从1.0 kg蔬菜中选其可食用部分,切碎后用四分法取样,取适量样品经充分捣碎制得分析用样品。称取试样25.00 g用50 mL乙腈高速匀浆提取,收集滤液40~50 mL与5 g氯化钠振荡盐析。定量分取上层清液10 mL置于80 ℃水浴上吹氮至干,加正己烷2 mL溶解残渣,所得溶液流经Florisil小柱纯化,用丙酮-正己烷(1+9)混合液淋洗2次,每次5 mL,洗脱液在50 ℃水浴上吹氮至干,用正己烷定容至2.0 mL,取1 μL进样进行气相色谱分析。采用Varian CP-Sil 5CB毛细管色谱柱分离及电子捕获检测器定量检测,5种拟除虫菊酯类农药可很好地分离。其峰面积值与相应质量浓度均在0.01~1.0 mg·L-1之间呈线性,检出限(3S/N)在1.6~2.0 μg·kg-1之间。在3个浓度水平上(0.02,0.10,0.50 mg·kg-1)加入各农药标准溶液,按方法作回收率及精密度试验,测得回收率和相对标准偏差(n=6)分别在90.5%~106.4%和0.98%~6.3%之间。

Edible parts of 1.0 kg of vegetable were taken, cut up and sampled by quartering. An appropriate amount of the sample was pounded thoroughly to prepare the sample for analysis. 25.00 g of the sample was extracted with 50 mL of acetonitrile for 3-5 min by high speed homogenization, and 40-50 mL of the filtrate was salted out by shaking with 5 g of NaCl. An aliquot of 10 mL of the supernatant was taken and blown to dryness with nitrogen at 80 ℃ over a water-bath. The residue was taken up with 2 mL of n-hexane, which was purified on Florisil column. The column was eluted twice with 5 mL of mixed solvent of acetone-n-hexane (1+9), and the eluates were combined and blown to dryness by nitrogen at 50 ℃ on a water bath. The residue was taken up with 2.0 mL of n-hexane, and 1 μL was taken from it for GC analysis using Varian CP-Sil 5CB capillary column for separation and ECD for determination. Five pyrethroid pesticides were satisfactorily separated under this condition. Linearity ranges between values of peak area and mass concentration of the pesticides were found same between 0.01 and 1.0 mg·L-1, with detection limits (3S/N) in the range of 1.6-2.0 μg·kg-1. Recovery and precision were tested by standard addition method at 3 concentration levels (0.02, 0.01, 0.50 mg·kg-1), giving results of recovery in the range of 90.5%-106.4% and RSD′s (n=6) ranged from 0.98% to 6.3%.