Preparation of l‐phenylalanine‐imprinted solid‐phase extraction sorbent by Pickering emulsion polymerization and the selective enrichment of l‐phenylalanine from human urine

A novel l‐ phenylalanine molecularly imprinted solid‐phase extraction sorbent was synthesized by the combination of Pickering emulsion polymerization and ion‐pair dummy template imprinting. Compared to other polymerization methods, the molecularly imprinted polymers thus prepared exhibit a high specific surface, large pore diameter, and appropriate particle size. The key parameters for solid‐phase extraction were optimized, and the result indicated that the molecularly imprinted polymer thus prepared exhibits a good recovery of 98.9% for l‐ phenylalanine. Under the optimized conditions of the procedure, an analytical method for l‐ phenylalanine was well established. By comparing the performance of the molecularly imprinted polymer and a commercial reverse‐phase silica gel, the obtained molecularly imprinted polymer as an solid‐phase extraction sorbent is more suitable, exhibiting high precision (relative standard deviation 3.2%, n = 4) and a low limit of detection (60.0 ± 1.9 nmol·L^?1) for the isolation of l‐ phenylalanine. Based on these results, the combination of the Pickering emulsion polymerization and ion‐pair dummy template imprinting is effective for preparing selective solid‐phase extraction sorbents for the separation of amino acids and organic acids from complex biological samples.     

Highly selective separation and detection of cyromazine from seawater using graphene oxide based molecularly imprinted solid‐phase extraction

A novel molecularly imprinted polymer based on graphene oxide was prepared as a solid‐phase extraction adsorbent for the selective adsorption and extraction of cyromazine from seawater samples. The obtained graphene oxide molecularly imprinted polymer and non‐imprinted polymer were nanoparticles and characterized by scanning electron microscopy. The imprinted polymer showed higher adsorption capacity and better selectivity than non‐imprinted polymer, and the maximum adsorption capacity was 14.5 mg/g. The optimal washing and elution solvents for molecularly imprinted solid phase extraction procedure were 2 mL of acetonitrile/water (80:20, v/v) and methanol/acetic acid (70:30, v/v), respectively. The recoveries of cyromazine in the spiked seawater samples were in the range of 90.3–104.1%, and the relative standard deviation was <5% (n = 3) under the optimal procedure and detection conditions. The limit of detection of the proposed method was 0.7 μg/L, and the limit of quantitation was 2.3 μg/L. Moreover, the imprinted polymer could keep high adsorption capacity for cyromazine after being reused six times at least. Finally, the synthesized graphene oxide molecularly imprinted polymer was successfully used as a satisfied sorbent for high selectivity separation and detection of cyromazine from seawater coupled with high‐performance liquid chromatography.     

Surface‐imprinted magnetic nanoparticles for the selective enrichment and fast separation of fluoroquinolones in human serum

Surface enrofloxacin‐imprinted magnetic nanoparticles were prepared for the selective recognition and fast separation of fluoroquinolones in human serum by surface‐initiated reversible addition fragmentation chain transfer polymerization. The surface morphology and imprinted behavior were investigated and optimized. The living/controlled nature of reversible addition‐fragmentation chain transfer polymerization reaction allowed the successful construction of well‐defined imprinted polymer layer outside the Fe₃O₄ core. Such molecularly imprinted polymers exhibited superparamagnetic properties and specific recognition toward fluoroquinolones. Combined with reversed‐phase high‐performance liquid chromatography, the prepared molecularly imprinted polymers were used for the selective enrichment and analysis of fluoroquinolones in human serum samples. The recoveries of four fluoroquinolones were 86.8–95.3% with relative standard deviations of 2.0–6.8% (n  = 3). Such magnetic molecularly imprinted polymers have great prospects in the separation and enrichment of trace analysts in complex biological samples.     

Theoretical and experimental studies on the performances of barbital‐imprinted systems

By using density functional theory, we studied the interaction process between barbital and 2‐vinyl‐4,6‐diamino‐1,3,5‐triazine in acetonitrile at 333 K. Barbital and 2‐vinyl‐4,6‐diamino‐1,3,5‐triazine were used as the template and functional monomer, respectively. The molecularly imprinted polymer microspheres containing barbital and 2‐vinyl‐4,6‐diamino‐1,3,5‐triazine were synthesized through precipitation polymerization. After removing the template molecule barbital, the average diameter of the obtained molecularly imprinted polymers was 1.45 μm. By optimizing the molar ratio of barbital and the 2‐vinyl‐4,6‐diamino‐1,3,5‐triazine, the resulting molecularly imprinted polymers showed the highest adsorption for the barbital. The analysis of the Scatchard plot revealed that the dissociation constant (K_d) and apparent maximum adsorption quantity (Q_max) of the molecularly imprinted polymers were 30.69 mg/L and 8.68 mg/g, respectively. The study of selective adsorption showed that molecularly imprinted polymers exhibited higher selectivity for barbtital than that for 1,3‐dimethyl barbituric acid and pentobarbital. Herein, the studies can provide theoretical and experimental references for the barbital‐imprinted system.     

