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Tallarek U, Trebel N, Frerichs D, Steinhoff A, Höltzel A. Organic-solvent ditch overlap in reversed-phase liquid chromatography: A molecular dynamics simulation study in cylindrical 6-12 nm-diameter pores. J Chromatogr A 2024; 1726:464960. [PMID: 38718695 DOI: 10.1016/j.chroma.2024.464960] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2024] [Revised: 04/28/2024] [Accepted: 04/30/2024] [Indexed: 05/23/2024]
Abstract
Mass transport through the mesopore space of a reversed-phase liquid chromatography (RPLC) column depends on the properties of the chromatographic interface, particularly on the extent of the organic-solvent ditch that favors the analyte surface diffusivity. Through molecular dynamics simulations in cylindrical RPLC mesopore models with pore diameters between 6 and 12 nm we systematically trace the evolution of organic-solvent ditch overlap due to spatial confinement in the mesopore space of RPLC columns for small-molecule separations. Each pore model of a silica-based, endcapped, C18-stationary phase is equilibrated with two mobile phases of comparable elution strength, namely 70/30 (v/v) water/acetonitrile and 60/40 (v/v) water/methanol, to consider the influence of the mobile-phase composition on the onset of organic-solvent ditch overlap. The simulations show that, as the pore diameter decreases from 9 to 6 nm, the bonded-phase density extends and compacts towards the pore center, which leads to increased accumulation of organic-solvent excess and thus enhanced organic-solvent diffusivity in the ditch. Because the acetonitrile ditch is more pronounced than the methanol ditch, acetonitrile ditch overlap sets in at less severe spatial confinement than methanol ditch overlap. The pore-averaged methanol and acetonitrile diffusivities are considerably raised by ditch overlap in the 6 nm-diameter pore, but also benefit from the ditch (without overlap) in the 7 to 12 nm-diameter pores, whereby local and pore-averaged effects are generally larger for acetonitrile than methanol.
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Affiliation(s)
- Ulrich Tallarek
- Department of Chemistry, Philipps-Universität Marburg, Hans-Meerwein-Strasse 4, Marburg 35032, Germany.
| | - Nicole Trebel
- Department of Chemistry, Philipps-Universität Marburg, Hans-Meerwein-Strasse 4, Marburg 35032, Germany
| | - Daniel Frerichs
- Department of Chemistry, Philipps-Universität Marburg, Hans-Meerwein-Strasse 4, Marburg 35032, Germany
| | - Andreas Steinhoff
- Department of Chemistry, Philipps-Universität Marburg, Hans-Meerwein-Strasse 4, Marburg 35032, Germany
| | - Alexandra Höltzel
- Department of Chemistry, Philipps-Universität Marburg, Hans-Meerwein-Strasse 4, Marburg 35032, Germany
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2
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Gritti F, Lawrence N, Field J. Preparation and investigation of two-component silica-modified hydrophobic layer for minimizing retention loss of reversed-phase chromatographic columns using fully aqueous mobile phases. J Chromatogr A 2024; 1719:464766. [PMID: 38428339 DOI: 10.1016/j.chroma.2024.464766] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2024] [Revised: 02/19/2024] [Accepted: 02/21/2024] [Indexed: 03/03/2024]
Abstract
Chromatographers often employ fully aqueous mobile phases to retain highly polar compounds in reversed-phase liquid chromatography (RPLC). However, when the flow rate is interrupted, either accidentally or intentionally, a substantial loss in retention occurs due to the spontaneous dewetting of water from the hydrophobic surface of conventional RPLC-C18 particles. Previous studies have shown that maintaining a low C18 surface coverage (approximately 1.5 μmol/m2) can mitigate water dewetting by increasing chain disorder, facilitating the intercalation of water clusters between the C18-bonded chains, and keeping the mesopores wetted. In this research, we explore the potential and additional benefits of using two-component surface bonding materials (C8/C18 and PhenylHexyl (PhHx)/C18) at a constant and low total surface coverage of 1.51 ± 0.15 μmol/m2. We synthesized seven one- and two-component modified silica particles with a volume average particle size of 5.22 μm and an average mesopore size of 104 Å. The surface coverage was increased from 0 to 0.54, 1.00, and to 1.66 μmol2 for C8 chains and from 0 to 0.52, 0.70, and to 1.65 μmol2 for PhHx ligands. To prevent interactions between water and any unreacted silanols, all seven derivatized particles were heavily endcapped with trimethylsilane (TMS) reagent. The fraction of the surface area remaining in contact with water was determined by measuring the retention times of weakly (thiourea) and strongly (thymine) retained compounds at intervals of 1, 2, 4, 8, 16, 32, and 64 minutes following the cessation of flow. Two distinct column temperatures, 24°C and 60°C, were employed in the experiments. Retention losses were found to be minimized in the presence of a small quantity of C8 chains (less than 40% of the total surface coverage). Additionally, it is essential to consider substantial fractions of PhHx chains, as long as the presence of the PhHx ligand does not significantly impact retention and selectivity. Combining mixed RPLC bondings with a low total surface coverage of approximately 1.5 μmol/m2 emerges as a viable solution for further minimizing retention loss in standard C18-bonded RPLC columns, particularly within the surface coverage range of 2.5-3.0 μmol/m2.
