Analysis of protonated and alkali metal cationized aminoglycoside antibiotics by collision-activated dissociation and infrared multi-photon dissociation in the quadrupole ion trap

Nine aminoglycoside antibiotics were analyzed in two quadrupole ion trap ma ss spectrometers using electrospray ionization, Structural information was obtained via collision-activated dissociation (CAD) and infrared multiphoto n dissociation (IRMPD) of the protonated species, Several of the compounds, having multiple basic sites, preferred the doubly protonated form while so me existed in the singly charged state or were distributed between single a nd doubly protonated species, allowing comparison of the fragmentation patt erns of the two charge states. In general, IRMPD is as efficient as CAD, pr oduces more low-mass fragment ions, and is more universally applied owing t o its low dependence on trapping, pressure and tuning conditions, Alkali me tal complexation using Li+ and Na+ was probed as a means of producing diffe rent fragmentation patterns, but in most cases the resulting fragmentation patterns were simplified versions of those obtained for the protonated anal ogs, Copyright (C) 2000 John Wiley & Sons, Ltd.