Spectrophotometric determination of captopril in dosage form via charge-transfer complexes

ABSTRACT

Two simple and sensitive spectrophotometric methods for the assay of captopril have been presented. The first is based on the reaction of captopril with iodine to give a molecular charge-transfer complex. The second method depends on the formation of a highly colored stable radical anion between captopril and 7,7,8,8-tetracyanoquinodimethane [TCNQ] as a pi-electron acceptor. The molecular ratios of the reactants in the complexes as well as the experimental conditions leading to maximum charge-transfer b and s have been studied. Beer's Law is obeyed over captopril concentration range of 2-8 mug.ml -1 by iodine method and 0.32-3.2 mug.ml -1 by TCNQ method. The proposed procedures have been applied successfully to the analysis of captopril tablets and the results are in agreement with those of official methods: