bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hexacyanoferrate‐anion exchanger‐modified carbon paste electrodes
Authors: Labuda Ján , Hudáková Monika 
Published: May 2005

AbstractThe preparation of carbon paste electrodes (CPEs) modified with the hexacyanoferrate ion attached to synthetic hydrotalcite, a solid anion exchange resin Wofatit SBW and a liquid anion exchanger tris‐octylamine (TOA) used as pasting liquid, is described. Stability of the electrodes and their electrocatalytic properties were investigated. The surface‐modified hexacyanoferrate‐TOA‐CPE can be prepared and renewed in a simple and reproducible manner. The sensor was applied to the determination of ascorbic acid in real samples using a mediator accumulation/chronoamperometric detection scheme.
Simultaneous FIA determination of two components with differential normal pulse voltammetric multidetection
Authors: Alpízar Jesús , Crespí Antonio , Cladera Andreu , Forteza Rafael , Cerdà Víctor 
Published: May 2005

AbstractA flow injection method for the simultaneous determination of two components based on differential normal pulse voltammetric multidetection was developed. The method entails applying two sequential potential pulses to a 3‐electrode voltammetric system (with a carbon paste working electrode) connected to a flow‐through cell. The proposed method can be applied to other complex systems comprising more than two substances provided large differences in their peak potentials.
Analysis of the derivative chronopotentiometric peak shape for the reduction of adsorbed bovine serum albumin
Authors: Honeychurch Michael J. , Ridd Michael J. 
Published: May 2005

AbstractThe broad shape of the reduction peak of adsorbed proteins containing multiple electroactive disulfide bonds can be modeled by developing the existing theory used to describe the reduction peaks of proteins with multiple heme groups. This theory is developed and applied to the study of the derivative chronopotentiometric (DCP) reduction peak of adsorbed bovine serum albumin (BSA). For BSA adsorbed on mercury, six disulfide groups were found to be electroactive. It was found that the DCP peak shape could be deconvoluted into five electrochemically equivalent, non‐interacting disulfide groups with formal potentials (vs SCE) of −598 mV, −598 ± 17.8 mV and −598 ± 41.3 mV, and one electrochemically distinct group with a formal potential of −706 mV.
Activation of titanium electrodes for voltammetric detection of oxygen and hydrogen peroxide in alkaline media
Authors: Clark Theotis , Johnson Dennis C. 
Published: May 2005

AbstractBright, freshly‐polished Ti electrodes give minimal cathodic response for O2 and H2O2 in 1.0 M NaOH. However, the response is increased gradually by repeated application of a triangular waveform within the approximate potential limits of O2 response (ca. −1.5 to −0.7 V vs. SCE). This same voltammetric pretreatment applied for excessive periods results in formation of golden films on the Ti surfaces that are active for reduction of O2 and H2O2. Levich plots of cathodic current for O2 and H2O2 at rotated golden‐Ti disk electrodes in 1.0 M NaOH (−1.35 V) are linear over a large range of rotational velocity (42 to 513 rad s−1), a behavior considered to be indicative of fast heterogeneous kinetics. Ring‐disk data demonstrate that a small amount of H2O2 is produced throughout the potential region for O2 reduction and H2O2 is concluded to be an intermediate product in the O2‐reduction mechanism. These observations are consistent with those reported previously for single‐crystal TiO2 electrodes.
Critical comparison of metallized and mediator‐based carbon paste glucose biosensors
Authors: Wang Joseph , Chen Liang , Liu Jie 
Published: May 2005

AbstractThe performance of metallized carbon oxidase‐based biosensors is critically compared with that of mediator‐based enzyme electrodes. Dimethyl ferrocene and rhodium metal centers are used as model mediator and catalyst, respectively, in connection to carbon‐paste electrode transducers and assays of glucose. The rhodium‐containing bioelectrode displays enhanced selectivity (particularly improved discrimination against ascorbic acid), lower sensitivity, faster response time, greater oxygen dependence, and similar detection limit in comparison to the mediated electrode. In addition to assessing the relative merits of both strategies, the data offer useful insights into the behavior of these ‘first’‐ and ‘second‐generation’ oxidase amperometric electrodes.
Development of an ion‐sensitive field effect transistor based on PVC membrane technology with improved long‐term stability
Authors: Jiménez Cecilia , Bartroli Jordi 
Published: May 2005