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Affiliation(s)
- Fabrice Gritti
- Waters Corporation, Instrument/Core Research/Fundamental, 34 Maple Street, Milford, MA, 01757, USA.
| | - Nicole Lawrence
- Waters Corporation, Instrument/Core Research/Fundamental, 34 Maple Street, Milford, MA, 01757, USA
| | - Jessica Field
- Waters Corporation, Instrument/Core Research/Fundamental, 34 Maple Street, Milford, MA, 01757, USA
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3
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Steinhoff A, Höltzel A, Tallarek U. The Solvation Shell of Small Solutes in Aqueous-Organic Solvent Mixtures and Its Implications for Reversed-Phase Liquid Chromatography. J Phys Chem B 2023; 127:10052-10066. [PMID: 37943096 DOI: 10.1021/acs.jpcb.3c05492] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2023]
Abstract
Reversed-phase liquid chromatography (RPLC) operates with water-organic solvent (W-OS) mobile phases where preferential solvation (PS) of solutes is likely. To investigate the relevance of the solute solvation shell in the mobile phase for RPLC retention, we combine data from molecular dynamics simulations of small, neutral solutes (six analytes and two dead time markers) in W-methanol (MeOH) and W-acetonitrile (ACN) mixtures with corresponding retention data obtained on an RPLC column over a wide range of W/OS ratios. Data derived from Kirkwood-Buff integrals show PS by the OS for analytes vs low or negative PS for dead time markers. W-ACN mixtures generate a higher amount of PS than W-MeOH mixtures, which contributes to the higher eluent strength of ACN in RPLC. Difference spatial distribution functions reveal anisotropic solvation shells with OS excess at hydrocarbon elements and W excess at functional groups, predicting that retention by the hydrophobic stationary phase is favored by hydrocarbon elements and limited by functional groups. Analysis of solute-solvent hydrogen bonds pinpoints the hydrogen-bond requirements toward W as the retention-limiting factor. The relation between the solute solvation shell and retention confirms the importance of W-OS and solute-W hydrogen bonding for RPLC retention.
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Affiliation(s)
- Andreas Steinhoff
- Department of Chemistry, Philipps-Universität Marburg, Hans-Meerwein-Strasse 4, Marburg 35032, Germany
| | - Alexandra Höltzel
- Department of Chemistry, Philipps-Universität Marburg, Hans-Meerwein-Strasse 4, Marburg 35032, Germany
| | - Ulrich Tallarek
- Department of Chemistry, Philipps-Universität Marburg, Hans-Meerwein-Strasse 4, Marburg 35032, Germany
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Retention and mass transfer properties of the series of unbonded, amide-bonded, and alkylsulfobetaine-bonded ethylene bridged hybrid hydrophilic interaction liquid chromatography columns. J Chromatogr A 2023; 1692:463828. [PMID: 36804802 DOI: 10.1016/j.chroma.2023.463828] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Revised: 01/23/2023] [Accepted: 01/24/2023] [Indexed: 02/09/2023]
Abstract
This work investigates the link between the retentivity and the stationary phase to mobile phase mass transfer resistance of hydrophilic interaction liquid chromatography (HILIC) columns packed with the same base ethylene-bridged hybrid particles (BEH). The retention volumes, the plate heights, and the volume of the adsorbed water layer were measured for the ACQUITYTM UPLCTM BEHTM 130 Å HILIC Column (unbonded BEH), ACQUITY UPLC BEH 130 Å Amide Column (amide group attached), and AtlantisTM Premier BEH 95 Å Z-HILIC (zwitterionic group attached) Column. The method of Guo (toluene retention volumes in pure acetonitrile and in the HILIC eluent) was validated from the UNIFAC group-contribution method and applied to measure accurately the water layer volumes in these columns. A strong correlation was found between the retention volumes of most neutral polar analytes and the volume of the water layer adsorbed in the HILIC column. The fraction of the pore volume occupied by the water layer increases significantly from the BEH HILIC Column to the BEH Amide Column, and to the BEH Z-HILIC Column. This is explained by the water solvation of the attached ligands in the pore volume of the BEH Particles and to the smaller average mesopore size of the BEH Z-HILIC Particles. A second and strong correlation is also observed between the water content in the HILIC particle and the stationary phase to mobile phase mass transfer resistance of the HILIC columns at high mobile phase linear velocities. The measured intra-particle diffusivity normalized to the bulk diffusion coefficient decreased from 0.33 (BEH HILIC Column) to 0.10 (BEH Amide Column) and to only 0.03 (BEH Z-HILIC Column) for comparable retention of cytosine. These results are fully consistent with the higher viscosity of the internal eluent (higher water content) and higher internal obstruction for diffusion (smaller mesopores and internal porosity) in the BEH Z-HILIC Particles. Still, in gradient elution mode, the peak capacity was found to be 18% higher for the BEH Z-HILIC Column than that on the BEH Amide Column because the retention factors at elution were smaller when maintaining the same analysis time and starting eluent composition.
