by differential pulse polarography and square‐wave voltammetry.
Studies of the preparation and analytical application of polypyrrole‐coated microelectrodes for determination of aluminum
Authors: Barisci Joseph N. , Murray Peta , Small Chris J. , Wallace Gordon G. 
Published: May 2005

AbstractMethods that enable the preparation of cation sensitive polymer‐coated microelectrodes have been developed. The analytical utility of these electrodes has been demonstrated with the detection of aluminum in flowing solutions. Detection limits in the low ppb range have been obtained. The response for several potentially interfering cations was evaluated.
Selectivity of hybrid voltammetric determinations
Authors: Lubuda JÁN , Vaníčková Mária 
Published: May 2005

AbstractThe selectivity of solvent extraction voltammetry and ion‐exchange voltammetry hybrid procedures has been investigated. The equations for the prediction of the selectivity value according to the extraction constants or distribution coefficients of the analyte and interfering component were obtained. Their verification and application at the determination of trace metals in model and real samples are presented.
Anodic stripping voltammetry of tungsten at graphite electrodes
Authors: Malakhova Natalia A. , Popkova Galina N. , Wittmann Gertrud , Kalnichevskaia Liubov N. , Brainina Khjena Z. 
Published: May 2005

AbstractTrace levels of tungsten can be determined at a graphite electrode using anodic stripping voltammetry. Tungsten is concentrated at the electrode surface after reduction to Wv as a insoluble ternary complex in the presence of rhodanide ions and antipyrine (ANT) or 4‐ dimethyl‐aminoantipyrine (pyramidon, PYR). The optimal conditions of this determination are: electrolyte 1 M H2SO4 containing 0.078 M NH4SCN + 0.04M ANT or 0.02M PYR; deposition potential −0.50 V; sweep from −0.4 to −0.05 V using differential pulse stripping technique. Detection limit is 1 × 10−9M (0.2 μg/L) for a 180 s accumulation time (with a relative standard deviation of 15%). Results obtained for waste waters, steel and olive leaves are reported.
Resolution of differential potentiometric stripping analysis
Authors: Garai Tibor , Nagy Zoltan , Mészáros Lajos , Bartalits Liliana , Locatelli Clinio , Fagioli Francesco 
Published: May 2005

AbstractThe resolution of differential potentiometric stripping analysis has been evaluated in terms of the difference in the half‐wave potentials, the number of electrons involved in the electrode reactions and the concentration ratio of the ions to be determined simultaneously. The asymmetry of the dt/dE vs. E function was found to affect the resolution considerably. In other words the interference is considerably enhanced when the half‐wave potential of the interfering ion is more cathodic than that of the measured one while in the reverse case the resolution is much improved.
Preconcentration by flow reversal in conductometric sequential injection analysis of ammonium
Authors: Oms M. T. , Cerdà A. , Cerdà Victor 
Published: May 2005

AbstractA simple sequential injection method for the determination of ammonium with conductometric detection is described. The sample and alkaline solution are sequentially aspirated into a single tubular channel and mixed by flow reversal. The formed ammonia permeates through a gas permeable membrane and is collected on a static acceptor solution. The change in conductance of the acceptor solution is related to the concentration of ammonium ions in the sample. The use of flow reversal and influence of sample residence time on preconcentration are studied. The detection limit can be lowered from 1.5mg L−1 to 0.1 mg L−1 if preconcentration by successive sample flow reversal is used. The relative standard deviation is lower than 3%.
A photo‐cured calcium ion‐selective electrode for use in flow injection potentiometry that tolerates high perchlorate levels
Authors: Dimitrakopoulos Telis , Farrell John R. , Iles Peter J. 
Published: May 2005

AbstractAn improved photo‐cured membrane selective to calcium was developed based on the calcium bis[4‐(l, 1,3,3‐tetramethylbutyl)phenyl] phosphate ionophore and incorporates the lipophilic additive, potassium tetrakis(p‐chloropheny1)borate. The calcium electrode exhibited a hyper‐Nernstian response of 31.0 mV change per activity decade and a log‐linear range between 1 × 10−5 to 0.1 M in pure calcium chloride solution, in steady‐state mode. The calcium electrode was fast responding, reaching 90% of steady‐state value in 5s making it ideal for flow injection measurements. The photo‐cured electrode can measure calcium in a high perchlorate background, and was used to determine the total calcium level in full cream milk that was digested by a nitric/perchloric acid mixture. The results obtained were in good agreement with atomic absorption spectroscopy measurements.
Parameters in the design of oxygen detecting oxidase enzyme electrodes
Authors: Gooding J. Justin , Hall Elizabeth A. H. 
Published: May 2005

