Determination of Fipronil and Its Metabolite Residues in Eggs and Egg Products by GC-MS/MS

Fipronil and its metabolite residues (fipronil-desulfinyl, fipronil sulfide and fipronil sulfone) in eggs and egg products were detected by gas chromatography-tandem mass spectrometry (GC-MS/MS). The samples were diluted by water, and vortexed to mix uniformity. Then acetonitrile containing 0.1% acetic acid was added, followed by sodium chloride. After vortexing and shaking vigorously, the samples were ultrasonic extracted. Then the samples were centrifuged, and the supernatant layer was taken. Then residues were extracted by acetonitrile containing 0.1% acetic acid again. The supernatant layer of twice extraction was put together and evaporated to dryness. Then acetonitrile was added to dissolve the residue. This solution was cleaned up by dispersive solid phase extraction powder (primary secondary amine, graphitized carbon black and eighteen alkyl silane), then was analyzed by GC-MS/MS. The extraction solvent (ethyl acetate, acetone, acetonitrile and acetonitrile containing 0.1% glacial acetic acid) and extraction mode (shaking, vortexing ultrasonic and oscillation) were optimized. The optimization of dispersive-solid phase extraction powders was carried out by orthogonal experiment. The matrix effects of four compounds in eggs and egg products were definitely declined by the purification of dispersive-solid phase extraction. The quantification was carried out by external standard method of matrix calibration curve. The linear ranges of four compounds are 2-100 μg/L with the correlation coefficients more than 0.99. The limits of quantification of four compounds are 1.0 μg/kg. At four spiked concentration levels of 1.0, 2.0, 4.0 and 20.0 μg/kg, the recoveries are 72.0%-109.5% with the relative standard deviations (RSDs) less than 16.0%. This method is accurate, simple, quick, and suitable for simultaneous determination of fipronil and its metabolite residues in eggs and egg products.