【作者】 吕永琴；

【导师】 谭天伟；

【作者基本信息】 北京化工大学 ， 化学工程与技术， 2010， 博士

【摘要】 整体柱(monolithic column)又称为连续床(continuous bed),是由单体、交联剂、致孔剂以及引发剂的混合溶液在色谱柱内通过原位热引发或光引发聚合得到的整体、连续的柱体。相对于常规填充柱,具有制备简单、易于改性、渗透性好、柱压低、传质速度快和分离效率高等优点。本论文合成了聚甲基丙烯酸缩水甘油酯poly(GMA-co-EGDMA)和聚甲基丙烯酸异氰基乙酯poly(IEM-co-MMA-co-EGDMA)整体柱聚合物骨架材料,通过键合碳链(C8-C18)疏水配基、聚乙烯亚胺(PEI)阴离子交换配基和p-环糊精(p-CD)配基,对骨架材料进行功能化修饰。实现了对天然产物葛根黄酮粗提物、解脂假丝酵母脂肪酶和布洛芬手性药物的分离纯化。研究了整体柱的分离识别机理,并利用计算机模拟和核磁共振技术探讨了p-环糊精的超分子识别机理。鉴于分子印迹技术(Molecular imprinting technology, MIT)的专一识别性能和固相萃取技术(Solid phase extraction, SPE)的高效预富集能力,本论文还利用分子印迹固相萃取(Molecular imprinting solid phase extraction, MISPE)技术实现了对茶叶中残留的痕量有机磷农药乐果的快速富集与分离。优化了分子印迹聚合物(Molecularly imprinted polymers, MIPs)的合成条件,建立了等温吸附模型,研究了MISPE对目标分子的萃取效率,并利用计算机模拟构建模型,探讨了MIPs的特异选择识别性能。论文的主要工作如下：1、合成C8疏水配基键合聚甲基丙烯酸缩水甘油酯poly(GMA-co-EGDMA)整体柱,通过一步色谱,分离纯化葛根黄酮中的葛根素,研究葛根素、大豆甙和大豆苷元的分离识别机理。采用甲基丙烯酸缩水甘油酯(GMA)为功能单体,二甲基丙烯酸乙二醇酉(?)(EGDMA)为交联剂,GMA:EGDMA=8:2 (v/v),偶氮二异丁腈(AIBN)为引发剂,环己醇：十二醇=87：13(v/v)为致孔剂,直接以不锈钢柱管为模具,55℃自由基热聚合制备poly(GMA-co-EGDMA)整体柱聚合物骨架介质。在55℃下,利用50%(v/v)的正辛胺乙醇溶液修饰整体柱,合成C8疏水配基键合poly(GMA-co-EGDMA)整体柱。介质的孔隙率为60.8%,比表面积为17.8 m2·g-1,平均孔径为0.76μm。对葛根素的动态饱和吸附容量为15 mg·g-1,C8配基密度为2.3 mmol·g-1。从葛根黄酮粗提物中一步分离纯化得到葛根素的最佳流动相为1%(v%)的醋酸水溶液,等梯度洗脱。组分的定性由红外光谱分析(FTIR). LC-MS和NMR完成。样品在最大负载量11.6 mg每克干树脂下,一步色谱纯化得到的葛根素的收率和纯度分别为95%和69%(m%)。整体柱介质在多次使用后,利用100%的甲醇以0.5 mL·min-1的流速连续冲洗1 h,介质可以再生。结合混合溶剂下的色谱分析和计算机模拟研究葛根素、大豆甙和大豆苷元在C8疏水配基整体柱上的分离识别机理。通过改变色谱流动相中添加剂的浓度,证明了氢键作用和疏水作用的存在。底物在C8疏水配基整体柱上的保留符合氢键和疏水共存的混合作用模式。计算模拟结果表明,聚合物骨架和仲胺功能基团均与底物形成很强的氢键,氢键的受体为羰基和羧基,氢键的给体为羟基和仲胺基团。而C8配基与底物的芳香环有很强的疏水作用。通过分子动力学模拟计算底物和聚合物的结合能,可以成功地预测底物在整体柱上的保留行为。2、合成聚乙烯亚胺(PEI)高聚物阴离子交换配基键合poly(GMA-co-EGDMA)整体柱,通过一步色谱,分离纯化解脂假丝酵母脂肪酶(YlLip2)。确定整体柱的最佳合成条件,PEI的分子量30kDa, PEI的修饰浓度为10%(wt%),修饰温度为55℃,修饰时间为12 h。介质的孔隙率为65.6%,比表面积为5.8 m2.g-1,平均孔径为1.8μm。对BSA的动态吸附容量为45.2 mg·g-1,PEI配基密度(按N元素计算)为316.8μmol-g-。一步色谱分离纯化,从脂肪酶粗酶液中分离得到四种同工酶。非变性电泳分析显示,四种同工酶成分均一,分子量相当,约为38 kDa。层析的酶活力总收率为52.2%。四种同工酶的最大纯化倍数为4.5,酶活比活力最大值达到3860U·mg-1。圆二色(CD)光谱分析各组分的二级结构,酶结构显示了α/β水解酶折叠的特点,各组分间的二级特征结构的比例差异较小,无规则卷曲都约为30%。MALDI-TOF-MS表征同工酶A,B,C和D的分子量分别为36 648±36、37 839±33、38 236±31和38 795±96Da。3、合成p-环糊精配基键合poly(GMA-co-EGDMA)整体柱,手性拆分布洛芬对映体,研究p-CD与布洛芬超分子手性识别的包络机理。整体柱的最佳合成条件确定为：0.2 M Na2CO3(pH=12)为修饰反应溶剂,EDA-β-CD的修饰浓度为20%(wt%),修饰反应温度为60℃。介质的孔隙率为65.6%,比表面积为5.1 m2·g-1,平均孔径为1.1μm。β-CD配基的键合量为680μmol·g-1。确定手性拆分布洛芬的最佳流动相为甲醇/0.5%TEAA=30/70 (v/v) (pH=4),等梯度洗脱,对布洛芬对映体的分离度为2.0,选择性因子为6.1。分析级实验中,步分离纯化从葛根黄酮中得到葛根素,纯度为86%(m%),收率为79%(m%),分离效率略逊于C8疏水配基整体柱。布洛芬与β-CD超分子手性识别的包络机理是P-N作用机理,即形成包合物后,布洛芬的苯环完全被包络在β-CD的疏水内腔中,而布洛芬的羧基极性端位于β-CD的小口端。结合能、氢键相互作用和对映体分子的竞争性吸附结果表明,S-布洛芬与β-CD形成的包合物相对更稳定,色谱洗脱过程中S-布洛芬后洗脱出来,与色谱手性拆分的结果一致。相对于游离态的β-CD,键合后的β-CD对布洛芬对映体的选择性增加,手性拆分效率提高。4、合成新型的、具有高反应活性和通用性的聚甲基丙烯酸异氰基乙酯poly(IEM-co-MMA-co-EGDMA)整体柱骨架材料,键合碳链(C8-C18)疏水配基和β-环糊精配基,通过一步色谱,分离纯化葛根黄酮中的葛根素。甲基丙烯酸异氰基乙酯(IEM)为功能单体,甲基丙烯酸甲酯(MMA)为共聚单体,二甲基丙烯酸乙二醇酯(EGDMA)为交联剂,IEM:MMA:EGDMA=12:1:1(摩尔比),偶氮二异丁腈(AIBN)为引发剂,甲苯/正庚烷=0.5/1(v/v)为致孔剂。介质的孔隙率为57.6%,比表面积为11.5 m2·g-1,平均孔径为1.6μm。整体柱配基有效键合的定性分析由FTIR、固体核磁共振光谱和X光电子能谱(XPS)完成。由整体柱修饰反应的动力学曲线计算配基的饱和键合密度,C8配基键合密度高达2.33 mmo1·mL-1,异氰酸酯(N=C=O)基团的转化率为96.9%。5、色谱分析、计算机模拟和核磁共振技术结合研究葛根素、大豆甙和大豆苷元在p-环糊精配基整体柱上的分离识别机理。