Preparation,Characterization And Application Of Two Magnetic Adsorbents

Magnetic solid phase extraction has received widespread attention due to its advantages such as simplicity,rapidness,high efficiency,and environmental friendliness.Magnetic adsorbent is the key to magnetic solid phase extraction,so the development of new magnetic adsorbent with good magnetic response,good dispersion,high extraction efficiency and good chemical stability is the focus of analysis and research.In this paper,two magnetic adsorbents were prepared and characterized by various characterization methods.The as-prepared two magnetic adsorbents were applied to magnetic solid phase extraction for the analysis of target analytes at low levels in food and biological samples combined with high performance liquid chromatography.The main research contents of this paper are as follows:（1）Graphene oxide nanoribbons has some disadvantages such as high oxidation degree,lessπ-conjugated system,poor adsorption performance and difficulty in separation,which limit its application in sample pretreatment.To solve this problem,magnetic reduced graphene oxide nanoribbons（Fe₃O₄@RGONRs）adsorbent was prepared in this study.First,graphene oxide nanoribbons were obtained by longitudinal unzipping of multi-walled carbon nanotubes.Then,reduced graphene oxide nanoribbons was obtained by using sodium hydroxide as reducing agent.Finally,Fe₃O₄@RGONRs was synthesized by solvothermal method using ferric chloride hexahydrate as iron source.The Fe₃O₄@RGONRs was characterized by transmission electron microscopy,X-ray diffraction,Fourier transform infrared spectroscopy,vibrating sample magnetometer,nitrogen adsorption-desorption isotherm and Zeta potential analysis.The results showed that Fe₃O₄@RGONRs adsorbent had the advantages of good crystal structure,strong magnetic response,large specific surface area,richπ-conjugated system,good adsorption performance and so on.Combined with high performance liquid chromatography,Fe₃O₄@RGONRs magnetic solid phase extraction method was established for the determination of bisphenol endocrine disruptors in carbonated beverages.This research expands the application of graphene nanoribbons and their derivatives in sample pretreatment.（2）Appropriate modification of Fe₃O₄ nanoparticles and zeolite imidazolate framework-8 to improve their efficient enrichment of low level analytes is a problem that needs to be solved in this study.Polyacrylic acid（PAA）is a typical anionic polyelectrolyte,which not only has good dispersibility and biocompatibility,but also has abundant carboxyl groups.In this work,magnetic zeolite imidazolate framework-8（Fe₃O₄@PAA@ZIF-8）adsorbent with a core-shell structure was prepared by using PAA as the linking agent.The introduction of PAA can not only improve the dispersion of Fe₃O₄ nanoparticles,but also immobilize Zn²⁺with the carboxyl group on the surface through coordination bonds.And then,Zn²⁺and 2-methylimidazole can form a ZIF-8shell on Fe₃O₄@PAA surface by self-assembly.Fe₃O₄@PAA@ZIF-8 was characterized by transmission electron microscopy,X-ray diffraction,Fourier transform infrared spectroscopy,vibrating sample magnetometer,Zeta potential analysis and specific surface area measurement.The results showed that Fe₃O₄@PAA@ZIF-8 adsorbent had the advantages of good dispersion,good crystal structure,good magnetic response,large specific surface area and high extraction performance.Combined with high performance liquid chromatography,Fe₃O₄@PAA@ZIF-8 magnetic solid phase extraction method for the determination of brucine and strychnine in urine samples was established.