Spectrophotometric Determination of Captopril in Pharmaceutical Formulations based on Ion-Pair Reaction with the Red Congo

Abstract

A simple and sensitive spectrophotometric method has been proposed for the determination of captopril. The method is based on ion coupling between Congo Red and captopril, giving an intense violet color at 15°C. The colored product is quantified by spectrophotometry at 596 nm. Optimization of experimental conditions is described. The method was used to estimate 1-60 μg/ml of captopril. The accuracy of the method is achieved by mean recovery (97.446%) and accuracy is supported by relative standard deviation values (0.06-0.965%). The sensitivity of the method is indicated by the molar absorptivity (5757.92) L mol-1 cm-1The results of the method are compared with the formal method. The interaction of common drug additives was also studied. The proposed method is successfully applied for the determination of captopril in pharmaceutical.