A (−)‐norephedrine‐based molecularly imprinted polymer for the solid‐phase extraction of psychoactive phenylpropylamino alkaloids from Khat (Catha edulis Vahl. Endl.) chewing leaves

A molecularly imprinted polymer (MIP) was prepared using (?)‐norephedrine as the template, methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the cross‐linker and chloroform as the porogen. The MIP was used as a selective sorbent in the molecularly imprinted solid‐phase extraction (MIP‐SPE) of the psychoactive phenylpropylamino alkaloids, norephedrine and its analogs, cathinone and cathine, from Khat (Catha edulis Vahl. Endl.) leaf extracts prior to HPLC‐DAD analysis. The MIP was able to selectively extract the alkaloids from the aqueous extracts of Khat. Loading, washing and elution of the alkaloids bound to the MIP were evaluated under different conditions. The clean baseline of the Khat extract obtained after MIP‐SPE confirmed that a selective and efficient sample clean‐up was achieved. Good recoveries (90.0–107%) and precision (RSDs 2.3–3.2%) were obtained in the validation of the MIP‐SPE‐HPLC procedure. The content of the three alkaloids in Khat samples determined after treatment with MIP‐SPE and a commercial Isolute C₁₈ (EC) SPE cartridge were in good agreement. These findings indicate that MIP‐SPE is a reliable method that can be used for sample pre‐treatment for the determination of Khat alkaloids in plant extracts or similar matrices and could be applicable in pharmaceutical, forensic and biomedical laboratories. Copyright © 2015 John Wiley & Sons, Ltd.     

Molecularly imprinted polymer for solid‐phase extraction of ephedrine and analogs from human plasma

A molecularly imprinted polymer (MIP) was synthesized and evaluated to selectively extract ephedrine from human plasma. The MIP synthesis was performed in chloroform with methacrylic acid as a functional monomer and the target alkaloid as a template molecule. The resulting MIP was applied to the selective extraction of ephedrine from a pure aqueous medium. A recovery about 74% was obtained using the MIP with only 7% on the nonimprinted polymer (NIP). A very straightforward selective SPE procedure was then successfully applied to the direct extraction of ephedrine from spiked human plasma with a high extraction recovery (68%) on the MIP with no recovery on the NIP. Moreover, the MIP was used for the selective extraction of catecholamine neurotransmitters, i.e. adrenaline and noradrenaline.     

Preparation and application of a molecularly imprinted polymer for the determination of trace metolcarb in food matrices by high performance liquid chromatography

In this article, for the first time, a molecularly imprinted polymer (MIP) for the metolcarb was prepared by bulk polymerization using metolcarb as the template, methacrylic acid as the functional monomer and ethylene glycol dimethacrylate as the cross‐linker. The prepared polymer was characterized by FT‐IR, static and kinetic adsorption experiments, and the results showed that it has been successfully synthesized and had good selective ability for metolcarb. The MIP was applied as a sorbent in molecularly imprinted SPE coupled with HPLC‐UV for separation and determination of trace metolcarb in three kinds of food matrices at three concentration levels. Under the optimal conditions, the LODs (S/N=3) of cabbage, cucumber and pear were 7.622, 6.455 and 13.52 μg/kg, respectively, and recoveries were in the range of 68.80–101.31% with RSD (n=3) below 3.78% in all cases. To demonstrate further the selectivity of the MIP obtained, a comparison with commercially available C₁₈ SPE was performed. The results indicated that molecularly imprinted SPE showed better chromatography, better selectivity and higher recoveries for metolcarb than commercially available C₁₈ SPE.     

