bluuebunny/crossref_metadata_2025_split huggingface dataset:
Theory of derivative and differential potentiometric stripping analysis and stripping chronopotentiometry
Authors: Garai Tibor , Nagy Zoltán , Mészáros Lajos , Bartalits Liliana , Locatelli Clinio , Fagioli Francesco 
Published: May 2005

AbstractThe theoretical treatment of derivative potentiometric stripping analysis and differential potentiometric stripping analysis is presented. The latter term refers to the technique employing the derivative of time with respect to potential vs. the potential function as the measured signal. The mathematical expressions obtained were also verified experimentally.
Design and electrochemical evaluation of an optically transparent thin‐layer electrode flow cell
Authors: Brett Ana Maria C. F. Oliveira 
Published: May 2005

AbstractA new thin‐layer spectroelectrochemical cell with an optically transparent thin‐layer electrode (OTTLE) has been designed and characterized using ferro/ferricyanide in aqueous solution with potassium chloride supporting electrolyte as a model system. The optical configuration is directed perpendicularly through the OTTLE and solution. The cell is equipped with two semi‐transparent tin dioxide coated glass windows at a distance of 50–150 μm; that is, smaller than the semi‐infinite electrochemical diffusion layer thickness, and can be used either in a stationary mode or in a continuous‐flow system. Design is such that platinum wire or tin dioxide can be used as working electrode, the reference being Ag/AgCl. The formal potential obtained for the ferro/ferricyanide system is in good agreement with that expected; the difference between the anodic and cathodic peak potentials in cyclic voltammograms is less than 10 mV which suggests a good cell design. It is intended to apply the cell to in situ spectrophotometric monitoring of UV/vis/near‐IR absorbance changes due to electrode reactions of biologically electroactive compounds. The complementary information from the two techniques should be valuable in elucidation of reaction rates and mechanism.
Rotating ring‐disk electrode studies of polypyrrole‐glucose oxidase biosensors
Authors: Bélanger Daniel , Nadreau Jocelyn , Fortier Guy 
Published: May 2005

AbstractA rotating ring‐disk electrode, (RRDE) of which the platinum disk was coated with a polypyrrole‐glucose oxidase (PPy‐GOD) film by electrochemical polymerization and the ring was left bare, has been used to characterize the PPy‐GOD electrode. Polypyrrole‐GOD films of various thicknesses grown in the presence of 100 and 500 U/ml of GOD in the deposition solution were used. The amperometric current generated at 0.7 V versus saturated calomel electrode (SCE) by the electrochemical oxidation of hydrogen peroxide, generated by the enzymatic reaction, has been evaluated at both the coated disk and uncoated ring at various rotation speeds. The collection efficiency of the RRDE was 22% and was used to evaluate the total current of the PPy‐GOD electrode. The total current of a polypyrrole electrode was defined as the sum of the disk current and the total ring current taken as the observed ring current divided by the collection efficiency of the RRDE. From this study, it clearly appears that the biotransformation of glucose takes place mainly at the polypyrrole film/solution interface independently of the rotation speed and that the catalysis is not limited by oxygen. The Eadie‐Hofstee type plots obtained for disk current with 10–225 mM of glucose show a strong positive deviation for glucose concentrations higher than 100 mM. On the other hand, linear plots are obtained when the total current of the enzyme electrode is considered. No definitive explanation can be given for these behaviors, except that at a higher glucose concentration, the flux of glucose is high enough to permit the diffusion of glucose deeper in the film, where it can be oxidized by the enzyme. Thus, the catalytic reaction is taking place in a thicker layer of the film.
Exploitation of the nitrite catalytic effect to enhance the sensitivity and selectivity of the adsorptive stripping voltammetric method for the determination of cobalt with dimethylglyoxime
Authors: Bobrowski Andrzej , Bond Alan M. 
Published: May 2005

