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    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

    • 摘要: 茶叶样品(1.00g)用水5 mL湿润后加入50 mL乙腈高速匀浆提取3 min。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20.0 mL于45 ℃蒸发至近干,加入乙酸乙酯-环己烷(1+1)混合溶剂10.0 mL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4.7 mL·min-1。收集9~20 min时间段的流出液,在45 ℃蒸至近干,加正己烷定容为5.0 mL,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0.02~0.50 mg·L-1。检出限(3S/N)在1×10-4~2×10-3mg·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。

       

      Abstract: 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 min. The mixture was filtered into a cylinder containing 2 g of solid NaCl. 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 GC 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 83.2%-114.6% and 0.9%-4.8% respectively.

       

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