Preparation of magnetic molecularly imprinted polymer for dispersive solid‐phase extraction of valsartan and its determination by high‐performance liquid chromatography: Box‐Behnken design

In this work, core/shell magnetic molecularly imprinted polymer nanoparticles were synthesized for extraction and pre‐concentration of valsartan from different samples and then it was measured with high‐performance liquid chromatography. For preparation of molecularly imprinted polymer nanoparticles, Fe₃O₄ nanoparticles were coated with tetraethyl orthosilicate and then functionalized with 3‐(trimethoxysilyl) propyl methacrylate. In the next step, molecularly imprinted polymer nanoparticles were synthesized under reflux and distillation conditions via polymerization of methacrylic acid, valsartan (as a template), azobisisobutyronitrile and ethylene glycol dimethacrylate as cross linking. The properties of molecularly imprinted polymer nanoparticle were investigated by FTIR spectroscopy, field emission scanning electron microscopy, and X‐ray diffraction. Box‐Behnken design with the aid of desirability function was used for optimizing the effect of variables such as the amounts of molecularly imprinted polymer nanoparticles, time of sonication, pH, and volume of methanol on the extraction percentage of valsartan. According to the obtained results, the affecting variables extraction condition were set as 10 mg of adsorbent, 16 min for sonication, pH = 5.5 and 0.6 mL methanol. The obtained linear response (r² > 0.995) was in the range of 0.005–10 µg/mL with detection limit 0.0012 µg/mLand extraction recovery was in the range of 92–95% with standard deviation less than 6% (n = 3).     

Electrosynthesis of Molecularly Imprinted Poly‐o‐phenylenediamine on MWCNT Modified Electrode for Selective Determination of Meldonium

In this study, a molecularly imprinted polymer (MIP) was synthesized by electrochemical polymerization and used to construct an electrochemical sensor for determination of meldonium (MEL) selectively for the first time. The polymer film was generated by using o‐phenylenediamine (o‐PD) as a monomer on the surface of carboxylic acid functionalized multiwalled carbon nanotube (MWCNT) modified pencil rod electrode in the presence of MEL as a template. MEL imprinted (MEL‐imp) and non‐imprinted (N‐imp) polymer films and coated electrodes were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), profilometry, electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Voltammetric measurements were carried out in a ferrocyanide/ferricyanide redox probe solution for MEL‐imp and N‐imp electrodes in the presence and absence of template molecule. The decrease in peak current of redox probe was linear with the concentration of MEL in the range of 0.1–5 μg/mL and the limit of detection (3 s/b) was found to be 0.066 μg/mL under optimized experimental conditions. The proposed sensor was successfully applied for selective determination of MEL in human urine sample with long term stability and good reproducibility.     

One‐pot synthesis of surface‐functionalized molecularly imprinted polymer microspheres by iniferter‐induced “living” radical precipitation polymerization

This article describes for the first time the development of a new polymerization technique by introducing iniferter‐induced “living” radical polymerization mechanism into precipitation polymerization and its application in the molecular imprinting field. The resulting iniferter‐induced “living” radical precipitation polymerization (ILRPP) has proven to be an effective approach for generating not only narrow disperse poly(ethylene glycol dimethacrylate) microspheres but also molecularly imprinted polymer (MIP) microspheres with obvious molecular imprinting effects towards the template (a herbicide 2,4‐dichlorophenoxyacetic acid (2,4‐D)), rather fast template rebinding kinetics, and appreciable selectivity over structurally related compounds. The binding association constant K_a and apparent maximum number N_max for the high‐affinity sites of the 2,4‐D imprinted polymer were determined by Scatchard analysis and found to be 1.18 × 10⁴ M^?1 and 4.37 μmol/g, respectively. In addition, the general applicability of ILRPP in molecular imprinting was also confirmed by the successful preparation of MIP microspheres with another template (2‐chloromandelic acid). In particular, the living nature of ILRPP makes it highly useful for the facile one‐pot synthesis of functional polymer/MIP microspheres with surface‐bound iniferter groups, which allows their direct controlled surface modification via surface‐initiated iniferter polymerization and is thus of great potential in preparing advanced polymer/MIP materials. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3217–3228, 2010     

