| A high performance liquid chromatography-tandem mass spectrometry(HPLC-MS/MS) was developed for the simultaneous determination of seven macrolide antibiotics,ie.tilmicosin,roxithromycin,spiramycin,tylosin,erythromycin,clarithromycin and azithromycin in additive premix,concentrate supplement,complete feed and concentrated feed.The samples were extracted with 1% ammoniated acetonitrile solution,followed by Oasis PRiME HLB solid phase extraction for further purification.The analytes were separated on an ACQUITY UPLC BEH C18 column(2.1 mm×100 mm,1.7 μm) by gradient elution using 0.1% formic acid solution and acetonitrile as mobile phases,then analyzd by MS/MS with electrospray ionization in positive mode,and quantified by external standard method.Results showed that there were good linear relationships for 3 target analytes,ie.tilmicosin,spiramycin and erythromycin in the concentration range of 0.5-50 μg/L(r2>0.99) and for the other 4 target analytes in the range of 0.25-50 μg/L(r2>0.99).The limits of detection and the limits of quantitation were in the ranges of 1.25-2.5 μg/kg and 2.5-5.0 μg/kg,respectively.At three spiked levels of 5,10 and 50 μg/kg,the average recoveries for target compounds ranged from 61.4% to 103% with relative standard deviations of 0.43%-15%.The developed method is simple,rapid,sensitive and low matrix interference,and it is suitable for the routine supervision and quantitative detection of macrolide antibiotics in different feeds. |