Preparation Of Magnetic Nanocomposite Materials And Its Application In The Detection Of Foods

Food safety is closely related to people's health.Food safety issues such as antibiotic residues and excessive additive content have received widespread attention from the society.Therefore,it is necessary to develop simple,sensitive,and rapid new analytical methods to detect antibiotic residues and additive content in foods.Due to the complex composition in foods and the low target analytes content,it is necessary to take an appropriate sample pretreatment to separate and concentrate the target analytes before determination.Magnetic solid phase extraction(MSPE)is a sample pretreatment technique that uses magnetic(composite)material as adsorbent to separate and enrich target analytes from sample solution.Compared with other sample pretreatment technologies,MSPE has the advantages of simple operation,high extraction efficiency,material reusability and environmental protection.In this paper,three different magnetic composite materials were prepared for the magnetic solid phase extraction of fluoroquinolones,sulfonamides and parabens in foods followed by high performance liquid chromatography detection.The main research contents are as follows:1.Fe₃O₄/MWCNTs/IL magnetic composite material was prepared and used as adsorbent to separate and enrich fluoroquinolones in foods coupled with high performance liquid chromatography for detection.The introduction of hydrophilic amine-terminated ionic liquid could improve the dispersibility and adsorption capacity of the adsorbent in aqueous solution.The material was characterized by transmission electron microscopy(TEM),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),Fourier infrared spectroscopy(FT-IR)and vibrating-sample magnetometer(VSM).Several factors affecting the extraction efficiency of MSPE were optimized,including the amount of adsorbent,extraction time,solution p H,eluent type and volume.Under the optimal extraction and detection conditions,the linear range of four fluoroquinolones were 4-1000 ng/m L,the limits of detection were 0.33-0.78ng/m L,and the spiked recoveries were between 85.2%-105.9%.Therefore,this method was suitable for detecting fluoroquinolones in foods.2.Fe₃O₄/MWCNTs-COOH/MoS₂magnetic composite material was prepared.The introduction of Mo S₂ not only effectively relieved the aggregation of Fe₃O₄ and MWCNTs-COOH,but also increased the surface area of the material,so that the material could provide more active adsorption sites.The prepared magnetic adsorbent had good stability and could be reused 8 times.Under the optimized experimental conditions,the linear range of four sulfonamides were 2-500 ng/m L,the limits of detection were 0.22-0.58 ng/m L,and the spiked recoveries were between 82.9%-94.2%.The result showed that the established method was simple and reliable,the detection limit was low,and the material could be reused many times.3.Fe₃O₄/N-RGO magnetic composite material was prepared.GO sheets were easy to agglomerate,resulting in the decrease of their adsorption capacity.Nitrogen doping could not only prevented the aggregation of GO sheets,but also made the wrinkle level of N-RGO increased.Undoubtedly,the reduction of aggregation degree and the increase of wrinkle increased the surface area of N-RGO and provided more adsorption sites,which was beneficial to improving the adsorption capacity of the material.At the same time,the introduction of nitrogen could improve the hydrophilicity of the material to make it fully contact with the solution,so that the target analytes could be adsorbed more quickly and completely.Under the optimal experimental conditions,the linear range of three parabens were 1-1000 ng/m L,the limits of detection were 0.18-0.21ng/m L,the spiked recoveries were between 91.2%-104.8%and the material could be reused 7 times.The results showed that the established method had the advantages of simple,rapid,low detection limit,and wide linear range.Therefore,this method was suitable for the extraction and detection of paraben preservatives in fruit juice.