A liquid chromatography (LC) method with luminescence detection for the determination of eightquinolone antibiotics is reported. The system encompasses three consecutive steps: (a) chromatographic separation using reverse-phase mode (RP-LC), (b) postcolumn derivatization reaction, and(c) luminescence detection by monitoring fluorescence (FL) and time-resolved (TR) signals. Thederivatization step is based on the reaction between quinolones and terbium(III) to form luminescentchelates, which were determined at
ex 340 and
em 545 nm (FL mode) or at
ex 281 and
em 545 nm(TR mode). Dynamic ranges of the calibration graphs, obtained with standard solutions of analytesand FL and TR modes, respectively, were 190-3500 and 316-2000 ng mL
-1 for marbofloxacin,8-3500 and 8.1-1500 ng mL
-1 for ciprofloxacin, 6.2-3500 and 13-1500 ng mL
-1 for danofloxacin,7.4-3500 and 8.4-1500 ng mL
-1 for enrofloxacin, 14-3500 and 20-2000 ng mL
-1 for sarafloxacin,12.5-3500 and 13.9-1200 ng mL
-1 for difloxacin, 7.6-3500 and 13-3000 ng mL
-1 for oxolinicacid, and 9-2000 and 130-3000 ng mL
-1 for flumequine. Limit of detection values obtained usingFL and TR modes, respectively, were 60 and 95 ng mL
-1 for marbofloxacin, 2 and 2.4 ng mL
-1 forciprofloxacin, 1.9 and 3.9 ng mL
-1 for danofloxacin, 2.2 and 2.5 ng mL
-1 for enrofloxacin, 3.8 and 7ng mL
-1 for sarafloxacin, 4 and 4.2 ng mL
-1 for difloxacin, 2.3 and 4 ng mL
-1 for oxolinic acid, and2.7 and 40 ng mL
-1 for flumequine. The precision was established at two concentration levels ofeach analyte and expressed as the percentage of relative standard deviation with values rangingbetween 1.9 and 7.8%. The validation procedure for the analysis of samples was carried out usingEuropean Community recommendations, and the decision limit and detection capability were calculatedfor bovine whole milk. The method was applied to whole, semiskimmed, and skimmed milk samplesspiked with the target analytes, and the recoveries ranged between 93.3 and 106.0%.
