bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of a chronocoulometric method for the determination of uranium at trace levels by using the catalytic nitrate reduction
Authors: Cantagallo Maria Inês C. , Bertotti Mauro , G. R. Gutz Ivano 
Published: May 2005

AbstractThe electroanalytical determination of uranium at trace levels was studied with the purpose of improving the sensitivity of the uranium‐catalyzed reduction in the presence of nitrate on mercury electrode. Examination of the current dependence on time (chronoamperometry) revealed the advantage of measuring the current later and for a longer time interval than usual in pulse polarography. The uranium/nitrate system is particularly favorable in this sense because an intensification of the catalytic current with time is observed. The best signal‐to‐noise ratio was achieved using the technique of chronocoulometry. In this chronocoulometric catalytic determination (CCCD), analytical information was gathered, calculating the slope of the charge versus time curve during the period of 10 to 20 seconds after the application of the potential pulse and correcting it for the residual slope before the pulse. To establish the new analytical procedure, the effects of electrolyte composition, potential program, integration time, and blank correction were examined. A detection limit of 3 × 10−10 M was attained, a power of ten lower than the sensitivity reported for the same catalytic determination by differential pulse polarography. An exploratory study of the combination of this procedure with preconcentration of uranium on the electrode allowed reduction of the detection limit by an additional order of magnitude.
Electrochemical quantification of phenol using mushroom tyrosinase: Determination of the kinetic parameters of the enzyme
Authors: Rivas Gustavo A. , Solis Velia M. 
Published: May 2005

AbstractThis article presents a sensitive electroanalytical method for the determination of phenol in the presence of mushroom tyrosinase as well as a simple methodology to evaluate the kinetic parameters of this enzyme. The quantification is performed at low potential from the oxidation current of pyrocatechol that is formed by the action of mushroom tyrosinase in air‐saturated solutions. Any electrochemically activated glassy carbon electrode is used. The course of the reaction is followed by cyclic voltammetry. A linear relationship holds up to 9.0 × 10−5 M, a detection limit is 4.6 × 10−7 M with a precision of 3.2% and a correlation coefficient of 0.997. Kinetic parameters evaluated from the same experiments are Vmax = 0.005 μmol of pyrocatechol produced per minute and KM = 2.0 × 10–4 M.
Sensors based on carbon paste in electrochemical analysis: A review with particular emphasis on the period 1990–1993
Authors: Kalcher K. , Kauffmann J.‐M. , Wang J. , Švancara I. , Vytřas K. , Neuhold C. , Yang Z. 
Published: May 2005

AbstractA review is presented dealing with the use of carbon paste as an electrode maaterial for electrochemical sensors (311 references). It covers mainly publications which appeared during the period 1990–1993; numerous applications demonstrate the widespread applicability of carbon paste in the field of electrochemical analysis, such as voltammetry, amperometry, and potentiometry, but also as an electrode for electrochemical detectors in flow systems.
Carbon paste electrodes modified with enzymes, tissues, and cells
Authors: Gorton L. 
Published: May 2005

AbstractA review is presented dealing with the use of carbon paste amperometric electrodes for electroanalytical purposes, with either the surface or the bulk being modified with biologically derived material such as enzymes, tissues, and cells. It covers virtually all the publications which have appeared from the very first enzyme‐modified carbon paste electrode up to early 1994 and includes 220 references.
Surface‐modified gold electrodes for electrocatalytic oxidation of NADH based on the immobilization of phenoxazine and phenothiazine derivatives on self‐assembled monolayers
Authors: Schlereth D. D. , Katz E. , Schmidt H.‐L. 
Published: May 2005

