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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.

Two proposed methods have been described for the determination of prenalterol hydrochloride in acetate buffer (pH=4.1) as authentic material and in tablets form using a (i) colorimetric method based on reduction of ferric iron by prenalterol hydrochloride and subsequent measurement at 511 nm of the red color obtained by the treatment of the resultant ferrous iron with 1, 10-orthophenanthroline, (ii) a differential pulse polarographic method based on nitrosation with 0.1 M NaNO2/dil. HC1 and consequent recording of the differential pulse polarogram. The differential polarogram was obtained under constant amplitude pulses of 50 mV (DP 50) superimposed on a linearly increasing DC-voltage ramp. The peak height (h), of the polarogram was measured at the peak potential of -0.2V on the dropping mercury electrode (DME) versus Ag/AgCl reference electrode. The linearity ranges observed are 0.6μgfml to 6.0μg/ml and 2μg/ml to 12μg/ml, respectively. The mean percentage recoveries for an authentic sample are 9...