bluuebunny/crossref_metadata_2025_split huggingface dataset:
Four potential step differential amperometry in a single pulse sequence mode
Authors: Fang Yuzhi , Tong Wei , He Pingang , Wang Rener , Jin Litong 
Published: May 2005

AbstractA new type of four potential step differential amperometry in a single pulse sequence mode is proposed on the basis of four potential step differential normal voltammetry. The charging current tends to be eliminated, and the background current is set at zero after the differentiation and addition of the sampling currents on these four potential steps. The signal‐to‐noise ratio is enhanced by utilizing a series of pulses. In addition, since the potential returns to its initial point, it is advantageous for electrode cleaning and the study of solid electrode and adsorption systems. This provides an alternative approach for electrical current‐type electrochemical sensors, electrochemical detection in liquid chromatography, and electrode kinetics studies.
Determination of kinetic parameters from the steady‐state voltammograms at microring electrodes
Authors: Zhnang Qian‐Kun , Cben Hong‐Yuan 
Published: May 2005

AbstractUnder steady‐state conditions, the i‐E equations at thin microring electrodes for reversible, quasi‐reversible, and irreversible systems are derived by using uniform surface concentration boundary condition. Using these results, the heteroger eous rate constants of several fast electron transfer reactions under steady‐state diffusion conditions are measured. The measured rates are in good agreement with existing data. As a result, all these efforts are successful in a simplified way compared to those required for relaxation techniques.
Adsorptive stripping voltammetric determination of folic acid in pharmaceutical preparations
Authors: Szczepaniak W. , Ren M. 
Published: May 2005

AbstractAn adsorptive stripping voltammetric (AdSV) procedure is proposed for determination of folic acid (FA) in cores and coated pellets of Hemofer (FA/iron tablet). The adsorptive stripping response was evaluated with respect to the electrolyte solution, the accumulation time and potential, and the concentration dependence. The relationship between ip and FA concentration was linear over the range 1 × 10−8 to 5 × 10−7 M FA. The conditions of cores and pellets preparation for analysis were established. The relative standard deviation is 2.4% for a content of FA of 0.35 mg per core (n = 5).
Nitro radical anion formation from nitro‐substituted amphetamine derivatives
Authors: Nuñez‐Vergara Luis J. , Matus C. , Alvarez‐Lueje A. F. , Cassels B. K. , Squella J. A. 
Published: May 2005

AbstractThe cyclic voltammetric characteristics of two nitroamphetamine derivatives (2‐nitro‐4,5‐dimethoxyamphetamine and 2‐nitro‐4,5‐methylenedioxyamphetamine) have been investigated in different media. In mixed media (aqueous buffer and DMF, dioxane, or acetonitrile) a reversible one‐electron reduction takes place to form a stable nitro radical anion. At more negative potential values, a further three‐electron reduction occurs irreversibly to give the hydroxylamine derivative. Cyclic voltammetry (CV) has been employed to study the tendency of the nitro radical anions to undergo further chemical reactions. The subsequent chemical reaction corresponds to a second‐order process, a dismutation reaction electrochemically initiated. Data about rate constants and half‐life times in mixed media are reported.
Electroreduction of benzoylacetanilides in nonaqueous medium
Authors: Abou‐Elenien G. M. , El‐Anadouli B. E. , Baraka R. M. 
Published: May 2005

AbstractThe electroreduction of three series of benzoylacetanilides has been investigated in benzonitrile at a platinum electrode. One series (I) contains substituents on the benzoyl moiety, the second (II) has the substituents on the anilide moiety, and the third (III) has substituents on both the anilide and benzoyl moieties. All of these compounds are reduced in a single irreversible two‐electron process forming the corresponding dianion which abstracts protons from the media to saturate the anilide CO. A good linearity is obtained when the E1/2 value is plotted against the substituent constant of the substituents in the different series (I–III).
Electrochemical reduction behavior and analysis of some organophosphorous pesticides
Authors: Subbalakshmamma M. , Reddy S. Jayarama 
Published: May 2005

AbstractThe electrochemical reduction behavior of organophosphorous pesticides such as monocrotophos, phosphamidon, and dichlorvos have been studied by employing dc polarography, cyclic voltammetry, ac polarography, differential pulse polarography miilicoulometry, and controlled potential electrolysis. The general reduction mechanism of these compounds has been suggested based on the results obtained. A differential pulse polarographic method is developed for the determination of title compounds in agricultural formulations. Both standard addition and calibration methods are used for the analysis experiments. The lower detection limits are found to be 1.0 × 10−8, 1.25 × 10−8 and 1.2 × 10−8 respectively.
Formation of an intermetallic compound between selenium and copper
Authors: Somer Güler , Karacan Mehmet S. 
Published: May 2005

