bluuebunny/crossref_metadata_2025_split huggingface dataset:
Theory of ultramicroelectrodes
Authors: Aoki Koichi 
Published: May 2005

AbstractThis review describes the theory of mass transport at ultramicroelectrodes that have broken through several experimental limitations of electrochemical measurements. On the basis of the mathematical miniaturization, the ultramicroelectrode can be classified into a point electrode, a line electrode, and a plane electrode. Electrochemical features of these electrodes are described from a viewpoint of the mass transport, especially due to diffusion. Theoretical difficulty in ultramicroelectrodes is mainly due to nonuniform current distribution on the electrode surface. The expression for the time‐dependent diffusion‐controlled current at any electrode geometry, which predicts the current responding to any potential variation, is presented. Conditions of the steady‐state current are specified. The diffusional characteristic functions at a disk. a cylinder, and a band are presented, from which the theories of various electrochemical techniques can be derived analytically. Voltammetric peak currents at several ultramicroelectrodes are compared in light of the diffusional edge effect. The properties of the steady‐state current are described at a disk, a band array, a ring, and a recess electrode. The theory is extended to the current‐potential curves complicated by the heterogeneous kinetics at a disk, a cylinder, and a band‐array electrode.
Software development for improving the application of static semimicroelectrodes in voltammetric quantitative analysis of oligocomponent samples
Authors: Mesáaroš ŠTefan , Bustin Dušan 
Published: May 2005

AbstractA computer procedure is proposed to improve the application of the nonsteady‐state voltammogram at a semimicroelectrode in quantitative analysis of oligocomponent samples. The technique is based upon the optimized order differentiation. The proposed computer routine offers the optimation of the differentiation order as well as accomplishment of the differentiation itself. The mutual independence of the analytical signal‐‐a prerequisite of quantitative application of semimicroelectrode voltammetry– was tested with a mixture of o‐dianizidine and 4‐amino‐4′‐methoxy diphenylamine. Pt‐disk (ø = 40 μm) and Pt‐fiber (ø = 40 μm, 15 mm in length) semimicroelectrodes were applied for the testing.
Postchromatographic electrochemical detection of carbohydrates at a silver oxide electrode
Authors: Tougas Terrence P. , Debenedetto Mark J. , Demott James M. 
Published: May 2005

AbstractSilver electrodes, when conditioned at sufficiently positive potentials in the presence of a strong base, can be made to form a silver(I) oxide or silver(II) oxide surface. In the presence of this oxide surface, carbohydrates may be oxidized and quantitated by means of an electrocatalytic scheme. The current which flows to reoxidize the charge‐transfer mediator (silver oxide) is directly related to concentration of carbohydrate. Rectilinear response is obtained over at least two decades of concentration (104 M to 10−6 M). Design of a prototype electrochemical cell and studies of optimum cell conditions are discussed. The application of a high‐performance liquid chromatography (HPLC) detector for the separation of some common sugars is illustrated.
Elimination of zinc/copper intermetallic interference in the determination of zinc in wastewaters and seawater by potentiometric stripping analysis
Authors: Scollary Geoffrey R. , Cardwell Terence J. , Cattrall Robert W. , Nan Chen Guo , Vicente‐Beckett Victoria A. , Hamilton Ian C. , Roden Steve 
Published: May 2005

AbstractA new approach to the elimination of Zn/Cu intermetallic interference in the determination of zinc by potentiometric stripping analysis is described. The method is based on the use of several enrichment/ stripping cycles, with each cycle using an enrichment time of 10 seconds or less and the stripping signal from each cycle being added to give the total stripping signal. The additive method compares favorably with the traditional “third element” approach based on the use of gallium, and it is demonstrated that, for an industrial sample containing oil and grease, the additive method has significant advantages over the gallium method. The advantages of potentiometric stripping analysis in monitoring zinc in industrial wastes and the applicability of the technique to zinc speciation studies are described.
Application of glassy carbon substrated cyanide‐sensitive electrodes in determination of cyanide and mercaptan levels of wastewater
Authors: Stankovic Slavka M. , Jovanović Momir S. , Jovanović Vladislava M. , Djikanović Milka 
Published: May 2005

