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An electrochemical sensor based on molecularly imprinted polypyrrole membrane is reported for the determination of dapsone (DDS). The sensor was prepared by electropolymerization of pyrrole at a glassy carbon electrode in the presence of DDS as a template. The electropolymerization was performed in the presence of an aqueous solution of 0.1 M HCl, and 0.2 M pyrrole, with and without a template molecule (DDS) at a glassy carbon electrode using cyclic voltammetry. Some of the parameters, important to controlling the performance of the polypyrrole, were investigated and optimized, including the effects of pH, monomer and template concentrations, electropolymerization cycles. The molecularly imprinted film exhibited a high selectivity and sensitivity toward dapsone. The differential pulse voltammetry (DPV) peak current showed a linear dependence on the DDS concentration and a linear calibration curve was obtained in the range 1.0 μM to 110 μM of DDS with a correlation coefficient of 0.998 with a detection limit of 3.0 × 10 −7 M (S/N = 3). The electrode was successfully applied to the determine Dapsone in spiked human serum and urine.

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Electrochemical oxidation of catechol (1) has been studied in the presence of benzoylnitromethane (2a), benzoylacetonitrile (2b), benzoylacetone (2c) and dibenzoylmethane (2d) as nucleophiles in water/acetonitrile (60/40, v/v) solution, by means of cyclic voltammetry and controlled-potential coulometry.The results indicate the participation of electrochemically generated o-benzoquinone (1ox) in the Michael addition reaction with nucleophiles 2a -d, to form the corresponding benzofuran derivatives. Based on the EC mechanism, the observed homogeneous rate constants (k obs ) of the reaction of o-benzoquinone (1ox) with CH-acid nucleophiles (2a -d) were estimated by comparing the experimental cyclic voltammograms with the digitally simulated results. The calculated observed homogeneous rate constants (k obs ) were found to vary in the order 2a > 2b > 2c > 2d.

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