bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pulse polarography of azobenzene
Authors: Komorsky‐Lovrić ŠEbojka , Lovrić Milivoj 
Published: May 2005

AbstractPulse polarography is applied to measure adsorption of azobenzene and hydrazobenzene in a wide acidity range between 5 M HClO4 and 0.5 M NaClO4 buffered to pH 7. The solvent is 20% v/v aqueous acetonitrile. In 5 M HClO4 the adsorption of azobenzene is weaker, while at pH 7 it is stronger than the adsorption of hydrazobenzene. In weakly acidic and neutral NaClO4 solutions, the surface protonization of azobenzene is a rate‐determining step of the redox reaction. When the polarographic pulse is very short, the unprotonated azobenzene is reduced directly and at potentials which are more negative than the potentials at which the monoprotonated azobenzene is reduced if pulses are longer. The rate constants of benzidine rearrangement of adsorbed hydrazobenzene are measured in concentrated HClO4 solutions: k = 52 s−1, 115 s−1, and 224 s−1 for 1, 3, and 5 M HClO4, respectively.
Voltammetric investigations on carbon paste electrodes as supports for mercury films
Authors: Švancara Ivan , Pravda Miloslav , Hvizdalová Marie , Vytřas Karel , Kalcher Kurt 
Published: May 2005

AbstractDifferent carbon paste electrodes (CPEs) were investigated for their ability to act directly as supports for mercury films formed “in situ” by electrodeposition. A CPE, containing tricresyl phosphate as a pasting liquid, was found to be especially suitable for this purpose. The mercury film on this support exhibited a more negative potential limit than mercury films deposited onto common carbon pastes or glassy carbon. Thus, the mercury film electrode (MFE) with the tricresyl phosphate‐based carbon paste support proved to be advantageous for differential pulse anodic stripping voltammetry (DPASV) of Zn(II). The effects of various supporting electrolytes, and of the concentration of Hg(Il) ions on the response of zinc, were studied in detail together with an optimization of voltammetric parameters. Interferences from metal ions such as Ni(II), Co(II), Mn(II), and Cu(II), were also investigated. For quantitative evaluations, Zn(II) was accumulated from a 0.1 M ammonia buffer containing 2 × 10−5 M Hg(II), with an accumulation potential of –1.5 V (vs. Ag/AgCl). The current response of Zn(II) was linear for a concentration range from 2 × 10−7 to 2 × 10−5 mol/L with a detection limit of 1 × 10−7 mol/L (accumulation time 180 seconds). The method was applied to the determination of Zn(II) in drinking water and deionized water.
Effect of interference on amperometric glucose biosensors with cellulose acetate membranes
Authors: Vaidya Rajesh , Wilkins Ebtisam 
Published: May 2005

AbstractA new enzyme electrode concept featuring glucose oxidase (GOD) immobilized on fine carbon powder in a fluid state and a cross‐linked GOD enzyme layer has been developed. This enzyme electrode has been tested in vitro at 37°C and has a lifetime of 3 months after which it can be recharged with fresh enzyme. In vitro interference tests carried out on this sensor used with cellulose acetate membranes are described. Sulfur‐free EDTA‐treated cellulose acetate membranes (molecular weight cutoff at 1000) were used, some of which were coated with positively and negatively charged hydrogel layers. The sensors showed a stable and linear response to glucose concentrations >300 mg/dL, in the presence of glucose alone in the phosphate buffer medium and in the presence of interferences. The effects of ascorbic acid, bilirubin, creatinine, L‐cysdne, glycine, uric acid, and urea on the amperometric signal of the sensor were studied. The cellulose acetate membrane coated with the negatively charged hydrogel layer provided good protection for the enzyme electrode, especially in the presence of uric acid, bilirubin, and L‐cystine.
Determination of copper in seawater by adsorptive voltammetry with 1,2‐dihydroxyanthraquinone‐3‐sulfonic acid
Authors: Quentel François , Elleouet Catherine , Madec Christian 
Published: May 2005

AbstractA method is described for the determination of copper in seawater by adsorptive stripping voltammetry after accumulation of a 1,2‐dihydroxyanthraquinone‐3‐sulfonic acid (DASA) complex. The effects of various operational parameters (pH, ligand concentration, potential, and accumulation time) on the reduction current of the adsorbed chelate are discussed. A linear current concentration relationship was observed up to 5 × 10−8 M. The detection limit is 0.3 nM.
Fish Liver Tissue‐Based Membrane Electrode for Uric acid in Serum
Authors: Deng Jiaqi , Wang Qing 
Published: May 2005