AbstractAn NH ‐ISFET sensor based on PVC membrane technology with improved long‐term stability has been developed. As a new approach, the plasticizer (tetra‐n‐undecyl) 3,3′,4,4′ ‐benzhydroltetracarboxylate (ETH2112) was used in membrane preparation. Its lipophilic nature provides a restricted diffusion of the membrane components to the external solution and improves membrane adhesion to the gate area of the ISFET. The good performance of this plasticizer was confirmed by comparison with usual plasticizers applied in standard ISE technology. Moreover, the durability and stability of the sensor were enhanced by the application of a graphite‐epoxy layer as an internal reference between the gate area and the PVC membrane. This composite layer permits the reduction of the optical sensitivity and improves the adherence of the PVC membrane to the ISFET surface. Furthermore, this composite layer acts as a plug, preventing the entrance of water upon the encapsulant‐chip interface, thus protecting electrical connections from moisture. As a result, an NH ‐ISFET with a long‐term stability of three months and a sensitivity of −58.7 ± 2.3 mV decade−1 in a linear range of 10−5 −0.1 mol dm−3 has been developed. The application of this sensor to a continuous‐flow system has confirmed the feasibility of the technological approach proposed.
TTF‐TCNQ complex based printed biosensor for long‐term operation
Authors: Khan Golam Faruque 
Published: May 2005

AbstractA printed amperometric glucose sensor based on glucose oxidase adsorbed on crystals of tetrathiafulvalene‐tetracyanoquinodimethane (TTF‐TCNQ) is described. The sensitivity and the stability of the sensor are affected by the binder and solvent used for the preparation of the GOD.TTF‐TCNQ paste. The sensors are continuously used in a flow injection analysis (FIA) system under continuous polarization at 0.15 V (vs Ag/AgCl) at 37°C. The developed sensors exhibit a large response current, an extended linear range and oxygen independence. The sensors can be used for more than 3 months. The GOD.TTF‐TCNQ paste is suitable for the preparation of planar sensor by screen printing method.
Development of a hypoxanthine biosensor based on immobilized xanthine oxidase chemically modified electrode
Authors: Hu Shengshui , Liu Chung‐Chiun 
Published: May 2005

AbstractAn amperometric biosensor for hypoxanthine determination has been developed. The sensor uses a Nafion‐paraquat chemically modified glassy‐carbon electrode. It detects the oxygen consumed by the enzymatic reaction catalyzed by xanthine oxidase which is immobilized on the electrode surface. The sensor responds linearly to hypoxanthine over the concentration range of 1 × 10−6 M −2 × 10−4 M. The biosensor can be reused for more than 100 times without significant deterioration in performance. After 32 days storage at 3–5°C, the sensor response remains at 68% of the initial level. The high sensitivity, selectivity and stability of this biosensor demonstrates its practical applicability for a simple, rapid and economical determination of hypoxanthine in fish samples.
pHh‐dependent permselectivity of the fibrinogen‐modified carbon paste electrode
Authors: El Rhazi Mama , Randriamahazaka Hyacinthe N. , Nigretto Jean‐Maxime 
Published: May 2005

AbstractThe modification of carbon paste matrices with fibrinogen is reported. The effect of the pH of the solution on the CV peak currents of positively or negatively charged redox analytes was examined at the fibrinogen‐modified carbon paste electrode. In the presence of the coating, pH‐dependent selectivity in electrochemical detection of charged species was demonstrated depending on the sign of the supported charge. Above the isoelectric pH attributed to the immobilized protein (5.5), the current response of anionic redox probes [Fe(CN)/Fe(CN)] was impeded while the response was almost totally restored below this pH. Opposite trends were observed with the Ru(NH3)/Ru(NH3) cationic redox analytes.
Electrochemil investigation of the photodecomposition of selected ferrocene derivatives
Authors: Davis James , Vaughan D. Huw , Cardosi Marco F. 
Published: May 2005

AbstractThe photostability of nine ferrocene derivatives of varying functionality was investigated using cyclic voltammetry. Derivatives with carbonyl groups (aldehyde or ketone) directly attached to the cyclopentadiene ring system were found to decompose in aqueous (pH 7.4) solution over a period of 10 min when exposed to light. The kinetics of the photodecomposition process were investigated and the relative values of the rate constants for the photodecomposition tabulated. The implications for biosensor applications are assessed.
Electrochemical oxidation and determination of heparin at electrodes modified with ruthenium oxide or copper oxide
Authors: Lewinski Krzysztof , Hu Yun , Griffin Charles C. , Cox James A. 
Published: May 2005