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Steinhoff A, Höltzel A, Trebel N, Tallarek U. Mobile-Phase Contributions to Organic-Solvent Excess Adsorption and Surface Diffusion in Reversed-Phase Liquid Chromatography. J Phys Chem B 2022; 126:10554-10568. [PMID: 36469753 DOI: 10.1021/acs.jpcb.2c06871] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Fast transport of retained analytes in reversed-phase liquid chromatography occurs through surface diffusion in the organic-solvent (OS)-enriched interfacial "ditch" region between the hydrophobic stationary phase and the water (W)-OS mobile phase. Through molecular dynamics simulations that recover the OS excess adsorption isotherms of a typical C18-stationary phase for methanol and acetonitrile, we explore the relation between OS properties, OS excess adsorption, and surface diffusion. The emerging molecular-level picture attributes the mobile-phase contribution to surface diffusion to the hydrogen-bond capability and the eluting power of the OS. The higher affinity of methanol for the formation of W-OS hydrogen bonds at the soft, hydrophobic surface presented by the bonded-phase (C18) chains reduces the OS excess and the related viscosity drop in the ditch. The lower eluting power of methanol, however, translates to increased bonded-phase contacts for analytes, which can increase their mobility gain from surface diffusion above the gain observed with acetonitrile.
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Affiliation(s)
- Andreas Steinhoff
- Department of Chemistry, Philipps-Universität Marburg, Hans-Meerwein-Strasse 4, 35032Marburg, Germany
| | - Alexandra Höltzel
- Department of Chemistry, Philipps-Universität Marburg, Hans-Meerwein-Strasse 4, 35032Marburg, Germany
| | - Nicole Trebel
- Department of Chemistry, Philipps-Universität Marburg, Hans-Meerwein-Strasse 4, 35032Marburg, Germany
| | - Ulrich Tallarek
- Department of Chemistry, Philipps-Universität Marburg, Hans-Meerwein-Strasse 4, 35032Marburg, Germany
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Trebel N, Höltzel A, Tallarek U. Confinement Effects on Distribution and Transport of Neutral Solutes in a Small Hydrophobic Nanopore. J Phys Chem B 2022; 126:7781-7795. [PMID: 36149739 DOI: 10.1021/acs.jpcb.2c04924] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Molecular dynamics simulations are used to study confinement effects in small cylindrical silica pores with extended hydrophobic surface functionalization as realized, for example, in reversed-phase liquid chromatography (RPLC) columns. In particular, we use a 6 nm cylindrical and a 10 nm slit pore bearing the same C18 stationary phase to compare the conditions inside the smaller-than-average pores within an RPLC column to column-averaged properties. Two small, neutral, apolar to moderately polar solutes are used to assess the consequences of spatial confinement for typical RPLC analytes with water (W)-acetonitrile (ACN) mobile phases at W/ACN ratios between 70/30 and 10/90 (v/v). The simulated data show that true bulk liquid behavior, as observed over an extended center region in the 10 nm slit pore, is not recovered within the 6 nm cylindrical pore. Instead, the ACN-enriched solvent layer around the C18 chain ends (the ACN ditch), a general feature of hydrophobic interfaces equilibrated with aqueous-organic liquids, extends over the entire pore lumen of the small cylindrical pore. This renders the entire pore a highly hydrophobic environment, where, contrary to column-averaged behavior, neither the local nor the pore-averaged sorption and diffusion of analytes scales directly with the W/ACN ratio of the mobile phase. Additionally, the solute polarity-related discrimination between analytes is enhanced. The consequences of local ACN ditch overlap in RPLC columns are reminiscent of ion transport in porous media with charged surfaces, where electrical double-layer overlap occurring locally in smaller pores leads to discrimination between co- and counterionic species.
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Affiliation(s)
- Nicole Trebel
- Department of Chemistry, Philipps-Universität Marburg, Hans-Meerwein-Strasse 4, 35032 Marburg, Germany
| | - Alexandra Höltzel
- Department of Chemistry, Philipps-Universität Marburg, Hans-Meerwein-Strasse 4, 35032 Marburg, Germany
| | - Ulrich Tallarek
- Department of Chemistry, Philipps-Universität Marburg, Hans-Meerwein-Strasse 4, 35032 Marburg, Germany
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7
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Trebel N, Höltzel A, Lutz JK, Tallarek U. Consequences of Cylindrical Pore Geometry for Interfacial Phenomena in Reversed-Phase Liquid Chromatography. J Phys Chem B 2021; 125:11320-11336. [PMID: 34610741 DOI: 10.1021/acs.jpcb.1c06732] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The interfacial phenomena behind analyte separation in a reversed-phase liquid chromatography column take place nearly exclusively inside the silica mesopores. Their cylindrical geometry can be expected to shape the properties of the chromatographic interface with consequences for the analyte density distribution and diffusivity. To investigate this topic through molecular dynamics simulations, we introduce a cylindrical pore inside a slit pore configuration, where the inner curved and outer planar silica surface bear the same bonded phase. The present model replicates an average-sized (9 nm) mesopore in an endcapped C18 column equilibrated with a mobile phase of 70/30 (v/v) water/acetonitrile. Simulations performed for ethylbenzene and acetophenone show that the surface curvature shifts the bonded phase and analyte density toward the pore center, decreases the solvent density in the bonded-phase region, increases the acetonitrile excess in the interfacial region, and considerably enhances the surface diffusivity of both analytes. Overall, the cylindrical pore provides a more hydrophobic environment than the slit pore. Ethylbenzene density is decidedly increased in the cylindrical pore, whereas acetophenone density is nearly equally distributed between the cylindrical and slit pore. The cylindrical pore geometry thus sharpens the discrimination between the apolar and moderately polar analytes while enhancing the mass transport of both.
