APPLICATION OF NEW FERROCENE DERIVATIVE FOR ELECTROCATALYTIC DETERMINATION OF CAPTOPRIL USING MULTIWALL CARBON NANOTUBE MODIFIED CARBON PASTE ELECTRODE

A carbon-paste electrode modified with the N-4,4'-azodianiline (ferrocenyl Schiff base) and with multiwall carbon nanotubes was used as a highly sensitive and fairly selective electrochemical sensor for trace level determination of captopril. This modified electrode shows very efficient electrocatalytic activity for anodic oxidation of captopril via substantially decreasing of anodic overpotential. The measurements carried out by application of electrochemical impedance spectroscopy, differential pulse voltammetry, cyclic voltammetry and chronoamperometry. It has been found that under optimum conditions, the oxidation of captopril occurs at potential less positive than the unmodified carbon paste electrode. The kinetic parameters such as electron transfer coefficient (a) and rate constant for chemical reaction between captopril and redox sites in the modified electrode were 0.31 and 1.82 x10(2) cm(3) mol(-1) s(-1), respectively. The catalytic peak current was linearly dependent on the captopril concentration in the range of 0.1-625.0 mu mol L-1 with a detection limit of 0.03 mu mol L-1. Finally, the modified electrode was examined as a selective, simple, and a precise new electrochemical sensor for the determination of captopril in real sample, such as urine, with satisfactory results.