AbstractThe electrochemical oxidation of full‐size heparin (13–15 kDa) is demonstrated in 1 M H3PO4 at a glassy carbon electrode coated with a ruthenium oxide film. The pathway apparently is analogous to chemical oxidation by periodate. By comparison to currents from inorganic species, it is apparent that only about 2 electrons per mole are involved. Flow injection analysis (FIA) allowed determinations down to 2 μM heparin, but the calibration plot was nonlinear. Low molecular weight heparin (5–6 kDa) was not electroactive with this system. In basic solution at a glassy carbon electrode that is modified with a film of Cu2O, both full‐size and low molecular weight heparin are oxidized. The pathways involved oxidative desulfation and attack on saccharide units with evolution of CO2. Linear calibration plots which extended into the sub‐μM level were obtained by FIA. The detection limits, which were based on a value of 3 for the ratio of the signal to the standard deviation of replicates, were 9 nM for full‐size and 20–30 nM for various low molecular weight heparin samples.
An original electroenzymatic system: Flavin reductase‐riboflavin for the improvement of dehydrogenase‐based biosensors. Application to the amperometric detection of lactate
Authors: Cosnier Serge , Fontecave Marc , Innocent Christophe , Niviere Vincent 
Published: May 2005

AbstractThe electropolymerization of a flavin reductase (Fre) – amphiphilic pyrrole ammonium mixture previously adsorbed on the electrode surface provides an efficient bioelectrode for the amperometric detection of NADH and NADPH. The bioelectrode response was based on the oxidation at −;0.1 V vs. SCE of the enzymically generated dihydroriboflavin. The sensitivity and detection limit of the bioelectrode were 29 mAM−1 cm−2 and 0.2 μM for NADH and 15.8 mAM−1 cm−2 and 0.4 μM for NADPH. The coimmobilization of Fre and a lactate dehydrogenase leads to a dehydrogenase‐based bioelectrode for the determination of lactate in the presence of riboflavin and NAD+. With laponite additives into the polypyrrole host matrix, the sensitivity and the detection limit of the bioelectrode for lactate are 11.7 mAM−1 cm−2 and 1 μM respectively. Owing to the negative value of the applied potential for the oxidation of riboflavin, the response of the bienzyme electrode remains insensitive to interferents like ascorbate, urate and acetaminophen.
Silica‐modified carbon paste electrode for copper determination in ammoniacal medium
Authors: Walcarius A. , Bessiere J. 
Published: May 2005

AbstractThe silica modified carbon paste electrode (SMCPE) was applied to the voltammetric detection of copper(II) at trace level after its accumulation under open‐circuit conditions. As demonstrated by cyclic voltammetric experiments, silica particles displayed an attractive ability to efficiently preconcentrate trace copper(II) from ammonia solution, according to a combined acid‐base and complexation reaction: 2 (SiOH) + Cu(NH3) ⇌ (SiO)2Cu(NH3)2 + 2 NH. The analytical procedure involved four successive steps: the preconcentration during a given period of time at open circuit in the ammoniated analyte solution, the medium exchange of the electrode (washed with water) to a pure electrolyte solution (0.1 M HNO3), a 30 s electrolysis for reducing the accumulated CuII species, and the square wave voltammetric determination. Experimental parameters affecting either the uptake of copper(II) or its voltammetric detection at SMCPE were explored, including the solution pH and ionic strength, the ammonia concentration in the preconcentration medium, the preconcentration time, the deposition potential and duration, the anodic stripping scan mode or the silica loading into the paste. A detection limit of 2 × 10−9 M has been achieved after 10 min preconcentration (from a 0.5 M NH3 medium), as determined for a signal‐to‐noise ratio of 3, and a linear calibration plot was obtained in the 5 × 10−9 M to 5 × 10−6 M concentration range. The relative standard deviation (n = 8) for the determination of a 5 × 10−7 M Cu11 sample was 8%.
Formation in situ and electrochemistry of C70‐salt film on a microelectrode
Authors: Cheng Fu‐Xiang , Li Nan‐Qiang , He Wei‐Jun , Gu Zhen‐Nan , Zhou Xi‐Huang , Sun Yi‐Liang , Wu Yong‐Qing 
Published: May 2005

