浊点萃取-异辛烷反萃取-气相色谱测定茶叶中拟除虫菊酯农药残留

Cloud Point Extraction Coupled with Ultrasonic-assisted Back-extraction for Determination of Pyrethroid Pesticides in Tea by Gas Chromatography with Electron Capture Detection

建立了浊点萃取-异辛烷反萃取-气相色谱(ECD)检测茶叶中联苯菊酯(Bifenthrin)、甲氰菊酯(Fenpropathrin)、功夫菊酯(Cyhalothrin)、氯菊酯(Permethrin)、氰戊菊酯(Fenvalerate)、溴氰菊酯(Deltamethrin)6种拟除虫菊酯农药残留的方法。对含1.2%(m/V)聚乙二醇6000(PEG6000)表面活性剂和40%(m/V)(NH4)2SO4的6种拟除虫菊酯溶液进行加热萃取,所获得的富集相用异辛烷超声反萃取,并经离心对上层异辛烷溶液进行进一步净化处理,即可获得富集倍数达75倍的6种农药。本方法的检出限(LOD)为:联苯菊酯、甲氰菊酯和功夫菊酯0.4μg/kg;氰戊菊酯2.1μg/kg;氯菊酯和溴氰菊酯3.0μg/kg;用本方法测定了新鲜茶叶中6种拟除虫菊酯农药,含量分别为4.17,4.15,4.09,4.01,3.93和3.51μg/kg。在上述茶叶样品中添加20μg/kg的6种农药后测定,添加回收率为72.3%～85.6%;相对标准偏差为2.2%～5.6%。

A method was developed for the determination of pyrethroid pesticides： bifenthrin （BF）, fenpropathrin（ FP）, eyhalothrin （ CH ）, permethrin （ PM ）, fenvalerate （ FV ） and deltamethrin （ DI ） in tea proposed using the cloud point extraction （CPE） coupled with ultrasonic-assisted back-extraction prior to gas chromatography with electron capture detection. A pyrethroid solution containing 1.2% （m/V） polyethylene glycol 6000 （PEG 6000） and 40% （m/V） （NH4 ）2SO4 was heated for the extraction of the pyrethroid pesticides. The coacervation phase obtained was back extracted with isooetane. The upper isooctane solution was eentrifugated simply for further cleanup. A preconeentration factor of 75 was obtained for these six pesticides. The limits of detection（LODs） were 0.4 μg/kg for BF, FP and CH, 2.1μg/kg for FV and 3.0 μg/kg for PM and DI respectively. Six pyrethroid pesticides, BF, FP, CH, FV, DM and DI, were determined, the amounts were 4. 17, 4. 15, 4.09, 4.01, 3.93 and 3.51 μg/kg. Six pyrethroid pesticides standards of 20μg/kg were added in the tea samples mentioned above, the spiked recoveries were 72.3% - 85.6% and the relative standard deviations were 2.2% - 5.6%.