Synthesis and characterization of photo‐responsive magnetic molecularly imprinted microspheres for the detection of sulfonamides in aqueous solution

A dual responsive molecularly imprinted polymer sensitive to both photonic and magnetic stimuli was successfully prepared for the detection of four sulfonamides in aqueous media. The photoresponsive magnetic molecularly imprinted polymer was prepared by surface imprinting polymerization using superparamagnetic Fe₃O₄ nanoparticles functionalized with a silica layer as a support, water‐soluble 4‐[(4‐methacryloyloxy)phenylazo]benzenesulfonic acid as the functional monomer, and sulfadiazine as the template. The magnetic molecularly imprinted polymers showed specific affinity to sulfadiazine and its structural analogs in aqueous media. Upon alternate irradiation at 365 and 440 nm, the quantitative bind and release of the four sulfonamides by magnetic molecularly imprinted polymers occurred. Furthermore, the prepared magnetic molecularly imprinted polymers were used as solid‐phase extraction material selectively extracted the four sulfonamides from water samples with good recoveries. Thus, a simple, convenient, and reliable detection method for sulfonamides in the environment based on responsive magnetic molecularly imprinted polymers was successfully established.     

Deep eutectic solvents skeleton typed molecularly imprinted chitosan microsphere coated magnetic graphene oxide for solid‐phase microextraction of chlorophenols from environmental water

Novel molecularly imprinted chitosan microspheres were prepared on the surface of magnetic graphene oxide, with deep eutectic solvents both as a functional monomer and template. The prepared molecularly imprinted chitosan microspheres‐magnetic graphene oxide was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, Brunauer‐Emmett‐Teller surface area, thermogravimetric analysis were subsequently combined with solid‐phase micro‐extraction for simultaneous separation and enrichment of the extraction of chlorophenols from environmental water. Factors affecting the extraction efficiency of chlorophenols were optimized using response surface methodology. The actual extraction capacities under the optimal conditions (liquid to solid ratio = 3, cycles of adsorption/desorption = 5, 40°C extraction temperature, and extraction time for 35 min) were 86.90 mg/g. Compared to the traditional materials, the molecularly imprinted chitosan microspheres‐magnetic graphene oxide produced higher selectivity and extraction capacity.     

Molecularly imprinted polymer coating on metal‐organic frameworks for solid‐phase extraction of fluoroquinolones from water

In this work, a novel surface molecularly imprinted polymer with high adsorption capacity, high adsorption rate, and high selectivity for fluoroquinolones was prepared on the surface of UiO‐66‐NH₂, which is a kind of metal‐organic framework. The surface morphology and adsorption properties of this molecularly imprinted polymer were investigated. The maximum adsorption capacity was 99.19 mg/g, and adsorption equilibrium was achieved within 65 s. Combined with reversed‐phase high‐performance liquid chromatography, the molecularly imprinted polymer was used to selectively enrich, separate and analyze fluoroquinolones present in lake water. The results showed that the recoveries of the four fluoroquinolones were 92.6–100.5%, and the relative standard deviations were 2.9–6.4% (n = 3). The novel molecularly imprinted polymer is an excellent adsorbent and has broad application prospects in the enrichment and separation of trace analytes in complex samples.     

Tailor‐made ion‐imprinted polymer based on functionalized graphene oxide for the preconcentration and determination of trace copper in food samples

A tailor‐made Cu(II) ion‐imprinted polymer based on large‐surface‐area graphene oxide sheets has been synthesized for the preconcentration and determination of trace copper from food samples by solid‐phase extraction. Attributed to the ultrahigh surface area and hydrophilicity of graphene oxide, the Cu(II) ion‐imprinted polymer prepared by the surface ion‐imprinting technique exhibited a high binding capacity and a fast adsorption rate under the optimized experimental conditions. In the static adsorption experiments, the maximum adsorption capacity of Cu(II) ion‐imprinted polymer is 109.38 mg/g at 25°C, which is much higher than that of the nonimprinted polymer (32.12 mg/g). Meanwhile, the adsorption is very rapid and equilibrium is reached after approximately 30 min. The adsorption mechanism is found to follow Langmuir adsorption model and the pseudo‐second‐order adsorption process. The Cu(II) ion‐imprinted polymer was used for extracting and detecting Cu(II) in food samples combined with graphite flame atomic adsorption spectrometry with high recoveries in the range of 97.6–103.3%. The relative standard deviation and limit of detection of the method were evaluated as 1.2% and 0.37 μg/L, respectively. The results showed that the novel absorbent can be utilized as an effective material for the selective enrichment and determination of Cu(II) from food samples.     

