Single-step extraction followed by LC for determination of (fluoro)quinolone drug residues in muscle, eggs, and milk

In this study, a simplified method for the extraction and determination of seven fluoroquinolone residues (danofloxacin, difloxacin, enrofloxacin, marbofloxacin, orbifloxacin, ofloxacin, and sarafloxacin) and three quinolones (oxolinic acid, flumequine, and nalidixic acid), in porcine muscle, table eggs, and commercial whole milk, which required no cleanup step, was devised. This procedure involves the extraction of analytes from the samples via liquid-phase extraction, and the subsequent quantitative determination was accomplished via LC-fluorescence detection. Analyte separation was successfully conducted on an XBridge-C-18 column, with a linear gradient mobile phase composed of acetonitrile and 0.01 M oxalic acid buffer at pH = 3.5. The one-step liquid-liquid extraction method evidenced good selectivity, precision (RSDs = 0.26-15.07%), and recovery of the extractable analytes, ranging from 61.12 to 115.93% in matrices. The LOQs ranged from 0.3 to 25 mu g/kg. A survey of ten samples purchased from local markets was conducted, and none of the samples harbored fluoroquinolone residues. This method is an improvement over existing methodologies, since no additional cleanup was necessary.