FRAGMENTATIONS OF FLURBIPROFEN-L-ARGININE DIASTEREOMERS IN NEGATIVE-ION FAST-ATOM-BOMBARDMENT MASS-SPECTROMETRY

Fragmentations between flurbiprofen-L-arginine diastereomers, flurbiprofen(S)-L-arginine and flurbiprofen (R)-L-arginine, were examined in both fast atom bombardment (FAB) and field desorption mass spectrometry. In negative ion FAB mass spectrometry using glycerol as a matrix, the cleavage pattern for flurbiprofen(S)-L-arginine was very different from that for flurbiprofen(R)-L-arginine, and the former changed depending on the amount of xenon collisional energy. In positive ion FAB and field desorption mass spectrometry, no significant differences were found between the cleavage patterns of these two diastereomers, Our results indicate that the selection of the mode of ionization, the matrix and the FAB gun voltage were important in order to distinguish accurately between flurbiprofen-L-arginine diastereomers.