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Silica Column (silica + column)
Selected AbstractsCapillary electrochromatography with monolithic silica column:,I.ELECTROPHORESIS, Issue 3 2003Preparation of silica monoliths having surface-bound octadecyl moieties, applications to the separation of neutral, charged species, their chromatographic characterization Abstract Monolithic silica columns with surface-bound octadecyl (C18) moieties have been prepared by a sol-gel process in 100 ,m ID fused-silica capillaries for reversed-phase capillary electrochromatography of neutral and charged species. The reaction conditions for the preparation of the C18-silica monoliths were optimized for maximum surface coverage with octadecyl moieties in order to maximize retention and selectivity toward neutral and charged solutes with a sufficiently strong electroosmotic flow (>,2 mm/s) to yield rapid analysis time. Furthermore, the effect of the pore-tailoring process on the silica monoliths was performed over a wide range of treatment time with 0.010 M ammonium hydroxide solution in order to determine the optimum time and conditions that yield mesopores of narrow pore size distribution that result in high separation efficiency. Under optimum column fabrication conditions and optimum mobile phase composition and flow velocity, the average separation efficiency reached 160,000 plates/m, a value comparable to that obtained on columns packed with 3 ,m C18-silica particles with the advantages of high permeability and virtually no bubble formation. The optimized monolithic C18-silica columns were evaluated for their retention properties toward neutral and charged analytes over a wide range of mobile phase compositions. A series of dimensionless retention parameters were evaluated and correlated to solute polarity and electromigration property. A dimensionless mobility modulus was introduced to describe charged solute migration and interaction behavior with the monolithic C18-silica in a counterflow regime during capillary electrochromatography (CEC )separations. The mobility moduli correlated well with the solute hydrophobic character and its charge-to-mass ratio. [source] Application of hydrophilic interaction chromatography retention coefficients for predicting peptide elution with TFA and methanesulfonic acid ion-pairing reagentsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 6-7 2010Chad E. Wujcik Abstract Hydrophilic retention coefficients for 17 peptides were calculated based on retention coefficients previously published for TSKgel silica-60 and were compared with the experimental elution profile on a Waters Atlantis HILIC silica column using TFA and methanesulfonic acid (MSA) as ion-pairing reagents. Relative peptide retention could be accurately determined with both counter-ions. Peptide retention and chromatographic behavior were influenced by the percent acid modifier used with increases in both retention and peak symmetry observed at increasing modifier concentrations. The enhancement of net peptide polarity through MSA pairing shifted retention out by nearly five-fold for the earliest eluting peptide, compared with TFA. Despite improvements in retention and efficiency (Neff) for MSA over TFA, a consistent reduction in calculated selectivity (,) was observed. This result is believed to be attributed to the stronger polar contribution of MSA masking and diminishing the underlying influence of the amino acid residues of each associated peptide. Finally, post-column infusion of propionic acid and acetic acid was evaluated for their potential to recover signal intensity for TFA and MSA counter-ions for LC-ESI-MS applications. Acetic acid generally yielded more substantial signal improvements over propionic acid on the TFA system while minimal benefits and some further reductions were noted with MSA. [source] Performance of wide-pore monolithic silica column in protein separationJOURNAL OF SEPARATION SCIENCE, JSS, Issue 15-16 2009Hironobu Morisaka Abstract A monolithic wide-pore silica column was newly prepared for protein separation. The wide distribution of the pore sizes of monolithic columns was evaluated by mercury porosimetry. This column, as well as the conventional monolithic column, shows high permeability in the chromatographic separation of low-molecular-sized substances. In higher-molecular-sized protein separation, the wide-pore monolithic silica column shows better performance than that of the conventional monolithic column. Under optimized