Separation of chiral compounds using magnetic molecularly imprinted polymer nanoparticles as stationary phase by microchip capillary electrochromatography

In this work, a simple and rapid approach was developed for separation and detection of chiral compounds based on a magnetic molecularly imprinted polymer modified poly(dimethylsiloxane) (PDMS) microchip coupled with electrochemical detection. Molecularly imprinted polymers were prepared employing Fe₃O₄ nanoparticles (NPs) as the supporting substrate and norepinephrine as the functional monomer in the presence of template molecule in a weak alkaline solution. After extracting the embedded template molecules, Fe₃O₄@polynorepinephrine NPs (MIP–Fe₃O₄@PNE NPs) showed specific molecular recognition selectivity and high affinity towards the template molecule, which were then used as stationary phase of microchip capillary electrochromatography for chiral compounds separation. Mandelic acid and histidine enantiomers were used as model compounds to test the chiral stationary phase. By using R‐mandelic acid as the template molecule, mandelic acid enantiomer was effectively separated and detected on the MIP‐Fe₃O₄@PNE NPs modified PDMS microchip. Moreover, the successful separation of histidine enantiomers on the MIP–Fe₃O₄@PNE NPs modified microchip using L‐histidine as template molecule was also achieved.     

分子印迹聚合物拆分消旋体酮洛芬

以(S) 酮洛芬为印迹分子利用分子印迹技术合成能识别(S) 酮洛芬的聚合物。聚合物作为高效液相色谱的固定相,消旋体酮洛芬在固定相能分开,同时聚合物还能将酮洛芬和布洛芬的混合物分开。     

Solid-phase microextraction of chlorpyrifos in fruit samples by synthesised monolithic molecularly imprinted polymer fibres

A monolithic solid-phase microextraction (SPME) fibre was fabricated based on a molecularly imprinted polymer that could be coupled with gas chromatography for extraction, and determination of chlorpyrifos. The time of extraction, pH, temperature and ionic strength were investigated as important factors on the extraction procedure. The fabricated fibre was firm, inexpensive, stable and selective which gave it vital importance in SPME. The selectivity of the fabricated fibre in relation to analogue compounds was also investigated. Under the optimum conditions, the calibration curve was linear in the range of 1–20 mg L^?1 (R² = 0.9899). The high extraction efficiency was obtained for chlorpyrifos with a detection limit of 0.23 mg L^?1. The fabricated fibre was successfully applied to SPME of chlorpyrifos from apple and grape fruits after its extraction and followed by gas chromatography-flame ionisation detector analysis.     

二苯甲酰-D-酒石酸分子印迹整体柱的制备及其色谱性能

采用紫外光谱法选择丙烯酰胺为功能单体,以二苯甲酰-D-酒石酸(D-DBTA)为模板分子,丙烯酰胺为功能单体,二甲基丙烯酸乙二醇酯为交联剂,甲苯和十二醇为混合致孔剂,用原位分子印迹技术,合成了D-DBTA分子印迹整体聚合物。在优化色谱条件的基础上,25min内基本实现了DBTA消旋体的手性分离,分离度达1.25。对色谱分离过程中的热力学进行分析,在所考察的温度范围内,色谱分离存在两种不同的热力学过程,且两者与范特霍夫方程能够很好地吻合。在这两种热力学过程的转换温度处,分离因子α达最大值。     

A molecularly imprinted polymer for solid phase extraction of allantoin

We describe a molecularly imprinted polymer (MIP) for the solid-phase extraction of the skin protectant allantoin. The MIP was deposited on the surface of monodisperse silica microspheres possessing acroyl groups on the surface (MH-SiO₂). The resulting MIP microspheres (MH-SiO₂@MIP) showed a 3.4-fold higher adsorption capacity and a 1.9-fold better selectivity for allantoin than the respective non-imprinted polymer (MH-SiO₂@NIP). The monolayer adsorption capacities of the MH-SiO₂@MIP and the MH-SiO₂@NIP were calculated with the help of the Langmuir model and found to be 6.8 and 1.9 mg?g^?1, respectively. Adsorption kinetics fit a pseudo-second order rate mechanism, with an initial adsorption rate of 1.44 for the MH-SiO₂@MIP, and of 0.07 mg?g^?1?min^?1 for the MH-SiO₂@NIP. The material can be regenerated, and its adsorption capacity for allantoin remains stable for at least five regeneration cycles. It was successfully used as a sorbent for the selective solid-phase extraction of allantoin from Rhizoma dioscoreae.

