Novel Boron Affinity Monolithic Columns And Magnetic Particles:Preparation And Applications

Objectives:Boron affinity materials(BAM)can selectively capture cis-dihydroxy-containing substances,including glycoproteins,nucleic acids,polysaccharides,glycosides,catechols and other substances,which have attracted extensive attention of scientists.However,traditional BAM can only achieve specific capture under alkaline conditions,while some cis-dihydroxy compounds are unstable and easy to be oxidized and degraded under alkaline conditions.Therefore,two novel BAMs were prepared for capturing cis-dihydroxy-containing substances selectively under weak acidity or moderate pH conditions.Method:1.In polyether ether ketone(PEEK)tube,a novel BAM-PEEK monolithic column was prepared as following:concentrated acid corrosion to increase the specific surface area of PEEK inner wall;polydopamine layer modified PEEK inner wall;epoxy group grafted on PEEK inner wall to provide reaction site for amino-epoxy ring opening polymerization;2-amino-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyridine was used as boric acid source and synthesized by ring opening polymerization without catalyst;under acidic conditions,opening pinacol borate ring,releasing boric acid group and obtaining BAM-PEEK monolithic column.The morphology of the BAM-PEEK monolithic column was observed by scanning electron microscopy(SEM),and the composition was analyzed by Fourier transform infrared(FT-IR)spectroscopy.BAM-PEEK monolithic column was used as solid-phase microextraction(SPME)material to capture cis-dihydroxy polyphenols in solution.SPME combined with high performance liquid chromatography(HPLC)was used to enrich,separate and detect polyphenols in water samples.2.A novel magnetic BAM nanoparticle was fabricated as following:Fe3O4 nanoparticles prepared by hydrothermal synthesis as magnetic core;SiO2 layer coated on magnetic core to protect magnetic core and provide reaction sites for silylation reaction;amino group modified by silylation reagent to provide reaction sites for amino-epoxy ring-opening polymerization;BAM containing boron-nitrogen coordination group was grafted outside magnetic core through ring-opening polymerization.The morphology of different magnetic particles was observed by transmission electron microscopy(TEM),the composition of magnetic particles was analyzed by FT-IR spectroscopy,and the proportion of degradable components was analyzed by thermogravimetric analysis(TGA)Magnetic BAM nanoparticles were used as magnetic solid phase extraction(MSPE)adsorbents to capture cis-dihydroxy-containing polyphenols in real samples.MSPE combined with high performance liquid chromatography-mass spectrometry(HPLC-MS)was used to enrich,separate and detect polyphenols in honeysuckle dewResults:1.SEM and FT-IR spectroscopy proved the successful synthesis of BAM-PEEK monolithic column.The inner wall of PEEK tube was inert,and its specific surface area could be increased by sulfuric acid corrosion.Although the polydopamine layer and the inner wall of PEEK tube were adsorbed by non-covalent bonds,they were closely bound,and the polydopamine layer could provide further modified active hydroxyl sites.Therefore,the BAM monolithic column covalently bonded to the dopamine layer,and the BAM monolithic column was closely bound to the inner wall of the PEEK tube.In addition,pyridine boric acid was heterocyclic boric acid,whose pKa value was less than 7,so that the prepared BAM-PEEK monolithic column could capture cis-dihydroxy-containing compounds under weak acidic conditions(pH=6.5).In the standard addition recovery experiment,the recovery and relative standard deviation(RSD)of five cis-dihydroxy-containing polyphenols by SPME combined with HPLC were 90.4%to 101.3%and 2.6%to 7.2%,respectively.2.Results of TEM,FT-IR and TGA showed that magnetic BAM nanoparticles were successfully prepared.The SiO2 layer could protect the magnetic nucleus,avoid acid corrosion and improve the reusability of magnetic BAM nanoparticles.In addition,in BAM,the "molecular group" of boron-nitrogen coordination,which was grafted outside the magnetic nucleus,had Wulff-type boric acid ligands-like structure,which could capture cis-dihydroxy-containing compounds at neutral pH.MSPE with magnetic BAM nanoparticles as adsorbent combined with HPLC-MS was used to detect 13 polyphenols in honeysuckle dew.In the standard addition recovery experiment,the recovery and RSD of 11 cis-dihydroxy-containing polyphenols were 84.6%to 100.9%and 2.8%to 8.2%,respectivelyConclusion:1.The BAM monolithic column was closely assembled with the inner wall of the PEEK tube through the polydopamine layer.BAM-PEEK monolithic column had high adsorption capacity for cis-dihydroxy compounds and could specifically capture cis-dihydroxy polyphenols in weak acidic environment.The permeability of BAM-PEEK monolithic column was good,but it was easy to be dussed during repeated use.2.Magnetic BAM nanoparticles could selectively adsorb cis-dihydroxy compounds under neutral pH conditions,and possessed strong adsorption capacity and good reusability.Magnetic BAM nanoparticles have wide application prospects,especially for selectively trapping compounds with cis-dihydroxy-containing structure which are unstable under alkaline conditions.