Magnetic molecularly imprinted composite for the selective solid‐phase extraction of p‐aminosalicylic acid followed by high‐performance liquid chromatography with ultraviolet detection

A new method for the selective extraction of p‐aminosalicylic acid from aqueous and urine samples has been developed using magnetic molecularly imprinted polymer nanoparticles before determination by high‐performance liquid chromatography. The Fe₃O₄ nanoparticles were first prepared through the chemical coprecipitation of Fe²⁺ and Fe³⁺ and then coated with a vinyl shell. Subsequently, a layer of molecularly imprinted polymers was grafted onto the vinyl‐modified magnetic nanoparticles by precipitation polymerization. FTIR spectroscopy, scanning electron microscopy, vibrating sample magnetometry, and thermogravimetric analysis were applied to characterize the sorbent properties. Moreover, the predominant parameters affecting the magnetic solid phase extraction such as sample pH, sorption and elution times, the amount of sorbent, and composition and volume of eluent were investigated thoroughly. The maximum sorption capacity of the imprinted polymer toward p‐aminosalicylic acid was 70.9 mg/g, which is 4.5 times higher than that of the magnetic nonimprinted polymer. The magnetic molecularly imprinted polymer nanoparticles were applied for the selective extraction of p‐aminosalicylic acid from aqueous and urine samples and satisfactory results were achieved. The results illustrate that magnetic molecularly imprinted polymer nanoparticles have a great potential in the extraction of p‐aminosalicylic acid from environmental and biological matrices.     

Surface‐Imprinted Nanofilaments for Europium‐Amplified Luminescent Detection of Fluoroquinolone Antibiotics

The development and characterization of novel, molecularly imprinted polymer nanofilament‐based optical sensors for the analysis of enrofloxacin, an antibiotic widely used for human and veterinary applications, is reported. The polymers were prepared by nanomolding in porous alumina by using enrofloxacin as the template. The antibiotic was covalently immobilized on to the pore walls of the alumina by using different spacers, and the prepolymerization mixture was cast in the pores and the polymer synthesized anchored onto a glass support through UV polymerization. Various parameters affecting polymer selectivity were evaluated to achieve optimal recognition, namely, the spacer arm length and the binding solvent. The results of morphological characterization, binding kinetics, and selectivity of the optimized polymer material for ENR and its derivatives are reported. For sensing purposes, the nanofilaments were incubated in solutions of the target molecule in acetonitrile/HEPES buffer (100 mM , pH 7.5, 50:50, v/v) for 20 min followed by incubation in a 10 mM solution of europium(III) ions to generate a europium(III)–enrofloxacin complex on the polymer surface. The detection event was based on the luminescence of the rare‐earth ion (λ_exc=340 nm; λ_em=612 nm) that results from energy transfer from the antibiotic excited state to the metal‐ion emitting excited state. The limit of detection of the enrofloxacin antibiotic was found to be 0.58 μM .     

Simultaneous determination of levofloxacin and ciprofloxacin in human urine by ionic‐liquid‐based,dual‐template molecularly imprinted coated graphene oxide monolithic solid‐phase extraction

A novel method was developed to simultaneously determine the ciprofloxacin and levofloxacin levels in human urine using an ionic‐liquid‐based, dual‐molecularly imprinted polymer‐coated graphene oxide solid‐phase extraction monolithic column coupled with high‐performance liquid chromatography. The molecularly imprinted monolithic column was prepared using ciprofloxacin and levofloxacin as templates, 1‐vinyl‐3‐ethylimidazolium bromide as the functional monomer, and graphene oxide as the core material. The resulting imprinted monoliths were characterized by scanning electron microscopy and fourier transform‐infrared spectroscopy. The efficiency and capacity of the ionic‐liquid‐based imprinted monolithic column were investigated by varying the synthesis conditions (ciprofloxacin/levofloxacin ratio and template/functional monomer/cross‐linker ratio). The solid‐phase extraction process was optimized by changing the washing and eluting conditions. The results suggested that the proposed ionic‐liquid‐based molecularly imprinted solid‐phase extraction monolithic‐high‐performance liquid chromatography method could separate ciprofloxacin and levofloxacin efficiently and simultaneously from human urine. The mean recoveries of ciprofloxacin and levofloxacin ranged from 89.2 to 93.8 and 86.7 to 94.6%, respectively. The intra‐ and interday relative standard deviation ranged from 0.9 to 3.2 and 0.8 to 2.9%, respectively. Under the optimized conditions, the recoveries of ciprofloxacin and levofloxacin were more than 93.8%.     