AbstractWhen selenite solutions are determined in the presence of copper using anodic stripping voltammetry (ASV), a new peak appears, which is not associated with copper or selenium. It is attributed to the formation of an intermetallic compound between copper and selenium. To verify the existence of such a compound, cyclic voltammograms have been recorded. It has been shown that there is formation of such a compound, and its composition depends on the copper‐to‐selenite ratio.
Stabilization of the redox polymer [Os(bipy)2(PVP)10Cl]Cl by in situ chemical cross‐linking
Authors: Doherty Andrew P. , Buckley Tim , Kelly David M. , Vos Johannes G. 
Published: May 2005

AbstractThe redox polymer [Os(bipy)2(PVP)10Cl]Cl, where bipy is 2,2′‐bipyridy and has been physically stabilized by chemical cross‐linking at various levels via the solid‐state reaction with the cross‐linking agents p‐dibromobencane, 1,5‐dibromopentane, and 1,10‐ dibromobencane. The stability of the resulting polymer films under the severe hydrodynamic conditions of thin‐layer flow cells and at rotating disk electrodes (RDEs) was greatly increased compared to the uncross‐linked polymer. The charge transport properties of the redox polymer were maintained or improved by cross‐linking. The surface and Nernstian behavior of the cross‐linked redox materials are not found to be substantially affected by cross‐linking.
Electrochemical immunoassay: Simple kinetic detection of alkaline phosphatase enzyme labels in limited and excess reagent systems
Authors: Treloar Paul H. , Nkohkwo Asa'ah T. , Kane John W. , Barber Don , Vadgama Pankaj M. 
Published: May 2005

AbstractKinetic measurement of an alkaline phosphatase enzyme label was performed with amperometric detection using conversion of substrate 4‐aminophenyl phosphate to the electroactive phenolic, measured at +125 to +200 mV tvs. Ag/AgCl. Calibration plots for thyroxine‐binding globulin (TBG) and cortisol were obtained by excess reagent and limited reagent immunoassays, respectively, which were comparable with those obtained using colorimetric detection. These provided a measurement range of 31–1000 μg/L for TBG and 100–2000 nM for cortisol. An antibody‐bound label was monitored in this system, and covering the electrode with a simple dialysis or polycarbonate membrane avoided electrode fouling. The kinetic mode of detection reduced assay time and helped to simplify the assay protocol.
Electrochemical study of isopolymolybdate(VI) anion transfer across the water/nitrobenzene interface
Authors: Wang Erkang , Wang Hanming 
Published: May 2005

AbstractIsopolymolybdate (VI) anion transfer across the water/nitrobenzene (w/n) interface was studied by cyclic voltammetry. The effect of pH and responsed kinetics of isoplymoybdate anion's formation in the water phase on the transfer behavior have been studied. At 1.0 < pH < 3.0 and 7.0 > pH > 5.8, transfer species are [HMo8O26]3− and [H2Mo–O24]4−, respectively. At 5.8 > pH > 3.0, the two anions can transfer across the w/n interface simultaneously. Transfer process was contrilled by difusion of isopolymolybdate anions toward the interface. The standard transfer potentials Δφ0 and the standard Gibbs energy ΔG, of the two isopolymolybdate anions were determined, and the transfar mechanism has been discussed.
Utilization of Canavalia maritima as biocatalyst for urea biosensors
Authors: de Oliveira Neto Gracliano , Godinho Oswaldo E. S. , Aleixo Luiz M. , da Silva Valdinete L. 
Published: May 2005

AbstractSeeds of Canavalia maritima are ground after removal of the external coat and are used for the construction of a new enzymatic electrode for urea. Aliquots (10 mg of the powder) are immobilized at the surface of an ammonia gas‐sensing electrode, via glutaraldehyde or, alternatively, on PVC membranes. The analytical performance of the biosensors for serum urea determination is comparable to the spectrophotometric method.
Investigations of platinized and rhodinized carbon electrodes for use in glucose sensors
Authors: White Stephen F. , Turner Anthony P. F. , Schmid Rolf D. , Bilitewski Ursula , Bradley Joanne 
Published: May 2005

