Electrochemical oxidation of phenothiazine derivatives at glassy carbon electrodes and their differential pulse and square-wave voltammetric determination in pharmaceuticals

Three 2,10-disubstituted phenothiazines - chlorpromazine hydrochloride (CPM), thioridazine hydrochloride (TR) and propericiazine (PRC) - were electrochemically studied in various buffer systems at different pH values, using a glassy carbon electrode. The substances were electrochemically oxidized at potential range 0.55-0.75V. The oxidation was reversible and exhibited diffusion-controlled process. The mechanism of the oxidation process is discussed. According to the linear relation between peak current and concentration, differential pulse voltammetry (DPV) and square wave voltammetry (SWV) methods for quantitative determination of chlorpromazine and propericiazine in 0.1M HClO4, and thioridazine in pH 2 phosphate buffer, was applied. Both the repeatability and reproducibility of the methods were also determined for all studied substances. The developed procedures were successfully applied to the determination of chlorpromazine and thioridazine in pharmaceutical dosage forms.