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Spectrophotometric Determination Of Lisinopril In Pharmaceutical Preparations Assisted By Microwave Oven

Asad Raza

In this work, two effective and low-cost spectrophotometric methods (A and B) for the determination of lisinopril are proposed in its pure and pharmaceutical preparations. The both methods depend on the charge-transfer reaction between lisinopril as n-electron donor with 2,3- dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) in methanol medium and 7,7,8,8-tetracyanoquinodimethane (TCNQ) ) in methanol-acetonitrile medium as p-acceptor to give a colored complex, which absorb maximally at 475 nm and 740 nm respectively. These reactions were accelerated by irradiating the reaction mixtures with microwave energy (1100 W) during 45 seconds in method A and two minutes in method B. Beer’s law is obeyed in the concentration ranges 0.5-60 μ mg/mL with molar absorptivity of 1.2 × 105 L mole-1 cm-1 and 0.5-15 μ mg/mL with molar absorptivity of 8.3 × 104 L mole-1 cm-1 respectively. The optimal reaction conditions values such as reagent concentration, heating time and stability of the reaction product were determined. The analytical results obtained by applying the proposed method compare very favorably with those given by the British Pharmacopoeia standard procedure.