bluuebunny/crossref_metadata_2025_split huggingface dataset:
Amperometric glucose biosensors based on an osmium (2+/3+) redox polymer‐mediated electron transfer at carbon paste electrodes
Authors: Pravda Miloslav , Adeyoju Olubunmi , Iwuoha Emmanuel I. , Vos Johannes G. , Smyth Malcolm R. , Vytras Karel 
Published: May 2005

AbstractFour glucose sensors have been developed by modifying carbon paste electrodes with glucose oxidase as a biocomponent and a conducting redox osmium‐polymer as the mediating compound. The enzyme was immobilized by crosslinking with glutaraldehyde and bovine serum albumin in three modifications of electrodes and physical adsorption in one electrode. The optimal concentrations of the modifying compounds were determined and the response of the sensors to 2–20 mM glucose were characterized. The influence of pH, temperature, interferences, and storage on the responses of the sensors were investigated.
Biosensing of tyrosinase inhibitors in nonaqueous solvents
Authors: Stancik Lubor , Macholán Lumír , Scheller Frieder 
Published: May 2005

AbstractAn amperometric biosensor based on a Clark oxygen electrode coupled with a biocatalytic layer containing tyrosinase has been developed for measurement in nonaqueous solvents. Glass filter paper was soaked with the enzyme and fixed on top of the electrode by a dialysis membrane. Thiourea derivatives were detected in hexane by evaluating the decrease in the response towards phenol. This method was fast and highly sensitive with detection limits in the range of 13–181 nM depending on the structure of the inhibitor compounds. The response time was up to 10min and depended on the inhibitor's structure. The mechanism of inhibition is discussed using kinetic parameters.
Electrocatalysis with an acetylcholinesterase immobilized graphite electrode
Authors: Stoytcheva Margarita 
Published: May 2005

AbstractOn the basis of the acetylthiocholine iodide hydrolysis, catalyzed by the enzyme acetylcholinesterase and leading to an electroactive product, an amperometric sensor is developed. An electrochemically modified graphite electrode is used, with acetylcholinesterase covalently linked directly on its surface. The kinetic parameters of the enzymatic reaction, in the presence and in the absence of inhibitors, are determined using an electrochemical approach.
Study of cation transfer across the water/nitrobenzene interface facilitated by a synthetic neutral dicarboxamide
Authors: Hu Zhongmin , Zhang Weiqing , Zhao Pingsan , Qi Deyao 
Published: May 2005

AbstractThe transfer of proton, alkali, and alkaline earth metal ions across the water/nitrobenzene interface, facilitated by a synthetic neutral dicarboxamide ionophore in the nitrobenzene phase was investigated using cyclic voltammetry. The ionophore‐facilitated transfer of Li+, Ca2+, and Ba2+ ions showed cathodic current peaks, and the transfer of H+ ions apparently resulted in peaks of both anodic and cathodic currents within the potential window. The transfer process of these ions was found to be controlled by the diffusion of the ionophore in the nitrobenzene. The formation of a 1 : 1 complex for H+ and of 1 : 2 (cation to ionophore) complexes for Li+, Ca2+, and Ba2+ ions was inferred, through peak separation or the dependence of the cathodic peak potential on the logarithm of the ionophore concentration, to be involved in the transfer process. The equilibrium constants KLI,M for the exchange reaction of the ion MZ+ with the Li‐+ ionophore complex at the water/nitrobenzene interface were evaluated and correlated with the potentiometric selectivity coefficients K.
All‐solid‐state chloride‐selective electrode with poly(pyrrole) solid contact
Authors: Hulanicki Adam , Michalska Agata 
Published: May 2005

AbstractThe responses of all‐solid‐state potentiometric chloride sensors with an internal poly(pyrrole) contact and a plastic membrane with methyltridodecylammonium chloride were investigated. The influence of the poly(pyrrole) doping anion was studied. Chloride‐selective electrodes with a poly(pyrrole) solid contact were characterized by good stability. The selectivity coefficients for this electrode are slightly better than for the internal solution electrode.
The liquid–liquid micro‐interface for the amperometric detection of urea
Authors: Osborne Murray D. , Girault Hubert H. 
Published: May 2005

