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Simultaneous determination of twenty antibiotic residues including β-lactams,quinolones and macrolides in milk and powdered milk samples by ultra performance liquid chromatography

An ultra performance liquid chromatographic method for the simultaneous determination of 20 antibiotic including cephalosporins,quinolones and macrolides in milk and powdered milk samples was established.After precipitating protein with 0.5 mol/L perchloric acid,the samples of milk or powdered milk were extracted with acetonitrile and water(8+2).The extract was cleaned up with HLB cartridge and the chromatographic operating conditions were on a BEH C18 column(50 mm×2.1 mm i.d.,1.7μm),acetonitrile(containing 0.2% formic acid)-0.006 mol/L ammonium acetate as mobile phase at a flow rate of 0.4 mL/min.The LODs of milk and powdered milk samples were in the ranges of 8～60μg/kg and the LOQs were in the ranges of 25～200μg/kg at a S/N of 10.The intra-assay precisions were in the ranges of 2.3%～13% and spiked recoveries of ten antibiotics were 48.6%～91.2%.