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Chromatographic Column (chromatographic + column)
Selected AbstractsMechanical Deformation of Compressible Chromatographic ColumnsBIOTECHNOLOGY PROGRESS, Issue 3 2002R. N. Keener A one-dimensional model of mechanical deformation of compressible chromatography columns is presented. The model is based on linear elasticity and continuum mechanics and is compared to a more complete two-dimensional model and one-dimensional porosity profiles measured by NMR imaging methods. The model provides a quantitative description of compression and the effects of wall support during scale-up. A simple criterion for the significance of wall support as a function of both diameter and length is also developed. Although the model accounts only for mechanical deformation, flow compression can be included, and validation presented here suggests that a more complete model may be valuable for anticipating the effects of scale and aspect ratio on pressure-flow behavior of compressible columns. [source] A rapid and sensitive liquid chromatography/positive ion tandem mass spectrometry method for the determination of cimetropium in human plasma by liquid,liquid extractionJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 7 2006Heon-Woo Lee Abstract We have developed and validated a simple detection system with high-performance liquid chromatography (HPLC) with positive ion electrospray ionization tandem mass spectrometry (ESI-MS/MS) for determining cimetropium levels in human plasma using scopolamine butyl bromide as an internal standard (I.S.). The acquisition was performed in the multiple reaction monitoring (MRM) mode, by monitoring the transitions: m/z 357.9 > 103.1 for cimetropium and m/z 359.9 > 103.1 for butyl-scopolamine. The method involves a simple single-step liquid,liquid extraction with dichloromethane. The analyte was chromatographed on an YMC C18 reversed-phase chromatographic column by isocratic elution with 10 mM ammonium formate buffer,methanol (19 : 81, v/v; adjusted to pH 4.0 with formic acid). The results were linear over the studied range (0.2,100 ng ml,1), with r2 = 1.0000, and the total analysis time for each run was 2 min. Intra- and interassay precisions were 0.70,8.54% and 1.08,4.85%, respectively, and intra- and interassay accuracies were 97.56,108.23% and 97.48,103.91%, respectively. The lower limit of quantification (LLOQ) was 0.2 ng ml,1. At this concentration, mean intra- and interassay precisions were 8.54% and 4.85%, respectively, and mean intra- and interassay accuracies were 97.56% and 98.91%, respectively. The mean recovery ranged from 62.71 ± 4.06 to 64.23 ± 2.32%. Cimetropium was found to be stable in plasma samples under typical storage and processing conditions. The devised assay was successfully applied to a pharmacokinetic study of cimetropium bromide administered as a single oral dose (150 mg) to healthy volunteers. Copyright © 2006 John Wiley & Sons, Ltd. [source] Purification of alkaloids from Corydalis yanhusuo W. T. Wang using preparative 2-D HPLCJOURNAL OF SEPARATION SCIENCE, JSS, Issue 9 2009Jing Zhang Abstract Two-dimensional preparative multi-channel parallel high performance liquid chromatography was successfully applied for the first time to isolate and purify alkaloids from Corydalis yanhusuo. The experiments were performed in off-line mode using the same preparative chromatographic column with pH 3.5 in the first and pH 10.0 in the second separation dimension. In the preparative process, UV-triggered fraction collection was used in the first dimension while UV and MS-triggered collection were used in the second dimension for reasons of sensitivity and complementarity. Two pure compounds and nine fractions were obtained in the first dimension. Then two representative fractions were further purified in the second dimension and six pure compounds were obtained. The results demonstrated that this procedure is an effective approach for the preparative isolation and purification of alkaloids from Corydalis yanhusuo. Based on the different pH values of the mobile phase in this method, it is also suitable for the preparative isolation and purification of other compounds from TCMs which are sensitive to the pH of the solutions. Moreover, this method will be a promising tool for the purification of low content compounds from natural products. [source] Development of a silica monolith microbioreactor entrapping highly activated lipase and an experiment toward integration with chromatographic separation of chiral estersJOURNAL OF SEPARATION SCIENCE, JSS, Issue 17 2007Koei Kawakami Abstract Microbioreactors are effective for high-throughput production of expensive