分子模拟结果显示,葛根素与p-CD的结合能最小,大豆苷元与p-CD的结合能最大。相对应在色谱分析中,葛根素在p-环糊精配基整体柱上的保留因子最小,大豆苷元的保留因子最大。p-CD与客体分子的结合能越大,表明p-CD与客体小分子的结合作用越大,形成的包合物相对越稳定,则在色谱分离中客体分子在固定相上的保留因子越大,在洗脱顺序中表现为后洗脱出来。通过模拟计算p-CD与客体分子的结合能的大小,可以成功地预测客体小分子在p-环糊精配基整体柱上的保留行为和洗脱顺序。空白整体柱骨架聚合物对三种底物没有选择性,配基p-CD起到主要作用。通过改变色谱流动相添加剂的浓度,证明了葛根素、大豆甙和大豆苷元在p-CD配基整体柱上的保留符合氢键和疏水作用共存的混合作用模式。由1H NMR和2D ROESYNMR证明,络合机理是葛根素的B环、C环和A环从p-CD的大口端进入环糊精的疏水内腔中,与p-CD形成1：1的络合物。NMR分析结果与分子模拟结果一致。6、分子印迹固相萃取技术快速富集分离茶叶中残留的痕量有机磷农药乐果。计算机模拟和色谱分析结合筛选分子印迹体系,最佳条件确定为：甲基丙烯酸丁酯(BMA)为功能单体,乙二醇二甲基丙烯酸酉(?)(EGDMA)为交联剂,四氢呋喃(THF)为致孔剂,模板分子、功能单体和交联剂的摩尔比为1：4：20,聚合温度为60℃,聚合时间为24 h,引发剂AIBN的用量为1%(相对于单体体积质量比)。MIPs对其模板分子乐果表现出很高的专一识别性能,其吸附等温线符合Langmuir模型。分子印迹固相萃取茶叶中的乐果的回收率可以达到99%,富集倍数为100倍,而空白聚合物对乐果的回收率仅有26%。分子动力学模拟构建模型,通过定义IFindicator和CFindicator两个参数,反映MIPs对乐果及其结构类似物的特异选择性能。TFindicator越大,MIPs对其选择性越好；CFindicator越大,结构类似物与乐果的结构差异越大,则MIPs对其选择性越差。吸附溶剂对聚合物和底物的作用力越小,溶剂之间的作用力越大,则有利于聚合物与底物的靠拢,聚合物与底物间的作用力越大。更多还原

【Abstract】 Monolithic column, which can be described as the integrated continuous porous separation media without the interparticle voids, is directly cast in tubes by free radical polymerization. Monoliths can be prepared in-situ by the copolymerization of functional monomers, cross-linkers and initiators in the presence of porogens. Compared with traditional packed columns, the major merits of monoliths are their easy preparation, low backpressure, high permeability, good mass transfer, high separation efficiency, and also that they are amenable to surface functionalization by suitable selection of monomers. In this thesis, poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) (poly(GMA-co-EGDMA)) and novel poly(isocyanatoethyl methacrylate-co-methyl methacrylate-co-ethylene glycol dimethacrylate) (poly(IEM-co-MMA-co-EGDMA)) monolithic matrix were synthesized. The poly(GMA-co-EGDMA) monolithic matrix can be modified by the ring-opening reaction of epoxy groups originated from GMA. The isocyanate groups on the surface of poly(IEM-co-MMA-co-EGDMA) monolithic matrix are highly reactive and versatile, which are amenable to functionalization by hydroxyl, amine and thiol groups with high efficiency. By chemical modification with a variety of modifiers, C8-C18 functionalized hydrophobic monoliths, polyethyleneimine (PEI) functionalized anion-exchange monoliths, andβ-cyclodextrin functionalized monoliths were prepared. Radix puerariae (R.P.) crude extract, ibuprofen optical isomer and YlLIP2 crude lipase were separated and purified. The preparative conditions for monoliths were first optimized, the separation and purification methods were further, established, and the molecular recognition mechanism was finally investigated. Theβ-cyclodextrin supramolecular recognition mechanism was studied by computational modeling and nuclear magnetic resonance (NMR).Thanks to the high specific selective recognition of molecular imprinting technology (MIT) and the highly efficient preconcentration ability of solid phase extraction (SPE), molecular imprinting solid phase extraction (MISPE) was used for the selective recognition and large enrichment