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Affiliation(s)
- Nicole Trebel
- Department of Chemistry, Philipps-Universität Marburg, Hans-Meerwein-Strasse 4, 35032 Marburg, Germany
| | - Alexandra Höltzel
- Department of Chemistry, Philipps-Universität Marburg, Hans-Meerwein-Strasse 4, 35032 Marburg, Germany
| | - Julia K Lutz
- Department of Chemistry, Philipps-Universität Marburg, Hans-Meerwein-Strasse 4, 35032 Marburg, Germany
| | - Ulrich Tallarek
- Department of Chemistry, Philipps-Universität Marburg, Hans-Meerwein-Strasse 4, 35032 Marburg, Germany
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8
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Klimova YA, Asnin LD. Enantioselective adsorption dynamics of leucyl-leucine in a Chirobiotic R column. J Chromatogr A 2020; 1635:461771. [PMID: 33302135 DOI: 10.1016/j.chroma.2020.461771] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 11/26/2020] [Accepted: 11/26/2020] [Indexed: 12/15/2022]
Abstract
The dynamics of adsorption of the Leu-Leu stereoisomers in a chromatographic column packed with the Chirobiotic R chiral stationary phase bearing grafted antibiotic ristocetin A was studied by means of measurement and analysis of van Deemter plots. Similar measurements were carried out with weakly retained Gly-Gly for the sake of comparison. The bulk diffusion coefficients of the investigated dipeptides were also determined. It is found that the van Deemter plots of both the Leu-Leu stereoisomers and Gly-Gly have an uncommon convex-upward shape. Besides, the van Deemter B coefficients for the Leu-Leu stereoisomers, but not for Gly-Gly, have unusually high values. It is suggested that a high transcolumn contribution to eddy dispersion, which turned out to be enantioselective, accounts for these findings. Adsorption kinetics of all the dipeptides considered is relatively slow, the adsorption rate constant (kads) being of order of magnitude 20-60 s-1. kads does not depend on the configuration of Leu-Leu stereoisomers, although their affinity toward the chiral selector depends on this factor. This supports the above hypothesis that eddy dispersion is mainly responsible for the observed peculiarities in the dynamic behavior of dipeptides, and adsorption kinetics has secondary importance in this phenomenon.
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Affiliation(s)
- Yana A Klimova
- Perm National Research Polytechnic University, 29 Komsomolsky Al., Perm 614990, Russian Federation
| | - Leonid D Asnin
- Perm National Research Polytechnic University, 29 Komsomolsky Al., Perm 614990, Russian Federation.
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9
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Song H, Desmet G, Cabooter D. A Methodology for the Estimation and Modelling of the Obstruction Factor in the Expression for Mesopore Diffusion in Reversed-Phase Liquid Chromatography Particles. J Chromatogr A 2020; 1625:461285. [DOI: 10.1016/j.chroma.2020.461285] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 05/27/2020] [Accepted: 05/28/2020] [Indexed: 01/19/2023]
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10
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Gritti F, Hlushkou D, Tallarek U. Multiple-open-tubular column enabling transverse diffusion. Part 1: Band broadening model for accurate mass transfer predictions. J Chromatogr A 2020; 1625:461325. [DOI: 10.1016/j.chroma.2020.461325] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2020] [Revised: 06/05/2020] [Accepted: 06/05/2020] [Indexed: 12/16/2022]
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11
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Gritti F, Hochstrasser J, Svidrytski A, Hlushkou D, Tallarek U. Morphology-transport relationships in liquid chromatography: Application to method development in size exclusion chromatography. J Chromatogr A 2020; 1620:460991. [DOI: 10.1016/j.chroma.2020.460991] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Revised: 02/13/2020] [Accepted: 02/20/2020] [Indexed: 12/14/2022]
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12
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Khanal O, Kumar V, Schlegel F, Lenhoff AM. Estimating and leveraging protein diffusion on ion-exchange resin surfaces. Proc Natl Acad Sci U S A 2020; 117:7004-7010. [PMID: 32179691 PMCID: PMC7132105 DOI: 10.1073/pnas.1921499117] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Protein mobility at solid-liquid interfaces can affect the performance of applications such as bioseparations and biosensors by facilitating reorganization of adsorbed protein, accelerating molecular recognition, and informing the fundamentals of adsorption. In the case of ion-exchange chromatographic beads with small, tortuous pores, where the existence of surface diffusion is often not recognized, slow mass transfer can result in lower resin capacity utilization. We demonstrate that accounting for and exploiting protein surface diffusion can alleviate the mass-transfer limitations on multiple significant length scales. Although the surface diffusivity has previously been shown to correlate with ionic strength (IS) and binding affinity, we show that the dependence is solely on the binding affinity, irrespective of pH, IS, and resin ligand density. Different surface diffusivities give rise to different protein distributions within the resin, as characterized using confocal microscopy and small-angle neutron scattering (length scales of micrometer and nanometer, respectively). The binding dependence of surface diffusion inspired a protein-loading approach in which the binding affinity, and hence the surface diffusivity, is modulated by varying IS. Such gradient loading increased the protein uptake efficiency by up to 43%, corroborating the importance of protein surface diffusion in protein transport in ion-exchange chromatography.
