A steady-state voltammetric investigation on the oxidation of ferrocene inethanol-water mixtures

The oxidation process of ferrocene was studied in ethanol-water mixtures, u nder steady-state conditions, with platinum and carbon microdisk electrodes . The electrode process was found to be essentially reversible in mixtures up to 60 vol.% water. In media with a larger water content, a weak adsorpti on of the reactant was involved. Half-wave potentials determined with both microelectrodes, quoted against an aqueous Ag\AgCl (KCl saturated) referenc e electrode, shifted towards less positive values as the water content was increased. In contrast, the halfwave potential referenced against the cobal tocenium\cobaltocene system was calculated to be -1.318 (+/- 0.005) V, inde pendent of the medium composition. The limiting current, at a given concent ration of ferrocene, strongly depended on the medium composition and mainly reflected the change of viscosity of the media. The overall results allowe d us to conclude that ferrocene can be used as a voltammetric standard in t he mixtures examined. (C) 1999 Elsevier Science S.A. All rights reserved.