of dimethoate from tea leaves. The preparative conditions of molecularly imprinted polymers (MIPs) were first optimized, the thermal adsorption isotherm was further established and the selective recognition properties of MIPs were finally investigated. The systematic studies were listed below:1. The C8 group functionalized poly(GMA-co-EGDMA) hydrophobic monolith was prepared for one-step rapid separation and purification of puerarin from Radix puerariae (a crude extract of the root of Pueraria lobata) by isocratic elution. The chromatographic recognition mechanism of puerarin was also investigated. The poly(GMA-co-EGDMA) monolithic matrix was prepared in-situ by free radical co-polymerisation of glycidyl methacrylate (GMA) and ethylene glycol dimethacrylate (EGDMA) with AIBN as initiator and cyclohexanol:dodecanol=87:13 (v/v) as porogen. The monolithic matrix was then functionalized by 50%(v/v) n-octylamine ethanol solution. The monolith shows a specific surface area of 11.5 m2·g-1, average pore size of 1.6μm, and a total porosity of 57.6%. A ligand density of 2.3 mmol·g-1 was obtained for the C8 functionalized monolith, which had the binding capacity of 15 mg·g-1 for puerarin. With a sample load of 11.6 mg crude R.P per gram dry polymer and with 1% acetic acid water solution as the optimum mobile phase, a puerarin purity of around 95%(m%) with a recovery of approximate 69%(m%) was achieved by proper peak cutting. The puerarin fraction was then characterized by FTIR, LC-MS and NMR. The column can be regenerated by cleaning with 100% methanol at the flow-rate of 0.5 mL·min-1 for one hour.The puerarin, daidzin and daidzein recognition mechanisms on C8 functionalized monolith were studied by computational modeling and chromatographic evaluation using a variety of solvent systems, and were shown to be based on a mixed-mode of hydrogen bonding and hydrophobic interaction. The hydrogen bonding arises from amino groups, carboxyl groups and hydroxyl groups. The functional alkane groups (C8) produces strong hydrophobic interaction with the phenolic groups of isoflavones. By analyzing the interaction energy between polymer and analytes, the retention factor of analytes on the monolith can be predicted.2. The polyethyleneimine (PEI) modified poly(GMA-co-EGDMA) monolith was prepared by functionalization with 10%(wt%) PEI 30 kDa aqueous solution at 55℃for 12 h, and then was applied for one-step purification of YlLIP2 isoforms from Candida sp.99-125. The monolith has a specific surface area of 5.8 m2·g-1, average pore size of 1.8μm, and a total porosity of 65.6%. A ligand density of 316.8μmol·g-1 was obtained for the PEI functionalized monolith, which had the binding capacity of 45.2 mg·g-1 for bovine serum albumin (BSA). Crude lipase was separated to four isoforms with the total enzyme activity recovery of 52.2%, the maximum purification fold of 4.5, and the specific enzyme activity of 3860 U·mg-1. As analyzed on non-denaturing PAGE, the four isoforms are homogenous and have the similar molecular mass of approximate 38 kDa. The