conditions, five different proteins , ribonuclease A, albumin, aldolase, catalase, and ferritin , were baseline-separated within 3 min, which is faster than that using the particle-packed columns. In addition, the monolithic wide-pore silica column could also be prepared in fused silica capillary (600 mm long, 0.2 mm i.d.) for highly efficient protein separation. The peak capacity of the wide-pore monolithic silica capillary column is estimated to be approximately 300 in the case of protein separation, which is a characteristic performance. [source] Evaluation of mobile phase, ion pairing, and temperature influence on an HILIC-MS/MS method for L -arginine and its dimethylated derivatives detectionJOURNAL OF SEPARATION SCIENCE, JSS, Issue 13 2008Giuseppe Paglia Abstract Asymmetric NG,,NG -dimethylarginine (ADMA) increases in diseases such as renal failure, diabetes mellitus, and hypercholesterolemia. The feasibility and utility of a hydrophilic interaction chromatography (HILIC) method for the separation of free L -arginine (Arg), ADMA, and symmetric NG,,NG, -dimethylarginine (SDMA) on a typical silica column were explored and the impact of some experimental parameters on the chromatographic behavior of these analytes was investigated. The effect of water and TFA content in mobile phase and of column temperature was investigated during the development of a fast and simple HILIC-MS/MS method that might be suitable for the quantification of free Arg, ADMA, and SDMA in plasma for routine analysis. Our results show that a good compromise between efficiency and peak shape with acceptable retention and total chromatographic run time is achieved using an ACN/water (90:10) mobile phase with TFA% as additive ranging from 0.015 to 0.025% and column temperature ranging from 25 to 30°C. [source] Simple 2D-HPLC using a monolithic silica column for peptide separationJOURNAL OF SEPARATION SCIENCE, JSS, Issue 10-11 2004Hiroshi Kimura Abstract Separation of peptides by fast and simple two-dimensional (2D)-HPLC was studied using a monolithic silica column as a second-dimension (2nd-D) column. Every fraction from the first column, 5 cm long (2.1 mm ID) packed with polymer-based cation exchange beads, was subjected to separation in the 2nd-D using an octadecylsilylated (C18) monolithic silica column (4.6 mm ID, 2.5 cm). A capillary-type monolithic silica C18 column (0.1 mm ID, 10 cm) was also employed as a 2nd-D column with split flow/injection. Effluent of the first dimension (1st-D) was directly loaded into an injector loop of 2nd-D HPLC. UV and MS detection were successfully carried out at high linear velocity of mobile phase at 2nd-D using flow splitting for the 4.6 mm ID 2nd-D column, or with direct connection of the capillary column to the MS interface. Two-minute fractionation in the 1st-D, 118-second loading, and 2-second injection by the 2nd-D injector, allowed one minute for gradient separation in the 2nd-D, resulting in a maximum peak capacity of about 700 within 40 min. The use of a capillary column in the 2nd-D led to less solvent consumption and better MS detectability compared to a larger-sized column. This kind of fast and simple 2D-HPLC utilizing monolithic silica columns will be useful for the separation of complex mixtures in a short time. [source] Reduced-bore monolithic silica column modified with C8 -TEOS for reversed-phase electrochromatographyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 9 2004Qishu Qu Abstract Monolithic silica columns of 2.7 mm ID were prepared and derivatized with C8 -TEOS and TEOS by on-column sol-gel reaction. These C8 large diameter monolithic silica columns gave 21 000 theoretical plates for aromatic hydrocarbons in 60% acetonitrile and 40% Tris-HCl buffer. The surface areas as well as the separation reproducibility were improved on coating by the sol-gel approach. Joule heating was greatly reduced by using monolithic columns to which fine quartz sand had been added during column preparation. Since this is a preliminary investigation on a monolithic column with such a large inner diameter, the separation efficiency was not so high as that presently achieved in normal capillary electrochromatography (CEC). However, use of the columns improved sample loadability and concentration detectability of electrochromatography, and semi-preparative separations could be performed. [source] Determination of the purity of ampicillin by micellar electrokinetic chromatography and reversed phase liquid chromatography on a monolithic silica columnJOURNAL