Preparative separation and determination of matrine from the Chinese medicinal plant <Emphasis Type="Italic"> Sophora flavescens </Emphasis>Ait by molecularly imprinted solid-phase extraction

Molecularly imprinted microspheres (MIMs) were synthesized by micro-suspension polymerization using matrine (MT) as template. The MIMs were employed for solid-phase extraction (SPE) and as chromatographic stationary phase for the determination of MT from the Chinese medicinal plant Sophora flavescens. The effects of the various eluents, their concentrations and volumes on the retention behavior were investigated. The selectivity and capacity of the imprinted microspheres against MT was also discussed. The results showed that the MIMs exhibited stronger specific affinity to MT than to oxymatrine (OMT). Methanol-water (3:7, v/v) was used for washing impurities from the MIMs-SPE cartridge loaded with the herb extracts, while methanol-glacial acetic acid (9:1, v/v) was used for eluting MT. The maximum load of MT and the recovery of MIMs cartridge towards MT were 38.7 microg g(-1) and 71.4%, respectively. The method developed might be used to separate and extract effective constituents from Chinese medicinal plants on a large scale.     

Molecularly imprinted stationary phase prepared by reverse micro-emulsion polymerization for selective recognition of gatifloxacin in aqueous media

A new stationary phase for selectively recognizing gatifloxacin in aqueous media based on molecularly imprinted microspheres (MIMs) has been prepared by water/oil reverse micro-emulsion polymerization. The MIMs were prepared using gatifloxacin as the template, N, N'-methylenebisacrylamide as cross-linker and acrylamide and acryloyl-β-CD (β-CD-A, synthesized by ester reaction of acrylic acid with β-CD) as combinatorial functional monomers. The surface morphology of MIMs was characterized by scanning electron microscopy. The properties of MIMs recognition for gatifloxacin in water were studied by adsorption kinetics, adsorption isotherms combined with Scatchard analysis and selective recognition experiments. The results showed that the synthesized MIMs had an excellent ability to selectively recognize gatifloxacin in aqueous media. MIMs were employed as the chromatographic stationary phase to successfully separate the template gatifloxacin from its analogues. Discovering the mechanism of the MIMs recognition revealed that the memory cavities in the surface of the MIMs and hydrophobic effects between the template and the cavities of the β-CD residues were the primary contributions to the special recognition process.     

Grafting of MIPs from PVDF Membranes via Reversible Addition-fragmentation Chain Transfer Polymerization for Selective Removal of p-Hydroxybenzoic Acid

Effective molecularly imprinted membranes(MIMs) were developed as an efficient adsorbent for the selective removal of p-hydroxybenzoic acid(p-HB) from acetylsalicylic acid(ASA, aspirin). The MIMs were grafted successfully from poly(vinylidene fluoride) microfiltration membranes via reversible addition-fragmentation chain transfer(RAFT) polymerization. The graft copolymerization of acrylic acid(AA) in the presence of template p-hydroxybenzoic acid led to molecularly imprinted polymer(MIP) film coated membranes. The obtained MIMs were characterized by scanning electron microscopy(SEM), Fourier transform infrared spectrophotometer(FTIR) and Raman spectra, and batch mode adsorption studies were carried out to investigate the specific adsorption equilibrium, kinetics and selective recognition properties of different MIMs. The kinetic properties of the MIMs could be well described by the pseudo-second-order rate equation. Selective permeation experiments were performed to evaluate the permeation selectivity of the p-HB imprinted membranes. The observed performances of the MIMs are applicable to the further purification of aspirin.     

Determination of ofloxacin and lomefloxacin in chicken muscle using molecularly imprinted solid-phase extraction coupled with liquid chromatography

A new molecularly imprinted solid-phase extraction (MISPE) procedure combined with liquid chromatography was developed for the simultaneous selective extraction and determination of ofloxacin (OFL) and lomefloxacin (LOM) in chicken muscle samples. The water-compatible molecularly imprinted microspheres (MIMs) were synthesized by aqueous suspension polymerization using 2-hydroxy-3-naphthoic acid and 1-methylpiperazine as mimic templates. The MIMs applied as selective sorbents in SPE method showed high selectivity and affinity to OFL and LOM in complex biological matrices. Good linearity was obtained in a range of 0.025-2.0 μg/g, and the average recoveries of OFL and LOM at three spiked levels ranged from 94.4 to 96.9%, respectively, with the relative standard deviation ≤4.7%. The developed MISPE-HPLC method was successfully applied to the isolation of OFL and LOM in chicken muscles, which demonstrated the potential ability of the novel MIMs for selective extraction of fluoroquinolones in biological samples.     

