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  • Polymer and Materials Science  (23)
  • Spectroelectrochemistry  (2)
  • 1
    Digitale Medien
    Digitale Medien
    A finite-element method for determining ohmic distortion of current-voltage curves at hydrodynamic electrodes (1993)
    Weinheim : Wiley-Blackwell
    Electroanalysis 5 (1993), S. 41-46 
    Details
    ISSN: 1040-0397
    Schlagwort(e): Ohmic distortion ; Hydrodynamic electrodes ; Finite-element method ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A finite-element method is described that predicts the effects of ohmic distortion of current-voltage curves for arbitrary cell and hydrodynamic electrode geometries using the widely available circuit analysis program SPICE. Simulated and experimental data are presented for a channel electrode flow cell showing the displacement of the half-wave potential and the potential-dependent error in the Tafel slope for the case of an electrochemically reversible electrode reaction. Error curves are provided that may be scaled for different electrolyte conductivities as a guide to the maximum current levels that may be used in practice. For analytical flow detection work, the displacement of the half-wave potential under certain conditions implies that high detection potentials must be used to obtain the correct concentration-related current intensity. The implications for quantitative measurements using practical electrodes are assessed.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/elan.1140050108
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  • 2
    Digitale Medien
    Digitale Medien
    Sonovoltammetric behavior of ascorbic acid and dehydroascorbic acid at glassy carbon electrodes: Analysis using pulsed sonovoltammetry (1996)
    Weinheim : Wiley-Blackwell
    Electroanalysis 8 (1996), S. 218-222 
    Details
    ISSN: 1040-0397
    Schlagwort(e): Voltammetry ; Ultrasound ; Ascorbic acid ; Dehydroascorbic acid ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The effect of power ultrasound on the voltammetric behavior of ascorbic acid and dehydroascorbic acid at a glassy carbon electrode is described. The voltammetric characteristics of both compounds were found to be modified by ultrasonically formed radicals. In the case of dehydroascorbic acid the single sweep voltammogram shows an anodic signal in the presence of ultrasound which probably results from the formation of an oxidizable radical known to be an intermediate of ascorbic acid oxidation. In the case of ascorbic acid pulsed sonovoltammetry is applied and characterized regarding the time dependence of the current decay and the reliability of its analytical performance. The utility of pulsed sonovoltammetry is demonstrated analyzing a pain killer tablet regarding the ascorbic acid content.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/elan.1140080304
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  • 3
    Digitale Medien
    Digitale Medien
    Photo-electroanalysis: Indirect determination of anthracene using the oxygen reduction in aqueous acetonitrile (1996)
    Weinheim : Wiley-Blackwell
    Electroanalysis 8 (1996), S. 702-705 
    Details
    ISSN: 1040-0397
    Schlagwort(e): Anthracene ; Photoelestroanalysis ; Aromatic reduction ; Oxygen reduction ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A novel method for the photoelectroanalysis of anthracene, as a model compound, is proposed. This technique utilizes a gold electrode in a flowing system of electrolyte, air saturated with oxygen. On irradiation of the electrode with UV-vis light there is a reduction in the level of the oxygen four-electron reductive limiting current due to a reaction of the excited state anthracene and oxygen in acetonitrile/water solution. A linear response over four orders of magnitude (10-2 to 10-1 mol dm-3 was observed between this reduction of current and the concentration of anthracene suggesting the application of this type of technique to the detection of trace levels of aromatic molecules.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/elan.1140080719
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  • 4
    Digitale Medien
    Digitale Medien
    The reduction of m-iodo-nitrobenzene: A comparative study using microdisk and channel electrodes (1996)
    Weinheim : Wiley-Blackwell
    Electroanalysis 8 (1996), S. 214-217 
    Details
    ISSN: 1040-0397
    Schlagwort(e): Iodo-nitrobenzene ; Reduction ; Channel electrode ; Microdisk electrode ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The reduction of m-iodo-nitrobenzene, m-I-φ-NO2, in acetonitrile solution was studied using both microdisk and channel electrodes. A voltammetric wave with a halfwave potential of -1.09 V (vs. saturated calomel reference electrode) was observed and both techniques showed that more than one electron was passed per molecule of the substrate. The rates of mass transport were varied in both electrode systems by changing either the electrode radius in the case of microelectrodes, or the electrolyte flow rate in the case of channel electrodes so as to identify the kinetics and mechanism of the electrode process. Both approaches indicated an ECE mechanism operates: where HS denotes the solvent-supporting electrolyte system. The rate constants for the decomposition of the radical anion, [m-I-φ-NO2]·, as determined by the two methods, were in excellent agreement and equal to 0.30(0.05) s-1. Comparisons between the use of microdisks and channel electrodes for such studies are reported and their relative sensitivity assessed.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/elan.1140080303
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  • 5
    Digitale Medien
    Digitale Medien
    A new electrochemical method for the investigation of the aggregation of dyes in solution (1997)
    Weinheim : Wiley-Blackwell
    Electroanalysis 9 (1997), S. 759-764 
    Details
    ISSN: 1040-0397