Isolation of sinapic acid from broccoli using molecularly imprinted polymers

A molecularly imprinted polymer was synthesized for the purpose of sinapic acid isolation from Egyptian nutraceutical Botrytis italica, L. (broccoli) due to its prominent medicinal and wide pharmacological activities. A computational study was first developed to determine the optimal template to functional monomer molar ratio. Based on the computational results, five polymers were synthesized using a bulk polymerization method with sinapic acid as the template molecule. Evaluation of the synthesized polymers binding performance was carried out using batch rebinding assay, which revealed that the molecularly imprinted polymer of molar ratio (1:4:20), template to functional monomer (4‐vinyl pyridine) to crosslinker (ethylene glycol dimethacrylate) was of optimum performance, thus, this polymer was applied for sinapic acid isolation from closely related analogues. This represents a more practical approach to isolate sinapic acid from different natural extracts selectively.     

Synthesis of a molecularly imprinted polymer for the selective solid-phase extraction of chloramphenicol from honey

Solid-phase extraction (SPE) with a molecularly imprinted polymer (MIP) as sorbent has been investigated for the clean-up of the broad-spectrum bacteriostatic antibiotic chloramphenicol (CAP) in honey samples. The MIP was prepared by using methacrylic acid (MAA) as functional monomer, ethylene glycol dimethacrylate (EDMA) as cross-linker, chloroform as porogen and CAP as template molecule. The binding behaviour of the template CAP on the MIP was evaluated by high-performance liquid chromatography, and then the MIP was applied as a sorbent in SPE to selectively extract CAP from honey. It was shown that recoveries of nearly 100% of a CAP standard solution and up to 94% from spiked honey samples could be obtained after SPE.     

Molecularly Imprinted Polymer Monolithic Column Separation of Isomers and Analogues of Vanillin by Capillary Electrochromatography

A vanillin imprinted capillary monolithic column was synthesized by in situ polymerization reaction using ethylene-glycol dimethacrylate as cross-linking monomer and methacrylic acid as functional monomer. Under the optimum conditions of capillary electrochromatography, this molecularly imprinted polymer （MIP）-based column showed high selectivity and could recognize not only template molecule vanillin but also positional isomer o-vanillin from their structural analogues.     

Selective extraction of clonazepam from human plasma and urine samples by molecularly imprinted polymeric beads

A molecularly imprinted polymer (MIP) based on free‐radical polymerization was prepared with 1‐(N,N‐biscarboxymethyl)amino‐3‐allylglycerol and N,N‐dimethylacrylamide as functional monomers, N,N‐methylene diacrylamide as the cross‐linker, copper ion‐clonazepam as the template and 2,2‐azobis(2‐methylbutyronitrile) as the initiator. The imprinted polymer was characterized by Fourier transform infrared spectroscopy, elemental analysis, thermogravimetric analysis, and SEM. The MIP of agglomerated microparticles with multipores was used for SPE. The imprinted polymer sorbent was selective for clonazepam. The optimum pH and sorption capacity were 5 and 0.18 mg/g at 20°C, respectively. The profile of the drug uptake by the sorbent reflects good accessibility of the active sites in the imprinted polymer sorbent. The MIP‐SPE was the most feasible technique for the extraction of clonazepam with a high recovery from human plasma and urine samples.     

Synthesis of molecularly imprinted polymers for the application of selective clean-up vinblastine from Catharanthus roseus extract

Molecularly imprinted polymers (MIPs) are synthetic tailor-made polymers with high selectivity towards a particular substance (template). An MIP using vinblastine (VLB) as the template molecule was synthesized and characterized. The presence of monomer-template complexes in a non-covalent way was confirmed by UV-vis spectrometry analysis. The polymerization was performed using methacrylic acid (MAA) as the functional monomer, ethylene glycol dimethacrylate (EGDMA) as the cross-linking agent, and toluene as the porogenic solvent by a thermo-polymerization method. The characterization of the obtained MIP was evaluated by scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) analysis. It was observed that the morphology of the MIP was more porous and rough, and the surface area had a significant increase compared with that of the non-imprinted polymer (NIP). This MIP was used as the sorbents of solid-phase extraction (SPE) to assess the selectivity of the MIP after optimization of the SPE protocol. VLB was specifically adsorbed on the MIP cartridge, while to vincristine (VCR), the chemical analog of VLB, almost no selective binding appeared. On the basis of the results, Catharanthus roseus extract was applied to the MIP cartridge for investigating its capability to extract VLB from the plant extract, and the capacity of the MIP cartridge was also evaluated. It was shown that the MIP could effectively enrich VLB from C. roseus extract and the recovery amounted to 93.8%. The solvents dissolving the samples had significant influence on the capacity of the MIP cartridge; it was 750 μg/g in toluene, 625 μg/g in chloroform, and 250 μg/g in methanol.     

