Stability-Indicating Methods for the Determination of Candesartan Cilexetil in Bulk Drug and Pharmaceutical Formulations

Two stability-indicating methods were developed for the determination of candesartan cilexetil in the presence of its degradation products. The first method uses isocratic RP-HPLC with an Agilent C18 column. The mobile phase was phosphate buffer (pH = 2.8 +/- 0.1)-acetonitrile (60 + 40, v/v). The flow rate was 2.0 mL/min, and the UV detection was at 254 nm. The second method depends on TLC-densitometric measurements of drug spots at 254 nm. The separation was carried out on silica gel 60 F-254 plates using ethyl acetate-methanol-toluene-ammonia 33% (40 + 25 + 20 + 2, v/v/v/v) mobile phase. The methods were validated according to U.S. Pharmacopeia guidelines, and the acceptance criteria for accuracy, precision, linearity, specificity, robustness, LOD, LOQ, and system suitability were met in all cases. Linear ranges of the methods were 10.0-200.0 mu g/mL and 1.0-9.0 mu g/spot for HPLC and TLC, respectively. The proposed methods were successfully applied to the drug in bulk powder, in laboratory-prepared mixtures with its degradation products, and in commercially available tablets. The results were compared statistically at the 95% confidence level with each other. There were no significant differences between the mean recovery and precision of the two methods.