Porous Organic Polymers Applied To The Magnetic Solid Phase (Micro) Extraction For Separation And Enrichment Of Persistent Organic Pollutants

The analysis of environmental samples includes several processes,such as sampling,sample pretreatment,analysis,and data processing of experimental results.The study on sample pretreatment technology is very important in environmental analytical chemistry.It is a crucial step to improve the sensitivity and accuracy of the analysis and reduce the detection limit to pretreat the complex matrix samples so as to separate and enrich the target and interfering impurities and avoid the influence of the matrix.Some green,safe,and low-cost sample pretreatment technologies,such as solid-phase microextraction（SPME）,solid-phase extraction（SPE）,and magnetic solid-phase extraction（MSPE）have developed in recent years.The adsorption material with high selectivity and strong enrichment capacity is the current research hotspot,which is the core of sample pretreatment technology.New types of porous organic polymers,such as Covalent organic frameworks（COFs）and Conjugated microporous polymers（CMPs）,have the advantages of the green preparation process,diverse structures,and large specific surface area.At the same time,these materials also have uniform pore size distribution,adjustable pore size,easy post-modification,and stable physical and chemical properties,which make them play an important role in the field of sample pretreatment.In this paper,novel COFs and CMPs were synthesized and used as adsorption materials for MSPE and SPME combined with high performance liquid chromatography（HPLC）to separate and enrich persistent organic Pollutants（POPs）,including brominated flame retardants（BFRs）,hormones,and polycyclic aromatic hydrocarbons（PAHs）in environmental samples.It is mainly composed of four chapters:In Chapter 1,the hazards of persistent organic pollutants and the importance of sample pretreatment techniques in the environmental analysis are briefly introduced.The definition,classification,preparation methods,development history,and application fields of COFs and CMPs are reviewed in detail.In Chapter 2,a novel NiFe₂O₄-based magnetic COFs（NiFe₂O₄@COFs）was prepared by a simple room-temperature synthesis method and used as MSPE adsorbent for the determination of five BFRs in real water samples.The results showed that NiFe₂O₄@COFs has better adsorption performance than carbon nanotube materials to BFRs due to the hydrophobic interaction,π-πstacking of benzene ring and van der Waals force.In addition,adsorption thermodynamics and kinetic models showed that adsorption belonged to the Langmuir isotherm and quasi-second-order kinetic model,respectively.Using NiFe₂O₄@COFs combined with HPLC-UV method,it had a lower detection limit(0.03-1.95μg L^-1)and a wider linear range(0.1-1000μg L^-1),as well as better recovery rate（91.5-102%）and lower relative standard deviation（RSD）<0.3%under the optimized conditions.In Chapter 3,two triazine-based conjugated microporous polymers(Ta-CMPs_（DMF）and Ta-CMPs_（MB）)were produced using 2,4,6-tris（4-bromophenyl）-1,3,5-triazine（Ta-M）and terephthalic acid as monomers based on the Suzuki-Miyaura reaction,and then stainless steel wire was used as the substrate to prepare Ta-CMPs_（DMF）-SPME and Ta-CMPs_（MB）-SPME fibers by the sol-gel method.The adsorption properties of the two CMPs materials to hormones were compared.The results showed that Ta-CMPs_（DMF）had more excellent adsorption performance.Under the established Ta-CMPs_（DMF）-SPME-HPLC-UV method,seven hormones of different dairy products were analyzed.The LOD was 0.09-1.14μg L^-1 and the relative standard deviation（RSD）was1.8-5.5%,the correlation coefficient（R）>0.9991,and the linear range was 0.1-500μg L^-1.These results indicated that the established method was simple,high sensitive,and can quickly separate seven hormones in complex dairy products.In Chapter 4,A CMPs was synthesized by using 2,4,6-tris（4-bromophenyl）1,3,5-triazine（Ta-M）as the monomer based on the Yamamoto reaction,and then a SPME fiber was prepared by silicone glue on stainless steel wire.Combined with HPLC,a detection method（CMPs-SPME-HPLC-FLD）for fifteen PAHs in industrial wastewater was established.The experiment was carried out under the optimized conditions,the LOD was 0.001-1.65μg L^-1 and the relative standard deviation（RSD）was 0.5-6.7%,and the correlation coefficient（R）>0.9988.These results showed that the method was simple and efficient,which can realize the enrichment and analysis of trace PAHs in real samples.