Preparation Of Ferulic Acid Surface-imprinted Material And Study Of Its Molecular Molecule Recognition Characteristic

Ferulic acid,also named4-hydroxy-3-methoxy cinnamic acid in chemistry, hasa highcontentin herbssuch as rhizomaligusticiwallichii, angelica. Ferulic acid has pharmacologicalaction of antioxidant and getting rid of free radicals、anticancer and antimutation,protection ofthe cardiovascular system, improving the immune systemand so on. At preseent,ferulic acidhas been made use of the pharmaceuticalstoiletry,health food andfood addition and so on,soitis greatly significant that the ferulic acid is extracted. The molecularly imprinted solid phaseextraction, abbreviated toMISPE,is an effective separation technique. For the polymerizabledouble bond that is contained in the molecular structure of FA, in this work, a kind offunctional macromolecules was grafted on the surfaces of micron-sized silica gel particles viamolecular design, and then themolecule imprinting of FA was effectively realized by using thenew surface imprinting technology of “pre-graft polymerizing and post-imprinting”,and threekind of FA molecule-imprinted material was prepared, which is a foundation of separation ofFA by the MISPE. The results have importantly scientific significance and potentialapplications in the separation of active constituentsfrom natural compounds.Firstly，the coupling agent γ-aminopropyltrimethoxysilane (AMPS) was bond onto thesurface of silica gel particles, and amino groups were introduced onto the surfaces of silica gelparticles, obtaining the modified particles AMPS-SiO2. A redox initiating system wasconstructed by the amino groups on the modified silica gel particles and ammoniumpersulphate in the solution, and the surface-initiated graft polymerization ofdimethylaminoethyl methacrylate (DMAEMA) was performed, resulting in the graftedparticles PDMAEMA/SiO2.Subsequently, the quaternization reaction of the tertiary groups onthe grafted particles was carried out withchlorethamin as regeant, and thequaternizationtransform of the grafted PDMAEMA was realized, resulting in the functionalgrafted particles QPDMAEMA/SiO2with cationic property. The functional grafted particles were fully characterized by several means, such as FTIR, SEM and Zeta potentialdetermination. The effects of temperature on the graft-polymerization reaction and thequaternizationtransform were mainly researched, and the conditions were optimized. Theadsorption property of the functional grafted particles PDMAEMA/SiO2andQPDMAEMA/SiO2for ferulic acid was examined. The experimental results show that thegraft-polymerization of DMAEMA on silica gel particles can be effectively realized by usingthe surface initiating system of-NH2/S2O82-, and the suitable temperature is35℃. Thequaternization reaction between chlorethamin and the tertiary amine groups on the graftedparticles can be smoothly carried out, and the appropriate temperature is60℃. At thistemperature the quaternization degree (QD) of the tertiary amine groups can reach82%. Byright of the synergism of strong electrostatic interaction and cation-πinteraction, the functionalgrafted particles PDMAEMA/SiO2and QPDMAEMA/SiO2possess very strong adsorption forferulic acid, the adsorption capacity gets up to0.75mmol/g and0.94mmol/g.The molecule imprinting towards the grafted PDMAEMA was performed with FA astemplate molecule and dibromohexane as crosslinking agent by using the novelsurface-molecular imprinting techniqueof “pre-graft polymerizing and post-imprinting”,established by our research group, and the FA molecule-imprinted materialMIP-PDMAEMA/SiO2was prepared. With Chlorogenic acid and Caffeic acid as contrastcompounds, both static and dynamic methods were adopted to study the recognitionproperty for FA and the separation ability towardsChlorogenic acid and Caffeic acid. Theexperiment results show that MIP-PDMAEMA/SiO2have obvious recognition selectivityand fine binding affinity for FA.The binding capacity gets up to0.74mmol/g. Relative to adepside, chlorogenic acid, whose molecular structure is similar to that of FA to a certaindegree, the coefficient of selectivity of MIP-PDMAEMA/SiO2particles reaches up to6.47,while relative to another phenolic acid, caffeic acid, whose molecular structure is very similarto that of FA, the coefficient of selectivity of MIP-QP/SiO2particles reaches2.75. Besides,MIP-PDMAEMA/SiO2has excellent elution property, with AceticAcid/Methanol(V:V=1:9)solution as eluent, the desorption ratio of FA reach99.6％in18BV. The functionalized macromolecule QPDMAEMA were made to be crosslinked withglutaraldehyde as crosslinker and with Shiff base reaction as crosslinking reaction, and themolecule imprinting of FA was achived, obtaining FA surface-imprinted particlesMIP-QPDMAEMA/SiO2, abbreviated to MIP-QP/SiO2. The imprinted particlesMIP-QP/SiO2were fully characterized. The molecular recognition property of MIP-QP/SiO2particles was maily investigated, and their property of separating FA with solid phaseextraction method was evaluated. The experimental results show that the imprinted particlesMIP-QP/SiO2have the excellent binding affinity and specific recognition selectivity. Thebinding capacity gets up to0.9mmol/g. Relative to chlorogenic acid,the coefficient ofselectivity of MIP-QP/SiO2particles reaches up to7.15, while relative toCaffeicacid., thecoefficient of selectivity of MIP-QP/SiO2particles reaches3.27. MIP-QP/SiO2has excellentelution property, with Acetic Acid/Methanol(V:V=1:9) solution as eluent, the desorptionratio of FA reach99.7％in20BV.With methacrylic acid (MAA) as functional monomer, hydrogen bonding as adsorptiondriving force,the molecule imprinting of FA,MIP-PMAA/SiO2, was effectively realized byusing thesurface imprinting technology of “pre-graft polymerizing and post-imprinting”.Firstly, via the coupling effect of γ-aminopropyltrimethoxysilane(AMPS),methacrylic acidwasgraft-polymerized onto the surface of silica gel particles,obtaining the grafted particlesPMAA/SiO2.Then,the molecular imprinting towards the grafted PMAA wasperformed withFA as template molecule and ethylene glycol diglycidyl ether（EGDE） as crosslinking agentby using the novel surface-molecular imprinting technique established by our researchgroup,and the FA molecule-imprinted material MIP-PMAA/SiO2was prepared.WithCA as acontrast compound,both static and dynamic methods were adopted to study the recognitionproperty for FA and the separation ability towardsCA.The experiment results show thatMIP-PMAA/SiO2have specific recognition selectivity and excellent binding affinity forFA,and its selectivity coefficient for FA with respect to CA reaches2.46.Besides,MIP-PMAA/SiO2has excellent elution property, with acetic acid/methanol(V:V=1:9) solution as eluent, the desorption ratio of FA reach99.8％in15BV.