Multi-residue Analysis of Fipronil and its Metabolites in Eggs by SinChERS-based UHPLC-MS/MS

A method for simultaneous detection of fipronil (F) and its metabolites fipronil desulfinyl (FD), fipronil sulfide (FS), fipronil sulfone (FSO) in chicken eggs was applied and validated. It includes SinChERS for sample preparation and UHPLC-MS/MS for chemical analysis. Results suggested that formic acid enhanced the recovery of 4 target residues and 1% supplement to acetonitrile gained higher recoveries than 5% formic acid acetonitrile. SinChERS integrates extraction and clean-up steps into one, with shorter time (1.5 h) to operate and higherrecoveries (97%~100%) than HLB, Envi-Carb-NH₂ and QuEChERS, and it consumes the smallest volume of extracting solvent (10 mL) as QuEChERS. Quantitative analyses using external standard method showed the linear ranges of 4 target compounds are 1~20 µg/L with R²>0.9947. The limit of detection (S/N>3) and quantification (S/N>10) was 0.3 μg/kg and 1 μg/kg. Recoveries were from 89.0% to 104.4%, and the relative standard deviations (n=6) at 1, 10, 20 μg/kg were lower than 6.03%. To verify the adaptability and practicality of the established SinChERS-based UHPLC-MS/MS, 30 batches of domestic eggs (500 g each batch) were checked and no target residues were detected in all samples. Therefore, the method developed in this study is a rapid, sensitive, accurate and economic way for multi-residue analysis of fipronil and its metabolites in eggs.