加速溶剂萃取/凝胶渗透色谱－固相萃取净化、气相色谱－质谱法测定茶叶中残留的33种农药

建立了茶叶中有机磷、有机氯、拟除虫菊酯类共33种农药残留的分析方法。样品以丙酮-二氯甲烷(体积比为1:1)为提取剂经加速溶剂方法萃取,提取液用凝胶渗透色谱净化除去大部分的色素、脂类和蜡质,再用Carb-NH2小柱和Florisil小柱净化。采用气相色谱法分析、外标法定量、气相色谱-质谱法（GC-MS）定性。加标水平为0.05 mg/kg时,大部分农药的回收率为70%~120%,相对标准偏差小于20%。方法的检测限为0.005～0.05 mg/kg (以10倍信噪比计)。该方法的提取效率高,准确灵敏,目前已应用于出口茶叶中农药残留的日常检测。大量实际样品的检测结果表明,此方法适于出口茶叶中农药残留检测实际工作的需要。

Determination of 33 pesticides in tea by accelerated solvent extraction-gel permeation and solid-phase extraction purification-gas chromatography-mass spectrometry

A method has been developed for the determination of 33 pesticide residues in tea, including organophosphorous, organochlorine and pyrethroid pesticides. The target analytes were extracted with the solution of acetone/dichloromethane (1:1, v/v) using accelerated solvent extraction (ASE) and then purified using gel permeation chromatography (GPC) to eliminate most of the coextracts, such as pigments, lipids and waxes. They were further purified using Carb-NH2 and Florisil solid-phase extraction (SPE) cartridges prior to the identification using gas chromatography-mass spectrometry (GC-MS). The quantitative analysis was performed with flame photometric detector (FPD) for organophosphorous pesticides and electron capture detector (ECD) for organochlorine and pyrethroid pesticides. At the spiked level of 0.05 mg/kg, the recoveries for most pesticides were between 70%-120%; the relative standard deviations were less than 20%; the limits of detection varied from 0.005 to 0.05 mg/kg (defined in terms of 10 times of the baseline noise). This method is precise, sensitive and highly efficient in extraction. After routine applications, the results indicated that this method is suitable for the determination of pesticide residues in the tea for export.