Identification, isolation, characterization, and UHPLC quantification of potential genotoxic impurities in linagliptin.

During the stress testing of linagliptin, one unknown degradation product (impurity I) on acidic conditions was detected by using high-performance liquid chromatography and subsequently isolated, identified, and characterized by the spectral data (MS, MS/MS, 1D and 2D NMR spectroscopy, and IR spectroscopy) and finally subjected for mechanism analysis. The degradation product (impurity I) and another process-related impurity (impurity II) of linagliptin were found to contain the structural alerts of N-acylated aminoaryl and alkyl halide, respectively, which were both potential genotoxic substances. Hence, a rapid and facile ultra high performance liquid chromatography method was developed for the simultaneous determination of these two potential genotoxic impurities at ppm levels in linagliptin. The factors involved in the method development were discussed and this method was fully validated as per International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use guidelines, which proved the method sensitive, selective, and robust. The presented method has been successfully applied to the analysis of real samples from multiple batches. This study will help to risk management of possible genotoxic impurities present in linagliptin.