CONFIRMATION OF FLUOROQUINOLONES IN CATFISH MUSCLE BY ELECTROSPRAY LIQUID-CHROMATOGRAPHY MASS-SPECTROMETRY

A multiresidue liquid chromatography/mass spectrometry (LC/MS) confirm ation method for fluoroquinolones in catfish muscle was developed by u sing an electrospray interface. Residues of ciprofloxacin, enrofloxaci n, sarafloxacin, and difloxacin were positively identified in catfish muscle fortified at 10-80 ppb as well as in incurred tissue. The extra ction procedure is based on an LC method with fluorescence detection f or determination of these compounds in catfish. Residues were extracte d from catfish muscle with an acidic ethanol solution, and the extract s were cleaned up on a propyl sulfonic acid solid-phase extraction col umn. Chromatographic conditions were optimized to be compatible with t he electrospray interface, internal electrospray voltages were optimiz ed so that 3 fragment ions, in addition to the protonated molecular io n, could be monitored for each residue. To obtain maximum sensitivity, separate MS acquisition programs were developed for ciprofloxacin/enr ofloxacin and sarafloxacin/difloxacin pairs.