AbstractA novel tissue‐based membrane electrode for uric acid in serum is constructed by coupling of fish liver to an oxygen electrode. The oxygen signals decrease with the concentrations of uric acid, and the linear range of the calibration graph is 2.0 × 10−5 to 3.0 × 10−4 mol/L. The biosensor has a lifetime of at least 3 months. Optimum conditions of preparing the sensor and measuring uric acid were explored. Its application in serum was compared with two methods of pure enzyme, and satisfactory results were obtained.
Electrocatalytic activity of cytochrome c for the reduction of nitric oxide
Authors: Miki Koujiro , Ikeda Tokuji , Kinoshita Hideaki 
Published: May 2005

AbstractSodium nitrite in acidic solutions produces a voltammetric cathodic wave starting from −0.5 V (vs. Ag/AgCl) in the presence of a small amount of cytochrome c (cyt c), in which cyt c works as a catalyst for the electroreduction of nitric oxide produced by the disproportionation reaction of nitrite. Hemoglobin (Hb) and myoglobin (Mb) are also effective as catalysts for this type of reaction.
The linear sweep voltametric method: An application to the study of reversible and irreversible processes
Authors: González‐Velasco J. 
Published: May 2005

AbstractThe theory of the linear sweep voltametric method has been the object of a series of articles in which useful solutions for current versus scan rate (I vs. v) relationships and for the diagnostic criteria for different kinds of reacting systems have been found. Some difficulties remain in order to clarify these concepts. This article is an attempt to introduce clearer ideas about how to deduce I vs. v and I vs. E relationships for the method mentioned above as applied to the study of reversible and irreversible electrochemical processes. Some new equations are given which have been deduced under consideration of the numerical solutions obtained by Nicholson and Shain [4]. Variations of Co(O, t) and CR(O, t) with the potential value have been found, and an unambiguous definition of k°′ for irreversible processes is given, which allows the determination of k° values from linear voltammograms recorded in the study of such processes. Also, the values of δN, the thickness of the diffusion layer, have been calculated as a function of the potential and sweep rate.
The oxidation of cyclic diols on a gold elecrode structure‐reactivity relationships
Authors: Luczak Teresa , Holze Rudolf , Beltowska‐Brzezinska Maria 
Published: May 2005

AbstractThe electrooxidation of the three isomeric 1,2‐, 1,3‐, and 1,4‐cyclohexanediols at a gold electrode in contact win an alkaline electrolyte solutior has been studied with cyclic voltammetry. Signficant differences in the electrochemical activity of the isomers were found. The 1,2‐diol is by far the most active one. Its trans‐isomer is more reactive than the cis‐isomer. These differences are rationalized based on the molecular structure and the different elearosorption properties.
Differential pulse polarographic determination of omeprazole in pharmaceutical preparations
Authors: Özaltin Nuran , Temizer Aytekin 
Published: May 2005

AbstractA new electroanalytical method was developed for the analysis of omeprazole. Various polarographic techniques and supporting electrolytes were examined. Best results were obtained with differential pulse polarography (DPP) in borate buffer (pH 9.0) solution. Linear response was observed from 2.0 × 10−7 M to 2.0 × 10−5 M. The peak potential was observed at –1.28 V (vs. Ag/AgCl). The developed method was applied to two different commercial hard gelatin capsules, containing enteric‐coated granules, preparations. The relative standard deviations were found to be 3.04% (brand A) and 2.88% (brand B).
Electroanalytical applications in occupational and environmental health
Authors: Ashley Kevin 
Published: May 2005

AbstractElectroanalytical chemistry has been used for years in the occupational and environmental health fields. Portable sensors and analytical devices based on electrochemical (EC) methods are commonly used on‐site in the workplace. Laboratory EC methods also have been used extensively for the analysis of industrial hygiene and related samples. Recent advances in electroanalytical methodology may lead to new analytical applications in the occupational health arena, both in the laboratory as well as on‐site in the workplace. Applications in heavy metals analysis, analysis for inorganic and organic species, and bioanalysis are exemplified. This article provides an overview of the history of EC analysis for industrial hygiene purposes, and also summarizes current and newly developed applications of electroanalytical methods in occupational and environmental health.
The electrochemistry of dibutyltin at mercury electrodes in aqueous media
Authors: Turoczy Nicholas J. , Carter Rodney J. , Bond Alan M. 
Published: May 2005