A molecularly imprinted polymer for solid phase extraction of allantoin

We describe a molecularly imprinted polymer (MIP) for the solid-phase extraction of the skin protectant allantoin. The MIP was deposited on the surface of monodisperse silica microspheres possessing acroyl groups on the surface (MH-SiO₂). The resulting MIP microspheres (MH-SiO₂@MIP) showed a 3.4-fold higher adsorption capacity and a 1.9-fold better selectivity for allantoin than the respective non-imprinted polymer (MH-SiO₂@NIP). The monolayer adsorption capacities of the MH-SiO₂@MIP and the MH-SiO₂@NIP were calculated with the help of the Langmuir model and found to be 6.8 and 1.9 mg•g⁻¹, respectively. Adsorption kinetics fit a pseudo-second order rate mechanism, with an initial adsorption rate of 1.44 for the MH-SiO₂@MIP, and of 0.07 mg•g⁻¹•min⁻¹ for the MH-SiO₂@NIP. The material can be regenerated, and its adsorption capacity for allantoin remains stable for at least five regeneration cycles. It was successfully used as a sorbent for the selective solid-phase extraction of allantoin from Rhizoma dioscoreae.

A molecularly imprinted polymer for the selective separation of allantoin was developed. It was successfully used as a sorbent for the selective solid-phase extraction of allantoin from Rhizoma dioscoreae.

     

Catalytical oxidation of styrene by molecularly imprinted polymer with phenylacetic acid as template

This letter used the molecular imprinting technology to build up the microenvironment around co-monomer bemin to mimic the cytochrome P450 catalyzing the epoxidation of styrene. The results showed that the conversion rates of products were obviously enhanced by molecularly imprinted polymers, compared to free heroin solution, using three kinds of oxidants. The used axial ligand in polymers synthesis also improved the total conversion rates.     

橄榄醇分子印迹聚合物的制备及评价(英文)

以橄榄醇为模板分子,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,甲苯和十二醇为溶剂,通过本体聚合法制备了橄榄醇分子印迹聚合物。利用平衡结合实验、扫描电镜(SEM)及红外光谱(FTIR)对分子印迹聚合物(MIP)进行了表征,并用该聚合物进行了加标麦麸中橄榄醇的固相萃取(SPE)研究。平衡结合实验表明MIP对模板分子具有更好的识别性。Scatchard分析表明对橄榄醇分子的吸附存在2类不同结合位点,其中高亲和力结合位点和低亲和力结合位点的解离常数分别为0.021和1.002 mmol/L,相应的最大表观结合量分别为18.74和135.9 μmol/g。在优化的固相萃取条件下,MIP固相萃取柱对加标麦麸中橄榄醇的回收率达到97.8%~98.8%,相对标准偏差为2.8%~4.2%(n=5),线性范围为0.1~100 mg/L,检出限(S/N=3)为0.062 mg/L。与非印迹聚合物(NIP)柱及市售聚苯乙烯/二乙烯基苯(PLS)柱相比,MIP柱的选择性更强,回收率更高,纯化效果更好。     

Rapid preparation of molecularly imprinted polymer by frontal polymerization

Frontal polymerization was successfully applied, for the first time, to obtain molecularly imprinted polymers (MIPs). The method provides a solvent-free polymerization mode, and the reaction can be completed in 30 min. By this approach, MIPs were synthesized using a mixture of levofloxacin (template), methacrylic acid, and divinylbenzene. The effect of template concentration and the amount of comonomer on the imprinting effect of the resulting MIPs was investigated. The textural and morphological parameters of the MIP particles were also characterized by mercury intrusion porosimetry, nitrogen adsorption isotherms, and scanning electron microscopy, providing evidence concerning median pore diameter, pore volumes, and pore size distributions. The levofloxacin-imprinted polymer formed in frontal polymerization mode showed high selectivity, with an imprinting factor of 5.78. The results suggest that frontal polymerization provides an alternative means to prepare MIPs that are difficult to synthesize and may open up new perspectives in the field of MIPs.

