Preparation Of Estrogen Imprinted Magnetic Particles With Yolk-shell Structure For Extraction Applicaton

Sample pretreatment is a key step in the analysis of food,environmental and biological samples,and an effective measure to improve the selectivity,sensitivity,and accuracy of analytical method.Among them,due to its simple operation,fast separation,and small amount of organic solvents,magnetic dispersive solid-phase extraction(MDSPE)is a widely used and fast-developing new method.And two key factors affecting the separation and enrichment efficiency of magnetic dispersion solid phase extraction are the composition and physical morphology of the coating materials.Based on the selective recognition of molecularly imprinted polymers,molecularly imprinted magnetic particles with superparamagnetic yolk shell structure and double yolk shell structure were synthesized by selective etching method,characterized by TEM,TGA,N₂adsorption and desorption experiments and magnetic determination,respectively.The composite magnetic materials were applied for extraction and sensitive detection of 17?-estradiol(E2)in milk powder.After optimizing the MSPE conditions,MDSPE-HPLC methods were established for high accuracy and sensitivity determination of E2 in milk samples.(1)A three-layer structure magnetic microspheres with Fe₃O₄core,inorganic silica layer and external molecularly imprinted layer were formed by surface-polymerize using Fe₃O₄as the core,E2 as the template,BTESE as a cross-linking agent,APTES as a functional monomer and CTAB as a pore-forming agent.Then,the mesoporous yolk shell structure magnetic polymers(MYS-MMIPs)were synthesized by selective etching to remove the inorganic silica interlayer.Transmission electron microscopy combined with N₂adsorption and desorption experiments confirmed the mesoporous yolk shell structure of the materials.Thermogravimetric analysis and cycling experiments showed the good thermal and adsorption stability of the composite magnetic materials.Magnetic properties experiment confirmed the good magnetic response of the materials.The binding experiment indicated that the materials had selective recognition and high binding capacity(39.24 mg/g)for E2.The obtained polymers were applied as the adsorbents for the magnetic dispersion solid phase extraction(MDSPE)of E2.After optimizing the MDSPE conditions,an MDSPE-HPLC method was developed for the determination of E2 in milk powder.The linear range of the method for E2 in milk was 1?300?g/kg,the detection limit was 0.33?g/kg,the recoveries were in the range of 88.3%?102.4%,and the relative standard deviations(RSDs)were less than5.5%.It could be seen that the MDSPE-HPLC method had an high accuracy and sensitivity for the analysis of E2 in milk samples,which meets the requirement of quantitative analysis.(2)A five-layer structure magnetic microspheres with Fe₃O₄core,inorganic silicalayer,molecularly imprinted layer,inorganic silica and molecularly imprinted layer were synthesized by surface-polymerize using Fe₃O₄as a core,E2 as the template,BTESE as a cross-linking agent,APTES as a functional monomer and CTAB as a pore-forming agent.Then,the double yolk shell structure magnetic polymers(DYS-MMIPs)were synthesized by selective etching to remove the double interlayers of inorganic silica.DYS-MMIPs were characterized by TEM,TGA,BJH,VSM recycling and adsorption experiments.The results showed that the DYS-MMIPs with mesoporous yolk shell structure had good thermal stability,adsorption stability and selectivity,and magnetic response.The adsorption capacity for E2 reached 65.17mg/g,which was 60%higher than that of MYS-MMIPs.These results showed that DYS-MMIPs had more specific surface area and adsorption capacity compared with MYS-MMIPs,and retained the pefect adsorption selectivity,stability,and magnetic properties,which was more suitable for MDSPE.After optimizing the MDSPE conditions,an MDSPE-HPLC method was developed for the determination of E2 in milk powder.The linear range of this method was 0.30?300?g/kg,the detection limit was 0.1?g/kg,the recoveries were in the range of 92.5%?101.1%,and the relative standard deviations(RSDs)were less than 6.1%.It could be concluded that the MDSPE-HPLC method has higher sensitivity for E2 analysis in milk samples than MYS-MMIPs-MDSPE-HPLC,which meets the requirements for quantitative analysis of E2 in milk powder samples.