AbstractThe detection of the ammonium ion produced by the enzymatic action of urease on urea is investigated electrochemically by means of Facilitated ion transfer reactions at liquid–liquid micro–interfaces. The urease was used either in a dissolved form (free in aqueous solution) or immobilized onto the surface of an ammonia gas permeable membrane. The sensing structure utilizing the ammonia gas permeable membrane allowed the detection of urea from 200μM to 4mM. Thick film technology was utilized in conjunction with UV excimer laser photoablation techniques to fabricate a inicroelectrode strip sensor for the ammonium ion.
Biosensing of rapeseed glucosinolates using amperometric enzyme electrodes based on membrane‐bound glucose oxidase or tyrosinase
Authors: Stančík Lubor , Macholán Lumír , Pluháček Ivo , Scheller Frieder 
Published: May 2005

AbstractSinigrin, the β‐D‐thioglucoside of the cruciferous plant species was hydrolyzed for 15 min at pH 7 and 30°C by the enzyme myrosinase to liberate glucose and mustard oil allylisothiocyanate as aglucone. A Clark‐type pO2 sensor overlaid with a glucose oxidase + catalase membrane served for the glucose measurements, whereas the isothiocyanate component was measured (after conversion to allylthiourea) from the inhibition degree of a tyrosinase membrane/pO2 sensor. The total amounts of glucosinolates found with the glucose probe in six assorted samples of rapeseed meal and evaluated in sinigrin equivalents (13.6 −147 μmol/g) agreed with those obtained using gas chromatography as the reference. Poor agreement (results: 111.4–112.3%) was achieved when a different method of fat removal was used prior to electroanalysis. The amounts of progoitrin (not convertible to thiourea) estimated indirectly from the difference of both the glucose and the aglucone biosensor analyses were found to be in the range 6.2–103 μmol/g (44.3–83.8% of the total glucosinolates).
Simultaneous determination of lead and tin in biological and environmental materials by differential pulse cathodic voltammetry on a glassy carbon mercury film electrode
Authors: Adeloju Samuel B. O. , Pablo Fleurdelis 
Published: May 2005

AbstractA method involving a nonelectrolytic accumulation of a tin(IV)–catechol complex, followed by differential pulse cathodic voltammetric reduction of the tin‐catechol complex and the direct reduction of lead(II) ions, is described for the simultaneous determination of trace amounts of tin and lead on a glassy carbon mercury film electrode. The selective reaction of tin with catechol enables adequate resolution of its peak from the lead response. The resulting peaks which appeared at −0.39V, −0.50V and −0.66V (vs. Ag/AgCl), correspond to the reduction of SnIV, PbII and SnII, respectively. The lowest detectable concentrations in 0.10 M acetate buffer electrolyte (pH between 4.2 and 4.7) containing 5 × 10−4M catechol with an accumulation period of 300s are l.0μg L−1 and 0.5 μg L−1 for lead and tin, respectively. The linear concentration range for lead and tin in the presence of 20 μ L−1 of either element are 0–4 mg L−1 and 0‐34 μg L−1, respectively. The simultaneous determination of both elements was accomplished in solutions containing up to 4000‐fold more lead than tin. The method is successfully demonstrated for the reliable simultaneous determination of lead and tin in some biological and environmental materials.
Electrocatalysis of adsorbed Co‐cyclam at Au electrodes for nitrate reduction in concentrated alkaline solution
Authors: Ma Ling , Li Hulin 
Published: May 2005

AbstractCobalt‐cyclam, trans‐CoIII‐([14]aneN4)Cl2, was directly adsorbed on Au electrodes to form adsorbed Co‐cyclam modified electrodes. The presence of Co‐cyclam on the surface of the electrodes was determined by XPS (X‐ray photoelectron spectroscopy), differential capacity, and the voltammetric behavior of the Co‐cyclam modified electrode in 3 M NaOH solution. The electrocatalytic activity of this modified electrode towards nitrate reduction was examined in 3M NaOH solution, and a comparison of the electrocatalytic activities of the Co‐cyclam modified electrode and the Co‐cyclam incorporated Nafion film modified Au electrode is discussed. The results showed that the new modified electrode exhibited a more efficient catalytic effect.
A simple method for catalyst immobilization on electrode surfaces
Authors: De Smet Steven , Cassidy John , McCormac Tim , Maes Noel A. 
Published: May 2005

