The Experts below are selected from a list of 29277 Experts worldwide ranked by ideXlab platform
Georges Guiochon - One of the best experts on this subject based on the ideXlab platform.
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possible resolution gain in enantioseparations afforded by core shell particle technology
Journal of Chromatography A, 2014Co-Authors: Fabrice Gritti, Georges GuiochonAbstract:Whether columns packed with core–shell particles may outperform those packed with fully porous particles for chiral separations is controversial. The potential advantages of such columns are investigated from a Theoretical viewpoint. The height equivalent to a Theoretical Plate (HETP) associated to the slow adsorption-desorption process typical of chiral chromatography was derived from the Laplace transform of the general rate model of chromatography for core–shell particles. The relationship between the resolution factor and the core-to-particle diameter ratio is predicted at constant selectivity. The calculations are based on a complete set of actual kinetic parameters (longitudinal diffusion, eddy dispersion, intra-particle diffusivity, and adsorption-desorption constant) measured for a reference column packed with Lux Cellulose-1 fully porous particles. If we compare columns packed with the best procedure available in either case, the results demonstrate that those packed with core–shell particles may outperform to a degree those packed with fully porous particles. The minimum reduced HETP could decrease from 2.0 to 1.7. The maximum relative gain in resolution is about 10%, which is not negligible for critical enantioselective-separations. This gain is observed only if the packing uniformity of the core–shell particles is achieved.
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rapid development of core shell column technology accurate measurements of the intrinsic column efficiency of narrow bore columns packed with 4 6 down to 1 3 μm superficially porous particles
Journal of Chromatography A, 2014Co-Authors: Fabrice Gritti, Georges GuiochonAbstract:Abstract The intrinsic heights equivalent to a Theoretical Plate (HETPs) of 31 narrow-bore and wide-bore columns packed with four different brands of core–shell particles were accurately measured on an optimized vHPLC instrument (1290 Infinity system) that has an extra-column volume variance of 13.6 ± 0.3 μL 2 . These results were derived from the slopes of the linear plots of the apparent Plate heights of each column versus the reciprocal of (1 + k′ ) 2 for seven homologous compounds with a linear regression coefficient larger than 0.999. The results show that the kinetic performance of narrow-bore columns packed with core–shell particles increases almost linearly with decreasing particle diameter. The optimum reduced Plate heights increase slightly from 1.6 to 1.9 with decreasing particle sizes from 4.6 to 1.3 μm. This confirms that wide-bore columns provide better efficiencies than narrow-bore columns.
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effect of parallel segmented flow chromatography on the height equivalent to a Theoretical Plate ii performances of 4 6mm 30mm columns packed with 2 6μm accucore c18 superficially porous particles
Journal of Chromatography A, 2013Co-Authors: Fabrice Gritti, Georges GuiochonAbstract:Abstract The reduced trans-column (or long-range eddy dispersion) height equivalent to a Theoretical Plate (HETP) of short and wide 4.6 mm × 30 mm columns packed with 2.6 μm Accucore-C 18 superficially porous particles was measured under conventional (no split flow) and parallel segmented (outlet and inlet) flow chromatography. The overall reduced HETP was derived from the true moments of the recorded concentration profiles. The longitudinal diffusion HETP term was measured at a very small flow rate (0.05 mL/min). The solid–liquid mass transfer resistance was derived from the shell diffusivity, using the composite Garnett–Torquato model of effective diffusion in a heterogeneous system made of a dense packing of core–shell particles immersed in a continuous matrix (the eluent). The trans-channel and short-range interchannel eddy dispersion HETP terms were assumed to be equal to the calculated h data after solving the Navier–Stokes equation and simulating the advection–diffusion transport process. Experimental results confirmed that the optimum efficiency of these short columns was increased by a factor of about two. The ratio of the detection sensitivities on the PSFC stream and on a regular stream increased from 1 to 1.45 when the retention factor decreases from about 10 to 0.5. These phenomena are due to a strong reduction of the trans-column eddy dispersion HETP term. The system loses about 60% of the sample mass when only outlet skimming is carried out when the flow rate ratio of 55% is applied, as was done in this work. It loses about 50% of the sample when inlet/outlet segmentation is applied. In gradient elution, the peak capacity is increased by only 15%, due to post-column band spreading, which should imperatively be minimized when the outlet flow is split.
