bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polishable composite electrode based upon graphite powder modified with an electrochemically deposited catalyst
Authors: Cox James A , Lewinski Krzysztof 
Published: May 2005

AbstractA polishable bulk‐modified electrode is described that contains polymeric‐mixed valent ruthenium oxide with cyano cross‐links (mvRuCN) as a catalyst. Because mvRuCN is not available as an isolated compound, it was electropolymerized on graphite powder that was subsequently formed into a conducting composite with epoxy. Except for promoting oxidations at a more positive potential, this composite behaved the same as mvRuCN films on glassy carbon. Electrocatalytic oxidation of various N‐nitrosamines, As(III), glutathione, isotocin, and myoglobin was observed. Flow‐injection analysis of 50 μM N‐nitrosodi‐n‐propylamine with amperometric detection at the bulk‐modified composite electrode yielded currents of 2.5 ± 0.1 μA (5 trials) when the carrier solution is pH 1.5 phosphate buffer. The use of a micellar carrier,pH 1.5 phosphate buffer in 0.01 M hexadecyltrimethylammonium chloride, decreased the sensitivity of the flow‐injection amperometric determination of N‐nitrosodi‐n‐phenylamine by 50%, but otherwise, the behavior of the electrode was unchanged. The major advantages of the bulk‐modified electrode over the surface‐modified electrode jras the long‐term stability (at least several months with dry storage) and polishability. Regarding trie latter, 19 replicates of the oxidation of As(III) yielded a relative standard deviation (RSD) of the current response of 3% when the surface was polished between each trial.
Electrochemical study of pyrazolone derivatives at the liquid/liquid interface
Authors: Wang Erkang , Wang Hanming , Yu Zemu 
Published: May 2005

AbstractPyrazolone derivatives, such as antipyrine, aminopyrine, and 4‐aminoantipyrine, can transfer across the water/nitrobenzene interface to produce a pair of well‐defined symmetric, reversible anodic‐cathodic peaks by cyclic voltammetry. The transfer mechanism has been studied as a result of the formation of complex of related pyrazolone derivatives with a proton. The protonated complex formed then transferred across the water/nitrobenzene interface. The effect of drugs' structure on the transfer behavior was discussed and parameters related to interfacial behavior were determined.
Electrochemical behavior of triazolobenzodiazepine derivatives
Authors: Arenaza Jesús , Gallo Blanca , Vicente Francisca , Dominguez Manuel 
Published: May 2005

AbstractThe electrochemical behavior of two novel triazolobenzodiazepines (adinazolam and U43.465F) has been studied in the pH range 3 to 13.5. Both compounds are reduced on the dropping mercury electrode and yield one reduction wave attributed to the azomethine group. The two‐electron transfer is polarographically reversible. However, the transfer is followed by a fast conversion of the elearolysis product by a chemical reaction with an irreversible global process. A weak adsorption of the reactant has been observed under certain conditions. Quantitative analysis has been performed, showing that adinazolam and U43,465F can be determined up to 1.1 × 10−6M using differential pulse polarography.
Liquid chromatography series dual‐electrode amperometric detection for aromatic nitro compounds
Authors: Lin Yuehe , Zhang Rongkun 
Published: May 2005

AbstractA new design of dual‐electrode electrochemical detector for liquid chromatography is described utilizing two series generator/detector electrodes. The detector developed is based on the larger electrode area design compared with commercial ones and has higher electrolytic efficiency, which lead to a higher detection sensitivity when in a reductive‐oxidative series detection mode. Analytes are first reduced at the upstream electrode and the reaction products are then detected by oxidation at the downstream electrode. So, the influence of dissolved oxygen and trace amounts of heavy metals in the mobile phase and sample is eliminated. Thus, exhaustive removal of dissolved oxygen before analysis is not required, and the method can be easily automated. The technique is tested on seven aromatic nitro compounds. Under the optimized conditions, the assay is linear in a concentration range of 2.0 × 10−7 to 4.0 × 10−5 g/mL and has low detection limits of 1.0 to 2.0 ng using a 10 μL sample. The largest standard deviation was 5.2%. The recovery of the detection of water samples was 93 to 107%.
Reproducible, reliable and rugged Hg‐plated Ir‐based microelectrode for in situ measurements in natural waters
Authors: Tercier M.‐L. , Parthasarathy N. , Bufle J. 
Published: May 2005