AbstractSelf‐assembled monolayers of cystamine and cysteine chemisorbed on gold electrode surfaces have been used as a support for covalent immobilization of some phenoxazine and phenothiazine derivatives. The covalent attachment was achieved after previous functionalization of the free amino groups on the electrode surface with bifunctional reagents (terephthaloyl chloride and 1,6‐hexamethylene diisocyanate) able to react with the imino form of the amino group in position 3 of the phenoxazine and phenothiazine derivatives.In every case, a shift of the redox potentials between 130 and 180 mV towards more positive potentials, as well as an increase in the peak‐topeak separation between anodic and cathodic peaks was observed after covalent attachment. The surface coverages (10−11 < Γ < 10−10 mol/cm2) obtained from the cyclic voltammograms were those for a not densely packed monolayer and varied depending on the redox compound immobilized. The surface‐modified electrodes obtained were afterwards used for the electrocatalytic oxidation of NADH.UV‐vis spectroscopy was used to monitor the successive steps of surface modification using gold semitransparent electrodes. The total surface coverage of redox mediator on the electrode surface could also be calculated from the optical difference spectra between the oxidized and the reduced state obtained ‘in situ’ in a spectroelectrochemical cell.
A flexible biosensor for glucose
Authors: Mitsubayashi K. , Dicks J. M. , Yokoyama K. , Takeuchi T. , Tamiya E. , Karube I. 
Published: May 2005

AbstractA flexible glucose biosensor was constructed by immobilizing glucose oxidase within a gold‐coated, hydrophilic polytetrafluoroethylene membrane. All reagents and materials used were harmless and nontoxic. Enzyme immobilization was improved using a mesh mask during gold deposition, the grid pattern permitting better access into the membrane. The masked sensors had greatly improved output currents and linearity. The sensor was linear up to 662 mgL−1, the range covering the concentrations encountered in normal and diabetic human tear fluids. The current was proportional to the square of the electrode area, hence an electrode of known dimensions can be used without precalibration. Sterilization using 80% ethanol had a negligible effect on its response. The sensor is well suited to the detection of glucose or other analytes in body fluids, such as tears, airway mucus, sweat, and saliva.
Nitrate detection at Nafion‐modified electrodes incorporating ytterbium and uranyl electrocatalysts
Authors: Ugo P. , Moretto L. M. , Ballarin B. 
Published: May 2005

AbstractThe performances of Nafion‐coated thin mercury film electrodes and Nafion‐coated glassy carbon electrodes loaded in aqueous solutions of Yb3+ or UO, respectively, are examined in relation to their use for the electrocatalytic voltammetric detection of nitrate.Electrocatalytic reaction between the incorporated, reduced species, namely Yb2+ and U3+, and the NO, substrate is observed in both cases; however, the rapid inactivation of the ytterbium‐based sensor prevents its use for practical purposes. More promising results were obtained for the uranyl‐based sensor, since a more stable, modified electrode is obtained which can be used for the detection of nitrate in the 2–400 μM concentration range; however, problems connected to the slow release of the catalyst from the coating remain to be solved. Finally, the limitations and possible development of such a voltammetric sensor are critically discussed.
Adsorptive stripping voltammetry of palladium(II) with thioridazine in situ modified carbon paste electrodes
Authors: Raber G. , Kalcher K. , Neuhold C. G. , Talaber C. , Kölbl G. 
Published: May 2005

AbstractA method is described for the voltammetric determination of palladium(II) using a carbon paste electrode modified with thioridazine. The modifier was added to the analyte solution and adsorbed onto the electrode surface under closed circuit conditions. Palladium could be preconcentrated onto the electrode surface and determined by differential pulse voltammetry without medium exchange. The dependence between the current response and the concentration of palladium(II) was linear within a range of 1 to 450 μg L−1 with preconcentration times between 0 and 120 seconds. The influence of parameters such as modifier concentration and pH‐value on the determination of palladium were investigated. The applicability of this method for the voltammetric determination of palladium in fresh water and in catalysts used for synthetic organic reactions is demonstrated.
Electrochemical response of poly(vinylferrocenium)‐coated Pt electrods to some anions in aqueous media
Authors: Gülce H. , Özyörük H. , Yildiz A. 
Published: May 2005

AbstractThe electrooxidation behavior of iodide, thiocyanate, and cyanide on poly(vinylferrocenium)‐coated Pt electrodes was investigated using cyclic voltammetry and differential pulse anodic stripping voltammetry. IR and UV spectroscopic data, and differential scanning calorimetry (DSC) measurements indicated that these anions were incorporated in the polymeric structure as a result of anion exchange. Anodic stripping of these anions from the film was carried out after the initial preconcentration. Cyanide uptake was found to cause an irreversible change in the physical properties of the film, whereas thiocyanate and iodide are merely incorporated in the film structure as counter ions.
Enzyme‐modified microelectrodes for in vivo neurochemical measurements
Authors: Pantano Paul , Kuhr Werner G. 
Published: May 2005

