Simultaneous Determination of Residual Antibiotics in Livestock Manure by Solid Phase Extraction-Ultra-high Performance Liquid Chromatography Tantem Mass Spectrometry

Abstract

A ultra-high performance liquid chromatography tandem mass spectrometric(UPLC-MS/MS) method was developed for the simultaneous determination of various antibiotics residues including 6 sulfonamides(SAs),4 tetracyclines(TCs),3 quinolones(FQs),3 macrolides(MACs) and 1 nitrofuran(NFs) in livestock manures.The samples were extracted with McIlvaine-Na2EDTA buffer and organic mixed extract solution by ultrasonic extraction,and then degreased by n-hexane.The extract was cleaned upon a SAX-HLB solid phase column.After drying the extract under a gentle stream of N2 and reconstituting the dried residue,the target compounds were analyzed by ultra-high performance liquid chromatography with gradient elution using a cetonitrile-0.1% formic acid as mobile phase.The antibiotics were identified and determined by internal standard method.In the concentration range of 0.1-1000 μg/kg(dry weight),R2 of calibration curve for all the objects was above 0.99.The detected limits(LOD) ranged from 0.1 ng/g to 2.0 μg/kg,limit of quantification(LOQ) ranged from 0.3 to 6.6 μg/kg.The recoveries of target compounds at three spiked levels ranged from 42.3% to 79.6% with relative standard deviations of 1.4%-5.4%.The method was applied on the determination of residual antibiotics in 32 manure samples collected from several animal feeding operations in Northen China.The results indicated that all of the selected antibiotics were detected at different levels,in which the highest concentration was chlortetracycline with 125 mg/kg.