A high performance liquid chromatographic (HPLC) method was developed for the simultaneous determination of nalidixic acid,
flumequine, oxolinic acid, piromidic acid, danofloxacin, enrofloxacin and sarafloxacin in chicken, pork and fish. These seven
quinolone antibacterials were extracted with 0.3% metaphosphoric acid: acetonitrile (1:10, v/v), followed by a Bond Elut C18 cartridge
clean up procedure. The HPLC separation was achieved on a Cosmosil 5C18-AR-II column (5 µm, 4.6 mm i.d. ¥ 250 mm) with acetonitrile:
0.05M NaH2PO4 (pH 2.5)(35:65, v/v) containing 3.5 mM sodium dodecyl sulfate as a mobile phase, and detection was
performed with photodiode array and fluorescence detector (by using wavelength programming). Good linearity was observed from the
calibration plot at concentrations from 0.05 to 10.0 mg/mL (0.005~2.0 µg/mL for danofloxacin). Recovery studies of the analytes were
performed at 0.01, 0.1, 0.4 and 2.0 ppm (0.001, 0.01, 0.04 and 0.20 ppm for danofloxacin) spiked levels. Average recoveries of low
concentration ranged from 74.3 to 85.5% and those of the rest ranged from 80.1 to 99.9% with coefficients of variation less than 5.8%.
The detection limits of quinolones were 0.01~0.04 ppm with photodiode array detection and 0.0006~0.05 ppm with fluorescence
detection. The coefficients of variation of intra-day and inter-day assays were lower than 3.29% and 5.23%, respectively. These results
indicated that the developed method had an acceptable precision. Using this method to detect quinolones in sixty three samples
purchased from various markets in Taipei, we found that nine wu ku chicken muscles contained enrofloxacin residues ranged from 0.08
to 4.04 ppm, four wu ku chicken liver muscles contained enrofloxacin residues ranged from 0.01 to 0.27 ppm, and oxolinic acid
residues in three sweet fish samples ranged from 0.13 to 0.35 ppm. The results indicated that 25.4% of samples violated the regulation
set by the Department of Health. The enrofloxacin residue in wu ku chicken muscle is very stable even after a long period of refrigeration
at 4ûC.