OF SEPARATION SCIENCE, JSS, Issue 7-8 2004Milada Dole, alová Abstract A micellar electrokinetic chromatographic (MEKC) method and a fast reversed-phase liquid chromatographic one have been developed for determining the purity of ampicillin. MEKC separation of ampicillin and its related substances was performed with the use of an untreated fused-silica capillary and 40 mM phosphate-borate buffer, pH 7.5 containing 75 mM SDS. The HPLC method employed a monolithic silica C18 column and a mobile phase composed of phosphate buffer, pH 5.2 and ACN, the flow rate being 4.0 mL/min. Both methods were successfully validated. Linearity, relative response factors, limits of quantitation, intermediate precision, and accuracy were evaluated. The methods proved to be fast, reliable, and sufficiently sensitive and, accordingly, well-suited for control of purity of ampicillin substance, injections, and capsules. A combination of both methods can be very useful in the confirmation of impurity profiles. [source] Comparison of two sample clean-up methodologies for the determination of polycyclic aromatic hydrocarbons in edible oilsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 17 2003Alejandro Barranco Abstract An off-line high-performance normal-phase liquid chromatography procedure with a silica column followed by reversed-phase high-performance liquid chromatography (HPLC) with fluorescence detection for the determination of polycyclic aromatic hydrocarbons (PAHs) in edible oils is reported. The method was validated using certified reference materials and compared with a standardized method widely used in the food industry, consisting in low pressure column chromatography with alumina as stationary phase followed by reversed phase HPLC determination. The limits of detection were lower than 1 ng/g and good selectivity was achieved for both methods. There were no significant differences in accuracies and precisions obtained for each approach. The advantages and disadvantages of the two methods are discussed. [source] Recovery of plant DNA using a reciprocating saw and silica-based columnsMOLECULAR ECOLOGY RESOURCES, Issue 1 2007PATRICK J. ALEXANDER Abstract The time needed for hand grinding and the cost of commercially available extraction kits remain to be the major limitations in plant DNA extraction for many researchers. We present inexpensive techniques for (i) simultaneously machine grinding large numbers of plant samples for DNA extraction using a commercially available reciprocating saw; and (ii) DNA recovery using silica column-based extractions similar to that used in some commercially available kits. Used together, these allow for the rapid recovery of plant DNA at relatively low cost. Furthermore, these methods appear to be widely applicable within plants with good yields recovered in test extractions across major plant groups (ferns, gymnosperms, monocots and eudicots). [source] Direct determination of endogenous melatonin in human saliva by column-switching semi-microcolumn liquid chromatography/mass spectrometry with on-line analyte enrichmentRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 12 2004Akira Motoyama An analytical method that enables direct and sensitive determination of endogenous melatonin (MLT) in human saliva was developed by means of column-switching semi-microcolumn liquid chromatography (i.d.: 1,2,mm)/mass spectrometry (LC/MS). The system allows direct injection analysis of a 400-,L aliquot of saliva with minimal sample pretreatment (internal standard (IS) addition and vortex mixing) and a relatively short run-time (10,min). The system consists of three columns to attain large volume injection and on-line analyte enrichment. A pre-column packed with a silica-based mixed-functional C8 (4.0,mm i.d.,×,20,mm) was used for on-line sample cleanup. MLT and an IS, the d7 isomer of MLT (d7-MLT), were heart-cut by valve switching and enriched at the top of the intermediate trapping column packed with a silica-based C18 (4.0,mm i.d.,×,10,mm). Subsequently, the analytes were backflushed into a semi-micro C18 silica column (2.0,mm i.d.,×,150 mm) for the final separation. MLT and IS were ascertained by positive electrospray ionization and selected ion monitoring (SIM). MLT was monitored based on its fragment ion at m/z 174.1 by in-source collision-induced dissociation (CID). The validation of this method revealed a detection limit of 2.5,pg,mL,1 at a signal-to-noise (S/N) ratio of 5. The linearity of the method was established in the ranges 