串联质谱法检测洋葱中36种例行监测农药及其基质效应的探讨

建立了气相色谱-串联质谱(GC-MS/MS)同时测定洋葱中36种例行监测农药残留的方法。样品经过乙腈提取,异丙基键合硅胶+石墨化炭黑(NH2/Carbon)复合固相萃取小柱净化,以串联质谱作为检测器,多反应监测(MRM)模式进行测定。农药在0.020 mg/kg的添加水平时,采用基质后加标制定标准曲线校正,除甲胺磷、敌敌畏、乙酰甲胺磷、氧乐果外,农药的回收率为73.4%～110.0%,RSD(n=5)为2.8%～11.7%,检出限为0.2～11.1μg/kg。同时探讨了36种农药通过串联质谱法检测的基质效应情况,结果表明采用三种不同方式配制标准溶液,标准曲线斜率大小顺序为:洋葱基质后加标>洋葱基质前加标>试剂标样(正己烷:丙酮(9+1))。采用基质后加标,能节省标样配制时间,同时克服基质效应对校正结果的影响。

Study on Detection and Matrix Effects of 36 Routine Monitoring Pesticides in Onion by Gas Chromatography-tandem Mass Spectrometry

A gas chromatography-tandem mass spectrometry(GC-MS/MS) method was established for analysis of 36 routine monitoring pesticides in onion.The samples were extracted by acetonitrile,and cleaned up by an NH2/Carbon SPE column;Then the extracts was determined with a MS/MS detector based on MRM.When the spiked levels were 0.020 mg/kg,the average recoveries ranged from 73.4 % to 110.0 % except for methamidophos,dichlorvos,acephate and omethoate,the RSD(n=5) ranged from 2.8 %~11.7 %,and the detection limits(3S/N) of this method were 0.2 ~11.1 μg/kg.As standard curves were prepared in three different ways,the slopes were followed the order: after-spiking standard in the onion matrix>before-spiking standard in onion matrix > standard in reagent(hexane : acetone(9+1)).Using after-spiking standard in the onion matrix to calibrate can save time as well as overcome the matrix-effect influence in the results.