Metal-Organic Framework Composites Coupled With GC-MS/MS For The Determination Of Persistent Organic Pollutants In Water And Food

Persistent organic pollutants?POPs?,an organic chemical pollutant which persist in environment,accumulate through the biological food chains?webs?and seriously endanger human health and the environment.They have long-term residual,bioaccumulative,semi-volatile and highly toxic properties.Recently,the detection and removal of POPs is a hot topic in the field of analytical chemistry and environmental.It is particularly important to develop accurate,rapid,and efficient methods for the analysis and determination of POPs in order to protect the environment and human health.Metal-Organic Frameworks?MOFs?materials are crystalline materials with adjustable pore sizes.They are formed by self-assembly of organic ligands and inorganic metal centers.They have many advantages such as porous,large specific surface area,various structural and functions so that they have been widely used in gas adsorption and separation,drug delivery,catalysis and sensing.Metal-organic framework composites are hybrid materials that combine traditional MOFs and other nanomaterials through physical or chemical interactions.They are improvements and innovations of MOF materials with more special functions and superior performance.In this study,three novel metal-organic framework composites were successfully synthesized by us.We combined these noval materials with different sample pretreatment methods and developed the analysis methods for the detection of trace level persistent organic pollutants like PCBs?PAHs and NPAHs in drinking water by GC-MS/MS.Consequently,a series of new methods for detection and analysis were developed,which were provided with accurate,convenient,efficient and environmentally friendly properties.The main research results of this paper are as follows:1.A novel metal-organic framework nanocomposite Fe₃O₄@SiO₂@UiO-66-PNIPAM was synthesized by solvothermal method.The material was characterized by scanning electron microscopy,transmission electron microscopy,X-ray powder diffraction,hydrogen spectrum NMR,fourier transform infrared spectroscopy and hysteresis loop measurements.Using the material as an adsorbent,a new method for the determination of trace PCBs in water samples using magnetic solid-phase extraction combined with GC-MS/MS was developed.The optimization experiment was designed by Box-Behnken design of Design Expert.The extraction time,extraction temperature and ionic strength were optimized by response surface method.After optimizing desorption solvent by single factor experiments,optimal experimental conditions were obtained.Under the optimal conditions,the method showed a good linear relationship with the linear range of 5-2500 ng L^-1,the detection limit was 0.41-1.15 ng L^-11 for 7 PCBs,and the spike recovery was in range of 81.1-108.5%,the RSD was less than 10%.The results showed that Fe₃O₄@SiO₂@UiO-66-PNIPAM has good applicability and broad prospect in the determination and analysis of PCBs in water as a magnetic solid phase extraction adsorbent.2.The MIL-101?Fe?was synthesized in teflon-sealed autoclave by solvothermal method and then the nanocomposite MIL-101@MON with core-shell structure was synthesized by the sonogashira coupling reaction under anhydrous and anaerobic conditions.The material was characterized by scanning electron microscopy,transmission electron microscopy,thermogravimetric analysis,X-ray powder diffraction and nitrogen adsorption-desorption isotherms.As a novel adsorption fiber coating,the material was fixed on the stainless steel needle by physical adhesive method,and the handmade SPME device was obtained.Using the material as an adsorbent,a new method for the determination of trace PAHs in water samples using solid-phase microextraction combined with GC-MS/MS was developed.The optimization experiment was designed by Box-Behnken design of Design Expert.Extraction temperature,extraction time,stirring rate and ionic strength were selected as significant factors and were optimized by response surface method.Under the optimal conditions,the enrichment factors of the coating for 16 PAHs were evaluated,the adsorption mechanism was discussed,and the commercial value of the coating was compared.Through method validation and actual sample analysis experiments,the proposed method showed high enrichment factors in range of 1215-3805,low detection limit as 0.02-0.30 ng L^-1,satisfactory recoveries from 71.2%to 109.2%with the RSD less than 10%.The preliminary application of the method in the determination of 16 PAHs in meat products has also achieved satisfactory results.3.Metal-organic framework nanoomposite In₂S₃@MIL-125?Ti?was prepared by solvothermal method in the teflon-sealed autoclave.Scanning electron microscopy,transmission electron microscopy,electron energy spectrum,X-ray powder diffraction,fourier transform infrared spectroscopy and nitrogen adsorption-desorption isotherms were used to characterize the materials.Using the material as an adsorbent,a new method of detecting 16NPAHs in water samples with dispersed solid phase extraction coupled with GC-MS/MS was developed.The optimization experiment was designed by Box-Behnken design of Design Expert.Extraction temperature,extraction time and ionic strength were selected as significant factors and were optimized by response surface method.After using single factor experiments to optimize the desorption solvents,the optimal experimental conditions were obtained.Under the conditions,the method validation and the actual sample analysis were performed.The linear range of 16 NPAHs was 10-5000 ng L^-1,the detection limit was 2.9-83ng L^-1,the recovery was in range of 70.6%-112%,and the RSD was less than 10%.By comparing with other methods,the superiority of the developed method was evaluated,and the adsorption mechanism of the material on 16 NPAHs was discussed.The results show that this method is suitable for analysis and detection of NPAHs in water and meat products,and it has broad prospects for development.