超声辅助-漂浮固化分散液液微萃取-气相色谱法测定茶叶中5种拟除虫菊酯类农药残留

Ultrasound-assisted Dispersive Liquid-liquid Microextraction Based on the Solidification of a Floating Organic Droplet Followed by Gas Chromatography for the Determination of Five Pyrethroid Pesticides in Tea Samples

建立了超声辅助-漂浮固化分散液液微萃取(UA-DLLME-SFO)-气相色谱法(GC)测定茶叶中甲氰菊酯、氟氯氰菊酯、氯氟氰菊酯、氰戊菊酯、溴氰菊酯5种拟除虫菊酯类农药残留的方法。获得最佳试验条件为20μL十六烷(萃取剂)和800μL丙酮(分散剂),质量分数为4%的氯化钠,水相pH为4,35℃超声30 min,-3℃、10 000 r·min^(-1)离心5 min后,去除水相后经气相色谱测定。结果表明:在1~150μg·kg^(-1)范围内,5种拟除虫菊酯类农药呈良好的线性关系,相关系数均大于0.9994,在1~5μg·kg^(-1)添加水平下,平均回收率为92.3%~99.6%,日内相对标准偏差(RSD)均低于3.5%(n=6),日间相对标准偏差(RSD)均低于5.9%(n=3),5种农药在茶叶中的检出限为0.11~0.24μg·kg^(-1),定量限为0.36~0.81μg·kg^(-1)。该方法操作简便、快速、安全、成本低、重现性好,适用于茶叶样品中拟除虫菊酯类农药残留的分析。

A novel ultrasound-assisted dispersive liquid-liquid microextraction based on solidification of floatingorganic droplet method(UA-DLLME-SFO)which combined with gas chromatography coupled with ECD detectorwas developed for the determination of five pyrethroid pesticides(fenpropathrin,cyfluthrin,cyhalothrin,fenvalerate,deltamethrin)in tea.The optimal liquid-liquid microextraction experiment conditions were as follows:20μLhexadecane was used as extraction solvent.After ultrasound for30min under35℃,800μL of acetone(disersivesolvent)were rapidly transferred.The NaCl Mass Fraction was4%and pH was adjusted to4.The sample solution was then centrigugated at10000r·min-1for5min under-3℃and then injected for gas chromatography analysis.It was shown that a good linearity for these pyrethroids was obtained at concentrations of1.0to150.0μg·kg-1withcorrelation coefficients higher than0.9994.The average recoveries of the5pesticides in liquid milk were in therange of92.3%to99.6%at spiked levels between1to5μg·kg-1,with intra-day relative standard deviations lowerthan3.5%(n=6)and inter-day relative standard deviations lower than5.9%(n=3).The limits of detection andquantification were0.11-0.24μg·kg-1and0.36-0.81μg·kg-1,respectively.The proposed method is simple,fast,safe,reliable and applicable for analyzing pyrethroid pesticides in tea samples.