Enantiomeric Resolution on L-Carnitine Selective Polymers Prepared by Molecular Imprinting

L-carnitine selective polymers were prepared by molecular imprinting using methacrylic acid as the functional monomer. The acid function of the monomer is expected to form hydrogen bond and ionic interactions with the amine function of the target molecule L-carnitine. The imprinted polymers were used as stationary phases in high-performance liquid chromatography (HPLC). It was shown that L-carnitine imprinted polymer exhibited a higher affinity to its template molecule, while the non-imprinted polymer had no affinity to the compounds tested. Racemic carnitine hydrochloride was efficiently resolved on the L-carnitine imprinted polymer, and the separation factor is 1.9.

Molecular Imprinting Fibrous Membranes of Poly(acrylonitrile-co-acrylic acid) Prepared by Electrospinning

IntroductionOver the past few decades, molecular imprinting has been described as a technology for preparing ＂molecular doors＂ which can be matched to ＂template keys＂. It has been found to be a simple and effective approach to introduce specific recognition sites into synthetic polymers, namely, to create molecular imprinting polymers Remarkable features such as stability, ease of preparation and low cost, have made molecular imprinting polymers particularly attractive in chemical sensors, catalysis, drug delivery, and dedicated separations. Practical applications of molecular imprinting polymers require accessible sites, fast mass transfer, and quick binding. However, present techniques used to prepare molecular imprinting polymers most often result in materials exhibiting a high affinity and selectivity but a low capacity and poor site accessibility for the target molecules. It is also very difficult to remove the imprinted molecules located in these molecular imprinting polymers because the highly cross-linked structures do not allow the templates to move freely. To some extent, combining molecular imprinting technology with membrane separation and surface imprinting can overcome the shortcomings, such as mass transfer limitations and non-quantitative recovery of the template molecules seen for imprinted materials fabricated by conventional bulk methods. In that ease, it appears to us that molecular imprinting polymers with high surface area to volume ratios are particularly desirable for largescale applications. Eleetrospun nano and ultrafine fibrous membranes are the most suitable materials due to advantages such as： （1） large specific surfaces, providing relatively high imprinting sites per unit mass; （2） fine porous structures, resulting in the accessibility of imprinting sites and low diffusion resistance necessary for high efficiency; and （3） easy recoverability from practical operation or applicability for continuous usages. Therefore, in this work, we prepared a unique kind of imprinted material--molecularly imprinted fibrous membranes of poly （ acrylonitrile-co-acrylic acid） fabricated by means of an electrospinning process.

Molecular Imprinting of (R)-(+)-α-Methylbenzylamine for Chiral Stationary Phase

A new type of molecular imprinting stationary phase was prepared by using R- (+)-α -methylbenzy lamine as the print molecule. Experiments of high performance liquid chromatography show that the new stationary phase has high enantio-selectivity and discriminates (R, S) -(± )- α -methylbenzylamine successful ly with α value of 1. 67

Computer Simulation and Experimental Investigations of Phenobarbital Molecular Imprinting System

The interaction process between the phenobarbital（PHN） and acrylamide（AM） was studied using the M062X/6-31G（d,p） method. The PHN and AM were used as the template and functional monomer,respectively. The molecular electrostatic potential（MEP） was simulated for predicting the reactive sites. The atoms in molecules theory helped to reveal the imprinting mechanism and optimize the molar ratios for PHN and AM. The molecular imprinted polymers（MIPs） containing PHN were synthesized through the precipitation polymerization. The diameter range of the obtained MIPs was from 150 to 390 nm. According to the computational results,MIPs with the molar ratio of PHN and AM equal to 1：6 showed high selective adsorption for PHN. The apparent maximum adsorption quantity（Q_（max）） of MIPs toward PHN was 7.9 mg/g,and the Qmax of nonimprinted polymer microspheres（NIPs） was 3.2 mg/g. Herein,the studies can provide theoretical and experimental references for the controllable fabrication of MIPs.