AbstractCatalytic layers of a cobalt tetraphenylporphyrin/polystyrene composite coated on a glassy carbon electrode are shown to allow the reduction of oxygen at less negative potentials than at the bare electrode. When this layer was overcoated with a glucose oxidase (GOD) layer, the glucose could be determined under aerobic conditions. A similar ferrocene/polystyrene composite overcoated with a glucose oxidase layer allowed the determination of glucose under anaerobic conditions.
Novel application of potentiometric microelectrodes: Scanning potentiometric microscopy
Authors: Tóth Klára , Nagy Géza , Wei Chang , Bard Allen J. 
Published: May 2005

AbstractThe techniques for the fabrication of a new type of potentiometric scanning electrochemical microscopic tip are described. Ion‐concentration profiles generated in electrochemical model experiments, by enzyme catalyzed reaction and corrosion processes, as well as by the electrochemical reduction of zinc ions, have been studied and followed with micropipet ion‐selective electrode based probe microscopy. Efforts devoted to developing methods to measure scanning tip‐to‐target distances are surveyed.
Applicability of the phase boundary potential model to the mechanistic understanding of solvent polymeric membrane‐based ion‐selective electrodes
Authors: Bakker Eric , Nägele Matthias , Schaller Ulrich , Pretsch Ernö 
Published: May 2005

AbstractRecent experimental evidence suggests that the equilibrium partitioning of sample ions at the sample/membrane interface is the main parameter governing the potentiometric response of polymeric membrane‐based ion‐selective electrodes (ISEs). It is shown that the response of a neutral‐carrier‐based H+‐selective electrode can be fully predicted on the basis of equilibrium concentrations measured optically within a thin organic film having the same composition as the ISE membrane. Consequently, using this simple and powerful phase boundary potential model together with mass balances and observed complex formation constants, the response and selectivity of various ISE membranes may be described. In this contribution, the most recent applications of the model are reviewed including: (1) a novel and general selectivity description, which is related to the so‐called matched potential method and clearly shows the limitations of the extended Nicolsky–Eisenman equation if ions of different charge are considered; (2) the measuring range of neutral‐carrier‐based H+‐selective ISEs, showing that previous experimental findings can now be explained by theory; (3) prediction of the influence of anionic and cationic sites on the selectivity of charged‐carrier‐based ISEs demonstrating that such ISE membranes need the incorporation of sites of the same charge type as the analyte ion to induce optimum potentiometric selectivity; and (4) the determination of the concentration of anionic impurities in poly(viny1 chloride) by measuring the influence of the anionic site concentration on the divalent/monovalent ion selectivity of a neutral‐carrier‐based ISE.
Lifetime of glass membrane electrodes: Theoretical model for the corrosion of silicate glasses
Authors: Morf Werner E. 
Published: May 2005

AbstractWhile misfunctions of pH‐sensitive glass electrodes, as found in routine work at room temperature, are usually due to coatings on the glass membrane or to clogging of the reference electrode junction, the practical lifetime of glass electrodes at elevated temperatures is often limited by a critical increase of the electrical membrane resistance, by a gradual appearance of sluggish response phenomena, by deteriorations with respect to selectivity and linear response range, and/or by the generation of asymmetry potentials. Such aging behavior has been attributed to decomposition processes that occur on the glass surfaces in contact with aqueous solutions, such as selective ion exchange of alkali and alkaline earth metal ions for hydrogen ions from the solution (leaching), congruent matrix corrosion of the entire silicate network (etching), and enrichment of nearly insoluble components at the interface. This article reports on the corrosion dynamics of different electrode glasses. The theory of ion exchange and the effects of leached layers on glass surfaces are summarized. A thermodynamic approach to corrosion kinetics, originally devised for simulating the corrosion of minerals and glasses under hydrogeochemical conditions, was adopted for modeling the matrix corrosion of silicate glasses of various compositions.
Electroanalytical and biocompatibility studies on microfabricated array sensors
Authors: Lindner Ernô , Cosofret Vasile V. , Buck Richard P. , Johnson Timothy A. , Ash R. Bruce , Neuman Michael R. , Kao Weiyuan J. , Anderson James M. 
Published: May 2005

