基质固相分散和GC-NCI-MS法分析果汁中拟除虫菊酯农药残留量

Multiresidue determination of pyrethroid pesticides in fruit juices by matrix solid-phase dispersion and gas chromatography-negative chemical ionization-mass spectrometry

建立了基质固相分散法（MSPD）和气相色谱-负化学离子源-质谱法（GC—NCI—MS）应用于果汁中10种拟除虫菊酯农药残留量的快速分析方法，并对这些农药NCI—MS的阴离子结构与断裂机理进行初步探讨。采用以中性氧化铝为吸附刺、Florisil硅藻土为净化剂和乙酸乙酯为洗脱剂的MSPD样品前处理方法，以PCB103为内标物和GC—NCI—MS的选择离子监测方式（SIM）进行定性与定量分析。当样品的加标浓度水平为50、250μg／kg时，平均加标回收率为86．7％～114．8％，相对标准偏差为1.9％～14．1％；除氯菊酯农药的方法检出限（MDL）为14.7μg／kg外，其余农药的MDL大都小于1．0μg／kg；线性范围为10～500μg／kg，相关系数都大于0.997，在所分析的大部分果汁中至少分析出两种以上的拟除虫菊酯农药残留。

A rapid method based on matrix solid-phase dispersion was developed for the determination of ten pyrethroid pesticides in commercial juices. Meanwhile, negative ion structure and fracture mechanism of these pesticides of negative chemical ionization mass spectrometry were evaluated. The group of pesticides was added to juice and blended with neutral alumina, the mixture was packed into disposable filtration column, this column was tandem with florisil as cleaning and was eluted with ethyl acetate. The analysis of samples was accomplished using gas chromatography with negative chemical ionization mass spectrometric detection （GC - NCI - MS） in the selected ion monitoring mode （SIM）, and with PCB103 as internal standard. Recovery studies were performed at 50 and 250μg/kg fortification levels for each pesticide, and the average recoveries ranged from 86.7 to 114.8% with a relative standard deviation between 1.9% and 14.1% for the different pesticides. The detection limit of the method was less than 1.0μg/kg for most of pesticides except for the permethrin. The developed method was linear over the range assayed, 10 ～ 500μg/kg,with correlation coefficients 〉 0. 997. The proposed method was applied to the analysis of these compounds in commercial juice samples. At least two pesticides was found in most of the samples.