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  • 1
    ISSN: 1040-0397
    Schlagwort(e): Methyl viologen ; Pyrex glass ; Adsorption ; Nafion ; Renewable electrode ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Square wave voltammograms of methyl viologen (MV2+) were recorded at a renewable Nafion-loaded carbon paste electrode immersed in 20 mL of phosphate buffer solution (pH 7.4) contained in a beaker-type electrochemical cell (Pyrex glass; contact area = 33 cm2). From the calibration plot obtained in the concentration range 0.01-2.4 μM, it could be concluded that the maximum surface excess of MV2+ adsorbed on Pyrex glass (0.24 nmol cm-2) was reached at concentrations above 1.4 μM. The adsorption isotherm presented a sigmoidal shape characteristic of attractive interaction. From this plot, it was evaluated that the maximum depletion of MV2+ in solution (28%) did not occur at the lowest concentrations, but in nearly micromolar solutions. This result emphasizes the unavoidable and random errors which are involved when MV2+ solutions are purposely diluted in Pyrex glassware. The MV2+ adsorption proceeds to a less extent on Duran borosilicate glass and/or in acid or alkaline medium.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 0268-2605
    Schlagwort(e): Cobaltocenium ; Nafion ; nortriptyline ; biotin ; desipramine ; square-wave voltammetry ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A cobaltocenium label was covalently attached to two antidepressants, nortriptyline and desipramine, via an amide linkage, and also to the hydrazine derivative of the biologically important compound biotin (vitamin H), again via an amide linkage. Analytically pure samples of these new cobaltocenium salts could be obtained by chromatography on silica gel followed by elution with aqueous acetone solutions containing sodium chloride (NaCl). These positively charged cobaltocenium ions preconcentrate in a polyanionic Nafion film coated on a glassy carbon surface, albeit at different concentration levels. One factor which seems to influence the amount of cobaltocenium ion that enters the film is polarity since the cobaltocenium ion containing the rather polar biotin preconcentrates at the lowest level in the relatively hydrophobic Nafion. Square-wave voltammograms of Nafion films containing these cobaltocenium cations exhibit a one-electron, reversible, reduction wave at approximately -1.1 V (vs Ag/AgCl) with peak currents that are sufficiently large to permit detection of 10-8 M quantities of these substances in the bulk solution.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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