Flow-injection iodimetric determination of captopril in pharmaceutical preparations

a simple, fast and low cost procedure for spectrophotometric determination of captopril in pharmaceutical preparations is described. the procedure is based on a flow-injection system exploiting the on-line formation of the triiodide reagent, which is consumed in the presence of the analyte generating a transient signal. linear response was observed up to 200 μmol l-1 with a detection limit of 1.0 μmol l-1 (99.7% confidence level). the coefficient of variation (n = 20) and the sampling rate were estimated as 1.2% and 72 determinations per hour, respectively. the main excipients found in pharmaceutical preparations did not affect the captopril determination. the zone sampling approach was exploited to implement on-line dilutions, aiming direct analysis of sample extracts. results of the analysis of commercial samples agreed with the obtained by the titrimetric reference procedure described in the us-pharmacopeia at the 95% confidence level. the reagent consumption was estimated as 18 μg of kmno4 and 10 mg of ki per determination, with a cost of us$ 2.50 per 1000 determinations.