Preparation of molecularly imprinted polymers based on magnetic nanoparticles for the selective extraction of protocatechuic acid from plant extracts

In this study, highly selective core–shell molecularly imprinted polymers on the surface of magnetic nanoparticles were prepared using protocatechuic acid as the template molecule. The resulting magnetic molecularly imprinted polymers were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, and vibrating sample magnetometry. The binding performances of the prepared materials were evaluated by static and selective adsorption. The binding isotherms were obtained for protocatechuic acid and fitted by the Langmuir isotherm model and Freundlich isotherm model. Furthermore, the resulting materials were used as the solid‐phase extraction materials coupled to high‐performance liquid chromatography for the selective extraction and detection of protocatechuic acid from the extracts of Homalomena occulta and Cynomorium songaricum with the recoveries in the range 86.3–102.2%.     

Preparation of magnetic surface molecularly imprinted polymers for the selective extraction of triazines in environmental water samples

ABSTRACT

In this work, a magnetic molecularly imprinted polymer (Fe₃O₄@SiO₂@MIPs) was prepared via a surface-imprinted method for the determination of the triazines in environmental water samples combined with high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). The Fourier transform infrared spectroscopy (FTIR) and vibrating sample magnetometer showed that the Fe₃O₄@SiO₂@MIPs was successfully synthesised and exhibited superparamagnetism. The isotherm adsorption, selectivity and adsorption kinetics experiments showed that the Fe₃O₄@SiO₂@MIPs exhibited excellent specific recognition and fast adsorption equilibrium for triazines. The adsorption process is spontaneous and endothermic. The isotherm adsorption was consistent with Scatchard model and adsorption kinetic fit pseudo-second-order kinetic model. Under the optimised adsorption conditions, the Fe₃O₄@SiO₂@MIPs was directly used to selectively enrich six triazines in environmental water samples. The enrichment volume was up to 500 mL, and the matrix effects were down to 0.7–12.4%. The built method has excellent linearities in the range of 0.25–500 ng L^?1 with R² in the range of 0.998–0.999, lower limit of detections (0.02–0.08 ng L^?1) and higher precision (2.4–7.2%). The Fe₃O₄@SiO₂@MIPs is expected to be widely applied to the direct enrichment of triazines in bulk environmental water samples.     

水杨酸分子印迹电化学传感器的制备及其性能研究

以水杨酸作为模板分子,通过原位聚合法,在玻碳电极表面合成了水杨酸分子印迹聚合物膜,并用方波伏安法对该印迹电极进行了分析研究.当吸附时间为7 min时,印迹电极对水杨酸浓度响应的线性范围为1.0×10-5~2.6×10-5mol/L,检出限(S/N=3)为2.0×10-6mol/L,同一支印迹电极对水杨酸响应值的RSD为...     

Magnetic molecularly imprinted polymers for selective extraction and determination of naphthols

Microchimica Acta - The authors describe a magnetic molecular imprinted polymer (MMIP) for the extraction and detection of naphthols synthesized by surface imprinting technology using 1-naphthol as...     

Towards ochratoxin A selective molecularly imprinted polymers for solid-phase extraction

Molecularly imprinted polymers (MIPs) displaying selective binding properties for the mycotoxin ochratoxin A (OTA) in polar/protic media were prepared. Crucial to the success of these efforts was the implementation of rationally designed OTA mimics as templates and a set of novel basic and neutral functional monomers, allowing the maximization of the template-functional monomer association via ion-pairing, hydrophobic and steric interactions. MIPs prepared with a 20:1:1:3 molar ratio of cross-linking agent, template mimic, basic functional monomer and hydrophobic auxiliary monomer produced polymers with superior recognition properties compared to materials generated with other stoichiometries. Chromatographic evaluation using the OTA mimics, OTA and a set of structurally closely related compounds as analytes revealed pronounced substrate selectivity of these MIPs in polar/protic media, the templates and OTA being bound with significantly higher affinities. Complementary substrate selectivities/affinities were observed in aprotic and apolar solvents. The possibility of solvent-dependent tuning of substrate selectivity/affinity and the high binding capacity recommend the developed MIPs as promising solid-phase extraction adsorbents for clean-up and pre-concentration of OTA from various biologically relevant matrices.     

