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.     

苯甲酸分子印迹聚合物的制备及其吸附性能

以苯甲酸为模板分子,4-乙烯基吡啶为功能单体,乙二醇二甲基丙烯酸酯为交联剂,采用本体聚合法制备了高选择性识别的分子印迹聚合物。利用合成的聚合物作为吸附剂填充制备气体浓缩针装置,并用于挥发性有机化合物(VOCs)的气相色谱分析。实验结果表明:60℃下恒温聚合反应6h,模板分子、功能单体、交联剂的物质量比为1∶4∶20,预聚合时间为3h,溶剂为乙腈,模板分子为苯甲酸时,合成的分子印迹聚合物对苯系物的吸附量最大。     

分子印迹β-环糊精聚合物选择性识别水中的双酚A

以双酚A为模板分子, β-环糊精为功能单体, 六亚甲基二异氰酸酯为交联剂, 二甲基亚砜为溶剂, 采用沉淀聚合法合成了分子印迹β-环糊精聚合物. 用傅里叶变换红外光谱仪、 扫描电子显微镜对聚合物的结构进行表征. 从选择性、 吸附容量、 结合特性对吸附剂的性能进行了评价. 底物类似物的机会均等与机会不均等竞争吸附实验证明了β-CD-MIPs对底物的结合容量远大于对类似物的结合容量. 用热力学参数对实验数据进行拟合, 发现β-CD-MIPs对BPA的吸附为自发的放热过程, 温度低对吸附有利.     

Surface imprinted polymers for oil denitrification with the combination of computational simulation and multi‐template molecular imprinting

Multi‐template molecular imprinting technique was employed for the theoretical study about industrial oil denitrification. Prior to the preparation of multi‐template molecularly imprinted polymers (MT‐MIPs), density functional theory was used for simulating the imprinted pre‐assembly systems composed of template (aniline, indole, or 3‐methylinndole) and monomer [methacrylic acid, acrylamide (AM), and 4‐vinylpyridine]. MT‐MIPs were synthesized as surface MIPs simply and successively by seeded emulsion polymerization or two‐stage precipitation polymerization. The experimental results were consistent with the simulative results, which demonstrated that AM was more suitable monomer together. In addition, seeded emulsion polymerization synthesized MT‐MIPs with better performance compared with two‐stage precipitation polymerization. The adsorption kinetics and adsorption isotherm of MT‐MIP prepared with AM using seeded emulsion polymerization were fitted with different models. The fitting results indicated that pseudo‐second‐order kinetics model and Freundlich isotherm model were suitable for describing the adsorption process of AM seeded emulsion polymerization. This study will provide a certain guidance and theoretical basis for introducing the combination of multi‐template molecular imprinting technique and computational simulation into the field of industrial denitrification. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis of Chlorogenic Acid Imprinted Chromatographic Packing by Surface-initiated Atom Transfer Radical Polymerization and Its Application

A novel chromatographic packing of chlorogenic acid（CGA） molecularly imprinted polymer（MIP） based on the 5.0 ~tm silica was prepared by surface initiated atom transfer radical polymerization（SI-ATRP） with 4-vinylpyridine（4-VP） as functional monomer, ethyl glycol dimethacrylate（EDMA） as cross-linker in the mixture of methanol and water（7：3, volume ratio） under mild reaction conditions. The characteristics of CGA MIP were investi- gated by elemental analysis, thermogravimetric analysis（TGA）, Fourier transform infrared spectrometry（FTIR） and atomic force microscopy（AFM）. The effects of some chromatographic conditions such as mobile phase composition and temperature on the retention time were investigated. The adsorption capacity of the stationary phase for com- pounds was determined by frontal chromatographic technique. The results show that Freundlich isotherm fits the ex- perimental adsorption isotherm data better than Langmuir model does. The relatively high heterogeneity index values regressed with the Freundlich isotherm suggest the formation of fairly homogeneous MIP. Thermodynamic data（AAH and AAS） obtained by van＇t Hoff plots reveal an entropy-controlled separation. The CGA MIP column was shown to be successful for the separation and purification of chlorogenic acid from the extract of Honeysuckle.     