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Affiliation(s)
- Ohnmar Khanal
- Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, DE 19716
| | - Vijesh Kumar
- Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, DE 19716
| | | | - Abraham M Lenhoff
- Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, DE 19716;
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Gritti F, Tanaka N. Slow injector-to-column sample transport to maximize resolution in liquid chromatography: Theory versus practice. J Chromatogr A 2019; 1600:219-237. [DOI: 10.1016/j.chroma.2019.04.060] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Revised: 04/15/2019] [Accepted: 04/22/2019] [Indexed: 01/08/2023]
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14
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Unusual van Deemter plots of optical isomers on a chiral brush-type liquid chromatography column. J Chromatogr A 2019; 1592:112-121. [PMID: 30683529 DOI: 10.1016/j.chroma.2019.01.048] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Revised: 01/12/2019] [Accepted: 01/17/2019] [Indexed: 11/23/2022]
Abstract
Unusual dynamic behavior of the enantiomers of 9-bromo-11b-(tert-butyl)-2,3,6,11b-tetrahydrooxazolo[3',2':1,5]pyrrolo[3,4-b]quinoline-5,11-dione (I) was observed on a Nautilus-R column packed with silica grafted with antibiotic ristocetin. It consisted in (i) antibatic behavior of the van Deemter plots of the enantiomers and (ii) high and strongly enantiomer dependent values of the A- and B-terms of the van Deemter equation. Although rare, such a pattern has been found earlier in chiral chromatography, with all reported cases limited to brush-type chiral stationary phases. Adsorption dynamics in this system was studied by means of the moment method and the peak parking technique; hydrodynamic properties of the column were explored by using unretained tracers. It was shown that the peculiar shape of the van Deemter curves for the enantiomers of I is conditioned by imperfect packing of the stationary phase, which result in high transcolumn eddy dispersion, and by slow adsorption/desorption kinetics. It was proven that the whole void volume of the column available to an eluent is not accessible to the studied analyte because it cannot penetrate the space between neighboring grafted ligands. Its mass transfer in pores is also affected by the fact that the stagnant layer of the binary water-acetonitrile mobile phase differs in composition from the bulk liquid due to preferential adsorption of water that influences the apparent molecular diffusivity of solutes. An effect of the structures of analyte and chiral selector on the adsorption kinetics is also briefly discussed.
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15
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Hydrazine determination in allopurinol using derivatization and SPE for sample preparation. J Pharm Biomed Anal 2018; 152:25-30. [DOI: 10.1016/j.jpba.2018.01.035] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Revised: 01/08/2018] [Accepted: 01/17/2018] [Indexed: 11/19/2022]
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16
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Lunn DB, Yun YJ, Jorgenson JW. Retention and effective diffusion of model metabolites on porous graphitic carbon. J Chromatogr A 2017; 1530:112-119. [PMID: 29157608 PMCID: PMC5711574 DOI: 10.1016/j.chroma.2017.11.023] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Revised: 11/11/2017] [Accepted: 11/13/2017] [Indexed: 11/12/2022]
Abstract
The study of metabolites in biological samples is of high interest for a wide range of biological and pharmaceutical applications. Reversed phase liquid chromatography is a common technique used for the separation of metabolites, but it provides little retention for polar metabolites. An alternative to C18 bonded phases, porous graphitic carbon has the ability to provide significant retention for both non-polar and polar analytes. The goal of this work is to study the retention and effective diffusion properties of porous graphitic carbon, to see if it is suitable for the wide injection bands and long run times associated with long, packed capillary-scale separations. The retention of a set of standard metabolites was studied for both stationary phases over a wide range of mobile phase conditions. This data showed that porous graphitic carbon benefits from significantly increased retention (often >100 fold) under initial gradient conditions for these metabolites, suggesting much improved ability to focus a wide injection band at the column inlet. The effective diffusion properties of these columns were studied using peak-parking experiments with the standard metabolites under a wide range of retention conditions. Under the high retention conditions, which can be associated with retention after injection loading for gradient separations, Deff/Dm∼0.1 for both the C18-bonded and porous graphitic carbon columns. As C18 bonded particles are widely, and successfully utilized for long gradient separations without issue of increasing peak width from longitudinal diffusion, this suggests that porous graphitic carbon should be amenable for long runtime gradient separations as well.