Facile preparation of polydopamine‐coated imprinted polymers on the surface of SiO2 for estrone capture in milk samples

Estrone molecularly imprinted polymers were synthesized through the self‐polymerization of dopamine on the surface of silica gels, which had the characteristics of mild polymerization conditions, simple reaction procedure and good specific recognition ability for estrone. The estrone molecularly imprinted polymers were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, elemental analysis and nitrogen adsorption–desorption tests. The characterization confirmed that the imprinted polymers were successfully grafted on the surface of silica gels. Through investigating the adsorption performance, the prepared estrone molecularly imprinted polymers exhibited high adsorption capacity, fast mass transfer, as well as excellent selectivity toward estrone. The estrone molecularly imprinted polymers as the solid‐phase extraction adsorbent coupled with high‐performance liquid chromatography was developed to determine estrone from the milk samples. The developed estrone molecularly imprinted polymer solid‐phase extraction with high‐performance liquid chromatography method exhibited satisfactory specificity, precision, accuracy and good linearity relationship in the range of 0.2–20 μg/mL. The developed method is simple, fast, effective and high specificity method and it provides a new method to detect the residues of estrone in animal foods.     

Solid‐phase extraction based on a molecularly imprinted polymer nanoshell at the surface of silica nanospheres for the specific enrichment and identification of alkaloids from Crinum asiaticum L. var. sinicum

A molecularly imprinted nanoshell on the surface of silica nanospheres was prepared for specific enrichment and identification of alkaloids from Crinum asiaticum L. var. sinicum . The nanoshell was synthesized by surface polymerization using lycorine as the template, acrylamide as the functional monomer, ethylene glycol dimethacrylate as the cross‐linker, 2′,2‐azobisisobutyronitrile as the initiator and acetonitrile as the pore‐forming agent. The core–shell nanospheres were characterized by transmission electron microscopy and infrared spectroscopy, and the results show that the nanoshell layer was homogeneously attached to the surface of vinyl‐modified SiO₂ nanospheres. The adsorption capacity of the nanospheres was estimated by binding equilibrium and adsorption kinetics experiments. The maximum adsorption amount of lycorine on the nanospheres was 6.68 μmol/g and the imprinting factor was nearly 2.5, indicating a good imprinting effect. The nanospheres were successfully applied in solid‐phase extraction for lycorine from Crinum asaticum L. var. sinicum and detection of target molecule in rat metabolites. The average recoveries of lycorine in Crinum asaticum L. var. sinicum extraction and rat metabolites were 93.5 ± 0.6% (n = 3) and 91.6 ± 1.9% (n = 3), respectively. This work provides a simple approach for the fabrication of a molecularly imprinted nanoshell at the surface of silica nanospheres‐based solid‐phase extraction for drug analysis.     

Selective extraction of morphine from biological fluids by magnetic molecularly imprinted polymers and determination using UHPLC with diode array detection

The determination of morphine concentration in the blood and urine is necessary for patients and recruitment purposes. Herein, a magnetic molecularly imprinted polymer for selective and efficient extraction of morphine from biological samples was synthesized by using a core–shell method. Fe₃O₄ nanoparticles were coated with SiO₂‐NH₂. The molecularly imprinted polymer was coated on the Fe₃O₄/SiO₂‐NH₂ surface by the copolymerization of methacrylic acid and ethylene glycol dimethacrylate in the presence of morphine as the template molecule. The morphological and magnetic properties of the polymer were investigated. Field‐emission scanning electron microscopy indicated that the prepared magnetic polymer is almost uniform. The saturation magnetization values of Fe₃O₄ nanoparticles, Fe₃O₄/SiO₂‐NH₂, and the magnetic polymer were 48.41, 31.69, and 13.02 emu/g, respectively, indicating that all the particles are superparamagnetic. Kinetics of the adsorption of morphine on magnetic polymer were well described by second‐order kinetic and adsorption processes and well fitted by the Langmuir adsorption isotherm, in which the maximum adsorption capacity was calculated as 28.40 mg/g. The recoveries from plasma and urine samples were in the range of 84.9–105.5 and 94.9–102.8%, respectively. By using the magnetic molecularly imprinted polymer, morphine can selectively, reliably, and in low concentration be determined in biological samples with high‐performance liquid chromatography and UV detection.     

