Flow-injection spectrophotometric system for captopril determination in pharmaceuticals

A simple, accurate and precise flow-injection spectrophotometric procedure is reported for the determination of captopril in pharmaceutical formulations. In this procedure, captopril was oxidized by iron(III) and the iron(II) produced was spectrophotometrically monitored as iron(II)1,10-phenantroline complex at 540 nm. The analytical curve for captopril was linear in the concentration range from 1.0 x 10(-5) to 8.0 x 10(-4) mol L-1 with a detection limit of 5.0 x 10(-6) mol L-1. The recovery of this analyte in five samples ranged from 98.5 to 102.4%. The analytical frequency was sixty determinations per hour and the RSD was less than 0.2% for a captopril concentration of 4.0 x 10(-4) mol L-1 (n = 10). A paired t-test showed that all results obtained for captopril in commercial formulations using the proposed flow injection procedure and a potentiometric procedure agreed at the 95% confidence level.