| Nonsteroidal anti-inflammatory drugs(NSAIDs)are widely used in the treatment of human diseases due to their good anti-inflammatory and analgesic effects,but the unconsumed drug residues may be in various ways and forms exist in complex matrices such as water environment,and it is harmful to human body through enrichment and amplification in the living body.Therefore,the detection of residual NSAIDs in environmental water is particularly important.However,the matrix composition in environmental water is complex,and the concentration of the substance to be measured is extremely low.Therefore,only the effective sample preparation technology and the appropriate adsorbents can eliminate the influence of matrix and impurities and achieve the purpose of qualitative and quantitative analysis.Metal-organic frameworks(MOFs)are coordination polymers with certain cavities formed by metal ions as the coordination center and connected with rigid or semi-rigid organic bridged ligands.As a new type of porous material,it has the advantages of high specific surface area,large porosity,low cost,and structural adjustability.Therefore,it has broad application prospects in the fields of energy storage,catalysis,sensing,and selective adsorption separation.Especially in the field of sample preparation,it has obvious advantages.It can be used as a solid-phase microextraction(SPME)fiber coating,and selecting a suitable organic ligand can effectively achieve its selective extraction of the targets.Graphene Oxide(GO)is a graphene derivative obtained by oxidation of graphene.Because its structure contains a lot of oxygen-containing active groups,it has hydrophilicity and dispersibility,and can provide a large number of binding sites for the growth of MOFs,guide the growth of MOFs,and increase the extraction capacity of MOFs.Therefore,the MOFs@GO composite materials are expected to become supewuyrior SPME adsorbents.Based on the many advantages of MOFs and GO materials,this paper carried out a series of research work around the new SPME technology.Terephthalic acid,2-aminoterephthalic acid,and 2-methylimidazole are used as organic ligands,which are combined with different metal ions to obtain three kinds of MOFs,and three new SPME fiber coatings are prepared by compounding with GO.Combined with gas chromatography-flame ionization ditector(GC-FID),it is applied to the detection of NSAIDs in water samples.The specific research work are as follows:1.In view of the problems encountered in the extraction process of NSAIDs drugs,this article used zirconium tetrachloride(Zr Cl4),terephthalic acid as raw materials,and formic acid(HCOOH)as a p H adjuster to prepare large specific surface area,good chemical,and thermal stability Zr-MOF@GO octahedral configuration composite adsorbent.SPME fiber was made by coating Zr-MOF@GO on stainless steel wire substrate by binding method,and combined with non-derivative GC-FID detection technology to extract and analyze NSAIDs in environmental water samples.The physical and chemical properties of Zr-MOF@GO composites were studied using a series of characterization methods.The composite material can effectively form the coordination effect,?-? conjugation effect and H-bonding effect with two kinds of NSAIDs,realize the high-efficiency extraction of the targets,and obtain low detection limit and wide linear range.The non-derivatization extraction technique also highlights the advantages of the method,such as environmental friendliness and time saving.Compared with commercial PA and Zr-MOF-SPME fibers,Zr-MOF@GO-SPME fiber has better extraction capacity and extraction performance.Satisfactory results have also been obtained in practical applications.2.Based on the preliminary experiments,the-NH2 functional group was introduced into the ligand,and Zr-MOF-NH2@GO adsorbent material was successfully prepared by solvothermal method.Compared with Zr-MOF@GO,the crystal form of the composite material has not changed,but the specific surface area,thermal stability,and other properties have been significantly improved,which is very conducive to increasing its extraction capacity of the targets and increasing the service life of the fiber.More importantly,the extraction performance of this material is significantly better than Zr-MOF@GO,which may be due to the addition of-NH2 to enhance the H-bonding effect between the coating material and the targets,increase the conjugation system,especially increasing the p Ka value of MOFs material effectively improves the acid-base interaction between it and the targets.This also shows that the presence of-NH2 is very advantageous for the extraction of NSAIDs.3.Using zinc nitrate hexahydrate(Zn(NO3)2·6H2O),2-methylimidazole,and triethylamine as starting materials,a new ZIF-8@GO-SPME fiber was successfully prepared by one-step solvothermal method.Compared with the first two MOFs composite materials,the thermal stability of the material is stronger.However,due to the strong basicity of 2-methylimidazole,an irreversible effect is produced between the fiber and the targets,and a hysteresis effect occurs in the extraction.Therefore,the extraction results have low repeatability.This also shows that the extraction coating has a moderate alkalinity to effectively improve the extraction of targets. |
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