Author(s): Bharat G. Chaudhari
A simple and economical dual wavelength spectrophotometric method has been developed for the simultaneous estimation of amlodipine besylate and enalapril maleate in their combined dosage forms. The method was based on property of additivity of absorbances. From the UV absorption spectrum of amlodipine besylate, three wavelengths were selected, which were 226.6, 247.8 and 360.6 nm. From the UV absorption spectrum of enalapril maleate, 226.6 and 247.8 nm wavelengths were selected. At 360.6 nm only amlodipine besylate has reasonable absorbance, so it was selected for the estimation of it from combination drug product. At 226.6 and 247.8 nm both drugs had shown some absorbance. At these two wavelengths absorbance for amlodipine besylate was found to be same i.e. absorbance difference was zero for any concentration, while for enalapril maleate concomitantly increase in absorbance difference with increase in its concentration. So, 226.6 and 247.8 nm wavelengths were selected for the estimation of enalapril maleate from its combination drug product. The method involved solving of an equation based on measurement of absorbances at two wavelengths 226.6 and 247.8 nm. The proposed method was found to be simple, economical, accurate and reproducible for the routine analysis of both drugs in tablet dosage forms.