Study On New Methods For Small Molecule Compounds Detection Based On COFs/HOFs Porous Materials MALDI Mass Spectrometry

Matrix-assisted laser desorption time-of-flight mass spectrometry（MALDI-TOF MS）has the advantages of small sample amount,simple,fast,sensitive,good salt tolerance,wide measurement range and high-throughput and other features are widely used in the analysis and detection of peptides,nucleic acids,proteins and other macromolecules.However,there is still some limitation in the application of this popular technique for analysis of small molecular compounds.A critical problem is the suppression effects of the MALDI-TOF MS signal,which mainly comes from intrinsic matrix-related ions of conventional organic matrixes in the low-mass region and other analyte-ion interferences.Moreover,when applies to the detection of complex samples,high-abundance coexisting substances can also interfere with the detection of analytes.Therefore,to meet the urgent needs of detection of some small molecule compounds in environmental analysis,disease diagnosis,food safety and other aspects,aims to obtain the content and structure information of the target substance in the complex system,and to address the challenges of the stability of the matrix of MALDI mass spectrometry and the background interference of the complex system.In this paper,porous nanomatrix with enrichment function was synthesized as a mass spectrometric probe to construct LDI mass spectrometry technology assisted by porous nanomaterials,which were respectively applied to the enrichment of cisediol,perfluorinated sulfonic acid,paraquat and Chlormequat directly identified by mass spectrometry.The specific research contents are as follows:1.An imine-linked cation covalent organic framework（EB-COFs）,via the condensation by using trialdehyde phloroglucinol（Tp）and ethidium bromide（EB）as ligands,and the EB-COFs-LDI MS method was constructed.EB-COFs can enrich trace amounts of perfluorosulfonic acid from solution effectively and quickly through electrostatic interaction.Through the characterization and analysis of the material,EB-COFs has a porous structure,pore size:1.1 nm,high specific surface area:1104.7m²/g;Moreover,it has good thermal stability and strong near-ultraviolet light absorption.Applied to the detection of small molecule compounds,it exhibits the characteristics of high ionization efficiency and low background signal.This method has high sensitivity when applied to the enrichment and detection of perfluorosulfonic acid.The detection limits of perfluorobutane sulfonic acid,perfluorohexane sulfonic acid and perfluorooctane sulfonic acid are 0.001 ng/m L and 0.01 ng/m L,and 0.5ng/m L,respectively.In addition,the method has been successfully applied to the detection and analysis of actual samples such as lake water and human serum.2.Based on the specific affinity of boric acid and cis-diol,we presented a facile one-pot strategy for the synthesis of boric-acid functionalized covalent organic frameworks（B-COFs）by using 2,4,6-trihydroxy-1,3,5-benzenetrialdehyde,benzidine,and 4-aminophenyl-boronic acid as ligands.Compared with bare COFs,the B-COFs have similar crystallinity,specific surface,and well-developed pore structure.The surface area and average pore size of B-COFs were 238.0 m²/g and 1.2 nm,respectively.Using luteolin,riboflavin and catechol as the target analytes,we investigated the matrix ability,enrichment ability and experimental conditions of this method.The results showed that,compared with COFs,B-COFs showed the ability to specifically enrich cis-diols.After optimal the experimental conditions,the limits of detection for luteolin,riboflavin,and pyrocatechol were as low as fg/m L with B-COF enrichment.Moreover,the B-COFs were further employed and validated for specific enrichment and direct detection of target analytes with complex samples such as human serum,milk,and Capsicum samples,and a better recovery rate was obtained.Large surface area,numerous boric-acid active sites,and super stability make B-COFs with high enrichment capacity,high selectivity and sensitivity,satisfying reproducibility,and excellent applicability in MALDI-TOF MS assays.3.Here,we use 1,3,6,8-tetra（4-carboxybenzene）pyrene（H₄TBAPy）as raw material synthesis of hydrogen-bonded organic framework by a facile approach at room temperature,and the HOFs-LDI MS method was constructed.The structure and properties of HOFs-101 were characterized by powder diffraction,and ultraviolet-visible absorption spectroscopy.The results show that:HOFs-101 has high crystallinity,strong ultraviolet absorption in the near ultraviolet region,and good chemical and thermodynamic stability.Using two quaternary ammonium pesticides paraquat and chlormequat as model analytes,the experimental conditions for their extraction and detection by HOFs-LDI MS method were investigated and optimized,and the results showed that paraquat shows a good linear relationship（R²=0.9918）in the range of 0.008-0.3 ng/m L,and the detection limit is as low as 0.001 ng/m L;Chlormequat has a good linear relationship in the range of 0.3-60 ng/m L（R²=0.9926）,and the detection limit is 0.1 ng/m L.Furthermore,this method was applied to the analysis of two pesticides in tap water,lake water and soil samples,and a good recovery rate was obtained.These superior performances are mainly due to the abundant carboxyl functional groups of HOFs-101,which can effectively capture analytes from complex environments quickly through electrostatic interaction.