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.     

Water‐compatible halloysite‐imprinted polymer by Pickering emulsion polymerization for the selective recognition of herbicides

A water‐compatible molecularly imprinted polymer was prepared by Pickering emulsion polymerization using halloysite nanotubes as stabilized solid particles. During polymerization, we used 4‐vinylpyridine as monomer, divinylbenzene as cross‐linking agent, toluene as porogen, 2,2‐azobisisobutyronitrile as initiator, 2,4‐dichlorophenoxyacetic acid as template to form the oil phase, and Triton X‐100 aqueous solution to form the water phase. The halloysite nanotubes molecularly imprinted polymer was characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. Kinetic and equilibrium bindings were also employed to evaluate the adsorption properties of the imprinted polymer. The imprinted polymer showed better selectivity, more rapid kinetic binding (60 min) for 2,4‐dichlorophenoxyacetic acid in pure water compared with rebinding in toluene. The imprinted polymer was used as a sorbent to enrich and separate 2,4‐dichlorophenoxyacetic acid from water, and was detected by high‐performance liquid chromatography with UV detection.     

Comparison of binding behavior for molecularly imprinted polymers prepared by hierarchical imprinting or Pickering emulsion polymerization

The aim of this study was the evaluation of the binding performances and selectivity of molecularly imprinted beads prepared toward several penicillins (i) by hierarchical bulk polymerization in the pores of template‐grafted silica microbeads (hMIPs) and (ii) by Pickering emulsion polymerization in the presence of template‐decorated silica nanobeads (pMIPs). 6‐Aminopenicillanic acid was chosen as the common fragmental mimic template. Both approaches produced micron‐sized polymeric beads with good recognition properties toward the target ligands whereas the selectivity pattern appeared quite different. The polymer prepared by the Pickering emulsion approach showed binding properties similar to imprinted beads prepared by hierarchical approach. Equilibrium binding constants changed their values from 0.1–0.2 × 10⁶ (hMIPs) to 0.2–0.6 × 10⁶ M^?1 (pMIPs), while the binding site densities changed from 3.7–4.8 (hMIPs) to 0.3–0.55 μmol/g (pMIPs). Compared to the hierarchical polymerization, Pickering emulsion polymerization represents a more practical approach when a template mimic needs to be used.     

Preparation and characterization of molecularly imprinted polymers based on β‐cyclodextrin‐stabilized Pickering emulsion polymerization for selective recognition of erythromycin from river water and milk

Molecularly imprinted polymers were prepared via β‐cyclodextrin‐stabilized oil‐in‐water Pickering emulsion polymerization for selective recognition and adsorption of erythromycin. The synthesized molecularly imprinted polymers were spherical in shape, with diameters ranging from 20 to 40 µm. The molecularly imprinted polymers showed high adsorption capacity (87.08 mg/g) and adsorption isotherm data fitted well with Langmuir model. Adsorption kinetics study demonstrated that the molecularly imprinted polymers acted in a fast adsorption kinetic pattern and the adsorption features of molecularly imprinted polymers followed a pseudo‐first‐order model. Adsorption selectivity analysis revealed that molecularly imprinted polymers had a much better specificity for erythromycin than that for spiramycin or amoxicillin, and the relative selectivity coefficient values on the bases of spiramycin and amoxicillin were 3.97 and 3.86, respectively. The Molecularly imprinted polymers also showed a satisfactory reusability after four times of regeneration. In addition, molecularly imprinted polymers exhibited good adsorption capacities for erythromycin under complicated environment, that is, river water and milk. These results proved that the as‐prepared molecularly imprinted polymers is a potent absorbent for selective recognition of erythromycin, and therefore it may be a promising candidate for practical applications, such as wastewater treatment and detection of erythromycin residues in food.     

Selective enrichment and separation of phosphotyrosine peptides by thermosensitive molecularly imprinted polymers

Novel thermosensitive molecularly imprinted polymers were successfully prepared using the epitope imprinting approach in the presence of the mimic template phenylphosphonic acid, the functional monomer vinylphosphonic acid‐Ti⁴⁺, the temperature‐sensitive monomer N‐isopropylacrylamide and the crosslinker N,N′‐methylenebisacrylamide. The ratio of the template/thermosensitive monomers/crosslinker was optimized, and when the ratio was 2:2:1, the prepared thermosensitive molecularly imprinted polymers had the highest imprinting factor. The synthetic thermosensitive molecularly imprinted polymers were characterized by Fourier transform infrared spectroscopy to reveal the combination and elution processes of the template. Then, the adsorption capacity and thermosensitivity was measured. When the temperature was 28°C, the imprinting factor was the highest. The selectivity and adsorption capacity of the thermosensitive molecularly imprinted polymers for phosphotyrosine peptides from a mixture of three tailor‐made peptides were measured by high‐performance liquid chromatography. The results showed that the thermosensitive molecularly imprinted polymers have good selectivity for phosphotyrosine peptides. Finally, the imprinted hydrogels were applied to specifically adsorb phosphotyrosine peptides from a sample mixture containing phosphotyrosine and a tryptic digest of β‐casein, which demonstrated high selectivity. After four rebinding cycles, 78.9% adsorption efficiency was still retained.     

