Use of ion-trap liquid chromatography–mass spectrometry to screen and confirm drug residues in aquacultured products Original Research Article

Ion-trap liquid chromatography–multiple mass spectrometry (LC–MSn) has been shown to be a valuable tool for the confirmation of animal drug residues. We have taken advantage of this to update several regulatory methods for the confirmation of drug residues in aquacultured products. Here we report two such examples. First, the use of an ion-trap electrospray instrument collecting data-dependent MS2 and MS3 scans to yield structurally significant ions has allowed multi-residue confirmation of fluoroquinolones in salmon tissue. Ciprofloxacin, enrofloxacin, sarafloxacin, and difloxacin residues were positively identified in salmon muscle fortified at 5–80 μg kg−1. These residues were also confirmed in extracts from incurred salmon tissue with final drug concentrations ranging from 10 to 40 μg kg−1. The second example deals with multi-residue confirmation of phenicols using ion-trap LC–MSn. Comparisons of these methods with related confirmation procedures are discussed, as well as the optimization of MSn parameters to meet confirmation criteria. Initial efforts to use this instrument in conjunction with generic extraction methods to screen multi-class residues in shrimp tissue are also presented.