Preparation Of Novel MOFs Solid Phase Extraction Adsorbent And Its Application In Detection Of Pesticide Residues In Fruits And Vegetables

Pesticides are often used to increase the yield of crops,resulting in pesticide abuse,in which pesticide residues in crops and food endanger human health and pollute the environment.In recent years,metal organic frameworks?MOFs?has become a hot research topic in the field of pesticide pretreatment and adsorption removal because of MOFs large specific surface area,good adsorption performance and easy control of structure and size.Metal-organic frame composite materials are prepared by combining conventional MOFs with certain materials,and the two form complementary advantages,can realize the high-efficiency enrichment and rapid purification of the pesticide in the complex matrix.The construction of a new type of MOFs composites with stable crystal structure,superior multi-residue specific adsorption,strong hydrophilicity are still urgent problems to be solved in the field of mofs pesticide pretreatment.According to the characteristics of pesticides and different synthesis strategies,stable functionalized MOFs composite materials are prepared,thus realizing high-throughput specific adsorption of multiple pesticide residues,which is of great significance for exploring new synthesis strategies and broadening the application of composite materials in food safety analysis.?1?a double-layer MOFs composite material Fe₃O₄-ZIF-8@ZIF-67 is prepared on the surface of Fe₃O₄ nanoparticles by an in-situ polymerization method.The composite material has larger specific surface area and stronger adsorption performance,and can be used as an adsorbent to rapidly and efficiently enrich pesticides fipronil and its derivative.The structural characteristics and morphology composition of the two-layer MOFs composite were analyzed.The experimental results show that Fe₃O₄-ZIF-8@ZIF-67 has good adsorption for fipronil pesticides.Static adsorption conforms to Freundlich bimolecular adsorption model and dynamic adsorption conforms to pseudo second-order kinetic model.Under the optimal experimental conditions,combined with HPLC-MS-MS,the enrichment methods of fipronil and its derivatives pesticides in environmental water samples and cucumber samples were constructed.?2?Fe₃O₄-g-C₃N₄-PDA@MIL-101?Fe?nanocomposites were successfully prepared by layer-by-layer self-assembly and directional anchoring modification strategies,The experimental results show that the composite material has superparamagnetism,high specific surface area,uniform and porous inside,etc.Under the optimal adsorption-desorption conditions,Fe₃O₄-g-C₃N₄-PDA@MIL-101?Fe?was used as magnetic solid phase extraction adsorbent to realize high flux adsorption and enrichment of organophosphorus pesticides.Magnetic dispersion solid phase extraction combined with HPLC-MS/MS successfully established a multi-residue detection method for three organophosphorus pesticides in Chinese cabbage and scallion.?3?Three-dimensional mesh crystal material Fe₃O₄-MWCNT@MOF-199 with high specific surface area is prepared by co-precipitation and surface polymerization and was used as a magnetic solid phase extraction adsorbent to enrich triazole fungicides.The experimental results show that Fe₃O₄-MWCNT@MOF-199 has high specific surface area?197.50 m²/g?and stability,regular shape and uniform structure.Through the optimization experiment,the optimal adsorption-desorption conditions of the composite were obtained.Furthermore,a HPLC-MS-MS multi-residue detection method for triazole fungicides in real fruits and vegetables samples was successfully constructed.