Fast and sensitive determination of captopril by voltammetric method using ferrocenedicarboxylic acid modified carbon paste electrode

A ferrocenedicarboxylic acid modified carbon paste electrode was constructed and used as a fast and sensitive tool for the determination of captopril at trace level. It has been shown by direct current cyclic voltammetry and double step chronoamperometry that ferrocenedicarboxylic acid can catalyze the oxidation of captopril in aqueous buffer solution and produces a sharp oxidation peak current at about +0.49 vs. Ag/AgCl reference electrode. The square wave voltammetric peak currents of the electrode increased linearly with the corresponding captopril concentration in the range of 3.0 x 10(-7)-1.4 x 10(-4)M with a detection limit of 9.1 x 10(-8) M. The influence of pH and potential interfering substances on the determination of captopril were studied. Electrochemical impedance spectroscopy was used to study the charge transfer properties at the electrode-solution interface. Finally, the sensor was examined as a selective, simple, and precise new electrochemical sensor for the determination of captopril in real samples, such as drug and urine, with satisfactory results.