The Research On Pretreatment Methods Based On Magnetic Materials For Enrichment Of Environmental Pollutants

The rapid development of modern industry has produced a large number of pollutants and brought great pressure to the environment.Pollutants would impose a huge impact on human health through environmental contact or the food chain,and it is very important to detect and control the concentration of pollutants in the environment.However,due to the complexity of the matrix and the low concentration of the target analytes,direct injection of sample solution for determination is often infeasible or greatly affects the accuracy of the instrument.Therefore,it is necessary to develop new materials for efficient,simple and selective pretreating samples before instrument detection to remove matrix effects and enrich target analytes.Aiming at the pollutants in the environment and taking advantages of the characteristics of magnetic solid-phase extraction such as convenient,time-saving and high-efficiency,this paper is devoted to the design and development of new magnetic solid-phase extraction materials to enrich and purify the target analytes in complex samples.The thesis mainly includes the following three parts:（1）A new guanidinium ionic liquid N,N,N’,N’-tetramethyl-N",N"-2-（3-aminopropyl）chloride[di Pr NH₂TMG]Cl（GIL）was prepared and modified covalently onto the surface of Fe₃O₄@n SiO₂ particles using polyethyleneimine as a linkage bridge The obtained Fe₃O₄@n SiO₂-GIL nanoparticles were used as the adsorption materials for magnetic solid phase extraction of polycyclic aromatic hydrocarbons（PAHs）in water and presented good enrichment efficiency.The limits of detection（LODs）were 0.05-0.1 ng?m L^-1,the recoveries of spiked samples were between 80-120%and the linear correlation coefficient（r²）was above0.996.In combination with high-performance liquid chromatography-ultraviolet detection（HPLC-UV）,the proposed method can be used for the effective extraction and determination of pollutants such as PAHs in environmental water samples.（2）Three-dimensional（3D）and flower-like magnetic SnS₂ composites Fe₃O₄@n SiO₂-SnS₂ were prepared and used to extract sulfonamide antibiotics（SAs）in tap water,milk and honey.Compared with 2D materials,the 3D SnS₂ materials were more stable and could expose more active sites.Combined with magnetic materials,the extraction and separation process were simple and efficient.The magnetic solid phase extraction conditions were optimized,and the results showed that the extraction and desorption could reach equilibrium within 2 minutes using the prepared Fe₃O₄@n SiO₂-SnS₂ materials.Combined with HPLC-UV,the LODs were 0.025 ng?m L^-1,and the r² values were above 0.9964 in the concentration range of 0.1-200 ng?m L^-1.The recoveries were acceptable for spiked real samples at three concentrations levels,ranging from 80%to 120%for milk and honey,and the RSDs were less than 13%.The results indicated that the prepared Fe₃O₄@n SiO₂-SnS₂materials had a great potential for the extraction of SAs.（3）In order to increase the specific surface area and improve extraction efficiency,a mesoporous SiO₂ layer was modified on the non-mesoporous SiO₂ surface of Fe₃O₄@n SiO₂.The amine functionalized GIL and carbon dots reacted with glutaric acid and modified on the surface of mesoporous materials,and the obtained materials were used for the enrichment of phthalate esters.Compared with non-mesoporous Fe₃O₄@n SiO₂,the specific surface area and adsorption capacity of Fe₃O₄@n SiO₂@m SiO₂ materials were larger,and higher extraction efficiency can be obtained.