Mercurimetric and Polarographic Determination of Captopril

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Abstract
Two different methods have been applied for the determination of captopril, namely,(i) a direct mercurimetric method using standard mercuric nitrate solution and diphenyl carbazone as an end-point indicator (ii) a differential pulse (DP50) polarographic method based on the measurement of the polarographic current at the peak potential of - 0.25V vs. Ag/AgCl (Kcl Sat.) reference electrode using acetate buffer of pH U.6 as a supporting electrolyte containing 0.01% w/v gelatin as a maximum suppressor. The accuracy obtained for the mercurimetric method is 99.8±0.7% and 100.2±1.3% for the authentic captopril and its tablets respectively. For the polarographic method, the linearity between current and concentration holds for the concentration range 2 to 45 ppm under the experimental conditions employed with an accuracy of 99. 4±0.8% and 99.9±1.9% for the authentic captopril and its tablets respectively.