5,250 and 100,2500,pg,mL,1 with a coefficient of determination of greater than 0.998. Accuracies, evaluated at five levels in the range 5,1000,pg,mL,1, were between 81 and 108% with a relative standard deviation (RSD) ranging from 1.3,20%. The method was successfully applied for the endogenous saliva MLT monitoring of two healthy subjects. Copyright © 2004 John Wiley & Sons, Ltd. [source] A highly automated 96-well solid phase extraction and liquid chromatography/tandem mass spectrometry method for the determination of fentanyl in human plasmaRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 7 2001Wilson Z. Shou A high-throughput bioanalytical method based on automated sample transfer, automated solid phase extraction, and fast liquid chromatography/tandem mass spectrometry (LC/MS/MS) analysis, has been developed for the determination of the analgesic fentanyl in human plasma. Samples were transferred into 96-well plates using an automated sample handling system. Automated solid phase extraction (SPE) was carried out using a 96-channel programmable liquid-handling workstation using a mixed-mode sorbent. The extracted samples were then dried down, reconstituted and injected onto a silica column using an aqueous/organic mobile phase with tandem mass spectrometric detection. The method has been validated over the concentration range 0.05,100,ng/mL fentanyl in human plasma, based on a 0.25-mL sample size. The assay is sensitive, specific and robust. More than 2000 samples have been analyzed using this method. The automation of the sample preparation steps not only increased the analysis throughput, but also facilitated the transfer of the method between different bioanalytical laboratories of the same organization. Copyright© 2001 John Wiley & Sons, Ltd. [source] Determination of bevantolol enantiomers in human plasma by coupled achiral,chiral high performance-liquid chromatographyCHIRALITY, Issue 7 2007Joung Weon Oh Abstract A coupled achiral,chiral high performance liquid chromatographic method was developed and fully validated for the determination of bevantolol enantiomers, (,)-(S)-bevantolol and (+)-(R)-bevantolol, in human plasma. Plasma samples were prepared by solid phase extraction with Sep-Pak Plus C18 cartridges followed by HPLC. Bevantolol enantiomers and (+)-(R)-Propranolol as internal standard (IS) were preseparated from interfering components in plasma on a Phenomenex silica column and bevantolol enantiomers and IS were resolved and determined on a Chiralcel OJ-H chiral stationary phase. The two columns were connected by a switching valve equipped with silica precolumn. The Precolumn was used to concentrate bevantolol in the eluent from the achiral column before back flushing onto chiral phase. A detailed validation of the method was performed accordingly to FDA guidelines. For each enantiomer the assay was linear between 20 and 1600 ng/ml. The quantification limits of both bevantolol enantiomers were 20 ng/ml. The intraday variation was between 1.07 and 12.64% in relation to the measured concentration and the interday variation was 0.91 and 11.79%. The method has been applied to the determination of (,)-(S)- and (+)-(R)-bevantolol in plasma from healthy volunteers dosed with racemic bevantolol hydrochloride. hydrochloride. Chirality, 2007. © 2007 Wiley-Liss, Inc. [source] Capillary electrochromatography with monolithic silica column:,I.ELECTROPHORESIS, Issue 3 2003Preparation of silica monoliths having surface-bound octadecyl moieties, applications to the separation of neutral, charged species, their chromatographic characterization Abstract Monolithic silica columns with surface-bound octadecyl (C18) moieties have been prepared by a sol-gel process in 100 ,m ID fused-silica capillaries for reversed-phase capillary electrochromatography of neutral and charged species. The reaction conditions for the preparation of the C18-silica monoliths were optimized for maximum surface coverage with octadecyl moieties in order to maximize retention and selectivity toward neutral and charged solutes with a sufficiently strong electroosmotic flow (>,2 mm/s) to yield rapid analysis time. Furthermore, the effect of the pore-tailoring process on the silica monoliths was performed over a wide range of treatment time with 0.010 M ammonium hydroxide solution in order to determine the optimum time and conditions that yield mesopores of narrow pore size distribution that result in high separation efficiency. Under optimum column fabrication conditions and optimum