Composition Of Polymerization Mixture Research Articles

Imprinted polymers in analytical chemistry

Molecularly imprinted polymers were prepared and tested in different way. 1-methyl-2-piperidinoethylester of 4-decyloxyphenylcarbamic acid was used as template for imprints formation. Acrylamide, 4-vinylpyridine and methacrylic acid as monomers and methanol and acetonitrile as a porogene were used. Non-imprinted polymers (NIP) were prepared for each imprinted polymer by the same procedure. Polymers were employed as sorbents for solid-phase extraction (SPE). In this work the influence of polymerization mixture composition on polymer properties, such as capacity and selectivity, was investigated. The influence of alkoxy-chain length and position on benzene ring on the selectivity of polymers was also investigated.

Epitope‐Imprinted Nanoparticles as Transforming Growth Factor‐β3 Sequestering Ligands to Modulate Stem Cell Fate

AbstractGrowth factors (GFs) are biomolecules with potent biological effects but inherent limitations hinder their potential as therapeutic agents and cell culture supplements in tissue engineering and regenerative medicine (TERM). Biomaterials that sequester endogenous GFs by affinity binding might circumvent such limitations and thus are being increasingly investigated. Here, molecularly imprinted nanoparticles (MINPs) are proposed as specific abiotic ligands for GFs. As a proof of concept, a conformational epitope of transforming growth factor‐β3 (TGF‐β3) is designed and surface imprinted onto polyacrylamide‐based nanoparticles by inverse microemulsion polymerization. It is found that, depending on the polymerization mixture composition, MINPs can recognize and preferentially bind TGF‐β3, either in noncompetitive assays or from a complex human fluid (platelet lysate). Substrates functionalized with MINPs are then used for 2D culture of adipose‐derived stem cells. Remarkably, gene and protein expression profiles show a marked upregulation of SOX‐9, suggesting activation of TGF‐β3 signaling pathways without requiring supplementation with exogenous GF. Likewise, culturing these cells in pellets incorporating MINPs previously incubated with platelet lysate results in higher collagen II‐rich matrix deposition, compared to pellets incorporating non‐imprinted nanoparticles. In summary, results suggest MINPs can be used as cost‐effective, stable, and scalable alternative abiotic GF ligands to guide cell fate in TERM applications.

Molecularly imprinted polymer as stationary phase for HPLC separation of phenylalanine enantiomers

l-Phenylalanine molecularly imprinted polymers were synthesized by bulk polymerization. Methacrylic acid and acrylamide were tested as functional monomers. Ethanol and acetonitrile were used as porogenic solvents. Optimal composition of polymerization mixture was methacrylic acid, template, and ethylene glycol dimethacrylate in molar ratio 1:5:26. MIP was applied as HPLC chiral stationary phase. The influences of the mobile phase composition, flow rate, column temperature, and column length on the efficiency of enantioseparation were investigated. The enantioselective separation of phenylalanine was attained in reversed phase mode at 45 °C with acetonitrile/water containing 1.5% acetic acid (90/10, v/v) as mobile phase (resolution value was 1.49, selectivity factor was 1.38). Applicability of polymeric stationary phase prepared for l-phenylalanine was tested for analysis of dietary supplement sample. The UV detection limits for both enantiomers were 1 mg cm−3 (S/N = 3). Good linearity was observed from 1 to 10 mg cm−3.

Nanostructured hybrid monolith with integrated stirring for the extraction of UV-filters from water and urine samples

This article presents a monolithic extraction unit with integrated stirring using carbon nanohorns and methacrylate-based compounds as monomers. The hybrid monolithic material was prepared by thermal polymerization at 70 °C for 24 h, and was applied for the extraction of UV-filters from waters and human urine samples. To achieve the integrated stirring unit, the monolith was grown over an ironware. Variables dealing with the polymerization mixture composition and the microextraction procedure were studied in depth. The resulting hybrid monolithic polymer was also characterized by scanning electron microscopy (SEM) and nitrogen intrusion porosimetry. The target analytes were quantified by UPLC-DAD, and the limits of detection were between 1 and 10 μg/L. The precision of the method (inter extraction units) expressed as relative standard deviation ranged from 5.4% and 7.9%. Also, relative recoveries values of the analyte spiked to swimming pool water and urine samples varied in the interval 72–124 and 71–114%, respectively.