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effect of parallel segmented flow chromatography on the height equivalent to a Theoretical Plate i performance of 4 6 mm 30 mm columns packed with 3 0 μm hypurity c18 fully porous particles
Journal of Chromatography A, 2013Co-Authors: Fabrice Gritti, Georges GuiochonAbstract:Abstract The mass transfer kinetics in short and wide 4.6 mm × 30 mm columns packed with 3.0 μm Hypurity-C18 fully porous particles were measured for three different configurations of the inlet sample distribution and outlet sample collection: (1) both the inlet and outlet column endfittings are standard, (2) the inlet endfitting is standard while the outlet endfitting allows parallel segmentation of the exiting flow between a central and a peripheral region across the column diameter, and (3) both the inlet and outlet endfittings allow a parallel segmentation of the flow entering and exiting the column, respectively. The total reduced heights equivalent to a Theoretical Plate (HETP) were carefully measured, using the first and second central moments of the elution band profiles, obtained by its accurate numerical integration. The longitudinal diffusion term was measured at the lowest experimental reduced velocity applied. The solid–liquid mass transfer resistance was estimated from measurements of the intra-particle diffusivity using the Torquato's model of effective diffusion in packed beds. The trans-channel and short-range interchannel eddy diffusion HETP terms were taken from data obtained by solving numerically the Navier–Stokes equations and simulating advective-diffusive transport in computer-generated random sphere packings. The results clearly show that the trans-column eddy diffusion HETP term can account for up to 85% of the total intrinsic HETP (corrected for extra-column contributions) of the standard columns. Parallel segmented flow chromatography can reduce this contribution by half at high velocities, by eliminating most of the baseline peak tailing. This holds true irrespective of the retention factor of the analyte. It was found also that segmenting the inlet/outlet flow increases detection sensitivity by 25–50% for peaks with large to small retention factors, respectively. In practice, the advantage of parallel segmented flow chromatography in gradient elution (thin peak widths) is essentially limited by post-column bandspreading and diffusion in the dwell volume of the instrument used. Analyst should minimize post-column bandspreading (caused by connectors and detection cell volume) and synchronize the eluent composition in the peripheral and central inlet ports of the column, by using two separate pumps with appropriate dwell volumes.
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relationship between trans column eddy diffusion and retention in liquid chromatography theory and experimental evidence
Journal of Chromatography A, 2010Co-Authors: Fabrice Gritti, Georges GuiochonAbstract:Abstract Experimental results demonstrate that trans-column eddy diffusion depends on the retention of compounds. The combination of elution profiles recorded in different points of the exit column cross-section and of the height equivalent to a Theoretical Plate (HETP) of small molecules clearly show a strong link between retention and column performance in liquid chromatography. These results validate a new model of trans-column eddy diffusion in packed columns. The contribution to the column HETP of the trans-column eddy diffusion term decreases with increasing retention factor from k′ = 0 to k′ = 3 above which it becomes negligible. The best column performance in RPLC is observed for the most retained compounds. This is due to the combination of the lack of a residual trans-column eddy diffusion contribution and the vanishing contribution of the instrument to band broadening.
Hamed Abbasfard - One of the best experts on this subject based on the ideXlab platform.
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simulation and feasibility analysis of structured packing replacement in absorption column of natural gas dehydration process a case study for farashband gas processing plant iran
Journal of Natural Gas Science and Engineering, 2014Co-Authors: Seyyed Mohammad Jokar, Hamid Reza Rahimpour, Hossein Momeni, Mohammad Reza Rahimpour, Hamed AbbasfardAbstract:Abstract Application of structured packing in separation processes like natural gas dehydration has been increased since last few years. Replacement of the existing trayed column with that of structured packing can enhance the capacity and performance of the natural gas dehydration process. In this work, the natural gas dehydration plant of Farashband gas processing plant has been simulated. The profile of concentration, temperature and pressure in absorption column was obtained. A computer program, prepared with Visual Basic, has been proposed to calculate the height equivalent to a Theoretical Plate (HETP) of structured packing. The effect of some important parameters of inlet Tri-ethylene glycol (TEG) and natural gas on the performance of absorption column have been analyzed. Results show that revamp of trays with structured packing, can reduce outlet natural gas dew point and improve the positive effect of other parameters on the performance of dehydration unit. Moreover, the most significant factors affecting the HETP were investigated which were less than 15% effective. Finally, the cost of the modification project for the absorption column in the Farashband gas processing plant was calculated. The cost is evaluated 202,909 $ in this case and replacing was found economically justifiable.
