Development and application of molecularly imprinted polymers as solid-phase sorbents for erythromycin extraction

Six molecularly imprinted polymers (MIPs) of erythromycin (ERY) were prepared by noncovalent bulk polymerization using methacrylic acid (MAA) as the functional monomer. On the basis of binding analysis, the MIPs with 1:2 optimum ratio of template to MAA were selected for subsequent scanning electron microscopy and Brunauer–Emmett–Teller analyses, which indicated that the MIPs had more convergent porous structures than the nonimprinted polymers. The equilibrium binding experiments showed that the binding sites of MIPs were heterogeneous, with two dissociation constants of 0.005 and 0.63 mg mL⁻¹, respectively. Furthermore, the performance of the MIPs as solid-phase extraction (SPE) sorbents was evaluated, and the selectivity analysis showed that the MIPs could recognize ERY with moderate cross-reactivity for other macrolides. The overall investigation of molecularly imprinted SPE for cleanup and enrichment of the ERY in pig muscle and tap water confirmed the feasibility of utilizing the MIPs obtained as specific SPE sorbents for ERY extraction in real samples. Figure Schematic diagram of the preparation and application of the erythromycin imprinted molecularly imprinted polymers Suquan Song and Aibo Wu contributed equally to this work.     

Synthesis of surface molecularly imprinted silica micro-particles in aqueous solution and the usage for selective off-line solid-phase extraction of 2,4-dinitrophenol from water matrixes

Very severe reaction conditions are required in the conventional synthesis of molecularly imprinted polymers (MIPs), which is unfavorable to their applications in chemical separation and analysis. A simple surface molecular imprinting approach was developed to synthesize MIP-coated SiO₂ micro-particles in aqueous solutions. The ¹H NMR and UV-vis spectroscopic analysis indicated that via hydrogen bonding, the functional monomer (o-phenylenediamine) can associate with the target (template) 2,4-dinitrophenol (2,4-DNP), as a model compound of organic pollutants, to form a precursor in aqueous solution. The copolymerization of this precursor and the free monomer was performed in the aqueous suspension of surface modified SiO₂ particles, leading to the formation of MIP-coated SiO₂ micro-particles. The MIP-coated silica particles were characterized with FT-IR, TGA, and UV-vis solid-state reflection spectroscopy, and were further demonstrated to have high adsorption capacity, excellent selectivity and site accessibility for 2,4-DNP. The new absorbent was successfully used in solid-phase extraction (SPE) to selectively enrich and determine 2,4-DNP in aqueous samples. The experimental results indicated that the MIP-SPE column yielded recoveries higher than 92% with R.S.D. <2.8%, much better than the commercial C₁₈-SPE column, which produced a recovery less than 30% with R.S.D. <3.0%.     

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.     

Molecular imprinting of natural flavonoid antioxidants: application in solid-phase extraction for the sample pretreatment of natural products prior to HPLC analysis

As shown in the past years, SPE based on molecularly imprinted polymers (MIPs) may provide significant enhancement of selectivity in sample preparation and analyte preconcentration. The objective of this work was the fabrication of MIPs for the specific adsorption of rutin and quercetin. The two flavonoids were used as the template molecules for the preparation of MIP phases in a self-assembly (noncovalent) approach. The produced MIPs were validated with regard to the imprinting efficiency as media for LC and SPE. The retention behavior of several flavonoid compounds was studied using as stationary phases imprinted, control nonimprinted polymers, and commercial silica-based materials. MIPs were applied as materials for the selective SPE and preconcentration of the flavonoids from white and red wine, orange juice, and tea. The collected fractions were analyzed by high-pressure LC. MIP-SPE facilitated specific analyte isolation and effective sample clean-up. The results show that molecularly imprinted SPE can be a useful tool for the simple, selective, and cost-effective pretreatment of samples containing natural antioxidants.     

Molecularly Imprinted Polymers for Solid Phase Extraction

The combination of molecularly imprinted polymers (MIPs) and solid phase extraction (SPE) is reviewed. MIPs, which have high selectivity and affinity for a predetermined molecule (template), have been used as sorbents for SPE to selectively isolate analytes from biological, pharmaceutical, and environmental samples. Solid phase extraction with molecularly imprinted polymers (MIP–SPE) is a promising technique which allows specific analytes to be selectively extracted from complex matrices. This survey summarizes the characteristics, development and application of MIP–SPE in recent years. Existed problems and the future direction of MIP–SPE are also discussed.     