products from small amounts of substrates. Lipases are versatile enzymes for chiral syntheses, and are highly activated when immobilized in alkyl-substituted silicates by the sol,gel method. For practical application of sol,gel immobilized lipases to a flow system, a microbioreactor loaded with a macroporous silica monolith is well suited, because it can be easily integrated with a chromatographic separator for optical resolution. We attempted to develop a microbioreactor containing a silica monolith-immobilized lipase. A nonshrinkable silica monolith was first formed from a 4:1 mixture of methyltrimethoxysilane (MTMS) and tetramethoxysilane (TMOS). It was then coated with silica precipitates entrapping lipase, derived from a 4:1 mixture of n -butyltrimethoxysilane (BTMS) and TMOS. As a result, monolith treated with the BTMS-based silicate entrapping lipase exhibited approximately ten times higher activity than nontreated monolith-immobilized lipase derived from the MTMS-based silicate, in transesterification between glycidol and vinyl n -butyrate in isooctane. A commercially available chiral column was connected in series to the monolith microbioreactor, and a pulse of substrate solution was supplied at the inlet of the reactor. Successful resolution of the racemic ester produced was achieved in the chromatographic column. [source] Behaviour of carbamate pesticides in gas chromatography and their determination with solid-phase extraction and solid-phase microextraction as preconcentration stepsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 16 2005Rita Carabias-Martínez Abstract This work reports a study of the chromatographic behaviour of seven carbamate pesticides (aldicarb, carbetamide, propoxur, carbofuran, carbaryl, methiocarb, and pirimicarb) by gas chromatography-mass spectrometry (GC-MS). Variables such as injector temperature, solvent, injection mode, and the degree of ageing of the chromatographic column were studied. One of the aims of this work was to achieve a controlled decomposition of carbamates by a solid-phase microextraction (SPME) preconcentration step with a polyacrylate fibre in order to obtain reproducible chromatographic signals of the degradation products. Optimisation of the SPME process was accomplished by means of experimental design. Several methods using ultrapure water were developed with different preconcentration configurations: SPME-GC-MS, SPE followed by SPME-GC-MS, and SPE plus GC-MS. For all the pesticides studied, method detection limit (MDL) values below 0.1 ,g L,1 were reached in at least one of the proposed configurations. [source] Pastoral and species flavour in lambs raised on pasture, lucerne or maizeJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 2 2003Owen A Young Abstract Variations in diet, age and castration were employed to generate a range of flavours that were chemically analysed to find the cause of ,pastoral' flavour in sheepmeat and its relationship to species flavour. Lambs were raised on pasture (ram or castrate) or on a maize-based or lucerne-based concentrate diet (ram only). They were slaughtered at 132 and 232 days. Fat from animals raised on concentrates had lower proportions of fat-hardening stearic acid and higher proportions of oxidation-prone fat-softening oleic and linoleic acids. Concentrations of species-characterising short branched-chain fatty acids (BCFAs), typified by 4-methyloctanoic acid, were lower for pasture-fed lambs, particularly at 232 days, although between-animal variation was high. Castration did not statistically affect BCFA concentration at this age. Correlations between BCFAs and testes weight were not significant, suggesting that they were not acting as sex pheromones. Concentrations of 3-methylindole (skatole) in perirenal fat were higher for the pasture diet at both slaughter dates. Concentrations of 4-methylphenol in the fat were not affected by diet. However, 3-methylphenol was more abundant in pasture treatments. A sensory panel found that the intensity of ,sheepmeat' flavour was higher for pasture-raised animals, but that associations of ,barnyard' flavour (which has been linked to pastoral flavour) with diet were more complex. The issue was resolved by fat sniffing. Panel responses to heated subcutaneous fat were recorded as frequency of descriptive terms drawn from a limited lexicon. Volatiles from fats pooled by treatment were resolved on a gas chromatographic column whose effluent was monitored by odourport sniffing. Compounds were identified by parallel chromatographic/mass spectrometric runs. The headspace concentrations of these compounds were then measured for individual animals. These data were related to frequency