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simulation and feasibility analysis of structured packing replacement in absorption column of natural gas dehydration process a case study for farashband gas processing plant iran
Journal of Natural Gas Science and Engineering, 2014Co-Authors: Seyyed Mohammad Jokar, Hamid Reza Rahimpour, Hossein Momeni, Mohammad Reza Rahimpour, Hamed AbbasfardAbstract:Abstract Application of structured packing in separation processes like natural gas dehydration has been increased since last few years. Replacement of the existing trayed column with that of structured packing can enhance the capacity and performance of the natural gas dehydration process. In this work, the natural gas dehydration plant of Farashband gas processing plant has been simulated. The profile of concentration, temperature and pressure in absorption column was obtained. A computer program, prepared with Visual Basic, has been proposed to calculate the height equivalent to a Theoretical Plate (HETP) of structured packing. The effect of some important parameters of inlet Tri-ethylene glycol (TEG) and natural gas on the performance of absorption column have been analyzed. Results show that revamp of trays with structured packing, can reduce outlet natural gas dew point and improve the positive effect of other parameters on the performance of dehydration unit. Moreover, the most significant factors affecting the HETP were investigated which were less than 15% effective. Finally, the cost of the modification project for the absorption column in the Farashband gas processing plant was calculated. The cost is evaluated 202,909 $ in this case and replacing was found economically justifiable.
Fabrice Gritti - One of the best experts on this subject based on the ideXlab platform.
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possible resolution gain in enantioseparations afforded by core shell particle technology
Journal of Chromatography A, 2014Co-Authors: Fabrice Gritti, Georges GuiochonAbstract:Whether columns packed with core–shell particles may outperform those packed with fully porous particles for chiral separations is controversial. The potential advantages of such columns are investigated from a Theoretical viewpoint. The height equivalent to a Theoretical Plate (HETP) associated to the slow adsorption-desorption process typical of chiral chromatography was derived from the Laplace transform of the general rate model of chromatography for core–shell particles. The relationship between the resolution factor and the core-to-particle diameter ratio is predicted at constant selectivity. The calculations are based on a complete set of actual kinetic parameters (longitudinal diffusion, eddy dispersion, intra-particle diffusivity, and adsorption-desorption constant) measured for a reference column packed with Lux Cellulose-1 fully porous particles. If we compare columns packed with the best procedure available in either case, the results demonstrate that those packed with core–shell particles may outperform to a degree those packed with fully porous particles. The minimum reduced HETP could decrease from 2.0 to 1.7. The maximum relative gain in resolution is about 10%, which is not negligible for critical enantioselective-separations. This gain is observed only if the packing uniformity of the core–shell particles is achieved.
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rapid development of core shell column technology accurate measurements of the intrinsic column efficiency of narrow bore columns packed with 4 6 down to 1 3 μm superficially porous particles
Journal of Chromatography A, 2014Co-Authors: Fabrice Gritti, Georges GuiochonAbstract:Abstract The intrinsic heights equivalent to a Theoretical Plate (HETPs) of 31 narrow-bore and wide-bore columns packed with four different brands of core–shell particles were accurately measured on an optimized vHPLC instrument (1290 Infinity system) that has an extra-column volume variance of 13.6 ± 0.3 μL 2 . These results were derived from the slopes of the linear plots of the apparent Plate heights of each column versus the reciprocal of (1 + k′ ) 2 for seven homologous compounds with a linear regression coefficient larger than 0.999. The results show that the kinetic performance of narrow-bore columns packed with core–shell particles increases almost linearly with decreasing particle diameter. The optimum reduced Plate heights increase slightly from 1.6 to 1.9 with decreasing particle sizes from 4.6 to 1.3 μm. This confirms that wide-bore columns provide better efficiencies than narrow-bore columns.
