| The separation and purification of active components of traditional Chinese medicine is one of the key technologies in the modernization of traditional Chinese medicine.The glycosides and alkaloids of traditional Chinese medicine are the important source of active molecules and leading compounds for the new drugs development of traditional Chinese medicine because of their diverse structures and pharmacological activities.The development of the separation and purification of glycosides and alkaloids from traditional Chinese medicine is a hot research subject in the field of separation and analysis.Molecularly imprinted technology is a kind of high molecular polymer technology which has specific recognition ability for specific template molecules.Molecular imprinted polymers(MIPs)prepared by this technology have the characteristics of strong predetermination,high specific recognition ability,acid and alkali resistance,stable performance and reusability.It has been widely used in the field of solid phase extraction and chromatography.Currently,The molecularly imprinted solid phase extraction adsorbent materials are mainly prepared by bulk polymerization.The prepared polymer material is amorphous particles,resulting in imprinting sites embedded in the polymer,making elution difficult,slow mass transfer rate,low utilization of imprinting recognition sites,and poor water phase environment selectivity.Aiming at the shortcomings of traditional molecularly imprinted polymers,this paper uses traditional Chinese medicine glycoside compounds(naringin,ginsenoside Rbl)and alkaloid molecules(quinine)as imprinting models to study and prepare three-dimensionally ordered macroporous molecularly imprinted microspheres and surface boric acid affinity molecularly imprinted microspheres based on organic polymer microspheres and inorganic/organic composite microspheres as a carrier.These MIPs not only have the advantages of fast adsorption kinetics,high adsorption capacity and easy accessibility for template molecules to the imprinting recognition sites,but also have good application value in the fields of chromatography and solid phase extraction due to their uniform spherical shape.The specific research content of this paper mainly includes the following three parts.The fast part:The polymer microspheres with good monodispersity and abundant boric acid functional groups was prepared by suspension polymerization by using 4-vinylphenylboronic acid(VPBA)and methacrylate(MMA)as functional monomers,and ethylene glycol dimethacrylate(EDMA)as crosslinking agent,respectively.Using the prepared polymer microspheres as the carrier,the naringin template molecule was combined with the boronic acid functional groups on the surface of the microspheres,and then the naringin surface boronic acid affinity molecularly imprinted microspheres(SBMIMs)were successfully prepared by co-deposition polymerization coating of dopamine and polyethyleneimine.The prepared materials were characterized by optical microscopy,laser confocal microscopy,scanning electron microscopy,infrared spectroscopy,and nitrogen adsorption/desorption measurements.The results show that the dopamine and polyethyleneimine co-deposited film has been successfully coated on the surface of the polymer microspheres,and the surface imprinted microspheres have a stable structure and high mechanical properties.The adsorption capacity and imprinting factor of SBMIMs are affected by the concentration of polymerized monomer,polymerization time,and adsorption solvent.When the imprinting molecule concentration is 2.0 mg mL-1,the polymerization time is 36 h,and the adsorption solvent is methanol/phosphate buffer solution(20 mM,pH8.7)(3/7,v/v),the adsorption capacity of SBMIMs for naringin reaches the maximum,and its imprinting factor is greater than 4.0.The kinetic adsorption experiment,which conforms to the second-order kinetic adsorption model,shows that SBMIMs has faster adsorption kinetics for naringin,indicating that the adsorption behavior is controlled by a chemical adsorption process.Selective experiments on different substrates show that SBMIMs have a highly specific recognition of naringin,and its binding partition coefficient to naringin is significantly higher than other substrates.The results of solid-phase extraction application research show that the SBMIMs as the adsorption material of the molecularly imprinted solid-phase extraction column can effectively extract,separate and purify the naringin in the crude extract of Citri Grandis Exocarpuim,and the elution amounts of naringin is 273.15 μg g-1,the total recovery of elution solution can reach 50.52%.The second part:A kind of urea-formaldehyde/SiO2 composite microspheres(UF-SiO2)with good monodispersity and a particle size range of 5-10 μm was prepared by using the Stober method and the polymerization-induced colloidal agglomeration method based on tetraethyl orthosilicate(TEOS)as the silicon source,urea and formaldehyde as polymerization monomers,respectively.The composite microspheres are coated by co-deposition polymerization of dopamine and polyethyleneimine,and abundant amino groups are introduced on the surface of the microspheres to prepare amino-functionalized urea-formaldehyde/SiO2 composite microspheres(NH2@UF-SiO2).The boric acid functionalized polymeric composite microspheres were prepared via condensation reaction of the of amino groups of NH2@UF-SiO2 and 4-carboxylic acid phenylboronic acid.Then ginsenoside Rbl surface boric acid affinity molecularly imprinted composite microspheres(SBMICMs)were prepared by the Co-deposition coating of dopamine and polyethyleneimine polymerization after the templates molecule ginsenoside Rbl was reacted with boric acid of the microspheres.The structure and morphology of SBMICMs were characterized by optical microscopy,laser confocal microscopy,scanning electron microscopy,infrared spectroscopy,and nitrogen adsorption/desorption measurements.The adsorption performance of SBMICMs was evaluated by thermodynamics,kinetic adsorption and different substrate selectivity experiments.The research results show that SBMICMs has good adsorption performance and specific selection performance for ginsenoside Rb1.The application results of solid-phase extraction show that the SBMICMs as the adsorption material of the molecularly imprinted solid-phase extraction column have a good separation and purification effect for the ginsenoside components,which can remove most of the impurities in the crude extract of Panax quiquefolium L..The ginsenoside Rbl,ginsenoside Rg2 and ginsenoside Rd were extracted and separated,and the elution recovery adsorption rate was as high as 84.25%,82.52%and 90.07%,respectively.The third part:Monodisperse silica nanoparticles were prepared by stober method,and silica colloidal crystal template microspheres were prepared by the evaporation-induced self-assembly method.Using quinine as the imprinting model,a novel three-dimensional ordered macroporous quinine molecularly imprinted microspheres(3DMIMs)was developed by combining the colloidal crystal template method and molecular imprinting technology.The structure and morphology of 3DMIMs were characterized by optical microscopy,scanning electron microscopy,thermogravimetric analysis,nitrogen adsorption measurement,and small-angle X-ray scattering,and their adsorption behavior was evaluated.The research results show that 3DMIMs have three-dimensionally long-range ordered and interconnected macropore array,and the polymer inner wall has a nanometer-level thickness with abundant mesoporous structure.Compared with traditional bulk imprinted polymers,3DMIMs has faster adsorption kinetics and higher adsorption capacity,and its maximum adsorption capacity(47.45 μmol g-1)is about 21.0%higher than traditional bulk polymers(BMIPs).The kinetic adsorption process conforms to the second-order kinetic model,and the binding rate constant(k2)of 3DMIMs is 1.15×10-2 gμmol-1 min-1,which is about 4.4 times that of BMIPs.Solid-phase extraction studies have shown that 3DMIMs,as solid-phase extraction materials,can effectively separate quinine and its diastereoisomer quinidine directly from Cinchona bark crude extract. |
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