AbstractThe first electrodeposition in situ of C70‐salt films in a mixed solvent on a microdisk electrode is reported. The deposition conditions of these films were optimized and then the electrochemical behaviors of these films were investigated, displaying three one‐electron oxidation peaks with the characteristics of surface reactions. The electron‐transfer coefficients (α) of the three surface reactions were also determined.
Electrooxidation of ammonia and simple amines at titanium electrodes modified with a mixture of ruthenium and titanium dioxides
Authors: Donten Mikołaj , Hyk Wojciech , Ciszkowska Małgorzata , Stojek Zbigniew 
Published: May 2005

AbstractElectrooxidation of ammonia at the Ti/TiO2/RuO2 electrode was investigated using voltammetry, coulometry, 14N NMR, potentiometry with a nitrate ISE, and numerical simulation. The major product of electrooxidation was elementary nitrogen. Nitrate was a minor product. NH4 is not electroactive at the oxide electrode. Since protons are formed in the course of the electrode reaction, incoming ammonia is transformed to NH4, and therefore the flux of ammonia to the electrode surface is strongly depressed in solutions containing no excess of hydroxide ion. Amines were electrooxidized to a variety of compounds. Both ammonia and amines strongly adsorb on the electrode surface. Height of the anodic voltammetric peaks of both ammonia and simple amines was found to be linearly dependent on substrate concentration in a wide millimolar range.
Separation of the depolarizer from surface active substances in the tubes of a flow injection system
Authors: Kubiak Wladyslaw W. , Strozik Miroslaw M. 
Published: May 2005

AbstractThe possibility to separate depolarizer and surfactant bands directly in a flow injection system is reported. Transport of a surfactant is according to an adsorptive or a hydrodynamic mechanism. In the former case a surfactant is transported slower than a depolarizer whereas in the latter case it is transported faster than a depolarizer. Theoretical background for both mechanisms is provided. The influence of sample volume, mixing coil parameters (tube length and inner diameter), tube material and flow rate on the separation process is discussed. The separation process dependence on the flow rate may provide the basis of surface active substances characterization. Such characteristics for several surfactants are presented. Under optimized conditions the parameters of the calibration plots for a depolarizer in the absence and presence of surfactant are statisticaly equivalent.
Voltammetry and LCEC of isoflavones
Authors: Wu Langyu , Laughlin James B. , Dewald Howard D. 
Published: May 2005

AbstractThis study provides electrochemical and LCEC determination for three of the most abundant and most important isoflavones, Biochanin A, formononetin, and genistein. Cyclic voltammetry and pH‐potential diagrams show that the isoflavones undergo pH‐dependent irreversible oxidations. The LCEC determination of the isoflavones has been optimized for mobile phase composition and detection potential. Sub‐nanogram detection limits have been achieved.
Polarographic determination of hydrogen peroxide in perborate containing commercial detergents under the bleaching process condition
Authors: Sužnjević Desanka , Blagojević Stevan , Vučelić Dušan , Zuman Petr 
Published: May 2005

AbstractDifferential pulse (DP) and current sampled (TAST) polarography were applied for measuring hydrogen peroxide in actual washing systems. In addition to the possibility of the hydrogen peroxide determination in commercial detergent species containing sodium perborate monohydrate as bleaching substance, the change in peroxide concentration can be followed under the conditions which usually exist in the washing process. The possibility of determining dissolved oxygen in the peroxide decomposition reaction was also demonstrated.
Anion partitioning into highly lipophilic organic phases
Authors: Andredakis George , Tsagatakis John , Chaniotakis Nikolas A. 
Published: May 2005

AbstractThe partitioning of anions into different highly lipophilic media such as plasticizers used in the construction of ISEs was studied. Using both potentiometry and conductometry, precise partitioning values of a series of common potassium salts were obtained. The partitioning of the anions was shown to be significant and was dependent on the organic media used. These results stress the importance of the materials used in the construction of the anion selective electrodes since they gave anion partitioning sequences linked to the plasticizer, which differ from the common Hofmeister selectivity pattern. At the same time the partitioning values obtained can be used for the experimental estimation of the mobilities of anions in organic media.
Sol‐gel‐derived cobalt phthalocyanine‐dispersed carbon composite electrodes for electrocatalysis and amperometric flow detection
Authors: Wang Joseph , Pamidi Prasad V. A. , Parrado Concepcion , Park Deog Su , Pingarron Jose 
Published: May 2005

