STABILITY INDICATING HPTLC METHOD DEVELOPMENT AND VALIDATION FOR SIMULTANEOUS ESTIMATION OF AMLODIPINE BESYLATE AND LOSARTAN POTASSIUM AND CHARACTERISATION OF ACID DEGRADANT PRODUCT OF LOSARTAN

An accurate, precise, sensitive and selective stability indicating High-Performance Thin Layer Chromatographic method has been developed and validated for simultaneous estimation of Amlodipine besylate (AML) and Losartan potassium (LOS) in bulk and pharmaceutical dosage formulation. Chromatographic separation of both the drugs was achieved by using TLC aluminum plates pre-coated with silica gel 60 F₂₅₄ as the stationary phase and chloroform: methanol: toluene: acetic acid (5.5: 2.5: 2: 0.05 v/v/v/v) as mobile phase. Densitometric analysis was carried out in the absorbance mode at 237 nm. The R_f values found to be 0.23 ± 0.02 and 0.74 ± 0.02 for AML and LOS respectively. The method was validated in compliance with ICH Guideline for linearity, the limit of detection (LOD), the limit of quantification (LOQ), precision, specificity, accuracy, repeatability, and robustness.  Linear regression analysis data for the calibration plots showed good linear relationship over the concentration range of 100-400 ng/spot (r² = 0.9993) and 500-1750 ng/spot (r² = 0.9991) for AML and LOS respectively. The LOD and LOQ were 24.46 and 74.14 ng/spot for AML and 10.82 and 32.80 ng/spot for LOS. The recoveries of AML and LOS were found to be 99.48-99.56% and 99.51-99.89% respectively. The drugs were subjected to acidic, alkaline, oxidative, neutral and thermal degradation conditions. The degradation product of Losartan in acidic condition was carried out, and its degradation product is successfully separated and isolated by HPTLC method. Degradation product was identified by using the MS technique.