Preparation and Characterization of Trans‐Resveratrol Imprinted Polymers

Abstract

In order to selectively extract trans‐resveratrol from Chinese herbs, molecularly imprinted polymers (MIPs) were prepared with trans‐resveratrol as the template molecule. The influences of porogenic solvents and functional monomers on the recognition properties of the polymer were studied. The MIP, which was prepared in acetone using 4‐vinylpyridine as functional monomer, displayed good affinity and recognition property for the template molecule. This indicates that the 4‐vinylpyridine can form hydrogen‐bonding or ionic interaction with trans‐resveratrol. Experimental result also indicated that the MIP column can separate trans‐resveratrol from matrix components in the Polygonum cuspidatum extract.     

Synthesis of molecularly imprinted polypyrrole as an adsorbent for solid‐phase extraction of warfarin from human plasma and urine

The aim of this work was to develop a method for the clean‐up and preconcentration of warfarin from biological sample employing a new molecularly imprinted polymer (MIP) as a selective adsorbent for solid‐phase extraction (SPE). This MIP was synthesized using warfarin as a template, pyrrole as a functional monomer and vinyl triethoxysilane as a cross‐linker. The molar ratio of 1:4:20 (template–functional monomer–cross‐linker) showed the best results. Nonimprinted polymers (NIPs) were prepared and treated with the same method, but in the absence of warfarin. The prepared polymer was characterized by Fourier transmission infrared spectrometry and scanning electron microscopy. An adsorption process (SPE) for the removal of warfarin using the fabricated MIPs and NIPs was evaluated under various conditions. Effective parameters on warfarin extraction, for example, type and volume of elution solvent, pH of sample solution, breakthrough volume and maximum loading capacity, were studied. The limits of detection were in the range of 0.0035–0.0050 µg mL^?1. Linearity of the method was determined in the range of 0.0165–10.0000 µg mL^?1 for plasma and 0.0115–10.0000 µg mL^?1 for urine with coefficients of determination (R²) ranging from 0.9975 to 0.9985. The recoveries for plasma and urine samples were >95%. Copyright © 2015 John Wiley & Sons, Ltd.     

Optimization of the process parameters of synthesis of vinblastine imprinted polymer

Molecularly imprinted polymers (MIPs) are tailor-made polymers with high selectivity for the template molecule. This selectivity arises from the synthetic procedure followed to prepare the MIP. In this work, the influence of process parameters on the preparation of vinblastine (VLB) imprinted polymers was presented. In the procedure of polymerization, VLB (0.1 mmol) was used as the template molecule and a commonly used initiator, azobisisobutyronitrile (AIBN), was employed to initiate the reaction at 60 °C. The influence of the following parameters was investigated: the moles of functional monomer (MAA, 0.3-1.0 mmol), the moles of cross-linker (EDMA, 1.5-5.0 mmol) and the porogenic solvent (toluene or acetonitrile). A mathematical method of uniform design was applied to optimize these selected parameters in order to increase the selectivity of MIP for template molecule. The experimental data were analyzed to obtain the regression model and the optimal conditions were achieved by optimization with uniform design software. The MIP was synthesized under the optimal conditions that 1.0 mmol of MAA and 5.0 mmol of EDMA copolymerized in toluene in the presence of 0.1 mmol of VLB. After removal of the template molecule, the obtained MIP was then employed as the sorbents of solid-phase extraction (SPE) to separate VLB from Catharanthus roseus extract. The results showed that the polymer exhibited high affinity to the template molecule and could separate and enrich VLB from C. roseus extract effectively. The recovery of VLB on the optimal MIP was 89.00%, which agreed closely with the predicted recovery. Therefore it is possible to further improve the nature of the polymer by optimizing the polymerization parameters with the method of uniform design.     