AbstractQuantities of free and complex cyanides and mercaptans were determined in wastewater. Levels of free and complex cyanides were determined after previous oxidation of mercaptans by hydrogen peroxide. The procedure used for cyanide determination relied on applying a laboratory‐made glassy carbon (GC) substrated melt‐coated Agl “cyanide‐sensitive” electrode. The level of mercaptans was determined by iodometric titration in bicarbonate solution. Iodine was coulometrically generated using the depolarization end point detection on a GC/saturated calomel electrode indicating a couple connected directly to the recorder.
Differential electrolytic potentiometric determination of caffeine in nonaqueous media
Authors: Abdennabi Abdalla M. S. , Sultan Salah M. 
Published: May 2005

AbstractThe application of direct current differential electrolytic potentiometry (dc DEP) to the titration of caffeine in acetic anhydride‐toluene mixture has been investigated. A very stable low current source has been constructed to polarize the antimony electrodes. The behavior of these electrodes during the titration of caffeine has been examined. Caffeine in commercial samples like tea, Pepsi as a beverage and Prontopyrin, a proprietary drug, was extracted in chloroform and determined by dc DEP.
Chronocoulometric interrogations of oxidase‐based enzyme electrodes for enhanced selectivity
Authors: Higson S. P. J. , Vadgama P. M. , Ward J. P. 
Published: May 2005

AbstractClassical oxidase‐based enzyme electrodes rely on the amperometric determination of H2O2. Such electrodes are vulnerable to electroactive interferants found in biological solutions. Some interferants may be oxidized at anodic potentials, necessitating the use of permselective barrier membranes. Two generic chronocoulometric approaches to the interrogation of oxidase‐based enzyme electrodes have been developed. Both the chronocoulometric interrogation of H2O2 and the chronocoulometric interrogation of the reduction of O2 (formed from the anodic oxidation of H2O2) have allowed new correlations to be made with 0 to 20 mM glucose concentrations. Furthermore, the inter rogation of O2 has allowed a glucose sensor to be constructed that is virtually free from the effects of electroactive interferants.
Voltammetric investigations of the effect of triton X‐100 on copper processes in the presence of oxygen
Authors: Krznarić Damir , Plavšić Marta , Ćosović Božena 
Published: May 2005

AbstractThe influence of Triton X‐100 (T‐X‐100) on the redox processes of copper in NaCl solutions and in the presence of oxygen was investigated by anodic stripping alternating current voltammetry (ASacV), anodic stripping direct current voltammetry (ASdcV), and differential pulse anodic stripping voltammetry (DPASV). In the presence of oxygen, copper dissolution from amalgam is characterized by a catalytic process, resulting in a net cathodic current due to the oxidation of Cu(I) to Cu(II) by H2O2 formed on the electrode, and the subsequent reduction of Cu(II) back to Cu (I). Triton X‐100 blocks the catalytic process by hindering the formation of H2O2, by competing with CuCl and Cl− for the adsorption sites on HMDE surface, and by blocking the formation of Cu(I) and Cu(II) hydroxide deposit on the surface. Its presence also changes the redox processes of copper from reversible to quasireversible. At the same time, T‐X‐100 increases the oxidation current of copper, probably through disproportionation of Cu(I) to Cu(0) and Cu(II). This last effect was observed regardless of whether oxygen was present in the solutions or not.
Potentiometric ion‐pair titrations of metal ions forming complexes with 1,10‐phenanthroline and its derivatives
Authors: Vytřas Karel , Varmužová Ilona 
Published: May 2005

AbstractSimple coated‐wire electrodes, prepared using an ordinary aluminum wire conductor covered with the plasticized poly(vinyl chloride) membrane, were used in potentiometric titrations of metal ions forming complexes with 1,10‐phenanthroline and its derivatives. The method precipitation of ion pairs formed by metal phenanthroline complexes and tetraphenylborate. Titractions were accompanied with titration curves yielding very sharp potential breaks, so that very reproducible results could be taken even in titrations of quite diluted solutions (down to 2.5 × 10−7 mol of the metal ion in the 25 cm3 of the sample titrated). Using the procedure described the following cations were titratable in forms of their 1.10‐phenanthroline complexes: Zn2+, Cd2+, Mn2+, Fe2+, Fe3+, Co2+, Ni2+, Cu2+, Vo2+, Ga3−, In3−, and Tl3−. Some of the metal ion solutions, prepared from the salts of analytical‐reagent‐grade purity, can be recommended for use in standardization procedures of the sodium tetraphenylborate titrant. 2.9‐Dimethyl‐1,10‐phenanthroline complexes of Zn2+, Cd2+, and Cu+ were also titrable, but the results were significantly erroneous. Metal 4,7‐diphenyl‐1,10‐phenathroline complexes were insoluble in water as well as in water/ethanol mixtures.
Fast‐pulsed amperometric detection at electrodes: A study of oxide formation and dissolution at platinum in 0.1 M NaOH
Authors: Roberts Richard E. , Johnson Dennis C. 
Published: May 2005

