bluuebunny/crossref_metadata_2025_split huggingface dataset:
Needle‐type glucose biosensor with an electrochemically codeposited enzyme in a platinum black matrix
Authors: Abdel‐Humid Ihab , Atanasov Plamen , Wilkins Ebtisam 
Published: May 2005

AbstractIn this study we report the development of a needle‐type glucose biosensor for the management of hemorrhagic shock. The immobilization technique depends on the electrophoretic deposition of the glucose oxidase enzyme in an electrochemically grown platinum black matrix. The sensor was coated with Nafion to decrease the effect of interferents. Preliminary tests were carried out to evaluate the sensor performance in vitro. These tests included the measurement of glucose levels in buffer solutions containing various potential physiological interferents, as well as in bovine serum. The preliminary results show the sensor to have inearity up to 33 mM and a diminished response to interferents. The advantages of this technique are its simplicity and high controllability.
Potentiometric potassium selectivity of polymer membrane electrodes prepared with organo‐phosphine ligands
Authors: Saleh M. B. , Taha F. , Aof G. S. 
Published: May 2005

AbstractPotassium ion‐selective electrodes based on a new type of phosphine oxide compounds were prepared. The electrode based on tert‐butyl‐3‐p‐tolyl phosphine oxide cyclohexene gave a linear response with a Nernstian slope of 60 mV per decade within the concentration range 10−1–10−5 M KCl. The electrode exhibited good selectivity for potassium with respect to alkali, alkaline earth and other metal ions. The content of potassium ion in some plant and soil samples was determined using the prepared electrode and flame photometry. The electrode gave results very similar to those of flame photometry. Routine use of ion‐selective potentiometry for potassium determination can thus be recommended for plant and soil analysis.
Simultaneous voltammetric determination of antimony, copper, lead, and tin in steel using a hydrochloric acid–isopropanolic medium
Authors: Hofbauerová Helena , Labuda Ján , Fišera Miroslav , Vaníčková Mária 
Published: May 2005

AbstractThe problem of overlapping peaks of antimony and copper, as well as lead and tin, was solved by performing differential pulse anodic stripping voltammetry and differential pulse voltammetry in a 1.8 M HCl–80% isopropanol supporting electrolyte media. Arsenic (III) does not interfere in the alcoholic medium and it can be determined by differential pulse voltammetry in acidic aqueous solution. The procedure has been applied to the determination of trace metals in alloy steel.
Ferrocene‐containing polymers as electron transfer mediators in carbon paste electrodes modified with PQQ‐dependent aldose dehydrogenase
Authors: Smolander Maria , Gorton Lo , Lee Hung Sui , Skotheim Terje , Lan Hsing‐Lin 
Published: May 2005

AbstractThe aim of this work was to improve an aldose‐detecting biosensor based on quinoprotein aldose dehydrogenase (ALDH). Polymer‐bound ferrocene derivatives with four different structures were studied as electron transfer mediators between the coenzyme of ALDH, pyrroloquinoline qninone (PQQ), and the conducting electrode material. The ferrocene polymers were mixed into carbon paste, which was used for the preparation of aldose‐detecting electrodes by immobilizing ALDH on the carbon paste surface by adsorption. The current responses of the ferrocene polymer modified electrodes were studied and the effect of the polymer structure on the response was examined. The electrodes modified with all four polymers showed maximum response at the working potential around 300 mV (vs. Ag/AgCl). The operational stability of the ferrocene polymer modified electrodes was better than that of corresponding dimethylferrocene modified electrodes. The ferrocene polymer modified electrodes seemed to be suitable for the measurement of real samples.
A model of non‐nernstian response in the determination of aluminum ions by indirect potentiometry
Authors: Ngila J. Catherine , Alexander Peter W. , Hibbert D. Brynn 
Published: May 2005