槲皮素表面分子印迹聚合物的制备及其应用研究

以接枝双键的凹凸棒土(TM)为载体,槲皮素为模板分子,采用表面印迹技术制备对槲皮素具有特异吸附性能的分子印迹聚合物(MIP)。利用光谱法选择实验条件及对化合物表征。采用静态法研究聚合物对槲皮素的结合性能与识别性能。结果表明,该分子印迹材料对槲皮素具有特异的识别特性和优良的亲和性,提高了传统聚合物的结合率。以该印迹聚合物为固相萃取材料,结合高效液相色谱法,对白菜中的槲皮素进行分离富集,方法回收率为84.0%~90.6%,相对标准偏差低于5.6%。     

Preparation and utilization of a molecularly imprinted polymer for solid phase extraction of tramadol

In this paper, a highly selective molecularly imprinted polymer (MIP) for tramadol hydrochloride, a drug used to treat moderate to severe pain, was prepared and its use as solid-phase extraction (SPE) sorbent was demonstrated. The molecularly imprinted solid-phase extraction procedure followed by high performance liquid chromatography with ultraviolet detector (MISPE-HPLC) was developed for selective extraction and determination of tramadol in human plasma and urine. The optimal conditions for molecularly imprinted solid-phase extraction (MISPE) consisted of conditioning with 1 mL methanol and 1 mL of deionized water at neutral pH, loading of tramadol sample (50 μg L⁻¹) at pH 7.5, washing using 1 mL acetone and elution with 3 × 1 mL of 10% (v/v) acetic acid in methanol. The MIP selectivity was evaluated by checking several substances with similar molecular structures to that of tramadol. Results from the HPLC analyses showed that the calibration curve of tramadol (using MIP from human plasma and urine) is linear in the ranges of 6–100 and 3–120 μg L⁻¹ with good precisions (1.9% and 2.9% for 5.0 μg L⁻¹), respectively. The recoveries for plasma and urine samples were higher than 81%.      

丹酚酸A分子印迹聚合物制备及识别性能研究

以丹酚酸A为模板分子,丙烯酰胺(AM)、α-甲基丙烯酸(MAA)、2-乙烯基吡啶(2-VP)和4-乙烯基吡啶(4-VP)为功能单体,乙二醇二甲基丙烯酸酯(EGDMA)为交联剂,丙酮、乙酸乙酯、乙腈和甲醇为致孔剂,采用本体聚合法制备了一系列丹酚酸A分子印迹聚合物.通过静态平衡吸附实验和选择性实验考察了印迹聚合物的吸附性能...     

Preparation and evaluation of a monolithic molecularly imprinted polymer for the chiral separation of neurotransmitters and their analogues by capillary electrochromatography

A monolithic molecularly imprinted polymer (MIP) column was prepared as the stationary phase for the capillary electrochromatographic (CEC) separation of a group of structurally related compounds including dopamine (DA), (±)-epinephrine (EP), (-)-isoproterenol (ISO), (±)-norepinephrine (NE), (±)-octopamine (OCT), and (±)-synephrine (SYN). Here, (-)-NE was used as the template. Either methacrylic acid (MAA) or itaconic acid (IA) together with a mixture of ethylene glycol dimethacrylate (EDMA) and α,α'-azobis(isobutyronitrile) (AIBN) in N,N-dimethylformamide (DMF) was introduced into a pre-treated, silanised, fused-silica capillary by a thermal non-covalent polymerisation procedure. Optimised conditions for the polymerisation reaction were assessed by the separation efficiency of the template. Both the template/monomer/cross linker molar ratio and the compositions of the functional monomer, cross-linker, and porogen affected polymerisation. The optimum in situ polymerisation reaction was performed at 65 °C for 17 min. By varying CEC parameters like eluent composition and pH, we observed that the addition of SDS to the eluent clearly improved the CEC separations. With a mobile phase of citrate buffer (10 mM, pH 3)/SDS (40 mM)/acetonitrile (2/2/1, v/v/v) solution and an applied voltage of 10 kV, the six related structures of the template and their enantiomeric mixtures were satisfactorily separated at 30 °C.     