data by the principal component method. ,Mutton' and ,sheepmeat' odour notes were clearly linked to indoles (skatole particularly) and, to a lesser extent, methylphenol, setting these notes apart from ,lamb', an odour note more associated with lucerne and maize diets through higher concentrations of BCFAs. It was concluded that 3-methylindole was the major cause of pastoral flavour in sheepmeat, and that fat oxidation products represented a background flavour that varied quantitatively but not qualitatively with fatty acid profile. © 2002 Society of Chemical Industry [source] A rapid ultra-performance liquid chromatography,electrospray Ionisation mass spectrometric method for the analysis of saponins in the adventitious roots of Panax notoginsengPHYTOCHEMICAL ANALYSIS, Issue 1 2009Mo Dan Abstract Introduction Saponins are bioactive compounds employed in the prevention and treatment of cardiovascular and cerebrovascular diseases. The adventitious roots of Panax notoginseng may offer an alternative source of saponins. Identification and determination of saponins in the crude extract is challenging owing to their similar structures and the lack of standards. Objective To develop a rapid, sensitive and accurate method based on solid-phase extraction followed by ultra-performance liquid chromatography,electrospray ionisation mass spectrometry (UPLC-ESI-MS) for the identification and quantification of saponins in P. notoginseng. Methodology Following extraction using Waters OasisTM HLB cartridges, the analytes were subjected to a UPLC system with a Waters Acquity BEH C18 chromatographic column and a binary mobile phase system consisting of 0.05% formic acid in water and acetonitrile under gradient elution conditions, with final detection by ESI-MS in the positive ion mode. Results The UPLC-ESI-MS method gave limits of detection and quantification within the range 0.015,0.382 and 0.052,1.124 µg/mL, respectively, for 15 studied saponins. The instrumentation/injection precision (RSD) was 4.5% for a low concentration and 3.2% for an intermediate concentration sample. The intra- and inter-day repeatability was less than 2.65% (RSD). The method described was validated using spiked samples with different amounts of saponin standards. Conclusion This UPLC-ESI-MS assay provides a suitable quality control method for the tentative identification and determination of major biological active constituents in adventitious and native roots of P. notoginseng. Copyright © 2008 John Wiley & Sons, Ltd. [source] Semi-online nanoflow liquid chromatography/matrix-assisted laser desorption ionization mass spectrometry of synthetic polymers using an octadecylsilyl-modified monolithic silica capillary columnRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 13 2010Takehiro Watanabe We have designed a semi-online liquid chromatography/matrix-assisted laser desorption/ionization mass spectrometry (LC/MALDI-MS) system to introduce eluent from a octadecylsilyl (ODS) group modified monolithic silica capillary chromatographic column directly onto a sample plate for MALDI-MS analysis. Our novel semi-online system is useful for rapidly and sensitively examining the performance of a monolithic capillary column. An additional advantage is the small elution volume of a monolithic capillary column, which allows delicate eluents, such as 1,1,1,3,3,3,-hexafluoroisopropyl alcohol (HFIP), to be used to achieve cost-effective analysis. Using the semi-online LC/MALDI-MS system, chromatographic separation of polymers by the monolithic column with different eluents was studied. Separation of poly(methyl methacrylate) and Nylon 6/6 showed that the column functioned via size-exclusion separation when tetrahydrofuran or HFIP eluent was used. On the other hand, the separation behavior of Nylon 11 indicated a reversed-phase mode owing to the interaction of the polymer with the modified ODS group in the column. Using tetrahydrofuran/methanol (1:1, v/v) as the eluent, the LC/MALDI-MS spectra of poly(lactic acid), which contains both linear and cyclic polymer structures, showed that the column could separate the hydrophobic cyclic polymer and elute it out relatively slowly. The monolithic column functions basically via size-exclusion separation; the reversed-phase separation by interaction with the ODS functions may have less influence on column separation. The semi-online monolithic capillary LC/MALDI-MS method we have developed should provide a means of effectively analyzing synthetic polymers. Copyright © 2010 John Wiley & Sons, Ltd. [source] Purification, crystallization and preliminary X-ray diffraction studies on avian haemoglobin from pigeon (Columba livia)ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 