AbstractResults of a potential‐step chronocoulometric study of oxide formation at a Pt‐rotated minidisk electrode (0.00785 cm2) indicate that the anodic charge (qa) grows ca. as a linear function of the log time (t) for t = ca. 2–30 ms. Furthermore, the slope of the linear qa – log (t/ms) plot is proportional to the applied overpotential for oxide formation. The anodic peak current observed during linear potential‐scan voltammetric experiments is nearly a linear function of scan rate (ϕ) for small ϕ (1000 < mV s−1) but shows substantial negative deviation from linearity for ϕ > 1000 mV s−1. The peak potential for oxide formation shifts in a positive direction for increasing values of ϕ, suggesting that this process is kinetically slow relative to large ϕ values. Reverse potential‐step chronocoulometric measurements demonstrate that the background current in so‐called “reverse‐pulsed amperometric detection (RPAD)” can be decreased by inhibiting the conversion of the hydrous oxide (PtOH) to the inert oxide (PtO). Data also indicate that the rate of cathodic dissolution of surface oxide is dependent on applied potential for t < 2 to 30 ms. Oxide reduction continues even for t > 1000 ms.
Design and evaluation of photoelectrochemical flow cells
Authors: Barisci J. N. , Wallace G. G. 
Published: May 2005

AbstractSeveral photoelectrochemical flow cells have been designed and their analytical performances evaluated and compared. Two cell geometries, thin‐layer and wall‐jet, and three irradiation configurations differing in the relative position of the irradiation and detection points have been considered. In the first configuration (“adjacent”), the irradiation point is located upstream of the working electrode. In the second arrangement (“above”), the light irradiates the solution above the working electrode as well as the electrode surface. The third configuration (“on”) involves the use of an optically transparent electrode through which the light passes before irradiating the solution present on the electrode surface. The “adjacent” thin‐layer cell was found to be the most practical and useful design. The photoelectrochemical efficiency of this cell was optimized and evaluated in terms of window and channel size.
Studies on electrochemical reactions at metal‐oxide electrodes for combination with high‐performance liquid chromatography
Authors: Stitz Alfred , Buchberger Wolfgang 
Published: May 2005

AbstractVarious electrodes, such as nickel, copper, and cobalt metal electrodes and nickel‐, copper‐, and cobalt‐modified glassy‐carbon electrodes, are investigated for the oxidative amperometric detection of alcohols, polyols, and carbohydrates after separation by high‐performance liquid chromatography (HPLC). These electrode materials are compared with respect to stability, detection limits, and an eventual necessity of electrode surface pretreatment. Detection limits of 4 ng and 10 ng glucose injected can be achieved using a metallic copper electrode and a metallic nickel electrode, respectively. Investigations at the surface of a nickel electrode reveal the existence of a reversible layer of nickel oxide with higher valence which is formed in an alkaline medium at an applied potential of at least 400 mV versus Ag/AgCl/KCl(sat). Its thickness strongly depends on electrochemical pretreatment procedures. This layer can be converted into a layer of lower valence nickel oxide either electrochemically or chemically. Investigations of the electrode surface are carried out by in situ ultraviolet‐visible (UV‐vis) reflectance spectroscopy and by Fourier‐transform infrared spectroscopy (FTIR). Controlled‐potential experiments at various metal‐oxide electrodes and separation of the oxidation products on ion‐exchange columns reveal some of the reaction mechanisms for the oxidation of alcohols, polyols, carbohydrates, and similar organic compounds.
Voltammetric determination of piroxicam after incorporation within carbon pastes
Authors: Paniagua Ana Rosa , Vázquez Maria Dolores , Tascón Maria Luz , Sánchez‐Batanero Pedro 
Published: May 2005

AbstractAn accurate voltammetric method for the piroxicam determination at solid state, with a detection limit of 0.47 mg/g, is described. The method is based on the incorporation and oxidation of piroxicam within a carbon paste matrix bound with a nonconducting solvent. The method was successfully applied to the analysis of several pharmaceutical formulations.
Polarographic behavior of the β‐lactam antibiotic Cefuroxime and study of the reduction mechanism in acidic media
Authors: Bernacca Giuliana , Nucci Lamberto , Pergola Francesco 
Published: May 2005

