A Validated Rapid Stability-Indicating Method for the Determination of Related Substances in Vardenafil Hydrochloride by Ultra-Performance Liquid Chromatography

Abstract

A novel, sensitive, stability indicating RP-LC method has been developed for the quantitative determination of Varde- nafil and its related impurities in both bulk drugs and Pharmaceutical dosage forms. Effective chromatographic separation was achieved on a C18 stationary phase with simple mobile phase combination delivered in a simple gradient pro- gramme and quantitation was by ultraviolet detection at 210 nm. The mobile phase consisted of a buffer and acetonitrile delivered at a flow rate 0.25 ml?min–1. Buffer consisted of 20 mM Ammonium bi carbonate, pH adjusted to 5.0 by using ortho Phosphoric acid. In the developed UPLC method the resolution (Rs) between vardenafil and its four potential impurities was found to be grater than 2.0.Regrreation analysis showed an r value (correlation coefficient) grater than 0.999 for vardenafil and its four impurities. This method was capable to detect all four impurities of vardenafil at a level of 0.25 μg.mL–1 with respect to test concentration of 500 μg?ml–1 for a 2 μl injection volume. The inter and intra day precision values for all four impurities and for vardenafil was found to be with in 2.0% RSD. The method showed good and consistent recoveries for vardenafil in bulk drugs (98.8% - 100.9%), pharmaceutical dosage forms (100.5% - 101.5%) and its all four impurities (99.8% - 102.5%).The test solutions was found to stable in acetonitrile for 48 h. The drug was subjected to stress conditions of hydrolysis, oxidation, photolysis, and thermal degradation. Considerable degradation was found to occur in peroxide hydrolysis. The stress samples were assayed against a qualified reference standard and the mass balance was found close to 99.9%. The developed RP-LC method was validated with respect to linearity, accuracy, precision and robustness.