A Novel Electrochemical Sensor for β2‐Agonists with High Sensitivity and Selectivity Based on Surface Molecularly Imprinted Sol‐gel Doped with Antimony‐Doped Tin Oxide

A novel strategy to improve the sensitivity of molecularly imprinted polymer (MIP) sensors was proposed for the determination of β₂‐agonists. The imprinted sol‐gel film was prepared by mixing silica sol with a functional monomer of antimony‐doped tin oxide (ATO) and a template of β₂‐agonists. ATO, which was embedded in the surface of the molecularly imprinted sol‐gel film, not only provides the excellent conductivity for biosensor but also increases the stability and the surface area of the MIP film. The imprinted sensor was characterised by field emission scanning electron microscope, fourier transform infrared spectroscopy and electrochemical methods. Under the optimal experimental conditions, the peak current was linear with the logarithm of the concentration of clenbuterol (CLB) in the range of 5.5 nM–6.3 µM, and a detection limit of 1.7 nM was obtained. Meanwhile, the electrochemical sensor showed excellent specific recognition of the template molecule among structurally similar coexisting substances. Furthermore, the proposed sensor was satisfactorily applied to determine β₂‐agonists in human serum samples. The good results indicated that highly effective molecularly imprinted sol‐gel films doped with ATO can be employed for other analytes.     

Synthesis of polydopamine‐coated graphene–polymer nanocomposites via RAFT polymerization

Graphene‐polymer nanocomposites have significant potential in many applications such as photovoltaic devices, fuel cells, and sensors. Functionalization of graphene is an essential step in the synthesis of uniformly distributed graphene‐polymer nanocomposites, but often results in structural defects in the graphitic sp² carbon framework. To address this issue, we synthesized graphene oxide (GO) by oxidative exfoliation of graphite and then reduced it into graphene via self‐polymerization of dopamine (DA). The simultaneous reduction of GO into graphene, and polymerization and coating of polydopamine (PDA) on the reduced graphene oxide (RGO) surface were confirmed with XRD, UV–Vis, XPS, Raman, TGA, and FTIR. The degree of reduction of GO increased with increasing DA/GO ratio from 1/4 to 4/1 and/or with increasing temperature from room temperature to 60 °C. A RAFT agent, 2‐(dodecylthiocarbonothioylthio)?2‐methylpropionic acid, was linked onto the surface of the PDA/RGO, with a higher equivalence of RAFT agent in the reaction leading to a higher concentration of RAFT sites on the surface. Graphene‐poly(methyl methacrylate), graphene‐poly(tert‐butyl acrylate), and graphene‐poly(N‐isopropylacrylamide) nanocomposites were synthesized via RAFT polymerization, showing their characteristic solubility in several different solvents. This novel synthetic route was found facile and can be readily used for the rational design of graphene‐polymer nanocomposites, promoting their applications. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3941–3949     

Innovative method for the enrichment of high‐polarity bioactive molecules present at low concentrations in complex matrices

Ginsenoside Rg1 is a valuable bioactive molecule but its high polarity and low concentration in complex mixtures makes it a challenge to separate Ginsenoside Rg1 from other saponins with similar structures, resulting in low extraction efficiency. The successful development of effective Rg1 molecularly imprinted polymers that exhibit high selectivity and adsorption may offer an improved method for the enrichment of active compounds. In this work, molecularly imprinted polymers were prepared with two different methods, precipitation polymerization or surface imprinted polymerization. Comparison of the adsorption abilities showed higher adsorption of the surface molecularly imprinted polymers prepared by surface imprinted polymerization, 46.80 mg/g, compared to the 27.74 mg/g observed for the molecularly imprinted polymers prepared by precipitation polymerization. Therefore, for higher adsorption of the highly polar Rg1, surface imprinted polymerization is a superior technique to make Rg1 molecularly imprinted polymers. The prepared surface molecularly imprinted polymers were tested as a solid‐phase extraction column to directionally enrich Rg1 and its analogues from ginseng tea and total ginseng extracts. The column with surface molecularly imprinted polymers showed higher enrichment efficiency and better selectivity than a C₁₈ solid‐phase extraction column. Overall, a new, innovative method was developed to efficiently enrich high‐polarity bioactive molecules present at low concentrations in complex matrices.