AbstractA highly sensitive, catalytic adsorptive stripping voltammetric (AV) method for the determination of ultratrace cobalt concentrations in the supporting electrolyte consisting of ammonia buffer, dimethylglyoxime (DMG), and NaNO2 has been evaluated and compared with the well‐known AV method with DMG and other dioximes. Conditions for maximal sensitivity and the simultaneous determination of Co and Ni are described. The sensitivity of the cobalt‐DMG complex method is improved about 20‐fold by exploitation of the catalytic effect observed in the presence of nitrite. The detection limit of the method is 4 × 10−11 M. As a result of the selective nature of the catalytic response for cobalt, the method is more sensitive and selective against Ni and Zn than the commonly used classical DMG method (without nitrite). The method, which uses inexpensive and widely available reagents (DMG, NaNO2), is suitable for the determination of Co in the 10−10 M–10−9 M concentration range even when the Ni concentration is 10 to 50 times higher, as is the case in many practical situations. The method is also advantageous when the background current from sources other than Ni makes the use of the less sensitive method with DMG impossible. However, the selectivity of the method over the Ni and Zn responses is inferior than obtained with previously published but more expensive catalytic methods based on nioxime‐NaNO2 or α‐benzil dioxime‐NaNO2 systems.
Adsorptive stripping voltammetric measurements of trace niobium levels following chelation with cupferron
Authors: Wang Joseph , Lu Jianmin , Taha Ziad 
Published: May 2005

AbstractTrace levels of niobium can be determined by adsorptive stripping voltammetry, with controlled interfacial accumulation of the niobium/cupferron complex onto the hanging mercury drop electrode. Optimal conditions (5 times; 10−6 M cupferron in acetate buffer (pH 4.0), a preconcentration potential of −0.2 V, and differential pulse stripping) allow convenient quantitation of μg/L (ppb) concentrations. The detection limit is 83 ppt (10 minute preconcentration); the response is linear over the 0–20 ppb range: and the relative standard deviation (at the 5 ppb level) is 2.0%. Most cations do not interfere in the determination of niobium. Complexation with cupferron also allows analogous trace measurements of vanadium.
Electrochemical detection of carbohydrates at nickel‐copper and nickel‐chromium‐iron alloy electrodes
Authors: Marioli Juan M. , Kuwana Theodore 
Published: May 2005

AbstractNickel‐copper and nickel‐chromium‐iron alloy electrodes are employed in the amperometric detection of carbohydrates after anion‐exchange liquid chromatographic separation. The sugars are oxidized at the Ni(III) oxyhydroxide sites formed on the electrode surface at potentials of approximately 0.45 V (versus Ag/AgCl reference electrode). The set potential for the electrochemical detection of carbohydrates is optimized on a signal‐to‐noise (S/N) ratio analysis at different potential values. The detection limits for glucose, based on an S/N ratio of 3, are 15 and 1 picomoles at the nickel‐copper and the nickel‐chromium‐iron alloy electrodes, respectively. The electrodes' response was also assessed with respect to the detection of sugar alcohols, mono‐, and disaccharides.
Square‐wave voltammetry at spherical and disk microelectrodes as a function of electrode radius and frequency
Authors: Komorsky‐Lovrić Š. , Lovrić M. , Bond A. M. 
Published: May 2005

AbstractSquare‐wave voltammograms obtained with small spherical electrodes and influenced by electrode kinetics have been analyzed theoretically as a function of electrode radius and frequency for a reduction reaction involving a soluble reactant and product. If the redox reaction is reversible, or totally irreversible, dimensionless peak currents depend linearly on the parameter y = (D0/ƒ)1/2/r, where r is the electrode radius, D0 the diffusion coefficient of the oxidized species, and ƒ the square‐wave frequency. The variation of electrode size or frequency enables the determination of the charge transfer coefficient α or the kinetic parameter ks/D1/2 of an irreversible reaction (ks = standard heterogeneous charge transfer rate constant) if its reversible peak potential is known. Differences between square‐wave voltammograms at spherical and inlaid disk microelectrodes are considered theoretically and shown to be small under most conditions. As expected, in the limiting case where steady‐state mass transfer conditions prevail at microelectrodes, both the square‐wave current and peak potential become independent of the frequency. Steady‐state voltammetry, which is readily achieved at a slow d.c. scan rate of potential, may be more suitable than square‐wave voltammetry for kinetic measurements at microelectrodes, although the latter is likely to be the more sensitive technique in the analytical sense. This is in contrast to conventionally sized electrodes where the square‐wave method is likely to be superior in all contexts. Criteria of reversibility are proposed and confirmed by square‐wave voltammetric measurements on the reversible oxidation of ferrocene and quasi‐reversible reduction of ferricyanide at an inlaid gold microdisk electrode.
Polarographic and electrochemical studies of some aromatic and heterocyclic nitro compounds: Part VI. Polarographic, voltammetric, and controlled potential reduction of ortho‐nitrobenzaldehyde anthranil
Authors: Fijalek Zbigniew , Zuman P. 
Published: May 2005