Simulation and Preparation of Molecular Imprinting System with Atrazine as Template

In this work, atrazine functions as a template molecule, and trifluoromethacrylic acid （TFMAA）, methacrylic acid （MAA）, methyl methacrylate （MMA）, and acrylamide （AM） serve as functional monomers, respectively. By using density functional theory （DFT）, the computational approach was carried out to simulate the self-assembly system of template and functional monomer. The geometry optimization, action sites, binding energies, and molecular imprinting mechanism of complexes with different functional monomers in different proportions were predicted. The simulation results showed that atrazine and the functional monomers interacted through hydrogen bond. Among the 4 functional monomers, the imprinted complex formed by TFMAA and atrazine with a ratio of （1：6） has the lowest binding energy and the best imprinting effect. Then, the microspheres of molecularly imprinted polymer （MIPs） were prepared by precipitating polymerization using atrazine as the template molecule and TFMAA as the functional monomer. The microspheres were observed by scanning electron microscopy （SEM）. The results showed that atrazine MIP microspheres had average particle size of 400 nm, which was greater than the non-imprinted polymeric microspheres （NIPs）. Dynamic adsorption experiments of MIPs showed that the adsorption reaction reached balance after 200 min. Analysis of the Scatchard plot revealed that the binding sites of MIPs to atrazine were equal class under the studied concentration range. The dissociation constant （Kd） and apparent maximum adsorption quantity （Qmax） of MIPs were 3.6×10^-5 mol/L and 4.83μmol/g, respectively. The study of selective adsorption between atrazine and metribuzin showed that imprinted microspheres had high selectivity for the template molecule atrazine.

Simultaneous Chiral Separation Using a Combinatorial Molecular Imprinting Phase

Molecular imprinting chiral stationary phase against Cbz-L-Serine (Cbz-L-Ser) and Cbz-L-Alaine (Cbz-L-Ala) were prepared utilizing acrylamide + 2-vinylpyridine as combined basic functional monomers. Cross-selectivity was used to obtain simultaneous chiral separations of Cbz-DL-Ser and Cbz-DL-Ala by connecting two columns packed with Cbz-L-Ser and Cbz-L-Ala imprinted chiral stationary phase, respectively.

Solid-phase Extraction of β-Sitosterol from Oldenlandia diffusa Using Molecular Imprinting Polymer

The β-sitosterol imprinted polymer was prepared for selective extraction and analysis of β-sitosterol from Old-enlandia diffusa （0. diffusa） followed by HPLC with UV detection. The imprinted polymers show high affinity and selectivity to β-sitosterol. Using this molecularly imprinted polymer （MIP） cartridge as solid-phase extraction （SPE） material, the interferences could be quickly washed out and β-sitosterol was selectively retained and enriched. HPLC analysis method was used to evaluate the characteristics of this MIP material. At the condition of mobile phase composed of MeOH/H20/H3PO4 （99/1/0.1, V/V/V, pH=6.0） and the flow rate of 1.0 mL·min -1, a good linear relationship was demonstrated when the concentrations of β-sitosterol were in the range of 0.50--100.0 μg·mL-1. The recoveries ranged from 75.3% to 86.5% and the inter-day and intra-day relative standard deviations were less than 5%. This developed HPLC method was proved to be acceptable for extraction offl-sitosterol from O. diffusa.

Preparation of a PTE simulacrum based on surface molecular imprinting

Firstly,we synthesized N-methacryloyl-histidine monomer and N-methacryloyl-histidine-Cu^2＋ complex（MAH-Cu^2＋）.Then the molecular imprinting polymers（MIP） has been prepared by surface grafting on uniform polystyrene（PS） core using reversible addition-fragmentation transfer polymerization（RAFT） with MAH-Cu^2＋ as the functional monomer,methyl paraoxon as the template to simulate phosphodiesterase（PTE）.Finally,we have investigated the catalytic hydrolytic activities of MIP and non-imprinting polymers（NIP） to the template methyl paraoxon and the template analogue ethyl paraoxon respectively by UV spectrophotometry.The results showed that the catalytic hydrolytic activity of MIP to the template methyl paraoxon was highest and the value of k is 8.67×10^-5 mmol L^-1 min^-1,3.89-fold higher than MIP to the template analogue ethyl paraoxon,2.79-fold higher than NIP to the template methyl paraoxon.The KM,rm of MSP are also determined,and KM = 3.95×10^-4）mol/L,rm = 2.12μmol/ min.The MIP can be reused with only lose 7%of catalytic activity for four cycles.

Novel polymer system for molecular imprinting polymer against amino acid derivatives

Molecular imprinting polymers (MIPs) against N-Cbz-L-Tyr were prepared utilizing different polymer systems and evaluated in HPLC mode. It was found that MIP utilizing cocktail functional monomers, acrylamide + 2-vinylpyridine showed better molecular recognition and better separation ability for the template molecule than those utilizing other functional monomers. MIP utilizing trimethylolpropane trimethacrylate as cross-linker showed higher load capacity and separation factor than those utilizing ethylene glycol dimethacrylate as cross-linker. Increasing the concentration of competing solvent, acetic acid weakened me ionic interaction and hydrogen bonding between the analyte and the functional monomers, 2-vinylpyridine and acrylamide, when me template enantiomer was separated by HPLC. Therefore increasing of the concentration of acetic acid leads to decreasing of capacity factor, separation factor and resolution.