AbstractFlow analysis data of the response of an aluminum wire electrode to fluoride into which Al3+ is added is modeled assuming a logarithmic response of the electrode to F− and reaction of F− with aluminum ions to give a series of complexes [AlFq](3−q)+ when q = 1,2,3,4,5,6. The solutions were maintained at pH 5.0 with acetic acid/acetate buffer. Other species modeled were the hydroxo complexes of aluminum [Alm(OH)n](3m−n)+ when m = 1, n = 1,2,3,4; m = 2, n = 2; m = 3, n = 4; m = 13, n = 32, and the acetate complex [Al2(OH)2OAc]3+. Protonation of F− to HF and HF was also considered. Three coefficients were required to fit the data, a constant and slope of the response of the electrode to free fluoride and a dispersion factor in the flow analysis. Published stability constants were used and no account was taken of ionic strength. The model may be used to predict optimum analysis conditions given an approximate aluminum concentration.
Stripping voltammetry at microdisk composite electrode assembly
Authors: Wang Joseph , Armalis Saulius 
Published: May 2005

AbstractThe attractive stripping voltammetric performance of the recently developed RAM electrode, consisting of 3.5‐μm radius carbon microdisks embedded in epoxy resin, is described. The microdisk dimensions and interdisk spacings of the RAM surface lead to nonlinear diffusional flux and offer efficient metal deposition from quiescent samples. Coupled with large “collective” stripping currents, a wide potential window and a low background current, the new electrode yields low detection limit (e.g., 0.3 μg/L lead and cadmium for 2‐min deposition) and good precision (2.1–2.3% RSD, n = 15). Assays of drinking water are used for illustration.
Investigations on adsorption potentiometry. Part X: Derivative adsorption chronopotentiometry of chromium(III)
Authors: Jin Wenrui , Jia Xianglan , Lu Jianmin 
Published: May 2005

AbstractThe study concerns a very sensitive electroanalytical method, based on derivative chronopotentiometry of the chromium(III) complex with 2‐(5′‐bromo‐2′‐pyridylazo)‐5‐diethyl aminophenol (5‐Br‐PADAP) accumulated adsorptively on the surface of a hanging mercury drop electrode. The detection limit is 6 × 10−11 mol/L for a preconcentration time of 6 min. The mechanism of the electrode reaction has been investigated in detail.
Solid state electrochemical characterization of tungsten oxides and related heteropoly‐12‐tungstic acid single crystals
Authors: Karwowska Beata , Kulesza Pawel J. 
Published: May 2005

AbstractTungsten oxide, dihydrate (WO3 · 2H2O) and monohydrate (WO3 · H2O) pastes, as well as silico‐12‐tungstic acid single crystals (H4SiW12O40 · 31H2O) have been subjected to electrochemical investigations in solid‐state, i.e., in the absence of deliberately added external liquid electrolyte phase. Mobile protons, which exist in WO3 · H2O and H4SiW12O40 · 31H2O (but not in WO3 · H2O) bulk materials, are capable to support electron transport between WVI, V mixed‐valence sites (generated in the systems upon partial reduction). Silicotungstic acid can be reduced reversibly to heteropolyblue (HzSiW12O, where z is 1, 2 or 4), which is analogous to hydrogen tungsten oxide bronze (HxWO3, 0 < x < 0.35), i.e., blue nonstoichiometric WVI, V oxide. The values of z = 4 and x ≈ 0.35 are approximately equivalent because each silicotungstate structure consists of twelve WO3 surrounding the SiO4 group. There are similarities in the voltammetric behaviors of WO3 · 2H2O and H4SiW12O40 · 31H2O. Quantitative characterization of H4SiW12O40 · 31H2O has been achieved with the use of a carbon fiber ultramicrodisk electrode. Upon injection of four electrons per silicotungstate unit, the maximum concentration (6–7 M) of WVI, V redox sites is generated within the diffusional flux in the crystal. An effective diffusion coefficient for charge propagation is high (3–4 × 10−7 cm2 s−1), Injection of more electrons (z > 4) leads to irreversible redox transitions in the system. Silico‐12‐tungstic acid single crystal can be considered as a bulk, molecular, model for redox reactions in catalytic tungsten oxides.
Total anodic voltammetric waves of undiluted dimethylsulfoxide at Pt microelectrodes
Authors: Koncka Marta , Stojek Zbigniew 
Published: May 2005