2 2009Pon. Sathya Moorthy Haemoglobin is a physiologically significant metalloprotein that is involved in the exchange of gases for sustaining life. The respiratory system of birds is unique and complex compared with that of mammals. Many investigations of avian haemoglobins have revealed the presence of inositol pentaphosphate (IP5), a principal allosteric effector that is involved in regulation of their function. Structural investigations of avian haemoglobins are presently not adequate to explain their function. Efforts have been made in this direction in order to understand the oxygen-binding affinity involved in adapting to hypoxia in avian haemoglobins. Fresh whole blood was collected from pigeon (Columba livia) and purified using a DEAE cellulose anion-exchange chromatographic column. Crystallization of pigeon haemoglobin was accomplished using the hanging-drop vapour-diffusion method using PEG 3350 as a precipitant in 50,mM sodium acetate buffer pH 5.5 with 1,M NaCl. Data collection was carried out using a MAR345 image-plate detector system. The crystals diffracted to 2,Ĺ resolution. Pigeon haemoglobin crystallizes in a triclinic space group, with two whole biological molecules in the asymmetric unit and with unit-cell parameters a = 55.005, b = 65.528, c = 104.370,Ĺ, , = 78.742, , = 89.819, , = 65.320°. [source] Mechanics of column beds: I. Acquisition of the relevant parametersAICHE JOURNAL, Issue 3 2003Bee Gaik Yew The efficiency of chromatographic columns is adversely affected by large-scale radial variations of the packing density or void ratio of the material used to prepare the bed. This heterogeneity is due to wall friction effects that take place during the preparation of the column and to seepage effects operating during the packing process and the subsequent operation of the column. The dependence of the bed's void fraction on the stress applied during its consolidation was determined, as well as its permeability at various stages of the consolidation process and the coefficient of friction between typical packing materials and the stainless steel wall of chromatographic columns. These results are required to develop and use numerical models of the volumetric response to axial compression of the bed and models of the coupled mechanical-seepage rheology of particulate materials. [source] Mechanics of column beds: II.AICHE JOURNAL, Issue 3 2003Modeling of coupled stress-strain-flow behavior The rheological behavior of a bed of packing material during its consolidation was investigated using an elastic-plastic model, the Frictional Material Model. This model takes into account the behavior of the packing material under compression stress, its consolidation, its internal friction, its friction against the column wall, and the dependence of the bed's permeability on the local void fraction. The complexity of the problem arises from the nonlinear behavior of the relationships between the critical parameters controlling the column bed behavior and the external stresses applied to this bed. Solutions of the model were calculated for combinations of axial compression and seepage stresses, the latter corresponding to the flow of the mobile-phase stream under typical conditions used in HPLC. The results demonstrate the importance of the internal angle of friction of the packing material used on the degree of radial and axial heterogeneity of the beds of chromatographic columns packed with this material. [source] Study on conical columns for semi-preparative liquid chromatographyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 3-4 2003Ma Jiping Abstract The dynamic flow profiles and column efficiencies in conically shaped semi-preparative liquid chromatographic columns (inlet ID larger than outlet ID) with two different conical angles (7° and 15°) were studied. The dynamic flow profiles were studied by an on-column visualization method. Conical columns were compared with cylindrical column of the same length and internal volume. The results showed that the flow profile of a sample band in the conical column of 7° (50 mm×17 mm , 11 mm ID) was parabolic in shape. The sample band migrated slower in the wall region than in the central region, as in the cylindrical column (50 mm×14 mm ID). However, the sample band in the conical column of 15° (50 mm×20 mm , 7 mm ID) migrated slower in the central region than in the wall region, resulting in a reverse parabolic flow profile, in contrast to that in cylindrical column. This indicated that a flat flow profile might be realized in a conical column with a conical angle between 7° and 15°. The conical column of 15° had the highest column efficiency among