Monolithic columns based on a poly(styrene-divinylbenzene-methacrylic acid) copolymer for capillary liquid chromatography of small organic molecules (original) (raw)
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Methacrylate monolithic columns of 320 μm I.D. for capillary liquid chromatography
Journal of Chromatography A, 2002
Monolithic capillary columns (320 mm I.D.) were prepared for capillary liquid chromatography (CLC) by radical polymerization of butylmethacrylate (BMA) and ethylenedimethacrylate (EDMA) in the presence of a porogen solvent containing propan-1-ol, butane-1,4-diol and water. The influence of the contents of the porogen solvent and EDMA in the polymerization mixture on the monolith porosity and column efficiency was investigated. The composition of the polymerization mixture was optimized to attain a minimum HETP of the order of tens of mm for test compounds with various polarities. The separation performance and selectivity of the most efficient monolithic column prepared was characterized by van Deemter curves, peak asymmetry factors and Walters hydrophobicity and silanol indices. It was demonstrated that the 320-mm I.D. monolithic column exhibited CLC separation performance similar to that observed for 100-and 150-mm I.D. monolithic columns reported in the literature; moreover, the 320-mm I.D. column was easier to operate in CLC and exhibited a higher sample loadability.
Monolithic organic polymeric columns for capillary liquid chromatography and electrochromatography
Journal of Chromatography B, 2006
This review briefly summarizes the present state of the preparation and use of capillary monolithic columns for liquid chromatography (LC) and electrochromatography (EC). Most important approaches to the preparation of monolithic stationary phases based on organic polymers are outlined and the properties of the monoliths obtained are compared with those of classical particulate phases. A few selected applications of monolithic columns are shown to demonstrate the most important advantages of monolithic capillary columns. It is concluded that both the monolithic and particulate capillary columns are important and that judicious choice of the type suitable for a particular application requires careful consideration of the purpose of the separation and the properties of the solutes to be separated. Monolithic columns are substantially younger than packed ones and thus will require further theoretical and experimental study to further improve their preparation and to enable reliable prediction of their properties and applicability; nevertheless, they are very promising for the future.
Journal of Biochemical and Biophysical Methods, 2007
This paper describes the fabrication of long alkyl chain methacrylate monolithic materials for using as stationary phases in capillary liquid chromatography. Following deactivation of the capillary surface with 3-(trimethoxysilyl)propyl methacrylate (γ-MAPS), monoliths were formed by co-polymerisation of stearyl methacrylate (SMA) with ethylene glycol dimethacrylate (EDMA) in the presence of the initiator AIBN and a mixture of porogens including iso-amyl alcohol and 1,4-butanediol. The monoliths were prepared in 100 μm i.d. capillaries and the composition of the polymerisation mixtures were optimised in terms of the ratio of SMA/EDMA, the porogen composition and ratio of porogen to monomers. As the porogen weight fraction decreased, the microglobules became smaller and as expected, the total porosity decreased. In order to determine the usability of such materials, the column permeability K was measured by pumping water through the columns at different linear flow rates. Good results were obtained when these capillaries were used to separate mixtures of weak acids, neutral and basic compounds.