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Affiliation(s)
- Daniel B Lunn
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Young J Yun
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - James W Jorgenson
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
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Additional band broadening of peptides in the first size-exclusion chromatographic dimension of an automated stop-flow two-dimensional high performance liquid chromatography. J Chromatogr A 2017; 1521:80-89. [DOI: 10.1016/j.chroma.2017.09.025] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Revised: 08/22/2017] [Accepted: 09/08/2017] [Indexed: 12/14/2022]
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18
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Gritti F. Impact of straight, unconnected, radially-oriented, and tapered mesopores on column efficiency: A theoretical investigation. J Chromatogr A 2017; 1485:70-81. [DOI: 10.1016/j.chroma.2017.01.030] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2016] [Revised: 01/09/2017] [Accepted: 01/11/2017] [Indexed: 11/25/2022]
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19
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Property evaluations and application for separation of small molecules of a nanodiamond-polymer composite monolithic column. Talanta 2016; 154:237-48. [DOI: 10.1016/j.talanta.2016.03.069] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Revised: 03/16/2016] [Accepted: 03/19/2016] [Indexed: 11/19/2022]
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20
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Gritti F, Gilar M, Jarrell JA. Achieving quasi-adiabatic thermal environment to maximize resolution power in very high-pressure liquid chromatography: Theory, models, and experiments. J Chromatogr A 2016; 1444:86-98. [DOI: 10.1016/j.chroma.2016.03.070] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Revised: 03/22/2016] [Accepted: 03/23/2016] [Indexed: 11/29/2022]
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21
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Lee IS, Ko KY, Kim IH. Analysis of Cyclic Adenosine Monophosphate (cAMP) Separation via RP-HPLC (reversed-phase high-performance liquid chromatography) by the Moment Method and the van Deemter Equation. KOREAN CHEMICAL ENGINEERING RESEARCH 2015. [DOI: 10.9713/kcer.2015.53.6.723] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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22
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Analysis of R-Limonene separation in RP-HPLC (reversed-phase high-performance liquid chromatography) by Moment method and Van Deemter equation. BIOTECHNOL BIOPROC E 2015. [DOI: 10.1007/s12257-014-0573-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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23
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Gritti F, Guiochon G. The quantitative impact of the mesopore size on the mass transfer mechanism of the new 1.9 μm fully porous Titan-C18 particles. I: Analysis of small molecules. J Chromatogr A 2015; 1384:76-87. [DOI: 10.1016/j.chroma.2015.01.047] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Revised: 01/15/2015] [Accepted: 01/15/2015] [Indexed: 10/24/2022]
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24
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The relative importance of the adsorption and partitioning mechanisms in hydrophilic interaction liquid chromatography. J Chromatogr A 2015; 1376:112-25. [DOI: 10.1016/j.chroma.2014.11.087] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Revised: 11/28/2014] [Accepted: 11/29/2014] [Indexed: 11/18/2022]
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25
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Mass transport of small retained molecules in polymer-based monolithic columns. J Chromatogr A 2014; 1362:49-61. [DOI: 10.1016/j.chroma.2014.07.065] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Revised: 07/18/2014] [Accepted: 07/21/2014] [Indexed: 11/21/2022]
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26
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Gritti F, Bell DS, Guiochon G. Particle size distribution and column efficiency. An ongoing debate revived with 1.9μm Titan-C18 particles. J Chromatogr A 2014; 1355:179-92. [DOI: 10.1016/j.chroma.2014.06.029] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Revised: 06/06/2014] [Accepted: 06/10/2014] [Indexed: 10/25/2022]
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27
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Deridder S, Vanmessen A, Nakanishi K, Desmet G, Cabooter D. Experimental and numerical validation of the effective medium theory for the B-term band broadening in 1st and 2nd generation monolithic silica columns. J Chromatogr A 2014; 1351:46-55. [DOI: 10.1016/j.chroma.2014.04.099] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Revised: 04/07/2014] [Accepted: 04/30/2014] [Indexed: 10/25/2022]
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28
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Gritti F, Guiochon G. The rationale for the optimum efficiency of columns packed with new 1.9μm fully porous Titan-C18 particles-a detailed investigation of the intra-particle diffusivity. J Chromatogr A 2014; 1355:164-78. [PMID: 24969087 DOI: 10.1016/j.chroma.2014.05.076] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Revised: 05/26/2014] [Accepted: 05/27/2014] [Indexed: 12/01/2022]
Abstract