AbstractConstruction of a reproducible, reliable and rugged iridium‐based microelectrode is described. Perfect electrical contact, Ir‐glass sealing and Ir disk morphology are the key points for obtaining reproducible voltammetric sensors. These points are discussed in detail and optimal fabrication conditions are given. Electron bombardment under vacuum yielded good soldering between Ir and Cu electrical cable. Reproducible polishing of the microelectrode to a mirror like Ir disk surface is obtained with silicon carbide pads and diamond paste using an automatic home made polisher. Cyclic voltammetry and optical microscopy have been used to characterize this microelectrode. Hgplated Ir‐based microelectrodes are prepared by electrodeposition of mercury on the iridium disk substrate. Reproducibility and reliability close to 100% have been obtained for Ir‐based microelectrode preparation, mercury layer deposition and trace metal measurements by differential pulse anodic stripping voltammetry (DPASV) and square wave anodic stripping voltammetry (SWASV) in synthetic solutions even at low ionic strength (10−3 M). Continuous measurements over long periods of time indicate that the Hg‐plated Ir‐based microelectrodes can be used for several days without renewal of the mercury layer. These microelectrodes were applied to lead and cadmium speciation studies directly in river waters by SWASV without any separation. The results show that free PbII and CdII concentrations as low as 0.5 nM and 0.1 nM respectively can be determined by direct measurements, without perturbing the medium. The lifetime of these microelectrodes in the present state of the art is more than 2 years.
Methylene‐green‐mediated carbon paste glucose biosensor
Authors: Kulys J. , Wang L. , Hansen H. E. , Buch‐Rasmussen T. , Wang J. , Ozsoz M. 
Published: May 2005

AbstractAn amperometric glucose bioelectrode based on the incorporation of methylene green (MG) within a glucose oxidase (GOD)‐containing carbon paste is described. The electrode generates an anodic current in the range of 0.0–0.6 V (vs. SCE). The optimum pH is 8.5. The apparent Michaelis constant for the Cali bration plot is 49.3 mM (at 0.5% MG and 5.0% GOD loadings). The electrode sensitivity is 18.1 μA/mM cm2. The electrode is insensitive to paracetamol and ethanol. At 0.068 V the response to ascorbic acid (40 μM) accounts for 2.4% of that of the normal physiological glucose level in blood. The performance was optimized by systematically altering the electrode composition and electrode potential. The electrode was used to measure glucose in a serum sample and gave an acceptable correlation with the reference method Eksan‐G results. Good stability was observed for storage in the dry state in the refrigerator.
Polarographic and electrochemical studies of some aromatic nitro compounds: Part VIII. Effects of solvents and surfactants on current–voltage curves obtained with DC and differential pulse polarography
Authors: Zuman P. , Rupp E. 
Published: May 2005

AbstractDifferential pulse polarography (DPP) is an excellent analytical method, but cannot be recommended for applications in the initial stages of mechanistic studies. Its application is also questionable in the analysis of samples containing varying concentrations of an organic cosolvent or of surface active compounds. The effect on limiting currents obtained by DC polarography and on peak currents obtained by DPP was demonstrated for reductions of various nitrobenzene derivatives. The similarity of changes in current for various nitrobenzenes enables the exclusion of the formation of adducts or micelles as the predominant effect. The decrease of the limiting currents in all cases is much smaller than the decrease of DPP peak currents, due to strong effects of the surfactants on the kinetics of electroreduction. For the analysis of natural products or of solutions containing varying amounts of organic cosolvent, the measurement of the DC polarographic limiting current is preferred. An addition of 30% ethanol minimizes the effects of the varying concentration of surfactant on both DC polarographic limiting and DPP peak currents.
Electrocatalytic oxidation of reduced nicotinamide coenzymes at organic dye‐modified electrodes
Authors: Chi Q. , Dong S. 
Published: May 2005