mobile phase composition and flow velocity, the average separation efficiency reached 160,000 plates/m, a value comparable to that obtained on columns packed with 3 ,m C18-silica particles with the advantages of high permeability and virtually no bubble formation. The optimized monolithic C18-silica columns were evaluated for their retention properties toward neutral and charged analytes over a wide range of mobile phase compositions. A series of dimensionless retention parameters were evaluated and correlated to solute polarity and electromigration property. A dimensionless mobility modulus was introduced to describe charged solute migration and interaction behavior with the monolithic C18-silica in a counterflow regime during capillary electrochromatography (CEC )separations. The mobility moduli correlated well with the solute hydrophobic character and its charge-to-mass ratio. [source] Hydrophilic interaction LC of peptides: Columns comparison and clusteringJOURNAL OF SEPARATION SCIENCE, JSS, Issue 6-7 2010Sylvia Van Dorpe Abstract A wide variety of hydrophilic interaction chromatography (HILIC) stationary phase surface chemistries are currently available. Although their selectivity can be considerably different, column comparison or clustering using peptides is limited. In this study, ten pharmaceutically relevant model peptides are analyzed on seven different HILIC columns (bare silica, amide, poly-hydroxyethyl aspartamide, diol and zwitterionic) for the evaluation of their performance and classification. The responses examined include single and multiple responses: plate number, asymmetry factor, LOD, geometric mean resolution, resolution product, time corrected resolution product, peak capacity and chromatographic response function. Column classification was performed using hierarchical clustering and principal component analysis. Moreover, the overall performance quality of the HILIC columns was compared using a linear desirability function. Hierarchical clustering and principal component analysis showed consistent clusters. The zwitterionic phase was clustered apart from the other HILIC columns and both poly-aspartamide columns were clustered together. In addition, the two bare silica phases represent two different clusters, and thus different selectivities. Overall, the responses showed the best performance for one of the bare silica columns (Alltima-Alltech), followed by the zwitterionic phase (ZIC)-HILIC. Thus, these columns, belonging to different clusters, were found to be the best performing systems in pharmaceutical peptide analysis for the selected peptide set. [source] Spherical ordered mesoporous silicas and silica monoliths as stationary phases for liquid chromatographyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 6 2006Anne Galarneau Abstract Ordered mesoporous silicas such as micelle-templated silicas (MTS) feature unique textural properties in addition to their high surface area (,1000 m2/g): narrow mesopore size distributions and controlled pore connectivity. These characteristics are highly relevant to chromatographic applications for resistance to mass transfer, which has never been studied in chromatography because of the absence of model materials such as MTS. Their synthesis is based on unique self-assembly processes between surfactants and silica. In order to take advantage of the perfectly adjustable texture of MTS in chromatographic applications, their particle morphology has to be tailored at the micrometer scale. We developed a synthesis strategy to control the particle morphology of MTS using the concept of pseudomorphic transformation. Pseudomorphism was recognized in the mineral world to gain a mineral that presents a morphology not related to its crystallographic symmetry group. Pseudomorphic transformations have been applied to amorphous spherical silica particles usually used in chromatography as stationary phases to produce MTS with the same morphology, using alkaline solution to dissolve progressively and locally silica and reprecipitate it around surfactant micelles into ordered MTS structures. Spherical beads of MTS with hexagonal and cubic symmetries have been synthesized and successfully used in HPLC in fast separation processes. MTS with a highly connected structure (cubic symmetry), uniform pores with a diameter larger than 6 nm in the form of particles of 5 ,m could compete with monolithic silica columns. Monolithic columns are receiving strong interest and represent a milestone in the area of fast