Degradation Pathway for Eplerenone by Validated Stability Indicating UP-LC Method.

Degradation pathway for eplerenone is established as per ICH recommendations by validated and stability-indicating reverse phase liquid chromatographic method. Eplerenone is subjected to stress conditions of acid, base, oxidation, and thermal and photolysis. Significant degradation is observed in acid and base stress conditions. Four impurities are studied and the major degradant (RRT about 0.31) was identified by LC-MS and spectral analysis. The stress samples are assayed against a qualified reference standard and the mass balance is found close to 99.5%. Efficient chromatographic separation is achieved on a Waters symmetry C18 stationary phase with simple mobile phase combination delivered in gradient mode and quantification is carried at 240 nm at a flow rate of 1.0 mL min(-1). In the developed LC method the resolution between eplerenone and four potential impurities (imp-1, imp-2, imp-3, and imp-4) is found to be greater than 4.0. Regression analysis shows an r value (correlation coefficient) of greater than 0.999 for eplerenone and four potential impurities. This method is capable to detect the impurities of eplerenone at a level of 0.020% with respect to test concentration of 1.0 mg mL(-1) for a 20 μL injection volume. The developed UPLC method is validated with respect to specificity, linearity and range, accuracy, precision, and robustness for impurities and assay determination.