| A confirmatory method was developed and validated for the simultaneous determination of four acetylgestagens residues,including flurogestone acetate(FGA),melengestrol acetate(MGA）,megestrol acetate(MA) and chlormadinone acetate(CMA)in ovine milk using high performance liquid chromatography-tandem mass spectrometric(HPLC-MS/MS） method.The analytes were extracted from milk with acetonitrile,defatted with freezing-lipid filtration,and then the extract was purified with C18 solid-phase extraction column.The analytes were analyzed by HPLC-MS/MS in positive multiple reaction monitoring(MRM）mode. Two product ions from each of the chosen precursor ions were acquired for confirmation of the acetylgestagens.Good linearities were achieved with correlation coefficients not less than 0.999 6 for all analytes in the concentration of 0.5-20 μg/L.The limits of detection were 0.2,0.2,0.1,0.1 μg/kg for FGA,CMA,MGA,MA,respectively,with limits of quantitation of 0.5 μg/kg.Recoveries for the ovine milk fortified at levels of 0.5,1.0,2.0,10 μg/kg were in the range of 87%-96%,with RSDs of 4.5%-9.1%.The developed method is sensitive and accurate,and is suitable for the simultaneous detection of these acetylgestagens in ovine milk. |