Establishment Of A Fast Screening Method For Pesticide Residues Based On Low Temperature Plasma Mass Spectrometry

In order to meet the current demand for rapid screening of agricultural residues in fruit and vegetable market,this paper mainly uses open ion source technology combined with high resolution time-of-flight mass spectrometer to establish a rapid,efficient and accurate method for the detection of pesticide residues in fruits and vegetables.First of all,the thermally assisted desorption temperature,helium flow rate and ion transport tube temperature in thermally desorption-low temperature plasma source(TD-LTP)were debugged and optimized,and the best experimental parameters were determined.After that,a thermally assisted desorptionlow temperature plasma source time-of-flight mass spectrometry(TD-LTP-TOFMS)experimental platform for rapid screening of pesticide residues was established by combining the above TD-LTP ionization source with high resolution time-of-flight mass spectrometry(TOFMS).The performance of the built TD-LTP-TOFMS is characterized to determine the quality resolution,quality accuracy,quality range and stability of the platform.Through the qualitative and quantitative analysis of the pesticide standard triazophos and the false negative / positive detection rate of the labeled samples,the results show that the resolution of the instrument is more than 7500,and the quality range is 55.27?998.32 Da,stability RSD < 20%.In order to meet the detection requirements of representative pesticides in fruits and vegetables,with reference to the different rules for the detection of agricultural residues in fruits and vegetables in the 2019?Implementation rules for sampling inspection of national food safety supervision?referred to as the "National sampling rules".The instrument platform set up in this study can meet the requirements of 94% of the national sampling rules for the detection of agricultural residues.Based on the pretreatment operation method of Qu ECh ERS(Quick?Easy?Cheap?Effective?Rugged?Safe),combined with the characteristics of strong tolerance of sample matrix and high salt tolerance of TDLTP-TOFMS rapid detection platform,the pretreatment process was simplified.Firstly,the pretreatment method for testing the fruit and vegetable samples was explored,which mainly included weighing,homogenizing,adding acetonitrile and shock centrifugation,and the supernatant was detected.The results showed that in the addition test of 6 groups of matrix samples(leek,cucumber,bract,rape,eggplant and Chinese cabbage),all the labeled pesticides could be detected except carbofuran.In order to ensure that pesticides in different substrates can meet the detection requirements of GB 2763-2019?National food safety standard-Maximum residue limits for pesticdes in food?.Then,the pretreatment process of direct extraction was further optimized and the effects of adding Na Cl and not adding Na Cl on pesticide detection in six groups of matrix samples were compared.The results showed that the sensitivity of the quality peak of target pesticide sample could be effectively enhanced by adding Na Cl,and carbofuran could be detected in cucumber,leek,bract,eggplant and Chinese cabbage,which could realize the rapid screening of multi-residual pesticides in complex matrix.Under the condition of pre-treatment,the methodology of the actual fruit and vegetable samples was verified,and the linear range,correlation coefficient and detection limit of the samples were obtained,which met the requirements of MRL in GB 2763-2019.Through the preliminary screening of 127 pesticides in the national smoking rules,119 pesticides can be detected in this system.After that,the detection limits of these 119 pesticides were tested,and the detection limits of 116 pesticides met the requirements of GB 2763-2019 MRL.Based on the detection requirements of different fruits and vegetables in the national standard,47 kinds of pesticides were selected,and 6 kinds of fruit and vegetable matrix samples were tested.The results showed that the detection rate was between 82% ?100%.The TD-LTP-TOFMS detection method established in this paper can quickly and accurately analyze the types and range of pesticide residues in different fruits and vegetables,realize high-speed,non-targeted and broad-spectrum screening of pesticide residues in fruits and vegetables,and provide a rapid screening method based on mass spectrometry for fast circulating fruits and vegetables in the market.