Preparation And Application Of Yolk-Shell Structure Magnetic Particles For Extraction

In recent years,magnetic solid phase extraction(MSPE)has been extensively studied in the field of separation science due to its high efficiency of extraction and rapid separation.As a new type of composite material,yolk-shell nano-particles have unique properties such as controllable size,high mass transfer efficiency,and more contact sites and larger surface area than common core-shell composites.It has great potential in catalysis,drug loading,storage and adsorption.In this paper,three kinds of super-paramagnetic yolk-shell magnetic particles were synthesized by hard template or self-template method.The materials were characterized by TEM,FT-IR,TGA and XRD.The materials were used as the adsorbents for pretreatment of polycyclic aromatic hydrocarbons(PAHs).After optimization of the extraction conditions,novel methods for the analysis of PAHs in tea were established combined with high performance liquid chromatography.The researches were as follows:(1)Nano-Fe₃O₄@void@polymethacrylic acid(PMAA)magnetic yolk-shell microspheres were prepared using surface polymerization and alkaline etching method.The materials were characterized by TEM,FT-IR,TGA and XRD and showed good adsorption properties for PAHs.The microparticles were characterized by FT-IR,TGA,TEM,XRD,and applied as adsorbents for the separation of PAHs.By optimizing the magnetic extraction conditions,an MSPE-HPLC method for the determination of PAHs in tea was established.The detection limit of the method for phenanthrene and anthracene were 4.0-6.0?g/kg,the intra-and inter-day RSDs were between 3.7-10.0%,and the spiked recoveries were between86.7-112.2%.(2)Porous magnetic carbon microspheres with yolk-shell structure was prepared by carbonization and etching technique.The precursor was prepared by one-pot method,and?-CD was modified on the surface of porous carbon to prepare the novel magnetic microspheres with host-guest recognition ability.The materials were characterized by FT-IR,TGA,TEM,XRD and N₂ sorption experiments.The micropartiocles were applied for PAHs MSPE.After optimizing the extraction conditions,an MSPE-HPLC method for the analysis of PAHs in tea samples was established.The method was volidated and applied to real samples.The detection limits of phenanthrene,fluoranthene and anthracene were 1.0-1.5?g/kg,the intra-and inter-day RSDs were in the ranges of 1.5-9.6%,and the recoveries were between93.8-104.5%.(3)ZIF-8 magnetic composite microparticles with yolk-shell structure were prepared using zinc oxide as the self-template.Zinc oxide was coated on the surface of nano-Fe₃O₄ by sol-gel method.ZIF-8 shell was formed using zinc ions and 2-methylimidazole.The micrioparticles were characterized and exhibited good adsorption property for PAHs.After optimizing MSPE conditions,an MSPE-HPLC method for the analysis of PAHs in tea samples was established,and the methodological investigation and application were carried out.The detection limits of the five PAHs were between 0.9-2.5?g/kg,the intra-and inter-day RSDs were between1.5-9.6%,and the spiked recoveries were between 93.8-104.5%.