Controlled crosslinking of trimethylolpropane trimethacrylate for preparation of organic monolithic columns for capillary liquid chromatography.

Organic monolithic columns based on single crosslinking of trimethylolpropane trimethacrylate (TRIM) monomer were prepared in a single step by living/controlled free-radical polymerization. Full optimization of the preparation, such as using different percentages of TRIM and different amounts of radical promoter as well as various porogen solvents were explored. The resulting monolithic columns were characterized by scanning electronic microscopy and nitrogen sorption for structure morphology studies and surface area measurements, respectively. Using capillary liquid chromatography, 150μm i.d. columns were applied to separate a mixture of small hydrophobic molecules. The results indicated that column performance is highly sensitive to the type and the amount of porogen solvents used in the polymerization mixture composition. Good resolution factors and methylene selectivity were obtained, indicating the promising potential of this material for capillary liquid chromatography separations.

Repeatability of Octadecyl Methacrylate-Based Monolithic Columns for Capillary Electrochromatography

Octadecyl methacrylate-based monolithic capillary columns were prepared using octadecyl methacrylate as the monomer, ethylene dimethacrylate as the cross-linking agent, 2-acryloylamido-2-methylpropanesulfonic acid as the ionizable monomer, responsible for a negatively charged stationary phase surface and able to support a cathodic electrosmotic flow, and amyl alcohol and 1,4-butanediol as porogenic solvents. The repeatability of the morphological aspect of the monolithic material was evaluated by scanning electron microscopy (SEM). The uniformity along the same monolithic bed was also investigated by SEM. Replicate determinations of surface area and pore volume were also performed and compared. The repeatability of the obtained electrochromatographic efficiencies for separations of alkylbenzenes using the stationary phases prepared was also evaluated. A column that had a plate height of 31 μm was tested for separation of polycyclic aromatic hydrocarbons. Even though minimal possible variation of experimental parameters was maintained, it was not possible to reproduce the stationary phases of the monolithic columns, since the relative standard deviation for the efficiencies obtained on columns prepared from the same polymerization mixture composition was 62%. The lack of repeatability for the efficiency is thought to be a result of limited homogeneity of the monolithic globular structures along the length of the majority of the prepared columns. The poor precision of preparation was justified by the copolymerization reaction that occurs in the presence of 2, 2′-azobisisobutyronitrile as the initiator agent, whose decomposition starts at the moment that this is added to the reaction mixture.

Sensitive determination of parabens in human urine and serum using methacrylate monoliths and reversed-phase capillary liquid chromatography–mass spectrometry

A method for the determination of parabens in human urine and serum by capillary liquid chromatography (cLC) with UV–Vis and mass spectrometry (MS) detection using methacrylate ester-based monolithic columns has been developed. The influence of composition of polymerization mixture was studied. The optimum monolith was obtained with butyl methacrylate monomer at 60/40% (wt/wt) butyl methacrylate/ethylene dimethacrylate ratio and 50wt% porogens (composed of 36wt% of 1,4-butanediol, 54wt% 1-propanol and 10wt% water). Baseline resolution of analytes was achieved through a mobile phase of acetonitrile/water in gradient elution mode. Additionally, dispersive liquid–liquid microextraction (DLLME) was combined with both cLC–UV–Vis and cLC–MS to achieve the determination of parabens in human urine and serum samples with very low limits of detection. Satisfactory intra- and inter-day repeatabilities were obtained in UV–Vis and MS detection, although the latter provided lower detection limits (up to 300-fold) than the UV–Vis detection. Recoveries for the target analytes from spiked biological samples ranged from 95.2% to 106.7%. The proposed methodology for the ultra-low determination of parabens in human urine and serum samples is simple and fast, the consumption of reagents is very low, and very small samples can be analyzed.

