分子印迹整体柱在高效液相色谱和电色谱手性分离中的应用

在常规不锈钢色谱管中以甲基丙烯酸为功能单体,采用原位聚合法制备了(5S,11S)-特罗格尔碱(S-TB)的印迹整体柱。考察了流动相中添加不同量的醋酸和水对分离的影响,结合台阶梯度洗脱模式在S-TB整体柱上实现了对TB消旋体的快速分离。另外,以碱性单体2-二甲基乙基胺甲基丙烯酸酯(DAMA)为功能单体,在毛细管中采用原位聚合法制备了毛细管分子印迹整体柱,用于在毛细管电色谱（CEC）中对消旋体1,1′-联-2-萘酚(BNL)进行手性分离。结果表明,以AMA为功能单体可以制备其他酸性模板的分子印迹聚合物,从而扩大了分子印迹聚合物MIP）在CEC分离中的应用范围。     

以分子印迹聚合物为固定相手性拆分1,1′-联-2-萘酚及其衍生物

以(R)-(+)-1,1′-联-2-萘酚为模板分子,4-乙烯基吡啶为功能单体合成了分子印迹聚合物,将其作为高效液相色谱的固定相,研究其手性识别特性。对该固定相的手性拆分的色谱条件进行了优化。实验结果表明,合成的印迹聚合物对(R)-(+)-1,1′-联-2-萘酚具有较强的亲和力和特定的选择性,能有效拆分1,1′-联-2-萘酚对映体,分离因子最高达到12.25。通过优化色谱条件,该分子印迹聚合物还能对与1,1′-联-2-萘酚结构相似的衍生物5,6,7,8,5′,6′,7′,8′-八氢-1,1′-联-2-萘酚和1,1′-联萘-2-氨基-2′-酚进行手性拆分,分离因子分别达到1.51和2.40。     

Retentivity and enantioselectivity of uniformly-sized molecularly imprinted polymers for (S)-nilvadipine in aqueous and non-aqueous mobile phases.

Uniformly-sized molecularly imprinted polymers (MIPs) for (S)-nilvadipine have been prepared by a multi-step swelling and polymerization method using methacrylic acid or 4-vinylpyridine (4-VPY) as a functional monomer, ethylene glycol dimethacrylate (EDMA) as a cross-linker, and toluene, chloroform, cyclohexanol or phenylacetonitrile as a porogen. The chiral recognition abilities of the MIPs for nilvadipine were evaluated using aqueous and non-aqueous mobile phases. Among the MIPs, the (S)-nilvadipine-imprinted 4-VPY-co-EDMA polymers prepared using toluene as a porogen showed the highest recognition ability for nilvadipine in both aqueous and non-aqueous mobile phases. In addition to molecular shape recognition, hydrogen-bonding interactions of the NH proton of nilvadipine with a pyridyl group of the (S)-nilvadipine-imprinted 4-VPY-co-EDMA polymers could play an important role in the retention and chiral recognition of nilvadipine in aqueous and non-aqueous mobile phases. Furthermore, the MIP for (S)-nilvadipine gave the highest molecular recognition ability when a porogenic solvent during polymerization was used as the mobile phase modifier.     

Investigating the mechanisms of 17<Emphasis Type="Italic">β</Emphasis>-estradiol imprinting by computational prediction and spectroscopic analysis

Molecular dynamics simulations combined with spectroscopic analysis were applied to understand the nature of recognition in molecularly imprinted polymers (MIPs), and for optimizing the MIP formulation. The best monomers for synthesizing imprinted materials for 17β-estradiol (BE2) were selected by evaluating the strength of the template–monomer interaction derived from molecular dynamics simulations. A number of potential functional monomers for BE2 were screened for hydrogen-bonding strength in order to analyze template–monomer interactions favorable for synthesizing noncovalent MIPs, with the simulations revealing that methacrylic acid, 2-(diethylamino)ethyl methacrylate, and methacrylamide provided the highest binding affinity to BE2. These theoretical predictions agree with previously reported results on batch rebinding studies using the corresponding functional monomers for synthesizing a series of MIPs. Molecular analysis such as ¹H NMR was used for experimentally confirming the prevalent template–monomer interactions derived from the modeling results. Molecular dynamics simulations indicating monomer dimerization in the prepolymerization solution correlated with the nature of the porogenic solvent, which was confirmed by NMR studies on hydrogen-bonding interactions of methacrylic acid in different solvents. Furthermore, batch rebinding studies revealed that the specific functionalities of the monomers essential to rebinding are retained after polymerization, which proves that the application of computational methods for modeling the prepolymerization solution provides useful information for optimizing real MIP systems.     

