An easy-to-use method for determining the levels of fipronil and its metabolites (fipronil-desulfinyl, fipronil-sulfone and fipronil-sulfide) in chicken egg, muscle and cake was developed and validated using a modified quick, easy, cheap, effective, rugged and safe (QuEChERS) approach coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. The samples were extracted using acetonitrile, salted out with sodium chloride at -20°C, and then purified by combined PSA and C18 phases and anhydrous magnesium sulphate. The recoveries were 80.4-119% with relative standard deviations (RSDs) < 10% for the different matrixes. The validated method was used to analyse the target compounds in 214 real samples collected in Beijing. The metabolite fipronil-sulfone was detected in most of the samples and was identified as the main residue in the egg and cake. The method was validated using a proficiency test for fipronil in products of animal origin published by Wageningen University & Research in 2017.
Keywords: Fipronil and its metabolites; cake; chicken egg; muscle; ultra-performance liquid chromatography-tandem mass spectrometry.