bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cobalt‐porphyrin‐nafion film on carbon microarray electrode to monitor oxygen for enzyme analysis of glucose
Authors: Dong Shaojun , Kuwana Theodore 
Published: May 2005

AbstractA microcarbon array electrode was modified by the placement of a Nafion film containing cobalt tetra‐methylpyridyl phorphyrin on its surface. This electrode was applied to the analysis of solution glucose when it was further modified by the immobilization of glucose oxidase on the outermost surface of the Nafion by the cross‐linking of serum albumin with glutaraldehyde. The concomitant decrease in the concentration of oxygen, as it was consumed in the enzymatic reaction of glucose with glucose oxidase, was determined by either cyclic voltammetry or a double potential step method at the porphyrin‐Nafion catalytic electrode. Glucose could be determined in the range, of 0.01‐;4 mM rapidly, without interference from substances such as accurate or other saccharides.
Tensammetric and indirect amperometric detection of phospholipids
Authors: Schmidt Thomas , Emons Hendrik 
Published: May 2005

AbstractElectrochemical detection procedures for electroinactive phospholipids were developed for flow injection (FI) systems and high performance liquid chromatography (HPLC). The methods are based on the adsorption of these surface‐active compounds, which was characterized in solutions containing acetonitrile, water, and methanol. Tensammetric FI detection at mercury electrodes was systematically studied with respect to various experimental parameters. The method was also applied to the normal phase HPLC determination of phospholipids, but with higher detection limits. In addition, an indirect amperometric detection method based on the inhibition effect of adsorbed phospholipids on electrode reactions at glassy carbon fibers was explored. This can be also used for FI systems and in HPLC. Significantly wide linear dynamic ranges were obtained for the determination of phospholipids.
Enzymatic determination of ethanol by flow injection analysis using a Kel‐F wax carbon paste electrode
Authors: Wangsa Julie , Danielson Neil D. 
Published: May 2005

AbstractSurface passivation during oxidation of NADH at a fluorocarbon polymer‐carbon paste electrode (CPE) was about 25% less than that of the glassy carbon or Nujol‐oil CPE. After repeated injections of 1.5 mM NADH for 12 h, the Kel‐F wax CPE maintained about 85% of its initial response. The determination of ethanol in wine samples using soluble alcohol dehydrogenase stabilized by polyethyleneglycol was demonstrated. Linearity of response extended from the detection limit of 0.44 mM to 33 mM.
Microarray electrodes as biosensors
Authors: Sohn Tae‐Won , Stoecker Paul W. , Carp Wendy , Yacynych Alexander M. 
Published: May 2005

AbstractMicrodisk and microhole array electrodes were used to construct amperometric glucose biosensors based on the detection of hydrogen peroxide. All‐chemical methods such as platinization, glucose oxidase immobilization, and electropolymerization permit electrodes of any size, shape, or surface complexity to be used for biosensors. This also gives the biosensor surface a multifunctional character, where the platinization decreases the operating potential, the immobilized enzyme provides the specificity, and the electropolymerized film prevents interferences and fouling. All of these functions are accomplished in a layer that is about 10 nm thick. The microdisk and microhole biosensors were linear to about 3 mM and 4 mM glucose, respectively, and were accurate, as checked by standard reference serum.
Hg(II) voltammetry on a 1,5‐diphenylcarbazide containing carbon paste electrode
Authors: Navrátilová Zuzana 
Published: May 2005

AbstractThe differential pulse voltammetric determination of Hg(II) at a carbon past electrode modified by 1,5‐diphenylcarbazide is described. Voltammetry of Hg(II) on various types of modified electrodes in 0.1 M KSCN (pH = 2) was studied. A detection limit 5 × 10−9 M was achieved at the carbon paste electrode containing 5% of 1,5−diphenylcarbazide in this background electrolyte.
Mercury ion‐selective polymeric membrane electrodes based on substituted diaza crown ethers
Authors: Brzozka Zbigniew , Pietraszkiewicz Marek 
Published: May 2005

AbstractThe potentiometric selectivities of membranes based on new N, N' ‐substituted 4, 13‐diaza‐18‐crown‐6 ethers were determined under different internal filling electrolytes and conditioning time of the membranes. The preference of Hg2+ over other divalent cations was observed for compounds bearing 2‐methylquinolyl or 2‐methylquinolyl‐1‐oxide groups. The membrane electrodes with ionophores 1 and 2 exhibited a linear response in the activity range 10−5 − 10−3 M Hg(NO3)2.
Enzyme electrodes with pyrolyzed CoTMPP catalyst
Authors: Gamburzev S. , Iliev I. , Atanasov P. , Kaisheva A. , Scheller F. , Pfeifer D. 
Published: May 2005

