Abstract: The structural fragmentation of three cephalosporins in electrospray ionization conditions was studied by electrospray ionization quadrupole time-of-flight mass spectrometry in positive mode. Some common fragmentation pathways were found to be closely related to the substituent of the 7-aminocephalosporin nucle us. The product ion experiments turned out to be an essential technique to draw the fragmentation patterns of compounds. The results suggest that electrospray ionization quadrupole time-of-flight mass spectrometry is an ideal instrument to investigate the fragmentation pathways of drugs.

Key words: cephalosporins, electrospray ionization quadrupole time-of-flight ma ss spectrometry, collision-induced dissociation