Study of impurity carryover and impurity profile in Febuxostat drug substance by LC–MS/MS technique

Febuxostat is used in the treatment of hyperuricemia and gout. Several impurities were detected in Febuxostat drug substance. Impurities were identified with the help of LC–MS/MS and were characterized after synthesis by IR and NMR. Reverse phase gradient system was used with Kromasil C18, 150 mm × 4.6 mm, 5 μm particle size column for the separation of impurities. Q-TOF mass spectrometer with electrospray ionization (ESI) source was used and operated in ESI positive mode, which gives exact mass up to four decimal places and fragmentation with mass accuracy, it is useful for the identification of impurities. Four impurities were identified as amide, sec-butyl, des-cyano and des-acid in Febuxostat drug analog. These impurities were further confirmed by NMR and FT-IR spectral data.