Forced Degradation Study to Develop and Validate Stability-Indicating RP-LC for Quantification of Ropinirole Hydrochloride in Its Modified Release Tablets

Abstract

A forced degradation study on ropinirole hydrochloride in bulk and in its modified release tablets was conducted under the conditions of hydrolysis, oxidation and photolysis in order to develop an isocratic stability-indicating LC-UV method for quantification of the drug in tablets. An impurity peak in standard solution was found to increase under acidic and neutral hydrolytic conditions while another degradation product was formed under alkaline condition. The drug and its degradation products were optimally resolved on a Hypersil C₁₈ column with mobile phase composed of diammonium hydrogen orthophosphate (0.05 M; pH 7.2), tetrahydrofuran and methanol (80:15:5% v/v) at a flow rate of 1.0 mL min⁻¹ at 30 °C using 250 nm as detection wavelength. The method was linear in the range of 0.05–50 μg mL⁻¹ drug concentrations. The %RSD of inter- and intra-day precision studies was <1. The system suitability parameters remained unaffected during quantification of the drug on three different LC systems. Excellent recoveries (101.59–102.28%) proved that the method was sufficiently accurate. The LOD and LOQ were found to be 0.012 and 0.040 μg mL⁻¹, respectively. Degradation behaviour of the drug in both bulk and tablets was similar. The drug was very unstable to hydrolytic conditions but stable to oxidative and photolytic conditions. The method can be used for rapid and accurate quantification of ropinirole hydrochloride in tablets during stability testing. Based on chemical reactivity of ropinirole in different media, the degradation products were suspected to be different from the known impurities of the drug.