AbstractAt least two total anodic voltammetric waves of DMSO, or voltammetric waves of undiluted DMSO, can be obtained at platinum microelectrodes. These waves are of roughly equal height. Linear scan‐ and reverse pulse voltammograms indicate that the first wave is a one‐electron wave. After the addition of water the formation of dimethylsulfone is possible and therefore a part of DMSO equivalent to water concentration is oxidized via the two‐electron process. This results in an increase of the wave height and can be used for analytical purposes. To determine water content, by using this increase, its concentration in DMSO should be higher than 0.1 mol/L.
Application of DPASV to the study of heavy metal complexation in colloidal latex dispersions
Authors: Díaz‐Cruz José M. , Wonders Jeannette H. A. M. , van Leeuwen Herman P. 
Published: May 2005

AbstractDifferential pulse anodic stripping voltammetry (DPASV) was applied to the study of the binding of ZnII, CdII and PbII by two kinds of polystyrene latex particles at different pH values and at different electrolyte concentrations. For the calculation of stability constants, the criterion of consistency between current and potential data was applied. For CdII and PbII, the application of DPASV yields qualitatively good results (in agreement with those previously found by DPP). However, from a quantitative point of view, the consistency criterion often reduces the applicability of the technique to quite narrow pH ranges, which increases the error in some calculations. In the case of ZnII, certain anomalies were found, rendering quantitative considerations impossible.
A new conducting polymer glucose sensor based on polythianaphthene
Authors: Compagnone Dario , Federici Giorgio , Bannister Joe V. 
Published: May 2005

AbstractA glucose biosensor has been developed by entrapment of glucose oxidase in a polythianaphthene film formed onto a platinum surface. Glucose has been measured by H2O2 detection at +400 mV (vs. SCE). Electrochemical kinetic constants for the enzyme electrode have been calculated and indicated that in the unsaturated region the rate limiting step is the diffusion of the substrate through the polymer. The biosensor exhibited a linear response in the range 0.05–7.4 mmol/L with a response time of 30–60s and a relative standard deviation of 5.4%. The presence of the film onto the electrode prevents the oxidation of interfering agents such as ascorbic and uric acid. The use of additional polycarbonate membranes onto the electrode surface extended the linearity of the response allowing the probe to be used in blood glucose analysis, The amount of glucose in two control sera was measured using the biosensor. Results correlated well with the glucose nominal values.
The voltammetry of neuropeptides containing L‐tyrosine
Authors: Reynolds Norman C. , Kissela Brett M. , Fleming Lynda H. 
Published: May 2005

AbstractNeuropeptides containing an N‐terminal tyrosine are irreversibly oxidized on glassy carbon electrodes using scan rates from 0.020 to 0.500 V/s. Despite variations in peptide length and amino acid composition from tyrosine to α‐neoendorphin 1–10, peak potentials occurred in a relatively narrow range from +0.925 V to +0.971 V (vs. Ag/AgCl). An inverse linear relationship of Ep vs. pH with a slope near −59 mV/pH unit suggests that the oxidation involves a one electron oxidation and a single proton transfer similar to the oxidation of simple para‐substituted phenols. Linear slopes between 0.790 and 0.933 of log Ip vs. log v suggest that surface processes contribute to the voltammetry on glassy carbon.
Microband electrodes of ideal and nonideal geometries: AC impedance spectroscopy
Authors: Alden John A. , Compton Richard G. 
Published: May 2005

