Electrochemical oxidation of L-dopa at a carbon paste electrode

Abstract

The electrochemical oxidation pathway of levodopa and methyl dopa at a carbon paste electrode in a pyrophosphate buffer medium has been studied. The catechol moiety in both the compounds undergoes a two-electron oxidation to give dopaquirtone. The effects of varying pH, sweep rate. concentration of the electroactive species and temperature on the electrochemical behavior of levodopa and methyl dopa have been discussed. Much sharper peaks were obtained on carbon paste electrode as compared with glassy carbon electrode. The signal was enhanced on addition of cationic and anionic surfactants while non-ionic surfactant decreased the peak current This behavior, which is different from that observed at the glassy carbon electrode, makes it possible to determine wry low concentrations of levodopa. The effect of addition of surfactants can be a consideration for the selective determination of levodopa in the presence of ascorbic acid present in biological systems. A method for the electrochemical determination of dopa in pharmaceutical formulations is developed using differential pulse voltammetry.