CONICET | Buscador de Institutos y Recursos Humanos

The electro-oxidation of ochratoxin A (OTA) mycotoxin is studied at glassy carbon (GC) electrodes in 10% acetonitrile (ACN) + 90% 1 M HClO4 aqueous solution by cyclic (CV) and square wave (SWV) voltammetries. Under these experimental conditions, the adsorptive accumulation of its electrochemical oxidation product was found. A quasi-reversible redox couple of surface nature was detected and studied by both, CV and SWV. The Frumkin adsorption isotherm resulted in being the best one to describe the specific interaction of OTA oxidation product with GC electrodes. Values for the adsorption standard free energy (∆G°) and the adsorbed species interaction parameter (g*) were obtained from results of the best fitting of experimental data by a nonlinear least square procedure. In addition, from the width at half height of cyclic voltammograms an exchanged electron number of two per mole of electroactive adsorbed substance was obtained. From the variation of anodic and cathodic peak potentials of cyclic voltammograms recorder in solutions of different pH, after the accumulation of OTA electrochemical oxidation product at GC electrodes in the highly acidic medium, an apparent 2 e-, 2 H+ exchange could be inferred. SWV was employed to perform a full thermodynamic and kinetics characterization of the adsorbed redox couple by using the combination of the ?quasi-reversible maximum? and ?the splitting of SWV peaks? methods. Thus, average values of the formal potential, the anodic transfer coefficient and the overall formal rate constant of adsorbed OTA electrochemical reaction product were determined for the overall two-electron redox process. SWV was employed to generate calibration curves. The lowest concentration value measured for a signal to noise ratio of 3:1 was 1,24 x 10-8 mole dm-3 (ppb).

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