Application of π-acceptors to the spectrophotometric determination of lisinopril in commercial dosage forms

Two simple, rapid and sensitive spectrophotometric methods have been proposed for the determination of lisinopril in pure form and pharmaceutical formulations. The methods are based on the charge transfer complexation reaction of the drug with 7,7,8,8,tetracyanoquinodimethane (TCNQ) and p-chloranilic acid (pCA) in polar media. The lisinopril-TCNQ and lisinopril-pCA charge transfer complexes dissociate in acetone and methanol, respectively, and yield coloured TCNQ and pCA radical anions which are measured spectrophotometrically at 743 and 525 nm. Under optimised experimental conditions, Beer's law is obeyed in the concentration range of 2-26 and 25-300 μg ml-1 with molar absorptivity of 1.432 × 104 and 1.192 × 104 l mol-1 cm-1 for TCNQ and pCA methods, respectively. Both the methods have been applied to the determination of lisinopril in pharmaceutical dosage forms. Results of analysis are validated statistically.