In a previous report, it was reported that columns packed with fully porous 1.9μm Titan-C18 particles provided a minimum reduced plate height as small as 1.7 for the most retained compound (n-octanophenone) under RPLC conditions. These particles are characterized by a relatively narrow size distribution with a relative standard deviation (RSD) of only 10%. A column packed with classical 5μm Symmetry-C18 particles, used as a reference RPLC column, generated a minimum reduced plate height of 2.1 for the same retained compound. This work demonstrates that this was due to an unusually low intra-particle diffusivity across these particles, which leads to a small longitudinal diffusion coefficient along the column. The demonstration is based on the combination of accurate measurements of the height equivalent to a theoretical plate (HETP), inverse size exclusion chromatography (ISEC), peak parking (PP), and minor disturbance method (MDM) experiments. The experimental results show that the reduced eddy dispersion HETP term (A=0.8 for a reduced velocity of 5), the internal particle porosity (ϵp=0.35), and the enrichment of acetonitrile in the pore volume (75% acetonitrile in the bulk, 85% inside the mesoporous volume) are identical on both the Titan-C18 and Symmetry-C18 columns. The difference between the internal structures of these two brands of RPLC-C18 fully porous particles lies in the values of the internal obstruction factor γp, which is 0.42 for the Symmetry-C18 but only 0.26 for the Titan-C18 particles. This is in part related to the diffusion hindrance due to the small average pore size of the Titan-C18 particles, around 59Å versus 77Å for Symmetry-C18 particles. A simple model of constriction along diffusion paths having the shape of a truncated cone suggests that the width of the pore size distribution (RSD of 30% and 20% for Titan-C18 and Symmetry-C18 particles) is mostly responsible for the difference in their obstruction factors.
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Affiliation(s)
- Fabrice Gritti
- Department of Chemistry, University of Tennessee, Knoxville, TN 37996-1600, USA
| | - Georges Guiochon
- Department of Chemistry, University of Tennessee, Knoxville, TN 37996-1600, USA.
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29
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Possible resolution gain in enantioseparations afforded by core–shell particle technology. J Chromatogr A 2014; 1348:87-96. [DOI: 10.1016/j.chroma.2014.04.041] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Revised: 04/08/2014] [Accepted: 04/14/2014] [Indexed: 11/21/2022]
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30
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Mass transfer mechanism in chiral reversed phase liquid chromatography. J Chromatogr A 2014; 1332:35-45. [DOI: 10.1016/j.chroma.2014.01.040] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2013] [Revised: 01/12/2014] [Accepted: 01/14/2014] [Indexed: 11/19/2022]
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31
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Gritti F, Pynt J, Soliven A, Dennis GR, Shalliker RA, Guiochon G. Effect of parallel segmented flow chromatography on the height equivalent to a theoretical plate III – Influence of the column length, particle diameter, and the molecular weight of the analyte on the efficiency gain. J Chromatogr A 2014; 1333:32-44. [DOI: 10.1016/j.chroma.2014.01.055] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Revised: 01/14/2014] [Accepted: 01/18/2014] [Indexed: 12/01/2022]
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32
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Evaluation of the kinetic performance of new prototype 2.1mm×100mm narrow-bore columns packed with 1.6μm superficially porous particles. J Chromatogr A 2014; 1334:30-43. [DOI: 10.1016/j.chroma.2014.01.065] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Revised: 01/17/2014] [Accepted: 01/20/2014] [Indexed: 11/21/2022]
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33
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De Bruyne S, De Malsche W, Deridder S, Gardeniers H, Desmet G. In Situ Measurement of the Transversal Dispersion in Ordered and Disordered Two-Dimensional Pillar Beds for Liquid Chromatography. Anal Chem 2014; 86:2947-54. [DOI: 10.1021/ac403147q] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Selm De Bruyne
- Department
of Chemical Engineering, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
- MESA+ Research
Institute, University of Twente, Enschede, The Netherlands
| | - Wim De Malsche
- Department
of Chemical Engineering, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
- MESA+ Research
Institute, University of Twente, Enschede, The Netherlands
| | - Sander Deridder
- Department
of Chemical Engineering, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
| | - Han Gardeniers
- MESA+ Research
Institute, University of Twente, Enschede, The Netherlands
| | - Gert Desmet
- Department
of Chemical Engineering, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
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34
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Vasudevan V, Loh KC. Transcolumn dispersion in a computational mimic of an analytical silica monolith reconstructed from sub-microtomographic scans using computational fluid dynamics. Sep Purif Technol 2014. [DOI: 10.1016/j.seppur.2013.10.050] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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35
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The van Deemter equation: Assumptions, limits, and adjustment to modern high performance liquid chromatography. J Chromatogr A 2013; 1302:1-13. [DOI: 10.1016/j.chroma.2013.06.032] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Revised: 06/12/2013] [Accepted: 06/13/2013] [Indexed: 11/24/2022]
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36
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Gritti F, Guiochon G. Mass transfer mechanism in hydrophilic interaction chromatography. J Chromatogr A 2013; 1302:55-64. [DOI: 10.1016/j.chroma.2013.06.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2013] [Revised: 05/28/2013] [Accepted: 06/01/2013] [Indexed: 10/26/2022]
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37