AbstractChemically modified electrodes (CMEs) were prepared by adsorbing different dyes, including methylene blue (MB), toluidine blue (TB) and brilliant cresyl blue (BCB), onto glassy carbon electrodes (GCE) with anodic pretreatment. The electrochemical reactions of adsorbed dyes are fairly reversible at low coverages. The CMEs are more stable in acid solutions than in alkaline ones, which is mainly due to decomposition of the dyes in the latter media. They exhibit an excellent catalytic ability for the oxidation of nicotinamide coenzymes (NADH and NADPH). The formation of a charge transfer complex between the coenzyme and the adsorbed mediator has been demonstrated using a rotating disk electrode. The charge transfer complex decomposition is a slow step in the overall electrode reaction process. Some kinetic parameters are estimated. Dependence of the electrocatalytic activity of the CMEs on the solution pH is discussed.
An amperometric study of the reactions of copper(I) and copper(II) oxides with barium peroxide in surfactant suspensions
Authors: Franklin T. C. , Nnodimele R. A. , Bui T. 
Published: May 2005

AbstractA study was made of the amperometric titration of the reaction between barium peroxide and copper(I) and copper(II) oxides. It was shown that it was possible to titrate a solid with a solid in surfactant suspensions. The studies were made in aqueous and acetonitrile suspensions containing cationic surfactants. End points were obtained at molecular ratios of BaO2 to CuO of 1 : 1, 1 : 3, and 1 : 5; and molecular ratios of BaO2 to Cu2O of 1 : 1 and 2: 1. It was postulated that the reactions involving CuO were

The reactions involving Cu2O were postulated to be

.
Application of dual‐pulse staircase voltammetry for simultaneous determination of glucose and fructose
Authors: Fung Y.‐S. , Mo S.‐Y. 
Published: May 2005

AbstractA new electroanalytical method, DPSV, employing dual pulses (0.7V and −0.8V) prior to anodic scan (using staircase voltammetry) is developed for simultaneous determination of glucose and fructose. The electrochemistry of both sugars was studied prior to optimizing the operational parameters. The linear ranges were found to be 0.01–2.0 mM for both sugars, precisions (mean = 0.10 mM and n = 8) 1.8% and 2.4% and detection limits (estimated by 3 times the standard deviation) 0.001 and 0.003 mM for glucose and fructose, respectively. To establish the reliability of the method, various food additives were tested and found to give no interference effect under normal concentrations. HPLC method was carried out in parallel with the method for analyzing food, drink and honey samples. No statistically significant difference in the results was obtained for methods.
Electrocatalytic oxidation of hydroquinone on a polypyrrole‐coated glassy carbon electrode
Authors: Vijayan M. , Krishnan V. 
Published: May 2005

AbstractThe electrochemical behavior of hydroquinone (H2Q) in 1 M H2SO4 on a polypyrrole‐coated glassy carbon electrode (PPy/GCE) has been studied using cyclic voltammetry. Hydroquinone undergoes oxidation at a lower anodic potential on a PPy/GCE compared to a bare GCE. Hydroquinone is oxidized catalytically on a PPy/GCE, and this has been found to be a diffusion‐controlled 2e− process. The effects of film formation potential, film thickness, and dopant anions on the catalytic behavior with respect to hydroquinone oxidation on a PPy/GCE are also discussed.
A study of riboflavin determination by square wave adsorptive stripping voltammetry on mercury film electrodes
Authors: Economou Anastasios , Fielden Peter R. 
Published: May 2005

AbstractIn this work riboflavin was determined by square wave adsorptive stripping voltammetry (SWASV): riboflavin was initially adsorbed on a mercury film electrode (MFE) at a potential of 0.0 V (vs. Ag/AgCl) and at pH 12; the subsequent reductive stripping step was carried out by applying a square wave potential‐time waveform on the electrode. Both a batch method (based on the rotating disk electrode configuration) and a flow approach [based on the wall‐jet flow‐through electrode and flow injection analysis (FIA)] were employed. Both instrumental and chemical parameters were investigated and optimized for analytical use of the technique. The limit of detection was 0.5 nmol L −1 (for 10 min of preconcentration), the precision was 8% for the batch system (at the 10 nmol L−1 level) and 6% for the flow system (at the 100 nmol L−1 level); the linear range depended on the preconcentration time and the mass transfer conditions during the accumulation step. Both methods were automated and applied to the determination of riboflavin in commercial pharmaceutical products with recovery values at over 90%.
Polarographic behavior and determination of oxamniquine in dosage forms
Authors: Belal F. , Aly F. A. 
Published: May 2005

