Based On The Preparation Of Imine-Linked COFs Coated Stir Bar And Its Adsorption Properties Towards Endocrine Disrupting Chemicals

Sample pretreatment is an essential step in the analysis of complex samples,aiming to reduce matrix interference and enhance method sensitivity.Endocrine disrupting chemicals(EDCs)are widely present in food,drink,and other environments.Exposure to EDCs can lead to various endocrine-related diseases,including infertility,hyperactivity disorder,diabetes,obesity,as well as prostate,ovarian,and breast cancers.Studies have shown that EDCs are present in low concentrations in some actual samples,which are difficult to detect and can pose a higher risk of harm to organisms than short-term exposure to high doses of these chemicals.Thus,it is important to develop an efficient,simple,and fast sample pretreatment method.Stir bar sorptive extraction(SBSE),a popular sample pretreatment technique developed from solid-phase microextraction(SPME),was first reported by Eric Baltussen and his colleagues at the Belgian Chromatography Research Center in 1999.SBSE has advantages of simple operation,high recovery,and low solvent consumption,and has been widely applied in trace analysis of samples such as biological,environmental,spices,and food.Among them,a coating with high extraction efficiency and selectivity is a necessary condition to improve the performance of SBSE analysis methods.However,there are only three types of commercialized coatings,which cannot meet the demand for the analysis of multiple EDCs in actual samples.Therefore,the development of coatings with high extraction efficiency,long service life,and high selectivity is of great significance to the development and application of SBSE.The purpose of this study is to prepare a highly efficient covalent organic framework(COF)coating material suitable for trace analysis of endocrine disruptors,and to combine it with SBSE and high performance liquid chromatography(HPLC)to establish a COF-SBSE-HPLC-DAD technique for the analysis of endocrine disruptors in water and beverages.The main research contents of this work include:(1)Using the room temperature method,a covalent organic framework material(TAPB-TFP-COF)was prepared with 1,3,5-tris(4-aminophenyl)benzene(TAPB)and 1,3,5-triformylphloroglucinol(TFP)as monomers.The catalyst is an important factor affecting its synthesis,therefore its amount was examined to determine the final usage amount.The structure of the prepared TAPB-TFP-COF was characterized,revealing its rich porous structure,rough surface,large specific surface area,and good thermal stability,which is conducive to the adsorption of target compounds.Based on this,TAPB-TFP-COF was introduced onto a"dumbbell-shaped"glass stir bar using physical adsorption techniques to create a TAPB-TFP-COF coated stir bar,and a new TAPB-TFP-COF-SBSE-HPLC-DAD analysis method was established for detecting four target bisphenol compounds and investigating factors affecting their extraction and desorption.Under the optimal SBSE conditions,the analytical performance of this method was evaluated,the linear range for the four bisphenols was 1-200μg/L with linear correlation coefficients(R~2)of 0.9992-0.9998.According to the principle of three times signal-to-noise ratio(S/N=3),the detection limits of the four bisphenol compounds were calculated to be between 0.03-0.06μg/L.The RSDs of the method were between 1.23-8.23%(n=7,c=50μg/L),indicating good repeatability.The enrichment factors of the method for the four bisphenol compounds were 21-32 times(theoretical enrichment factor of 33 times).This method was successfully applied to detect the four bisphenol compounds in common beverages.(2)Spherical TAPB-DHT-COF materials were synthesized at room temperature by using 1,3,5-tris(4-aminophenyl)benzene(TAPB)and 2,5-dihexyloxy terephthalaldehyde(DHT)as monomers.The catalyst dosage was optimized and the structure was characterized.The results indicated that the prepared TAPB-DHT-COF material possessed a distinct porous structure,uniform particle size,good crystallinity,large specific surface area,and excellent thermal stability.It provided sufficient adsorption sites for target molecules,thereby enhancing adsorption performance.Based on this,TAPB-DHT-COF material was successfully applied in SBSE by physical adsorption technique to prepare a novel imine-based COFs coated stir bar,and a new TAPB-DHT-COF-SBSE-HPLC-DAD analysis method was developed.The conditions that affected the extraction and desorption of target estrogens by SBSE were optimized,and the analytical performance of the method was evaluated.The highest enrichment factor was up to 24-48 times(theoretical enrichment factor of 50 times).Under optimal conditions,the detection limit for target estrogens was 0.06-0.15μg/L,the linear range was 0.2-100μg/L,and the linear correlation coefficient(R~2)was 0.9967-0.9998.The relative standard deviations(RSDs)of the method were 1.80-4.25%(n=8,c=50μg/L).The established method was successfully applied to the analysis of four types of estrogens in actual water samples.