Tandem infrared multiphoton dissociation and collisionally activated dissociation techniques in a quadrupole ion trap

Tandem infrared multiphoton dissociation and collisionally activated dissoc iation methods are implemented in a quadrupole ion trap mass spectrometer a nd used to characterize lan array of antibiotic ions generated by electrosp ray ionization. The tandem methods prove useful for probing fragmentation g enealogies, evaluating the structures of lower mass fragment ions produced from higher mass molecular ions, and differentiating isobaric ions. The inf rared multiphoton dissociation method is more efficient for producing array of fragment ions over a large mass range, whereas collisionally activated dissociation is preferable for the analysis of lower m/z ions.