Study of the electro-oxidation of a recreational drug GHB (gamma hydroxybutyric acid) on a platinum catalyst-type electrode through chronoamperometry and spectro-electrochemistry

Abstract

The electro-oxidation of gamma-hydroxybutyric acid (GHB) on a polycrystalline platinum electrode in acidic medium has been studied using chronoamperometry and spectroelectrochemistry. The study has been performed in a wide interval of potentials and at different concentrations.It was found that at longer times the density currents reached stationary values over 0.3V whereas it is zero to potentials below the above mentioned. These characteristics in the j–t curves suggest a different mechanism for the electro-oxidation of GHB, potential dependent, with a catalytic process and an adsorption process controlled by mass transport in the respective potential regions indicated.The change in the stationary current obtained at +0.9V with variable GHB concentrations also suggests an oxidation mechanism catalysed by the platinum surface with platinum hydroxides acting as reaction intermediates to make the final oxidation product for GHB. The results obtained using chronoamperometry are in good agreement with those obtained using cyclic voltammetry where the alcohol group is oxidized at different potentials.In situ surface enhanced Raman scattering (SERS) spectra corresponding to GHB intermediates and water adsorbed species being formed/consumed at the potential-dependent adsorption processes have been analysed using spectro-electrochemistry. A peak at 1590cm−1, corresponding to the asymmetric stretching of carboxylic group in a bridge configuration, increases with the potential. This supports the hypothesis of a mechanism of formation of the succinic acid on the platinum surface as reaction product under the experimental conditions studied.