Stability‐Indicating HPLC Method Development and Validation for the Quantification of Tofacitinib Citrate and Its Related Substances Using Hydrophilic Liquid Interaction Chromatography

A new stability‐indicating RPHPLC method with short run time has been developed and validated for tofacitinib citrate and its related substances. The novel HPLC method integrates hydrophilic interaction liquid chromatography (HILIC) technology as the stationary phase and employs a mobile phase composed of phosphate buffer (pH 7.0) and acetonitrile (45:55, %v/v) at a flow rate of 0.5 mL/min under isocratic elution. Analytes were monitored via a UV detector at 210 nm and with the column oven temperature at 30°C for a 20‐min analysis. Precision (%RSD) for Impurity‐A and Impurity‐B and tofacitinib met specifications at 2.4%, 0.8%, and 0.0%, respectively. Accuracy ranged from 86% to 100% for impurities, with LOD at 0.03% and LOQ at 0.05%–0.06%. Correlation coefficients exceeded 0.999 for impurities and tofacitinib citrate. Solution stability was confirmed for 24 h at room temperature. The method range was extended from LOQ to ∼1.5% for impurities and LOQ to ∼150% for tofacitinib citrate. The method's stability was evaluated under acid and base hydrolysis, oxidative and water hydrolysis, and thermal and photolytic degradation. Introducing HILIC as the stationary phase for this work proved effective, eliminating the need of ion pair reagents, reducing analysis time, and ensuring consistent results.