A Stability Indicating UPLC Method for Finasteride and Its Related Impurities

The objective of the present research work is to develop a gradient, reversed-phase liquid chromatographic (RP-UPLC) method for the determination of Finasteride in pharmaceutical bulk drugs for assay and its related impurities. The chromatographic separation was achieved on a Waters ACQUITY UPLC BEH Phenyl Column (150 mm × 2.1 mm, 1.7 μm), The gradient LC method employs solutions A and B as mobile phase. The solution A Contains 2.5 mM ortho phosphoric acid (Buffer) and solution B contains a mixture of acetonitrile and water in the ratio of (90:10 v/v). The flow rate was 0.22 ml/min and the detection wavelength was 210 nm. In the developed UPLC method, the resolution between Finasteride and its potential impurities, namely Imp-1, Imp-2, Imp-3 and Imp-4 was found to be greater than 2.0. The drug was subjected to stress conditions of hydrolysis, oxidation, photolysis and thermal degradation. Considerable degradation was found to occur in alkaline medium and oxidative stress conditions. Degradation product formed during oxidative hydrolysis was found to be Imp-1. The stress samples were assayed against a qualified reference standard and the mass balance was found close to 99.5%. The developed RP-UPLC method was validated with respect to linearity, accuracy, precision and robustness. The limit of quantification of Imp-1, Imp-2, Imp-3 and Imp-4 were 0.06, 0.06, 0.05 and 0.036% (of analyte concentration, i.e. 0.5 mg/ml) with 1 μl injection volume. The developed method was found to be linear in the range of 2.5 15 μg/mL with correlation coefficient of 0.999 for assay procedures and found to be linear in the range of 0.05 3 μg/mL with correlation coefficient of 0.999 for related impurities.