Vinylbenzyl quaternary ammonium-based polymeric monolith with hydrophilic interaction/strong anion exchange mixed-mode for pressurized capillary electrochromatography

A novel polymeric monolith with hydrophilic interaction and strong anion-exchange mixed-mode has been fabricated for pressurized capillary electrochromatography by an in situ copolymerization of vinylbenzyl trimethylammonium chloride (VBTA) and bisphenol A glycerolate dimethacrylate (BisGMA). The optimization of the polymerization mixture composition has been investigated, and column characteristics in terms of mechanical stability, permeability and reproducibility have been studied in detail. Linear responses between back pressure and flow rate have been achieved in different solvents. The absolute value of swelling propensity (SP) factor for poly(VBTA-co-BisGMA) monolith is 0.41, and the degree of permeability drop from pure ACN to water is about 45%. An acceptable mechanical stability of the column is obtained. The suitable reproducibility is also measured with the RSD for day-to-day (n=3) of retention time and column efficiency less than 3.3%, and the RSD for batch-to-batch (n=3) less than 5.3%, respectively. Under the optimum conditions, the mixed-mode of hydrophilic interaction and strong anion-exchange has been carried out, and efficient electrochromatography profiling of various polar compounds including neutral phenols, negatively charged benzoic acids and positively charged nucleic acid bases and nucleosides are achieved, respectively.

Recent advances in the design of organic polymer monoliths for reversed-phase and hydrophilic interaction chromatography separations of small molecules

Owing to their favorable porous structure with pore size distribution shifted towards large flow-through pores, organic polymer monoliths have been mainly employed for the separation of macromolecules in gradient elution liquid chromatography. The absence of significant amounts of small pores with a stagnant mobile phase and the resulting low surface area were considered as the main reason for their poor behavior in the isocratic separation of small molecules. Several recent efforts have improved the separation power of organic polymer monoliths for small molecules offering column efficiency up to tens of thousands of plates per meter. These attempts include optimization of the composition of polymerization mixture, including the variation of functional monomer, the cross-linking monomer, and the porogen solvents mixture, adjustment of polymerization temperature, and time. Additionally, post-polymerization modifications including hypercross-linking and the use of carbon nanostructures showed significant improvement in the column properties. This review describes recent developments in the preparation of organic polymer monoliths suitable for the separation of small molecules in the isocratic mode as well as the main factors affecting the column efficiency.

A molecularly imprinted monolith for the fast chiral separation of antiparasitic drugs by pressurized CEC

Molecularly imprinted polymer (MIP) monoliths with (S)-ornidazole ((S)-ONZ) as the template molecule have been designed and prepared by the simple thermal polymerization of methacrylic acid, 4-vinylpyridine, and ethylene dimethacrylate in the presence of a binary porogenic mixture of toluene and dodecanol. The influences of polymerization mixture composition on the chiral recognition of ONZ have been evaluated, and the imprint effect in the optimized MIP monolith has been clearly demonstrated. The new monolithic stationary phase with optimized porous property and good selectivity was used for the chiral separation of ONZ by pressurized CEC. The pressurized CEC conditions were also optimized to obtain the good chiral separation. The enantiomers were rapidly separated within 9 min on the MIP-based chiral stationary phase, whereas the chiral separation was not obtained on the nonimprinted polymer. Additionally, the proposed method has been successfully applied to the chiral separation of ONZ in tablet samples by injection of the crude sample. The cross-selectivity for similar antiparasitic drug was investigated. The results indicated that the chiral separation of secnidazole could also be obtained on the optimized MIP monolith within 14 min.

Fingerprint Development for Ginkgo biloba Extracts by Pressurized Capillary Electrochromatography: Comparison of Column Types

A pressurized capillary electrochromatographic (pCEC) fingerprint of Ginkgo biloba leaf extract was developed on three different types of capillary columns. A commercial column packed with 3-microm particles and an in-house column packed with 5-microm particles were investigated for their performance. Additionally, a monolithic column was included in the fingerprint study as a potential alternative to the conventional packed columns. The effects of experimental parameters, such as the composition of the mobile phase, the concentration and pH of the buffer, and the applied voltage, were studied. Binary mobile phases consisting of acetonitrile and a 5 mM sodium dihydrogen phosphate electrolyte at pH 2.8 were used in gradient elution mode with an applied voltage of 5 kV. Under optimal gradient conditions, at least 45 peaks were observed within 60 min on the commercial packed column, whereas only about 20 peaks were separated on the methacrylate-based monolithic and the in-house packed columns. The commercial column thus clearly outperforms the two other. However, the properties of the monolithic stationary phase still might be adapted (i.e., by changing the polymerization-mixture composition, the porosity, and thus the selectivity of the phase might be changed), which could lead to an improved efficiency.

