monolithic silica columns
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This study introduces zwitterionic monolithic capillary columns intended for isocratic and gradient HILIC separations. Silica-based monolithic capillary columns (100 μm × 150 mm) prepared by acidic hydrolysis of tetramethoxysilane in the presence of polyethylene glycol and urea were modified by a sulfoalkylbetaine zwitterion ([2-(methacryloyloxy)ethyl]-dimethyl-(3-sulfopropyl)-ammonium hydroxide) to HILIC stationary phase. The prepared columns were evaluated under the isocratic and gradient separation conditions using a standard mixture containing nucleic acid bases, nucleosides, and 2-deoxynucleosides. Mobile phases contained high concentration of acetonitrile (95-85%, v/v) and 5-50mM ammonium acetate or ammonium formate in the pH range of 3-6. The synthesized columns showed a long-term stability under the separation conditions while the high permeability and efficiency originating from dual structure of the silica monolith were preserved. The relative standard deviations (RSDs) for the retention times of tested solutes were lower than 2% under the isocratic conditions and lower than 3.5% under the gradient conditions.
- MeSH
- acetonitrily chemie MeSH
- betain analogy a deriváty chemie MeSH
- chromatografie kapalinová přístrojové vybavení metody MeSH
- hydrofobní a hydrofilní interakce MeSH
- nukleosidy chemie izolace a purifikace MeSH
- nukleové kyseliny chemie izolace a purifikace MeSH
- oxid křemičitý chemie MeSH
- reprodukovatelnost výsledků MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
We studied possibilities of prediction of the gradient elution data for alkylbenzenes, flavones and phenolic acids on two short octadecyl silica gel monolithic columns, namely a Chromolith Flash C18, 25×4.6mm, and a "new generation" Chromolith High Resolution C18, 50×4.6mm, in fast 1-2min gradients. With fixed short gradient times and varying gradient ranges of acetonitrile concentration in water, high flow rates of the mobile phase (3-5mL/min) could be used. The gradient elution data were predicted from four gradient models based on two-parameter and three-parameter isocratic retention equations. Various gradient retention models can be used for prediction of chromatograms and optimization of separation within a fixed gradient time. A two-parameter log-log model introduced in 1974 and a three-parameter model introduced in 1980 provided slightly more accurate prediction than the Linear Solvent Strength (LSS) semi-logarithmic two-parameter model, most frequently used in reversed-phase LC. A three-parameter model introduced in 1978 provided slightly improved accuracy of prediction of gradient data with respect to two-parameter models, in contrast to another, more recent three-parameter empirical model introduced in 2010 (which failed for gradients starting at a non-zero concentration of acetonitrile). Both a longer (5cm) and more efficient Chromolith HR column and a shorter (2.5cm) slightly less efficient Chromolith Flash column provide useful separations in fast gradients (1-2min) at high flow rates (3.5-5mL/min), especially in second dimension of two-dimensional LC×LC, in combination with HILIC separation on monolithic microcolumn in D1.
The capability of employing synthesized zwitterionic silica-based monolithic capillary columns (140 mm × 0.1mm) for separation of highly polar and hydrophilic nucleobases, nucleosides, and nucleotides in hydrophilic interaction chromatography is reported. The suitability of the columns for on-line conjunction with electrospray tandem mass spectrometry was explored. Our results show that the grafted layer of zwitterionic monomer ([2-(methacryloyloxy)ethyl]-dimethyl-(3-sulfopropyl)-ammonium hydroxide or 2-methacryloyloxyethyl phosphorylcholine) on the silica monolithic surface significantly improved the separation selectivity and reproducibility, as compared to the bare silica monolith. The stepwise elution from 90% to 70% of acetonitrile enabled separation of a complex sample mixture containing 21 compounds with a total analysis time less than 40 min.
