| Three analytical methods were established for the determination of fipronil and its metabolite residues in meat,eggs and visceral nitrile by gas chromatography-mass spectrometry(GC-MS) with electronic ionization(EI) or negative chemical ionization(NCI) and gas chromatography-triple quadrupole mass spectrometry(GC-MS/MS) with EI.And the three methods were compared.The samples were extracted with acetonitrile,and purified with PSA,C18 and GCB.The extracts were determined by GC-MS combined with EI or NCI techniques and GC-MS/MS with EI in multi-reaction monitoring(MRM) mode,and quantified by the external standard method.The calibration curves for fipronil and its metabolites were linear in the range of 0.001-2.0 mg/L with correlation coefficients(r2) higher than 0.999 0.The detection limits(LODs) of GC-MS/EI,GC-MS/NCI and GC-MS/MS/EI were 0.15,0.05,0.15 μg/kg with the limits of quantitation(LOQs) of 0.5,0.2,0.5 μg/kg，respectively.The sensitivity of GC-MS method with NCI is much higher than that with EI when analyzing fipronil and its metabolites with several strong electronegative elements in the molecule.The recoveries at three spiked concentration levels of 2,50,500 μg/kg ranged from 80.0%to 108.0% with relative standard deviations(RSDs) of 1.1%-7.6%.The three methods could complement each other,and be used in the detection and confirmation of fipronil and its metabolites in animal derived foods. |