茶叶中9种有机氯和拟除虫菊酯农药残留的前处理方法研究

Study on Pretreatment Technique of Nine Organochlorine and Pyrethroid Pesticides in Tea by GC-MS

建立了一种简便准确的前处理方法用于茶叶中5种有机氯农药和4种拟除虫菊酯类农药的测定。对索氏提取、超声提取、加速溶剂萃取和振荡提取4种提取方法的参数条件进行优化和对比,并对前处理的净化条件进行优化,建立了丙酮-正己烷(7∶3,体积比)溶液振荡提取串联Envi-Carb和LC-AliminaN小柱净化后,经丙酮-正己烷(1∶9)溶液洗脱,浓缩后用GC-MS法测定。茶叶样品中9种农药的加标回收率(n=6)为82%～108%,相对标准偏差为1.2%～4.5%,方法的检出限(以3倍信噪比计)为0.46～12.13ng/g。

A simple and repeatable pretreatment method was developed for gas chromatography-mass spectrometry（GC-MS）determination of five organochlorines and four pyrethroid pesticides residues in tea.The operating parameters for Soxhlet extraction（SE）,ultrasonic extraction（USE）,accelerated solvent extraction（ASE）and oscillation extraction（OE）of pesticides residues in tea samples were optimized and compared.The cleanup procedures for each of the extraction method were also studied and optimized.Experimental results showed that for SE and ASE,the target analytes were cleaned up using gel permeation chromatography（GPC）to eliminate most of the coextracts,such as pigments,lipids and waxes,followed by cleaning up with Envi-Carb and LC-Alimina N solid phase extraction（SPE）cartridges prior to GC-MS.For OE and USE,only SPE was necessary for cleanup.In view of the simple cleanup means and good recovery and RSD,OE was selected for the pesticides pretreatment method.The overall procedure is as follows：40 mL of acetone-hexane（7∶3,by volume）used as extractants for oscillation extracting 40 min,followed by cleaning up with columns of Envi-Carb combined with LC-Alimina N,then eluted by 7 mL of acetone-hexane（1∶9,by volume）prior to GC-MS.The spiked recoveries ranged from 82% to 108% with relative standard deviations of 1.2%-4.5%and the limits of detection（S/N=3）varied from 0.46 ng/g to 12.13 ng/g.The proposed method was sensitive and highly efficient,and was successfully applied in the determination of pesticide residues in 6 kinds of tea samples with satisfactory results.