反乌头酸分子印迹聚合物微球的制备及其分子识别功能

以乙腈为分散剂,采用沉淀聚合法合成了反乌头酸分子印迹聚合物微球。研究了合成反应条件对聚合物形貌的影响,发现聚合前主客体氢键络合物和功能单体氢键低聚体是控制微球形成及其粒径大小的关键因素。通过振荡吸附法对聚合物的结合特性进行了评价,发现印迹聚合物微球对模板分子的识别选择性优于块状印迹聚合物和非印迹聚合物。     

三元交联剂分子烙印手性固定相

采用２－乙烯基吡啶＋丙烯酰胺复合功能单体,以三甲氧基丙烷三甲基丙烯酸酯为三元交联剂制备了苯甲氧羰基－Ｌ－色氨酸烙印手性固定相,并与二元交联剂烙印相同氨基酸衍生物的情况进行了对比,发现三元交联剂在较小的用量下就可使分子烙印聚合物达到足够的交联度,实现烙印分子对映体的基线分离。     

Synthesis and characterization of a novel quercetin magnetic molecularly imprinted polymer via reversible addition fragmentation chain transfer strategy

Molecularly imprinted polymer (MIP) will be modified on the surface of the core-shell structure silica magnetic nanoparticles, during which quercetin is used as a template molecule, acrylamide as a functional monomer, azo-bisisobutyronitrile as an initiator and ethylene glycol dimethacrylate as a cross-linker, to synthesize highly efficient and selective quercetin magnetic molecularly imprinted nanoparticles via Reversible Addition-Fragmentation chain Transfer (RAFT) polymerization. FT-IR and X-ray diffraction (XRD) patterns are used to monitor the reaction and show the characteristic groups of each reaction step. Compared with the conventional bulk polymerization (2.7029 mg/g), the adsorption test showed that the MMIP by RAFT activity controlled polymerization had better absorption capacity for quercetin which the saturated adsorption amount was 4.8471 mg/g. Kinetic studies indicate that pseudo first order model is suitable to describe the adsorption mechanism. Thermodynamics experiment revealed that Langmuir model was more applied for explains the adsorption of quercetin onto magnetic molecularly imprinted polymer.     

硅胶表面苯并噻吩分子印迹聚合物的分子识别与吸附性能

选用γ-氨丙基三乙氧基硅烷和α-甲基丙烯酸修饰的硅胶作为载体,以甲基丙烯酸为功能单体,二甲基丙烯酸乙二醇酯为交联剂,苯并噻吩为模板分子,合成一种具有选择性识别苯并噻吩分子的印迹聚合物。采用红外光谱、元素分析及N2吸附对其结构进行了表征,以模拟汽油通过静态吸附对其吸附性能进行了研究。结果表明,在硅胶载体表面成功地嫁接了多孔的分子印迹聚合物薄层。印迹聚合物对苯并噻吩具有良好的识别性能,对苯并噻吩的吸附动力学满足Langergren准一级反应动力学方程,吸附过程属于单分子层吸附。符合Langmuir吸附模型印迹聚合物对苯并噻吩的平衡吸附容量达57.4×10-3,而非印迹聚合物的吸附容量为33.1×10-3。印迹聚合物在经过多次再生后其吸附容量基本不变,从而为在汽油深度脱硫中有效脱除噻吩类硫化物提供了一种新技术途径。     

双酚F分子印迹聚合物的制备及其对水相中双酚F吸附性能的研究

以双酚F(4,4′-BPF)为模板分子,α-甲基丙烯酸(MAA)为功能单体,乙二醇二甲基丙烯酸酯(EGDMA)为交联剂,偶氮二异丁腈(AIBN)为引发剂,采用沉淀聚合法合成4,4′-BPF分子印迹聚合物(MIPs)。运用傅里叶红外(FT-IR)光谱对产物的结构进行表征,并对其吸附等温线、吸附动力学、吸附热力学及选择性识别性能进行研究。结果表明:MIPs对水相中4,4′-BPF具有特异性吸附,最大吸附容量为82.8 mg/g;Freundlich模型拟合吸附等温线的相关系数R2=0.995;热力学参数ΔG、ΔS、ΔH均小于0,表明此吸附过程是自发进行的、熵减的、放热的。     

HPLC determination of sulfamethazine in milk using surface-imprinted silica synthesized with iniferter technique

