Application Of Functional Magnetic Metal Organic Framework Composites In The Extraction Of Organic Pesticide Residues

With the increasing demand of pesticides for modern agriculture,the overproof pesticide residues has become one of the most serious global issues.The residues in environment and crops can transfer into the human body through food chain,and cause various chronic diseases even cancers,which seriously threaten human health.Therefore,it is significantly important to analyze trace pesticides in different matrices.Because of their high specific surface,remarkable stability and abundant active sites,metal-organic frameworks(MOFs)have been widely applied in sample pretreatment.Thus in this work,focused on MOF materials,the functional nanocomposites with outstanding adsorption performance and high magnetic response were prepared and applied in the extraction and enrichment of pesticide residues in various matrices combined with liquid chromatography technique.Magnetic zeolite imidazole framework nanocomposite(ZIF-8/SiO2@Fe3O4)was fabricated via a self-assembly technique under sonication,and used as an adsorbent for extraction of the four triazine herbicides in fruit,vegetable,and water samples prior to liquid chromatography and mass spectrometry analysis.The prepared composite,which was held together by electrostatic forces,combined the advantages of ZIFs and magnetic materials.Under the optimum conditions,the detection limits of the four targets were 0.18-0.72 ng mL-1.Comparisons of extraction efficiency with different MOF materials assembled on magnetic nanoparticle were further performed.As a result,due to the lower steric hindrance,higher surface and stability,the numerous Zn2+ sites and imidazole ligands of ZIF-8 material,magnetic ZIF-8 composite possessed better adsorption capability towards the target through stronger π-πconjugation and π-complexation interactions.Therefore,the synthetic nanocomposite was efficient and had good potential for extraction of triazine residues from complex samples.A novel magnetic metal-organic framework composite,functionalized with chitosan and MIL-101(Cr),was prepared through inverse emulsion cross-linking and hydrothermal methods.It was then utilized in a magnetic solid phase extraction of the four benzoylurea insecticides in tea beverage and fruit juice samples,in combination with liquid chromatography analysis.The main experimental parameters affecting the extraction efficiency were optimized and the reusability performance of the adsorbent was evaluated.Under the optimum conditions,the detection limits of the targets were 0.29-0.44 ng mL-1.The absolute and relative recoveries were 80.3-90.8%and 88.0-102.1%,respectively.Besides,comparisons of extraction efficiency with different adsorbents were further performed.As a result,based on the advantages of the two modification materials,the functional composite exhibited unique characteristics(high specific surface,excellent dispersion and stability,abundant adsorption binding sites)and possessed better extraction efficiency towards the target compound.