Highly selective stir bar coated with dummy molecularly imprinted polymers for trace analysis of bisphenol A in milk

A water compatible molecularly imprinted polymers (MIPs) coated stir bar for bisphenol A(BPA) was prepared with 3,3',5,5'-tetrabromobisphenol A as the dummy template molecule in this study. The dummy molecularly imprinted polymers coated stir bar (DMIPs-SB) showed better selectivity than the bars coated with polydimethylsiloxane or non-imprinted polymers when used to extract BPA and its three analogues. The saturated adsorption amount of the DMIPs coating was 3.0 times over that of the non-imprinted polymers coating. To achieve the optimum extraction performance, several parameters, including extraction and desorption time, pH value, adsorption temperature and stirring speed were investigated. The high-performance liquid chromatography combined with the DMIPs-SB was employed in the analysis of BPA in aqueous solution. The linear range of BPA concentration in aqueous medium was 0.0228-2.28 ng/mL with correlation coefficient of 0.9994 and the detection limit was about 6.84 × 10(-3) ng/mL based on three times ratio of signal to noise. This method was directly applied to the determination of trace BPA in milk with satisfactory results.     

三聚氰胺磁性分子印迹聚合物材料的制备及性能表征

利用溶剂热法通过控制反应时间和温度制得了分散性好和磁性强的Fe3O4,并利用溶胶凝胶法制备得到包覆SiO2的磁性微球(Fe3O4@SiO2)。以三聚氰胺为模板分子,甲基丙烯酸(MAA)为单体,采用本体聚合法制备了磁性分子印迹聚合物(MMIPs)。通过静态吸附实验表明,MMIPs对三聚氰胺的饱和吸附量高达10.22μg/mg,是磁性非印迹聚合物(MNIPs)的1.62倍。粒子扩散模型、Elovich模型和动态吸附实验表明所制得的MMIPs有较好的吸附性能。     

Solid-phase extraction using molecularly imprinted polymers for selective extraction of a mycotoxin in cereals

The aim of this work was to develop a method for the clean-up of a mycotoxin, i.e. Ochratoxin A (OTA), from cereal extracts employing a new molecularly imprinted polymer (MIP) as selective sorbent for solid-phase extraction (SPE) and to compare with an immunoaffinity column. A first series of experiments was carried out in pure solvents to estimate the potential of the imprinted sorbent in terms of selectivity studying the retention of OTA on the MIP and on a non-imprinted polymer using conventional crushed monolith. The selectivity of the MIP was also checked by its application to wheat extracts. Then, after this feasibility study, two different formats of MIP: crushed monolith and micro-beads were evaluated and compared. Therefore an optimization procedure was applied to the selective extraction from wheat using the MIP beads. The whole procedure was validated by applying it to wheat extract spiked by OTA at different concentration levels and then to a certified contaminated wheat sample. Recoveries close to 100% were obtained. The high selectivity brought by the MIP was compared to the selectivity by an immunoaffinity cartridge for the clean-up of the same wheat sample. The study of capacity of both showed a significant higher capacity of the MIP.     

Preparation of monodisperse magnetic surface molecularly imprinted polymers for selective recognition of lincomycin hydrochloride in milk