AbstractThe AC impedance behavior of microband electrode geometries which deviate from the ideal is derived via numerical modelling of the chronoamperometric response under diffusion‐only conditions. Specifically attention is given to four electrode shapes in addition to the ideal microband geometry: elevated microband electrodes (with conducting supporting sides), recessed microband electrodes (with insulating pit walls), platform electrodes (with insulating supporting sides) and, for the purposes of comparison, a hypothetical line electrode without any support which permits diffusional mass transport to both sides of the infinitesimally thin electrode. Simple analytical expressions are established for the frequency dependence of the AC impedance in each case.
Derivative chronopotentiometric stripping analysis of insulin
Authors: Honeychurch Michael J. , Ridd Michael J. 
Published: May 2005

AbstractPorcine insulin was analyzed in the presence of dissolved oxygen by constant current stripping analysis (CCSA) and potentiometric stripping analysis (PSA). The CCSA analysis involves the constant current reduction of mercuric insulin thiolate following its potentiostatic accumulation on a hanging mercury drop electrode. The CCSA response was quantitatively enhanced in the presence of dissolved oxygen. The PSA analysis involves the oxidation, by dissolved oxygen, of sulfhydryl groups in reduced insulin following its accumulation on the HMDE at −900mV (vs. SCE).
Anion selectivities of membranes based on HgII complexes of calix[4]arene derivatives
Authors: Wróblewski Wojciech , Malinowska Elżbieta , Brzózka Zbigniew 
Published: May 2005

AbstractAnion selectivities of membranes based on cationic complexes of thioamide calix[4]arene derivatives are presented for the first time. HgII complexes of thioamide derivatives of calix[4]arene were applied to design perchlorate‐selective ISEs which show linear responses in the range 1–5 of pClO4 with a slope of 56.5mV decade −1. The highest selectivity over other anions (except iodides) and optimum performances of electrodes were obtained for a 0.01 M solution of HgII as an internal electrolyte.
The nature of voltammetric waves of copper complexes with dimethylglyoxime in ammonia and borate buffer solutions
Authors: Bobrowski Andrzej 
Published: May 2005

AbstractThe voltammetric and adsorptive characteristics of the Cu‐DMG complexes in a wide range of Cu concentration (from 5 × 10−8 M to 1 × 10−3 M) have been investigated in ammonia and borate buffer. Evaluation of the electrode process included the examination of the effect of Cu, DMG, buffers, ethanol and Triton X100 concentration, buffer capacity and ionic strength, pH and instrumental parameters. The adsorption phenomena were observed by direct current, linear scan, pulse and alternating current polarography and voltammetry. At high Cu concentration the additional effects such as spikes on the pulse and linear scan voltammetric curves as well as maxima and erratic behavior on the direct current polarograms were observed. From the voltammetric and the potentiostatic transient studies it has been found that these effects are caused by the nucleation and condensation processes. From the bulk electrolysis and microelectrolysis results it follows that the Cu‐DMG complex is reduced with participation of two electrons and no proof has been found that in the presence of a Cu‐DMG complex a catalytic hydrogen wave is formed. The adsorptive properties of the Cu‐DMG complex can be utilized for sensitive determination of Cu traces (from 1 × 10−7 M to ca. 1 × 10−5M Cu) or for simultaneous determination of Cu, Ni and Co by differential pulse polarography or linear fast sweep polarography.
Development and optimization of a solid composite tyrosinase biosensor for phenol detection in flow injection systems
Authors: Mareikelutz E. S. , Dominguez Elena 
Published: May 2005