Chiral separation of 1,1'-bi-2-naphthol and its analogue on molecular imprinting monolithic columns by HPLC

Two molecular imprinting polymer (MIP) monolithic columns with (S)-(-)-1,1'-bi-2-naphthol and (R)-(+)-5,5',6,6',7,7',8,8'-octahydro-1,1'-bi-2-naphthol as the templating molecules, respectively, have been prepared by in situ polymerization using 4-vinylpyridine and ethylene dimethacrylate as functional monomer and cross-linker, respectively. The columns with good flow-through properties were obtained by changing the molar ratio of the functional monomer and the template molecule. The effects of mobile-phase composition on separation of enantiomers were systematically investigated. The results indicate that hydrophobic interaction in aqueous solution and hydrogen-bonding interaction in ACN between the enantiomers and polymers could play important roles in the retention and resolution. The effects of chromatographic conditions, such as flow rate, column temperature, sample loading, on the enantioseparation were also studied. Further, these two MIP columns show a cross-reactivity.     

Chiral recognition and separation of beta2-amino acids using non-covalently molecularly imprinted polymers

Non-covalently molecularly imprinted polymers (MIPs) for beta2-amino acids were prepared for the first time. N-(2-chlorobenzyloxycarbonyl)-(R)-beta2-homophenylalanine (N-2-ClZ-(R)-beta2-HPhe) was imprinted with methacrylic acid (MAA) and/or 4-vinylpyridine (4-VPy) as the functional monomers, with ethylene glycol dimethacrylate (EDMA) as the cross-linker. The MIPs made with different ratios of MAA:4-VPy were studied in HPLC mode. The results show that MIPs made with 4-VPy yielded the best chiral separation factor (alpha= 1.86) for the template molecule. The importance for an efficient separation of pi-stacking interactions between the MIPs and the template molecule is demonstrated. Racemates of Z-alpha-amino acids and beta-amino acid analogues of the template were either not or poorly resolved by the MIPs, thus demonstrating the close three-dimensional complementarity of the MIPs' recognition sites with the template.     

Chiral separation of racemic mandelic acids by use of an ionic liquid-mediated imprinted monolith with a metal ion as self-assembly pivot

A new chiral stationary phase based on molecularly imprinted polymers (MIP) was prepared in ionic liquid by use of the metal pivot concept. Imprinted monoliths were synthesized by use of a mixture of R-mandelic acid (template), 4-vinylpyridine, ethylene glycol dimethacrylate, and several metal ions as pivot between the template and functional monomer. A ternary mixture of dimethyl sulfoxide–dimethylformamide–[BMIM]BF₄ containing metal ions was used as the porogenic system. Separation of the enantiomers of rac-mandelic acid was successfully achieved on the MIP thus obtained, with resolution of 1.87, whereas no enantiomer separation was observed on the imprinted monolithic column in the absence of metal ions. The effects of polymerization conditions, including the nature of the metal ion and the ratios of template to metal ions and template to functional monomer, on the chiral separation of mandelic acid were investigated. The results reveal that use of metal ions as a pivot, in combination with ionic liquid, is an effective method for preparation of a highly efficient MIP stationary phase for chiral separation.