AbstractThe response of an amperometric oxidase enzyme electrode, monitored by the consumption of oxygen, was numerically modeled using a two substrate model. The reduction current was found to be sensitive to the thiele modulus, Φ, which is dependent on the square of the biorecognition matrix thickness and the concentration of active enzyme within this matrix. The detectable concentration range to which the sensor can be used can be extended by reducing the membrane thickness or the enzyme loading, both of which reduce the signal change with substrate additions. The dependence of Φ on the square of the membrane thickness makes the sensor design exceedingly sensitive to minor changes in thickness and hence manufacturing of reproducible sensors with common deposition methods exceedingly difficult.
XPS, SEM and electrochemical characterization of a platinum‐based glassy carbon modified electrode. Electrocatalytic oxidation of ethanol in acidic medium
Authors: Casella Innocenzo G. , Desimoni Elio 
Published: May 2005

AbstractA platinum‐based chemically modified glassy carbon electrode (Pt‐CME) was characterized in acidic medium by X‐ray photoelectron spectroscopy, scanning electron microscopy and electrochemical techniques. A uniform distribution of platinum microparticles of different form and size (hexagonal, grain‐like and globular) was present on the surface of glassy carbon. The chemical species present on the electrode surface changed upon polarization. At higher potential values (1.5 V) species such Pt(OH)2, Pt(OH)ads and Pt(OH)4 formed at lower potential values were transformed into PtO, PtOads and PtO2 respectively. A few aspects of the electrooxidation of ethanol in acidic medium were investigated on the Pt‐CME described.
Voltammetry of MnII and CoII in the presence of polymethacrylate
Authors: Cancho Beatriz , Argudo Marco , Ariño Cristina , Esteban Miquel 
Published: May 2005

AbstractComplex formation of MnII and CoII with polymethacrylic acid (PMA) is studied by differential pulse polarography, normal pulse polarography, reverse pulse polarography, cyclic voltammetry and differential pulse anodic stripping voltammetry. Because of the lack of a model for macromolecular metal systems including Mn+/M(Hg) couples with irreversible electrochemical behavior, the application of the theoretical model developed for reversible electrochemical systems is tested to the slow MnII/Mn(Hg) and CoII/Co(Hg) couples. The quality of the experimental results obtained allows us to calculate the formation constants of the predominating MnII/PMA and CoII/PMA complexes and also their dependence on complexation variables.
Electron‐transfer properties of pyrolytic graphite optically transparent electrodes
Authors: Kummer Matthias , Kirchhoff Jon R. 
Published: May 2005

AbstractThe electron‐transfer characteristics of metal mesh optically transparent electrodes, which were modified by chemical vapor deposition of pyrolytic graphite, are investigated. The pyrolytic graphite optically transparent electrodes are found to exhibit sluggish electron‐transfer toward several transition metal probes. Subsequent activation of the electrode surface is accomplished by RF plasma etching of the carbon layer to expose a higher density of edge plane carbon. A limiting current response is achieved after 2.5 min of RF exposure. As a result of the activation process, sharper voltammograms and reduced peak separations are observed in cyclic voltammetric measurements, while reduced equilibration times are found for thin‐layer spectroelectrochemical measurements. [Fe(CN)6],3‐, ferrocene monocarboxylic acid, cobalt(III)sepulchrate {[Co(sep)] 3+} and tris(1, l0‐phenanthroline)cobalt(III){[Co(phen)3]3+} are used to characterize the response of the pyrolytic graphite optically transparent electrodes for electrochemical and spectroelectrochemical measurements.
Pulsed amperometric detection of ethanol in breath by gold electrodes supported on ion exchange membranes (solid polymer electrolytes)
Authors: Schiavon Gilberto , Comisso Nicola , Toniolo Rosanna , Bontempelli Gino 
Published: May 2005

AbstractA sensitive and fast‐responding amperometric sensor for the determination of ethanol in breath which eliminates oxygen interferences is described. It consists of a porous gold working electrode (facing the sample) supported on one face of an ion‐exchange membrane which serves as a solid polymer electrolyte (SPE). The other side of the membrane faces an internal electrolyte solution (1 M aqueous NaOH) containing the counter and reference electrodes. The fouling of the gold working electrode, due to the ethanol oxidation process, is overcome by continuously cleaning and reactivating its surface by applying a triple‐pulse potential waveform. The performance of this sensor has been tested in a closed‐loop flow apparatus fed with synthetic ethanol‐vapor samples obtained by evaporating aqueous solutions with known ethanol contents. The sensor displays a high current sensitivity and a low background noise, so that a low detection limit (2 μg L−1, 1ppm v./v.) is estimated for a signal‐to‐noise ratio of 3. The responses are characterized by both a good reproducibility and a linear dependence on the ethanol concentration over a fairly wide range (more than three orders of magnitude), as well as by a short response time (ca. 1 s). This fast response time arises from the lack of a gas‐permeable membrane and direct gas contact to the triple interphase among the gaseous analyte, the porous working electrode and the solid polymer electrolyte. The absence of significant interfering effects and the possibility of adopting such a device for the detection of ethanol in fermentation processes are also discussed.