Determination of fipronil and its metabolites in chicken egg, muscle and cake by a modified QuEChERS method coupled with LC-MS/MS

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 sulfate. The recoveries were 80.4–119% with relative standard deviations (RSDs) < 10% for the different matrixes. The validated method was used to analyze 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.

本研究建立并验证了一种便捷易用的检测方法，可用于测定鸡蛋、肌肉及蛋糕样品中氟虫腈（fipronil）及其代谢物脱亚磺酰基氟虫腈（fipronil-desulfinyl）、氟虫腈砜（fipronil-sulfone）与氟虫腈硫醚（fipronil-sulfide）的残留水平。该方法采用经改良的快速、简便、廉价、高效、耐用、安全（QuEChERS）前处理手段，结合液相色谱-串联质谱（LC-MS/MS）分析完成。样品以乙腈提取，经氯化钠盐析并置于-20℃环境下，随后通过混合氨基丙基硅烷（PSA）、十八烷基硅烷（C18）吸附剂与无水硫酸镁进行净化。不同基质下的加标回收率为80.4%~119%，相对标准偏差（RSDs）均小于10%。采用该经验证的方法对北京地区采集的214份实际样品中的目标化合物进行分析，结果显示大部分样品中均检出氟虫腈砜，且该代谢物被确定为鸡蛋与蛋糕样品中的主要残留成分。本方法通过了瓦赫宁根大学与研究中心（Wageningen University & Research）2017年发布的动物源产品中氟虫腈能力验证计划的验证。