Preparation and application of molecularly imprinted polymer for isolation of chicoric acid from Chicorium intybus L. medicinal plant

Molecularly imprinted polymer (MIP) was synthesized and applied for the extraction of chicoric acid from Chicory herb (Chicorium intybus L.). A computational study was developed to find a suitable template to functional monomer molar ratio for MIP preparations. The molar ratio was chosen based on the comparison of the binding energy of the complexes between the template and functional monomers. Based on the computational results, eight different polymers were prepared using chicoric acid as the template. The MIPs were synthesized in a non-covalent approach via thermal free-radical polymerization, using two different polymerization methods, bulk and suspension. Batch rebinding experiments were performed to evaluate the binding properties of the imprinted polymers. The best results were obtained with a MIP prepared using bulk polymerization with 4-vinylpyridine (4-VP) as the functional monomer and ethylene glycol dimethacrylate (EGDMA) as the crosslinker with a molar ratio of 1:4:20. The best MIP showed selective binding ability toward chicoric acid in the presence of the template’s structural analogues, caffeic acid, caftaric acid and chlorogenic acid.     

功能单体对分子烙印手性固定相手性拆分能力的影响

系统考察了功能单体对非共价分子烙印手性固定相手性分离能力的影响,发现在非共价分子烙印手性固定相的制备中,功能单体与烙印分子之间存在着匹配性。丙烯酰胺可以与氨基酸衍生物的酰胺基团形成较强的氢键作用,碱性功能单体2-乙烯基吡啶则与其羧基形成较离子作用,两者的协同作用使复合功能单体丙烯酰胺+2-乙烯基吡啶对于氨基酸衍生物具有良好的烙印效果。竞争溶剂乙酸对样品与分子固定相间的非共价作用力有较大的影响,增加流动相中的竞争溶剂乙酸的含量,将减弱分子手性固定相与样品的酰胺键和羧基的氢键及离子作用,导致对样品的容量因子、手性选择性α及分离度f/g的减小。     

N-苯甲氧羰基-L-色氨酸为模板的单分散分子印迹聚合物微粒的制备

采用两步溶胀与悬浮聚合联用方法,以2-乙烯基吡啶(2-VP)为功能单体,二乙二醇二丙烯酸酯(DEGDA)为交联剂,成功制备出以N-苯甲氧羰基-L-色氨酸(N-Cbz-L-Trp)为模板的单分散分子印迹聚合物,并用扫描电镜、氮气吸附、拉曼光谱、高效液相色谱、热失重分析等测试手段进行表征.结果表明,分子印迹聚合物的平均粒径为6.3μm,多分散系数为1.03.拉曼光谱显示聚合物反应完全,模板分子洗脱充分.高效液相色谱表征显示,分子印迹聚合物在很短的色谱柱中即可实现对印迹分子对映异构体的基线分离.     

Sulfonamide imprinted polymers using co-functional monomers

Molecular imprinted polymers (MIPs) prepared using combination of acrylamide (ACM) and 4-vinylpyridine (4-Vpy) as co-functional monomers exhibited efficient recognition properties in both organic and aqueous media as HPLC stationary phase. The results indicate that amide and pyridine groups in functional monomers formed strong hydrogen-bonding interaction with the template molecule, and specific recognition sites were created within the polymer matrix during the imprinting process. When sulfamethoxazole (SMO) was used as template, a MIP prepared in a polar organic solvent (acetonitrile) using the combination of ACM and 4-Vpy showed better recognition of template than the polymer prepared in the same solvent using the combination of acidic monomer (methacrylic acid) and basic monomer 4-Vpy. On the contrary, when sulfamethazine (SMZ) was used as template, a MIP prepared using the combination of methacrylic acid (MAA) and 4-Vpy showed better recognition of template than the polymer prepared using the combination of ACM and 4-Vpy. Our results indicate that in organic media the degree of retention of the sample molecules on the imprinted polymers was controlled by the hydrogen-bonding interaction between the sample molecules and the polymer, while in aqueous media it was determined to a considerable extent by hydrophobic interactions. In both media the shape, size and the electronic structure of the template molecule were all-important factors in the recognition process.     