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effect of parallel segmented flow chromatography on the height equivalent to a Theoretical Plate ii performances of 4 6mm 30mm columns packed with 2 6μm accucore c18 superficially porous particles
Journal of Chromatography A, 2013Co-Authors: Fabrice Gritti, Georges GuiochonAbstract:Abstract The reduced trans-column (or long-range eddy dispersion) height equivalent to a Theoretical Plate (HETP) of short and wide 4.6 mm × 30 mm columns packed with 2.6 μm Accucore-C 18 superficially porous particles was measured under conventional (no split flow) and parallel segmented (outlet and inlet) flow chromatography. The overall reduced HETP was derived from the true moments of the recorded concentration profiles. The longitudinal diffusion HETP term was measured at a very small flow rate (0.05 mL/min). The solid–liquid mass transfer resistance was derived from the shell diffusivity, using the composite Garnett–Torquato model of effective diffusion in a heterogeneous system made of a dense packing of core–shell particles immersed in a continuous matrix (the eluent). The trans-channel and short-range interchannel eddy dispersion HETP terms were assumed to be equal to the calculated h data after solving the Navier–Stokes equation and simulating the advection–diffusion transport process. Experimental results confirmed that the optimum efficiency of these short columns was increased by a factor of about two. The ratio of the detection sensitivities on the PSFC stream and on a regular stream increased from 1 to 1.45 when the retention factor decreases from about 10 to 0.5. These phenomena are due to a strong reduction of the trans-column eddy dispersion HETP term. The system loses about 60% of the sample mass when only outlet skimming is carried out when the flow rate ratio of 55% is applied, as was done in this work. It loses about 50% of the sample when inlet/outlet segmentation is applied. In gradient elution, the peak capacity is increased by only 15%, due to post-column band spreading, which should imperatively be minimized when the outlet flow is split.
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effect of parallel segmented flow chromatography on the height equivalent to a Theoretical Plate i performance of 4 6 mm 30 mm columns packed with 3 0 μm hypurity c18 fully porous particles
Journal of Chromatography A, 2013Co-Authors: Fabrice Gritti, Georges GuiochonAbstract:Abstract The mass transfer kinetics in short and wide 4.6 mm × 30 mm columns packed with 3.0 μm Hypurity-C18 fully porous particles were measured for three different configurations of the inlet sample distribution and outlet sample collection: (1) both the inlet and outlet column endfittings are standard, (2) the inlet endfitting is standard while the outlet endfitting allows parallel segmentation of the exiting flow between a central and a peripheral region across the column diameter, and (3) both the inlet and outlet endfittings allow a parallel segmentation of the flow entering and exiting the column, respectively. The total reduced heights equivalent to a Theoretical Plate (HETP) were carefully measured, using the first and second central moments of the elution band profiles, obtained by its accurate numerical integration. The longitudinal diffusion term was measured at the lowest experimental reduced velocity applied. The solid–liquid mass transfer resistance was estimated from measurements of the intra-particle diffusivity using the Torquato's model of effective diffusion in packed beds. The trans-channel and short-range interchannel eddy diffusion HETP terms were taken from data obtained by solving numerically the Navier–Stokes equations and simulating advective-diffusive transport in computer-generated random sphere packings. The results clearly show that the trans-column eddy diffusion HETP term can account for up to 85% of the total intrinsic HETP (corrected for extra-column contributions) of the standard columns. Parallel segmented flow chromatography can reduce this contribution by half at high velocities, by eliminating most of the baseline peak tailing. This holds true irrespective of the retention factor of the analyte. It was found also that segmenting the inlet/outlet flow increases detection sensitivity by 25–50% for peaks with large to small retention factors, respectively. In practice, the advantage of parallel segmented flow chromatography in gradient elution (thin peak widths) is essentially limited by post-column bandspreading and diffusion in the dwell volume of the instrument used. Analyst should minimize post-column bandspreading (caused by connectors and detection cell volume) and synchronize the eluent composition in the peripheral and central inlet ports of the column, by using two separate pumps with appropriate dwell volumes.