- MeSH
- hmotnostní spektrometrie s elektrosprejovou ionizací přístrojové vybavení metody MeSH
- hydrofobní a hydrofilní interakce MeSH
- nukleosidy chemie izolace a purifikace MeSH
- nukleotidy chemie izolace a purifikace MeSH
- oxid křemičitý chemie MeSH
- povrchové vlastnosti MeSH
- reprodukovatelnost výsledků MeSH
- tandemová hmotnostní spektrometrie přístrojové vybavení metody MeSH
- vysokoúčinná kapalinová chromatografie metody MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The temperature effects during the sol-gel process and ageing of the silica-based monolith on the structure and separation efficiency of the capillary columns (100microm i.d., 150mm) for HPLC separations were studied. The tested columns were synthesized from a mixture of tetramethoxysilane, polyethylene glycol and urea under the acidic conditions. The temperature was varied from 40 degrees C to 44 degrees C and formation of bypass channels between the silica mold and the capillary wall was examined. The temperature of 43 degrees C was estimated as optimal for preparation of efficient silica capillary columns which were subsequently modified by octadecyldimethyl-N,N-diethylaminosilane or covered by poly(octadecyl methacrylate) and tested using standard mixture of alkylbenzenes under the isocratic conditions.
- MeSH
- benzenové deriváty chemie MeSH
- koncentrace vodíkových iontů MeSH
- mikroskopie elektronová rastrovací MeSH
- močovina chemie MeSH
- oxid křemičitý chemie MeSH
- polyethylenglykoly chemie MeSH
- silany chemie MeSH
- teplota MeSH
- vysokoúčinná kapalinová chromatografie metody MeSH
- změna skupenství MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
This study introduces a silica-based monolith in a capillary format (0.1 mm × 100 mm) as a support for immobilization of liposomes and its characterization in immobilized liposome chromatography. Silica-based monolithic capillary columns prepared by acidic hydrolysis of tetramethoxysilane in the presence of polyethylene glycol and urea were modified by (3-aminopropyl)trimethoxysilane, whereby amino groups were introduced to the monolithic surface. These groups undergo reaction with glutaraldehyde to form an iminoaldehyde, allowing covalent binding of pre-formed liposomes containing primary amino groups. Two types of phospholipid vesicles were used for column modification; these were 2-oleoyl-1-palmitoyl-sn-glycero-3-phosphatidyl choline with and without 1,2-diacyl-sn-glycero-3-phospho-L-serine. The prepared columns were evaluated under isocratic separation conditions employing 20mM phosphate buffer at pH 7.4 as a mobile phase and a set of unrelated drugs as model analytes. The liposome layer on the synthesized columns significantly changed the column selectivity compared to the aminopropylsilylated monolithic stationary phase. Monolithic columns modified by liposomes were stable under the separation conditions, which proved the applicability of the suggested preparation procedure for the synthesis of capillary columns dedicated to study analyte-liposome interactions. The column efficiency originating from the silica monolith was preserved and reached, e.g., more than 120,000 theoretical plates/m for caffeine as a solute.
A monolithic sulfobetaine polymethacrylate micro-column BIGDMA-MEDSA designed in our laboratory, shows dual retention mechanism: In acetonitrile-rich mobile phase, hydrophilic interactions control the retention (HILIC system), whereas in more aqueous mobile phases the column shows essentially reversed-phase behavior with major role of hydrophobic interactions. The zwitterionic polymethacrylate micro-column can be used in the first dimension of two-dimensional LC in alternating reversed-phase (RP) and HILIC modes, coupled with an alkyl-bonded core-shell or silica-based monolithic column in the second dimension, for HILIC×RP and RP×RP comprehensive two-dimensional separations. During the HILIC×RP period, a gradient of decreasing acetonitrile gradient is used for separation in the first dimension, so that at the end of the gradient the polymeric monolithic micro-column is equilibrated with a highly aqueous mobile phase and is ready for repeated sample injection, this time for separation under reversed-phase gradient conditions with increasing concentration of acetonitrile in the first dimension. The fast repeating reversed-phase gradients on a short silica-monolithic or core-shell column in the second dimension can be optimized independently of the actual running first-dimension gradient program. As the alternating HILIC and RP separations on the first-dimension zwitterionic methacrylate column are based on complementary retention mechanisms, the instrumental setup essentially represents two coupled two-dimensional systems. It is first time that such an automated dual LCxLC approach is reported. The novel system allows obtaining three-dimensional data in a relatively short time and can be applied not only to multidimensional gradient separations of flavones and related polyphenolic compounds.
