CLASS-SELECTIVE COLLISIONALLY ACTIVATED DISSOCIATION ION-MOLECULE REACTIONS OF 4-QUINOLONE ANTIBIOTICS

A new combination of collisionally activated dissociation and ion-mole cule reactions in a quadrupole ion trap mass spectrometer is developed for the class-selective determination of 4-quinolones, an important g roup of antibiotics. In this method, collisionally activated dissociat ion is used to promote dehydration of each protonated quinolone, and t he resulting dehydrated fragment ion undergoes an addition reaction wi th an auxiliary reagent. The auxiliary reagents, including acetone, ac etic anhydride, and n-propylamine, have structures that specifically a llow formation of a cyclic adduct with the analyte ion. This sequentia l process is characteristic of a class of analyte molecules that have adjacent carboxylic acid and ketone functional groups anchored on a ri gid ring and undergo facile, efficient dehydration.