AbstractA new sol‐gel‐derived electrocatalytic carbon composite electrode was prepared by dispersing cobalt phthalocyanine (CoPC) in a carbon ceramic network. The performance of the CoPC‐modified sol‐gel carbon composite electrode compares favorably with that of common CoPC‐containing carbon pastes in term of electrocatalytic properties and short‐ and long‐term stability. The greatly improved stability and electrocatalytic action are illustrated in cyclic‐voltammetric and flow injection amperometric measurements of hydrogen peroxide, hydrazine, oxalic acid, cysteine and thiourea. Such improvements are coupled with the versatility, mechanical stability and renewability features of sol‐gel carbon composites.
Anodic and cathodic stripping voltammetry in the simultaneous determination of toxic metals in environmental samples
Authors: Locatelli Clinio 
Published: May 2005

AbstractDifferential pulse anodic and cathodic stripping voltammetry have been employed for the simultaneous determination of AsIII, SeIV CuII, PbII and CdII in environmental matrices. The voltammetric measurements were carried out using a conventional three‐electrode cell and the ammonia‐ammonium chloride buffer (pH 9.2) as supporting electrolyte. The analytical procedure was verified by the analysis of the standard reference materials: Mussel Tissue BCR‐CRM 278 and Ulva Lactuca BCR‐CRM 279. The precision and the accuracy, expressed as relative standard deviation (sr) and relative error (e), respectively, were of the order of 3 to 5%, while the detection limit for each element, under the experimental conditions employed, was around 10−9 M.
Study of bimolecular interactions by molecular modeling and surface acoustic wave device
Authors: Thompson Michael , Frank M. Donata , Stone David C. 
Published: May 2005

AbstractA film containing vicinal diol groups has been formed on the quartz surface of a surface acoustic wave sensor through a silanization reaction with 3‐glycidoxypropyltrimethoxysilane. The interactive selectivity of the silane surface for adsorption of several vapor analytes was measured using a gas chromatograph‐acoustic wave device combination. Much larger responses are obtained for compounds containing a nitrofunctional group. Computational chemistry is employed to calculate interaction energies for purported hydrogen‐bond complexes between analyte molecules and ethylene glycol, an analogue of the surface silane species. The results of these calculations are compared to the experimental sensor responses.
Plasticized PVC as a high efficiency selective barrier for the amperometric detection of phenolics
Authors: Christie Ian M. , Treloar Paul , Reddy Subrayal , Hepburn Carlos , Hulme John , Vadgama Pankaj 
Published: May 2005

AbstractIon selective and amperometric electrodes based on PVC membranes were constructed for the measurement of phenolics and assessed for potential use in monitoring coke works effluent treatment. Potentiometric working ranges are restricted to >100 mM, suffering thiocyanate interference, despite response slopes of <160mV/decade. Fabrication of a planar format is described, suitable for mass production. Similar membranes have been characterized in amperometric sensors, achieving greater sensitivity (>0.1 mM), tailored linear ranges and elimination of thiocyanate interference. Enhancement of electrochemical responses by use of high (>13) pH is achieved by stable encapsulation of such an environment beneath ion impermeable PVC within the sensor structure.
Humidity and temperature effects on the response to ethylene of an amperometric sensor utilizing a gold‐nafion electrode
Authors: Jordan Larry R. , Hauser Peter C. , Dawson George A. 
Published: May 2005

AbstractThe response to ethylene of chemically deposited gold‐Nafion electrodes was found to increase as the real surface area of the electrode was increased. However, humidity was found to lower the sensitivity of the electrode to ethylene. For larger electrode surface areas the humidity dependence of the sensor response to ethylene was found to increase. As well as the surface area, the method used to fabricate the gold‐Nafion electrode strongly influenced the humidity dependence. The response to ethylene on a vapor deposited electrode showed only a negligible humidity influence which may make this method more suitable for the fabrication of electrodes. The temperature dependence, for both chemically and vapor deposited electrodes, was found to be a 1% decrease in response to ethylene per °C decrease in temperature.