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%).     

Recognition of oxytocin by capillary electrochromatography with monolithic tetrapeptide-imprinted polymer used as the stationary phase

Using YPLG (Tyr-Pro-Leu-Gly), a tetrapeptide, as the template, an imprinted monolithic column was prepared and applied to the selective recognition of oxytocin based on the epitope approach and capillary electrochromatography (CEC). By optimizing the polymerization solution in terms of functional monomer, cross-linking reagent, porogen, and imprinted template via CEC evaluations of synthesized columns, an imprinted monolith with good recognition capacity (the imprinting factors for YPLG and oxytocin were 4.499 and 4.013, respectively) and high column efficiency (theoretical plates for YPLG and oxytocin were 22,995 plates/m and 16,952 plates/m, respectively) was achieved. In addition, the effects of various experimental parameters on the recognition of oxytocin, including the organic modifier content, the buffer concentration, and the pH value, were studied systematically. Furthermore, a mixture of oxytocin and other proteins was analyzed using this monolithic CEC column, and oxytocin was eluted much more slowly than other large biomolecules, which demonstrated the high selective recognition ability of such an imprinted monolith for oxytocin with PLG (Pro-Leu-Gly) as the epitope. Figure Separation of a mixture of oxytocin, BSA, bovine hemoglobin, ovalbumin, and lysozyme on the open column, the blank monolithic column, and the monolithic YPLG-imprinted column     

Porous molecularly imprinted polymer membranes and polymeric particles

Porous free-standing molecularly imprinted polymer membranes were synthesised by the method of in situ polymerisation using the principle of synthesis of interpenetrating polymer networks and tested in solid-phase extraction of triazine herbicides from aqueous solutions. Atrazine-specific MIP membranes were obtained by the UV-initiated co-polymerisation of methacrylic acid, tri(ethylene glycol) dimethacrylate, and oligourethane acrylate in the presence of a template (atrazine). Addition of oligourethane acrylate provided formation of the highly cross-linked MIP in a form of a free-standing 60 μm thick flexible membrane. High water fluxes through the MIP membranes were achieved due to addition of linear polymers (polyethylene glycol M_w 20,000 and polyurethane M_w 40,000) to the initial mixture of monomers before the polymerization. As a result, typical semi-interpenetrating polymer networks (semi-IPNs) have been formed, where the cross-linked polymer was represented by the atrazine-specific molecularly imprinted polymer, while the linear one was represented by polyethylene glycol/polyurethane. Extraction of the linear polymers from the fully formed semi-IPNs resulted in formation of large pores in the membrane structure. At the same time, extraction of the template molecules lead to formation of the sites in the polymeric network, which in shape and arrangement of functional groups are complementary to atrazine. Reference polymeric membranes were prepared from the same mixture of monomers but in the absence of the template. Recognition properties of the MIP membranes were estimated in solid-phase extraction by their ability to selective re-adsorbtion of atrazine from 10⁻⁸ to 10⁻⁴ M aqueous solutions. The imprinting effect was demonstrated for both types of the MIP membranes and the influence of the type of the linear compound on their recognition properties was estimated. The recognition properties of the MIP membranes were compared to those of the MIP particles of the same composition. Morphology of the MIP membranes was investigated using the SEM microscopy. High fluxes of the developed membranes together with high affinity and adsorption capability make them an attractive alternative to MIP particles in separation processes.     

