Different ratio spectra methods for simultaneous determination of Olmesartan Medoxomil, Hydrochlorothiazide and Amlodipine Besylate

Abstract

New, simple and specific spectrophotometric methods involving Direct spectrophotometric method ,derivative ratio spectra-zero-crossing method [DRSZ] double divisor ratio spectra derivative method [DDRD], and successive ratio spectra were developed and validated in accordance with ICH guidelines for the simultaneous estimation of Olmesartan Medoxomil [OLM], Amlodipine Besylate [AMLB], and Hydrochlorothiazide [HCTZ] in their combined pharmaceutical dosage form. First, Amlodipine [AMLB] was determined by direct spectrophotometry at 356.0 nm alone without any interference from OLM, and HCTZ. In the DRSZ method OLM, HCTZ, and AMLB were determined at 259.0nm, 279.0nm, and 358.0nm respectively, in the DDRD method OLM, HCTZ, and AMLB were determined at 266.0nm, 317.0nm, and 363.0nm respectively, and in the  successive ratio spectra  OLM, HCTZ, &AMLB were determined at 239.0nm, 276.0nm, and 375.0nm respectively. The calibration curves are linear over the concentration range of 5-50 µg mL^-1 for OLM, HCTZ, and AMLB respectively for all methods. The proposed methods were successfully applied for the assay of the three analytes with excellent recoveries in Laboratory prepared mixtures. No interference was observed from common pharmaceutical additives.  The methods are validated according to the ICH guidelines where accuracy, precision and repeatability are found to be within the acceptable limit.