Stress degradation study of Etoricoxib, isolation, and characterization of major degradation impurity by preparative high‐performance liquid chromatography, liquid chromatography‐mass spectrometry, and nuclear magnetic resonance: Validation of ultra‐performance liquid chromatography method

Abstract Etoricoxib (ETO) is a selective cyclooxygenase‐2 inhibitor, used as a nonsteroidal anti‐inflammatory drug. In this study, a detailed investigation was conducted on the degradation behavior of ETO under acidic, basic, neutral, photolytic, oxidative, and thermal degradation conditions as per the International Conference on Harmonization (ICH) guideline Q1A (R2). A gradient “ultra‐performance liquid chromatography (UPLC)” method was developed for separating the degradation products formed under various degradation conditions along with process‐related impurities. Acquity BEH phenyl column was used for the separation of analytes and 0.1% formic acid in water and 0.05% formic acid in acetonitrile:methanol (8:2 %v/v) were used as mobile phase‐A and mobile phase‐B. A major degradant namely, N‐oxide impurity was observed in oxidative degradation along with two minor degradants where N‐oxide was confirmed based on LC‐mass spectrometry (LC‐MS) studies. Further, the major degradant was enriched and isolated using preparative HPLC and the conformation of the N‐oxide impurity was established using nuclear magnetic resonance techniques including two‐dimensional studies and high‐resolution MS. In addition, the method for related substances by UPLC has been validated by considering a major degradant, namely N‐oxide along with process‐related impurities as per the ICH guidelines validation parameters.