CHARACTERIZATION OF BETA-LACTAMS BY PHOTODISSOCIATION AND COLLISION-ACTIVATED DISSOCIATION IN A QUADRUPOLE ION-TRAP

Electrospray ionization was used to introduce beta-lactams, including cephalosporin and penicillin analogs, into a quadrupole ion trap for a nalysis by collision-activated dissociation (CAD) and infrared multiph oton dissociation (IRMPD). The two dissociation methods provided simil ar spectra; however, photodissociation requires substantially less tun ing than is typically required to optimize CAD. Moreover, IRMPD was ef fective even at the elevated pressures introduced by the electrospray source. Both CAD and IRMPD promote cleavage across the beta-lactam rin g, resulting in highly diagnostic fragmentation patterns. Time-resolve d and SWIFT methods were used to determine fragmentation genealogies o f the ions created by IRMPD. (C) 1998 John Wiley & Sons, Ltd.