Stability Indicating RP-HPLC Studies for the Estimation of Irbesartan and Amlodipine Besylate in Pharmaceutical Formulations and Identification and Characterization of Degradants Using LC-MS

Abstract

A simple, specific, accurate, and stability-indicating reversed-phase high-performance liquid chromatography method was developed for simultaneous estimation of irbesartan and amlodipine besylate in pharmaceutical formulations. The chromatographic separation was achieved on a Zorbax CN column using a mixture of 1 mM potassium dihydrogen phosphate (pH 3.0) and acetonitrile (70:30, v/v) as the mobile phase at a flow rate of 0.9 mL/min. Detection was carried out at 240 nm. The calibration curves were linear (R 2 ≥ 0.99) over a concentration range of 6–42 µg/mL for irbesartan and 2–14 µg/mL for amlodipine besylate. The retention times of irbesartan and amlodipine besylate were 9.6 and 7.6 min, respectively. For stability studies, irbesartan and amlodipine besylate stock solutions were subjected to acid, alkali hydrolysis, chemical oxidation, and dry heat degradation. The degraded product peaks were well resolved from the pure drug peak with significant difference in their retention times and resolution. To elucidate structures of degradation products, the LC-MS method was used. The proposed method was successfully validated in accordance to the ICH guidelines acceptance criteria.