Kinetics investigation and determination of pipoxolan hydrochloride and its degradant using liquid chromatography

An LC method was developed for the quantitative determination of pipoxolan hydrochloride (PPH) and its degradant. Forced degradation studies were performed on bulk sample using acid (1 M hydrochloric acid), alkaline (0.2 M sodium hydroxide), oxidation (0.33% hydrogen peroxide), heat (70 degrees C), and photolytic degradation. The chromatographic method was fine-tuned using the samples generated from forced degradation studies. Good resolution between the peaks corresponding to the degradants and the analyte was achieved on a Discovery C18 LC column (25 cm x 4.6 mm id, 5 pm particle size). The mobile phase was methanol-10 mM sodium dihydrogen phosphate (60+40, v/v); pH was adjusted to 6.5 using 0.2 M sodium hydroxide. Quantitation was achieved with UV detection at 214 nm based on peak area. The proposed LC method was used to investigate the kinetics of acidic and alkaline degradation processes of PPH at different temperatures, and the apparent pseudo-first-order rate constant, half-life, and activation energy were calculated. The pH-rate profiles of degradation of PPH in Britton-Robinson buffer solutions within the pH range 2-12 were studied. The developed method was validated with respect to linearity, accuracy, precision, and robustness. Forced degradation studies proved the stability-indicating power of the method.