the three columns under the same conditions. Compared with the cylindrical column packed with identical packing material, the conical column of 15° had 22%,45% higher column efficiency and 11%,27% higher peak height. [source] A novel purification strategy for retrovirus gene therapy vectors using heparin affinity chromatographyBIOTECHNOLOGY & BIOENGINEERING, Issue 4 2005María de las Mercedes Segura Abstract Membrane separation and chromatographic technologies are regarded as an attractive alternative to conventional academic small-scale ultracentrifugation procedures used for retrovirus purification. However, despite the increasing demands for purified retroviral vector preparations, new chromatography adsorbents with high specificity for the virus have not been reported. Heparin affinity chromatography is presented here as a novel convenient tool for retrovirus purification. The ability of bioactive retroviral particles to specifically bind to heparin ligands immobilized on a chromatographic gel is shown. A purification factor of 63 with a recovery of 61% of functional retroparticles was achieved using this single step. Tentacle heparin affinity supports captured retroviral particles more efficiently than conventional heparin affinity chromatography supports with which a lower recovery was obtained (18%). Intact, infective retroviral particles were recovered by elution with low salt concentrations (350 mM NaCl). Mild conditions for retrovirus elution from chromatographic columns are required to preserve virus infectivity. VSV-G pseudotyped retroviruses have shown to be very sensitive to high ionic strength, losing 50% of their activity and showing membrane damage after a short exposure to 1M NaCl. We also report a complete scaleable downstream processing scheme for the purification of MoMLV-derived vectors that involves sequential microfiltration and ultra/diafiltration steps for virus clarification and concentration respectively, followed by fractionation by heparin affinity chromatography and final polishing by size-exclusion chromatography. Overall, by using this strategy, a 38% yield of infective particles can be achieved with a final purification factor of 2,000. © 2005 Wiley Periodicals, Inc. [source] Design of Simulated Moving Bed Plants for Reduced PuritiesCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 1 2010M. Fütterer Abstract Simulated moving bed (SMB) chromatography is an established separation technology, where chromatographic columns are interconnected to a ring. The feeding and drains are switched over cyclically, such that a continuous separation becomes possible. For a faultless operation, the volumetric flow rates and switching time must be carefully adjusted. Therefore, it is desirable to calculate these values in dependence of the model parameters exactly. In this contribution, a new method is introduced to compute operating points for dispersion-free SMB plants and to predict the associated time trajectories of the concentrations at the drains in cyclic steady state for user-specified purities and degree of robustness. Simulation results are presented to show the potential of this new method. [source] High Throughput Screening for the Design and Optimization of Chromatographic Processes: Assessment of Model Parameter Determination from High Throughput Compatible DataCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 12 2008A. Susanto Abstract Chromatographic processes can be optimized in various ways, and the two most prominent approaches are based either on statistical data analysis or on experimentally validated simulation models. Both strategies rely heavily on experimental data, the generation of which usually imposes a significant bottleneck on rational process design. The latter approach is followed in this work, and the utilizability of high throughput compatible experiments for the determination of model parameters which are required for in silico process optimization, is assessed. The unknown parameter values are estimated from batch uptake experiments on a robotic platform and from dynamic breakthrough experiments with miniaturized chromatographic columns. The identified model is then validated with respect to process optimization by comparison of model predictions with experimental data from a preparative scale column. In this study, a strong cation exchanger Toyopearl SP-650M and lysozyme solved in phosphate buffer (pH 7), is used as the test system. The utilization of data from miniaturized and high throughput compatible experiments is shown to yield sufficiently accurate results, and minimizes efforts and costs for both parameter estimation and model validation. [source] | |||||||||||||