AbstractVarious approaches to the production of miniaturized chemical sensors for in vivo applications are reviewed with special regard to the measurement of chemical transients in the mammalian brain. The basic tenants of biosensor principles are discussed in terms of the temporal response of enzyme‐modified electrodes and selection of redox enzymes. The effects of electron transfer mediators and differential measurements to gain selectivity are also examined. A broad range of immobilization methods including membrane entrapment, physical and chemical adsorption, cross‐linking agents, polymeric entrainment, electropolymerized films and covalent derivatization are examined. The use of polymer layers and redox polymers to gain selectivity are discussed. The discussion is limited to microelectrode surfaces (< 100 μm diameter) and various electrode types are examined, including bare and platinized carbon fibers, platinum microelectrodes, conducting organic salts and carbon paste electrodes.
The application of various immobilized crown ether platinum‐modified electrodes as potentiometric and amperometric detectors for flow injection analyses of catechol and catecholamines
Authors: Lunstord Suzanne K. , Ma Yi‐Long , Galal Ahmed , Striley Cynthia , Zimmer Hans , Mark Harry B. 
Published: May 2005

AbstractDifferent crown ethers were electrochemically polymerized or adsorbed onto a platinum electrode for the analysis of catechols by either static potentiometric, potentiometric FIA or amperometric FIA. The static potentiometric responses of all the crown ether modified electrodes were linear over about three decades of catechol concentration (10−5−10−8 M). The potentiometric FIA response of all the crown ether modified electrodes exhibited linear responses over four decades of catechol concentration (10−2−10−6 M). The amperometric FIA responses were linear over a 10−2−10−5 M range. Comparing the different techniques; static potentiometric, potentiometric FIA, and amperometric FIA, all had markedly different response slopes for the different crown ethers. Overall, the crown ether modified electrodes, except for an open‐crown ether, displayed excellent response stability for successive injections in both FIA modes. The lowest detection limits were about 0.5 × 10−6 M for the potentiometric FIA with minimal interference from ascorbic acid, uric acid and acetaminophen. For amperometric FIA the detection limits were about 0.5 × 10−5 M, but for ascorbic acid, uric acid, and acetaminophen the interference was significant. Experimental parameters which influence the mechanism of the potentiometric response are discussed.
Electroreduction mechanism of some sugars on mercury
Authors: Pezzatini Giovanni , Wei He , Innocenti Massimo , Guidelli Rolando 
Published: May 2005

AbstractThe electroreduction mechanism on mercury of the aldoses glucose and galactose, the ketoses fructose and tagatose, and the disaccharides lactose and lactulose was investigated in neutral and weakly alkaline solutions. Measurements at different temperatures ranging from 0 to 45°C indicate that the chemical reaction of the hemiacetal ring opening, which controls the polarographic limiting current, proceeds mainly in the adsorbed state below room temperature and in the nonadsorbed state above room temperature. Along the rising portion of the polarographic wave the electrode process is under the mixed control of the chemical reaction of ring opening and of a subsequent electrochemical step involving the uptake of the first transferring electron, with no protonation step in between.
A flow‐injection/XPS investigation of the effect of redox equilibria on the selectivity of an iodide‐selective electrode
Authors: Davey David E. , Mulcahy Dennis E. , O'Connell Gregory R. , Smart Roger StC. 
Published: May 2005

AbstractFlow‐injection selectivity coefficients for a solid‐state iodide‐selective electrode were determined for three moderately interfering species—bromide, thiocyanate and thiosulfate–by injecting mixed iodide–interferent solutions into selected reagent streams. The use of neutral and acidified iodate and bromate oxidant streams was found to increase the selectivity of the iodide electrode towards the three interferents. The acidified streams also visibly modified the surface of the electrode membrane, although the resultant coating, ascribed to the formation of elemental sulfur and iodine, was easily removed by manual polishing with slurried alumina and a lint‐free cloth. X‐ray photoelectron spectroscopy (XPS) performed on pressed AgI/Ag2S pellets following immersion in the acidified iodate and bromate solutions revealed substantial surface modification, with the formation of AgIO3 and AgBr, respectively. Use of ascorbic acid or metabisulfite reducing streams resulted in higher selectivity towards iodide than that obtained using either of the neutral oxidant streams, but less than that obtained in the presence of a simple nitrate reagent stream. In contrast, the use of a thiosulfate stream irreparably damaged the surface of the electrode to the point where subsequent flow‐injection experiments showed excessive peak broadening and very poor baseline recovery. XPS studies performed on the damaged membrane revealed a surface dominated by hydroxides and almost totally devoid of either AgI or Ag2S.
A new indicator electrode for oxygen sensors
Authors: Nei Lembit 
Published: May 2005