Synthesis and chromatographic evaluation of molecularly imprinted polymers prepared by the substructure approach for the class-selective recognition of glucuronides

Two series of molecularly imprinted polymers (MIPs) for the class-selective recognition of glucuronides have been prepared by using lipophilic substructures of the target analyte as template molecule and potent host monomers against oxyanions, that are expected to establish a strong stoichiometric interaction with the single carboxylic group of the template. The polymers were tested as stationary phases in liquid chromatography for specific recognition. A preliminary investigation of the imprinting properties of eleven MIPs was carried out, by comparing the retention time of the template and of structurally related compounds on the MIP column with that on the corresponding non-imprinted polymer (NIP). The two polymers showing the best performance were selected to further test cotinine, mycophenolic acid, testosterone and their respective glucuronides as model compounds. The high specificity obtained against glucuronides and the different chemical structure of the parent drug make the two MIPs class-selective imprinted receptors, also suitable for SPE application.     

Synthesis and evaluation of new lipomonosaccharide-imprinted polymers as MISPE supports

Molecular imprinted polymers (MIP) were prepared by the copolymerization of styrene (S) or methyl methacrylate (MMA) and methacrylic acid (MAA) using ethylene glycol dimethacrylate (EGDMA) as the crosslinker with molar ratios of [monomer]/[crosslinker] and [MAA]/[template] of 3:7 (to obtain a rigid structure) and 1:6 (to optimise hydrogen interactions), respectively. The polymerizations occurred in presence of the template molecule (MIP) - GlcNcouma - an amphiphilic monosaccharide. The same materials, non-imprinted polymers (NIP), were also prepared in absence of the template. These MIPs were characterized and used as SPE supports for selective enrichment. The results showed the correlation between retention efficiency and the porogen character of the polymerization solvent.     

Preparation and characterization of molecularly imprinted electropolymerized carbon electrodes

Molecularly imprinted polymers (MIPs) selective for fluorescein, rhodamine or 2,4-dichlorophenoxyacetic acid (2,4-D) were electropolymerized onto graphite electrodes using an aqueous solution equimolar in resorsinol/ortho-phenylenediamine and in the presence of the template molecule. For the dyes, the MIP-coated electrodes showed higher affinity for their template molecule than for a non-template dye. The 2,4-D-MIP-coated electrode showed a concentration dependent response for 2,4-D as compared to the polymer-coated electrode prepared in the absence of template molecule.     

合成引发方式对槲皮素-钴(Ⅱ)配位印迹聚合物结构与性能的影响

以槲皮素-钴(Ⅱ)的配合物为模板分子,在强极性甲醇溶剂中分别采用低温光引发和高温热引发聚合制备槲皮素-钴(Ⅱ)配位印迹聚合物.紫外-可见光谱分析确定了槲皮素与钴(Ⅱ)形成配合物的最佳配位比.根据印迹聚合物的平衡结合量优化功能单体丙烯酰胺用量.利用红外光谱、透射电镜和平衡结合实验,考察不同引发方式对聚合物的结构、微观形貌及结合性能的影响.进一步通过特异吸附容量和印迹指数确定,低温光引发聚合更适于配位分子印迹聚合物的制备.同时研究了不同阳、阴离子对印迹聚合物选择识别性的影响.结果表明光引发的金属配位分子印迹聚合物具有良好的吸附选择性,印迹指数可达3.919.     

Selective solid-phase extraction of bisphenol A using molecularly imprinted polymers and its application to biological and environmental samples

Molecularly imprinted polymers (MIPs) were prepared using bisphenol A (BPA) as a template by precipitation polymerization. The polymer that had the highest binding selectivity and ability was used as solid-phase extraction (SPE) sorbents for direct extraction of BPA from different biological and environmental samples (human serum, pig urine, tap water and shrimp). The extraction protocol was optimized and the optimum conditions were as follows: conditioning with 5 mL methanol–acetic acid (3:1), 5 mL methanol, 5 mL acetonitrile and 5 mL water, respectively, loading with 5 mL aqueous samples, washing with 1 mL acetonitrile, and eluting with 3 mL methanol. MIPs can selectively recognize, effectively trap and preconcentrate BPA over a concentration range of 2–20 μM. Recoveries ranged from 94.03 to 105.3 %, with a relative standard deviation lower than 7.9 %. Under the optimal condition, molecularly imprinted SPE recoveries of spiked human serum, pig urine, tap water and shrimp were 65.80, 82.32, 76.00 and 75.97 %, respectively, when aqueous samples were applied directly. Compared with C18 SPE, a better baseline, better high-performance liquid chromatography separation efficiency and higher recoveries were achieved after molecularly imprinted SPE.      

