Titrimetric determination of captopril in dosage forms

Two titrimetric methods are proposed for the determination of captopril in pure form or in tablets. In the first method iodide selective electrode is used for indirect titrimetric assay of captopril. This compound forms silver salt in presence of excess silver ions, the excess silver ions are determined potentiometrically with standardized iodide solution and an iodide selective electrode. The second method involves the titrimetric determination of captopril using a new oxidimetric titrant 2.3-dichloro-5.6-dicyano-1.4-benzoquinone (DDQ) in anhydrous acetic acid. The equivalent point is detected potentiometrically using calomel and platinum electrodes. The two methods allow semimicro-determination of captopril, the results by the proposed procedures are in good agreement with those obtained by the official method.