气相色谱-负离子化学电离质谱法分析测定蔬菜水果中有机磷农药的残留

将气相色谱-负离子化学电离质谱法(GC-NCI-MS)应用于蔬菜水果中9种有机磷农药残留的分析测定,初步解析了这些农药的NCI-MS特征阴离子结构和断裂机理,并初步探讨了GC-NCI-MS分析蔬菜水果中有机磷农药残留时基体效应的影响。采用空白样品基体匹配校准曲线法(MC)进行定量分析,有效地降低了基体效应的影响。蔬菜水果样品用乙酸乙酯超声提取,以乙硫磷为内标物,采用GC-NCI-MS的选择离子监测方式(SIM)进行定性和定量分析。9种有机磷农药的方法检测限为0.12～1.0 μg/kg。在方法的检测限与1000 μg/kg范围内,线性相关系数都大于0.9993。当空白蔬菜水果(西红柿）样品的加标水平为100，400，800 μg/kg时,平均加标回收率为78%～126%,相对标准偏差为0.58%～14.7%。

Multiresidue Determination of Organophosphorus Pesticide Residues in Vegetables and Fruit by Gas Chromatography-Negative Ion Chemical Ionization-Mass Spectrometry

An analytical method of gas chromatography coupled with negative ion chemical ionization-mass spectrometry for simultaneous determination of nine organophosphorus pesticide residues in vegetables and fruit has been developed, and the negative ions structure and partition mechanism of the nine organophosphorus pesticides were interpreted. Meanwhile, the matrix effect for sample analysis was discussed, and matrix-matched calibration for quantification was introduced to reduce the matrix effect in this method. Pesticides were extracted from sample with ethyl acetate in an ultrasonic bath, then determined by gas chromatography-mass spectrometry operated in negative chemical ionization mode and quantified in selective ion monitoring mode, and ethion was used as an internal standard. The detection limits of the method were 0.12-1.0 microg/kg for the nine organophosphorus pesticides, and the relative coefficients were higher than 0.9993. A blank sample (tomato) was spiked at 100, 400, 800 microg/kg for each pesticide, and the recoveries were determined to be from 78% to 126% with relative standard deviations from 0.58% to 14.7% for the pesticides.