AbstractGraphite electrodes were modified by the electrodeposition of either platinum or rhodium, using cyclic voltammetry. Following only brief periods of treatment, platinized carbon electrodes were able to directly oxidize glucose at a potential of +350 mV (vs. Ag/AgCl). By narrowing both the potential range of deposition (–450 to –500 mV) and cycling period (50 seconds at a scan rate of 10 mV s−1), the effects of direct glucose oxidation could be significantly reduced. Detection of H2O2 at +400 mV was possible; glucose enzyme electrodes were constructed, with glucose oxidase immobilized in hydroxyethylcellulose, and operated at this potential. These sensors had a linear range of 0.1 to 25 mM glucose and a slope of 8 nA/mM. Other electrodes were prepared by the electrodeposition of rhodium. These base electrodes proved to be insensitive to glucose and produced‐higher currents (compared to low platinum electrodes) to H2O2. Glucose sensors were constructed using rhodinked electrodes. Again operating at + 400 mV, these sensors had a linear range from 0.1 to 20 mM and a slope of 21 nA/mM glucose.
Indirect determination of surfactants by adsorptive voltammetry: Part 1: Determination of Trace and Ultratrace Concentrations of Sodium Dodecylbenzene Sulfonate
Authors: Adeloju S. B. , Shaw S. J. 
Published: May 2005

AbstractThe determination of sodium dodecylbenzene sulfonate based on the suppression of the adsorptive voltammetric response of nickel in the presence of dimethylglyoxime is described. Sensitive and accurate determination of the anionic surfactant is accomplished at trace and ultratrace concentrations by the use of a combination of electrodes, such as the hanging mercury drop electrode (HMDE), glassy carbon mercury film electrode (GCMFE), and a dropping mercury electrode (DME), The first two electrodes enabled the determination of sodium dodecylbenzene sulfonate down to ultratrace concentrations, while the latter was useful for rapid determination of trace concentrations of the surfactant. Despite the higher sensitivity obtained for the anionic surfactant on the GCMFE, the best limit of detection of 100 μg/L and the optimum recovery efficiency of 104 ± 8% were accomplished with the HMDE. Compared with the widely accepted spectrophotometric method, the adsorptive voltammetric approach is more rapid, has a much wider linear concentration range (based on the combined use of an HMDE or GCMFE and the DME), and is applicable at the ultratrace level.
Indirect determination of surfactants by adsorptive voltammetry: Part 2: Determination of hexadecyl trimethyl ammonium bromide and cetyl pyridinium chloride in industrial and consumer products
Authors: Adeloju S. B. , Shaw S. J. 
Published: May 2005

AbstractA method is described for the indirect determination of trace and ultratrace concentrations of hexadecyltrimethylammonium bromide (HTMAB) and cetyl pyridinium chloride (CPC) in industrial and consumer products by adsorptive voltammetry The determination of HTMAB at the trace concentration was accomplished by an indirect adsorptive polarography on a dropping mercury electrode (DME), while the determination of ultratrace amounts of CPC was performed by an indirect adsorptive stripping voltammetry on a hanging mercury drop electrode (HMDE). The detection limits accomplished for these surfactants were 5 mg/L and 10 μg/L, respectively. These were up to 100 times lower than those obtained by the spectrophotometric method. The linear concentration ranges accomplished for the surfactants under the specified conditions were 0–65 mg/L and 0–300 μg/L, respectively. The development and the incorporation of a simple and rapid separation scheme based on the use of a C18 sep‐pak cartridge with the adsorptive polarographic and voltammetric techniques were effective in overcoming the matrix interference problem from commercial domestic products. The application of the method to industrial and consumer products, such as disinfectant, lozenges, and mouth wash solutions was successful, resulting in an average recovery efficiency of 93 ± 9% for both surfactants.
Inner reference electrodes and filling solutions conferring linear temperature characteristics on glass pH electrodes
Authors: Midgley Derek 
Published: May 2005

AbstractGlass electrodes with linear temperature characteristics are described. By use of a Ag‐AgBr inner reference element and an inner reference solution containing a zwitterionic buffer (MOPS), an electrode is obtained that almost has the ideal characteristics of isopotential pH (pHiso = 7) and zeropoint pH (pH0 = 7) necessary for use with the temperature compensation circuits on most pH meters. A conventional Ag‐AgCl (3 M KCl) external reference electrode is used. Excellent linearity of changes in standard potential has been observed in the range tested (5 to 65°C), and the slope factor, thermal hysteresis, and speed of response to temperature change are as good as for commercially available electrodes. The application of electrodes with these characteristics should improve the accuracy of temperature compensation in industrial and environmental measurements. Other inner‐reference electrodes and buffers are considered.
Fabrication and characterization of tips for electrochemical scanning tunneling microscopy
Authors: Chen Zhen Fang , Wang Erkang 
Published: May 2005

