Separation and characterization of unknown impurities in latamoxef sodium by LC-Q-TOF MS and a summary of their positive-ion fragmentation regularities

A simple and sensitive method was developed for separation and characterization of seventeen impurities from commercial latamoxef sodium for injection by liquid chromatography combined with electrospray ionization and QTOF mass spectrometer (LC-ESI-QTOF MS). The chromatographic separation was performed on a Boston Green ODS-AQ C18 column (250 mm × 4.6 mm, 5 μm) under gradient mode using binary mobile phase: (A) ammonium acetate (10 mM)-methanol (99:1, v/v) and (B) ammonium acetate (10 mM)-methanol (70:30, v/v). Based on tandem multistage MS and high resolution MS data, the molecular formulas and structures of unknown impurities were inferred. A plausible formation mechanism of impurities was also proposed. In addition, the fragmentation regularity of degraded impurities in positive-ion mode was summarized.