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A stability indicating LC method for riluzole in bulk drugs and pharmaceutical dosage forms

Ravi Kiran Kaja, K.V.Surendranath, P.Radhakrishnanand, J.Satish1, P.V.V Satyanarayana

A novel, sensitive, stability indicating RP-LC method has been developed for the quantitative determination of riluzole, its related impurities in both bulk drugs and pharmaceutical dosage forms. Efficient chromatographic separation was achieved on a C18 stationary phase with simple mobile phase combination delivered in an isocratic mode and quantitation was carried out using ultraviolet detection at 241 nm. The mobile phase consists of buffer and acetonitrile. Buffer consists of 10 mM ammonium acetate, pH adjusted to 8.5 by using triethylamine and delivered at a flow rate of 1.2 mL min-1. In the developed HPLC method the resolution (Rs) between Riluzole and its three potential impurities was found to be greater than 2.0. Regression analysis shows an r value (correlation coefficient) of greater than 0.999 for Riluzole and it’s all the three impurities. This method was capable to detect all three impurities of Riluzole at a level of 0.0003% with respect to test concentration of 1.0 mg mL-1 for a 20L injection volume. The inter and intra day precision values for all three impurities and for Riluzole was found to be within 2.0% RSD. The method has shown good and consistent recoveries for Riluzole in bulk drugs (98.3-101.1%), pharmaceutical dosage forms (101.0-103.1%) and it’s all the three impurities (99.7-101.7%). The test solution was found to be stable in diluent for 48 h. The drug was subjected to stress conditions of hydrolysis, oxidation, photolysis and thermal degradation. Considerable degradation was found to occur in oxidative conditions. The stress samples were assayed against a qualified reference standard and the mass balance was found close to 99.95%. The developed RP-LC method was validated with respect to linearity, accuracy, precision and robustness.