Study On QuEChERS Method And Direct Mass Spectrometry Analysis Of Pesticide Residues

With the rising of peoples’s living standard, pesticide residue has been highly concerned to the international community. Many developed countries like Japans, European Union and American have controlled the pesticide residues more strictly. The maximum residue levels (MRLs) of pesticids in food have been established, so food export of our country are facing more and more technical barriers. Therefore, the establishment of quick and efficient methods for pesticides multi-residue analysis is one of important research duties.sample pretreatment has become a bottleneck step in analytical procedure of pesticides multi-residue analysis. The QuEChERS method, which stands for Quick, Easy, Cheap, Effective, Rugged and Safe, was introduced in2003by Anastassiades and Lehotay, et al. for the determination of pesticide residues in various produce. The main object in our study is to discuss the factor impact the results of QuEChERS pretreatment method, and develop the method for determination of pesticide residues in tea and vegetables based on GC/MS with QuEChERS. Methamidophos residue in vegetables was rapidly determined by Desorption Corona Beam Ionization Mass Spectrometry (DCBI/MS) without sample pretreament. There are four parts: 1. This part mainly introduces some common sample preparation methods and detection technology in the analysis of pesticide residue. And it presents the general situation of QuEChERS method and DCBI/MS.2. An rapid analysis method was developed for determination of pesticides by QuEChERS-GC/MS in tea. The improvenment of QuEChERS method have resulted in increased sensitivity and cleaner matrix. The mean recoveries of16pesticides were74%-108%, RSD were in the range of13.4%-19.5%, and the limit of detection were0.004-0.023mg/kg. The recovery, RSD and LOQ of the modified QuEChERS could meet the demand of the determination of pesticide residues in tea.3. A GC/MS method combined with the QuEChERS for determination the multi-residue pesticides in spinach was developed. The recoveries were71%-112%, RSD were1.8%-12.6%, and LOQ were0.003-0.025mg/kg. Results show that this is a simple, rapid, efficient method.4. A convenient method was developed for rapid determination of methamidophos in vegetables. Methamidophos residue on the vegetables was rapidly determined by Desorption Corona Beam Ionization Mass Spectrometry, without sample pretreament. For the pakchoi cabbage sample, the linear range was0.5-15μg/mL with satisfactory linear coefficient, R2=0.9841, and the limit of detection of this method was0.05 μg/mL.The average recovery was80.8%-87.3%and the relative standard deviation was13.4%-19.5%. The proposed DCBI/MS method is a simple, rapid and reliable for rapid screening analysis of methamidophos in vegetables.