Surface molecularly imprinted polymers prepared by two‐step precipitation polymerization for the selective extraction of oleanolic acid from grape pomace extract

Surface molecularly imprinted polymers were successfully prepared by a novel two‐step precipitation polymerization method. The first‐step allowed the formation of 4‐vinylpyridine divinylbenzene and trimethylolpropane trimethacrylate copolymeric microspheres. In the second‐step precipitation polymerization, microspheres were modified with a molecularly imprinting layer of oleanolic acid as template, methacrylic acid as functional monomer, and divinylbenzene/ethylene glycol dimethacrylate as cross‐linker. The obtained polymers had an average diameter of 4.43 μm and a polydispersity index of 1.011; adsorption equilibrium was achieved within 40 min, with adsorption capacity reaching 27.4 mg/g. Subsequently, the polymers were successfully applied as the adsorbents of molecularly imprinted solid‐phase extraction to separate and purify the oleanolic acid from grape pomace. The content of oleanolic acid in the grape pomace extract was enhanced from 13.4 to 93.2% after using the molecularly imprinted solid‐phase extraction process. This work provides an efficient way for effective oleanolic acid separation and enrichment from complex matrices, which is especially valuable in industrial production.     

Recognition characteristics of molecularly imprinted microspheres for triazine herbicides using hydrogen-bond array strategy and their analytical applications for corn and soil samples

The homogeneous molecularly imprinted microspheres (MIMs) based on a biologically inspired hydrogen-bond array were prepared using allobarbital as the novel functional monomer and divinylbenzene as the cross-linker. The host-guest binding characteristics were examined by molecular simulation and infrared spectroscopy. The resultant MIMs were evaluated using high performance liquid chromatography and solid-phase extraction. The results obtained demonstrate that the good imprinting effect and the excellent selectivity of MIMs are mainly due to the interaction involving the formation of three-point hydrogen bond between host and guest. The complete baseline separation was obtained for five triazine analogues and a metabolite on the MIM HPLC column. The MIMs were further successfully used as a specific sorbent for selective extraction of simetryne from corn and soil samples by molecularly imprinted solid phase extraction. Detection limits and recoveries were 5.8 μg/kg and 0.14 μg/kg and 87.4-105% and 94.6-101% for simetryne in corn and soil sample, respectively.     

Molecularly imprinted microspheres for the anticancer drug aminoglutethimide: Synthesis,characterization, and solid‐phase extraction applications in human urine samples

Molecularly imprinted microspheres (MIMs) for the anticancer drug aminoglutethimide (AG) were synthesized by aqueous suspension polymerization. The expected size and diameter of MIMs are controlled easily by changing one of the surfactant types, ratio of organic‐to‐water phase or stirring rate during polymerization. The obtained MIMs exhibit specific affinity toward AG with imprinting factor of 3.11 evaluated with a chromatographic model. The resultant MIMs were used as the SPE materials for the extraction of AG from human urine. A molecularly imprinted SPE (MISPE) method coupled with HPLC has been developed for the extraction and detection of AG in urine. Our results showed that most impurities from urine can be removed effectively after a washing step and the AG has been enriched effectively after MISPE operation with the recovery of >90% (n = 3). The developed MISPE–HPLC method could be used for enrichment and detection of AG in human urine.     

Preparation and characterization of molecularly imprinted microspheres for selective extraction of trace melamine from milk samples