AbstractThe electrochemical reduction of O2 was studied at Ni‐Cu alloy electrodes in aqueous alkaline solution (0.1–6.0 M KOH) and in unbuffered neutral solution (0.1–2.0 M KCl) using the rotating disk electrode technique. Voltammetric measurements showed that the overall O2 reduction process at the electrodes containing 70–90% Cu is transport‐limited at cathodic potentials, and that they can be used as indicator electrodes for galvanic‐type oxygen sensors. An industrially produced Ni‐Cu alloy “melhior”, which contains ∼ 30% Ni, was also studied, and this alloy proved to be an excellent O2 reduction catalyst. Melhior electrodes were utilized as indicator electrodes for oxygen sensors, and showed high output current stability and a long lifetime (exceeding one year).
Amperometric flow‐injection determination of citric acid in food using free citrate lyase and co‐immobilized oxalacetate decarboxylase and pyruvate oxidase
Authors: Matsumoto Kiyoshi , Tsukatani Tadayuki , Okajima Yuko 
Published: May 2005

AbstractA flow‐injection analytical system for the determination of citrate in food has been developed. Citrate lyase, oxalacetate decarboxylase, and pyruvate oxidase were used, and the latter two enzymes were co‐immobilized. Hydrogen peroxide, which was produced by three enzyme reactions, was monitored amperometrically with a platinum electrode. The carrier solution used was 0.1 M phosphate buffer (pH 7.0) containing 10 mM MgCl2, 80μM thiamine pyrophosphate (TPP), and 10μM flavine adenine dinucleotide (FAD). The detection limit was 0.02mM, and the range of determination was 0.1‐1.0 mM. The relative standard deviation was 1.23% for 10 successive determinations at the 0.5 mM level. The determination frequency was about 15 tests per hour. The present system was applied to the determination of citrate in several fruits. The results showed good agreement with those obtained using a conventional method (F‐kit method).
Stabilized bilayer lipid membranes for flow‐through experiments
Authors: Nikolelis Dimitrios P. , Siontorou Christina G. , Andreou Vangelis G. , Krull Ulrich J. 
Published: May 2005

AbstractThis work reports a technique for the stabilization of solventless bilayer lipid membranes (BLMs), and the use of stabilized BLMS as flow detectors. Microporous filters composed of glass fibers, polytetrafluoroethylene (PTFE) and polycarbonate (nominal pore sizes from 1 to 5 μM) can serve as interfaces that separate two solution compartments. The micropores in the filter media can act as supports for formation and stabilization of BLMs. One of the solution compartments is used to cast lipid films on the filters, while a carrier electrolyte solution concurrently flows through the opposing compartment. Optimization of the flow cell design, and the chemical composition and methods for preparation of stabilized BLMs, are described. Lipid membranes composed of mixtures of phosphatidyl choline and phosphatidic acid could respond rapidly to pH alterations of the carrier electrolyte solution. Signals would reproducibly appear within a few seconds following the injection of an electrolyte of different pH than the carrier. Signals took the form of a single ion current transient with magnitude of tens of picoamperes (pA) and a duration of seconds. The mechanism of signal generation is explored by differential scanning calorimetry. The results show that a phase transition within a lipid membrane can be triggered by pH alterations of the electrolyte solution. Stabilized BLMs which provide artificial ion gating events hold prospects for chemical sensing of process streams.
Amperometric gas‐diffusion/enzyme electrode
Authors: Iliev Ilia , Kaisheva Anastassia , Scheller Frieder , Pfeiffer Dorothea 
Published: May 2005