isoforms were subjected to CD and their far UV spectra 190-240 nm was obtained. The distribution of secondary structure of isoforms are different from each other, the isoforms show characteristicα/βhydrolase fold with the content of random coils of 30%. The differences of the four isoforms were further confirmed by MALDI-TOF mass analysis, which indicated molecular masses of 36 648±36、37 839±33、38 236±31 and 38 795±96 Da for isoform A, isoform B, isoform C and isoform D, respectively.3. Theβ-cyclodextrin (β-CD) functionalized poly(GMA-co-EGDM A) monolith was prepared by thermal grafting of 20%(wt%) EDA-β-CD in 0.2 M Na2CO3 (pH=12) aqueous solution at 60℃for 12 h. The monolithic polymer exhibits a specific surface area of 5.1 m2·g-1, average pore size of 1.1μm, and a total porosity of 65.6%. The modified monolith shows aβ-CD ligand density of 680μmol·g-1. The resultant monolith was used for the chiral separation of ibuprofen optical isomer with methanol//0.5%TEAA=30/70 (v/v) (pH=4) as the mobile phase by isocratic elution. The resolution is 2.0 and the selectivity factor is 6.1.Theβ-CD/ibuprofen supramolecular enantioselective recognition mechanism was further investigated by computational modeling. The preferred penetration mode found corresponds to a geometry where the polar group (-COOH) of ibuprofen faces the narrower cavity of the (3-CD (P-N). Studies on the interaction energy, hydrogen bonding and competitive binding between S- and R-ibuprofen demonstrate that S-ibuprofen forms more stable inclusion complex withβ-CD, and consequently has a stronger retardation on the monolith. Compared with free-stateβ-CD, bondedβ-CD has better enantioselectivity for S- and R-ibuprofen.4. The copolymer poly(isocyanatoethyl methacrylate-co-methyl methacrylate-co-ethylene glycol dimethacrylate) (poly(IEM-co-MMA-c o-EGDMA)) was developed as a novel, facile, highly reactive and versatile monolithic matrix, which was amenable to surface functionalization with a variety of nucleophilic modifiers based on the reactive isocyanate groups, producing hydrophobic chromatography andβ-CD functionalized monoliths. The molar ratio of IEM, MMA and EGDMA was 12:1:1. A mixture of toluene and heptane with a volume ratio of 0.5 to 1 was used as the porogen. The monolith shows a specific surface area of 11.5 m2·g-1, average pore size of 1.6μm, and a total porosity of 57.6%. The success of the chemical modification of the monolithic matrix was confirmed by FTIR, solid state 13C NMR and XPS elemental analysis, showing the high ligand density of the modified monoliths. A ligand density of up to 2.33 mmol·mL-1 was obtained fo the 1-octanol modified monolith with an isocyanate group conversion of 96.9%, indicating the high efficiency of the modification reaction. The potential applications of the monoliths are demonstrated by the separation of a series of model compounds and Radix puerariae, and show promising results.5. Study on the recognition mechanism of puerarin, daidzin and daidzein onβ-CD functionalized monolith by chromatographic evaluation, computational modeling and NMR.