AbstractBulk‐modified epoxy‐graphite tyrosinase biosensors were fabricated by four different procedures. The influence of these fabrication procedures on the analytical performance of the enzyme electrode in an amperometric wall‐jet flow cell has been studied. The bioprobe performance is assessed by cyclic voltammetry. Higher current densities and narrower peaks were obtained when the enzyme was introduced in the dry state into the epoxy‐graphite material, instead of introducing it previously dissolved in the buffer. In the F1 system responses of 11.79 μA cm−2 and 1.43 μA cm−2 are then obtained for catechol and phenol respectively for 50 μL injections of 20 μM solutions. Moreover, if gold/palladium is introduced into the epoxy‐graphite, a further increase in current is achieved resulting in 27.70μA cm−2 and 4.90μA cm−2for catechol and phenol, respectively. This biosensor can operate in aqueous as well as in mixed aqueous‐organic environments.
Amperometric determination of peroxides by glassy carbon electrodes modified with copper‐phenanthroline complexes
Authors: Toniolo Rosanna , Comisso Nicola , Bontempelli Gino , Schiavon Gilberto 
Published: May 2005

AbstractAn amperometric sensor is described for the determination of peroxides in both aqueous and organic media. It consists of a rotating glassy carbon electrode modified by coating first with a thin film of a perfluorinated anionic exchanger (Tosflex) and then by immobilizing on this substrate the mixed‐ligand copper complex [CuL2]2+ with 1, 10‐phenanthroline and bathophenanthroline (i.e., 1, 10‐phenanthroline containing two phenyl‐sulfonic groups as substituents in the positions 4 and 7), thanks to the bonds formed between the −NR+3 cationic groups of the Tosflex coating film and the −SO−3 anionic groups present in the latter ligand. The modified electrode, which is rather stable with time and can be easily restored, permits detection of peroxides by their reduction at less cathodic potentials than at an unmodified electrode surface. It shows enhanced sensitivity in a variety of media (water, ethanol and ethanol‐toluene 60/40 v./v.) which were investigated in view of their ability, on the whole, to dissolve peroxides originally present in different natural samples. Its satisfactory performance, which is unaffected by the presence of oxygen in the sample, in all the media studied is reported for hydrogen peroxide and tert‐butyl hydroperoxide in terms of detection limits, dynamic ranges and response time. Its application to the direct determination of peroxides in some cereal oils was also attempted and the results found are compared with those obtained by conventional methods.
Measurement of liquid junction potentials in strongly alkaline solutions
Authors: Norkus Eugenijus , Vaškelis Algirdas 
Published: May 2005

AbstractThe values of liquid junction potentials (Elj) between the saturated KCl solution in Ag/AgCl electrode and NaOH solutions (0.8–3.0 mol/L), as well as between NaOH solutions of different concentrations were determined at 20°C using Hg/HgO electrodes. The Elj value obtained can be as high as 20mV and its calculation by Henderson equation is not accurate enough.
A water‐soluble tetramethylbenzidine‐2‐hydroxypropyl‐β‐cyclodextrin inclusion complex as an efficient mediator for oxidoreductases
Authors: Cattaneo Maurice V. , Luong John H. T. 
Published: May 2005

AbstractA water soluble 3,5,3′,5′‐tetramethylbenzidine‐2‐hydroxypropyl‐β‐cyclodextrin (TMB‐hpβCyD) inclusion complex was demonstrated for the first time as an efficient mediator for glucose oxidase, xanthine oxidase and glutamate dehydrogenase. At pH 5, the cyclic voltammogram of the TMB‐hpβCyD complex exhibited two reversible oxidation waves with potential peak values (Epa) of 384 mV (TMB → TMB+·) and 496mV (TMB+· → TMB2+) at a glassy carbon electrode (vs. Ag/AgCl). The Epa value of the former was pH‐independent, whereas that of the latter was strongly pH dependent. However, at pH 7 the inclusion complex exhibited only one reversible oxidation wave with Epa of 396 mV. Based on cyclic voltammetric measurements, the second rate constant (k) for the TMB+ (glucose oxidase) reaction was determined as 6.7 × 105 M−1s−1 which compares favorably with that of ferrocene (2.6 × 104 M−1s−1), one of the most common mediators. The inclusion complex was then investigated for bioelectrocatalysis at membrane electrodes of glucose oxidase and xanthine oxidase. The response of the hypoxanthine electrode was linear up to 40μM; its sensitivity was 2.8 μA mM−1 and a response time was smaller than 2 min. A similar response time was also observed for the glucose electrode, however, the linear range and sensitivity of the glucose electrode were 0–3 mM and 0.6 μA mM−1, respectively. The capability of TMB+˙ to oxidize NADH formed from a glutamate dehydrogenase:NAD/glutamate reaction, was also demonstrated, as illustrated by a well‐defined catalytic wave for NADH oxidation.
Flow injection amperometric detection of ammonia using a polypyrrole‐modified electrode and its application in urea and creatinine biosensors
Authors: Trojanowicz Marek , Lewenstam Andrzej , Krawczyk Tadeusz Krawczyński Vel , Lähdesmäki Ilkka , Szczepek Wojciech 
Published: May 2005

