Evaluating polymer monolith in-tube solid-phase microextraction coupled to liquid chromatography/quadrupole time-of-flight mass spectrometry for reliable quantification and confirmation of quinolone antibacterials in edible animal food

A simple, rapid, and sensitive method is presented to determine seven trace quinolone antibacterials simultaneously in milk, egg, chicken and fish. This method is based on the combination of polymer monolith in-tube solid-phase microextraction with liquid chromatography and electrospray ionization quadrupole time-of-flight mass spectrometry (LC/ESI-QTOF-MS). LC/ESI-QTOF-MS offers the capability of unequivocal identification of target compounds from complex matrices, as well as the possibility of quantitation at low-level concentrations in real samples. The extraction was performed with a poly(methacrylic acid-ethylene glycol dimethacrylate) monolithic column. Under the optimized extraction conditions, good extraction efficiencies for the targets were obtained with no matrix interference in the subsequent LC/ESI-QTOF-MS. Good linearities were obtained for seven quinolones with the correlation coefficients (R) above 0.9951. The limits of detection (S/N = 3) for seven quinolones were found to be 0.3–1.2 ng/g in egg, 0.2–3.0 ng/mL in milk, 0.2–0.7 ng/g in chicken and 0.2–1.0 ng/g in fish. The recoveries of quinolones spiked in four different matrices ranged from 80.2 to 115.0%, with relative standard deviations less than 14.5%. The developed method was applied for the determination of quinolone residues in animal-producing food, and the positive samples were confirmed with high number of identification points (IPs) according to the IP system defined by the European Union (Commission Decision 2002/657/EC).