Monodisperse magnetic surface molecularly imprinted polymers (M-MIPs) with a specificity for lincomycin hydrochloride (LIN) were successfully prepared using surface-initiated atom transfer radical polymerization on the monodisperse magnetic polymer (vinylbenzylchloride/divinylbenzene) (Fe₃O₄/P_VBC/DVB) with LIN as a template molecule and 4-vinyl pyridine as the functional monomer. The Fe₃O₄ magnetic nanoparticles embedded itself in the micropores of polymer (P_VBC/DVB) by reversibly swelling adsorption method in which the pores of the polymer are swollen by the solvent, and then the Fe₃O₄ magnetic nanoparticles enter the pores, and as the solvent evaporates the pores of the polymer back to their original size, and Fe₃O₄ magnetic nanoparticles are left in the pores. The composition and magnetic properties of the polymer were characterized using scanning elemental microscopy analysis, X-ray diffraction, Surface element analysis and vibrating sample magnetometer analysis. The results of this study showed that the M-MIPs had good specific recognition ability for LIN. The imprinting factor is 3.72. The specific recognition capability of the polymers was affirmed by high performance liquid chromatography analysis. The spiked recovery was 94.3%–98.2% with RSD ≤ 3.7%, and the minimum detection limit is 15.0?ng/g (S/N?=?3) indicating that this material has application value in the pretreatment of complex samples.     

Citrinin selective molecularly imprinted polymers for SPE

Molecularly imprinted polymers (MIPs) for citrinin (Cit) with 1‐hydroxy‐2‐naphthoic acid (HNA) as mimic template were prepared and the molecularly imprinted SPE method was developed for the detection of Cit in rice with HPLC. The adsorption properties of HNA and Cit on the MIPs and nonimprinted polymers were investigated. It proved that MIPs showed higher selectivity adsorption to HNA and Cit than nonimprinted polymers were. The recoveries of Cit in rice were in the range of 86.7–97.7%. The spiked rice samples and five rice samples in Beijing market were detected using molecularly imprinted SPE method and satisfied results were obtained as discussed in this article.     

Water-compatible molecularly imprinted polymers for selective extraction of ciprofloxacin from human urine

Water-compatible molecularly imprinted polymers (MIPs) were prepared in water-methanol systems for selective extraction and separation of ciprofloxacin from human urine samples. Molecular recognition properties, binding capability, and chromatographic applications of the MIPs were evaluated and the results revealed the obtained MIPs have high affinity for ciprofloxacin in aqueous environment and the selectivity can be easily controlled by adjusting the pH of mobile phase. After centrifugation, the urine samples were directly injected into the MIPs column and ciprofloxacin could be selectively retained on the column while other biological matrixes were quickly washed out. Good linearity was obtained from 0.1 to 100 mg L(-1) (r=0.999) with the relative standard deviations less than 3.6%. The limit of detection of the method was 0.03 microg/mL and the recoveries were more than 94.5% at three different concentrations. Moreover, by increasing the injection volume, the detection limits of the method could be improved more than 100-folds.     

Synthesis and characterization of molecularly imprinted polymers for selective solid-phase extraction of pseudoephedrine

Molecular imprinted solid-phase extraction (MISPE) is a well known technique for the selective extraction and pre-concentration of analytes, are present at low levels in chemically complex materials. Herein, water-soluble, molecularly imprinted polymers (MIP) were prepared for solid-phase extraction of pseudoephedrine hydrochloride (PSE), which was monitored at 256 nm by the UV spectroscopy. MISPE conditions were optimized to allow the selective and determination of PSE in aqueous samples and composite materials, such as biological fluids and human urine. MIP was prepared by precipitation polymerization method, using methacrylic acid as a functional monomer and ethylene glycol dimethacrylate as a cross-linking agent in either acetonitrile or chloroform. The results suggest that the obtained MISPE exhibits high affinity for PSE, and the imprinted polymer demonstrates much higher efficiency than a non-imprinted polymer (NIP). The imprinting-induced extraction was confirmed by the determination of recovery values for NIP (4%) and MIP (80%) polymers, respectively. The binding capacity of the MIP for PSE was found of 47.6 mg g⁻¹.     

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.     

