QuEChERS-气相色谱-负化学电离源-串联质谱法测定茶叶中氟虫腈及其代谢物的残留量

Determination of Residues of Fipronil and Its Metabolites in Tea by Gas Chromatography-Negative Chemical Ionization-Tandem Mass Spectrometry with QuEChERS

取2.00 g茶叶样品,用10 mL水浸泡,再用10 mL乙腈、QuEChERS萃取盐包(含6 g硫酸镁、1.5 g乙酸钠)离心提取。吸取8 mL上清液,加到QuEChERS净化盐管[内装1200 mg硫酸镁、400 mg N-丙基乙二胺(PSA)、400 mg C_(18)和200 mg石墨化碳黑(GCB)]内,振荡、离心,取上清液,过0.45μm滤膜后,采用气相色谱-负化学电离源-串联质谱法(GC-NCI-MS/MS)测定滤液中氟虫腈及其代谢物氟甲腈、氟虫腈砜和氟虫腈亚砜的含量,基质匹配法定量。结果表明,氟虫腈及其代谢物的质量分数均在0.005~0.50 mg·kg^(-1)内与其对应的峰面积呈线性关系,检出限(3S/N)为0.25~0.5μg·kg^(-1)。按照标准加入法进行回收试验,回收率为96.6%~136%,测定值的相对标准偏差(n=6)均小于7.0%。方法用于分析100批茶叶,在某一批次茶叶样品中检出氟虫腈及其代谢物,总量为77.1μg·kg^(-1)(以氟虫腈计)。

2.00 g of the tea sample was taken,then soaked in 10 mL of water,and centrifuged for extraction with 10 mL of acetonitrile and QuEChERS extraction salt(containing 6 g of magnesium sulfate and 1.5 g of sodium acetate).8 mL of the supernatant was taken and added into the QuEChERS purification salt tube[containing 1200 mg of magnesium sulfate,400 mg of N-propyl ethylenediamine(PSA),400 mg of C_(18) and 200 mg of graphite carbon black(GCB)].After shaking and centrifuging,the supernatant was taken and passed through 0.45μm filter membrane.Gas chromatography-negative chemical ionization-tandem mass spectrometry(GC-NCI-MS/MS)was used to determine fipronil and its metabolites fipronil desulfinyl,fipronil sulfone and fipronil sulfoxide in filtrate,with matrix matching method for quantification.As shown by the results,linear relationships between values of the corresponding peak area and mass fraction of fipronil and its metabolites were found in the range of 0.005-0.50 mg·kg^(-1),with detection limits(3S/N)in the range of 0.25-0.5μg·kg^(-1).Test for recovery was made by the standard addition method,giving the results in the range of 96.6%-136%,with RSDs(n=6)of the determined values less than 7.0%.This method was used for the analysis of 100 batches of tea,and fipronil and its metabolites were detected in a certain batch of tea samples,with a total amount of 77.1μg·kg^(-1)(calculated by fipronil).