Abstract:A rapid screening method was developed for the determination of the residues of fipronil and its metabolites (fipronil-desulfinyl, fipronil sulfone and fiproil sulfide) in eggs by liquid chromatography triple quadrupole mass spectrometry (LC-MS/MS). Egg samples were extracted with acetonitrile and n-hexane. The obtained extract was purified by a C18 solid phase extraction (SPE) column and further separated using a Shim-pack XR-ODS Ⅲ column (2.0 mm I.D. × 150 mm L., 2.1 μm particle size) with a mobile phase in gradient elution (acetonitrile -5 mmol/L ammonium acetate (0.02% formic acid ). Qualitative screening and quantitative analysis were performed by LC-MS/MS with dynamic multiple reaction monitoring (DMRM) mode and in negative ion mode, and quantification was carried out by the external standard method. The results showed that good linearity was detected for fipronil and its metabolites in the range of 0~50 μg/L, with the correlation coefficient R2 greater than 0.999. The limit of quantification (LOQ) of fipronil and its metabolites was 0.3~0.6 μg/kg at the signal-to-noise ratio of 10. The average recovery of fipronil and its metabolites at the spiking levels of 0.5, 5.0 and 10.0 μg/kg ranged from 92.3% to 105.1%, with the relative standard deviation (RSD, n=6) in the range of 1.2%~8.6% The method was proven to be simple, rapid andsensitive, and suitable for rapid screening and quantitative detection of fipronil and metabolite residues in eggs.