AbstractIn acidic media, at pH < 7, the nitro group, in ortho‐nitrobenzaldehyde (I) is reduced in a four‐electron step to ortho‐formylphenylhydroxylamine (II). The protonated form of II is reduced by two electrons to ortho‐aminobenzaldehyde (IV), which is further reduced in a two‐electron process to ortho‐aminobenzylalcohol. At pH > 7, the arylhydroxylamine (II) condenses to form a nitrone, which is further reduced in two two‐electron waves, corresponding to the cleavage of the N‐O bond and reduction of the azomethine bond. At pH 7, formation of anthranil (III) from II is a relatively slow process: in cyclic voltammetry (CV) and d.c. polarography, II is further reduced to IV; in controlled potential electrolysis at a mercury pool electrode, the same products are obtained at 0° C, but at 25° C, III is the predominant product.
Determination of paraquat by cathodic stripping voltammetry after accumulation through the formation of an ion pair on a hanging mercury drop electrode
Authors: Macias J. M. Pinilla , Hernández L. Hernández , Sobrino J. M. Moreno , Escribano M. T. Sevilla 
Published: May 2005

AbstractThe formation of ion pairs is used to greatly enhance the sensitivity of cathodic stripping measurements at the hanging mercury drop electrode (HMDE). Such a scheme is illustrated for the trace determination of paraquat. Factors affecting the response are explored.
Determination of cefobid using adsorptive stripping voltammetric technique in different media
Authors: Ali Azza M. M. , El‐Maali Nagwa Abo , Ghandour Mahmoud A. 
Published: May 2005

AbstractA sensitive voltammetric method has been developed for the cephalosporin antibiotic, cefoperazone monosodium salt (cefobid). The method is based on controlled adsorptive preconcentration of cefobid on the hanging mercury drop electrode (HMDE), followed by voltammetric determination of the surface species by cathodic stripping voltammetry. Cyclic voltammetry was used to examine the interfacial behavior of the drug. The electroanalytical techniques used were direct current stripping voltammetry (DCSV) and differential pulse stripping voltammetry (DPSV). The adsorptive stripping response was evaluated with respect to preconcentration dependence, possible interferences, and other variables. The drug is strongly adsorbed in acidic media, with maximum adsorption at pH2. The detection limit found by DPSV was 2 × 10−9 M (1.33 ppb), with 240 second preconcentration. The relative standard deviation at the 1 × 10−7 M level was 3.2%. The interference of uric and ascorbic acids and copper and calcium ions has been studied. The method was applied to the determination of cefobid in urine.
Nickelocene‐mediated glucose oxidase electrode
Authors: Atanasov P. , Kaisheva A. , Gamburzev S. , Iliev I. , Bobrin S. 
Published: May 2005

AbstractNickelocene is investigated as an electrochemical mediator in glucose oxidase (GOD) amperometric electrodes. It is found that the adsorbed nickelocene mediates the charge transfer between the electrode and glucose oxidase adsorbed on the electrode surface. The quasi redox potential of a nickelocene/nickelocenium couple adsorbed on an electrochemically activated pyrolytic graphite electrode is experimentally estimated (−0.105 V vs. Ag/AgCl). The steady‐state amperometric response of nickelocene‐mediated glucose electrode is investigated as a function of the glucose concentration, applied potential, and solution pH of the electrolyte. The working potential of a nickelocene‐mediated glucose electrode is 0.00 V (vs. Ag/AgCl).
Flow‐injection potentiometric determination of creatinine in urine using sub‐Nernstian linear response range
Authors: Matuszewski Wojciech , Trojanowicz Marek , Meyerhoff Mark E. , Moszczyńska Anna , Lange‐Moroz Elzbieta 
Published: May 2005

AbstractA novel split‐stream flow‐injection system is described for the determination of creatinine in urine samples. The system is based on the use of a microreactor with immobilized creatinine iminohydrolase and downstream potentiometric detection of ammonium ions using a nonactin‐based membrane electrode. Splitting of the sample into two branches of the flow system, with the concomitant addition of alkali metal ions to the carrier solution, allows for simple correction of endogeneous ammonia and alkali metal ion levels via operation of the electrode in the sub‐Nernstian linear response range. The analytical utility of the system developed is illustrated by accurate creatinine determinations in urine samples.
Study of the electrode process of hemoglobin at a polymerized azure A film electrode
Authors: Dong Shaojun , Chu Qinghui 
Published: May 2005

