| Molecular imprinting is a kind of technology that the synthesized polymers,molecularly imprinted polymers (MIPs), are tailor-made materials with highselectivity for a target molecule. This selectivity arises from the synthetic procedurefollowed to prepare the MIPs, in which a template molecule is linked, by covalentbonds or non-covalent force, to suitable monomer containing functional groups. Thislink is responsible for the subsequent specific binding sites imparted to the MIPs.MIPs have proven their potential as synthetic receptors in numerous applicationsranging from purification of racemic mixtures, to chemical sensing and catalyticcontrol of complex chemical reactions, especially in the preparative and analyticalseparation of target molecule from the complex samples. The inherent advantagescompared to biochemical/biological recognition systems include robustness, storageendurance and lower costs.In this paper, vinblastine (VLB) was chosen as the template molecule while MAAas the function monomer, EDMA as the cross-linker and toluene as the porogen tosynthesize VLB-imprinted polymer which had the high affinity to VLB and could beused as the separation materials to extract and purify VLB from Chinese herbs. Inthe process of preparation, the extraction of template molecule was further studied.FTIR and SEM of VLB-MIP were established to characterize the polymers. The absorption, separation, capacity and endurance of VLB-MIP were evaluated bysolid-phase extraction (SPE) of which the synthesized VLB-MIP was used as thesorbents. The main parameters influenced the procedure of VLB-MIP, such as themole of MAA and EDMA and the porogen were optimized by the uniform designtest.The absorptions of the vinyl and carboxyl groups were interesting in FTIR. Theresonance of vinyl group may allow an estimate of the extent of unreacted doublebonds and therefore indicate the extent of the polymerization and that of carboxylgroup may give information of the hydrogen bond state. A clear band at 1638 cm-1 isattributed to=C-H bending and the broad band at 3200-3750 cm-1 to the carboxylOH stretch. The SEM images of the VLB-MIP and NIP exhibited appreciabledifferences in the morphology of the polymers. The surface of the VLB-MIP wasmore porous and with small cavities. And the NIP had a more uniform, smooth shapethan the VLB-MIP, which had an irregular, rough morphology. The regular structureof the NIP was due to the fact that no specific binding sites had been created for thetarget molecule. The holes and cavities in the VLB-MIP were probably caused by thestructure of VLB. When the template VLB was loaded on the VLB-MIP SPE and thespecific binding was observed between VLB and VLB-MIP, and the specificadsorption rate was 83.59%. On the contrary, the adsorption between VLB and NIPwas nonspecific, so as the adsorption between VCR, an analogue of VLB, andVLB-MIP, VCR and NIP. The VLB-MIP could separate VLB from the extract ofCantharanthus roseus successfully by optimizing the separation condition, theseparation factor was 0.89. The capacity of VLB-MIP was 0.622mg/g with tolueneas the solvent, which was higher than that of with chloroform and methanol as thesolvent. The VLB-MIP still exhibited good separation capability when used as thesorbents of SPE to separate VLB from the extract of Cantharanthus roseus for five times. In the procedure of extracting template from the polymers, methanol-glacialacetic acid (6:4,v/v) was determined as the extracting solvent and 98.03ï¼…of VLBcould be removed, while the amount of solvent and the extracting were bothdecreased. The parameters of synthesizing VLB-MIP were optimized by uniformdesign test. The adsorption rate of MIP9 synthesized under the optimal condition,VLB:MAA:EDMA=1:8.98:33.48 and acetonitrile as the porogen, amounted to 92.7ï¼….The separation factor of the MIP10, prepared under the another optimal condition,VLB:MAA:EDMA=1:8.98:48.97 and toluene as the porogen, was 0.93.The VLB-MIP had good stability, ideal capacity and exhibited high affinity to thetemplate VLB. It used as the sorbents of SPE and could be separated VLB from theextract of Cantharanthus roseus successfully. As a kind of new separating materials,MIP will be full of potential in selective separation active components from Chineseherbs. |
