Synthesis,Adsorption Properties And Analytical Applications Of Magnetic Nanocomposites

The technique of sample preparation plays an important role in analytical chemistry.Magnetic solid phase extraction（MSPE）has attracted much attention.Selective extraction of target analyte can be achieved by designing appropriate adsorbents,and rapid separation of adsorbents from sample solution can be achieved under the action of external magnetic field.MSPE has been widely used in the adsorption and extraction of target objects in complex matrix samples due to its advantages of good selectivity,strong anti-matrix interference ability,easy separation and enrichment of analytes,reusable adsorbents,and no need for a large amount of toxic organic solvents.In this thesis,three magnetic nano-adsorbents were prepared,combined with MSPE,the removal effection and adsorption properties of the adsorbent materials on synthetic pigments were investigated.Two new MSPE methods combined with liquid chromatography-mass spectrometry（UHPLC-MS/MS）and liquid chromatography（HPLC-UV）were established for the determination of tetracycline in water samples and synthetic pigments in drinks.This thesis is divided into 4 chapters as follows:Chapter 1:MSPE was briefly introduced.Carbon-based nanomaterials,metal-organic framework materials,molecularly imprinted polymers,ionic liquids and deep-eutectic solvents as well as their applications in analytical chemistry were summarized.The research ideas and contents of this thesis are expounded.Chapter 2:Fe₃O₄@PDA@ZIF-8 was prepared.Synthesis of ZIF-8,zinc acetate was used to replace zinc nitrate,and poly dimethyl diallyl ammonium chloride（PDDA）was added to enhance the adsorption efficiency of the material.The material was characterized by transmission electron microscope（TEM）,Fourier transform infrared spectrometer（FT-IR）,X-ray powder diffraction（XRD）,vibration sample magnetometer（VSM）and thermogravimetric analyzer（TGA）.The prepared material was used as adsorbent for MSPE and combined with UHPLC-MS/MS to detect four kinds of tetracycline in environmental water.The factors affecting extraction efficiency were investigated and optimized by single factor experiment and Central Composite Design（CCD）experiment in response surface method,and the optimal extraction conditions were determined by CCD experiment.Under the optimal conditions,the linear range of tetracycline was 0.1～50 ng/m L,R²>0.99,the recoveries were 76.92%～134.40%,the RSD（n=5）was≤8.06%,and the limit of detection was0.002～0.009 ng/m L.The proposed method has been successfully applied to the detection of four tetracyclines in environmental water.Chapter 3:Magnetic Graphene oxide（GO）/Chitosan（CS）was modified by Deep-eutectic solvents（DES）.The material was characterized by TEM,FT-IR,XRD,VSM and TGA.The removal efficiency of the material for the synthetic pigments bright blue and sunset yellow was investigated by using UV-VIS spectrophotometer.The Box-Behnken Design（BBD）using response surface method was used to investigate the factors affecting the removal efficiency,including the amount of adsorbents,p H of solution,extraction time,initial concentration of pigment and so on.It was found that the adsorption for bright blue was in accordance with Langmuir model,Dubinin Radushkevich（D-R）model and pseudo-second-order kinetic model,the adsorption for bright blue was physical natural adsorption,dominated by single layer adsorption,supplemented by multi-layer adsorption.The adsorption for Sunset Yellow was in accordance with the Freundlich model and the pseudo-second-order kinetic model,which indicated that the adsorption of the adsorbent for Sunset Yellow was spontaneous with faster adsorption speed.The adsorption performance of the adsorbent was better,showing larger adsorption capacity.Chapter 4:Graphene oxide/chitosan modified magnetic nanoparticles were used as MSPE adsorbent and combined with HPLC-UV for the determination of four kinds of synthetic pigments in beverages.The adsorbents were characterized by TEM,FT-IR,XRD,VSM and TGA,and the optimal extraction conditions were determined by single factor experiment and BBD design experiment.Under the optimal conditions,the linear ranges of the four analytes were 0.2～20μg/m L,the limits of detection were 0.13～0.37μg/m L,and the recoveries were 73.2%～108.9%with RSD（n=5）≤9.7%.The method has been successfully used for the detection of the synthetic pigments in three kinds of beverages.