RESOLUTION OF ASCORBIC-ACID OR CATECHOLAMINE AND INDOLE ALKALOID MIXTURES BY PULSE VOLTAMMETRY AT HIGHLY POLISHED GLASSY-CARBON

Metallographic polishing of glassy carbon electrodes (GCEs) yields wel l-defined oxidation peaks for two- and three-component mixtures of asc orbic acid, dopamine (DA), catechol, and hydroquinone. Linear calibrat ion plots of differential pulse voltammetric current versus concentrat ion were obtained for each component at a range of 0.4 to 10 muM. Dete rioration of voltammograms was observed when highly polished GCE was a ged in solution, resulting in positive shifts and broadening of the pe aks. Lower limits of detection (LLD) in water at pH 7 were about 0.01 muM for DA and 1 muM for AA. Highly polished GCEs were further applied to mixtures of naturally occurring indole alkaloids.