Molecularly imprinted solid-phase extraction of naphthalene sulfonates from water

A new polymeric sorbent synthesised by exploiting molecular imprinting technology has been used to selectively extract naphthalene sulfonates (NSs) directly from aqueous samples. In the non-covalent molecular imprinting approach used to prepare this polymer, 1-naphthalene sulfonic acid (1-NS) and 4-vinylpyridine (4-VP) were used as a template molecule and functional monomer, respectively, and both dissolved in a mixture of methanol/water (4:1) as porogen together with the cross-linker ethylene glycol dimethacrylate. The new non-covalent molecularly imprinted polymer (MIP) prepared in aqueous environment was used as a sorbent in solid-phase extraction (SPE) to selectively extract a group of naphthalene mono- and disulfonates. When one litre of a standard aqueous solution, which contained a mixture of eight NSs, was percolated through the SPE cartridge, all the NSs were retained on the MIP because of the cross-reactivity of the polymer. Recoveries were higher than 80% for all the compounds even after a clean-up step with methanol (MeOH). The MIP was also used to analyse water from the Ebro river.     

BSA‐imprinted synthetic receptor for reversible template recognition

A novel approach to the manufacturing of protein‐responsive imprints on a home‐made chitosan substrate was established together with m‐aminophenylboronic acid (APBA) as a functional monomer. The produced polymers were characterized using both (1) equilibrium adsorption assays and (2) high performance liquid chromatography analysis. Results confirmed that the synthesized BSA‐MIP (molecularly imprinted polymer) has a high affinity towards its template compared to the determined control proteins. The produced BSA‐MIP featured largely in its good adsorption reversibility, especially in competitive binding assays, which is of great biological significance in separations. Non‐specific binding was reduced to almost zero in a BSA/BHb competitive binding event. An excellent HPLC profile of template recognition was found for BSA‐MIP, even under harsh mobile phase conditions. In the present work, the adopted trapped‐template‐release method permits recovery of bound BSA [1]. The strategy of making an artificial protein‐receptor with high adsorption affinity and reversibility is promising in on‐line isolation of target protein from complicated biological environments.     

Rapid Preparation of Monolithic Molecular Imprinted Polymer Fiber for Solid Phase Microextraction by Microwave Irradiation

In this paper, a simple, fast and in situ polymerization strategy to prepare monolithic molecularly imprinted polymer (MIP) fibers for solid phase microextraction (SPME) is developed using silica capillaries as molds. With the help of microwave irradiation, polymerization was carried out in 5.5 min using olivetol as a template molecular, α‐methacrylic acid (MAA) as a functional monomer and ethylene dimethacrylate (EDMA) as a crosslinker, toluene and dodecanol as the binary porgens. The resulted MIP fibers were finally obtained after silica being etched away with a controlled length, and subsequently characterized by scanning electron microscope (SEM) and Fourier transform infrared absorption spectroscopy (FT‐IR). Under the optimal extraction conditions, a simple method based on the coupling of MIP SPME with high performance liquid chromatography (HPLC) was used for the selective determination of the model mixtures of olivetol, phenol and m‐toluidine in lake water and wheat bran samples. The recoveries of olivetol, phenol and m‐toluidine for both samples were in the range of 87.3‐93.6%, 21.4‐27.2%, 18.9‐24.8% at three spiked levels, respectively, demonstrating that higher extraction and the specific absorption occurred between the template molecule and the prepared MIP fiber.     

