凝胶渗透色谱净化-气相色谱法测定茶叶中30种有机氯及菊酯类农药残留量

GC Determination of 30 Organochlorine and Pyrethrin Pesticides in Tea with Clean-up by Gel Permeation Chromatography

茶叶样品(1.00g)用水5 mL湿润后加入50mL乙腈高速匀浆提取3min。混合物滤入已盛有固体氯化钠2 g的具塞量筒中,取上清液20.0mL于45℃蒸发至近干,加入乙酸乙酯环己烷(1+1)混合溶剂10.0mL溶解残渣后进行凝胶渗透色谱(GPC)净化。流动相为上述混合溶剂,流量为4.7mL·min^(-1)。收集9～20min时间段的流出液,在45℃蒸至近干,加正己烷定容为5.0mL,供气相色谱分析。采用Rxi-5MS石英毛细管柱进行分离和电子捕获检测器进行检测,所测农药的线性范围为0.02～0.50mg·L^(-1)。检出限(3S/N)在1×10^(-4)～2×10^(-3)mg·kg^(-1)之间。试验测得方法的回收率在83.2%～114.6%之间,测定值的相对标准偏差(n=5)在0.9%～4.8%之间。

The tea sample （1. 00 g） was moistened with 5 mL of water and extracted with 50 mL of acetonitrile by rotating homogenization for 3 rain. The mixture was filtered into a cylinder containing 2 g of solid NaC1. The supernatant （20. 0 mL） was taken and evaporated to near dryness at 45 ℃. The residue was taken up with 10. 0 mL of mixed solvent ethyl acetate and cyclohexane（1＋1）. The solution was then purified by GPC with the same mixed solvent as mobile phase at a flow rate of 4.7 mL . min-1. Eluate flowed out during the interval 9- 20 min was collected and evaporated to near dryness at 45 ℃. The residue was taken up with 5.0 mL of n-hexane and used for CC analysis using the Rxi -5MS quartz capillary column for separation and ECD for detection. Linearity ranges of the pesticides were kept in the same range of 0. 02 - 0. 50 mg . L-1 , with detection limits （3S/ N） ranged from 1×10 4 to 2×10-3mg .kg 1. Results of recovery and RSD＇s （n：5） were found in the ranges of 83. 25-114.6% and 0.9%-4. 8% respectively.