分散固相萃取-气相色谱法测定茶鲜叶中7种拟除虫菊酯类农药残留

建立了超声波提取、分散固相萃取净化、气相色谱-电子捕获法(GC-ECD)同时测定茶鲜叶中甲氰菊酯、高效氯氟氰菊酯、氯菊酯、氟氯氰菊酯、氯氰菊酯、氰戊菊酯和溴氰菊酯7种拟除虫菊酯类农药残留的方法。样品采用V(乙酸)∶V(乙腈)=1∶99的混合溶剂超声提取,适量乙二胺-N-丙基硅烷(PSA)、十八烷基硅烷键合硅胶(C18)和石墨化碳黑(GCB)吸附剂净化,GC-ECD测定,基质外标法定量。结果表明:在0.004~2 mg/L范围内,7种拟除虫菊酯类农药的峰面积与相应质量浓度间呈良好的线性关系,相关系数均大于0.999;在0.01~0.5 mg/kg的添加水平下,平均回收率为80%~101%,日内相对标准偏差(RSD)均小于8.4%(n=6),日间RSD均小于9.3%(n=3);7种农药在茶鲜叶中的检出限为0.002~0.02 mg/kg,定量限为0.01~0.05 mg/kg。该方法操作简单、定量准确、溶剂用量少,对检测条件要求低,可同时测定茶鲜叶中7种拟除虫菊酯农药的残留量。

Determination of pyrethroid residues in fresh tea leaves by dispersive solid phase extraction and gas chromatography

A GC-ECD method based on ultrasound assisted extraction (UAE) and dispersive solid phase extraction (DSPE) was established for simultaneous determination of 7 pyrethroid insecticides (fenpropathrin, lambda-cyhalothrin, permethrin, cyfluthrin, cypermethrin, fenvalerate, deltamethrin) in fresh tea leaves. Samples were extracted ultrasonically with V(acetic acid):V(acetonitrile) =1:99, followed by the DSPE clean-up using primary secondary amine (PSA), octadecylsilane bonded silica (C₁₈) and graphitized carbon black (GCB) as adsorbents. The sample extracts were determined by GC-ECD with matrix-matched external standard method. It was shown that good linearity was obtained at concentrations of 0.004-2 mg/L with correlation coefficients higher than 0.999 for these pyrethroids. The average recoveries of the 7 pesticides in fresh tea leaves were in the range of 80% to 101% at spiked levels of 0.01-0.5 mg/kg, with intra-day relative standard deviations lower than 8.4% (n=6) and inter-day relative standard deviations lower than 9.3% (n=3). The limits of detection and quantification were 0.002-0.02 mg/kg and 0.01-0.05 mg/kg, respectively. The method was simple, accurate, solvent saving. It was shown to be a suitable MRM method for determination of pyrethroid residues in fresh tea leaves.