Selective solid-phase extraction of a triterpene acid from a plant extract by molecularly imprinted polymer

A molecularly imprinted polymer (MIP) has been prepared by a thermal polymerisation method using methacrylic acid as functional monomer, ethylene glycol dimethacrylate as cross-linking agent, chloroform as porogenic solvent and an oleanane triterpene compound (18-beta-glycyrrhetinic acid) as imprinted molecule (template). Equilibrium ligand binding experiments were done to assess the performance of the MIP relative to non-imprinted polymer (NIP). After optimisation of SPE protocol (CHCl3 as washing solvent and MeOH as elution solvent), successful imprinting was confirmed by comparison of the recoveries between NIP (5%) and MIP (97%) cartridges. The binding capacity of the MIP for 18-beta-glycyrrhetinic acid was determined to be 0.94 mg g(-1). Four structurally related oleanane triterpenes (18-alpha-glycyrrhetinic acid, oleanolic acid, echinocystic acid, erythrodiol) were selected to assess the MIP selectivity. Experimental data illustrated the influence of functional groups on the triterpene skeleton. The MIP was applied to the solid-phase extraction of triterpenoids from a plant extract prior HPLC analysis. However, CHCl3 was replaced by ACN during the washing step in order to suppress non-specific interactions due to polar matrix components. A selective extraction of 18-beta-glycyrrhetinic acid from hydrolyzed extract of liquorice roots was achieved with a good extraction yield (98%).     

Selective extraction of derivates of p-hydroxy-benzoic acid from plant material by using a molecularly imprinted polymer

Selective SPE of derivates of p-hydroxybenzoic acid (pHBA) from plant extract of Melissa officinalis is presented using a molecularly imprinted polymer (MIP) made with protocatechuic acid (PA) as template molecule. MIP was prepared with acrylamide as functional monomer, ethylene glycol dimethacrylate as crosslinking monomer and ACN as porogen. MIP was evaluated towards six phenolic acids: PA, gallic acid, pHBA, vanillic acid (VA), gentisic acid (GeA) and syringic acid (SyrA), and then steps of molecularly imprinted SPE (MISPE) procedure were optimized. The best specific binding capacity of MIP was obtained for PA in ACN (34.7 microg/g of MIP). Other tested acids were also bound on MIP if they were dissolved in this solvent. ACN was chosen as solvent for sample application. M. officinalis was extracted into methanol/water (4:1, v/v), the extract was then evaporated to dryness and dissolved in ACN before application on MIP. Water and ACN were used as washing solvents and elution of benzoic acids was performed by means of a mixture methanol/acetic acid (9:1, v/v). pHBA, GA, PA and VA were extracted with recoveries of 56.3-82.1% using this MISPE method. GeA was not determined in plant extract.     

Metal ion mediated molecularly imprinted polymer for selective capturing antibiotics containing beta-diketone structure

A new molecularly imprinted polymer (MIP) targeting to quinolones (Qs) and tetracyclines (TCs) was synthesized using itaconic acid (ITA) and ciprofloxacin (CIP) as a functional monomer and template molecule, respectively. Factors affecting the overall performance of MIP were investigated, and the results showed that Fe(3+) ion play a vital role in the formation of MIP with high molecular imprinting effect. Meanwhile, the chelating ability of monomer, species of template molecule, as well as the molar ratio of monomer and template also contribute to the performance of the obtained MIP. Cyclic voltammetry verified that, with the participation of Fe(3+) ions, a ternary complex of ITA-Fe(3+)-CIP could be formed before polymerization. Compared with conventional MIP prepared from commonly used monomer, methacrylic acid (MAA), the new MIP show significantly enhanced molecular imprinting effect and higher capacity for specific adsorption of target compounds as revealed by static and dynamic binding experiments. The MIP was successfully used as solid-phase extraction (SPE) adsorbent for enriching a broad spectrum of antibiotics containing beta-diketone structure from surface water sample. HPLC detection showed that high recovery rate (78.6-113.6%) was found in these spiked antibiotics, whereas recovery rate for the non structurally related drugs, epinephrine (EP) and dopamine (DOPA), was very low (4.7-7.6%) on the MIP cartridges. The results demonstrate that the MIP prepared by the strategy proposed in this work, could specifically target to a series of structurally related antibiotics containing beta-diketone structure.     

