Potentiometric determination of captopril.

A rapid, accurate and reproducible method for the potentiometric determination of captopril in aqueous solution, is described. The method is based on the reaction of the thiol and the carboxylic group of captopril with silver ions whereby an equivalent amount of the acid is liberated; thereafter, the amount of captopril is determined by the potentiometric titration with sodium hydroxide. This method can be applied also for direct determination of captopril content in tablets.