AbstractA highly sensitive method is described for the determination of oxamniquine in its pure form and in capsules. The proposed method depends upon the polarographic activity of oxamniquine in Britton–Robinson buffer, whereby a well‐defined cathodic wave, followed by a more negative ill‐defined one, was produced over the whole pH range. The first wave was characterized as being irreversible and diffusion‐controlled with limited absorption properties. The current–concentration relationship was found to be rectilinear over the ranges 1 × 10−5 to 5 × 10−4 and 1 × 10−6 to 5 × 10 −4 M in the direct current (DCT) and differential pulse polarography (DPP) modes, respectively, with a minimum detectability of 1 × 10−7 M. The number of electrons involved in the reduction process was established through coulometric measurement at an applied potential. The mechanism of the electrode reaction was verified and confirmed through chemical reactions of the electrolyzed solution. The proposed method was successfully applied to the determination of oxamniquine in capsules, and the results obtained were in accordance with those found using the United States Pharmacopeia (USP) XXII method.
Electrochemical behavior of 2‐ and 8‐quinolinethiol complexes with cobalt and nickel and their catalytic hydrogen evolution
Authors: Paneli Miropi G. , Voulgaropoulos Anastasios N. 
Published: May 2005

Abstract2‐ and 8‐quinolinethiols catalyze hydrogen evolution at −1.500 V and −1.380 V vs. Ag/AgCl, respectively. The more positive potential for hydrogen evolution in the case of the latter is a result of its more acidic character. The addition of cobalt shifts the potential overvoltage for hydrogen evolution to more positive potentials in the presence of 2‐quinolinethiol, i.e., 1.400 V vs. Ag/AgCl; while in the presence of 8‐ quinolinethiol a significant increase in height of the hydrogen wave at −1.380V vs. Ag/AgCl is observed. In the former case, hydrogen evolution follows reduction of the CoII‐2‐quinolinethio1 complex, and for higher cobalt concentrations the wave splits into two Brdicka's peaks. In the latter case, reduction of the CoII‐2‐quinolinethiol complex takes place at the same potential as the hydrogen wave and, as a result, only one peak is observed; this peak can be used for the determination of cobalt with a detection limit of 0.50 nM and a relative standard deviation (RSD) of 3.8%.
Acetylcholinesterase‐based amperometric sensor
Authors: Stoytcheva Margarita 
Published: May 2005

AbstractAn amperometric sensor has been created using the hydrolysis of acetylthiocholine iodide, which is catalyzed by the acetylcholinesterase enzyme and generates an electroactive product. An electrochemically modified graphite electrode is used, with acetylcholinesterase covalently bonded directly to its surface. The characteristics of the sensor, such as the response time, repeatability, reproducibility, stability, dynamic range, activation energy, and temperature coefficient of the current are evaluated. The optimum working conditions (pH, temperature, and rotation speed) are established.
Complexation of lead with humic matter by stripping voltammetry. Prevention of adsorption on Nafion‐coated mercury film electrode
Authors: Capelo Sofia , Mota Ana M. , Gonçalves Maria L. S. 
Published: May 2005

AbstractThe complexation of humic matter with lead in natural water conditions was studied by differential pulse anodic stripping voltammetry (DPASV) using a mercury film of a Nafion‐coated mercury film as the working electrode. The results clearly show that the Nafion film greatly minimizes the adsorption of humics on the electrode. Besides adsorption, other effects on the voltammetic signal are discussed, such as the degree of lability, ligand heterogeneity, and the metal‐to‐ligand concentration ratio at the electrode surface.
Polarographic determination of diethyldithiocarbamate using kinetic and catalytic processes
Authors: Spataru Nicolae , Calusaru Aurelian 
Published: May 2005

AbstractDiethyldithiocarbamate (Et2DTC) is not polarographically reducible, but in complex combination with cobalt two prewaves are formed in ammonia buffer. These prewaves are due to catalytic cobalt and hydrogen discharge and they are useful for analytical purposes in the determination of Et2DTC with high sensitivity (2 × 10−6−1 × 104 M). The effects of CoII, ammonium hydroxide, and ammonium chloride concentrations on the catalytic waves are described. A mechanism for the formation of the prewaves is proposed, in which adsorption plays a prominent part. Suitable conditions for analytical applications are described.
Determination of orthochlorophenol by stripping voltammetry
Authors: Manisankar P. , Prabu H. Gurumallesh 
Published: May 2005