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Gritti F, Guiochon G. 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. J Chromatogr A 2013; 1297:64-76. [DOI: 10.1016/j.chroma.2013.04.047] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2013] [Revised: 04/13/2013] [Accepted: 04/15/2013] [Indexed: 10/26/2022]
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38
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Gritti F, Guiochon G. Comparison between the intra-particle diffusivity in the hydrophilic interaction chromatography and reversed phase liquid chromatography modes. Impact on the column efficiency. J Chromatogr A 2013; 1297:85-95. [DOI: 10.1016/j.chroma.2013.04.055] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Revised: 04/16/2013] [Accepted: 04/18/2013] [Indexed: 11/26/2022]
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39
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Gao H, Gritti F, Guiochon G. Investigations on the calculation of the third moments of elution peaks. II—Linear flow speed dependence of external mass transfer coefficient. J Chromatogr A 2013; 1294:41-9. [DOI: 10.1016/j.chroma.2013.04.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Revised: 04/03/2013] [Accepted: 04/04/2013] [Indexed: 11/24/2022]
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40
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Gritti F, Guiochon G. Perspectives on the Evolution of the Column Efficiency in Liquid Chromatography. Anal Chem 2013; 85:3017-35. [DOI: 10.1021/ac3033307] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Fabrice Gritti
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996-1600, United States
| | - Georges Guiochon
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996-1600, United States
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41
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Gritti F, Guiochon G. Theoretical and experimental impact of the bed aspect ratio on the axial dispersion coefficient of columns packed with 2.5μm particles. J Chromatogr A 2012; 1262:107-21. [DOI: 10.1016/j.chroma.2012.09.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2012] [Revised: 08/31/2012] [Accepted: 09/03/2012] [Indexed: 11/30/2022]
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42
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Daneyko A, Hlushkou D, Khirevich S, Tallarek U. From random sphere packings to regular pillar arrays: Analysis of transverse dispersion. J Chromatogr A 2012; 1257:98-115. [DOI: 10.1016/j.chroma.2012.08.024] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2012] [Revised: 08/02/2012] [Accepted: 08/05/2012] [Indexed: 11/26/2022]
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43
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Gritti F, Guiochon G. Repeatability of the efficiency of columns packed with sub-3μm core–shell particles: Part I. 2.6μm Kinetex-C18 particles in 4.6mm and 2.1mm×100mm column formats. J Chromatogr A 2012; 1252:31-44. [DOI: 10.1016/j.chroma.2012.05.072] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Revised: 05/17/2012] [Accepted: 05/21/2012] [Indexed: 10/28/2022]
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44
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Gritti F, Guiochon G. A revisit of the concept of external film mass transfer resistance in the packed beds used in high-performance liquid chromatography. Chem Eng Sci 2012. [DOI: 10.1016/j.ces.2012.01.028] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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45
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Gritti F, Guiochon G. Measurement of the eddy dispersion term in chromatographic columns. II. Application to new prototypes of 2.3 and 3.2mm I.D. monolithic silica columns. J Chromatogr A 2012; 1227:82-95. [DOI: 10.1016/j.chroma.2011.12.065] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2011] [Revised: 12/14/2011] [Accepted: 12/19/2011] [Indexed: 11/30/2022]
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46
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Gritti F, Guiochon G. Measurement of the eddy dispersion term in chromatographic columns: III. Application to new prototypes of 4.6mm I.D. monolithic columns. J Chromatogr A 2012; 1225:79-90. [DOI: 10.1016/j.chroma.2011.12.055] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2011] [Revised: 12/14/2011] [Accepted: 12/15/2011] [Indexed: 12/01/2022]
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47
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Mass transfer kinetics, band broadening and column efficiency. J Chromatogr A 2012; 1221:2-40. [DOI: 10.1016/j.chroma.2011.04.058] [Citation(s) in RCA: 216] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2011] [Revised: 04/20/2011] [Accepted: 04/21/2011] [Indexed: 11/23/2022]
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48
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Investigations on the calculation of the third moments of elution peaks. I: Composite signals generated by adding up a mathematical function and experimental noise. J Chromatogr A 2012; 1222:81-9. [DOI: 10.1016/j.chroma.2011.12.015] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2011] [Revised: 11/22/2011] [Accepted: 12/04/2011] [Indexed: 11/22/2022]
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49
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Guiochon G, Beaver LA. Separation science is the key to successful biopharmaceuticals. J Chromatogr A 2011; 1218:8836-58. [DOI: 10.1016/j.chroma.2011.09.008] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2011] [Revised: 09/04/2011] [Accepted: 09/05/2011] [Indexed: 10/17/2022]
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50
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Extending the Total Pore Blocking method to normal phase high performance liquid chromatography. J Chromatogr A 2011; 1218:7781-7. [DOI: 10.1016/j.chroma.2011.08.073] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2011] [Revised: 08/22/2011] [Accepted: 08/23/2011] [Indexed: 11/17/2022]
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