Preparation and Evaluation of Benzyl Methacrylate Monoliths for Capillary Chromatography
Journal of Chromatographic Science, 2014
This paper describes the comprehensive fabrication of monolithic materials for use as stationary phases in capillary liquid chromatography. Several columns were synthesized in the confines of 320 mm i.d. fused-silica capillaries by single-step in situ copolymerization of benzyl methacrylate and ethylene dimethacrylate (EDMA). The polymerization procedure was optimized by varying the reaction time within the range of 0.5-20 h, and by changing the composition contents of the polymeric mixture. The EDMA content showed a predominant influence on the characteristics of the columns and hence, on their chromatographic properties. The optimum value of the thermal initiator corresponded to 5 mg/mL. Changes of the porous, hydrodynamic properties and morphology of the prepared columns were thoroughly investigated and characterized. Different solvents were used as the mobile phase to demonstrate that the resulting monoliths exhibited good permeability and mechanical stability, whereas swelling and shrinking behaviors were observed and discussed. The efficiency and performance toward different sets of analytes were obtained; mixtures of aromatic hydrocarbons and phenolic compounds were successfully separated and evaluated, and adding tetrahydrofuran to the mobile phase showed improvement in both resolution and peak shapes. The characteristics of the columns were also checked in terms of repeatability and reproducibility. Experimental Chemicals and columns Formic acid, benzene, naphthalene, 4-aminophenol, mnitrophenol and other chemicals used in the experiments were of analytical grade and purchased from BDH (Lutterworth, UK). 2-Naphthol and anthracene were provided by Merck
Journal of Chromatography A, 2008
A new polystyrene-based monolithic stationary phase, which was prepared by single step in situ copolymerization of styrene, divinylbenzene and vinylbenzenesulfonic acid (VBSA), was developed as a separation column for capillary electrochromatography, in which VBSA was employed as the chargebearing monomer. Polymerization time of the polystyrene-based monolith had slightly influenced the separation time of the tested analytes, but it effectively altered their separation resolutions. Furthermore, baseline separation for a wider range of acetonitrile levels of mobile phase was achieved when a monolithic column prepared by a longer polymerization time was used. This novel polystyrene-based monolithic column provided an adequate electroosmotic flow either in basic or acidic mobile phase when VBSA level was maintained at 2.6% (w/w). Finally, this proposed polystyrene-based column allowed seven tested analytes to achieve a reproducible baseline separation within 2.2 min with theoretical plate numbers higher than 164 000 plates/m.
Asian Journal of Chemistry, 2014
Capillary liquid chromatography has been one of the most important recent developments in separation and analysis technology. Capillary liquid chromatography offers several advantages over conventional normal chromatography. The advantages include increased chromatographic resolution, higher efficiency, lower sample and solvent consumption, the ability to analyze and isolate rare compounds of interest, greater mass sensitivity and ease of on-line connection to a mass spectrometer 1-3. Traditionally, capillary liquid chromatography uses fused silica capillaries prepared with a variety of stationary phases. This technique appears to be very promising for separating a wide variety of analytes for different applications 4-10. However, the successful development of this technique is closely related to the technical challenges associated with manufacturing the column. Monolithic columns have quickly become extremely popular and they have attracted increasing interest as separation media for all chromatographic methods. The unique structure of the monoliths and their ease of preparation offer improved chromatographic performance and favorable properties that
Journal of Chromatographic Science, 2012
Butyl methacrylate (BMA)-ethylene dimethacrylate (EDMA)-methacrylic acid (MAA) and BMA-EDMA-2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) monolithic columns were prepared by varying the percentage of ionic monomers for capillary electrochromatography. Monolithic columns with a higher content of ionic monomers provided better column efficiency, and the performance of BMA-EDMA-MAA monoliths was better than BMA-EDMA-AMPS. To characterize and optimize BMA-EDMA-MAA monoliths, the effects of the content of cross-linker and the total monomer in the polymerization mixture on column performance were also studied. Plate heights of 8.2 mm for the unretained solute (thiourea) and 12.6 mm for the retained solute (naphthalene) were achieved with a monolithic column using 2.5% MAA (Column I).
Journal of Polymer Science Part A: Polymer Chemistry, 2000
Rapid high-performance liquid chromatography (HPLC) of polystyrenes, poly(methyl methacrylates), poly(vinyl acetates), and polybutadienes using a monolithic 50 ϫ 4.6 mm i.d. poly(styrene-co-divinylbenzene) column have been carried out. The separation process involves precipitation of the macromolecules on the macroporous monolithic column followed by progressive elution utilizing a gradient of the mobile phase. Depending on the character of the separated polymer, solvent gradients were composed of a poor solvent such as water, methanol, or hexane and increasing amounts of a good solvent such as THF or dichloromethane. Monolithic columns are ideally suited for this technique because convection through the large pores of the monolith enhances the mass transport of large polymer molecules and accelerates the separation process. Separation conditions including the selection of a specific pair of solvent and precipitant, flow rate, and gradient steepness were optimized for the rapid HPLC separations of various polymers that differed broadly in their molecular weights. Excellent separations were obtained demonstrating that the precipitation-redissolution technique is a suitable alternative to size-exclusion chromatography (SEC). The molecular weight parameters calculated from the HPLC data match well those obtained by SEC. However, compared to SEC, the determination of molecular parameters using gradient elution could be achieved at comparable flow rates in a much shorter period of time, typically in about 1 min.