分子印迹聚合物选择性富集长春碱的研究

分子印迹聚合物(MIPs)是近年来发展起来的一种对特定分子(模板分子)具有高度选择性的合成高分子材料.本文以长春碱(VLB)为模板分子,以甲基丙烯酸(MAA)为功能单体、乙二醇二甲基丙烯酸酯(EGDMA)为交联剂,在偶氮二异丁腈(AIBN)的引发下制备了长春碱印迹聚合物(VLB-MIP).采用紫外光谱对VLB与MAA之间形成的模板-功能单体复合物进行了分析,通过扫描电镜(SEM)对制备的VLB-MIP的表面形态进行了表征,并用BET法对MIP表面的孔径进行了测定.结果表明,VLB-MIP与未加模板分子制备的非印迹聚合物(NIP)相比表面多孔、粗糙,比表面积显著增加.以VLB-MIP作为固相萃取(SPE)的吸附剂,对VLB-MIP的选择性进行了评价,VLB-MIP能特异性地吸附VLB,而对VLB的结构类似物长春新碱(VCR)却没有表现出明显的吸附行为.将长春花提取物上样于填充VLB-MIP的SPE柱上,在最优实验条件下,长春花提取物中的VLB能被高效富集.此外,上样溶剂对MIP柱的吸附容量有影响,长春花提取物溶于非极性溶剂甲苯时,MIP的吸附容量最大为750μg/g,其次是氯仿吸附容量为625μg/g,最小的是甲醇为250μg/g.     

1-氨基乙内酰脲分子印迹聚合物的制备和吸附性能研究

以1-氨基乙内酰脲(AHD)为模板分子,α-甲基丙烯酸(MAA)为功能单体,乙二醇二甲基丙烯酸酯(EDMA)为交联剂,采用本体聚合方法合成了分子印迹聚合物(M IP),考察了模板分子与功能单体不同比例下制备的M IP对模板分子的吸附性能。通过Scatchard分析,表明该印迹聚合物上存在一类等价的吸附位点,其结合位点的离解常数KD=4.33mmol/L。     

邻苯二甲酸二（2-丙基庚）酯分子印迹固相萃取剂的制备及其应用

以邻苯二甲酸二辛酯（DOP）为虚拟模板分子,α-甲基丙烯酸（MAA）为功能单体,乙二醇二甲基丙烯酸酯（EDMA）为交联剂,采用沉淀聚合法制备了对邻苯二甲酸二（2-丙基庚）酯（DPHP）具有高选择性的分子印迹聚合物（MIP）。用紫外分光光度法探索了不同功能单体与模板分子的结合能力,与功能单体丙烯酸（AA）相比,MAA与DOP的结合能力更强,其最佳结合的物质的量比为6：1。考察MIP对DOP、DPHP、邻苯二甲酸二甲酯（DMP）、邻苯二甲酸二丁酯（DBP）的选择吸附性能,发现该聚合物对DPHP具有更高的选择吸附性。以制备的聚合物为固相萃取填料,结合HPLC分析,考察了淋洗剂与洗脱剂的种类和用量对DPHP回收率的影响。将DPHP甲醇溶液加载至萃取柱后用1 mL甲醇-水（1：9,v/v）淋洗,5 mL甲醇-乙酸（9：1,v/v）洗脱,DPHP在分子印迹固相萃取（MISPE）柱上的回收率达到96.8%,而在非印迹固相萃取（NISPE）柱上的回收率仅为52.9%。将建立的MISPE-HPLC方法应用于测定兔口服DPHP后不同时间点兔血清中DPHP的浓度,发现其血药浓度的最大值为5.88 μg/mL,达峰值时间为4 h,DPHP加标回收率为90.0%~92.0%,相对标准偏差小于5%。