Catechol as an electrochemical indicator for voltammetric determination of D-penicillamine in aqueous media at the surface of carbon paste electrode

The utilization of catechol as an electrochemical indicator for the presence of D-penicillamine (D-PA) at a carbon paste electrode (CPE) has been investigated in aqueous media using cyclic voltammetry (CV), differential pulse voltammetry (DPV) and double step potential chronoamperometry methods. The results show that D-PA participates in Michael type addition reaction with electrogenerated quinone from electrooxidation of catechol at CPE to form the corresponding thioquinone derivative. The reoxidation of the adduct leads to the increase in the oxidative current which is proportional to the concentration of D-PA. Therefore, in the optimum condition (pH 7.00) by CV, the oxidation of D-PA occur at a potential about 343 mV less positive than that in the absence of catechol at the surface of CPE. The practical utility of the method showed much reproducible responses, short response time, low detection limit and high sensitivity for determination of D-PA. The proposed method is useful for the routine analysis of D-PA in pharmaceutical formulations.