AbstractThe electrochemically polymerized azure A film electrode is reported. The resulting film on a platinum electrode surface was analyzed with electron spectroscopy for chemical analysis (ESCA). The heterogeneous electron transfer processes of hemoglobin at the polymerized azure A film electrode have been investigated using in situ UV‐visible spectroelectrochemistry. The formal potential (E°′) and electron transfer number (n) of hemoglobin were calculated as E = 0.088 V versus NHE (standard deviation ±0.5, N = 4) and n = 1.8 (standard deviation ±0.5, N = 4). Exhaustive reduction and oxidation electrolysis are achieved in 80 and 380 seconds, respectively, during a potential step between −0.3 and +0.3 V. A formal heterogeneous electron‐transfer rate constant (ksh) of 3.54(±0.12) × 10−6 cm/s and a transfer coefficient (α) of 0.28(±0.01) were obtained by cyclic voltabsorptometry, which indicated that the poly‐azure A film electrode is able to catalyze the direct reduction and oxidation of hemoglobin.
Determination of chromium(VI) and chromium(III) by using a diphenylcarbazide‐modified carbon paste electrode
Authors: Paniagua A. R. , Vazquez M. D. , Tascon M. L. , Batanero P. Sanchez 
Published: May 2005

AbstractA carbon paste electrode modified with diphenylcarbazide has been prepared in order to improve the analytical determination of chromium(VI) and chromium(III) using voltammetric techniques. Several parameters, such as carbon/diphenylcarbazide ratio, carbon/Nujol ratio, scan rate, accumulation time, etc., have been explored. A voltammetric study of both chemical species and an explanation of the chemical and electrochemical mechanism are presented. When applied to assays of soil samples, the results compared favorably to those of a polarographic method.
Adsorptive stripping tensammetry of motor oils in aqueous solutions
Authors: Kovac Martin , Kalvoda Robert , Novotny Ladislav , Berka Antonin 
Published: May 2005

AbstractAdsorptive stripping tensammetry at a hanging mercury drop electrode is described for aqueous solutions of various motor oils. The method can be used for the determination of oils in polluted waters in the concentration range from 0.4–0.8 to 3.5–7 ppm, dependent on the type of oil. Distinction between “pure” and “used” motor oil is made.
A voltammetric phosphate sensor based on heteropolyanion formation at the nitrobenzene/water interface
Authors: Osakai Toshiyuki , Himeno Sadayuki , Saito Atsuyoshi , Katano Hajime 
Published: May 2005

AbstractA novel voltammetric sensor for phosphate ion has been developed. This sensor relies on electrochemical formation of a heteropolyanion at the interface between an aqueous sample solution and a nitrobenzene solution containing hexamolybdate anion (Mo6) and on the subsequent detection of the voltammetric current due to the interfacial transfer of the heteropolyanion formed. Under optimal conditions, the voltammetric current is proportional to the phosphate concentration in the range from 0.02 to 0.5 mM. Though silicate ion interferes with the determination of phosphate ion, arsenate and germanate ions cause no significant interference.
Study of polypyrrole film as redox electrode
Authors: Michalska Agata , Lewenstam Andrzej , Ivaska Ari , Hulanicki Adam 
Published: May 2005

AbstractThe potentiometric redox sensitivity of different polypyrrole membranes is studied. Good Nernstian responses are observed for polypyrrole membranes polymerized on platinum substrate. The analytical use of such films as redox sensors is demonstrated.
Platinized carbon ultramicroelectrodes as glucose biosensors
Authors: Reynolds Eugene R. , Yacynych Alexander M. 
Published: May 2005

AbstractMiniaturized glucose biosensors were constructed by all‐chemical means from disk‐shaped carbon ultramicroelectrodes (UMEs) (diameter = 8 μm). These ultramicrobiosensors (UMBs) are capable of direct measurement of glucose in the presence of interfering species. Carbon UMEs were partially platinized by the electrochemical reduction of a platinum (IV) complex. Platinization of the carbon UMEs gave an increased current response to hydrogen peroxide and allowed the modified electrode to be operated at a lower oxidative potential. Glucose oxidase (E.C. 1.1.3.4.) was immobilized either by glutaraldehyde cross‐linking or by direct covalent attachment to the electrode surface using carbodiimide. Response time (100% response) was 15–45 seconds. Response was linear over the range of 3–7 mM glucose. An electropolymerized film of poly(1,3‐diaminobenzene) was used to prevent interfering species.
Cupric hexacyanoferrate colloid doped polypyrrole film modified electrode
Authors: Li Yijun , Zhang Wenbin , Dong Shaojun 
Published: May 2005