A new method for the synthesis of sulfamethazine-imprinted polymer on the surface of silica via quasi-living radical polymerization and the application of the resulting polymer in determination of the SMZ in milk is developed. In the synthesis, initiator-transfer agent-terminator (iniferter) was immobilized on the silica surface using chemical reagents with good availability. The imprinting polymerization was initialized by the silica-supported iniferter under the UV radiation. The molecularly imprinted polymer (MIP) layer grafted on the silica surface was constructed by using sulfamethazine (SMZ) as the template, methacrylic acid (MAA) as the functional monomer and ethylene dimethacrylate (EDMA) as cross-linker. The resulting MIP-silica has good selectivity for SMZ and high column efficiency in the HPLC analysis. The result demonstrated that the SMZ-imprinted polymer was grafted on the silica surface successfully. Under the optimized HPLC condition, the MIP-silica has been used for the determination of SMZ in milk. The method was linear over the concentration range of 0.1-50 microgmL(-1) with correlation coefficient R>0.999. The detection limit for SMZ was 25 ngmL(-1). The recoveries were above 78% at the spiked concentration of 0.024, 0.24 and 0.48 microgmL(-1).     

1-氨基乙内酰脲分子印迹聚合物的制备和吸附性能研究

以1-氨基乙内酰脲(AHD)为模板分子,α-甲基丙烯酸(MAA)为功能单体,乙二醇二甲基丙烯酸酯(EDMA)为交联剂,采用本体聚合方法合成了分子印迹聚合物(M IP),考察了模板分子与功能单体不同比例下制备的M IP对模板分子的吸附性能。通过Scatchard分析,表明该印迹聚合物上存在一类等价的吸附位点,其结合位点的离解常数KD=4.33mmol/L。     

A novel polymerization of ultrathin sensitive imprinted film on surface plasmon resonance sensor

A new surface-initiated polymerization based on pasting the initiator on a sensor chip surface was applied to prepare a malachite green (MG) imprinted ultrathin film on a surface plasmon resonance (SPR) sensor. First, the initiator (2,2-azoisobutyronitrile) was pasted on the gold surface using polyvinyl chloride (PVC). The initiator-covered gold chip was then soaked in a pre-polymerization solution prepared by dissolving methacrylic acid (functional monomer), ethylene glycol dimethacrylate (cross-linker), and MG (template) in DMSO in a weighing bottle. Finally, the weighing bottle was placed in a vacuum oven and thermal-initiated polymerization was conducted at 60 °C for 16 h. This method was simple and time-saving compared with the commonly used surface-initiated polymerization. More importantly, the molecularly imprinted polymer (MIP) film prepared using this method was much thicker than that of commonly used methods; the adsorption quantity was also much larger. The MIP modified SPR sensor showed high sensitivity and selectivity as well as good stability in detecting MG. The results suggest that the ultrathin MIP film prepared using the new method in this study is suitable to serve as the recognition element of the SPR sensor.     

丹酚酸A分子印迹聚合物制备及识别性能研究

以丹酚酸A为模板分子,丙烯酰胺(AM)、α-甲基丙烯酸(MAA)、2-乙烯基吡啶(2-VP)和4-乙烯基吡啶(4-VP)为功能单体,乙二醇二甲基丙烯酸酯(EGDMA)为交联剂,丙酮、乙酸乙酯、乙腈和甲醇为致孔剂,采用本体聚合法制备了一系列丹酚酸A分子印迹聚合物.通过静态平衡吸附实验和选择性实验考察了印迹聚合物的吸附性能...     

苄嘧磺隆印迹聚合物的波谱分析及吸附性能研究

以苄嘧磺隆为模板分子, α-甲基丙烯酸为功能单体, 三甲氧基丙烷三甲基丙烯酸酯为交联剂, 二氯甲烷为致孔剂, 在20 ℃温度下, 采用紫外引发沉淀聚合方法制备了苄嘧磺隆分子印迹聚合物. 紫外光谱和核磁共振氢谱实验提示了聚合前模板分子与功能单体之间的相互作用主要是分子间氢键, 分子间氢键相互作用能和双氢键的键距由Hyperchem 7.0和Gaussian 03W软件分别计算为: －28.6163 kJ/mol和0.179～0.181 nm. 制备的印迹聚合物在高效液相色谱和吸附动力学实验中都表现出对模板分子有较强的吸附作用.     

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.     