AbstractCatalytic electrode with pyrolyzed cobalt‐tetramethoxy‐phenylporphyrine (CoTMPP) for facilitating the anodic detection of hydrogen peroxide is investigated. This modified electrode can operate at potentials lower (by ca. 0.2 V) than a platinum electrode. The electrode is tested in membrane enzyme biosensors for the determination of glucose and lactate in water solutions.
Nucleoside oxidase‐modified carbon paste electrode containing quinone: Cathodic current response to nucleosides
Authors: Ikeda Tokuji , Hashimoto Yutaka , Senda Mitsugi , Isono Yoshikazu 
Published: May 2005

AbstractThe cathodic current for the reduction of benzoquinone at a glassy carbon electrode was increased in the presence of nucleoside oxidase and inosine. This was attributed to the regeneration of benzoquinone from hydroquinone by the laccaselike reaction of the enzyme, the rate of which depended on the concentration of inosine in the solution. Accordingly, an enzyme electrode for nucleosides was constructed by immobilizing nucleoside oxidase behind a dialysis membrane on a carbon paste electrode containing p‐benzoquinone or hydroquinone. The current response of the electrode to nucleosides was studied and the results were discussed on the basis of the laccaselike activity of the enzyme. The nucleoside oxidase‐modified electrode was tested as an amperometric enzyme electrode for nucleosides and could be used at least for three weeks.
Studies on the electrochemical behavior of 2‐(3,5‐dibromo‐2‐pyridyl)azo‐5‐diethylaminophenol‐co(II) complex in the presence of nitrite: Trace, measurements of cobalt
Authors: Zhao Zaofan , Cai Xiaohua , Pei Jianhong , Zhang Yeming , Zhou Xingyao 
Published: May 2005

AbstractIn an acetate acid buffer solution (pH = 4.5) containing 2‐(3,5‐dibromo‐2‐pridyl)azo‐5‐diethylaminophenol or 3,5‐2Br‐PADAP and nitrite, there is a catalytic single‐sweep polarographic peak that is very sensitive and selective to cobalt(II). The linear range is from 1 × 10−10 M to 1 × 10−6 M, with a detection limit of 5 × 10−11 M. Most common cations and anions do not interfere with the determination. The method has been used or the determination of trace cobalt in human hair and pure nickel nitrate samples. The mechanism involved has been investigated by various electrochemical methods, and the catalytic process is magnified image.
Theory of potentiometric stripping analysis in the case of reversible and quasi‐reversible electrode reactions
Authors: Garai Tibor , Mészáros Lajos , Bartalits Liliana , Locatelli Clinio , Fagioli Francesco 
Published: May 2005

AbstractThe theoretical treatment of potentiometric stripping analysis is presented for the cases of reversible and quasi‐reversible electrode reactions. The experimental results were found to be in good agreement with calculated data. Derivations based on different assumptions (e.g., stripping in stirred solutions, diffusion layer of constant thickness) are compared.
The determination of iron in seawater using catalytic cathodic stripping voltammetry
Authors: Yokoi Kunihiko , van den Berg Constant M. G. 
Published: May 2005

AbstractThe sensitivity of the determination of iron in natural waters, including seawater, using cathodic stripping voltammetry (CSV) with adsorptive collection of complexes with 1‐nitroso‐2‐naphthol is greatly enhanced by catalytic reoxidation in the presence of hydrogen peroxide. The limit of detection is lowered to 0.16 nM Fe (using an adsorption time of 60 s) and further to 0.03 nM Fe by increasing the adsorption time to 10 min. Interference from an increase in the background current, brought about by catalysis of the hydrogen evolution, is overcome by addition of an anionic surfactant (sodium dodecyl sulfate (SDS)). Optimal conditions include a hydrogen peroxide concentration of 1.8 mM and 5 ppm SDS. Procedures to purify the reagents from contaminant levels of iron are described. The method is successfully applied to certified seawater and samples from the North Atlantic.
Voltammetric behavior of dihydronicotinamide adenine dinucleotide phosphate at enzyme‐modified electrodes
Authors: Hua Chi , Walsh Sean , Smyth Malcolm R. , Švancara Ivan , Vytřas Karel 
Published: May 2005