separation. Their synthesis is a sol-gel process based on phase separation between silica and water, which is assisted by the presence of polymers. The control of the synthesis of monolithic silica has been systematically explored. Because of unresolved yet cladding problems to evaluate the resulting macromonoliths in HPLC, micromonoliths were synthesized into fused-silica capillaries and evaluated by nano-LC and CEC. Only CEC allows to gain high column efficiencies in fast separation processes. Capillary silica monolithic columns represent attractive alternatives for miniaturization processes (lab-on-a chip) using CEC. [source] Simple 2D-HPLC using a monolithic silica column for peptide separationJOURNAL OF SEPARATION SCIENCE, JSS, Issue 10-11 2004Hiroshi Kimura Abstract Separation of peptides by fast and simple two-dimensional (2D)-HPLC was studied using a monolithic silica column as a second-dimension (2nd-D) column. Every fraction from the first column, 5 cm long (2.1 mm ID) packed with polymer-based cation exchange beads, was subjected to separation in the 2nd-D using an octadecylsilylated (C18) monolithic silica column (4.6 mm ID, 2.5 cm). A capillary-type monolithic silica C18 column (0.1 mm ID, 10 cm) was also employed as a 2nd-D column with split flow/injection. Effluent of the first dimension (1st-D) was directly loaded into an injector loop of 2nd-D HPLC. UV and MS detection were successfully carried out at high linear velocity of mobile phase at 2nd-D using flow splitting for the 4.6 mm ID 2nd-D column, or with direct connection of the capillary column to the MS interface. Two-minute fractionation in the 1st-D, 118-second loading, and 2-second injection by the 2nd-D injector, allowed one minute for gradient separation in the 2nd-D, resulting in a maximum peak capacity of about 700 within 40 min. The use of a capillary column in the 2nd-D led to less solvent consumption and better MS detectability compared to a larger-sized column. This kind of fast and simple 2D-HPLC utilizing monolithic silica columns will be useful for the separation of complex mixtures in a short time. [source] Reduced-bore monolithic silica column modified with C8 -TEOS for reversed-phase electrochromatographyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 9 2004Qishu Qu Abstract Monolithic silica columns of 2.7 mm ID were prepared and derivatized with C8 -TEOS and TEOS by on-column sol-gel reaction. These C8 large diameter monolithic silica columns gave 21 000 theoretical plates for aromatic hydrocarbons in 60% acetonitrile and 40% Tris-HCl buffer. The surface areas as well as the separation reproducibility were improved on coating by the sol-gel approach. Joule heating was greatly reduced by using monolithic columns to which fine quartz sand had been added during column preparation. Since this is a preliminary investigation on a monolithic column with such a large inner diameter, the separation efficiency was not so high as that presently achieved in normal capillary electrochromatography (CEC). However, use of the columns improved sample loadability and concentration detectability of electrochromatography, and semi-preparative separations could be performed. [source] Determination of conjugated dienes in petroleum products by supercritical fluid chromatography and ultraviolet detectionJOURNAL OF SEPARATION SCIENCE, JSS, Issue 15-16 2003Flávio Cortiñas Albuquerque Abstract A method for determining total conjugated dienes in petroleum products, such as catalytic or thermal cracking fractions, using supercritical fluid chromatography (SFC) is presented. The separation is carried out in one or two silica columns and with CO2 as mobile phase. The conditions of analysis are the same as used in group-type analysis of diesel fuels by SFC (ASTM D 5186 standard method), except that UV detection at 240 nm is used. Hydrocarbons with two conjugated double bonds are the only substances eluting in the retention time range of the non-aromatics that appreciably absorb UV radiation at this wavelength. This was confirmed by analyzing standards of olefins, isolated diolefins, and conjugated diolefins. Results are reported in mol L,1 of 1,3-pentadiene. Several samples of different natures, such as fluid catalytic cracking liquid products and hydrotreated cracking naphthas, were successfully analyzed. The results correlate quite well with the respective diene values as determined by UOP method 326, although the slope and intercept were specific for each type of product. [source] | |||||||||||||