A Theoretical and Experimental Square-Wave Voltammetric Study of Ascorbic Acid in Light of Multi-Step Electron Transfer Mechanism

Abstract

A detailed theoretical and experimental study of the complex redox mechanism of ascorbic acid in aqueous phosphate buffer solution (pH = 7.3) by square-wave voltammetry is presented. Experimental square-wave voltammograms at edge plane pyrolytic graphite electrode consist of a typical irreversible peak for a direct two-step electrode oxidation of the ascorbic acid. The complex mechanism of oxidation of the ascorbic acid was represented by a theoretical model for E1C’E2C mechanism. Morphology of theoretical square-wave voltammograms greatly depended on different specific parameters of the model. This feature was used to make the best fit between experimental and theoretical voltammograms for 2 different step potentials, which resulted in revelation of all specific parameters (standard electrochemical rate constant, diffusion coefficient, electron transfer coefficient and rate constants for both chemical reactions) of the model. Therefore, we showed that using only square-wave voltammetry, both experimentally and theoretically, it is possible to make a detailed study of the complex oxidation of ascorbic acid and further enlighten its redox mechanism.