AbstractThe interaction of unprotonated ammonia molecules with polypyrrole (PPy) is employed for the amperometric detection of ammonia with the use of an anodically polarized platinum electrode modified with PPy as the working electrode. The polymer was obtained by electropolymerization in potentiostatic conditions from aqueous solutions. Chloride was found to be the most suitable dopant for PPy from several dopants studied. Satisfactory dynamic characteristics of detection permit its application to the determination of ammonia in a flow injection system up to 100 μM of analyte with a detection limit of 0.6 μM. Such a detector of ammonia was also employed as the internal detector in amperometric biosensors for urea and creatinine by the immoblization in a different way at the PPy surface of urease and creatinine iminohydrolase, respectively. An amperometric biosensor of very low sensitivity was obtained by urease entrapment in the PPy layer during the electropolymerization. The urea membrane biosensor was successfully applied in the determination of urea in human blood samples. On the basis of results of elemental analysis, UV and IR spectroscopy some suggestions are presented about the mechanism of the interaction between PPy and ammonia and about the anodic electrode process occurring in the amperometric detection of ammonia.
CuII‐poly (dithiooxamide) film coated anion selective electrode
Authors: Gong Young‐Tae , Won Mi‐Sook , Shim Yoon‐Bo , Park Su‐Moon 
Published: May 2005

AbstractElectrochemical deposition of a solid state anion selective membrane for thiocyanate and thiosulfate ions has been made from a 0.050 M dithiooxamide solution in 0.10 M sulfuric acid on a copper coated platinum electrode and its performance evaluated. The solid state membrane electrode displays excellent linearities with slopes of 59.2 ± 0.5 and 98.6 ± 0.6mV/decade and detection limits of 7 × 10−7 and 4 × 10−6 M for SCN‐ and S2O, respectively, high selectivity over other anions, and response time of about 6 s. The optimum pH for the electrode is around 6 in an acetate buffer, although it is usable in a wide pH range. The electrode was shown to be rugged and stable for at least a month and give reproducible responses if stored in an inert atmosphere.
The derivative adsorption chronopotentiometry of flavin adenine dinucleotide
Authors: Honeychurch Michael J. , Ridd Michael J. 
Published: May 2005

AbstractThe flavin adenine dinucleotide (FAD), leucoflavin adenine dinucleotide (FADH2) couple was studied by derivative adsorption chronopotentiometry at a HMDE. The theory of an EE mechanism for adsorption chronopotentiometry was developed and the semiquinone formation constant determined. Constant current stripping results at pH 7.0 were consistent with previous reports that adsorbed FAD was reduced via a stable semiquinone intermediate in two reversible one‐electron transfers (EE mechanism). Potentiometric stripping analysis was also carried out in which the FAD was accumulated as FADH2 on the HMDE at a reducing potential. The FADH2 was subsequently oxidized by dissolved oxygen. This reaction was also found to fit the EE model.