We describe molecularly imprinted microspheres (MIMs) for the selective extraction of melamine from milk. The MIMs were made from melamine as the template molecule, methacrylic acid as the functional monomer, and ethylene glycol dimethacrylate as the linking agent. The MIMs were synthesized by suspension polymerization and characterized by rebinding experiments. They displayed high adsorption capacity, fast rebinding kinetics, and highly specific rebinding of melamine. The imprinting factor is 4.1. Scatchard analysis revealed a one-type rebinding behavior, the dissociation constant and maximum rebinding capacity being 37.59 g L^?1 and 30.85 μmol g^?1, respectively. The MIMs exhibited a 25% cross-reactivity towards atrazine, but less than 3.0% towards prometryn, clenbuterol and metronidazole. In addition, a MIM-based solid phase extraction (MISPE) column for melamine was prepared by packing MIMs into a common SPE cartridge. The MISPE extraction gave recoveries of 89.8 to 100.6% of melamine, with relative standard deviations of 5.9 to 7.5%. There was no significant loss of rebinding capacity after more than 60 repeated uses, thus demonstrating the high stability of the MISPE column. The MSPE column also was applied to the extraction of melamine from spiked liquid and powdered milk with satisfying accuracy and precision.

Preparation and evaluation of molecularly imprinted microspheres for solid-phase extraction of 1,4-hydroxybenzoic acid esters in soy

Molecularly imprinted microspheres (MIMs) were prepared by precipitation polymerization for the binding and recognition of 1,4-hydroxybenzoic acid esters. Ethyl p-hydroxybenzoate (EtPHB) was used as the template molecule, methacrylic acid as the functional monomer, ethylene dimethacrylate as the linking agent. It was evaluated by solid-phase extraction column packed with MIMs combined with liquid chromatography to determine trace preservatives including benzoic acid, methyl p-hydroxybenzoate, EtPHB, propyl p-hydroxybenzoate in food products. A solid-phase extraction based on MIM procedure was used to isolate four additives from the food matrix before quantitative analysis. The Scatchard plot suggested that the template-polymer system had two-site binding behavior with the dissociation constants of 0.3577 and 3.952 mg/g, respectively. The rebinding test, based on the molecularly imprinted solid-phase extraction column technique, showed the recoveries of soy samples spiked with four additives within 88.4-110.6%, with the relative standard deviations of 1.97-3.82%. Finally, the method was successfully applied for the analysis of parabens in foodstuff without traditional pretreatment.     

Preparation and characterization of monodisperse molecularly imprinted polymers for the recognition and enrichment of oleanolic acid

Monodisperse molecularly imprinted polymers for oleanolic acid were successfully prepared by a precipitation polymerization method using oleanolic acid as a template, methacrylic acid as a functional monomer, and divinylbenzene/ethylene glycol dimethacrylate as a crosslinker in a mixture of acetonitrile and ethanol (3:1, v/v). The imprinted polymers and nonimprinted polymers were characterized by using scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The resulting imprinted polymers had average diameters of 3.15 μm and monodispersity values of 1.024. The results clearly demonstrate that use of ethanol as a cosolvent is indeed exceedingly effective in promoting the dissolution of oleanolic acid and in obtaining uniform microspheres. Molecular recognition properties and binding capability to oleanolic acid were evaluated by adsorption testing, which indicated that the imprinted polymers displayed optimal binding performance with a maximum adsorption capacity of 17.3 mg/g and a binding saturation time of 80 min. Meanwhile, the produced imprinted polymers exhibited higher selectivity to oleanolic acid than that for ursolic acid and rhein. Herein, the studies can provide theoretical and experimental references for the oleanolic acid molecular imprinted system.     

Development of molecularly imprinted microspheres for the fast uptake of 4‐cumylphenol from water and soil samples

Molecularly imprinted microspheres containing binding sites for the extraction of 4‐cumylphenol have been prepared for the first time. The imprinted microspheres were synthesized by a precipitation method using 4‐cumylphenol as a template molecule, methacrylic acid as a functional monomer and divinylbenzene‐80 as a cross‐linker for polymer network formation. The formation and the morphology of molecularly imprinted microspheres were well characterized using infrared spectroscopy, thermogravimetric studies, and scanning electron microscopy. The Brunauer–Emmett–Teller analysis revealed the high surface area of the sorbent indicating formation of molecularly imprinted microspheres. The developed microspheres were employed as a sorbent for the solid‐phase extraction of 4‐cumylphenol and showed fast uptake kinetics. The sorption parameters were optimized to achieve efficient sorption of the template molecule, like pH, quantity of molecularly imprinted microspheres, time required for equilibrium set‐up, sorption kinetics, and adsorption isotherm. A standard method was developed to analyze the sorbed sample quantitatively at 279 nm using high‐performance liquid chromatography with diode array detection. It was validated by determining target analyte from synthetic samples, bottled water, spiked tap water, and soil samples. The prepared material is a selective and robust sorbent with good reusability.     