AbstractAn amperometric enzyme gas‐diffusion electrode has been developed which combines a porous, air breathing gas‐diffusion electrode with an enzyme [glucose oxidase (GOD)] immobilized with Nation into its porous catalytic layer. The catalytic layer contains pyrolyzed Co‐ tetramethoxyphenylporphyrine (CoTMPP), which is very active towards the electrochemical oxidation of H2O2. The behavior of this electrode was investigated when the oxygen needed for the enzymatic reaction was supplied from the air (in the gas phase) through the porous structure of the gas‐diffusion electrode. It was shown that in the presence of the substrate (glucose), the amperometric signal obtained in this mode of operation was much higher than that obtained when only the oxygen dissolved in the electrolyte was involved in the enzymatic reaction. The developed enzyme gas‐diffusion electrode allows a versatile and rapid change in the O2 concentration in the zone where the enzymatic reaction is taking place. This electrode can be used as a model system for the investigation of the influence of O2 on the performance of both the peroxide or the mediated enzyme electrodes in an effort to develop oxygen independent biosensors.
Tubular band microelectrode. I. Design and electrochemical behavior
Authors: Corti Horacio R. , Goldfurb Darío L. , Ortiz Martin Scalabrini , Magallanes Jorge F. 
Published: May 2005

AbstractThe effect of supporting electrolyte concentration and sample flow rate on the electrochemical behavior of a tubular band microelectrode was studied and compared to the results obtained by simulation. The conditions for the current to be independent of the hydrodynamic flow rate are established. The experimental results are compared to those obtained by digital simulation based on the explicit hopscotch method. These calculated results are also compared to those obtained for microband and infinite planar geometries. It was concluded that this microelectrode very rapidly reaches a stationary state, providing a stable and fast response to concentration changes in the solution, as is required for analytical purposes.
The behavior of polypyrrole doped with different anions as an ion‐selective electrode
Authors: Jovanović Vladislava M. , Markičević Ljiljana , Stanković Slavka , Stanković Rade , Jovanović Momir S. 
Published: May 2005

AbstractPolypyrrole (PPy) films were electrochemically deposited on glassy carbon from aqueous solutions of different sodium salts (F−, Cl−, NO, HSO). Methods applied were potentiostatic polymerization or cyclic voltammetry. The electrochemical behavior of such electrodes was studied by cyclic voltammetry. The results obtained show that the reaction is localized at the electrode surface for polypyrrole doped with CI− and NO, anions and diffusion‐controlled for F− anions. The polypyrrole films, examined as ion‐selective electrodes in solutions of anions corresponding to the dopant ones, exhibit lower or higher deviation from the Nernstian response depending on the dopant. When polypyrrole doped with HSO was tested, a cationic response was obtained. The chemical exchange process of dopant anion was studied. The results show that this process depends on the nature of the dopant anion and the anion from the solution.
Ion exchanged polypyrrole‐based glucose biosensor: Enhanced loading and response
Authors: Ramanathan Kumaran , Sundaresan N. S. , Malhotra Bansi D. 
Published: May 2005

AbstractEnhanced loading of glucose oxidase in polypyrrole films via manipulation of the polymer morphology is reported. The exchange of bulky anions such asp‐toluene sulfonate and ferricyanide present as dopant ions in polypyrrole, with chloride ion in solution leads to greater porosity and resultant maximization of glucose oxidase (GOx) immobilization in polypyrrole. The polypyrrole–Gox electrode thus prepared exhibits improved performance as an amperometric glucose sensor. The fractal dimension estimated from chronoamperometric data demonstrate the increased dimensionality of the polypyrrole network after ion exchange.
Electroanalysis with interdigitated array microelectrodes
Authors: Niwa Osamu 
Published: May 2005

AbstractThis review discusses electroanalysis with interdigitated array (IDA) microelectrodes. The basic electrochemical properties of IDAs are presented along with a calculation of diffusion‐controlled current and an example of generation collection voltammetry to clarify the advantages of IDA for electroanalysis. The fabrication procedures of metal and novel carbon based IDAs are also summarized because the fabrication of very small IDAs is advantageous for electroanalysis. Previously reported electroanalytical applications of IDAs are overviewed. Among them are the measurement of redox electron conduction and molecular diffusion in various films, various types of enzyme sensors and electrochemical switches, an example of highly sensitive and selective generation collection voltammetry, a new stripping analysis using self‐induced redox cycling and the detectors for flow cells and liquid chromatography.