AbstractThe present work reports on a differential pulse and square wave stripping voltammetric procedure for the determination of orthochlorophenol. The best conditions included using 0.1 M KOH solution, an accumulation potential of 0.4 V vs. Ag/AgCl electrode, a square wave amplitude of 60mV, a frequency of 50 Hz, a step potential of 4mV, and an initial scan potential of −1.0 V. Under these conditions, determination limits of ng/ml were achieved at a stationary glassy carbon electrode.
Fast voltammetric sensors for the measurement of soil water activity
Authors: Huang Huiliang , Dasgupta Purnendu K. 
Published: May 2005

AbstractSmall inexpensive soil water sensors and the necessary electronics package for fast voltammetry (l04 V/s scan rate) are described. The sensor consists of a blunt ended hypodermic needle cathode containing a concentric PTFE insulating tube and therein, a Pt‐wire anode. The sensing film is formed by dip‐coating a 1:7 blend of a perfluorosulfonate and a polyestersulfonate polymer at the tip of the needle. Atop this sensing film is a composite protective film of cellulose acetate and nylon that inhibits the passage of ionic or low MW constituents and allows the transport of water. The sensor is sheathed in a PTFE tube that protrudes beyond the sensor tip and the protrusion gap is filled with a paste of talc and BaSO4 which serves as a water conduit between the soil and the sensor proper. The sensor is capable of making reliable moisture measurements between the wilting point and the field capacity of the soil sample; the response behavior consists of the combination of two nearly linear segments, the sensor output increasing steeply between the wilting point and ca. 60% of the field capacity and then much more gradually to the field capacity. The sensors have been field tested. No effect on sensor performance is observed even after burial under soil for several months.
Detection of surface activity by voltammetric measurements
Authors: Komorsky‐Lovrić Šebojka , Lovrić Milivoj , Branica Marko 
Published: May 2005

AbstractInfluences of a nonionic detergent Triton X‐100 on square‐wave voltammetry and anodic stripping square‐wave voltammetry of Cd2+ in 0.5 M NaClO4 + 0.01 M HClO4 are measured at precisely controlled durations of adsorptive accumulation and surfactant concentrations. Diagnostic criteria for the presence of surface‐active substances in electrolytes are reported. A voltammetric method for the quantitative analysis of detergents is proposed. An ionic type of detergent can be recognized by the variation of the accumulation potential.
Electrochemical behavior of metallothioneins and related molecules. Part II: Lys–Cys–Thr–Cys–Cys–Ala thionein fragment [56–61] MT I in the presence of cadmium and/or zinc
Authors: Muñoz Amalia , Rodriguez Adela Rosa 
Published: May 2005

AbstractAn electrochemical study, using differential pulse polarography (DPP), of a peptide Lys–Cys–Thr–Cys–Cys–Ala Thionein Fragment [56–61] MT I (FT) was performed in order to compare the behavior of metallothioneins and that of this less complex molecule, intrinsic to the metallothionein structure. The influence of different parameters, such as the solution pH and the concentration of metal elements, cadmium and zinc was investigated. Two different electrochemical systems were distinguished: in the first one, the mercury electrode itself is involved in the charge transfer steps; in this case, peaks are attributed to the oxidation of the mercury electrode in the presence of the peptide acting as a chelating agent. The second electrochemical system corresponds to the reduction of metal cations, cadmium and zinc, at a dropping mercury electrode either as free ions or complexed by the peptide. The apparent stability constants for complexes of FT with cadmium, zinc and mercury were estimated. The order of affinity is: K′HgFT ≫ K′CdFT > K′ZnFT. The DPP response can be used for elucidation of the chemical forms of compounds (speciation).
A tubular graphite‐epoxy electrode incorporating horseradish peroxidase as a potentiometric sensor for hydrogen peroxide
Authors: Zulfikar  , Hibbert D. Brynn , Alexander Peter W. 
Published: May 2005

AbstractA novel potentiometric peroxidase enzyme sensor based on a tubular graphite‐epoxy design is reported for the determination of hydrogen peroxide in an FIA system. The sensor was formed from horseradish peroxidase (40 mg), graphite (240 mg) and epoxy (780 mg). Hydrogen peroxide, injected into pH 7,0.05 M phosphate buffer at 26°C, was determined with a linear slope of 45.6 mV/decade in the concentration range 7.5 × 10−7 to 5.0 × 10−5 M. Acceptable reproducibility of 1.2% relative standard deviation was obtained in the flow injection analysis. The advantages of this sensor are low cost, simple electronic circuit design and better selectivity than amperometric sensors and a detection limit comparable with other methods.