The residues of fipronil and its metabolites, namely fipronil-desulfinyl, fipronil-sulfone, and fipronil-sulfide, have attracted increasing attention since the European egg contamination incident. In this study, by optimizing the pretreatment method and chromatographic conditions, a simple extraction method coupled with high performance liquid chromatography-tandem mass spectrometry was developed for the simultaneous determination of fipronil and its metabolites, including fipronil-desulfinyl, fipronil-sulfone, and fipronil-sulfide, in livestock and poultry liver. The optimal pretreatment method for fipronil and its metabolites was determined by comparing the recoveries obtained with different extraction solvents (methanol, acetonitrile, acetone, and ethyl acetate), and by purification with N-propyl ethylenediamine (PSA) and octadecylsilane (C18). The samples were extracted with 10 mL acetonitrile, then purified with 150 mg PSA and 100 mg C18, following which the extracted solutions were directly injected for analysis. Separation was performed on an Agilent ZORBAX SB-C18 column (150 mm×2.1 mm, 3.5 μm) with gradient elution using acetonitrile and water as the mobile phases. The target compounds were detected by electrospray ionization (ESI) in the negative mode under multiple reaction monitoring, and quantified by the external standard method with matrix-matched standard correction curves. The results indicated that the linear ranges for the four compounds ranged from 0.1 μg/L to 10.0 μg/L with correlation coefficients (r2) higher than 0.995. The limit of detection was 0.2 μg/kg and limit of quantitation was 0.5 μg/kg. The average recoveries were between 81.1% and 99.8% at three spiked levels of 0.5, 1.0, and 10 μg/kg, with relative standard deviations (RSDs) of 6.1%-11.7%. The matrix effect experiment showed that fipronil and its metabolites had matrix inhibition effects. Matrix-matched standard curve correction was performed to eliminate matrix inhibition effects. The proposed method was used for the analysis of 99 liver samples, where fipronil-sulfone was detected in four samples with values of 1.25-2.82 μg/kg. The method is simple, sensitive, and accurate, and is suitable for the determination of fipronil and its metabolites in livestock and poultry liver.
欧洲鸡蛋污染事件爆发后,氟虫腈及其代谢物氟甲腈、氟虫腈砜和氟虫腈亚砜残留受到人们较多关注。该研究通过优化前处理方法和色谱条件,建立了畜禽肝脏中氟虫腈及其代谢物的高效液相色谱-串联质谱测定分析方法。样品经10 mL乙腈提取,150 mg PSA、100 mg C18填料净化后,将提取液直接进样分析,以乙腈和水为流动相进行梯度洗脱,在Agilent ZORBAX SB-C18色谱柱(150 mm×2.1 mm, 3.5 μm)上进行色谱分离,采用电喷雾离子源,负离子扫描,多反应监测(MRM)模式测定,基质校正曲线,外标法定量。结果表明,氟虫腈及其代谢物在0.1~10 μg/L范围内线性关系良好,相关系数(r2)均大于0.995,方法的检出限和定量限分别为0.2 μg/kg和0.5 μg/kg。在0.5、1.0、10.0 μg/kg 3个加标水平下,氟虫腈及其代谢物的平均回收率为81.1%~99.8%,相对标准偏差(RSD)为6.1%~11.7%。应用建立的方法对99份畜禽肝脏样品进行检测,在4份样品中检测出氟虫腈砜,测定值为1.25~2.82 μg/kg。该方法简单,灵敏度和准确度高,适用于大批量畜禽肝脏样品中氟虫腈及其代谢物残留的日常测定。
Keywords: dispersive solid phase extraction (dSPE); fipronil and its metabolites; high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS); livestock and poultry liver.