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建立了微波辅助萃取结合气相色谱-飞行时间质谱(GC-TOF MS)技术在负化学电离(NCI)源和电子轰击电离(EI)源两种模式下测定烟草中24种农药残留的分析方法。烟叶样品于100℃下用二氯甲烷-正己烷(3∶1,v/v)混合溶剂微波萃取10 min,萃取液经弗罗里硅土固相萃取柱净化后进行检测分析。在NCI源和EI源质谱模式下,24种农药的线性关系均良好(r2>0.99),相对标准偏差分别小于8.6%和9.1%,定量限分别为0.3~6.9μg/kg和10.2~44.9μg/kg,加标回收率分别为75.2%~94.8%和75.0%~95.1%。比较两种离子源模式下的色谱图和质谱图,NCI源模式较EI源模式的选择性好、灵敏度高、基质干扰小、图谱简单易于解析,检出限低一个数量级以上,在分析低含量、复杂基质的样品时更具优势。
A method for the determination of 24 pesticide residues in tobacco by microwave assisted extraction combined with gas chromatography-time of flight mass spectrometry (GC-TOF MS) was developed in two modes: negative chemical ionization (NCI) and electron impact ionization (EI) The tobacco leaves samples were extracted with dichloromethane-n-hexane (3: 1, v / v) by microwave for 10 min at 100 ℃. The extracts were purified by Florisil solid-phase extraction. The linearity of 24 pesticides was good (r2> 0.99) with relative standard deviations of less than 8.6% and 9.1%, respectively, with limits of quantification of 0.3 to 6.9 μg / kg and 10.2 to 44.9 μg / kg, the recoveries were 75.2% ~ 94.8% and 75.0% ~ 95.1%, respectively. Comparing the chromatograms and spectra of two ion source modes, the NCI source mode has better selectivity than EI source mode, high sensitivity, less matrix interference, simple and easy to interpret the spectrum, the detection limit is more than an order of magnitude lower, , Complex matrix samples even more advantages.