核壳结构的萘夫西林磁性分子印迹聚合物微球的制备及性能

以表面修饰双键的Fe₃O₄@SiO₂纳米颗粒为基体,以萘夫西林(nafcillin)为模板,甲基丙烯酸(MAA)为单体,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,采用三步升温聚合法合成了核壳结构的萘夫西林磁性分子印迹聚合物。采用傅里叶变换红外光谱仪(FT-IR)、透射电子显微镜(TEM)、X射线衍射仪(XRD)和振动样品磁强计(VSM)对制备的印迹聚合物微球进行了表征,得到的磁性印迹聚合物微球的粒径在320 nm左右,大小均匀,分散性较好,可以在外加磁场下与溶剂实现快速分离。对磁性印迹和非印迹聚合物进行了吸附性能研究,结果表明该印迹聚合物微球对模板分子具有很高的吸附容量(50.7 mg/g),特异性识别性能良好(印迹因子为2.46),有望应用于实际样品中萘夫西林残留量的富集分析。     

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.     

片段/虚拟分子印迹聚合物的应用新进展

分子印迹聚合物(MIPs)是通过模拟酶与底物或抗原抗体特异性结合原理而制备的高分子聚合物,以其结构预定性、识别特异性、制备简便、成本低、耐受性强等优点而被广泛用于样品前处理、传感分析、生物医药、环境/食品分析等多个领域。目前已发展多种策略用于MIPs制备,达到简化制备过程或提高聚合物性能等目的,极大拓宽了MIPs的应用范围。对各种先进印迹策略及其组合使用的探索已成为MIPs制备的研究热点之一。其中,片段印迹策略和虚拟模板印迹策略备受青睐。片段印迹策略是选择目标分子中含有特定官能团的一部分(片段结构)作为模板进行印迹,通过对片段的识别达到对整个分子的识别,能够克服某些目标物不易获得或体积较大不适合作为模板的问题,为印迹易失活、易传染的目标物及整体印迹困难的大分子提供可行的方法。虚拟模板印迹策略是选用与目标物特异性结构相似或相同的其他物质代替目标物作为模板制备MIPs,可在很大程度上解决模板不易获得或较昂贵等问题,以及避免模板可能泄漏对结果造成的影响,尤其适用于目标物造价高、具有感染性、易燃易爆、易降解等不适合作为模板分子的情况。该文选取了最近4年发表在ACS、Elsevier、RSC等数据库约20篇相关文献,综述了片段/虚拟MIPs(FMIPs/DMIPs)的应用新进展。首先,针对蛋白质和微生物检测以及哺乳动物细胞印迹,介绍了FMIPs在生物医药领域的应用,另外介绍了FMIPs在食品分析领域的研究进展。随后,介绍了DMIPs在样品前处理和传感分析领域的应用。在样品前处理中,DMIPs主要作为固相萃取吸附剂进行装柱固相萃取、分散固相萃取、磁固相萃取、基质固相分散萃取等,或作为分子印迹膜材料,用于选择性萃取和富集分离样品中的目标分析物。在传感分析领域,DMIPs主要作为传感器的传感和转导元件,提高化学发光或荧光检测等方法的灵敏度和准确度。最后,对片段印迹和虚拟模板印迹策略的优缺点、区别与联系进行了总结,并展望了这两种策略的发展与应用前景。     

Rationally designed molecularly imprinted polymers for selective extraction of methocarbamol from human plasma

Molecularly imprinted polymers (MIPs) with high selectivity toward methocarbamol have been computationally designed and synthesized based on the general non-covalent molecular imprinting approach. A virtual library consisting of 18 functional monomers was built and possible interactions between the template and functional monomers were investigated using a semiempirical approach. The monomers with the highest binding scores were then considered for additional calculations using a more accurate quantum mechanical (QM) calculation exploiting the density functional theory (DFT) at B3LYP/6-31G(d,p) level. The cosmo polarizable continuum model (CPCM) was also used to simulate the polymerization solvent. On the basis of computational results, acrylic acid (AA) and tetrahydrofuran (THF) were found to be the best choices of functional monomer and polymerization solvent, respectively. MIPs were then synthesized by the precipitation polymerization method and used as selective adsorbents to develop a molecularly imprinted solid-phase extraction (MISPE) procedure before quantitative analysis. After MISPE the drug could be determined either by differential pulse voltammetry (DPV), on a glassy carbon electrode modified with multiwalled-carbon nanotubes (GC/MWNT), or high performance chromatography (HPLC) with UV detection. A comparative study between MISPE-DPV and MISPE-HPLC-UV was performed. The MISPE-DPV was more sensitive but both techniques showed similar accuracy and precision.     