AbstractpH, potassium and calcium ion‐selective membranes based on neutral ionophores TDDA, valinomycin and ETH‐1001, respectively and immobilized in high molecular weight (HMW) and carboxylated poly(viny1 chloride) (PVC‐COOH) as well as in aliphatic polyurethane (Tecoflex) matrices with normal and reduced amounts of plasticizers were investigated with respect of their general analytical properties, biocompatibility and cellular responses. The analytical performance of the PVC‐COOH based potassium electrodes was not effected by reducing the plasticizer content from 66% (w/w) to 33% (w/w) while that of pH electrodes was significantly deteriorated at the lower plasticizer level. High molecular weight PVC and Tecoflex membranes with low plasticizer content induce less inflammatory response compared to membranes cast with high plasticizer concentrations or PVC‐COOH as matrix. o‐NPOE plasticized membranes are correlated with an increased acute, but a decireased chronic inflammatory response, when compared to membranes cast with DOS as plasticizer.
Ionophores containing ethoxylate units for ion sensing
Authors: Thomas J. D. R. 
Published: May 2005

AbstractThe role of ethoxylate‐containing molecules as ion‐selective electrode (ISE) type potentiometric sensors is illustrated by studies carried out in the author's laboratories [1]. The molecules discussed include long chain acyclic polyethoxylates, crown and bis‐crown ethers, diphenylethers of tetraethyleneglycol and tripodal type receptors. Attention is given to performance of the ISEs for alkali and alkaline earth metal ions, uranyl and organic cations. Additionally, there is some discussion of fundamentals and of the role of electrodes with membranes based on appropriate tetraphenylborates of barium complexed with polyethoxylate in the analysis and critical micelle concentration determination of nonionic polyethoxylate detergents.
Kinetic characterization of the effects of organic solvents on the performance of a peroxidase‐modified electrode in detecting peroxides, thiourea and ethylenethiourea
Authors: Adeyoju Olubunmi , Iwuoha Emmanuel I. , Smyth Malcolm R. 
Published: May 2005

AbstractHorseradish peroxidase (HRP) modified electrodes were constructed by entrapping the enzyme in an Eastman AQ 55D polymer. The biosensor detects butanone peroxide (BTP) as a substrate, and thiourea (THU) and ethylenethiourea (ETU) as HRP inhibitors. The kinetic parameters for this sensor in organic media such as Imax and K′m for BTP detection and K′i for ETU and THU detection were evaluated. The differences in the values of these parameters were explained in terms of the physico‐chemical properties of the organic reaction media. A possible solvent‐induced deviation of the biosensor behavior from Michaelis–Menten kinetics in the detection of ETU and THU was evaluated using the Hill analysis. The least deviation was observed in acetonitrile. Spectroelectrochemistry was also used to qualitatively assess solvent–HRP, BTP–HRP and inhibitor–HRP interactions.
Handling low frequency drifting background noise in data from a swept‐potential electrochemical detector
Authors: Msimanga Huggins Z. , Sturrock Peter E. 
Published: May 2005

AbstractThe quality of measurements obtained from high‐performance liquid chromatography using electrochemical detection is often obscured by both the low‐frequency drifting background noise and the high‐frequency background noise. While the quality of measurements can be greatly improved by digital filtering techniques which are capable of minimizing high‐frequency noise, these techniques are very limited in handling low‐frequency drifting background noise. A method for effectively performing background correction (the moving band method) has been developed and applied to a few chemical systems which were studied in our laboratory. The method examines each sweep (chromatograms or voltammogram) for the presence of the analyte peak. Once the peak has been detected, the base of the peak is then generated by interpolation and then refined visually by adjusting the base peak width. The generated base, along with the data points which do not contain the peaks, constitutes the background of that sweep. This background is then subtracted from the original sweep, leaving the analyte signal on a flat baseline. Before the method is applied to a sweep, high‐frequency noise is removed by fast Fourier transforms digital filtering. The moving band method is tested and evaluated using data matrices of nitrophenols and catecholamines at concentrations of about 5.0 ng/10 μL where the drifting background noise is significant. The quality of the data matrices is greatly improved due to the improved signal‐to‐noise ratios.
Sensitive adsorptive stripping voltammetric determination of xanthine and its derivatives
Authors: Shubietah Raqi M. , Zuhri Ali Z. Abu , Fogg Arnold G. 
Published: May 2005

AbstractSensitive cathodic stripping voltammetric procedures for trace determination of xanthine (I), 7‐methylxanthine (II) and 1,7‐dimethylxanthine (III) are reported. The methods are based on the accumulation of the copper(I) complexes of the compounds on the hanging mercury drop electrode. The adsorptive stripping response was evaluated with respect to accumulation time, potential, concentration, pH and other variables. Linear calibration graphs were obtained over the range from 2.0 × 10−8 to 2.0 × 10−9 M; the limits of detection, with accumulation times of 4 min for I and III, and of 6 min for II, were calculated to be 5.0 × l0−10 1.0 × 10−9 and 5 × 10−10 M, respectively. Possible interferences by other purine derivatives were examined. The simultaneous determination of 1.7‐dimethylxanthine (paraxanthine) and theophylline is possible by the proposed method.
The derivatization of molecular iodine to iodoform and its determination by adsorptive stripping voltammetry
Authors: Möller Ada , Scholz Fritz , Lovrić Milivoj 
Published: May 2005

