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

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。

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

A novel ultrasound-assisted dispersive liquid-liquid microextraction based on solidification of floating organic droplet method (UA-DLLME-SFO) which combined with gas chromatography coupled with ECD detector was 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: 20 μL hexadecane was used as extraction solvent. After ultrasound for 30 min under 35℃, 800 μL of acetone (disersive solvent) were rapidly transferred. The NaCl Mass Fraction was 4% and pH was adjusted to 4. The sample solution was then centrigugated at 10000 r·min-1 for 5 min under -3℃ and then injected for gas chromatography analysis. It was shown that a good linearity for these pyrethroids was obtained at concentrations of 1.0 to 150.0 μg·kg-1 with correlation coefficients higher than 0.9994. The average recoveries of the 5 pesticides in liquid milk were in the range of 92.3% to 99.6% at spiked levels between 1 to 5 μg·kg-1, with intra-day relative standard deviations lower than 3.5%(n=6)and inter-day relative standard deviations lower than 5.9% (n=3). The limits of detection and quantification were 0.11-0.24 μg·kg-1 and 0.36-0.81 μg·kg-1 , respectively. The proposed method is simple, fast, safe, reliable and applicable for analyzing pyrethroid pesticides in tea samples.