Highly Selective and Sensitive Voltammetric Sensor for Captopril Determination Based on Modified Multiwall Carbon Nanotubes Paste Electrode

A new sensitive voltammetric sensor was developed for electrochemical determination of captopril (CAP) at a modified multiwall carbon nanotubes paste electrode with p-aminophenol (p-APMCNTPE). The result showed that p-APMCNTPE has high electrocatalytic activity for captopril oxidation at pH 6.0. Cyclic voltammetry (CV), double potential-step chronoamperometry and square wave voltammetric (SWV) were used to investigate the suitability of p-aminophenol into carbon nanotubes paste matrix as mediator for the electrocatalytic oxidation of CAP in aqueous solution. It has been found that under the optimum condition (pH 6.0), the oxidation of captopril occurred at a potential ca. 200 mV at p-APMCNTPE. The kinetic parameters, such as electron transfer coefficient and catalytic reaction rate constant, were also determined using the electrochemical approaches. Under optimized conditions, the electrocatalytic oxidation peak current of captopril showed two linear dynamic ranges, 5.0 x 10(-8) to 5.0 x 10(-7) and 5.0 x 10(-7) to 5.0 x 10(-5) mol L(-1) using SWV. The limit of detection was 2.0 x 10(-8) mol L(-1). Finally, the modified electrode was also examined as a selective, simple and precise new electrochemical sensor for the determination of captopril in real samples, such as pharmaceutical preparation and urine.