Combination of Modified QuEChERS and Disposable Polyethylene Pipet Assisted DLLME Based on Low Density Solvent Extraction for Rapid and Sensitive Determination of Fipronil and Its Metabolites in Eggs by GC-MS

Abstract

In the present study, a new method for separation and enrichment of fipronil and its metabolites in eggs was proposed by combining a modified QuEChERS procedure with a disposable polyethylene pipet assisted DLLME (DPP-DLLME). The DPP-DLLME employed low density solvent as extractant and was conducted in a cheap, disposable polyethylene pipet with an open and narrow tip upside. After phase separation, the extractant was floating on the aqueous solution and concentrated in the narrow neck of the pipet, which can be directly withdrawn by a microsyringe for instrument analysis. By coupling with GC-MS detection, a new method for analysis of fipronil and its metabolites in eggs was established. The linearity range was 0.5–200 ng/g with correlation coefficient R2 higher than 0.9967. The recoveries in spiked egg samples were in the range of 89.3–103.8% with the RSDs less than 13.6% (intra-day) and 17.5% (inter-day). The limits of quantification for the four target analytes (fipronil desulfinyl, fipronil sulfide, fipronil, fipronil sulfone) in eggs were in the range of 0.2–0.3 ng/g, which was comparable or better to the previously reported methods. Finally, the established QuEChERS-DPP-DLLME method was successfully applied to detect fipronil and its metabolites in several egg samples with different brands from local market.