β-CD exhibits the smallest interaction energy with puerarin, and the largest interaction energy with daidzein, which corresponds to the chromatographic elution result that the elution order is puerarin, daidzin and daidzein. Larger interaction energy means stronger interaction and more stable inclusion complex, and consequently longer retention time on the monolith. By simulating and analyzing the interaction energy betweenβ-CD and guest molecules, the retention property and elution order of guest molecules on theβ-CD functionalized monolith can be well predicted. Blank monolithic matrix has no selective recognition for puerarin, daidzin and daidzein. As a result, P-CD functionality plays a major role for the separation. The adsorption behaviour of puerarin onβ-CD functionalized monolith, has been investigated using a variety of solvent systems and shown to be based on a mixed-mode of hydrogen bonding and hydrophobic interaction.1H NMR and 2D ROESY NMR study shows that puerarin forms a tight 1:1 inclusion complex withβ-CD by penetrating its B, C and A rings into the hydrophobic cavity from the wider rim ofβ-CD, which is consistent with the simulation result.6. Selective recognition and large enrichment of trace dimethoate (organophosphorus pesticides, OPs) from tea leaves by molecular imprinting solid phase extraction (MISPE). The preparative conditions for dimethoate imprinting polymer were optimized by molecular dynamics modeling and chromatographic evaluation. Butyl methacrylate (BMA) was used as functional monomer, ethylene glycol dimethacrylate (EGDMA) was cross-linker, AIBN was initiator, and tetrahydrofuron (THF) was porogen. The molar ratio of template, BMA and EGDMA was 1:4:20. The polymerization was performed at 60℃for 24 h. MIP shows highly selective recognition property for the dimethoate template, and its adsorption isotherm is well presented by Langmuir model. Recoveries of dimethoate from tea samples by MIP and blank polymer are 99% and 26%, respectively, with a large enrichment factor of 100 for MIP. Two parameters, the imprinting factor indicator (IFindicator) and the competitive factor indicator (CFindicator), were defined according to the interaction energy difference to give an insight into the imprinting selectivity of MIPs to dimethoate versus other structurally related organophosphorus pesticides (OPs). A higher value of IFindicator means a better specificity and a higher value of CFindicator indicates a bigger structural difference between dimethoate and its analogues. A higher IFindicator value corresponds to a lower CFindicator value. By considering the two parameters, the selective recognition property of MIPs can be determined. The influences of the rebinding solvents on the adsorption properties of MIPs were also investigated. A good rebinding solvent should have a good solubility for the monomers and template, and less affinity with both template and polymer. A large self-association among solvent molecules could enhance the affinity between template and MIPs.更多还原