    Schlagwort(e): Aggregation ; Dyes ; Microelectrodes ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A new electrochemical technique is presented for the investigation of aggregation phenomena in solution over a wide range of solution conditions. Developed nominally for dyes, the method is, in principle, applicable to any electroactive compound. The method employs microelectrodes to measure the change in the diffusion limited current, with concentration, of the aggregating species of interest. At the onset of aggregation, the relationship between this limiting current and concentration deviates from linearity. This deviation, due to the slower rate of diffusion of aggregates, is related to the degree of association of the molecule, assuming a molecular weight distribution of aggregates and using an established relationship between the effective diffusion coefficient and molecular weight. The technique is contrasted with an existing spectroscopic method.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/elan.1140091006
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  • 6
    Digitale Medien
    Digitale Medien
    Anodic stripping voltammetry at hydrodynamic mercury thin film electrodes. Numerical simulation of stripping peaks for reversible processes at uniformly accessible electrodes (1997)
    Weinheim : Wiley-Blackwell
    Electroanalysis 9 (1997), S. 765-769 
    Details
    ISSN: 1040-0397
    Schlagwort(e): Anodic stripping voltammetry ; Numerical simulation ; Hydrodynamic electrodes ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The time dependent backwards implicit method is used to simulate the shape and position of the stripping peaks in DC (linear scan) anodic stripping voltammetry at mercury thin film hydrodynamic electrodes for electrochemically reversible systems. The effect of variable diffusion layer thickness, assumed uniform and experimentally controllable in the case of rotating disk systems, in influencing both the peak potential and peak shape, is quantified and the implications for anodic stripping voltammetry under convective conditions noted.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/elan.1140091007
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  • 7
    Digitale Medien
    Digitale Medien
    Voltammetric monitoring of photochemical reactions: Photo-induced electron transfer to p-chloronitrobenzene (1996)
    Weinheim : Wiley-Blackwell
    Electroanalysis 8 (1996), S. 515-518 
    Details
    ISSN: 1040-0397
    Schlagwort(e): Photo-induced electron transfer ; Photochemistry ; Channel electrodes ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Channel electrode voltammetry using an irradiated gold electrode is used to study the photolysis of p-chloronitrobenzene in aqueous ethanolic solution in the presence of the hydroxide anion. The formation of the stable radical anion, [p-CIC6H4NO2]•-, via light-induced electron transfer is demonstrated and kinetic parameters are reported.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/elan.1140080603
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  • 8
    Digitale Medien
    Digitale Medien
    Applications of the channel flow cell for UV-visible spectroelectrochemical studies: The kinetics of dimerization of the methyl viologen radical cation (1997)
    Weinheim : Wiley-Blackwell
    Electroanalysis 9 (1997), S. 219-224 
    Details
    ISSN: 1040-0397
    Schlagwort(e): Spectroelectrochemistry ; Methyl viologen ; Dimerization ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A channel flow cell specifically designed for ultraviolet-visible spectroelectrochemical experiments is described. The performance of the cell was characterized using the oxidation of N,N, N′, N′-tetramethyl-p-phenylenediamine in aqueous electrolytes and excellent agreement between theory and experiment was obtained. The technique was applied to study the dimerization rate of methyl viologen radical cations. The mechanistic results confirm that the electrogenerated methyl viologen radical cation dimerizes rapidly in aqueous solution and a previously unknown dimerization rate constant close to 104 M-1 s-1 is reported.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/elan.1140090306
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  • 9
    Digitale Medien
    Digitale Medien
    Microband electrodes of ideal and nonideal geometries: AC impedance spectroscopy (1996)
    Weinheim : Wiley-Blackwell
    Electroanalysis 8 (1996), S. 30-33 
    Details
    ISSN: 1040-0397
    Schlagwort(e): Microband electrodes ; Diffusion ; Ultramicroelectrodes ; AC impedance spectroscopy ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The 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.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/elan.1140080107
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  • 10
    Digitale Medien
    Digitale Medien
    The mechanism of the electro-reduction of some azo dyes (1996)
    Weinheim : Wiley-Blackwell
    Electroanalysis 8 (1996), S. 519-523 
    Details
    ISSN: 1040-0397
    Schlagwort(e): Azo dyes ; Reduction ; Mechanism ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The pH dependence of the reduction mechanism of the azo dyes Orange G and Sunset Yellow FCF was investigated using a mercury plated rotating disk electrode, The reduction was shown to proceed via a CE mechanism except at very high pH, where direct reduction was observed. It is proposed that the chemical step of the CE reaction, namely protonation of the azo bond, could occur either intramolecularly, via azo/hydrazone tautomerism, or intermolecularly from bulk solution. At low pH the protonation from free H+ predominated while above neutral pH, until deprotonation of the ortho hydroxyl group involved in the tautomerism, the intramolecular mechanism was more prevalent. The kinetic parameters for the chemical steps in each of the two protonation mechanisms were determined.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/elan.1140080604
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