AbstractWe report a new technique for preparing tips for electrochemical scanning1 tunneling microscopy (ECSTM) with particular consideration of its simplicity and reproducibility. In preparing scanning tunneling microscopy (STM) tips by electrochemical etching, we chose an etching process with the formation of a neck‐shaped part of an etched wire by applying a suitable etching voltage, and then we adopted a two‐step etching process to prevent over etching. The prepared tip possessed a curvature of 100 to 300 nm, much smaller than that of the tip prepared by the conventional method. The etched tip was insulated with silicon rubber or epoxy resin under an optical microscope. This controllable technique allows that a reproducible tip with an exposed area of 0.44 to 7.76 μm2, which has proved to be available for in situ experiment, could be made.
Amperometric flow‐injection analysis of purine nucleotides: Comparison of selectivity for hydrolytic cleavage of purine nucleotides
Authors: Yao Toshio , Tsureyama Kiminori , Nakahava Taketoshi 
Published: May 2005

AbstractFour hydrolases (alkaline phosphatase, apyrase, 5′‐nucleotidase, and adenosine‐5′‐triphosphatase) are immobilized onto the controlled‐pore glass, respectively. They are used as the reactor for the enzyme‐catalyzed hydrolytic cleavage of purine nucleotides, in a flow‐injection system based on the combined use of the following coimmobilized purine nucleoside phosphorylase–xanthine oxidase reactor and amperometric detector downstream. Four hydrolase‐immobilized reactors possess interesting differences in the selectivity for the hydrolytic cleavages of purine nucleotides. The alkaline phosphatase reactor catalyzes enzymatically the complete conversion of all the purine nucleotides to the corresponding nucleosides. The apyrase reactor converts completely both nucleoside triphosphate and diphosphate to nucleoside monophosphate. The 5′‐nucleotidase reactor is selective for the hydrolytic cleavage of nucleoside monophosphate to nucleoside. The analytical importance of these hydrolase‐immobilized reactors is discussed for the selective detection of purine nucleotides.
Micromachined electrochemical flow cell for biosensing
Authors: Murakami Yuji , Uchida Takashi , Takeuchi Toshifumi , Tamiya Eiichi , Karube Isao , Suda Masayuki 
Published: May 2005

AbstractA miniaturized electrochemical flow cell was fabricated on a silicon substrate using micromachining techniques, including photolithography, vacuum deposition, anisotropic etching, and fusion bonding. The flow cell consisted of a glass plate with gold elearodes, a silicon chip with a V‐shaped groove, and immobilized glucose oxidase. Hydrogen peroxide and glucose were measured by direct‐batch injection and by using the device in flow‐injection analysis (FIA) system.
Electrocatalytical oxidation of glucose on graphite using covalently immobilized glucose oxidase and 1,6‐dithia‐ and 1,6‐dioxapyrenes as mediators
Authors: Kulys J. , Razumas V. , Kazlauskaite J. , Marcinkeviciene J. , Buch‐Rasmussen T. , Hansen H. E. , Bechgaard K. , Christensen J. B. , Frederiksen P. 
Published: May 2005

AbstractElectrocatalytical oxidation of glucose on graphite using new mediators (1,6‐dithiapyrenes (DTPs) and 1,6‐dioxapyrenes) was performed. The electrocatalysis of glucose oxidase (GO) was based on the dithia(dioxa)pyrene cation‐radicals reaction with reduced GO. The rate of reduced GO oxidation by the cation‐radical of dithiapyrene was 4.8 × 104 M−1 s−1 at 25°C (pH 7.0). For enzyme electrode preparation, the GO was covalently immobilized by carbodiimide, and the mediator was adsorbed on a graphite electrode. The dithia(dioxa)pyrenes mediated glucose oxidation proceeds at potentials higher than 0.1 V (versus standard calomel electrode (SCE)). Of the investigated substituted dithia(dioxa)pyrenes, the largest electrocatalytical current was observed with electrodes comprising of DTP. Linear calibration graphs of these electrodes were obtained up to 12 mM of glucose, the maximal electrode activity was in the range of pH 6.5 to 8.0, and the temperature coefficient was 5.6%/°C. The investigated electrocatalytical systems can be used for construction of disposable senses for glucose determination in physiological solutions.
Individual and simultaneous determination of zinc and cadmium in biological tissues by flow injections / stripping voltammetric analysis
Authors: Izquierdo A. , De Castro M. D. Luque , Valcárcel M. 
Published: May 2005

