Stability Indicating High Performance Liquid Chromatographic Method for Linagliptin and Mechanistic Identification of its Degradants using LC-MS

A selective, precise and reproducible reverse phase-High Performance Liquid Chromatographic method was developed and validated for Linagliptin drug substance. Using this method separation of eight potential process related impurities, comprising 3 isomeric compounds of linagliptin (concentration range of 0.25- 0.75 µg/ mL) and its impurities was achieved. The chemical stability of linagliptin was determined by forced degradation under thermal, acidic, oxidative, basic and hydrolytic conditions and subsequently eight degradants were assigned a structure by LCMS/MS. Linagliptin degraded significantly under oxidation because of the formation of four types of N-oxides in considerable amount as compared to Linagliptin. In this study the mechanistic pathway of all degradation routes have been elaborated. The findings of this study may assist in formulation development.