- MeSH
- acetonitrily MeSH
- betain analogy a deriváty MeSH
- chromatografie kapalinová přístrojové vybavení metody MeSH
- chromatografie s reverzní fází přístrojové vybavení metody MeSH
- flavony izolace a purifikace MeSH
- hydrofobní a hydrofilní interakce MeSH
- hydroxybenzoáty izolace a purifikace MeSH
- kyseliny polymethakrylové * MeSH
- oxid křemičitý * MeSH
- rozpouštědla MeSH
- voda MeSH
- Publikační typ
- časopisecké články MeSH
This review article is an updated and extended version of the previous review that has been published 14 years ago . Although history does not change, its interpretation may. Therefore, I took the liberty to revisit the original work and added some of my new thoughts that could be interesting for the generation of scientists who are entering the intriguing arena of monoliths and may want to know the roots of the field. The current monolithic columns that are well applicable for efficient separations, were first described less than 30 years ago, and their advent represented the initial step to their present widespread appearance. At the beginning, the monolithic columns dominated the academic studies. However, several monolithic materials have later been materialized in commercial products. In order to stay within a reasonable size of this contribution, its focus is placed on developments achieved in the previous century. The very early reports are described in more detail since it might be difficult to find the original source.
Monolithic continuous separation media are gradually finding their way to sample pre-treatment, isolation, enrichment and final analytical separations of a plethora of compounds, occurring as food components, additives or contaminants, including pharmaceuticals, pesticides and toxins, which have traditionally been the domain of particulate chromatographic materials. In the present review, recent advances in the technology of monolithic columns and the applications in food analysis are addressed. Silica-based monoliths are excellent substitutes to conventional particle-packed columns, improving the speed of analysis for low-molecular weight compounds, due to their excellent efficiency and high permeability. These properties have been recently appreciated in two-dimensional HPLC, where the performance in the second dimension is of crucial importance. Organic-polymer monoliths in various formats provide excellent separations of biopolymers. Thin monolithic disks or rod columns are widely employed in isolation, purification and pre-treatment of sample containing proteins, peptides or nucleic acid fragments. Monolithic capillaries were originally intended for use in electrochromatography, but are becoming more frequently used for capillary and micro-HPLC. Monoliths are ideal highly porous support media for immobilization or imprinting template molecules, to provide sorbents for shape-selective isolation of target molecules from various matrices occurring in food analysis. The separation efficiency of organic polymer monoliths for small molecules can be significantly improved by optimization of polymerization approach, or by post-polymerization modification. This will enable full utilization of a large variety of available monomers to prepare monoliths with chemistry matching the needs of selectivity of separations of various food samples containing even very polar or ionized compounds.
The synthesis and characterization of large-bore silica-based monolithic capillary columns (0.32mm×150mm) are presented. Columns were prepared by acidic hydrolysis of a mixture containing tetramethoxysilane (TMOS) and 1,2-bis(trimethoxysilyl)ethane (BTME) in different molar ratios in the presence of polyethylene glycol and urea. The monoliths were modified by zwitterionic monomer [2-(methacryloyloxy)ethyl]-dimethyl-(3-sulfopropyl)-ammonium hydroxide via 3-(trimethoxysilyl)propyl methacrylate. Prepared stationary phases were evaluated by scanning electron microscopy and chromatographic separation of nucleobases and their derivatives in the HILIC mode. The best chromatographic results were obtained with the column prepared from the reaction mixture containing BTME and TMOS in a 1:4 molar ratio. The permeability of such column reached 1.68×10(-14)m(2) and the efficiency, expressed as a height equivalent of the theoretical plate, did not exceed 10.5μm for the tested compounds. The columns were successfully applied to HILIC separation of native and labeled oligosaccharides and glycans released from bovine ribonuclease B and human immunoglobulin G.
- MeSH
- chromatografie kapalinová přístrojové vybavení metody MeSH
- ethan analogy a deriváty chemie MeSH
- hmotnostní spektrometrie s elektrosprejovou ionizací MeSH
- hydrofobní a hydrofilní interakce MeSH
- imunoglobulin G metabolismus MeSH
- lidé MeSH
- methakryláty chemie MeSH
- mikroskopie elektronová rastrovací MeSH
- oligosacharidy analýza izolace a purifikace MeSH
- organické sloučeniny křemíku chemie MeSH
- oxid křemičitý chemie MeSH
- ribonukleasy metabolismus MeSH
- skot MeSH
- trimethylsilylové sloučeniny chemie MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- skot MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
