HPTLC method for the simultaneous determination of amlodipine and benazepril in their formulations

A new, simple, precise, rapid, and selective high-performance thin-layer chromatographic (HPTLC) method is developed for the simultaneous analysis of amlodipine and benazepril in pharmaceutical formulations. The method uses zolpidem as an internal standard (IS). The stationary phase used is silica gel 60 F254 prewashed with methanol. The mobile phase consists of an ethyl acetate-methanol-ammonia solution (8.5:2.0:1.0, v/v/v). Detection and quantitation are performed densitometrically at lambda = 254 nm. The Rf values of amlodipine, benazepril, and zolpidem (IS) are 0.58, 0.50, and 0.78, respectively. The limits of detection of amlodipine and benazepril are 0.02 and 0.2 microg; linearity ranges are 0.1-0.8 and 0.2-2.0 microg; and the percentage recoveries are 99.79% and 100.25%, respectively.