AbstractA flow‐injection (FI) voltammetric‐stripping method for the simultaneous determination of Cd and Zn is proposed after a systematic study of the variables affecting the method. The low determination limits, 1 × 10−9 and 5 × 10−9 M (detection limits 8 × 1010– and 2 × 10−9 M for Cd and Zn, respectively), and rsd. values, 1.57 and 5.16% for Cd and Zn, respectively, allow one to apply the method to real samples (biological tissues and reference materials) with good results. No formation of intermetallic compounds was detected.
Electrochemical behavior and determination of β‐carboxyethylgermanium sesquioxide
Authors: Hasebe Kiyoshi , Hikima Satoshi , Motonari Masayuki , Yamagishi Akihiko , Kakizaki Teiji 
Published: May 2005

AbstractThis article describes the electrochemical behavior of β‐carboxyethylgermanium sesquioxide (Ge‐132) on mercury electrodes in weakly acidic solution. The Ge‐132 exhibits two Well‐defined cathodic waves in linear‐sweep voltammetry and polarography. The first wave in a voltammiogram of Ge‐132 is a simple two‐electron reduction and exhibits the property of adsorption. From chronoamperometry, the reaction in die second wave, however, proves to be an ECE mechanism and ultimately yields metallic germanium and propionic acid. The determination of small amounts of Ge‐132 is investigated by differential pulse polarography in an acetate buffer. The detection limits of Ge‐132 are below 0.2 μmol dm−3.
Electroanalytical study of chelating extractants: LIX 34
Authors: Huebra Marta M. , Elizalde Maŕia P. , Castresana José M. 
Published: May 2005

AbstractThe voltammetric behavior of 4‐methyl‐N‐8‐quinolinybenzenesulfonamide, closely related to the active component of the commercial extractant LIX 34, has been studied in 0.1 M KCl/25% methanol medium as a function of pH, using polarography and cyclic voltammetry techniques. The elearochemical behavior of the extractant in the presence of Cu (II) ions has also been described. The commercial LIX 34 product exhibits a similar behavior both in differential pulse polarography and cyclic voltammetry, and polarogrnahic determination methods have been developed for both reagents. The relationship between reduction peak current and concentration is linear up to 1.96 × 10−6 M for 4‐methyl‐N‐8‐quinolinylbenzenesulfonamide, and the corresponding function for LIX 34 indicates a low percentage of the active component in the commercial extractant.
New amperometric dehydrogenase electrodes based on electrocatalytic NADH‐oxidation at poly (methylene blue)‐modified electrodes
Authors: Karyakin Arkady A. , Karyakina Elena E. , Schuhmann Wolfgang , Schmidt Hanns‐Ludwig , Varfolomeyev Sergei D. 
Published: May 2005

AbstractPoly(methylene blue) (PMB)‐modified electrodes show excellent properties for the electrocatalytic oxidation of NADH concerning the optimal working potential of 0 to 100 mV (vs. SCE)and their operation stability. By means of dehydrogenases entrapped within a Nafion film on top of the PMB layer, new amperometric biosensors for glucose, lactate, malate, and ethanol could be obtained with improved integration of the enzyme and the electrocatalyst directly on the electrode surface. Coentrapment of the negatively charged NAD+within the negatively charged Nafion Polyelectrolyte leads to reagentless dehydrogenase electrodes for one‐shot or short‐term applications.
Lactate biosensor based on a lactate dehydrogenase/nicotinamide adenine dinucleotide biocomposite
Authors: Wang Joseph , Chen Qiang 
Published: May 2005

AbstractA new biocomposite, fabricated by incorporating lactate dehydrogenase (LDH) and nicotinamide adenine dinucleotide (NAD+) within a graphite‐epoxy matrix, is used as a polishable (renewable) and robust biosensor for lactate. Highly sensitive and rapid amperometric biosensing is accomplished at relatively low potentials. The regeneration capability of the biocomposite probe circumvents problems of surface fouling inherent to the detection of NADH. Flow injection detection of lactate, with a sample throughput of 60/h, detection limit of 5 × 10−4 M, precision of 2.5% (RSD for n = 40), and linearity up to 2 × 10−2 M, is illustrated.