Determination of five quinolone antibiotic residues in foods by micellar electrokinetic capillary chromatography with quantum dot indirect laser-induced fluorescence

A new assay was developed for the determination of five quinolone antibiotic residues in foods, loxacin, enrofloxacin, ciprofloxacin, lomefloxacin, and norfloxacin, by micellar electrokinetic capillary chromatography with indirect laser-induced fluorescence, in which cadmium telluride quantum dots were used as a fluorescent background substance. Some factors that affected the peak height and the resolution were examined. The optimized running buffer was composed of 20 mM SDS, 7.2 mg/L quantum dots, and 10 mM borate at pH 8.8. The separation voltage was 20 kV. Under these conditions, five quinolone antibiotic residues were separated successfully within 8 min. The detection limits ranged from 0.003 to 0.008 mg/kg; the linear dynamic ranges were all 0.01?～?10 mg/kg; and the average recoveries of the spiked samples were 81.4?～?94.6 %. The assay can meet the requirement of maximum residue limits to these five quinolone antibiotics in the regulations of the European Union and Japan and has been applied for determining their residues in animal-derived food.