Determination Of Pesticide Multi-Residues In Vegetables By GC-MS And GC-QqQ-MS/MS

Nowadays, food safety has caught great attention by the society. As one of the most important issues, the determination of pesticide residues has been widely concerned by governments and organizations all over the world. Limitation requirements of the pesticide residues in food were set lower and lower by the worldwide governments. It is exigent to establish a determination method of pesticide multi-residues which is easy, quick, sensitive and efficient. The problem of pesticide residues in vegetables is more serious than other food. In this thesis, vegetables were selected for study.We established simple and efficient methods of pretreatment, which was based on QuEChERS method. All the pesticides with different polarity had good recoveries. Gas chromatography-mass spectrometry (GC-MS) and gas chromatography-triple quadrupole mass spectrometry (GC-QqQ-MS/MS) were selected in this thesis to establish accurate methods to detect pesticide multi-residues in vegetables. The mass spectrometry only scans the characteristic fragments of target compounds, which effectively removes interference. The determination is rapid, sensitive, effective and meets the need of pesticide residues analysis.The method of determination for 85 pesticides was studied in vegetables by GC-MS, including organochlorine pesticides, organophosphorus pesticides, herbicides, pyrethroids and carbamate pestcides. The critical steps of pretreatment were studied and discussed. Chinese cabbage and spinach were selected as samples. The spinach was processed with the adsorbent GCB while the cabbage was without the adsorbent GCB. GC-MS acquired data in selected ion monitoring mode. The recoveries of cabbage were from 73% to 124% with the RSD ranging from 1.6% to 16.2%. The LODs for cabbage were 0.002-0.03 mg/kg. The LOQs for cabbage ranged from 0.006 to 0.06 mg/kg. The recoveries of spinach were from 68% to 124% with the RSD ranging from 1.1% to 20.0%. The LODs for spinach were 0.004-0.06 mg/kg. The LOQs for spinach ranged from 0.012 to 0.18 mg/kg.A rapid multi-residue method was developed for the determination of 20 organophosphorous pesticide residues in leeks by GC-QqQ-MS/MS. The method was based on QuEChERS sample preparation method. After microwave pre-treatment, leek samples were extracted with acetonitrile containing acetic acid 0.1% and cleaned by dispersive solid phase extraction. The QqQ analyser acquired data in selected reaction monitoring mode. It could effectively remove the interferences of sulfur compounds. Recoveries of 20 organophosphorous pesticides were from 81.0% to 109.4% with the RSD ranging from 1.3% to 10.4%. The LODs were 0.07-1.5ug/kg. The LOQs ranged from 0.25 to 5ug/kg. Ten leek samples were analysed for method application.GC-QqQ-MS/MS has an advantage over GC-MS on selectivity and sensitivity. It has not only the same function as GC-MS but also the function of judge the structure of target compounds. Pesticide multi-residues in complex matrix were simultaneously detected by GC-QqQ-MS/MS.