Monodispersed molecularly imprinted polymer for creatinine by modified precipitation polymerization

A monodispersed molecularly imprinted polymer (MIP) for creatinine was prepared by modified precipitation polymerization. The retention and molecular-recognition properties of the prepared MIP were evaluated by the hydrophilic interaction chromatography mode using a mixture of ammonium acetate buffer and acetonitrile as a mobile phase in liquid chromatography. The MIP had a specific recognition ability for creatinine, while other structurally related compounds, such as hydantoin, 1-methylhydantoin, 2-pyrrolidone, N-hydroxysuccinimide and creatine, could not be recognized on the MIP. In addition to shape recognition, hydrophilic interactions could work for the recognition of creatinine on the MIP.     

A novel molecularly imprinted polymer thin film as biosensor for uric acid

A novel amine-imide type conducting polymer, denoted as poly(PD-BCD), was molecularly imprinted on an indium-tin oxide (ITO) glass, with uric acid (UA) as the template and without any functional monomer. Intending to improve the imprinting efficiency, the polymer content was varied from 0.3 to 0.9 wt% during the preparation of the molecularly imprinted polymer (MIP), thereby varying the thickness of the polymer film; the content of UA as the template was maintained to be the same for all the films. The sensitivities of the thus prepared MIP electrodes were calculated to be more than 3-fold, compared to those of the corresponding non-MIP (NMIP) electrodes, which were obtained through the same method, however, without adding UA during their preparation. A polymer content of 0.6 wt% rendered the best performing MIP electrode, as judged by the imprinting efficiency and sensitivity of the electrode for UA. A linear relationship between steady-state currents and UA concentrations from 0 to 1.125 mM was obtained for both types of the sensors. The sensitivities of the MIP and the NMIP electrodes made with 0.6 wt% of polymer were calculated to be 24.72 and 6.63 μA mM⁻¹ cm⁻², respectively. The limit of detection (LOD) for this MIP was found to be 0.3 μM at a signal to noise ratio (S/N) of 3. This MIP electrode was used as a biosensor for the detection of UA in the presence of ascorbic acid (AA) in a sample containing these species in the same concentrations as those in a human serum. The selectivity of MIP electrode is higher than that of NMIP electrode, and the values are 28.76 and 8.85, respectively. The results are substantiated by using cyclic voltammetry (CV), linear sweep voltammetry, amperometry, and scanning electron microscopy.     

Acetylsalicylic acid electrochemical sensor based on PATP-AuNPs modified molecularly imprinted polymer film

A novel electrochemical sensor based on molecularly imprinted polymer film has been developed for aspirin detection. The sensitive film was prepared by co-polymerization of p-aminothiophenol (p-ATP) and HAuCl(4) on the Au electrode surface. First, p-ATP was self-assembled on the Au electrode surface by the formation of Au-S bonds. Then, the acetylsalicylic acid (ASA) template was assembled onto the monolayer of p-ATP through the hydrogen-bonding interaction between amino group (p-ATP) and oxygen (ASA). Finally, a conductive hybrid membrane was fabricated at the surface of Au electrode by the co-polymerization in the mixing solution containing additional p-ATP, HAuCl(4) and ASA template. Meanwhile, the ASA was spontaneously imprinted into the poly-aminothiophenol gold nanoparticles (PATP-AuNPs) complex film. The amount of imprinted sites at the PATP-AuNPs film significantly increases due to the additional replenishment of ASA templates. With the significant increasing of imprinted sites and doped gold nanoparticles, the sensitivity of the molecular imprinted polymer (MIP) electrode gradually increased. The molecularly imprinted sensor was characterized by electrochemical impedance spectroscopy (EIS), differential pulse voltammetry (DPV), and cyclic voltammetry (CV). The linear relationships between current and logarithmic concentration were obtained in the range from 1 nmol L(-1) to 0.1 μmol L(-1) and 0.7 μmol L(-1) to 0.1 mmol L(-1). The detection limit of 0.3 nmol L(-1) was achieved. This molecularly imprinted sensor for the determination of ASA has high sensitivity, good selectivity and reproducibility, with the testing in some biological fluids also has good selectivity and recovery.