AbstractPolarographic behavior of the cephalosporin Cefuroxime (CFXN) in aqueous solutions of PH ranging from 1 to 10 was investigated. The reactant is strongly adsorbed in acidic media, while in neutral and alkaline solution, electrode reaction is not affected by adsorption phenomena. A kinetic study of the methoxyimino group electroreduction to methanol and an aminic derivative in acidic media was carried out. The overall electrode process is controlled by the heterogeneous protonation step preceded by a fast electronation step in the pH range 1 to 3, whereas for 3 < pH < 5, the rate determining step (rds) is the first electronation step. Moreover, a fast protonation precedes the rds in the whole acidic medium. The best experimental conditions for the detection of CFXM in differential pulse plarography (DPP)were found. Owing to its high adsorptivity, CFXM is detectable at a concentration as low as 1 × 10−8 M at a pH of about 2.
Liquid chromatography/electrochemical detection of hydroxylamines by oxidation at a cobalt phthalocyanine chemically modified electrode
Authors: Qi Xiaohe , Baldwin Richard P. 
Published: May 2005

AbstractChemically modified electrodes (CMEs) containing a polymeric cosating of cobalt phthalocyanine (CoPC) were shown to catalyze the electrooxidation of hydroxylamine (NH2OH) and its N‐mono‐, N,N‐di‐, and O‐substituted derivatives. All of these compounds were oxidized at unmodified glassy carbon electrodes only at potentials higher than +1 V (vs. Ag/AgCl) but gave substantial anodic currents between +0.25 and +0.55 V at the CoPC‐coniaining surface. On the basis of exhaustive electrolysis experiments, the number of electrons transferred for the oxidations was found to vary between 1.2 and 1.6 depending on the particular hydroxylamine compound and the specific condition, of the electrolysis; and the products included oximes, azoxy compounds, and dimeric species. These observations were consistent with an electrocatalytic mechanism involving oxidation of the hydroxylamine by electrogenerated Co(III)PC and subsequent reaction of the initially formed oxidatior products by several pathways. When the CoPC CME was used as the sensor in amperometric detection following liquid chromatography, the detection limits obtained at +0.55 V ranged from 0.4 pmol for hydroxylamine itself up to 40 pmol for N,O‐dimethylhydroxylamine. By maintaining the applied potential at +0.20 V, the detection could be made selective for hydroxylamine and N‐mono‐substituted hydroxylamine compounds only.
Partial characterization in vitro of glucose oxidase‐modified poly(phenylenediamine)‐coated electrodes for neurochemical analysis in vivo
Authors: Lowry John P. , O'Neill Robert D. 
Published: May 2005

AbstractGlucose oxidase (GOx) modified poly‐phenylenediamine (PPD) coated 250 μm Pt‐disk electrodes were prepared by electropolymerization in phenylenediamine solutions containing GOx. Bothorthoandmetamonomers were tested, and theorthoisomer was found to give better glucose responses. The response of Pt/o‐PPD/GOx electrodes to glucose was well behaved with a rapid response time and displaying Michaelis‐Menten kinetics. The behavior of these electrodes in vitro to ascorbic acid (a principal interferant in brain tissue) was complex in that the sensitivity was concentration dependent. At low ascorbate concentrations (<50 μM), the sensitivity was similar to that of bare Pt (72 ± 13 nA/ mM, n = 10) whereas at higher levels it decreased sharply to 0.2 ± 0.1 nA/mM (n = 3) at 1 mmol/L ascorbate. At still higher concentrations (1 to 10 mmol/L), the sensitivity was concentration independent, 0.14 ± 0.02 nA/mM (n = 3). Calibrations for another potential interferant, uric acid, were linear in the range studied (0 to 100 μM) with a slope of 0.41 ± 0.03 nA/mM (n = 3), indicating negligible interference by this substrate for concentrations present in brain extracellular fluid. Surprisingly, the permeability of both substrates was greater in PPD films containing no GOx. The results are discussed in terms of the suitability of these electrodes for monitoring brain glucosein vivo.
The electrochemical processes of copper in the presence of triton X‐100
Authors: Plavšić Marta , Krznarić Damir , Ćosović Božena 
Published: May 2005