Selective removal of 2,4-dichlorophenoxyacetic acid from water by molecularly-imprinted amino-functionalized silica gel sorbent

A molecularly-imprinted amino-functionalized sorbent for selective removal of 2,4-dichlorophenoxyacetic acid （2,4-D） was prepared by a surface imprinting technique in combination with a sol-gel process. The 2,4-D-imprinted amino-functionalized silica sorbent was characterized by FT-IR, nitrogen adsorption and static adsorption experiments. The selectivity of the sorbent was investigated by a batch competitive binding experiment using an aqueous 2,4-D and 2,4-dichlorophenol （2,4-DCP） mixture or using an aqueous 2,4-D and 2,4- dichlorophenylacetic acid （DPAC） mixture. The largest selectivity coefficient for 2,4-D in the presence of 2,4-DCP was found to be over 18, the largest relative selectivity coefficient between 2,4-D and 2,4-DCP over 9. The static uptake capacity and selectivity coefficient of the 2,4-D-imprinted functionalized sorbent are higher than those of the non-imprinted sorbent. The imprinted functionalized silica gel sorbent offered a fast kinetics for the extraction/stripping of 2,4-D, 73% of binding capacity （200 mg/L 2,4-D onto 20 mg of imprinted sorbent） was obtained within 5 min and the adsorbed 2,4-D can be easily stripped by the mixture solution of ethanol and 6 mol/L HC1 （V：V =1：1）. In a test of five extraction/stripping cycles, the adsorption capacity of the sorbent was all above 93% of that of the fresh sorbent. Experimental result showed the potential of molecularly-imprinted amino-functionalized sorbent for selective removal of 2,4-D.

Preparation of Molecular Imprinted Copolymer Membrane for Uracil Recognition

Uracil molecular imprinted membrane was prepared by phase inversion technique with [P(AN-co-MAA)] copolymer. SEM photograph shows that the resultant membrane has a typical ultrafiltration structure with Water Volume Flux of 3.7?0-5m3/m2穝, and uracil substrate permeation experiment shows that the resultant membrane can bind uracil into its structure, and shows a binding equilibrium.

Monocrotophos Molecularly Imprinted Microspheres Prepared by Precipitation Polymerization in Acetonitrile

Molecularly imprinted microspheres (MIP) for monocrotophos have been prepared by precipitation polymerization in acetonitrile (ACN) 60℃,24 h,using methacrylic acid (MAA),ethylene glycol dimethacrylate (EGDMA) and 2, 2-azobisiobutyronitrile (AIBN) as functional monomer,cross-linker and initiator,respectively.The recognition mechanism was elucidated by UV-vis spectra and computer modeling.Equilibrium binding experiment was employed to investigate the rebinding properties,Scatchard analysis showed that specific binding sites formed in the imprinted microspheres,and there were two kinds of binding sites,one was high binding sites,the other was low binding sites.This microspheres can be useful affinity absorbent used for organophosphorus pesticides separation and purification in food and environmental analysis.

Separation and Enrichment of Melamine in Feed by a New Molecularly Imprinted Solid-phase Extraction Column

[ Objective] The research aimed to develop a new molecular imprinting solid-phase extraction column for the separation and enrichment of melamine in feed. [ Method] The molecular imprinting polymer of melamine was prepared by mass polymerization method. This polymer was used as filler to prepare molecular imprinting polymer solid-phase extraction（MIP-SPE） column of melamine. The solid-phase extraction conditions were optimized and melamine content in concentrated solution was determined by using HPLC. [ Result] Melamine eould be separated selectively from feed and enriehed by self-made MIP-SPE column. It could wipe off complex matrix from feed and the addition recovery rate was 95%. The contrast experiment between MIP-SPE column and NMIP-SPE （ non-imprinted polymer- solid phase extraction） column showed that the extraction efficiency of the former was obviously higher than the latter. [ Conclusion] The home-made MIP- SPE column could be used to separate and enrich melamine in feed efficiently, with a broad application prospect.

Development of a competitive format sorbent assay for the determination of parathion in water using molecular imprinted polymer as specific sorbent carrier

A rapid,simple,and reliable competitive molecular imprinted polymer sorbent assay（MIPSA） was developed and validated for measurement of parathion in water samples.This assay employed a molecular imprinted polymer（MIP） that was synthesized with non-covalent imprinting method as capture reagent and p-aminoparathion conjugate of horseradish peroxidase（para-HRP） as an enzyme label.The assay depended on a competitive binding reaction between the enzyme conjugate and analyte for the binding sites of the MIP.The optimized analysis conditions of 10 ng mL-1 para-HRP and 10 mg mL-1 polymer were found.The assay was acceptable to detect parathion in water samples under the optimized conditions,with a limit of detection of 50 ng mL-1.Mean analytical recoveries of added parathion in water samples ranged from 101.2%to 105%.The precision of the assay was satisfactory; relative standard deviation ranged from 4.3%to 6%.