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.     

Preparation of high selective molecularly imprinted polymers for tetracycline by precipitation polymerization

High selective molecularly imprinted polymers(MIPs) for tetracycline have been prepared by precipitation polymerization. Effects of monomer and solvent,the ratio of monomer and template and the characterization of the polymer were investigated by frontal chromatography and selectivity experiment.The results clearly indicated that the polymer,which had the highest molecular recognition abilities for tetracycline antibiotics,had been received.     

Selective separation and enrichment of glibenclamide in health foods using surface molecularly imprinted polymers prepared via dendritic grafting of magnetic nanoparticles

In this paper, the novel surface molecularly imprinted polymers based on dendritic‐grafting magnetic nanoparticles were developed to enrich and separate glibenclamide in health foods. The density functional theory method was used to give theoretical directions to the synthesis of molecularly imprinted polymers. The polymers were prepared by using magnetic nanoparticles as supporting materials, methacrylic acid as the functional monomer, and ethylene glycol dimethacrylate as the cross‐linker. The characteristics of magnetic nanoparticles and polymers were measured by transmission electron microscope and SEM, respectively. The enriching ability of molecularly imprinted polymers was measured by Freundlich Isotherm. The molecularly imprinted polymers were used as dispersive SPE materials to enrich, separate, and detect glibenclamide in health foods by HPLC. The average recoveries of glibenclamide in spiked health foods were 81.46–93.53% with the RSD < 4.07%.     

Narrowly dispersed molecularly imprinted microspheres prepared by a modified precipitation polymerization method

A modified precipitation polymerization (MPP) method was established to prepare narrowly dispersed molecularly imprinted polymeric microspheres. MPP was stabilizer and surfactant free and needed only small amount of porogen (about 50 wt.%). Only part of alcohols and all the alkanes tested formed particles. Using a mixture of alkane and toluene as porogen, the carbon numbers of alkanes and solubility parameter of porogenic solvents were important factors in controlling particle morphology. Nearly mono-dispersed microspheres with diameter of about 2-3 μm were synthesized by MPP using mineral oil:toluene = 2:3 as porogen. Template did not affect the formation of globe microspheres in MPP. Microspheres prepared under the lowest reaction temperature had the highest binding capability. When used as sorbents of high performance liquid chromatography (HPLC), the microspheres prepared by MPP using bisphenol A, estradiol, and tebuconazole as template had similar binding selectivity and higher binding capability compared to microspheres synthesized by classical precipitation polymerization. Photoinitiation and low reaction temperature were important factors attributed to better binding capability of microspheres prepared by MPP.     

Selective recognition of sesamol using molecularly imprinted polymers containing magnetic wollastonite

The magnetic molecularly imprinted polymers (MMIPs) have been synthesized using piperonal molecules as dummy template and magnetic wollastonite composites as support. The resulting composites were applied to selective recognition of sesamol from aqueous solution. MMIPs were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) analysis, transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), thermogravimetric analysis (TGA), and vibrating sample magnetometer (VSM). MMIPs were demonstrated with an imprinted polymer film (90-100 nm) and exhibited magnetic property (M(s) =8.60 emu/g) and thermal stability. The effective average diameter of the Fe(3) O(4) nanoparticles was about 10 nm and the thickness of magnetic film was about 160 nm. Batch mode adsorption studies were carried out to investigate the specific adsorption equilibrium, kinetics and selective recognition. The Langmuir isotherm model was fitted to the equilibrium data better than the Freundlich model, and the kinetic properties were well described by the pseudo-second-order equation. The value of E(a) in this study was 5.35 kJ/mol for MMIPs. In addition, the selective recognition experiments demonstrated that MMIPs have specific recognition ability toward sesamol.     

Preparation of magnetic molecularly imprinted polymers for the rapid and selective separation and enrichment of perfluorooctane sulfonate

As a persistent organic pollutant, perfluorooctane sulfonate has drawn a great worldwide attention. In this contribution, a novel material of magnetic molecularly imprinted polymers, based on perfluorooctane sulfonate, as a template, molecule was prepared. The magnetic molecularly imprinted polymers were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, and vibrating sample magnetometry. The adsorption isotherm was measured, and adsorption kinetic tests were conducted. The adsorbents possess high recognition ability (2.460 mg/g) and short adsorption equilibration time (60 min). Besides, they show good specificity and good reusability with the adsorption capacities of adsorbent toward perfluorooctane sulfonate decreasing less than 3% after five adsorption–desorption cycles. The magnetic molecularly imprinted polymers were used successfully in the separation and enrichment of perfluorooctane sulfonate in real water sample and exhibited good prospects in environmental treatment and monitoring.     