石杉碱甲分子印迹聚合物的制备、表征及其吸附性能

以硅胶为牺牲载体,石杉碱甲为模板分子,甲基丙烯酸为功能单体,二乙烯基苯为交联剂,偶氮二异丁腈为引发剂,首次制备了石杉碱甲分子印迹聚合物,并用红外光谱、扫描电子显微镜和热重分析研究了印迹聚合物的结构特征,用静态吸附法和Scatchard分析法研究了印迹聚合物的识别效能和表面位点分布特征。 结果表明,石杉碱甲印迹聚合物对模板分子具有较好的选择吸附性能,选择系数为1.399。Scatchard分析表明,印迹聚合物基体中主要存有两类吸附位点,对高亲和位点：平衡离解常数Kd1=0.776 g/L,最大表观结合量Qmax1=0.213 mg/g;对低亲和位点：平衡离解常数Kd2=0.169 g/L,最大表观结合量Qmax2=0.832 mg/g。 当该聚合物用于微固相萃取蛇足石杉粗提液中的石杉碱甲时,石杉碱甲回收率为93.5%,显示了较好的富集效果。     

印迹分子聚合物结合低共熔溶剂用于山楂中咖啡酸的固相萃取

在相同的实验条件下,分别合成了以咖啡酸为模板的印迹分子聚合物和无模板分子聚合物。使用场发射扫描电镜法和吸附实验表征这两种聚合物材料的孔状结构和选择性吸附性能。然后利用印迹分子聚合物、无模板分子聚合物、C₁₈萃取小柱这3种材料结合固相萃取法纯化山楂提取物中的咖啡酸,提取率分别为3.46、1.01、1.17 μg/g。为了优化固相萃取过程,实验研究了不同洗脱剂的影响。分别利用用氯化胆碱和甘油、氯化胆碱和尿素(摩尔比均为1:2)合成出两种低共熔溶剂。甲醇与这两种低共熔溶剂分别以不同的体积比混合作为洗脱剂,用于优化咖啡酸的固相萃取过程。实验结果表明,印迹分子聚合物是一种良好的固相萃取材料;当甲醇和甘油基低共熔溶剂在体积比为3:1混合时,表现出最好的洗脱能力,得到咖啡酸的回收率为82.32%。     

Synthesis and Evaluation of Molecularly Imprinted Polymers as Sorbents for Selective Extraction of Coumarins

Coumarin, 7-hydroxycoumarin and dicoumarol molecularly imprinted polymers (MIP) were synthesized by bulk polymerization. Methacrylic acid and 4-vinylpyridine were tested as functional monomers and methanol, ethanol, acetonitrile, toluene and chloroform were tested as porogens. The binding capabilities of the imprinted polymers were assessed by equilibrium binding analysis. Highest binding capacity was obtained for MIP prepared for the template 7-hydroxycoumarin synthesized in methacrylic acid as functional monomer, chloroform as porogen and methanol/water as analyte solvent. Scanning electron microscopy analysis documented its appropriate morphology. ATR-FTIR spectra confirmed successful polymerization of MIP. Coumarin structural analogues were employed to evaluate the polymer selectivity and it was found that polymer prepared for 7-hydroxycoumarin was selective for its template molecule. Kinetic studies showed relatively fast adsorption of analytes to MIPs (1 h). Rebinding properties of MIPs were evaluated by adsorption isotherms. The calculated data fitted well with experimental data showing that Freundlich isotherm is suitable for modelling the adsorption of tested coumarins on prepared MIPs. Applicability of polymer prepared for 7-hydroxycoumarin was tested for the selective extraction of coumarins from the sample of chicory.     

Quercetin molecularly imprinted polymers: Preparation, recognition characteristics and properties as sorbent for solid-phase extraction

Molecular imprinted polymers (MIPs) were prepared through thermal polymerization by using quercetin as the template molecule, acrylamide (AA) as the functional monomer and ethylene glycol dimethacrylate (EDMA) as the cross-linker in the porogen of tetrahydrofuran (THF). The synthesized MIPs were identified by both Fourier transform infrared (FTIR) and scanning electron microscope (SEM). Systematic investigations of the influences of key synthetic conditions, including functional monomers, porogens and cross-linkers, on the recognition properties of the MIPs were conducted. Scatchard analysis revealed that the homogeneous binding sites were formed in the polymers. Besides quercetin, two structurally similar compounds of rutin and catechol were employed for molecular recognition specificity tests of MIPs. It was observed that the MIPs exhibited the highest selective rebinding to quercetin. Accordingly, the MIPs were used as a solid-phase extraction (SPE) sorbent for the extraction and enrichment of quercetin in cacumen platycladi samples, followed by HPLC-UV analysis. The application of MIPs with high affinity and excellent stereo-selectivity toward quercetin in SPE might offer a novel method for the enrichment and determination of flavonoid compounds in the natural products.     

