Preparative isolation and structural elucidation of impurities in fluconazole by LC/MS/MS.

Three impurities were detected in the LC/MS analysis of fluconazole bulk drug substance. Two of the impurities were unknowns having not been reported previously. Structural assignment of these impurities was carried out by LC/MS/MS using electrospray ionization source and an ion trap mass analyzer. Structural elucidation using nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy was facilitated by newly developed rapid preparative isolation method. These impurities were characterized as 1-(1-H-1,2,4-triazole-1-yl) propane-2,3-diol and Z-2-(2,4-difluorophenyl)-3-(1-H-1,2,4-triazole-1-yl)-2-propen-1-ol. Their formation and synthesis are discussed.