Adsorption of carbaryl using molecularly imprinted microspheres prepared by precipitation polymerization

To obtain the desired specific adsorbents for carbaryl to enrichment, separation, and analysis of trace pesticide residues in environmental water, molecularly imprinted polymer (MIP) microspheres were prepared by precipitation polymerization using carbaryl, methacrylic acid (MAA), ethylene glycol dimethacrylate (EGDMA), azobisisobutyronitrile (AIBN), and acetonitrile as template, functional monomer, cross‐linker, initiator, and porogen, respectively. Molecular modeling software was used to compute rational interaction between the template molecule and function monomer. The adsorption properties of carbaryl in acetonitrile for imprinted microspheres were evaluated by equilibrium rebinding experiments. Scatchard plot analysis revealed that there was one class of binding sites populated in the imprinted polymer microspheres with dissociation constants of 3.3 × 10^?2 mol/l and an apparent maximum number of 1.95 µmol/g. The specificity of the imprinted microspheres was investigated by binding analysis using carbaryl and structurally related carbamate pesticides. The results indicated that the obtained imprinted microspheres showed a good selectivity for carbaryl. Copyright © 2007 John Wiley & Sons, Ltd.     

Preparation and characterization of erythromycin molecularly imprinted polymers based on distillation–precipitation polymerization

Erythromycin‐imprinted polymers with excellent recognition properties were prepared by an innovative strategy called distillation–precipitation polymerization. The interaction between erythromycin and methacrylic acid was studied by ultraviolet absorption spectroscopy, and the as‐prepared materials were characterized by Fourier‐transform infrared spectroscopy and scanning electron microscopy. Moreover, their binding performances were evaluated in detail by static, kinetic and selective sorption tests. It was found that the molecularly imprinted polymers afforded good morphology, monodispersity, and high adsorption capacity when the fraction of the monomers was 7 vol% in the whole reaction system, and the adsorption data for imprinted polymers correlated well with the Langmuir model. The maximum capacity of the imprinted and the non‐imprinted polymers for adsorbing erythromycin is 44.03 and 19.95 mg/g, respectively. The kinetic studies revealed that the adsorption process fitted a pseudo‐second‐order kinetic model. Furthermore, the imprinted polymers display higher affinity toward erythromycin, compared with its analogue roxithromycin.     

Synthesis of ZnO/polystyrene composites particles by Pickering emulsion polymerization

ZnO/polystyrene composite particles were synthesized by Pickering emulsion polymerization. ZnO nanoparticles were first prepared by reaction of zinc acetate and sodium hydroxide in ethanol medium. Then different amount of styrene monomer was emulsified in water in the presence of ZnO nanoparticles either by mechanical stirring or by sonication, followed by polymerization of styrene. Two kinds of initiators were used to start the polymerization, azobisisobutyronitrile (AIBN) and potassium persulfate (KPS). The X-ray diffraction pattern verified the crystal structure of ZnO and FT-IR spectra evidenced the existence of ZnO and polystyrene (PS) in ZnO/polystyrene composite particles. Different morphologies were observed for the composite particles when using different initiators. From TEM photographs, AIBN-initiated system produced mainly core-shell composite particles with PS as core and ZnO as shell, while KPS-initiated system showed both composite particles and pure PS particles. Two schemes of reaction mechanism were proposed to explain the morphologies accordingly. Both systems of composite particles showed good pH adjusting ability.     

Hollow microspheres with covalent‐bonded colloidal and polymeric shell by Pickering emulsion polymerization

Hollow microspheres with SiO₂/polymer binary shell were fabricated from Pickering emulsion stabilized solely by methacryloxypropyltrimethoxysilane‐modified SiO₂ particles, and were characterized by optical microscopy, scanning electron microscopy, Fourier transformation infrared spectrum, thermogravimetric analysis (TGA), and energy dispersive X‐ray spectroscopy. The microspheres were templated by the Pickering droplets and the inner structure was affect by the proportion of crosslinking reagent. TGA result indicated that 60.3% of polymer in the shell was connected with SiO₂ by covalent bond which was formed by copolymerization of styrene and the reactive C?C group on SiO₂ stabilizer. Copyright © 2011 John Wiley & Sons, Ltd.     