Application of umbelliferone molecularly imprinted polymer in analysis of plant samples

The molecularly imprinted polymers (MIPs) were synthesised and the influence of the type of porogen, the nature of sample solvent, and the binding capacity of material were tested by high-performance liquid chromatography (HPLC). Umbelliferone was used as the template for imprint formation. Methacrylic acid was used as the monomer and acetonitrile, ethanol, and chloroform as porogen. Non-imprinted polymers (NIPs) were prepared by the same procedure. The highest value of the specific binding capacity (269 μg of umbelliferone per 100 mg of polymer) was obtained for polymers prepared in chloroform as porogen and methanol/water (φ _r = 1: 1) as the sample solvent. The group-selective MIP was used as sorbent for the SPE pre-treatment of umbelliferone from plant extracts prior to HPLC analysis. Analysis of the spiked samples showed good recoveries (> 77 %). The limit of detection, limit of determination, and repeatability of the method were also calculated.     

Molecularly Imprinted Polymers Modified by Deep Eutectic Solvents and Ionic Liquids with Two Templates for the Simultaneous Solid-Phase Extraction of Fucoidan and Laminarin from Marine Kelp

Molecularly imprinted polymers modified by deep eutectic solvents and ionic liquids (ILs) were prepared as packing materials for the solid-phase extraction (SPE) of fucoidan and laminarin. The prepared materials were characterized by field emission scanning electron microscopy and Fourier transform infrared spectroscopy. The polymers modified by the deep eutectic solvent prepared by choline chloride and urea had the best extraction efficiencies for fucoidan and laminarin (95.5% and 87.6%, respectively) from marine kelp. The relative standard deviations for intraday and interday determination were less than 4.23%. The molecularly imprinted polymers modified by deep eutectic solvents and ILs showed outstanding applications for SPE and may offer novel sample pretreatment for other analytes.     

分子印迹聚合物的制备及孔结构研究

以N 叔丁氧羰酰 L 色氨酸和N 叔丁氧羰酰 L 酪氨酸为印迹分子 ,分别采用光引发聚合和热引发聚合制备了分子印迹聚合物 ,并对聚合物的手性识别能力进行了色谱评价 .结果表明 ,制备的分子印迹聚合物对印迹分子具有特异性的吸附作用 ,光引发聚合的N 叔丁氧羰酰 L 色氨酸的印迹聚合物对印迹分子的选择性因子达到 2 .318,热引发聚合的N 叔丁氧羰酰 L 酪氨酸对印迹分子的选择性因子为 1 373 进一步研究了分子印迹聚合物的孔结构 ,发现光引发聚合的分子印迹聚合物与空白聚合物的孔结构差别比热引发聚合的分子印迹聚合物与空白聚合物的差别更为明显 .对印迹分子洗脱前后的印迹聚合物的孔结构研究进一步表明 ,印迹分子存在于不同类型的孔中 .     

Molecularly imprinted polymer microspheres for solid-phase extraction of protocatechuic acid in Rhizoma homalomenae

Molecularly imprinted polymers (MIPs) had been prepared by precipitation polymerization method using acrylamide as the functional monomer, ethylene glycol dimethacrylate as the cross-linker, acetonitrile as the porogen solvent and protocatechuic acid (PA), one of phenolic acids, as the template molecule. The MIPs were characterized by scanning electron microscopy and Fourier transform infrared, and their performance relative to non-imprinted polymers was assessed by equilibrium binding experiments. Six structurally similar phenolic acids, including p-hydroxybenzoic acid, gallic acid, salicylic acid, syringic acid, vanillic acid, ferulic acid were selected to assess the selectivity and recognition capability of the MIPs. The MIPs were applied to extract PA from the traditional Chinese medicines as a solid-phase extraction sorbent. The resultant cartridge showed that the MIPs have a good extraction performance and were able to selectively extract almost 82% of PA from the extract of Rhizoma homalomenae. Thus, the proposed molecularly imprinted-solid phase extraction-high performance liquid chromatography method can be successfully used to extract and analyse PA in traditional Chinese medicines.     

Synthesis and evaluation of molecularly imprinted core-shell carbon nanotubes for the determination of triclosan in environmental water samples

Synthetic core-shell molecularly imprinted polymers (MIPs) were prepared for the extraction of trace triclosan in environmental water samples. The synthesis process combined a surface molecular imprinting technique with a sol-gel process based on carbon nanotubes (CNTs) coated with silica. The morphology and structure of the products were characterized by transmission electron microscopy and Fourier transform infrared spectroscopy. The adsorption properties of the polymers were demonstrated by equilibrium rebinding experiments and Scatchard analysis. The prepared imprinted materials exhibited fast kinetics, high capacity and favorable selectivity. The process of synthesis was quite simple and different batches of MIPs and non-imprinted polymers (NIPs) showed good reproducibility in the template binding. The feasibility of determination of triclosan from real samples was testified using spiked river and lake water samples. The recoveries of river water and lake water samples were ranged from 92.1 to 95.3% and 90.7 to 93.6%, respectively, when the environmental water samples were spiked with 0.1, 0.3, and 0.5 μg L(-1) of TCS. In addition, the reusability of MIPs and NIPs without any deterioration in capacity was demonstrated for at least 10 repeated cycles.     

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。