Resumo

MORDIDO, S.C.  e  REBELO, M.J.F.. Electrochemistry of caffeic acid in acetate-ethanolic solutions. Port. Electrochim. Acta [online]. 2006, vol.24, n.2, pp.313-322. ISSN 0872-1904.

The electrochemical behaviour of caffeic acid in acetate solutions with and without added ethanol was studied by cyclic voltammetry. Solutions of pH and ethanol content close to the wine values (3.5 and 12%, respectively) were studied as a first model approach, pursuing work previously done. Studies at pH 7.4 and different ionic strengths were also done. It was found that cyclic voltammograms of caffeic acid acetate ethanolic solutions had oxidation peak potential values (≈ 470 mV) at pH 3.5 irrespective of the previous excursions of potential with the same set of electrodes. However, the cathodic peaks potentials and currents strongly depended on the cyclic voltammogram of the corresponding solvent electrolyte which had previously been run. The separation of oxidation and reduction peak potentials evidenced the presence of dimmers of caffeic acid in solution, under the following conditions: 0.1 mol dm^-3 acetate buffer pH 3.5 + 12% ethanol with the ionic strength increased by the addition of 0.05 mol dm^-3 KCl; limits of the anodic potential: from -100 to + 700 mV and N₂ bubbled through the solution for 10 minutes.

Palavras-chave : caffeic acid; acetate buffer; ethanol; cyclic voltammetry.

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