AbstractIn this work, the redox processes of copper ions were studied by electrochemical methods in NaCl and NaClO4solutions in the absence or in the presence of nonionic surfactant Triton X‐100 (T‐X‐100). The enhancement of the anodic peak current of copper in the presence of T‐X‐100 in sodium chloride solutions was observed depending on the Concentrations of T‐X‐100 and copper (II) ions. This is the consequence of destabilization of the otherwise stabile CuClcomplex in chloride solutions by the presence of T‐X‐100. The process involves disproportionation of formed copper (I) species to copper (0) and copper (II).
Contribution to the electrochemical behavior study of piroxicam in different aqueous‐orgarnic media and electrodes by using polarographic and voltammetric techniques
Authors: González Mercedes , Vázquez Maria Dolores , Tascón Maria Luz , Sánchez‐Batanero Pedro 
Published: May 2005

AbstractA study of the electrochemical behavior of piroxicam has been carried out by dc polarography, classical and differential pulse mode voltammetric techniques, as well as by classical and differential pulse mode adsorptive cathodic stripping voltammetry (AdCSV), in methanol/H2O(20/80% v/v) and acetonitrile/H2O(20/80%‐6 v/v) media. Several parameters, such as pH, temperature, scan rate, ad‐accumulation potential, and accumulation time, elucidate the piroxicam reduction mechanism and establish analytical methods, mainly by AdCSV, obtaining a detection limit of 2.4 × 10−11 M.
Electronic configurations in potentiostats for the correction of ohmic losses
Authors: Souto Ricardo M. 
Published: May 2005

AbstractRecent trends in the design of potentiostats capable of correcting for ohmic losses occurring in electrochemical cells are reviewed. The various effects of ohmic drop occurrence and their influence on diverse electroanalytical techniques are considered, as well as potentiostat configurations and stability, with emphasis in the three‐electrode cell configuration. Electronic correction methods are discussed according to the following classifications: (1) positive feedback, (2) negative impedance, (3) current pulse, (4) analogic subtraction, and (5) current interruption.
Enzyme chronopotentiometry
Authors: Uhe B. , Schuhmann W. , Janker G. , Schmidt H.‐L. , Janata J. 
Published: May 2005

AbstractChronopotentiometry (CP) with enzyme electrodes is a new approach to overcome inherent problems of steady‐state potentiometric processes. The developed procedure is presented on the example of a glucose oxidase (GOD) electrode. Electrochemically generated mediator helps to overcome traditional difficulties arising from poorly defined mixed potentials in the presence of oxygen during an analysis. Transition times are automatically evaluated by using computerized calculation programs. The technique can be used for determining substrate concentrations; moreover, it is particularly promising as an effective tool to study electrode processes with biochemical systems on an electrode surface.
Differential pulse voltammetric determination of lead(II) with benzoin oxime‐modified carbon paste electrodes
Authors: Tuzhi Peng , Zhe Tang , Guoshun Wang , Baoen Shen 
Published: May 2005

AbstractA new chemically modified electrode (CME) for determining lead(II) with high sensitivity and selectivity is reported. The electrode is constructed by adding benzoin oxime into a carbon paste mixture. The lead(II) is accumulated on the electrode surface by the formation of the complex in an open circuit, and then the resulting surface is characterized by medium exchange, potential reduction, and differential pulse anodic stripping voltammetry. In 10 deposition/measurement/regeneration cycles with a single surface, the response could be reproduced with 5.7% relative standard deviation. Quantitation of lead(II) from the peak current of the anodic wave for a 10 minute deposition time gives a detection limit of 8 × 10−9 M (1.6 ppb). Linear calibration plots are obtained for lead(II) concentrations ranging from 10−7 to 10−8 M. The modified electrode preferentially accumulates lead from the solution, while most of the metal ions do not interfere with the determination. The mechanism of the accumulation of lead on the benzoin oxime‐modified electrode has been explored. Application to the determination of lead in wastewater is illustrated.
Observed redox interferences of poly(pyrrole)‐based perchlorate‐selective electrodes
Authors: Hulanicki Adam , Michalska Agata , Lewenstam Andrzej 
Published: May 2005

AbstractThe responses of the poly(pyrrole)‐based ion‐selective perchlorate electrode were investigated in both perchlorate and redox buffers media. Sensitivity of tested electrodes both to the changes of perchlorate on concentrations and redox potential of the solution were observed. Slopes were characteristic −51.3 mV/dec in the case of perchlorate ion solutions and 61 mV/dec in the case of redox calibration. Potentiometric redox sensitivity of the tested poly(pyrrole) layers was observed in presence of 1 M sodium perchlorate. Potentiometric redox sensitivity of the bare platinum electrode and perchlorate‐sensitive electrode based on poly(pyrrole) in presence of 0.1 M NaClO4 were compared.