Preparation Of Magnetic ZIF-8 Nanocomposites And Their Application In Pesticide Residue Analysis

As an important agricultural production material,pesticides are widely used in agricultural production for the control of pests and diseases,however,excessive use of pesticides can cause their residues to remain on the surface of agricultural products or enter environmental water,and eventually enrich in humans through the food chain.The low level and wide variety of pesticide residues in the environment and the serious matrix interference bring obstacles to their rapid separation and accurate determination,so it is necessary to develop efficient,rapid and sensitive detection methods.In this study,we prepared functionalized ZIF-8 nanocomposites based on ZIF-8 by adding different functional materials to enhance the adsorption performance and recovery rate of ZIF-8 to make its application wider and to establish a rapid and sensitive detection method for trace pesticide residues in tea beverages and environmental water.The main studies are as follows:1.Magnetic graphene oxide loaded ZIF-8（MGO/ZIF-8）nanocomposites with large specific surface area(462.06 m²·g^-1)and good magnetic properties(40.33 emu·g^-1)were prepared by Hummers method,chemical co-precipitation method and solvothermal preparation method,which can be used as magnetic solid phase extraction（MSPE）sorbent.The MSPE was combined with HPLC-DAD to successfully establish a method for the determination of multiple phenylurea herbicides in tea beverage samples with good linearity（R² of 0.9978-0.9989）and reproducibility（intra-day precision of 2.6-4.2%and inter-day precision of 3.1-4.5%）and LODs of 0.42-0.64 ng·m L^-1.The actual sample spiked recoveries were 87.0-101.0%with RSD less than 4.5%.The experimental results showed that MGO/ZIF-8 nanocomposite is a stable and efficient MSPE adsorbent with strong adsorption capacity for phenylurea herbicides,which exhibits potential applications in the enrichment and separation of pesticide residues in tea beverages.2.Magnetic ZIF-8（Fe₃O₄/ZIF-8）nanocomposites were prepared by chemical co-precipitation and solvothermal preparation,which were used as MSPE adsorbents for the analysis and detection of pyrethroid pesticides in river water,lake water and tap water in combination with HPLC-DAD.Under the optimized MSPE conditions（40 mg of adsorbent,20min of adsorption time,p H 7.0 and 3 min of elution）,three pyrethroid insecticides in the range of 10-500 ng-m L-1 were enriched and separated with detection limits of 0.092-0.15 ng·m L^-1 and intra-day and inter-day precision of 2.7-4.5%and 3.6-4.7%.The spiked recoveries were 86.1-101.2%with relative standard deviations of 1.5-3.3%using the method for the analysis of actual water samples.The results show that the magnetic ZIF-8 nanocomposites have good adsorption properties and magnetic properties,demonstrating the promising application of this material for pyrethroid insecticide enrichment and separation.