Development and Validation of a Novel Stability Indicating UPLC Method for Analysis of Related Compounds and Assay of Bexarotene,an Anti-Cancer Agent

A novel liquid chromatographic method for the analysis of four potential impurities in the anti-cancer agent Bexarotene has been developed and validated using efficient chromatographic separation, achieved on a C₁₈ column (50 mm × 2.1 mm, 1.7-μm particles) with a simple isocratic mobile phase at a flow rate of 0.5 mL min^?1. The mobile phase consisted of a 70:30:0.1 (v/v/v) mixture of acetonitrile, water and trifluoroacetic acid, and quantification was achieved by use of ultraviolet detection at 260 nm. Resolution between Bexarotene and its four potential impurities was greater than 2.0. Regression analysis showed the r value (correlation coefficient) was >0.999 for Bexarotene and its four impurities. The method was capable of detecting all four impurities of Bexarotene at levels below 0.10 μg in a Bexarotene test concentration of 0.5 mg mL^?1 using an injection volume of 5 μL. The recovery for Bexarotene in assay method at a 100% level was observed to be 99.1 ± 0.32% with % RSD value of 0.5% for drug substance and 98.9 ± 0.46% for Bexarotene capsules with % RSD value of 0.4%. Recovery of imp-1, imp-2, imp-3, and imp-4 from bulk drug samples ranged from 96.3 to 102.0%. Recovery of imp-1, imp-2, imp-3, and imp-4 from Bexarotene Capsule samples ranged from 97.2 to 101.4%. A solution of Bexarotene in ethanol was stable for 48 h. The drug was also subjected to stress conditions as prescribed by ICH Guidelines. Degradation was found to occur under acidic and basic hydrolysis stress conditions; however, the drug was stable to oxidative, photolytic, and thermal stress. Assay of the stressed samples was calculated relative to a qualified reference standard and the mass balance was found to be close to 99.8%. The method was validated for linearity, accuracy, precision, and robustness.