AbstractAnionic colloid cupric hexacyanoferrate (CuHCF) was incorporated into polypyrrole (PPy) films in the course of electrochemical polymerization of pyrrole from aqueous solution containing pyrrole and CuHCF colloid. The films obtained were dark brown in color. Three redox peaks appeared in the cyclic voltammogram (CV). The peaks around 0.7 V (vs, SCE) showed cation‐selective properties. X‐ray photoelectron spectroscopic analysis and ultraviolet‐visible (UV‐vis) spectroscopic properties of the film were investigated.
The electrochemical oxidation of penicillins on gold electrodes
Authors: Koprowski Lisa , Kirchmann Eric , Welch Lawrence E. 
Published: May 2005

AbstractPenicillins can be electrochemically oxidized on gold electrodes in the presence of a catalytic surface oxide. Although oxidation can occur throughout a wide range of pH values, an acetate buffer solvent was selected to maximize the sensitivity and stability. Several amperometric waveforms were tested for penicillin detection using flow injection analysis. The use of pulsed amperometric detection (PAD) allowed the penicillins to be monitored either directly or indirectly depending on the specified waveform. Direct detection using standard PAD proved to be the optimal detection method, featuring excellent reproducibility and detectability to 4 × 10 −7 M for penicillin G.
Direct ion‐selective determination of boron in gallium arsenide
Authors: Lanza Pietro 
Published: May 2005

AbstractThe behavior of the Orion fluoroborate‐selective electrode (Model 93‐05) has been investigated under several working conditions. Long response time and slow shift of the potential can cause serious difficulties in practical applications. In spite of these facts, after a suitable conditioning of the electrode in solutions whose composition is similar to that of the solutions of the samples, sufficiently reproducible results are possible. Samples of GaAs, containing at least 1 μg/g of boron, can be analyzed with a precision (relative standard deviation) of about 5% (n = 5).
In situ fourier transform infrared reflection spectroscopic studies of ferricyanide/ferrocyanide on graphite electrode
Authors: Zhang Jiujun , Yin Qiguang , Cai Shengmin , Fujishima Akira 
Published: May 2005

AbstractThe electrochemical reactions of Fe(CN) and Fe(CN) on basal plane graphite electrode were studied using cyclic voltammetry and in situ Fourier transform infrared (FTIR) reflection spectroelectrochemistry. The IR band near 2080 to 2067 cm−1 was found to be an intermediate for Fe(CN) reduction and the band near 2058 to 2067 cm−1 for Fe(CN) oxidation. The possible mechanisms of reduction and oxidation and structure of intermediate are discussed.
Liquid chromatography and electrochemical detection of organic peroxides by reduction at an iron phthalocyanine chemically modified electrode
Authors: Qi Xiaohe , Baldwin Richard P. 
Published: May 2005

AbstractChemically modified carbon paste electrodes containing incorporated iron phthalocyanine (FePC) exhibited an electrocatalytic response for the reduction of organic peroxides. In pH 2 phosphate buffer, reduction at the FePC chemically modified electrode (CME) occurred at +0.1 to +0.2 V (vs. Ag/AgCl) for all peroxides examined except for dialkyl compounds. Because this potential was 100 mV more positive than that required for oxygen reduction at this electrode, amperometric detection of peroxides by this approach was possible in flow injection and high‐performance liquid chromatography without deoxygenating the sample or mobile phase solutions. In flow injection, the detection limit using this approach was 5 picomole (pmol) for hydrogen peroxide and varied from less than 1 pmol to as high as several hundred pmol for other peroxides. Cyclic voltammetry (CV) and visible spectroscopy experiments were consistent with a two‐step electrocatalytic mechanism involving the Fe(III)PC/Fe(II)PC couple.
Effect of polymer composition on the detection of electroinactive species using conductive polymers
Authors: Sadik Omowunmi A. , Wallace Gordon G. 
Published: May 2005

AbstractPrevious workers have demonstrated that conducting electroactive polymers can be used to detect electroinactive species. In this work, the effect of polymer composition, the nature of the eluent, and the electrochemical waveform on the selectivity of this detection process have been investigated.
A polytryptophan‐modified electrode
Authors: Narasaiah D. , Mitra Chanchal K. 
Published: May 2005

AbstractA conducting polymer film has been formed on a Pt‐wire mesh by electrochemical oxidation of tryptophan from acidic and alkaline solutions. The electrochemical characteristics of the film have been studied both by cyclic voltammetry and impedance studies. For both p‐benzoquinone and potassium ferrocyanide, the peak currents are only slightly lower compared to bare electrode, but the background currents are considerably reduced. The polymer film is not acting as a mediator and is chemically stable, but it is electrochemically unstable outside the potential range of −700 to 800 mV (vs. SCE). Possible uses of this modified electrode in biosensors are discussed.