The voltammetric study of 2-mercapto-5-phenylammino-1,3,4-thiadiazole using carbon paste electrodes

A rapid and accurate voltammetric method for the quantitative determination of 2-mercapto-5-phenylammino-1,3,4-thiadiazole (MPATD) with carbon paste electrodes (CPE) has been developed. The study was made by cyclic voltammetry between -0.4 and +0.6 V with 50 mV s(-1) sweep rate in aqueous solution. After successive oxidation/reduction cycles we found a total oxidation of MPATD at +0.45 V. As the compound is oxidated, the reduction current peak increases at +0.13 V, indicating an irreversible process. Following only the oxidation process in the -0.1 to +0.6 V range, we investigated the optimum scan rates at different current densities and pH values (realised with buffers, pH between 1.0 and 10.0) with CPE versus Ag/AgCl reference electrode using linear sweep voltammetry. We found a good linear relation between the current peak height and concentration in a 2.5 x 10(-9)-1.25 x 10(-7) mol ml(-1). This method allows the quantitative detection of the MPATD as it or from dosage forms and biological media.