Development and Validation of a Stability-Indicating RP-HPLC Method for Determination of Ambrisentan in Bulk Drugs

A stability-indicating reversed phase high-performance liquid chromatographic (RP-HPLC) method was developed for quantitative determination of ambrisentan and its potential related substances in bulk drugs. Drug substance was subjected to various stress conditions such as hydrolysis, oxidation, photolysis and thermal degradation as per International Conference on Harmonization (ICH) guidelines to investigate the stability indicating nature of the method. Significant degradation was found in acidic stress conditions. Efficient chromatographic separation was accomplished on a Phenomenex Luna C₁₈ (250 x 4.6 mm, 5 μm) column with a mobile phase composed of 0.02 M ammonium acetate buffer (pH = 4.2), and acetonitrile in 52:48 (v/ v) ratio at a flow rate of 1.0 mL/ min and column temperature of 25 degree Celsius. The eluent were monitored with a photo diode array (PDA) detector at a wavelength of 215 nm. The developed liquid chromatographic method was validated with respect to linearity, accuracy, precision, limits of detection and quantitation, and robustness. Regression analysis showed correlation co-efficient values greater than 0.997 for ambrisentan and its five impurities. Accuracy of the method was established based on the recovery obtained between 92.8 - 103.5 % and 99.2 - 100.7 % for impurities and ambrisentan, respectively. (author)