| A method was developed for the simultaneous determination of eight fat soluble colorants(para red,sudan Ⅰ,Ⅱ,Ⅲ,Ⅳ,sudan red 7B,sudan red G and sudan yellow) in feed by liquid chromatography-tandem mass spectrometry(LC-MS/MS) combined with dispersive solid phase extraction.The samples were extracted with acetonitrile.Then the extract was purified by dispersive solid phase extraction method with N propylethylenediamine(PSA) sorbent.After purification,the extract was diluted with 0.2% formic acid solution.Before analysis by LC-MS/MS,the samples were separated on an Acquity BEH C18 column with a mixture of 0.2% formic acid solution and acetonitrile as mobile phase under gradient elution conditions.The mass spectrometer was operated under multiple reaction monitoring(MRM) mode in the positive mode.The samples were quantified by the isotope dilution and the internal standard method.Good linearities were obtained for the eight fat soluble colorants in the concentration range of 1.0-200 μg/L with correlation coefficients more than 0.998.The recoveries of the analytes at fortified levels of 10-500 μg/kg were in the range of 102%-111%.The limits of detection and the limit of quantitation for eight fat soluble colorants were 5.0 μg/kg and 10 μg/kg,respectively.The relative standard deviations of intra-assay were between 2.8% and 8.0%.The relative standard deviations of inter assay were between 2.8% and 7.8%.The method is suitable for the determination of eight fat soluble colorants in feed. |