AbstractThe oxidation of nicotinamide‐adenine dinucleotide phosphate (reduced form, NADPH) at glassy carbon electrodes modified with different enzymes has been studied. It was found that NADPH yielded a well‐defined anodic peak about +0.70 V (vs. Ag/AgCl) at glassy carbon electrodes coated with three different enzymes, glutathione reductase, glutathione peroxidase, and glucose oxidase, in 1.4 M potassium phosphate supporting electrolyte. It was confirmed that the enzymes immobilized at the working electrode surface reduced the overpotential for the oxidation of NADPH. This method provides a way to study the mechanism of some enzymatic reactions.
Photoelectrochemical detection and speciation of thallium (I) and thallium (III)
Authors: Barisci Joseph N. , Wallace Gordon G. 
Published: May 2005

AbstractA method that allows speciation and electrochemical detection of thallium in flowing solutions has been developed. Thallous ions are determined using oxidative detection at a platinum electrode in a sulphuric acid‐formic acid solution. In the presence of thallic ions, iiradiation of the solution with UV light induces the reduction of Tl(III) to Tl(I) which is subsequently detected as described above. Under these conditions total thallium is determined. Irradiation of the flowing solution is carried out within the detector flow cell.
Automated system for on‐line adsorptive stripping voltammetric monitoring of trace levels of uranium
Authors: Wang Joseph , Setiadji Rossi , Chen Liang , Lu Jianmin , Morton Stephen G. 
Published: May 2005

AbstractAn automated system for on‐line monitoring of trace uranium, based on a flow‐through adsorptive stripping operation, is described. The on‐line formation of the uranium‐oxine complex is followed by its adsorptive accumulation and voltammetric quantitation at the downstream working electrode. About 10–60 runs can be made every hour with high reproducibility (RSD of 3–5%) and a detection limit of 0.7 μg/L. The dependence of the peak current on different experimental variables is reported. The sequence of events involved in the adsorptive stripping voltammetric cycle is controlled by a computer. Analogous on‐line monitoring of chromium (VI) are also reported with 36 runs/h (2.1% RSD), and detection limit of 1.5 μg/L. The system holds great promise for field‐based operation.
Amount adsorbed in adsorption voltammetry. Part 2. Amount adsorbed in the adsorption accumulation at a symmetric spherical electrode during the rest period
Authors: Jin Wenrui , Hou Yongchun , Yan Changtai , Wang Jianyan , Sun Changlin 
Published: May 2005

AbstractThe equation for the amount absorbed in adsorptive accumulation at a symmetric spherical electrode, during the rest period (under strong adsorption conditions) has been derived:
equation image
.The equation has been verified experimentally. The equation for the total amount adsorbed in adsorption voltammetry at a symmetric spherical electrode is
equation image
.
Development of an amperometric assay for the determination of reduced glutathione, using glutathione peroxidase and screen‐printed carbon electrodes chemically modified with cobalt phthalocyanine
Authors: Wring Stephen A. , Hart John P. , Birch Brian J. 
Published: May 2005

AbstractThe systematic characterization and optimization of bovine erythrocyte glutathione peroxidase is described, together with its application in an assay employing amperometry in stirred solutions for the determination of endogenous levels of reduced glutathione (GSH). Initial studies employed UV spectroscopy, cyclic voltammetry, and amperometry in stirred solutions (to construct hydrodynamic voltammograms) for several investigations including the selection of a suitable hydroperoxide second substrate, the investigation of solution conditions on the enzyme reaction rate, and reconstituted enzyme stability. Subsequently, amperometry in stirred solutions was used to monitor the enzyme‐catalyzed rate of GSH oxidation and to construct calibration plots over the concentration range 10 to 50 μM (corresponding to normal circulating GSH levels after the envisaged sample preparation step consisting of a simple twenty fold dilution of whole blood). Enzyme selectivity studies were performed using several potential physiological interferents and selected pharmaceuticals that may be encountered in the circulation of patients being treated for rheumatoid arthritis. The coefficient of variation for the enzyme linked amperometric assay was 7.28% (n = 5) for solutions containing 40 μM GSH.
A comparative study of the cylindrical wire, thin‐layer, and wall‐jet detector cells for the deterrnination of inorganic arsenic by ion exclusion chromatography with constant and pulsed amperometric detection
Authors: Stojanovic R. S. , Bond A. M. , Butler E. C. V. 
Published: May 2005