Efficient and selective separation of metronidazole from human serum by using molecularly imprinted magnetic nanoparticles

Magnetic molecularly imprinted nanoparticles were prepared through surface‐initiated reversible addition fragmentation chain transfer polymerization by using metronidazole as a template. The molecularly imprinted magnetic nanoparticles were characterized by attenuated total reflection Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, transmission electron microscopy, X‐ray diffraction, and vibrating sample magnetometry. The adsorption characteristics were also investigated and the kinetics of the adsorption of metronidazole on the imprinted nanoparticles were described by the second‐order kinetic model with the short equilibrium adsorption time (30 min). The adsorption isotherm was well matched with the Langmuir isotherm in which the maximum adsorption capacity was calculated to be 40.1 mg/g. Furthermore, the imprinted magnetic nanoparticles showed good selectivity as well as reusability even after six adsorption–desorption cycles. The imprinted magnetic nanoparticles were used as a sorbent for the selective separation of metronidazole from human serum. The recoveries of metronidazole from human serum changed between 97.5 and 99.8% and showed similar sensitivity as an enzyme‐linked immunoassay method. Therefore, the molecularly imprinted magnetic nanoparticles might have potential application for the selective and reliable separation of metronidazole from biological fluids in clinical applications.     

Selective solid phase extraction of a drug lead compound using molecularly imprinted polymers prepared by the target analogue approach

Summary Molecularly imprinted polymers have been evaluated at the sample clean-up stage in the analysis of a drug lead compound. In order to circumvent quantification problems related to bleeding of the template, a structurally related analogue of the latter was used. This was selected based on criteria related to interaction site location, solubility, availability and stability of the analogue. Selection of suitable polymerisation conditions was then made using a small batch format (ca. 50 mg) and rapid assessment of binding in the equilibrium mode. It was found that the amount of template could be greatly reduced compared to the conventional protocol, requiring only 5 μmol of template per gram of polymer without seriously compromising the performance of the materials for chromatographic or SPE applications.     

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.     

Comparative study of capsaicin molecularly imprinted polymers prepared by different polymerization methods

In this study, the molecularly imprinted polymers (MIPs) of capsaicin are prepared by bulk polymerization (MIPs1), precipitation polymerization (MIPs2), and surface imprinting technology based on SiO₂/Fe₃O₄ particles (MIPs3), respectively. MIPs are characterized by scanning electron microscopy and fourier transform infrared spectroscopy. The adsorption kinetics and thermodynamics of these composites are also investigated to estimate their capacity to rebind capsaicin. The adsorption kinetics show that the adsorption process of MIPs1 is fitted to pseudo first‐order kinetic model, while the kinetic properties of MIPs2 and MIPs3 are well described by pseudo second‐order kinetic model. Adsorption thermodynamics analysis indicated that there are two kinds of binding sites with different affinity in each MIPs, whereas only one kind of binding site in non‐imprinted polymers. All adsorption isotherms of MIPs are fitted to Freundlich models, illustrated that binding sites are distributed heterogeneously in the surface of the materials, and the adsorption might occur in the multimolecular layers. Comparisons of experimental data of three MIPs are achieved and the results show that MIPs3 has the best affinity and absorption capacity to capsaicin. Moreover, the MIPs3 maintain the magnetic properties of Fe₃O₄ particles, which will be applied to the rapid separation of capsaicin from chili peppers samples. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 157–164     

Preparation of magnetic molecularly imprinted polymers by atom transfer radical polymerization for the rapid extraction of avermectin from fish samples

A novel and highly efficient approach to obtain magnetic molecularly imprinted polymers is described to detect avermectin in fish samples. The magnetic molecularly imprinted polymers were synthesized by surface imprinting polymerization using magnetic multiwalled carbon nanotubes as the support materials, atom transfer radical polymerization as the polymerization method, avermectin as template, acrylamide as functional monomer, and ethylene glycol dimethacrylate as crosslinker. The characteristics of the magnetic molecularly imprinted polymers were assessed by using transmission electron microscopy, Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, vibrating sample magnetometry, X‐ray diffraction, and thermogravimetric analysis. The binding characteristics of magnetic molecularly imprinted polymers were researched through isothermal adsorption experiment, kinetics adsorption experiment, and the selectivity experiment. Coupled with ultra high performance liquid chromatography and tandem mass spectrometry, the extraction conditions of the magnetic molecularly imprinted polymers as adsorbents for avermectin were investigated in detail. The recovery of avermectin was 84.2–97.0%, and the limit of detection was 0.075 μg/kg. Relative standard deviations of intra‐ and inter‐day precisions were in the range of 1.7–2.9% and 3.4–5.6%, respectively. The results demonstrated that the extraction method not only has high selectivity and accuracy, but also is convenient for the determination of avermectin in fish samples.