Study of Selectivity of Molecularly Imprinted Polymers Prepared Under Different Conditions

Molecularly imprinted polymers were prepared and tested in different ways. 1-Methyl-2-piperidinoethylester of 4-decyloxyphenylcarbamic acid was used as the template for imprints formation. Acrylamide, 4-vinylpyridine, and methacrylic acid as monomers and methanol and acetonitrile as a porogene were used. Non-imprinted polymers were prepared for each imprinted polymer by the same procedure. Polymers were employed as sorbents for solid-phase extraction. In this work the influence of polymerization mixture composition on polymer properties, such as capacity and selectivity, was investigated. The influence of alkoxy-chain length and the position on benzene ring on the selectivity of polymers was also investigated.

Rapid determination of sterols in vegetable oils by CEC using methacrylate ester‐based monolithic columns

A method for the determination of sterols in vegetable oils by CEC with UV-Vis detection, using methacrylate ester-based monolithic columns, has been developed. To prepare the columns, polymerization mixtures containing monomers of different hydrophobicities were tried. The influence of composition of polymerization mixture was optimized in terms of porogenic solvent, monomers/porogens and monomer/crosslinker ratios. The composition of the mobile phase was also studied. The optimum monolith was obtained with lauryl methacrylate monomer at 60:40% (wt:wt) lauryl methacrylate/ethylene dimethacrylate ratio and 60 wt% porogens with 20 wt% of 1,4-butanediol (12 wt% 1,4-butanediol in the polymerization mixture). Excellent resolution between sterols was achieved in less than 7 min with an 85:10:5 v/v/v ACN-2-propanol-water buffer containing 5 mM Tris at pH 8.0. The limits of detection were lower than 0.04 mM, and inter-day and column-to-column reproducibilities at 0.75 mM were better than 6.2%. The method was applied to the determination of sterols in vegetable oils with different botanical origins and to detect olive oil adulteration with sunflower and soybean oils.

Investigation of Chromatographic Behavior and Porous Properties of Butyl Methacrylate Monolithic Columns

Monolithic columns based on butyl methacrylate were prepared inside capillaries of 320 µm inner diameter. The polymerization mixture consisted of monomer butyl methacrylate, crosslinker ethylene dimethacrylate, and ternary or binary porogen mixture. The chromatographic behavior of prepared columns was investigated via separation of selected solutes with different polarities. The morphology of monoliths was studied by mercury porosimetry and specific surface area measurements. The permeability of individual columns was closely connected to the pore radius. The separation efficiency was influenced by the specific surface area. A correlation between the polymerization mixture composition, the monolith morphology, and subsequently the chromatographic behavior was observed.

Monolithic capillary columns for liquid chromatography on the basis of ethylene glycol dimethacrylate

The effects of the synthesis conditions and polymerization mixture composition on the characteristics of monolithic capillary columns prepared from ethylene glycol dimethacrylate were studied. It was demonstrated that the content of the monomer in the initial mixture only slightly influences the efficiency of the columns obtained but, at the same time, causes a significant change in their separation impedance. By contrast, the temperature of synthesis strongly affects both these parameters. The efficiency of monolithic capillary columns prepared under optimum conditions was found to correspond to that of columns packed with a 5-µm-grained sorbent; however, the separation impedance of the former is substantially lower. A typical chromatogram of separation of a test mixture is presented.

Preparation and Characterization of Theophylline‐Imprinted Monolithic Column

Monolithic molecularly imprinted column was prepared by an in‐situ therm‐initiated copolymerization and the effects of essential preparation conditions such as polymerization mixture composition and polymerization condition was investigated. The results showed that the selection of correct porogenic solvents and appropriate polymerization conditions are crucial for the preparation of the monolithic stationary phases. The separation efficiency was only extremely weakly dependent on flow rate and hydrogen‐bonding interaction played an important role in the retention and separation. Compared with conventional particle columns and bulk molecular imprinted polymer column, the monolithic column exhibited good stability, ease of regeneration, high separation efficiency, and fast analysis.