Computational design and synthesis of molecular imprinted polymers with high selectivity for removal of aniline from contaminated water

A computational approach was developed to screening functional monomers and polymerization solvents for rational design of molecularly imprinted polymer (MIP). It was based on the comparison of the binding energy of the complexes between the template and different functional monomers. The effect of the polymerization solvent was included using the polarizable continuum model. According to the theoretical calculation results, the MIP with aniline as template was prepared by emulsion polymerization method using acrylamide (AAM) as functional monomer and divinylbenzene as cross-linker in carbon tetrachloride. The synthesized MIP was then tested by equilibrium-adsorption method, and the MIP demonstrated high removal efficiency to the aniline. The results of this study have indicated the possibility of using computer aided design for rational selection of functional monomers and solvents capable of removal of aniline from contaminated water.     

Monodispersed, molecularly imprinted polymers for cinchonidine by precipitation polymerization

Three monodispersed, molecularly imprinted polymers (MIPs) for cinchonidine (CD) have been synthesized by precipitation polymerization. MIP1 was prepared using methacrylic acid (MAA) as a functional monomer and divinylbenzene (DVB) as a cross-linker and MIP2 was prepared with further addition of 2-hydroxyethyl methacrylate (HEMA) as a co-monomer. For the preparation of MIP3, core-shell type MIP, monodispersed DVB homopolymers, which are prepared by precipitation polymerization, were used as a core and CD-imprinted MAA-DVB copolymer phases were coated onto the core. Three MIPs synthesized gave monodispersed, spherical beads in micrometer sizes. The binding characteristics and molecular recognition properties of MIP1-3 were examined by Scatchard analysis and chromatographic studies. The association constant of CD with MIP1 was the highest among MIPs prepared, while that with MIP3 was the lowest. The template molecule, CD, was more retained than its stereoisomer, cinchonine, on the three MIPs, and the stereoseparation factor of 38 was obtained with MIP3.     

Development of a model for the rational design of molecular imprinted polymer: Computational approach for combined molecular dynamics/quantum mechanics calculations

A new rational approach for the preparation of molecularly imprinted polymer (MIP) based on the combination of molecular dynamics (MD) simulations and quantum mechanics (QM) calculations is described in this work. Before performing molecular modeling, a virtual library of functional monomers was created containing forty frequently used monomers. The MD simulations were first conducted to screen the top three monomers from virtual library in each porogen-acetonitrile, chloroform and carbon tetrachloride. QM simulations were then performed with an aim to select the optimum monomer and progen solvent in which the QM simulations were carried out; the monomers giving the highest binding energies were chosen as the candidate to prepare MIP in its corresponding solvent. The acetochlor, a widely used herbicide, was chosen as the target analyte. According to the theoretical calculation results, the MIP with acetochlor as template was prepared by emulsion polymerization method using N,N-methylene bisacrylamide (MBAAM) as functional monomer and divinylbenzene (DVB) as cross-linker in chloroform. The synthesized MIP was then tested by equilibrium-adsorption method, and the MIP demonstrated high removal efficiency to the acetochlor. Mulliken charge distribution and ¹H NMR spectroscopy of the synthesized MIP provided insight on the nature of recognition during the imprinting process probing the governing interactions for selective binding site formation at a molecular level. We think the computer simulation method first proposed in this paper is a novel and reliable method for the design and synthesis of MIP.     

咖啡因分子印迹固相萃取柱的制备及应用

以咖啡因作为模板分子,α-甲基丙烯酸为功能单体,乙二醇二甲基丙烯酸酯为交联剂,制备了咖啡因分子印迹聚合物(MIP)。与非印迹聚合物(NIP)相比,MIP对咖啡因具有更高的吸附容量和选择性,MIP和NIP对咖啡因的最大静态吸附量分别为28.1和16.5mg/g,相对选择因子为1.25。以咖啡因分子印迹聚合物为固相萃取填料,结合高效液相色谱(HPLC),建立了茶水中咖啡因浓度及人饮茶后血清中咖啡因浓度的检测方法。考察了洗脱剂种类和用量对咖啡因回收率的影响。当萃取柱依次以2mL水活化,水溶液上样,2mL水淋洗,6mL甲醇-乙酸(9∶1,V/V)洗脱,咖啡因在MIP固相萃取柱上的回收率达到97.5%,而在NIP柱上的回收率仅为54.9%。