Determination of 9 cephalosporin drug residues in beef by ultra performance liquid chromatography-tandem mass spectrometry

A confirmative method to determine 9 cephalosporin residues in beef by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed. The sample was homogenized and extracted with acetonitrile and water for 1 min at 14 000 r/min, centrifuged at 10 000 r/min and 4 degrees C for 10 min. A total of 2 mL saturated sodium chloride solution was added to avoid foaming during the acetonitrile evaporation , the acetonitrile was evaporated below 37 degrees C using a rotary evaporator, and then cleaned up on an Oasis HLB (500 mg, 6 mL) SPE column by washing with 5 mL water and eluting with acetonitrile-water (7:3, v/v). The eluate was blown to dryness under a stream of nitrogen and adjusted to 3. 0 mL with water. The separation was carried out on an ACQUITY UPLC (TM) BEH C-18. column within 5 min, analyzed by UPLC-MS/MS system with external standard method. The limits of quantification ( LOQs) of cefuroxime ceftiofur and cefalonium were 10, 0. 5 and 0. 5 mu g/kg , respectively; the LOQs of other cephalosporins were 1. 0 mu g/kg. The recoveries of cephalosporins ranged from 74. 2% to 119% and the relative standard deviations (RSDs) ranged from 2. 9% to 15% for the spiked beef sample. The method is quick, easy, very sensitive and suitable for the determination of cephalosporin residues in beef.