AbstractAn ion chromatographic method for the separation and determination of As(III) empolying both constant and pulsed potential amperometric detection at platinum electrodes has been compared using cylindrical wire, thin layer, and wall‐jet flow cell detectors. Operational parameters such as limit of detection, linear dynamic range, stability, reproducibility, and flow rate dependence are reported for each detector cell. The different detector designs have features which make them individually appealing, depending on the type of application being considered and which operational parameter is most important. However, the limit of detection with the wall‐jet electrode of 1 × 10−9 M is superior to the other electrode designs (this may not necessarily be the case for other analytes) and makes this the preferred method for the determination of arsenic in bottled mineral water. Additionally, a lower limit of detection is achieved with constant potential amperometric detection than is the case with pulsed potential amperometric detection, which suggests that pulsed methods may not be advantageous for the detection of species at potentials where a large background current is exhibited at very positive potentials as required for the determination of arsenic.
The number of components in noisy data from a swept‐potential electrochemical detector
Authors: Msimanga Huggins Z. , Sturrock Peter E. 
Published: May 2005

AbstractExperimental data obtained from a conventional HPLC using a swept‐potential electrochemical detector are analyzed for the number of components present under varying conditions of signal‐to‐noise (S/N) ratios. The autocorrelation, multiple determination, and single‐vector uniqueness test functions are evaluated under low S/N conditions, and also tested on Fourier‐smoothed data. The autocorrelation and multiple determination functions give good predictions down to the S/N ratio of 2.4. Below this value the autocorrelation function gives fewer counts of the components than expected as the components signal becomes buried in the background noise. On the other hand, the multiple determination function gives too many counts of the components actually present. The single‐vector uniqueness test function proves to be superior to the other two. Its predictions are more consistent even at S/N ratios lower than 2.4 Data smoothing significantly improves the performance of all three functions.
Sensitive yeast bioelectrode to L‐lactate
Authors: Kulys Juozas , Wang Lizhong , Razumas Valdemaras 
Published: May 2005

AbstractAmperometric L‐lactate bioelectrodes based on carbon paste chemically modified with yeast Hansenula anomala and mediators are described. The bioelectrodes acted over a potential range at 0.05 – 0.3 V (vs SCE), the sensitivity was 14 – 116 μM−1 cm−2 and optimum pH was at 7.6 – 7.7. The apparent Michaelis constant for the calibration curves of bioelectrodes was different for mediators and varied in the range from 1.3 to 18.9 mM of L‐lactate. The bioelectrode was insensitive to glucose and ethanol. The bioelectrode's response to ascorbic acid was 1.4% at the normal physiological level of vitamin C and L‐lactate in blood. The bioelectrode was used for L‐lactate determination in serum, and remained stable for more than 2 months. The biocatalytic action of the cytochrome b2 in yeast was suggested.
Differential pulse anodic stripping voltammetric determination of trace bismuth in minerals with nafion mercury film modified electrode
Authors: Liu Kuai‐Zhi , Wu Qing‐Gro 
Published: May 2005

AbstractAn electrode for the differential pulse anodic stripping voltammetric determination of trace bismuth in mineral has been made by coating glassy carbon with Nafion. The sensitivity is enhanced by the ion‐exchange character of the Nafion film. A detection limit of 1 × 10−11 M has been obtained after electrodeposition for 16 min. The overlapping interference of Sb is addressed successfully. The method is sensitive, simple, and relatively rapid, with good reproducibility.
Determination of mercury on a carbon paste electrode modified with humic acid
Authors: Navrátilová Zuzana , Kula Petr 
Published: May 2005

AbstractThe binding of Hg(II) with humic acid, incorporated into the carbon paste electrode, was verified. This modified humic acid electrode was used for the trace determination of Hg(II). The differential‐pulse voltammetry on the electrode modified with humic acid yielded good performance over the concentration range 5 × 10−8–5 × 10−7 M Hg(II). Only Cu(II) interferes with the determination.
Voltammetric study of the oxine‐based extractant Kelex 100
Authors: Citores M. J. , Alonso R. M. , Fernández L. A. 
Published: May 2005

AbstractThe electroanalytical study of the behavior of 7‐(1′‐vinyl‐3′,3′,5′,5′‐tetramethylhexyl)‐8‐quinolinol, the active component of the commercial extractant Kelex 100 (Ashland Chemicals), at a glassy carbon electrode has been carried out using different voltammetric techniques. The compound is oxidized giving rise to a voltammetric peak in the pH range 1.03–7.27. The plot of the variation Ep versus pH shows two straight lines intercepting at 3.46, which corresponds to the pKai value of the component. The oxidation process of the compound is irreversible (ān = 1.32) and predominantly diffusion controlled, although with an important adsorptive component. The electrode process can be attributed to the oxidation of the hydroxyl group of the quinolinic ring. A voltammetric method for the determination of the extractant has been developed.
Amperometric response of mediating layers on electrode surfaces to Gaussian concentration profiles in flowing streams
Authors: Cassidy John F. , Breen William , McGee Anthony , Vos Johannes G. , Lyons Michael E. G. 
Published: May 2005