Chiral Resolution of Racemic 4-Phenyl(benzyl)-2-Oxazolidone by Use of Molecularly Imprinted Polymers

Polymers imprinted with (S)-4-phenyl-2-oxazolidone and (S)-4-benzyl-2-oxazolidone have been prepared by non-covalent imprinting. A combinational procedure was used to optimize the functional monomer and crosslinker. A copolymer of methacrylic acid and divinylbenzene resulted in the best chiral recognition. The ratio of template to functional monomer and solvent in the pre-polymerization mixture were also optimized. The imprinted polymers were used as stationary phases in high-performance liquid chromatography. The MIPs were more selective when prepared using a less polar solvent, except for toluene. Effective separations of the enantiomers of racemic 4-phenyl-2-oxazolidone and 4-benzyl-2-oxazolidone were achieved by use of acetonitrile as mobile phase; no cross-selectivity was observed. Interactions between functional monomers and template were investigated by ¹H NMR spectroscopy. The results suggest that hydrogen-bonding between the functional monomer and the template and π–π stacking interaction between the cross-linker and the template may contribute to chiral recognition.     

复合碱性功能单体分子烙印手性固定相

采用丙烯酰胺+2-乙烯基吡啶的复合碱性功能单体体系制备了氨基酸衍生物分子烙印高效液相色谱手性固定相。在优化了功能单体与烙印分子的比例条件下对于烙印分子及其结构相似的对映体具有良好的手性分离能力。考察了烙印分子的化学基团对手性分离的影响,发现氢键作用力和较强的离子作用力在手性分离过程中均有贡献。     

Synthesis and Evaluation of Molecularly Imprinted Polymers as Sorbents for Selective Extraction of Coumarins

Coumarin, 7-hydroxycoumarin and dicoumarol molecularly imprinted polymers (MIP) were synthesized by bulk polymerization. Methacrylic acid and 4-vinylpyridine were tested as functional monomers and methanol, ethanol, acetonitrile, toluene and chloroform were tested as porogens. The binding capabilities of the imprinted polymers were assessed by equilibrium binding analysis. Highest binding capacity was obtained for MIP prepared for the template 7-hydroxycoumarin synthesized in methacrylic acid as functional monomer, chloroform as porogen and methanol/water as analyte solvent. Scanning electron microscopy analysis documented its appropriate morphology. ATR-FTIR spectra confirmed successful polymerization of MIP. Coumarin structural analogues were employed to evaluate the polymer selectivity and it was found that polymer prepared for 7-hydroxycoumarin was selective for its template molecule. Kinetic studies showed relatively fast adsorption of analytes to MIPs (1 h). Rebinding properties of MIPs were evaluated by adsorption isotherms. The calculated data fitted well with experimental data showing that Freundlich isotherm is suitable for modelling the adsorption of tested coumarins on prepared MIPs. Applicability of polymer prepared for 7-hydroxycoumarin was tested for the selective extraction of coumarins from the sample of chicory.     

Molecularly imprinted polymers: a new tool for separation of steroid isomers

Molecularly imprinted polymers hold great promise for the separation of chiral compounds. A non-covalent approach to the synthesis of MIPs relies on the presence of specific and non-specific interactions, which lead to the formation of a molecular imprint. The structural differences between 17-alpha-estradiol and 17-beta-estradiol are too small to permit their efficient separation on a MIP prepared with beta-estradiol as a template. Molecular modeling revealed the presence of only one hydrogen bond that differentiates the two isomers.     

Molecularly Imprinted Polymers with Mandelic Acid as Template

In this report, molecularly imprinted polymers (MIPs) with racemic and L-mandelic acid as the templates were synthesized. Several structural analogues were chosen to study the selectivity of the MIPs prepared using 4-vinylpyridine (4-VP) as the monomer (MIP_4-VP). At the same time, the chromatographic behaviors of the MIP using acrylamide (AA) as the monomer (MIP_AA) in two different mobile phases, acetonitrile and hexane/ethyl acetate (1:1, v/v), were investigated and the separation of the enantiomers was tried. The results indicated that MIP_4-VP had great retention with a template comparable to other analogues. However, no difference in the k′ values of the enantiomers was observed, as the interaction between the polymer and the enantiomers was mainly dependent on the acidity, which showed no difference. The MIP_AA showed a more obvious imprinting effect for the template in hexane/ethyl acetate (1:1, v/v) than in acetonitrile. But the separation of the enantiomers was not achieved even in the less polar solvent, though there was an obvious difference between the retention time of L-MA and D-MA on the L-MA imprinted polymer.     