Preparation and Characterization of Monolithic Poly(methacrylic acid - ethylene glycol dimethacrylate) Columns for High Performance Liquid Chromatography

Porous polymer monolithic columns were prepared by the direct free radical copolymerization of methacrylic acid and ethylene glycol dimethacrylate within the confines of a chromatographic column in the presence of toluene-dodecanol as a porogenic solvent. The separation characteristics of the monolithic columns were tested by a homologous series of xanthine derivatives, theophylline and caffeine. The effects of the polymerization mixture composition and polymerization condition, mobile phase composition, flow rate and temperature on the retention times and separation efficiencies were investigated. The results showed that the selection of correct porogenic solvents and appropriate polymerization conditions are crucial for the preparation of the monolithic stationary phases. The separation efficiency was only extremely weakly dependent on flow rate and temperatures. Hydrogen-bonding interaction played an important role in the retention and separation. Compared with conventional particle columns, the monolithic column exhibited good stability, ease of regeneration, high separation efficiency and fast analysis.

A new method to estimate pore volume of porous styrene–divinylbenzene copolymers

A new method to estimate the pore volume of porous styrene–divinylbenzene copolymer beads is proposed. The estimated pore volume (PV e) is based on the solubility parameters ( δ i ) and the corresponding weight fractions ( f i ) of styrene, divinylbenzenes and diluents in the polymerization mixture. The equation used is: PV e = 1.136 ∑δ if i 2− 21.193∑δ if i+ 98.825 . Regression analysis results show that an ideally close match of the predicted pore volume and the pore volume determined by mercury porosimeter is achieved with R 2=0.99, when non-polar and moderately polar liquids are employed as diluents. In the case of strongly polar (H-bonding) liquids as diluents, the method should be used only to predict a trend towards an increase or decrease in pore volume, which occurs as a result of variation in the composition of polymerization mixture.

Chiral monolithic columns for enantioselective capillary electrochromatography prepared by copolymerization of a monomer with quinidine functionality. 1. Optimization of polymerization conditions, porous properties, and chemistry of the stationary phase.

Monolithic columns for chiral capillary electrochromatography have been prepared within the confines of untreated fused-silica capillaries in a single step by a simple copolymerization of mixtures of O-[2-(methacryloyloxy)ethylcarbamoyl]-10,11-dihydroquinidine , ethylene dimethacrylate, and glycidyl methacrylate or 2-hydroxyethyl methacrylate in the presence of mixture of cyclohexanol and 1-dodecanol as a porogenic solvent. The porous properties of the monolithic columns can easily be controlled through changes in the composition of the binary porogenic solvent. Although both thermal- and UV light-initiated polymerizations afford useful capillary columns, monoliths prepared using the former approach exhibit better chromatographic properties. The ability to control pore size independently of the polymerization mixture composition enables the preparation of monoliths with varying percentages of the chiral monomer and cross-linker, as well as the optimization of their separation properties. Very good separations of model racemate (R,S)-N-3,5-dinitrobenzoylleucine were achieved using an optimized monolithic CEC column, with high efficiencies of up to 74000 plates/m for the retained peaks.

Kinetics and reaction mechanism of template polymerization investigated by conductimetric measurements. Part 3. Radical polymerization of acrylic acid in the presence of poly(N-vinylpyrrolidone)

Conductimetry was used for monitoring the radical polymerization of a weak electrolyte (acrylic acid) in aqueous solution and for determination of the kinetic parameters of the reaction (reaction order with respect to monomer, activation energy). The results obtained were consistent with those determined by other techniques (such as dilatometry) or expected from theory. Dilatometric and conductimetric measurements were also used to study the template polymerization of acrylic acid onto poly(N-vinylpyrrolidone). Results indicate that the reaction proceeds according to a pick-up mechanism. Complexes between poly(acrylic acid) and poly(N-vinylpyrrolidone) were always isolated in equimolar composition of the two polymers, regardless of the polymerization mixture composition. Spectroscopic evidence of the existence of strong interaction and intimate mixing of the two polymers in the complexes was found. An influence of the template molecular weight on the chain length of the forming poly(acrylic acid) was detected by means of viscometry. © 2000 Society of Chemical Industry