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relationship between trans column eddy diffusion and retention in liquid chromatography theory and experimental evidence
Journal of Chromatography A, 2010Co-Authors: Fabrice Gritti, Georges GuiochonAbstract:Abstract Experimental results demonstrate that trans-column eddy diffusion depends on the retention of compounds. The combination of elution profiles recorded in different points of the exit column cross-section and of the height equivalent to a Theoretical Plate (HETP) of small molecules clearly show a strong link between retention and column performance in liquid chromatography. These results validate a new model of trans-column eddy diffusion in packed columns. The contribution to the column HETP of the trans-column eddy diffusion term decreases with increasing retention factor from k′ = 0 to k′ = 3 above which it becomes negligible. The best column performance in RPLC is observed for the most retained compounds. This is due to the combination of the lack of a residual trans-column eddy diffusion contribution and the vanishing contribution of the instrument to band broadening.
Chi Ruan - One of the best experts on this subject based on the ideXlab platform.
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optimisation of mass transfer in column elution of rare earths from low grade weathered crust elution deposited rare earth ore
Hydrometallurgy, 2010Co-Authors: Yin Jingqun, Chen Kaihong, Rao Guohua, Jiang Mintao, Chi RuanAbstract:An investigation was carried out to optimize the leaching and mass transfer of rare earth metals with ammonium sulfate solution during the column elution of a low grade weathered crust elution-deposited rare earth ore. The effects of flow rate, concentration of leach reagent and ore grade on the leaching performance were examined. The experimental data was analyzed using chromatographic non-equilibrium Plate theory in order to elucidate the mass transfer phenomena. It was found that the relationship between the height equivalent to a Theoretical Plate (HETP) and the leaching flow rate can be described by the Van Deemter equation and there is an optimum flow rate in the leaching process. Compared with similar higher grade ores which have a sharp peak followed by a short tail, the leach curve of low grade ores has a long tail following a broader peak.
Seyyed Mohammad Jokar - One of the best experts on this subject based on the ideXlab platform.
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simulation and feasibility analysis of structured packing replacement in absorption column of natural gas dehydration process a case study for farashband gas processing plant iran
Journal of Natural Gas Science and Engineering, 2014Co-Authors: Seyyed Mohammad Jokar, Hamid Reza Rahimpour, Hossein Momeni, Mohammad Reza Rahimpour, Hamed AbbasfardAbstract:Abstract Application of structured packing in separation processes like natural gas dehydration has been increased since last few years. Replacement of the existing trayed column with that of structured packing can enhance the capacity and performance of the natural gas dehydration process. In this work, the natural gas dehydration plant of Farashband gas processing plant has been simulated. The profile of concentration, temperature and pressure in absorption column was obtained. A computer program, prepared with Visual Basic, has been proposed to calculate the height equivalent to a Theoretical Plate (HETP) of structured packing. The effect of some important parameters of inlet Tri-ethylene glycol (TEG) and natural gas on the performance of absorption column have been analyzed. Results show that revamp of trays with structured packing, can reduce outlet natural gas dew point and improve the positive effect of other parameters on the performance of dehydration unit. Moreover, the most significant factors affecting the HETP were investigated which were less than 15% effective. Finally, the cost of the modification project for the absorption column in the Farashband gas processing plant was calculated. The cost is evaluated 202,909 $ in this case and replacing was found economically justifiable.
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simulation and feasibility analysis of structured packing replacement in absorption column of natural gas dehydration process a case study for farashband gas processing plant iran
Journal of Natural Gas Science and Engineering, 2014Co-Authors: Seyyed Mohammad Jokar, Hamid Reza Rahimpour, Hossein Momeni, Mohammad Reza Rahimpour, Hamed AbbasfardAbstract:Abstract Application of structured packing in separation processes like natural gas dehydration has been increased since last few years. Replacement of the existing trayed column with that of structured packing can enhance the capacity and performance of the natural gas dehydration process. In this work, the natural gas dehydration plant of Farashband gas processing plant has been simulated. The profile of concentration, temperature and pressure in absorption column was obtained. A computer program, prepared with Visual Basic, has been proposed to calculate the height equivalent to a Theoretical Plate (HETP) of structured packing. The effect of some important parameters of inlet Tri-ethylene glycol (TEG) and natural gas on the performance of absorption column have been analyzed. Results show that revamp of trays with structured packing, can reduce outlet natural gas dew point and improve the positive effect of other parameters on the performance of dehydration unit. Moreover, the most significant factors affecting the HETP were investigated which were less than 15% effective. Finally, the cost of the modification project for the absorption column in the Farashband gas processing plant was calculated. The cost is evaluated 202,909 $ in this case and replacing was found economically justifiable.