利用分子烙印手性固定相串联柱同时拆分两对对映体

采用复合功能单体制备了苯甲氧羰基－Ｌ－丝氨酸（Ｎ－Ｃｂｚ－Ｌ－Ｓｅｒ）和苯甲氧羰基－Ｌ－丙氨酸（Ｎ－Ｃｂｚ－Ｌ－Ａｌａ）烙印的分子烙印手性固定相。采用柱串联的方法,一次进样手性分离了苯甲氧羰基－ＤＬ－丝氨酸（Ｎ－Ｃｂｚ－ＤＬ－Ｓｅｒ）和苯甲氧羰基－ＤＬ－丙氨酸（Ｎ－Ｃｂｚ－ＤＬ－Ａｌａ）两对对映体,显示了分子烙印手性固定相在多对对映体同时手性分离的发展潜力。     

Investigation of enantiomer recognition of molecularly imprinted polymeric monoliths in pressurized capillary electrochromatography screening the amino acids and their derivatives

Molecularly imprinted monolithic columns were prepared for chiral separation of tyrosine and its amino acid derivatives by in situ therm-initiated copolymerization of methacrylic acid, 4-vinylpyridine and ethylene glycol dimethacrylate. The enantiomers were rapidly separated on monolithic columns in less than 10 min by pressurized capillary electrochromatography (pCEC). The influences of several parameters such as the content of cross-linking monomer on the composition of the pre-polymerization mixture were systematically investigated. The influence of the pCEC conditions including the composition of the mobile phase was also optimized to obtain the good enantioseparation. It was found that in addition to molecularly imprinted recognition, chromatographic retention and electrophoretic migration play important roles in the retention and chiral recognition of molecularly imprinted polymer (MIP) columns. The cross-selectivity for similar amino acids and its derivatives were systematical investigated for understanding the recognition mechanism on the MIP monolithic columns. The results indicated that molecularly imprinted polymer recognizes the template molecule by its molecular shape defined binding cavity.     

Preparation,evaluation and characterization of quercetin-molecularly imprinted polymer for preconcentration and clean-up of catechins

Molecularly imprinted polymer (MIP) for solid extraction and preconcentration of catechins have been successfully prepared by a thermal polymerization method using quercetin as template, 4-vinylpyridine as functional monomer and ethylene glycol dimethacrylate as crosslinker. A solution mixture of acetone and acetonitrile was used as porogen. Systematic investigations of the influence of monomer, cross-linker, porogen, as well as polymerization conditions on the properties of the MIPs were carried out. The quercetin MIPs were evaluated according to their selective recognition properties for quercetin, structurally related compounds (catechin, epigallocatechin gallate and epicatechin) and a unrelated compound of similar molecular size (α-tocopherol). Good binding was observed for quercetin, catechin and epigallocatechin gallate with an optimized MIP in a solid phase extraction system. Adsorption and kinetic characteristics were evaluated for catechins which indicated that the synthesized polymer had high adsorption capacity and contained homogeneous binding sites. Chemical and morphological characterization of the MIP was investigated by FTIR, SEM and BET, which confirmed a high degree of polymerization. Finally, the MIP was successfully applied to the clean-up and preconcentration of catechins from several natural samples.     

硅胶表面亮菌甲素分子印迹聚合物的制备及其性能研究

采用光接枝印迹方法,在硅胶微球表面制备了以亮菌甲素为模板分子、2-乙烯基吡啶为功能单体的分子印迹聚合物,采用荧光法优选了功能单体及比例,进一步用荧光法对印迹聚合物的吸附特性和印迹效率进行评价.结果表明.该印迹聚合物对模板分子具有特异吸附性能,印迹效率为48.6%.