Carbon-paste electrode modified with cobalt-5-nitrolsalophen as a sensitive voltammetric sensor for detection of captopril

The electrochemical behavior of captopril at the surface of a carbon-paste electrode (CPE) modified with cobalt-5-nitrolsalophen (CoNSal) is described. The prepared electrode shows an excellent electrocatalytic activity toward the oxidation of captopril, which is leading to marked lowering in the anodic overpotential and considerable improvement of sensitivity (anodic current). Whereas at the surface of unmodified electrode an electrochemical activity for captopril cannot be observed, a very sharp anodic wave with an anodic peak potential about 650 mV (versus Ag/AgCl) is obtained using the prepared modified electrode. This catalytic wave is assigned to mediating of Co(III)/Co(II) redox couple in the anodic oxidation of captopril. The substantial decrease in the overvoltage and significant improvement of anodic peak current for captopril associated with high stability of CoNSal in the matrix of modified CPE (compared to cobalt salophen); allow the development of a highly sensitive voltammetric sensor for the detection of captopril. The resulted electrode is used for the voltammetric determination of captopril pharmaceutical and clinical (human serum) preparations. The results show that a very good precision (R.S.D. < 2.5%) and very stable voltammetric response toward captopril.