Selective separation of magnolol using molecularly imprinted membranes

Molecularly imprinted membranes (MIMs) for selective separation of magnolol were prepared by thermal polymerization using magnolol as the template, ethylene glycol dimethacrylate (EGDMA) as the cross‐linker, 2,2‐azobisisobutyronitrile (AIBN) as the initiator, organic solvent as the porogen, methacrylamide (MAM) and acrylic acid (AA) as the functional monomers and cellulose acetate as the agglutinant. Commercial filter paper was used as the supporting material. The effects of different porogens and the ratio of functional monomers on the binding and recognition capacity of MIMs were investigated, and the morphology of the membranes was examined by scanning electron microscopy (SEM). The results showed that the MIMs have the highest selectivity to magnolol when the ratio of MAM/AA was 1:4 and tetrahydrofuran (THF) with dimethyl sulfoxide (DMSO) was used as the porogen. The morphology of the imprinted membranes after template extracting is much rougher with big cavities than that of the non‐imprinted membranes (NIMs) and the imprinted membranes before template extracting. The MIMs can selectively separate the magnolol.     

Preparing molecularly imprinted membranes by phase inversion to separate kaempferol

Molecularly imprinted membranes (MIMs) were studied to separate special target molecule – kaempferol, an important active pharmaceutical ingredient. The kaempferol MIM were prepared by the liquid–solid phase inversion method. The effects of polyphenylene sulfone, LiCl, and ZnCl₂ on membrane performance were studied, a high Flux MIM was prepared, then the kaempferol molecularly imprinted polymer membrane, non‐molecularly imprinted membrane, and non‐molecularly imprinted polymer membrane were prepared to investigate adsorption capacity. From adsorption isotherm curve, the maximum equilibrium adsorption quantity was 890 µg/g, and it was MIM. The MIM and molecularly imprinted polymer membrane give high selectivity towards kaempferol; the non‐molecularly imprinted membrane and non‐molecularly imprinted polymer membrane showed low adsorption quantity and selectivity. The reuse experiment of the MIM indicated that it has good reuse property. All the results showed binding sites were important in the separation process of MIMs. Copyright © 2016 John Wiley & Sons, Ltd.     

Evaluation of diazepam-molecularly imprinted microspheres for the separation of diazepam and its main metabolite from body fluid samples

Molecularly imprinted microspheres (MIMs) for the drug diazepam and its main metabolite (nordiazepam) were prepared and used to separate the two species from urine and serum samples via molecularly imprinted solid-phase extraction. The specific binding capacity for diazepam was determined to be 1.97 mg/g, resulting in an imprinting factor of 5.8. The MIMs exhibit highly selective binding affinity for tricyclic benzodiazepines. Water-acetonitrile-acetone mixtures were used as the washing solvent and resulted in complete baseline separation, with a recovery of >87% for diazepam and of 88% for nordiazepam. The limits of detection are 21.5 and 24.5 ng/mL, respectively.     

Preparation of ellagic acid molecularly imprinted polymeric microspheres based on distillation–precipitation polymerization for the efficient purification of a crude extract

Molecularly imprinted polymeric microspheres with a high recognition ability toward the template molecule, ellagic acid, were synthesized based on distillation–precipitation polymerization. The as‐obtained polymers were characterized by scanning electron microscopy, infrared spectroscopy, and thermogravimetric analysis. Static, dynamic, and selective binding tests were adopted to study the binding properties and the molecular recognition ability of the prepared polymers for ellagic acid. The results indicated that the maximum static adsorption capacity of the prepared polymers toward ellagic acid was 37.07 mg/g and the adsorption equilibrium time was about 100 min when the concentration of ellagic acid was 40 mg/mL. Molecularly imprinted polymeric microspheres were also highly selective toward ellagic acid compared with its analogue quercetin. It was found that the content of ellagic acid in the pomegranate peel extract was enhanced from 23 to 86% after such molecularly imprinted solid‐phase extraction process. This work provides an efficient way for effective separation and enrichment of ellagic acid from complex matrix, which is especially valuable in industrial production.     

