| Molecularly imprinted membranes(MIMs) are a novel type of separation membranes developed in the past few years.These membranes were designed and prepared combining the membrane separation with molecular imprinting technology.Compared with traditional membrane and molecular imprinted polymer,the MIM represents high selectivity for specifical substance and high imprint bind cavity hold rate,with a relative simple disposal procedure.Therefore MIM has attracted more interests in the development of functionalized membrane.Electrochemical sensor is one of the most effective and sensitive devices for determination of compounds,with possibility of easy-to-design,automation and miniaturization.Although the application of MIMs is maily focused on the fields of separation,it could find new application in other fields once integrate with electrochemical sensor.The purpose of this thesis is to apply the new type of molecular imprinting affinity separation technology to the separation,purification and related assay of effective ingredients from natural products.We prepared the molecular imprinted composite membrane and electrochemical sensor for resveratrol,which is an effective antioxidant compound found in grape and some Chinese traditional herbs.The details are as follows:1.RES imprinted composite membranes,with polyvinylidene fluoride microporous membrane as supporting membrane,were synthesized via in situ polymerization by thermal initiation,using acrylamide(AA) as functional monomer and ethyleneglycol dimethacrylate(EDMA) as the cross-linking agent.Scanning electron microscope(SEM) was used to visualize surface of membranes.The binding ability and permeation selectivity were studied for RES and its analogues,polydatin(POL),bisphel A(BPA) and 2-naphthol.The results indicated that the imprinted membranes demonstrated satisfactory recognition capacity and selectivity towards the template molecule.Rebinding of RES was much higher than that of structurally similar compounds.The saturated binding capacity of the imprinted composite membrane for RES is about 1.72μmol/g,nearly 3 times of that of non-imprinted polymer membrane.2-naphthol,which is smaller than the template molecule in size,transports through the imprinted composite membrane preferentially.The permeation amounts of BPA and POL are both less than that of RES, whether the molecular size is the same as or bigger than RES.RES transports through the imprinted membrane more quickly due to its complementary functional groups and shape with the imprinted sites on the imprinted composite membrane.The RES transfer rate increased for the imprinted composite membranes due to the larger amount of binding sites,comparing with the non-imprinted one.2.A voltammetric sensor for trans-Resveratrol has been prepared by a novel approach based on immobilisation of an imprinted polymer for trans-Resveratrol on functionalized Indium Tin Oxide Electrodes(ITO) and chemically irreversible oxidation of RES under the experimental conditions.γ-methacyloxypropyl trimethoxysilane (γ-MPS) was firstly self-assembled on to ITO electrode,then resveratrol-imprinted mixture was coated on the modified surface,with the benefits of preventing the sensor film falling off from electrode,effectively.Differential pulse voltammetry(DPV)was performed to extract resveratrol from the molecular imprinted polymer film and investigate its affinity and selectivity for template molecules.The oxidation peak current was directly proportional to the Concentrations of RES from 2.0×10-6 to 2.0×10-5 M,with a detectable limit down to 0.8μM.The modified molecular imprinted electrode demonstrated good sensitivity to and selectivity for RES. |
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