The Study On The Application Of Composite Materials With Hollow Multishelled Structure In Solid Phase Microextraction

Sample pretreatment techniques plays a critical role in the analysis of complex samples（e.g.biological,food and environmental samples）and is the key in the whole analytical process.Solid phase microextraction（SPME）is a new sample pretreatment technique that integrates the collection,separation,enrichment,desorption and injection steps from complex sample matrices.This kind of solvent-free or solvent less solid phase extraction technique have short extraction time、high extraction efficiency、and easy to achieve automated operation,in which the sorbent medium（material）is the core of this kind of extraction technology,so the development of high selectivity and enrichment of sorbent materials is the bottleneck problem.Hollow Multishelled Structure（HoMS）,as a special class of micro-and nanomaterials,has a thin multilayer hollow structure,which greatly shortens the transport path,accelerates the mass transfer rate and shortens the equilibrium time,making HoMS become a new competitive nanomaterial in recent years and showing great potential in the field of sample pretreatment.It has shown great potential application in the field of sample pretreatment.Therefore,in this thesis,three different types of hollow multishell structure（HoMS）composites were designed and prepared as sorbent materials for solid-phase microextraction（SPME）to separate and enrich trace organic pollutants in environmental samples,which was combined with high performance liquid chromatography（HPLC）for the analysis of pesticides and polycyclic aromatic hydrocarbons（PAHs）in environmental samples.This dissertation consists of three chapters:Chapter one:Firstly,the main types of hollow multishell structure（HoMS）composites,synthesis methods including template-free method（Ostwald ripening,Kirkendall effect and directional attachment）,and template method（soft template method,hard template method and self-template method）are described in detail,and the applications of HoMS composites in the field of sample pretreatment,such as solid phase extraction,solid phase microextraction,magnetic solid phase extraction and dispersive solid phase extraction,are reviewed.Chapter two:A novel solid-phase microextraction（SPME）fiber coating based on organosilicon copper sealant/hollow single-shell layer ZnO@CeO₂ composite was developed by precipitation and pyrolysis at room temperature and combined with high performance liquid chromatography（HPLC-UV）for the determination of six pesticides in environmental water samples.Under optimized conditions,the method exhibited a wide linear range(0.026-200μg·L^-1),good linearity（R²>0.9988）,low detection limits(0.008-0.353μg·L^-1)and quantification limits(0.026-1.175μg·L^-1).Compared with commercial SPME fibers,the home-made fibers exhibited superior capture ability to pesticide,which was due to the strong cation-πinteraction,abundant adsorption sites,and hydrogen bonding between the coating and the target analyte.In addition,the hollow structure of the composite,the rare earth metal oxide CeO₂ on the material surface,and the silicone sealant（Ss）all play crucial roles in the extraction process.Chapter three:Hollow double-shell layer Co₃O₄/C（DSH-Co₃O₄/C）composites were prepared by etching ZIF-67 with tannic acid（TA）and coated on the surface of stainless steel wire as a coating material for SPME fibers with the help of physical adhesion method,and combined with high performance liquid chromatography for the detection of seven polycyclic aromatic hydrocarbons（PAHs）in environmental water samples.Under the optimal experimental conditions,the DSH-Co₃O₄/C-SPME-HPLC method showed a low detection limit,a wide linear range,and a better linear relationship.This is mainly attributed to the synergistic effect between the composition and structure of DSH-Co₃O₄/C composites.In composition,the remaining tannins and Co-O bind PAHs through hydrogen bonding;the cation-πinteraction between the metal oxide and PAHs.In structure,the DSH-Co₃O₄/C composite is also favorable for the extraction of PAHs based on its unique double-shell structure,abundant active sites,and voids between the shells.Compared with commercial SPME fibers,DSH-Co₃O₄/C showed efficient enrichment ability for PAHs.Chapter four:A novel hollow core-shell layer ZnO@Co₃O₄ composite was successfully prepared by a simple precipitation and pyrolysis method using metal organic framework（ZIF-8/ZIF-67）as precursors,which was used as an adsorbent for SPME fibers and combined with high performance liquid chromatography（HPLC-UV）for the determination of seven PAHs in environmental samples.The characterization results showed that the composite ZnO@Co₃O₄ has a hollow core-shell layer structure as well as uniform pores,and the unique hollow core-shell layer structure endowed the material with a large surface area and rapid extraction of PAHs.The extraction efficiency of the hollow core-shell layer ZnO@Co₃O₄ composite fiber coating was significantly better than several other fibers.Based on the structural analysis,the fast extraction was mainly attributed to the small,highly dispersed ZnO and Co₃O₄ particles in the framework,the hollow structure promoting molecular mass transfer,the synergistic effect between the oxides in the composites,and the interaction forces between the coated fibers and the target analytes.Under optimal conditions,the method exhibits low detection limits,good reproducibility,high accuracy and sensitivity,and so on.