AbstractThe electrochemical reduction of dibutyltin (Bu2Sn2+) at mercury electrodes has been investigated in aqueous media containing nitrate and chloride electrolytes using the techniques of direct current (DC) polarography, differential pulse (DP) polarography, DP voltammetry, and cyclic voltammetry. In 0.10 M nitrate media, the initial charge transfer process occurs at approximately –0.7 V (vs. Ag/AgCl) and is described by the equation

in which a reversible charge transfer occurs with completely surface‐confined dibutyltin. However, when longer time domains at a hanging mercury drop electrode (HMDE) are used, the complexity of the electrochemistry increases, which is attributed to the occurrence of butyl exchange processes with the electrode mercury and consequent disruption of the film of adsorbed dibutyltin. In 0.50 M chloride media, the extent of adsorption is considerably less, and the processes, but not necessarily the postulated mechanism, correspond more closely to that described by previous workers for the reduction of dibutyltin compounds in ethanol‐water mixtures.
Redox reaction of peroxidase at poly(o‐phenylenediamine) modified electrode
Authors: Deng Qing , Dong Shaojun 
Published: May 2005

AbstractThe redox conversion of heme‐containing protein horseradish peroxidase (HRP), which has a molar mass of 40,000 was studied. The conversion was obtained at an electrochemical polymerized ophenylenediamine (PPD) film‐modified platinum electrode. Optical thin‐layer spectroelectrochemical techniques were applied to determine the characteristics of the electrochemical processes. The modified film can mediate the redox conversion of the HRP.
Investigations on adsorption potentiometry: Part 4. Derivative adsorption chronopotentiometry of the bismuth‐2‐(5′‐bromo‐2′‐pyridyeazo)‐5‐diethylaminophenol system
Authors: Jin Wenrui , Wang Junying 
Published: May 2005

AbstractDerivative adsorption chronopotentiometry of the bismuth complex with 2‐(5′‐bromo‐2′‐pyridylazo‐5‐ diethylaminophenol (5‐Br‐PADAP) has been described. The theory of derivative adsorption chronopotentiometry for the complex system and the method of determination of the composition, the conditional stability constant, as well as the number of electrons transferred by the electroactive complex adsorbed on the surface of the electrode have been discussed. In 0.025 mol/L NaOH, the linear range of the method is 2 × 10−9 to 1.1 × 10−7 mol/L for the preconcentration time of 120 seconds. This method has been used to determine the bismuth content in food.
Simultaneous determination of lead, copper, and mercury at a modified carbon paste eletrode containing humic acid
Authors: Jeong Euh‐Duck , Won Mi‐Sook , Shim Yeon‐Bo 
Published: May 2005

AbstractThe modified carbon paste electrode (CPE) responding simultaneously to lead(II), copper(II), and mercury(II) ions has been constructed by incorporating humic acid (HA) into the graphite powder with Nujol oil. Simple immerging of the electrode into the measuring solution containing these metal ions led to the chemical deposition of the ions onto the electrode through the complexation of the ions with HA. Cyclic and differential pulse voltammetry (DPV) characterized the modified electrode's surfaces. Several cyclings of the potential regenerated the electrode (from more positive than the stripping potential of reduced Hg to more negative than the reduction of Pb(II)ion), which was then used for another deposition. After five deposition/measurement/regeneration cycles, the peak current of voltammograns of the analyte decreased slightly. The response reproduced with a 5.1% relative standard deviation. We also applied ihe differential pulse technique to the previously mentioned system. Here, the detection limit tor Pb(II), Cu(II), and Hg(II) ions were 5.0 × 10−9 M 8.0 × 10−9 M, and 8.0 × 10−9 M, respectively, for 20 minutes of deposition time. After pretreatment of silver(I) ion with KC1, we could not observe any interference by other metal ions on the determination of the test ions in aqueous solution. Satisfactory results were acquired for the determination of the test metal ions in certified standard urine reference material SRM's 2670 (trace elements in urine).
Amoxycillinium‐Selective plastic membrane electrodes based on amoxycillinium‐phosphotungstate ion associate
Authors: Shoukry A. F. , Issa Y. M. , Rizk M. S. , Abdel‐Aal M. M. 
Published: May 2005

AbstractThe (1:3) (phosphotungstate:amoxycillinum) ion associate is used as the ion exchanger in preparing conventional and coated wire plastic‐membrane electrodes for amoxycillin (Am). The performance characteristics of the electrode are as follows: presoak time, 30 minutes; average slope: 59 ± 0.8 mV/ concentration decade, at 25°C, for 24 hours of continuous soaking; usable concentrations range, 1.96 × 10−4 to 1.5 × 10−2 M (Am); working pH range 3 to 9, and mean isothermal coefficient, 2.25 × 10−3 mV/°C. The electrode displays very good selectivity for Am toward a large number of inorganic and organic cations. The standard addition method and potentiometric titration are used to determine Am in pure solutions and in pharmaceutical preparations.
The electrocatalytic oxidation of D(+)‐glucose by a cis‐dioxoruthenium complex
Authors: Lai Yip‐Kai , Wong Kwok‐Yin 
Published: May 2005

AbstractThe ruthenium oxo complex electrogenerated from Cis‐[RuL2 (OH2)2]2+ (L = 6,6′‐dichloro‐2,2′‐bipyridine) is an active catalyst for the oxidation of D(+)‐glucose in solution. The second‐order rate‐constant for the reaction between cis [RuL2O2]2+ and D( + )glucose in 0.1 M CF3CO2H evaluated by rotating disk voltammetry is (1.2 ± 0.2) × 102 dm3 mol−1s−1. The chemically modified electrode prepared by immobilization of the ruthenium complex inside a Nafion film on the pyrolytic graphite electrode surface is capable of catalyzing glucose oxidation at potentials comparable to other reported modified electrodes.
Amperometric microbiosensors for detection of hydrogen peroxide and glucose based on peroxidase‐modified carbon fibers
Authors: Csöregi Elisabeth , Gorton Lo , Marko‐Varga György 
Published: May 2005

AbstractA mediatorless amperometric microbiosensor can be constructed by immobilizing horseradish peroxidase (HRP) onto the surface of carbon fibers Several types of carbon fibers were tested. The best microelectrode, constructed by immobilizing HRP on high modulus. type (GH) carbon fibers, presented a linear response range between 20 μM and 2.5 mM H2O2 and a detection limit of 0. 2 μM H2O2 calculated as twice the signal‐to‐noise ratio. When HRP was coimmobilized with hydrogen peroxide‐producing glucose oxidase (GOD), a glucose sensor could be constructed with a linear potential range between 20 and 160 μM glucose, with a detection limit of 20 μM. The detection of the substrates was performed at a working potential of 0 mV (vs. SCE) at pH 6.0.
The preparation in situ of a silver–silver chloride reference electrode
Authors: Kulys Juozas , Munk Jens A , Buch‐Rasmussen Thomas , Hansen Henrik E. 
Published: May 2005

AbstractThe preparation in situ of a silver‐silver chloride reference electrode includes anodic‐cathodic pretreatment of a silver electrode in a phosphate buffer solution comprising 0.1 M sodium chloride. At pH 7.0 and 25°C and with optimally pretreated electrodes, the potential of the Ag/AgCl electrode was 45.0 mV (vs. SCE) with a reproducibility of 0.2%. In a period of 30 seconds following a delay of 2 to 10 seconds, the electrode shows a very stable potential that changes only 0.2 to 0.3%. The electrode potential changes 0.3 mV/°C. The electrode shows nernstian dependence of the potential to the sodium chloride concentration. At the physiological level, the only electrochemically active compound that significantly influences the potential of the electrode is reduced glutathione. Paracetamol (0.2 mM) and uric acid (0.27 mM) after slightly the electrode potential. The electrode parameters in plasma are close to those of phosphate buffer solution, whereas in artificial blood, the reproducibility and the stability of the potential decrease. The reproducibility and stability of the electrode potential in capillary blood was 1.4 and 3.7%, respectively.
Field‐Effect transistors as transducers in biosensors for substrates of dehydrogenases
Authors: Vering Thomas , Schuhmann Wolfgang , Schmidt Hanns‐Ludwig , Mikolajick Thomas , Falter Thomas , Ryssel Heiner , Janata Jiri 
Published: May 2005

AbstractA specially designed field‐effect transistor (FET) with a significantly enlarged gate area was applied in a classical urea enzyme FET (ENFET). The resulting high stability and sensitivity toward pH shifts make it predestinated for the measurement of H+ produced in the equilibrium of NAD+ ‐dependent enzymatic reactions, especially when the equilibrium is shifted by a subsequent reaction. As a model, the glucose dehydrogenase (GDH) reaction connected to an ion‐sensitive field‐effect transistor (ISFET) is demonstrated by which glucose could be determined in the range from 1 to 40 mM. A platinum electrode on the gate of the FET permits the measurement of reduction equivalents (NADH) by means of the recently, reported chronopotentiometrical methods. Thus, in principle, a way toward a redox ENFET is shown.
Evaluation of mediators for development of amperometric microbial bioelectrodes
Authors: Kaláb TomáŠ , Skládal Petr 
Published: May 2005