AbstractA model for a layer, containing catalytic centers, coated on an electrode and used for the mediation of analyte in a flowing stream is proposed and solved. The model applies to a situation of a Gaussian concentration profile of analyte impinging on the outer edge of the mediating layer. It was found that the important parameters that limit the current magnitude are the diffusion coefficient of the analyte through the layer, the effective electron diffusion coefficient through the layer and the rate of reaction between the mediator and the analyte. On evaluation of literature data, it was found that layers, high catalyst loading and with high rates of electron exchange, lead to linear peak current height versus concentration plots.
Potentiometric anion response of poly (tetrakis(p‐aminophenyl)porphyrin) film‐modified electrodes
Authors: Kliza Dennis M. , Meyerhoff Mark E. 
Published: May 2005

AbstractThe potentiometric response to anions of glassy carbon electrodes coated with thin unmetallated poly(tetrakis(p‐aminophenyl)porphyrin) (poly(H2(p‐TAPP))) films is examined. The polymer films are introduced onto the glassy carbon surface by constant‐potential anodic electrolysis of the porphyrin monomer from a solution of dichloromethane containing a quaternary ammonium perchlorate salt. The thickness of the film is the controlled by the electrodeposition time. Oxidized poly(porphyrin) modified electrodes exhibit near Nernstian response to iodide in the concentration range of 5 × 10−5 – 1 × 10−1 M with significant selectivity over a wide range of other anions tested. The mechanism of the electrode's iodide ion response is considered in light of its response to other redox‐active anions, and a recent literature report describing the selective iodide response of electrodes coated with electropolymerized poly(3‐methylthiophene) films. Spectroelectrochemical studies with poly(porphyrin)‐modified tin oxide electrodes are used to confirm the redox‐type response mechanism of the sensors toward iodide. The analytical limitations of using such polymer film‐modified electrodes for potentiometric ion sensing are discussed.
Mediated micro‐glucose sensors using 2 μm platinum electrodes
Authors: Yokoyama Kenji , Nakajima Kenji , Uchiyama Shunichi , Suzuki Shuichi , Suzuki Masayasu , Takeuchi Toshifumi , Tamiya Eiichi , Karube Isao 
Published: May 2005

AbstractGlucose‐oxidase (GOD) and glucose‐dehydrogenase (GDH) immobilized cylindrical microelectrodes were fabricated, and their characteristics were evaluated by using 1,4‐benzoquinone and ferricyanide as electron mediators, respectively. Each enzyme was immobilized in a photocrosslinkable polymer on a cylindrical microelectrode of 2 μm diameter. A linear range in the calibration plot of the GOD‐based micro‐glucose sensor was observed to be wider than that obtained using a disk electrode of 1 mm diameter. The mediated response of the 2 μm glucose sensor was compared with the response resulting from hydrogen peroxide detection. This result showed that a higher response and a wider linear range were observed at a highly concentrated mediator. For the GDH‐immobilized 2 μm microelectrode, a much higher response was obtained when not only ferricyanide but also diaphorase were employed to reoxidize NADH produced by the enzyme reaction of GDH. The GDH‐based micro‐glucose sensor was found to be unaffected by dissolved oxygen concentration.
Nafion‐coated carbon fiber for acetylcholine and choline sensors
Authors: Navera Eriberta Nepomuceno , Suzuki Masayasu , Tamiya Eiichi , Takeuchi Toshifumi , Karube Isao 
Published: May 2005

AbstractA major improvement in the selectivity of carbon fiber microelectrodes for acetylcholine (Ach) and choline (Ch) as cationic amines is described. The electrodes are coated with Nafion, a perfluorosulfonated polymer. This coating is practically impermeable to ascorbic acid (AA) and anionic biogenic amine metabolites. Nafion‐coated fiber was characterized by cyclic voltammetry (CV). Selectivity and the dynamic range of these coated electrodes were evaluated using amperometric determination at a fixed potential of 1.2 V. The esterase activity was determined using choline sensor, and the relative slope values showed a fast response between 1 and 3 minutes. Calibration plots for Ach and choline showed a linearity range between 0.1 and 3 mM, with an increase of two orders of magnitude better than the previously used PVA‐SbQ membrane. No response was obtained between 0.1 and 0.3 mM of AA conc. The procedure, in preparing this type of coated electrodes, indicates some attractive perspectives for its use, especially for in vivo monitoring.