Application And Research Of Polyethylene Glycol Sol-Gel In Pesticide Residue Detection And Pesticide Synergistic Effect

The low utilization rate of pesticides has contributed to the excessive application of pesticides indirectly causing the increasing problem of pesticide residues on vegetables.How to detect pesticide residues on vegetables easily and quickly and develop pesticide products with higher utilization rates has been a concern of domestic and foreign researchers.In this paper,polyethylene glycol was selected as the precursor to make a strong polar sol-gel,and the fiber cloth was used as the coating substrate.The sol-gel was coated onto the fiber cloth,and the polyethylene glycol sol-gel fiber cloth and the truncated solid phase extraction column were fixed together by magnetic stirring beads,so that the fiber cloth could be stirred automatically under the action of magnetic stirrer during the whole extraction process.The residues of 48 pesticides in tomato,cucumber and cabbage were simultaneously detected by high performance liquid chromatography-tandem mass spectrometry(HPLC-MS/MS)combined with magnetic stirring FPSE(Fabric Phase Sorptive Extraction)technique.A series of optimization of the extraction conditions were carried out,and the best extraction results were obtained when the speed of the magnetic stirrer was 1500 rpm/min,the stirring time of the magnetic stirrer was 25 min,no sodium chloride was added to the sample,the p H of the sample solution was not adjusted,and 500 μL of ethyl acetate and acetone were used for the desorption for 5 min each.The methodological validation of the target pesticides showed that the limits of detection(LOD)of the 48 pesticides ranged from 0.014 to 6.280 ng/g.The results showed that the recoveries ranged from 71.4% to 99.8% with the relative standard deviations(RSDs)of the three samples of tomato,cucumber and cabbage at 10ng/g,50 ng/g and 100 ng/g.The results showed that the recoveries ranged from71.4% to 99.8%,and the relative standard deviations(RSDs)were less than 7.8%.In addition,when polyethylene glycol sol-gel was added with pesticide in appropriate ratio,it was observed that the sol-gel used its polyhydroxy property as a "bridge" connecting the pesticide and the cuticle of the leaf to enhance the adhesion of the pesticide on the crop leaf.The results showed that the pesticide structure after the addition of sol-gel was more compact with regular hexagonal microstructure,and the contact angle with the leaves was reduced by 5.6～7° at different concentrations,and the adhesion performance of the pesticide was increased by 26%.This study demonstrated the feasibility of strong polar polyethylene glycol sol-gel fiber cloth for the extraction of low and medium polarity pesticides on vegetables.The conditions and instrument parameters in the extraction process were also systematically studied and optimized,and the results showed that the assay was specific,reproducible and sensitive.Sol-gel is also a good pesticide additive,after adding sol-gel to pesticides,it increases the adhesion of pesticides,reduces the loss of pesticides in wind and rain,and reduces the amount of pesticides used.Therefore,sol-gels have great potential for applications in sorptive extraction of target analytes,improving pesticide utilization and controlling pests.