AbstractThe microbial biosensors were constructed from carbon paste electrodes (CPEs) modified with insoluble mediators and immobilized membrane vesicles or whole cells of the bacterium Paracoccus denitrificans. The best results were obtained with membrane vesicles and ferrocene (FC). This system could serve for determination of succinate, D‐lactate, and L‐lactate. Significant increase of signal was obtained when competitive flux of electrons to oxygen was blocked by inhibiting terminal oxidases using cyanide.
Electroanalytical study of the antioxidant tert‐butylhydroquinone (TBHQ) in an oil‐in‐water emulsified medium
Authors: González‐Cortés Araceli , Armisén Pilar , Asunción Ruiz M. , Yáñez‐Sedeño Paloma , Pingarrón José M. 
Published: May 2005

AbstractAn electroanalytical study of the oxidation of tert‐butylhydroquinone (TBHQ) by differential pulse polarography (DPP) and square‐wave voltammetry (SWV) in an emulsified medium formed with ethyl acetate and Pluronic F‐68 is carried out. The optimization of the chemical variables of the emulsions by DPP allowed the choice of the following working conditions: pH 9.0, 0.04% Pluronic F‐68, 2.0 mL of ethyl acetate and 3 minutes as ultrasonic stirring time. The demonstrated reversibility of the electrode process at the mercury electrode makes it suitable for the application of SWV. The influence of the square‐wave (SW) characteristic parameters on the TBHQ net peak current at the hanging mercury drop electrode (HMDE) was tested. Calibration graphs were obtained within the ranges 1.0 × 10−5 to 1.0 × 10−4, 1.0 × 10−6 to 1.0 × 10−5, and 1.0 × 10−7 to 1.0 × 10−6 mol L−1. An improved sensitivity with respect to that obtained by DPP was produced. The limit of detection was found to be 6.2 × 10−8 mol L−1. Interferences from tert‐butylhydroxyanisole, tert‐butylhydroxytoluene, propylene glycol, citric acid, propyl gallate, and ascorbic acid were tested. The proposed method was applied with good results to the determination of TBHQ in spiked popcorn samples by direct emulsification of the ethyl acetate sample extract.
Square wave voltammetry with arrays of liquid/liquid microinterfaces
Authors: Pereira C. Melo , Silva Fernando 
Published: May 2005

AbstractSquare wave voltammetry (SWV) has been successfully applied to arrays of liquid/liquid (L/L)microinterfaces formed across microholes perforated on a polyester film. The study of CIO4− ion transfer from water to 1.2‐dichloroethane (DCE) showed that the experimental parameters Esw, Es, and f are identical to those found for the reversible electron transfer on solid microelectrodes.
High‐Performance adsorptive cathodic stripping voltammetry of nickel and cobalt in seawater
Authors: Pérez‐Peña J. , Hernández‐Brito J. J. , Herrera‐Melián J. A. , Collado‐Sánchez C. , van den Berg C. M. G. 
Published: May 2005

AbstractThe voltammetric determination of trace metals in seawater suffers from the interference of dissolved oxygen and engine vibrations onboard ship. It is here attempted to overcome these interferences using a high‐frequency (1 to 20 kHz) staircase modulation during the voltammetric scan (high‐performance adsorptive cathodic stripping voltammetry, HPACSV). Comparative experiments using the square‐wave modulation showed that this modulation was not effective at such a high frequency. A comparison between various complexing agents (DMG and nioxime) and pH buffers (HEPES/NH4OH, borate/NaOH, and TEA/NH4OH) showed that the determination of nickel and cobalt was similarly improved by the high‐speed potential scan in all conditions. Fast potential scans cause a large increase of the peak area and peak heights using staircase modulation. The peaks are wider, and the peak potentials are shifted toward negative values due to the ohmic drop, but the analytical determination is not disturbed. Optimal sensitivity for the determination of cobalt and nickel in seawater was obtained using TEA buffer and DMG as the adsorptive ligand. The nioxime wave was found to interfere in the cobalt peak at high scan rates so that this ligand is not recommended for HPACSV. Comparative tests showed that the sensitivity for nickel and cobalt determinations was highly improved by the fast scan rates. Furthermore, the reduction current of dissolved oxygen was partially masked so that measurements could be taken without a previous purge of the sample. Finally, the scans were insensitive to the solution turbulence so measurements could be readily carried out onboard of an oceanographic vessel or without switching off the stirrer. Low levels of nickel (2 nM) could be determined in seawater by using a deposition time of 20 seconds and of 120 seconds for 0.05 nM cobalt from turbulent and unpurged solutions. A fast determination method for labile nickel and cobalt is proposed.