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Simple And Rapid Methods For The Analysis Of Captopril In Dosage Form

A.C.Sharada, H.Chandru

Two indirect methods are described for the micro determination of captopril using hexacyanoferrate (III) as reagent. Titrimetry involves the addition of a known excess of hexacyanoferrate (III) to the sample solution and back titration of the residual reagent iodometrically in the presence of a large excess of zinc sulphate, after the specified time. In spectrophotometry, the sample solution is treated with a large excess of hexacyanoferrate (III) and after specified time, hexacyanoferrate (II), the reduced form of the reagent was reacted with orthophenanthroline, and the absorbance of the resulting red colour measured at 510 nm, which forms the basis for the quantitative determination of captopril. The reaction used for titrimetry proceeds at room temperature and will be complete in 10 minute with a stoichiometry of 1:1 with respect to the oxidant and captopril. The reaction product used for spectrophotometric determination shows the absorption maximum at 510 nm. The Beer’s law is obeyed over the concentration range 0.25-12.00 μg ml-1, the molar absorptivity and Sandell sensitivity for the system being 9.14×103 l mol-1cm-1 and 23.78 ng cm-2, respectively. The limit of detection and quantification are found to be 0.08 and 0.26 μg ml-1, respectively. Both procedures have been applied to the determination of captopril in tablets. The results have been statistically compared with those obtained by the official (BP) method.