AbstractThe determination of elementary iodine in aqueous solutions is possible by a preliminary liquid–liquid extraction into benzene, followed by a derivatization to iodoform with alcoholic KOH solution. The iodoform is measured by adsorptive stripping voltammetry at a signal which corresponds to the reaction

The calibration plot is linear up to 1 × 10−5 mol/L. The detection limit is at least 2 × 10−8 mol/L and the standard deviation of the entire analytical procedure is 10%. The procedure is applicable to seawater.
A new simple long‐path‐length thin‐layer spectroelectrochemical cell in various uses
Authors: Niu Jianjun , Dong Shaojun 
Published: May 2005

AbstractThis article describes the design of a new type of long‐path‐length thin‐layer cell (LPTLC), which is constructed by inserting two Teflon cell bodies into a standard cuvette. This cuvette holder enables the LPTLC to combine with photometric instrumentation conveniently. Gold, platinum, glassy carbon, and other materials can be used for the working electrode. Since no soluble adhesive material is used, the cell can meet various needs (in situ conventional and derivative UV‐vis, in situ circular dichroism, etc.) in both aqueous and nonaqueous systems.
Determination of hesperidin by catholic stripping voltammetry in orange juice and helopyrin, a phytopharmaceutical preparation
Authors: Obendorf Dagmar , Reichart Edgar 
Published: May 2005

AbstractThe electrochemical behavior of hesperidin at the mercury electrode (HMDE, DME) has been studied by differential pulse polarography. Determination of hesperidin can be achieved either by direct reduction of the carbonyl group in the γ‐pyrone ring at −1.1 V (versus Ag/AgC1) or indirectly by cathodic stripping voltammetry via the formation of two different hesperidin‐mercury complexes at the electrode surface that can be reduced at −0.20 V and −0.40 V, respectively. The advantage of cathodic stripping voltammetry is higher sensitivity and due to the possibility of higher sample dilution less influence of matrix effects. The new method is suitable for the determination of lower hesperidin concentrations between 0.1 ppm (1.64 × 10−7 M) and 25 ppm (4.1 × 10−5 M). The application to the determination of hesperidin in orange juice and in Helopyrin tablets, a phytopharmaceutical preparation, is demonstrated.
Bilayer lipid membranes as electrochemical detectors for flow injection immunoanalysis
Authors: Nikolelis Dimitrios P. , Siontorou Christina G. , Andreou Vangelis G. , Viras Kyriakos G. , Krull Ulrich J. 
Published: May 2005

AbstractThis work describes the use of filter‐supported stabilized bilayer lipid membranes (BLMs) for the rapid electrochemical monitoring of an immunological reaction in flowing solution streams. BLMs were prepared from egg phosphatidylcholine (egg PC) and dipalmitoyl phosphatidic acid (DPPA) and the ultrafiltration membranes used were composed of glass microfibers. Thyroxin (T4)/anti‐rabbit T4 was used as a representative immunological reaction for these studies. Antibody was incorporated into a floating lipid matrix at an air–electrolyte interface, and then a casting procedure was used to deliver the lipid onto the filter supports for BLM formation. Injections of antigen were made into flowing streams of a carrier electrolyte solution. Experiments were done in a stopped‐flow mode using lipid mixtures containing 15% (w/w) DPPA to provide only a single transient current signal with a magnitude related to the antigen concentration. Differential scanning calorimetric experiments provided evidence that the antibody‐lipid interactions at the BLMs occurred through electrostatic interactions. BLMs containing 35% DPPA were used to examine regeneration of the active sites of antibody after complex formation by washing with the carrier electrolyte solution. Repetitive cycles of injection of antigen followed by regeneration of antibody binding activity have shown that the maximum number of cycles is about 5, followed by a degradation of signal for a larger number of injections. However, the sensor can also be easily regenerated by recasting of the existing lipid/antibody film at the air–electrolyte interface to form fresh BLMs.