Preparation and performance valuation of high selective molecularly imprinted polymers for malachite green

Molecular imprinting is a technology that facilitates the production of artificial receptors toward compounds of interest. In this study, we prepared a series of molecularly imprinted polymers (MIPs) by precipitation polymerization for the purpose of binding specifically to malachite green (MG). The presence of monomer–template solution complexes in non-covalent MIPs systems had been verified by UV-spectrometric detection and molecular dynamics simulations. The synthesized parameters were, respectively, optimized and the optimal conditions for the efficient adsorption property were as follows: template: MG, 1 mmol; functional monomer: methacrylic acid (MAA), 8 mmol; cross-linker: ethylene glycol dimethacryllate, 16 mmol; and porogen: acetonitrile, 30 mL. Fourier transform infrared spectroscopy and nitrogen adsorption experiments were used to characterize the MIPs. Scatchard analysis was used for estimation of the dissociation constants and maximum amounts of binding sites. The polymer based on MAA had two classes of heterogeneous binding sites characterized by two values of K _D and B _max: K _D = 14.10 μmol L^?1 and B _max = 1.37 μmol g^?1 for the higher affinity binding sites, and K _D = 384.62 μmol L^?1 and B _max = 24.77 μmol g^?1 for the lower affinity binding sites. The specificity of MIPs on SPE column was evaluated by rebinding the other structurally similar compounds. The results indicated that the imprinted polymers exhibited an excellent stereo-selectivity toward MG.     

替代模板分子印迹聚合物的制备及其用于人尿、牛血清和啤酒中7种双酚类物质的选择性固相萃取

以酚酞(PP)为替代模板,采用本体聚合法制备了选择性识别7种双酚类物质(BPs)的分子印迹聚合物(MIP)。将制备的PP-MIP用作固相萃取(SPE)填料,成功应用于人尿、牛血清和啤酒样品中7种BPs的分离净化。建立了同时测定人尿、牛血清和啤酒样品中的7种BPs的MIP-SPE-HPLC分析方法。3种样品中7种BPs的方法检出限范围均为1.2~2.0 μg/L。结果表明,7种BPs在0.02~2 mg/L范围内线性关系良好,相关系数(r)大于0.9998;空白样品中加标水平为100和500 μg/L的回收率范围为90.1%~107.1%,相对标准偏差(RSD)不高于8.1%。该方法简便、准确、灵敏、可靠,可用于人尿、牛血清和啤酒中7种BPs的快速检测。     

Facile preparation of magnetic molecularly imprinted polymers for the selective extraction and determination of dexamethasone in skincare cosmetics using HPLC

Dexamethasone‐imprinted polymers were fabricated by reversible addition–fragmentation chain transfer polymerization on the surface of magnetic nanoparticles under mild polymerization conditions, which exhibited a narrow polydispersity and high selectivity for dexamethasone extraction. The dexamethasone‐imprinted polymers were characterized by scanning electron microscopy, transmission electron microscope, Fourier transform infrared spectroscopy, X‐ray diffraction, energy dispersive spectrometry, and vibrating sample magnetometry. The adsorption performance was evaluated by static adsorption, kinetic adsorption and selectivity tests. The results confirmed the successful construction of an imprinted polymer layer on the surface of the magnetic nanoparticles, which benefits the characteristics of high adsorption capacity, fast mass transfer, specific molecular recognition, and simple magnetic separation. Combined with high‐performance liquid chromatography, molecularly imprinted polymers as magnetic extraction sorbents were used for the rapid and selective extraction and determination of dexamethasone in skincare cosmetic samples, with the accuracies of the spiked samples ranging from 93.8 to 97.6%. The relative standard deviations were less than 2.7%. The limit of detection and limit of quantification were 0.05 and 0.20 μg/mL, respectively. The developed method was simple, fast and highly selective and could be a promising method for dexamethasone monitoring in cosmetic products.