Molecularly Imprinted Polymers with Bi-functional Monomers of Polymerizable Cyclodextrin Derivatives and 2-(Diethylamino)-ethyl Methacrylate for Recognition of Norfloxacin in Aqueous Media

A molecularly imprinted polymer was synthesized using 2-（diethylamino）ethylmethacry -late（DEM） and bismethacryloyl-β-cyclodextrin（BMA-β-CD） as bi-functional monomers and norfloxacin（NOF） as a template. The results of equilibrium binding experiments indicated that the polymer has affinity and specificity for NOF in aqueous media, and that its selective recognition ability for the template was higher than that of the imprinted polymers synthesized with a single functional monomer （BMA-β-CD or DEM）.

Preparation and Selectivity of Molecularly Imprinted Polymer Coating on the Micro Pore Membrane of Polytetrafluoroethylene

In order to obtain mechanically stable membrane for practical application, the imprinted polymer was synthesized in the pores of polyfluoromembrane, the binding and transport ability of the membrane were studied.

Molecularly Imprinted Polymer for Theophylline Retention and Molecular Recognition Properties in Capillary Electrochromatography

Molecular imprinting of theophylline in poly (methacrylic acid- ethylene dimethacrylate) as CEC stationary phases was synthesized by an in situ photo-initiated polymerization reaction. The effect of electrolyte pH on xanthine derivatives and the stability of MIP column performance were investigated. the relative standard deviation (D RS) of migration time of five consecutive runs on MIP column was in the range of 2.2%–3.1%. The reproducibility of migration time column to column of M(A) was in the range of 3.8%–4.9%. The highest column efficiency was more than 140 000 plates per meter. The MIP capillaries had showed better selective for theophylline, which comparing with the reference column. The urine sample was separated by spiked 5×10?4 mol·L?1 theophylline. Key words capillary electrochromatography - molecular imprinting polymers - theophylline CLC number O 657.8 Foundation item: Supported by the National Nature Science Foundation of China (20375028) and the Research Fund for the National High Technology Development “863” of China (2002AA2Z2004)Biography: Cai Ling-shuang (1968-), female, Associate professor, Ph. D, research direction: separation science.

Fabrication of Molecularly Imprinted Electrospun Nanofibers with Mono-amidoxime Functional Ligand for Efficient Decontamination of Toxic Organophosphates

There is an urgent imperative to discover practical and efficacious artificial catalysts for the expeditious decontamination of toxic organophosphates. Herein, we propose a novel molecularly imprinted approach utilizing electrospun fiber scaffolds. Specifically, an amidoxime-based functional polymer (PMAOX) has been synthesized, which contains amidoxime groups that can act as nucleophiles and ligands for the formation of catalytic active sites. This polymer was blended with polyacrylonitrile (PAN), a well-processable material, to prepare a nanofiber mat using electrospinning techniques. Then, the amidoxime side groups on fiber surface were further cross-linked after the molecular coordination of templates to complete the molecularly imprinting process. This approach can not only enhance the content of functional molecularly imprinted polymers without affecting structural stability, but also combines surface MI technology to fully expose and leverage the advantages of active sites. The as prepared molecularly imprinted electrospun nanofibers MIF-Zn-PMAOX/PAN-6/4 catalyzes the degradation of paraoxon with a half-life of 32 min, and MIF-Ag-PMAOX/PAN catalyzes the degradation of parathion with a half-life of 18 min. The maximum catalytic rate evidence rate enhancements nearly 3700-fold of the self-hydrolysis. Thus, the mono-amidoxime based molecularly imprinted fibers demonstrate the versatility and superiority as self-detoxifying for organophosphates.

Preparation and Electrochemical Characters of Parathion Molecule Imprinted Polymeric Sensors

A sensitive, fast and low-cost molecular imprinted polymeric sensor for quantitative determination of parathion was prepared with chitosan（CS） as function matrix and parathion（PT） as template molecule via constant potential electrochemical deposition. Sensitive response was obtained with a detection limit of 1.0× 10-7 mol/L and an excellent recognition for PT was achieved due to the good memory capacity of the sensor. The developed sensor exhibited good fabrication reproducibility and acceptable stability, which provided a new promising tool for pesticide analysis.