Determination of glyphosate in foodstuff by one novel chemiluminescence-molecular imprinting sensor

A novel chemiluminescence (CL) sensor for the determination of glyphosate (GLY) was made up based on molecularly imprinted polymer (MIP). The molecularly imprinted microspheres (MIMs) with a small dimension which possess extremely high surface-to-volume ratio were synthesized using precipitation polymerization with GLY as template. And then the MIMs were modified on glass sheets, which were placed at the bottom of wells of microplate as the recognizer. Subsequently, a highly selective and high throughput chemiluminescence (CL)-molecular imprinting (MI) sensor for detection of GLY was achieved. Influencing factors were investigated and optimized in detail. The method can perform 96 independent measurements sequentially in 10 min and the limit of detection (LOD) for GLY was 0.046 μg mL(-1). The relative standard deviation (RSD) for 11 parallel measurements of GLY was 4.68%. The results show that CL-MI sensor can become a useful analytical technology for quick molecular recognition.     

离子液体-水双相体系悬浮聚合法制备对苯二酚分子印迹聚合物微球

通过在[Bmim]PF6离子液体-水双相体系中,以对苯二酚为模板分子,甲基丙烯酸为功能单体,二甲基丙烯酸乙二醇脂为交联剂,采用悬浮聚合法制备得到对苯二酚印迹聚合物微球(MIMs-IL),并通过FTIR等测试技术对MIMs-IL进行了表征。对不同离子液体进行了选择,[Bmim]PF6介质中制备的MIMs-IL的识别性能最好。与从氯仿介质中制备的印迹聚合物微球(MIMs-Or)相比较,MIMs-IL的产率为70.8%,明显高于MIMs-Or的48.7%。采用静态吸附法考察其印迹识别能力的结果表明,MIMs-IL对水中的对苯二酚的识别能力大大强于MIMs-Or。对MIMs-IL识别吸附的热力学和动力学研究结果表明,12h时MIMs-IL及其非印迹聚合物微球(nMIMs-IL)均达到各自饱和吸附量,对于0.50g/L对苯二酚水溶液,MIMs-IL的饱和吸附量是nMIMs-IL的2.67倍。     

L-组氨酸手性识别印迹固定相的制备及表征

以L-组氨酸为模板分子, 甲基丙烯酸为功能单体, 乙二醇二甲基丙烯酸酯为交联剂, 偶氮二异丁腈为引发剂, 在水-乙腈微乳体系中采用沉淀聚合方法制备了具有手性识别L-组氨酸功能的印迹微球. 采用静态平衡吸附实验及色谱分析探讨聚合微球对模板分子的选择识别吸附性能. 结果表明, 该印迹聚合物微球对模板分子存在两种结合位点, 最大表观结合量分别为33.04和24.16 μmol/g. 相对于常规的C18柱, 该印迹聚合物填充柱能够完全分离L-组氨酸和D-组氨酸, 分离度R为2.23, 选择因子为2.14. 利用差热分析、红外光谱及X射线衍射等技术表征聚合物微球的热性能及结构. 结果表明, 聚合物微球具有良好的热稳定性, 是一种具有部分晶体结构的聚合物.     

多壁碳纳米管表面熊果酸印迹聚合物的制备及固相萃取

以聚乙烯醇修饰的多壁碳纳米管(MWCNTs)为基材,熊果酸(UA)为模板分子,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,采用表面印迹技术在碳纳米管表面合成对熊果酸具有良好选择性的分子印迹聚合物( MWCNTs-MIPs).讨论了不同摩尔比例的功能单体与模板分子合成印迹聚合物的效果,得出...     

水溶液微悬浮聚合法制备酸性药物吲哚美辛分子印迹微球及其色谱表征

以带有羧基的酸性药物吲哚美辛为模板分子、碱性的4-乙烯基吡啶为功能单体,采用水溶液微悬浮聚合法制备了用于色谱分离的微米级分子印迹微球.详细讨论了流动相中缓冲溶液的pH值对吲哚美辛在MIMs柱上的容量因子(k′)、分离因子(α)和印迹因子(β)的影响.通过MIMs柱对吲哚美辛和4-氨基吡啶(4-AP)的保留行为的比较,证明以4-乙烯基吡啶为功能单体制得的MIMs对吲哚美辛的识别作用,主要靠吡啶环上氮原子与吲哚美辛羧基之间的离子键相互作用,以及吡啶环与模板分子之间的π-π相互作用.