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Miyagawa A, Yamada K, Nakatani K. Investigating hydrophobic environment in alkyl-group-functionalized silica particle with various chain lengths using absorption microspectroscopy. ANAL SCI 2024; 40:93-99. [PMID: 37814176 DOI: 10.1007/s44211-023-00434-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Accepted: 09/22/2023] [Indexed: 10/11/2023]
Abstract
A well-known solvatochromic dye, Reichardt's dye (R-dye), was used to evaluate the hydrophobicity of alkyl-group-functionalized silica particles (ASPs) with different chain lengths. The absorption spectra of R-dye were measured in a single ASP in a mixed solution of water and an organic solvent (methanol (MeOH), ethanol (EtOH), acetonitrile (ACN), tetrahydrofuran (THF), or N,N-dimethylformamide (DMF)) using absorption microspectroscopy. The polarity parameter in the ASPs (ET), determined by the absorption maximum, was observed to be smaller than those in bulk solutions, indicating that R-dye was present in a more hydrophobic environment. In EtOH, THF, and DMF, R-dye was distributed within the alkyl chain layer including the organic solvent. An increase in the organic solvent content of the bulk solution led to a higher organic solvent concentration in the alkyl chain layer, resulting in a decrease in ET. In MeOH and ACN, the R-dye was distributed within the alkyl chain layer and concentrated phase. Moreover, with the increase in the organic molecule content, the distribution of R-dye in the concentrated phase became dominant in MeOH and ACN system, leading to an increase in the ET value. The findings presented in this paper are expected to attract the attention of a wide range of researchers in chromatography.
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Affiliation(s)
- Akihisa Miyagawa
- Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki, 305-8577, Japan.
| | - Kazuki Yamada
- Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki, 305-8577, Japan
| | - Kiyoharu Nakatani
- Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki, 305-8577, Japan
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2
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Sander LC. Separations by Shape: Molecular Shape Recognition in Liquid Chromatography. Chromatographia 2022; 85:10.1007/s10337-022-04137-z. [PMID: 38567378 PMCID: PMC10986420 DOI: 10.1007/s10337-022-04137-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Revised: 02/08/2022] [Accepted: 02/09/2022] [Indexed: 11/03/2022]
Abstract
Molecular shape can provide a basis for chromatographic separations that is distinct from other interaction mechanisms often considered in liquid chromatography. Molecular shape recognition, or shape selectivity, is most evident for the separation of isomeric compounds that have constrained molecular structures, such as polycyclic aromatic hydrocarbons. A central feature of shape-selective columns is conformational order within the stationary phase; this aspect of stationary phase morphology is revealed through spectroscopic studies and molecular dynamics simulations, and is correlated with chromatographic performance.
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Affiliation(s)
- Lane C. Sander
- National Institute of Standards and Technology (NIST), Chemical Sciences Division 100 Bureau Drive, MS 8390, Gaithersburg, MD 20899-8390, USA
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3
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Zhang Y, Chen M, Zhou S, Han H, Zhang M, Qiu H. A carbonylative coupling approach to alkyl stationary phases with variable embedded carbamate groups for high-performance liquid chromatography. J Chromatogr A 2021; 1661:462718. [PMID: 34875517 DOI: 10.1016/j.chroma.2021.462718] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Revised: 11/12/2021] [Accepted: 11/26/2021] [Indexed: 12/15/2022]
Abstract
A highly efficient carbonylative coupling method for the preparation of alkyl stationary phases with variable numbers of carbamate groups was established. The effectiveness of such method was verified through elemental analysis, X-ray photoelectron spectroscopy and solid-state 13C nuclear magnetic resonance spectroscopy of three as-synthesized stationary phases bearing different alkyl chains and different numbers of carbamate groups (octadecyl/one carbamate group, C18C; docosyl/three carbamate groups, C22C3; triacontyl/two carbamate groups, C30C2). The comparative evaluation of these stationary phases using a great variety of analytes, including three sets of isomers of alkylbenzenes, two sets of standard mixtures of polycyclic aromatic hydrocarbons (SRM 1647e and 869b), nine polychlorinated biphenyls, fiveteen N-substituted ureas, ten sulfonylureas, five xanthines and some other phytonutrients, revealed their remarkable applicability in reversed-phase liquid chromatography. Notably, the intercalated carbamate groups rendered the resultant stationary phases compatible with 100% aqueous mobile phase. The suppression of silanol activity was positively related to the number of polar groups embedded in the bonded selector, and the smallest peak tailing factor (1.14) for amitriptyline was obtained by C22C3. The molecular shape-related selectivity was found to be more closely related to the length of the selector's aliphatic chain, as supported by the lowest αTBN/BaP value (0.31) by C30C2. These carbamate-embedded alkyl stationary phases constituted another class of polar-embedded stationary phases possessing a single type of functional ligand.
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Affiliation(s)
- Yujie Zhang
- School of Chemistry and Chemical Engineering, Huaiyin Normal University, Huai'an, 223000, China; CAS Key Laboratory of Chemistry of Northwestern Plant Resources and Key Laboratory for Natural Medicine of Gansu Province, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, 730000, China
| | - Min Chen
- Jiangsu Hanbon Science & Technology Co., Ltd., Huai'an, 223000, China
| | - Shouyong Zhou
- School of Chemistry and Chemical Engineering, Huaiyin Normal University, Huai'an, 223000, China
| | - Haifeng Han
- Jiangsu Hanbon Science & Technology Co., Ltd., Huai'an, 223000, China; CAS Key Laboratory of Chemistry of Northwestern Plant Resources and Key Laboratory for Natural Medicine of Gansu Province, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, 730000, China
| | - Mingliang Zhang
- Jiangsu Hanbon Science & Technology Co., Ltd., Huai'an, 223000, China; CAS Key Laboratory of Chemistry of Northwestern Plant Resources and Key Laboratory for Natural Medicine of Gansu Province, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, 730000, China.
| | - Hongdeng Qiu
- CAS Key Laboratory of Chemistry of Northwestern Plant Resources and Key Laboratory for Natural Medicine of Gansu Province, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, 730000, China; College of Chemistry, Zhengzhou University, Zhengzhou, 450001, China.
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Mileo PGM, Rogge SMJ, Houlleberghs M, Breynaert E, Martens JA, Van Speybroeck V. Interfacial study of clathrates confined in reversed silica pores. J Mater Chem A Mater 2021; 9:21835-21844. [PMID: 34707871 PMCID: PMC8491980 DOI: 10.1039/d1ta03105h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Accepted: 08/22/2021] [Indexed: 05/08/2023]
Abstract
Storing methane in clathrates is one of the most promising alternatives for transporting natural gas (NG) as it offers similar gas densities to liquefied and compressed NG while offering lower safety risks. However, the practical use of clathrates is limited given the extremely low temperatures and high pressures necessary to form these structures. Therefore, it has been suggested to confine clathrates in nanoporous materials, as this can facilitate clathrate's formation conditions while preserving its CH4 volumetric storage. Yet, the choice of nanoporous materials to be employed as the clathrate growing platform is still rather arbitrary. Herein, we tackle this challenge in a systematic way by computationally exploring the stability of clathrates confined in alkyl-grafted silica materials with different pore sizes, ligand densities and ligand types. Based on our findings, we are able to propose key design criteria for nanoporous materials favoring the stability of a neighbouring clathrate phase, namely large pore sizes, high ligand densities, and smooth pore walls. We hope that the atomistic insight provided in this work will guide and facilitate the development of new nanomaterials designed to promote the formation of clathrates.
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Affiliation(s)
- Paulo G M Mileo
- Center for Molecular Modeling (CMM), Ghent University Technologiepark 46 B-9052 Zwijnaarde Belgium
| | - Sven M J Rogge
- Center for Molecular Modeling (CMM), Ghent University Technologiepark 46 B-9052 Zwijnaarde Belgium
| | - Maarten Houlleberghs
- Center for Surface Chemistry and Catalysis, Katholieke Universiteit Leuven Celestijnenlaan 200F 3001 Heverlee Belgium
| | - Eric Breynaert
- Center for Surface Chemistry and Catalysis, Katholieke Universiteit Leuven Celestijnenlaan 200F 3001 Heverlee Belgium
| | - Johan A Martens
- Center for Surface Chemistry and Catalysis, Katholieke Universiteit Leuven Celestijnenlaan 200F 3001 Heverlee Belgium
| | - Veronique Van Speybroeck
- Center for Molecular Modeling (CMM), Ghent University Technologiepark 46 B-9052 Zwijnaarde Belgium
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Han H, Zhang Y, Lu R, Zhang M. An alternative approach for preparation of amide-embedded stationary phase for reversed-phase liquid chromatography. J Chromatogr A 2019; 1593:24-33. [DOI: 10.1016/j.chroma.2019.01.054] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2018] [Revised: 01/15/2019] [Accepted: 01/19/2019] [Indexed: 11/27/2022]
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Zhang Y, Li Q, Zhong H, Zhou S, Zhao Y, Zhang M, Han H, Qiu H. Tuning selectivity via electronic interaction: Preparation and systematic evaluation of serial polar-embedded aryl stationary phases bearing large polycyclic aromatic hydrocarbons. Anal Chim Acta 2018; 1036:162-171. [DOI: 10.1016/j.aca.2018.09.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Revised: 08/29/2018] [Accepted: 09/01/2018] [Indexed: 11/26/2022]
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Zhang Y, Li Q, Dai B, Zhou S, Zhang M, Han H, Qiu H. A versatile polar-embedded polyphenyl phase for multimodal separation in liquid chromatography. J Chromatogr A 2018; 1553:81-89. [DOI: 10.1016/j.chroma.2018.04.025] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Revised: 04/07/2018] [Accepted: 04/10/2018] [Indexed: 10/17/2022]
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8
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Oña-ruales JO, Sander LC, Wilson WB, Wise SA. Revisiting shape selectivity in liquid chromatography for polycyclic aromatic hydrocarbons (PAHs) – six-ring and seven-ring Cata-condensed PAH isomers of molecular mass 328 Da and 378 Da. Anal Bioanal Chem 2018; 410:885-96. [DOI: 10.1007/s00216-017-0456-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Revised: 05/30/2017] [Accepted: 06/07/2017] [Indexed: 10/19/2022]
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9
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Rybka J, Kärger J, Tallarek U. Single-Molecule and Ensemble Diffusivities in Individual Nanopores with Spatially Dependent Mobility. Chemphyschem 2017; 18:2094-2102. [DOI: 10.1002/cphc.201700231] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Revised: 05/19/2017] [Indexed: 11/09/2022]
Affiliation(s)
- Julia Rybka
- Department of Chemistry; Philipps-Universität Marburg; Hans-Meerwein-Strasse 4 35032 Marburg Germany
| | - Jörg Kärger
- Faculty of Physics and Earth Sciences; Universität Leipzig; Linnéstrasse 5 04103 Leipzig Germany
| | - Ulrich Tallarek
- Department of Chemistry; Philipps-Universität Marburg; Hans-Meerwein-Strasse 4 35032 Marburg Germany
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Yui Y, Miyazaki S, Ma Y, Ohira M, Fiehn O, Ikegami T, McCalley DV, Tanaka N. Distinction of synthetic dl-α-tocopherol from natural vitamin E (d-α-tocopherol) by reversed-phase liquid chromatography. Enhanced selectivity of a polymeric C18 stationary phase at low temperature and/or at high pressure. J Chromatogr A 2016; 1450:45-52. [PMID: 27157422 DOI: 10.1016/j.chroma.2016.04.076] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Revised: 04/06/2016] [Accepted: 04/27/2016] [Indexed: 10/21/2022]
Abstract
Separation of diastereomers of dl-α-tocopherol was studied by reversed-phase liquid chromatography using three types of stationary phases, polymeric ODS, polymeric C30, and monomeric ODS. Polymeric ODS stationary phase (Inertsil ODS-P, 3mmID, 20cm) was effective for the separation of the isomers created by the presence of three chiral centers on the alkyl chain of synthetic dl-α-tocopherol. Considerable improvement of the separation of isomers was observed on ODS-P phase at high pressure and at low temperature. Complete separation of four pairs of diastereomers was achieved at 12.0°C, 536bar, while three peaks were observed when the separation was carried out either at 12.0°C at low pressure or at 20°C at 488bar. Higher temperature (30.0°C) with the ODS-P phase resulted in only partial separation of the diastereomers even at high pressure. Only slight resolution was observed for the mixture of diastereomers with the C30 stationary phase (Inertsil C30) at 12.0°C and 441bar, although the stationary phase afforded greater resolution for β- and γ-tocopherol than ODS-P. A monomeric C18 stationary phase did not show any separation at 12.0°C and 463bar. The results suggest that the binding site of the polymeric ODS-P phase is selective for flexible alkyl chains that provided the longest retention for the natural form, (R,R,R) form, and the enantiomer, (S,S,S) form, of dl-α-tocopherol.
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Affiliation(s)
- Yuko Yui
- GL Sciences Inc., Iruma, Saitama 358-0032, Japan
| | | | - Yan Ma
- University of California, Davis, 451 Health Sciences Drive, Davis, CA 95616, USA
| | | | - Oliver Fiehn
- University of California, Davis, 451 Health Sciences Drive, Davis, CA 95616, USA; University of Jeddah, Biochemistry Department, Saudi Arabia
| | - Tohru Ikegami
- Kyoto Institute of Technology, Kyoto 606-8585, Japan
| | | | - Nobuo Tanaka
- GL Sciences Inc., Iruma, Saitama 358-0032, Japan.
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12
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Okusa K, Iwasaki Y, Kuroda I, Miwa S, Ohira M, Nagai T, Mizobe H, Gotoh N, Ikegami T, McCalley DV, Tanaka N. Effect of pressure on the selectivity of polymeric C18 and C30 stationary phases in reversed-phase liquid chromatography. Increased separation of isomeric fatty acid methyl esters, triacylglycerols, and tocopherols at high pressure. J Chromatogr A 2014; 1339:86-95. [DOI: 10.1016/j.chroma.2014.02.077] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2013] [Revised: 02/11/2014] [Accepted: 02/27/2014] [Indexed: 10/25/2022]
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13
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Borówko M, Sokołowski S, Staszewski T. Terminally Grafted Chain Layers in Oligomer–Monomer Solutions: Predictions from a Density Functional Theory. J Phys Chem B 2013; 117:10293-303. [DOI: 10.1021/jp4027546] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Affiliation(s)
- M. Borówko
- Department
for the Modeling
of Physico-Chemical Processes, Maria Curie-Skłodowska University, 20-031 Lublin, Poland
| | - S. Sokołowski
- Department
for the Modeling
of Physico-Chemical Processes, Maria Curie-Skłodowska University, 20-031 Lublin, Poland
| | - T. Staszewski
- Department
for the Modeling
of Physico-Chemical Processes, Maria Curie-Skłodowska University, 20-031 Lublin, Poland
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14
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Fatunmbi HO, Bruch MD. Characterization of the structural morphology of chemically modified silica prepared by surface polymerization of a mixture of long and short alkyl chains using 13C and 29Si NMR spectroscopy. Langmuir 2013; 29:4974-4987. [PMID: 23530776 DOI: 10.1021/la3040853] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
A series of bonded phases were prepared by the chemical modification of silica using the surface polymerization of trifunctional and difunctional ligands, and the structural morphology was characterized by solid-state nuclear magnetic resonance (NMR) spectroscopy using cross-polarization and magic angle spinning (CP/MAS). Mixed-phase surfaces were prepared using mixtures of trifunctional long-chain (C18) ligands with trifunctional and difunctional short-chain (C1) ligands, and these surfaces were compared to the corresponding single-phase surfaces consisting of only long- or short-chain ligands. For both types of mixed-phase surfaces, the incorporation of short chains increases the overall ligand density, the density of long chains, and the degree of cross-linking between ligands compared to that of the single-phase surface consisting exclusively of long chains. When the percentage of long-chain ligands in the mixture is high, a horizontally polymerized monolayer of chains is formed on the silica surface for both trifunctional and difunctional short chains. However, essentially all of the long chains adopt a trans conformation when trifunctional short chains are used, and a significant number of gauche defects are observed for the long chains when mixed with difunctional short chains. Furthermore, the ligands on the mixed-phase surface are more rigid when the short chains are trifunctional. When the percentage of trifunctional short chains is increased, some vertical polymerization occurs, caused by the molecular stacking of the highly reactive short chains near the surface. However, this does not preclude cross-linking between the ligands necessary to seal the surface, and the degree of cross-linking is quite high, suggesting that the short chains cross-link both vertically, away from the surface, and horizontally, across the surface. No such vertical polymerization is observed for the bulkier difunctional short chains. For both trifunctional and difunctional short chains, the surface chains are more mobile, with a greater number of gauche conformations among the long chains when the percentage of short-chain ligands in the reaction mixture is increased.
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Affiliation(s)
- Hafeez O Fatunmbi
- Separation Methods Technologies, Inc., 31 Blue Hen Drive, Newark, Delaware 19713, United States
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15
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Lindsey RK, Rafferty JL, Eggimann BL, Siepmann JI, Schure MR. Molecular simulation studies of reversed-phase liquid chromatography. J Chromatogr A 2013; 1287:60-82. [PMID: 23489490 DOI: 10.1016/j.chroma.2013.02.040] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2013] [Revised: 02/10/2013] [Accepted: 02/11/2013] [Indexed: 11/28/2022]
Abstract
Over the past 20 years, molecular simulation methods have been applied to the modeling of reversed-phase liquid chromatography (RPLC). The purpose of these simulations was to provide a molecular-level understanding of: (i) the structure and dynamics of the bonded phase and its interface with the mobile phase, (ii) the interactions of analytes with the bonded phase, and (iii) the retention mechanism for different analytes. However, the investigation of chromatographic systems poses significant challenges for simulations with respect to the accuracy of the molecular mechanics force fields and the efficiency of the sampling algorithms. This review discusses a number of aspects concerning molecular simulation studies of RPLC systems including the historical development of the subject, the background needed to understand the two prevalent techniques, molecular dynamics (MD) and Monte Carlo (MC) methods, and the wealth of insight provided by these simulations. Examples from the literature employing MD approaches and from the authors' laboratory using MC methods are discussed. The former can provide information on chain dynamics and transport properties, whereas the latter techniques are uniquely suited for the investigation of phase and sorption equilibria that underly RPLC retention, and both can be used to elucidate the bonded-chain conformations and solvent distributions.
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Affiliation(s)
- Rebecca K Lindsey
- Department of Chemistry and Chemical Theory Center, University of Minnesota, 207 Pleasant Street SE, Minneapolis, MN 55455-0431, USA
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Borówko M, Sokołowski S, Staszewski T. Adsorption from Oligomer–Monomer Solutions on the Surfaces Modified with End-Grafted Chains. J Phys Chem B 2012; 116:12842-9. [DOI: 10.1021/jp305624n] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- M. Borówko
- Department for the Modeling
of Physico-Chemical
Processes, Maria Curie-Skłodowska University, 20-031 Lublin, Poland
| | - S. Sokołowski
- Department for the Modeling
of Physico-Chemical
Processes, Maria Curie-Skłodowska University, 20-031 Lublin, Poland
| | - T. Staszewski
- Department for the Modeling
of Physico-Chemical
Processes, Maria Curie-Skłodowska University, 20-031 Lublin, Poland
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Affiliation(s)
- Prashant Kumar Gupta
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056 Basel, Switzerland
| | - Markus Meuwly
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056 Basel, Switzerland
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Hall K, Ashtari M, Cann NM. On simulations of complex interfaces: Molecular dynamics simulations of stationary phases. J Chem Phys 2012; 136:114705. [DOI: 10.1063/1.3693516] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
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Affiliation(s)
- M. Borówko
- Department for the Modeling
of Physico-Chemical
Processes, Maria Curie-Skłodowska University, 20-031 Lublin, Poland
| | - S. Sokołowski
- Department for the Modeling
of Physico-Chemical
Processes, Maria Curie-Skłodowska University, 20-031 Lublin, Poland
| | - T. Staszewski
- Department for the Modeling
of Physico-Chemical
Processes, Maria Curie-Skłodowska University, 20-031 Lublin, Poland
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Marchetti N, Pasti L, Dondi F, Cavazzini A. Recent Developments and Applications in Nonlinear Reversed Phase Liquid Chromatography. Adv Chromatogr 2012; 50:415-40. [PMID: 26437517 DOI: 10.1201/b11636-10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Rafferty JL, Siepmann JI, Schure MR. Retention mechanism for polycyclic aromatic hydrocarbons in reversed-phase liquid chromatography with monomeric stationary phases. J Chromatogr A 2011; 1218:9183-93. [DOI: 10.1016/j.chroma.2011.10.043] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2011] [Revised: 10/11/2011] [Accepted: 10/17/2011] [Indexed: 10/15/2022]
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Rafferty JL, Siepmann JI, Schure MR. Mobile phase effects in reversed-phase liquid chromatography: A comparison of acetonitrile/water and methanol/water solvents as studied by molecular simulation. J Chromatogr A 2011; 1218:2203-13. [DOI: 10.1016/j.chroma.2011.02.012] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2010] [Revised: 01/28/2011] [Accepted: 02/05/2011] [Indexed: 11/16/2022]
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Hu SQ, Guo AL, Yan YG, Jia XL, Geng YF, Guo WY. Computer simulation of diffusion of corrosive particle in corrosion inhibitor membrane. COMPUT THEOR CHEM 2011. [DOI: 10.1016/j.comptc.2010.12.019] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Zhang L, Zhao G, Sun Y. Effects of Ligand Density on Hydrophobic Charge Induction Chromatography: Molecular Dynamics Simulation. J Phys Chem B 2010; 114:2203-11. [DOI: 10.1021/jp903852c] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Lin Zhang
- Department of Biochemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
| | - Guofeng Zhao
- Department of Biochemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
| | - Yan Sun
- Department of Biochemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
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Kaliszan R, Bączek T. QSAR in Chromatography: Quantitative Structure–Retention Relationships (QSRRs). Challenges and Advances in Computational Chemistry and Physics 2010. [DOI: 10.1007/978-1-4020-9783-6_8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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28
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Andrzejewska A, Gritti F, Guiochon G. Investigation of the adsorption mechanism of a peptide in reversed phase liquid chromatography, from pH controlled and uncontrolled solutions. J Chromatogr A 2009; 1216:3992-4004. [DOI: 10.1016/j.chroma.2009.03.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2008] [Revised: 03/02/2009] [Accepted: 03/06/2009] [Indexed: 10/21/2022]
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Gritti F, Guiochon G. Adsorption mechanism of acids and bases in reversed-phase liquid chromatography in weak buffered mobile phases designed for liquid chromatography/mass spectrometry. J Chromatogr A 2009; 1216:1776-88. [DOI: 10.1016/j.chroma.2008.10.064] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2008] [Revised: 10/10/2008] [Accepted: 10/14/2008] [Indexed: 11/28/2022]
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Gritti F, Guiochon G. Peak shapes of acids and bases under overloaded conditions in reversed-phase liquid chromatography, with weakly buffered mobile phases of various pH: A thermodynamic interpretation. J Chromatogr A 2009; 1216:63-78. [DOI: 10.1016/j.chroma.2008.11.020] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2008] [Revised: 11/03/2008] [Accepted: 11/07/2008] [Indexed: 10/21/2022]
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Rafferty JL, Siepmann J, Schure MR. Influence of bonded-phase coverage in reversed-phase liquid chromatography via molecular simulation. J Chromatogr A 2008; 1204:11-9. [DOI: 10.1016/j.chroma.2008.07.037] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2008] [Revised: 06/24/2008] [Accepted: 07/04/2008] [Indexed: 10/21/2022]
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Chandrasekar K, Vijay R, Baskar G. Ionic polymeric amphiphiles with cholesterol mesogen: adsorption and organization characteristics at the air/water interface from Langmuir film balance studies. Biomacromolecules 2008; 9:1264-72. [PMID: 18307308 DOI: 10.1021/bm701252y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Ionic polymeric amphiphiles consisting of cholesterol mesogen were investigated for the interfacial adsorption characteristics at the air/water interface using a Langmuir film balance with an aim to understand the influence of ionic segment from 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS) on the packing behavior of cholesterol at the interface. From surface pressure (pi)-area (A) isotherm characteristics, it is demonstrated that the homopolymer and the copolymer C consisting of 0.15 mol fraction CAB segments exhibit the most expanded structures contributing to surface area of about 84 A(2)/molecule. It is shown that the copolymer B with 0.1 mol fraction CAB provides optimum hydrophilic liphophilic balance to form the most compact structures contributing to a surface area of 35.75 A(2)/molecule. The high surface pressure, >40 mN/m, in contrast to that of PAMPS demonstrates significant adsorption of the copolymers at the interface. An interesting correlation among interfacial packing characteristics, thermal behavior, and solution structures is demonstrated. From molecular models developed for CAB, it is shown that the horizontal orientation of the linker group with respect to cholesterol chain in CAB underlies the expanded structures observed in PCAB and copolymer C.
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Affiliation(s)
- K Chandrasekar
- Industrial Chemistry Laboratory, Central Leather Research Institute, Adyar, Chennai 600 020, India
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Gritti F, Kazakevich YV, Guiochon G. Effect of the surface coverage of endcapped C18-silica on the excess adsorption isotherms of commonly used organic solvents from water in reversed phase liquid chromatography. J Chromatogr A 2007; 1169:111-24. [PMID: 17875311 DOI: 10.1016/j.chroma.2007.08.071] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2007] [Revised: 08/27/2007] [Accepted: 08/30/2007] [Indexed: 11/22/2022]
Abstract
The excess adsorption isotherms of methanol, ethanol, 2-propanol, acetonitrile, and tetrahydrofuran from water were measured on five different silica-based packing materials by the minor disturbance method. These materials were prepared with the same lot of 5-microm particles (average pore size 90 A), all endcapped with trimethylchlorosilane (TMS), and bonded to octadecyl chains with different surface coverages (0, 0.42, 1.01, 2.03, and 3.15 micromol/m2). The relative adsorption of one eluent by respect to a second one informs on the heterogeneity of the material (alkyl-bonded and bare silica regions) and on the accessibility of the unreacted silanol groups to the mobile phase. It is shown that the total surface area of the adsorbent decreases with increasing degree of surface coverage with octadecyl chains and that the relative surface area of the regions occupied by accessible silanol groups to the regions occupied by alkyl-bonded groups decreases. For the five columns, an average of 10% of the adsorbent surface area is covered of bare silica accessible to the liquid phase, with a minimum of 5% with tetrahydrofuran and a maximum of 12% with ethanol or 2-propanol. Increasing the surface coverage by the C18 chains causes a significant increase of the attraction potential of the hydrophobic surface toward the organic solvent. This result is confirmed by the increase of the number of adsorbate monolayers with increasing bonding density of the octadecyl chains. This number is twice larger for the 315C18 column than for the C1 column.
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Affiliation(s)
- Fabrice Gritti
- Department of Chemistry, University of Tennessee, Knoxville, TN 37996-1600, USA
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Abstract
Fully atomistic simulations are used to characterize the molecular dynamics (MD) of acridine orange (3,6-dimethylaminoacridine) at a chromatographic interface. Multiple 1 ns MD simulations were performed for acridine orange at the interface between three different acetonitrile/water mixtures (0/100, 20/80, and 50/50) with C8 and C18 alkyl chains. The diffusion coefficient, D, of acridine orange in pure solvent was found to be 4 times smaller at the water/C18 interface (D = 0.022 x 10(-4) cm2/s) than in bulk water (D = 0.087 x 10(-4) cm2/s), in qualitative agreement with experiment. Rotational reorientation times were 20 and 700 ps, which also agree favorably with the measured time scales of 130 and 740 ps. Contrary to experiment, the simulations found that for increasing surface coverage, the diffusion coefficient for acridine decreased. Detailed analysis of the solvent structure showed that the transport properties of acridine were primarily governed by the solvent distribution above the functionalized surface. The solvent structure, in turn, was largely determined by the surface consisting of the silica layer, the alkyl chains, and their functionalization.
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Affiliation(s)
- Antony Fouqueau
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056 Basel, Switzerland
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Abstract
The properties of stationary phases and their characterization methods are reviewed. New and significant developments have occurred in the last few years, and new methods for stationary phase characterization have become available. The characterization methods are discussed, and the differences between the different methods are pointed out. In addition, method development approaches are reviewed, with special emphasis on recent developments that employ multiple parameters in parallel. Also, the renewed interest of temperature as a tool in method development is surveyed.
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Affiliation(s)
- Uwe D Neue
- Waters Corporation, Milford, MA 01757, USA.
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Prathab B, Aminabhavi TM. Atomistic simulations to compute surface properties of poly(N-vinyl-2-pyrrolidone) (PVP) and blends of PVP/chitosan. Langmuir 2007; 23:5439-44. [PMID: 17402756 DOI: 10.1021/la063228u] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Atomistic simulations were performed on poly(N-vinyl-2-pyrrolidone) (PVP) and its blends with chitosan (CS) in different ratios using molecular mechanics (MM) and molecular dynamics (MD) simulations in three-dimensionally periodic and effective two-dimensionally periodic condensed phases. Four independent microstructures were generated to analyze their surface properties. The calculated surface-energy values for PVP compared quite well with the experimental data reported in the literature. The density profile was analyzed, and the structure of the films showed an interior region of the bulk density. Various components of the energetic interactions (torsional, van der Waals, etc.) were examined to gain deeper insight into the nature of regular and anomalous interactions between the bulk and the surface films. Surface energies of PVP/CS blends were computed by MD simulations using the bulk pressure-volume-temperature (PVT) parameters. Bulk properties such as the cohesive energy density (CED) and solubility parameter (delta) were calculated using MM and MD simulations in the NVT ensemble under periodic boundary conditions. The Flory equation of state was used to compute the thermal expansion coefficient as well as PVT parameters. These surface-energy values agreed well with the surface-energy data calculated using the Zisman equation, which were also in accordance with the experimental observations. The results from this study suggest that computer simulations would provide valuable information on polymers and polymer-blend surfaces.
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Affiliation(s)
- B Prathab
- Molecular Modeling Division, Center of Excellence in Polymer Science, Karnatak University, Dharwad, India 580 003
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38
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Prathab B, Aminabhavi TM. Molecular modeling study on surface, thermal, mechanical and gas diffusion properties of chitosan. ACTA ACUST UNITED AC 2007. [DOI: 10.1002/polb.21109] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Gritti F, Guiochon G. Experimental evidence of the influence of the surface chemistry of the packing material on the column pressure drop in reverse-phase liquid chromatography. J Chromatogr A 2006; 1136:192-201. [PMID: 17046011 DOI: 10.1016/j.chroma.2006.09.075] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2006] [Revised: 09/06/2006] [Accepted: 09/20/2006] [Indexed: 11/17/2022]
Abstract
The permeabilities of six columns packed with different packing materials (neat silica, C(1) endcapped silica at 3.92 micro mol/m(2), C(18) bonded and endcapped silica with 0.42, 1.01, 2.03, and 3.15 micro mol/m(2) of C(18) bonded chains) were measured. All these materials derive from the same batch of spherical particles, 5 micro m in diameter. The columns have the same tube inner diameter (phi=0.460+/-0.003 cm) and length (L=15.000+/-0.003 cm). The experimental conditions were the same, flow-rate (F(v)=1.000+/-0.003 mL/min) and temperature (295 K). Nevertheless, it was found that the column permeability decreases significantly, by about 25%, from the neat silica column to the one packed with the highest density of C(18)-bonded silica (3.15 micro mol/m(2)). The results measured on two duplicate columns were very reproducible. Accurate (+/-0.5 %) measurements of the hold-volumes with concentrated and dilute solutions of NO(3)(-) showed that the columns had all nearly the same external porosity. The result cannot be explained by the error made on the volume of the column tube either as it was measured accurately for all the columns. The residual explanation is that the interstitial velocity distribution between the packed particles depends on the chemical nature of the external surface of these particles.
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Affiliation(s)
- Fabrice Gritti
- Department of Chemistry, University of Tennessee, Knoxville, TN 37996-1600, USA
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41
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Abstract
The selectivity difference between 15 different stationary phases was measured using a large number of analytes at 2 or 3 different pH values (3, 7 and 10) with acetonitrile and methanol as the mobile phase modifiers. The packings discussed include standard C(8) and C(18) packings, packings with embedded polar groups, a phenyl packing, a pentafluoro-phenyl packing, an adamantylethyl packing and others. The major selectivity differences observed are discussed in detail. Specific effects such as pi-pi interactions on phenyl packings or hydrogen-bond interactions on phases with embedded polar groups are confirmed.
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Affiliation(s)
- Uwe D Neue
- Waters Corporation, 34 Maple Street, Milford, MA 01757, USA.
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Zhang L, Rafferty JL, Siepmann JI, Chen B, Schure MR. Chain conformation and solvent partitioning in reversed-phase liquid chromatography: Monte Carlo simulations for various water/methanol concentrations. J Chromatogr A 2006; 1126:219-31. [PMID: 16820151 DOI: 10.1016/j.chroma.2006.06.003] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2006] [Revised: 05/24/2006] [Accepted: 06/01/2006] [Indexed: 11/25/2022]
Abstract
Many structural models for the stationary phase in reversed-phase liquid chromatography (RPLC) systems have been suggested from thermodynamic and spectroscopic measurements and theoretical considerations. To provide a molecular picture of chain conformation and solvent partitioning in a typical RPLC system, a particle-based Monte Carlo simulation study is undertaken for a dimethyl octadecyl (C(18)) bonded stationary phase on a model siliceous substrate in contact with mobile phases having different methanol/water concentrations. Following upon previous simulations for gas-liquid chromatography and liquid-liquid phase equilibria, the simulations are conducted using the configurational-bias Monte Carlo method in the Gibbs ensemble and the transferable potentials for phase equilibria force field. The simulations are performed for a chain surface density of 2.9 micromol/m(2), which is a typical bonded-phase coverage for mono-functional alkyl silanes. The solvent concentrations used here are pure water, approximately 33 and 67% mole fraction of methanol and pure methanol. The simulations show that the chain conformation depends only weakly on the solvent composition. Most chains are conformationally disordered and tilt away from the substrate normal. The interfacial width increases with increasing methanol content and, for mixtures, the solvent shows an enhancement of the methanol concentration in a 10 Angstrom region outside the Gibbs dividing surface. Residual surface silanol groups are found to provide hydrogen bonding sites that lead to the formation of substrate bound water and methanol clusters, including bridging clusters that penetrate from the solvent/chain interfacial region all the way to the silica surface.
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Affiliation(s)
- Ling Zhang
- Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, MN 55455-0431, USA
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Lippa KA, Sander LC. Identification of isolated cavity features within molecular dynamics simulated chromatographic surfaces. J Chromatogr A 2006; 1128:79-89. [PMID: 16846606 DOI: 10.1016/j.chroma.2006.06.043] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2006] [Revised: 06/06/2006] [Accepted: 06/13/2006] [Indexed: 10/24/2022]
Abstract
Highly ordered morphological features were characterized for molecular dynamics simulated alkyl-modified silica models that represent chromatographic materials with enhanced shape recognition capability. Deep cavities (8-10A wide) within the alkyl chains were identified for C18 polymeric models corresponding to shape-selective RPLC stationary phases. The all-trans conformational distal-end segments of these isolated cavities averaged over a 100 ps simulation time interval were observed to increase (up to 15 A) in models with an increase in both surface coverage and corresponding shape selectivity. Similar-structure cavities with significant alkyl chain ordered regions (>11A) were isolated from two independent C18 models (differing in bonding chemistry, density and temperature) that represent highly shape-selective materials. The size and depth of these ordered regions increased (up to 28 A) for the extended-length C30 alkyl phase models. These initial results offer a physical representation of alkyl-modified surfaces that may facilitate the identification of potential molecular features that may be involved in the shape-selective retentive processes, as well as illustrating the potential for such computational techniques to predict the molecular recognition capabilities of novel analyte-specific sorbents.
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Affiliation(s)
- Katrice A Lippa
- Analytical Chemistry Division, Chemical Science and Technology Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899, USA.
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Gritti F, Guiochon G. Heterogeneity of the Adsorption Mechanism of Low Molecular Weight Compounds in Reversed-Phase Liquid Chromatography. Anal Chem 2006; 78:5823-34. [PMID: 16906729 DOI: 10.1021/ac060392d] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The retention mechanism in RPLC mode was investigated based on the acquisition of adsorption isotherm data by frontal analysis measurements and their modeling. This work is a review of the results of four years of adsorption data measurements. The data were acquired on a wide variety of brands of C18-silica columns (from Akzo Nobel, Bishoff, Hypersil, Merck, Phenomenex, Supelco, Vydac, and Waters) with several low molecular weight compounds such as phenol (94 g/mol), caffeine (194 g/mol), tryptophan (204 g/mol), sodium 2-naphthalenesulfonate (235 g/mol), and propranololium chloride (295 g/mol). The mobile phase was a mixture of methanol and water at variable composition. The adsorption isotherms were all convex upward (langmuirian), and the degree of heterogeneity of the adsorption system was determined from the calculation of the adsorption energy distribution using the expectation-maximization method. The adsorption isotherm parameters (number of types of adsorption sites, surface concentration of each type of site, and difference between the adsorption energies E(i) - E(j) on sites i and j), obtained from the mathematical fit of the adsorption data to the appropriate multi-Langmuir adsorption isotherm model, were analyzed and compared. The results allow the drawing of general conclusions regarding the relationships between the size of the analyte and the adsorption properties (saturation capacities, adsorption energies) characterizing the retention mechanism in RPLC mode for neutral, anionic, and cationic compounds.
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Affiliation(s)
- Fabrice Gritti
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996-1600, USA
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Gritti F, Guiochon G. Adsorption mechanism in reversed-phase liquid chromatography. J Chromatogr A 2006; 1115:142-63. [PMID: 16580678 DOI: 10.1016/j.chroma.2006.02.095] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2006] [Revised: 02/21/2006] [Accepted: 02/28/2006] [Indexed: 11/22/2022]
Abstract
The effect of the bonding density of the octadecyl chains onto the same silica on the adsorption and retention properties of low molecular weight compounds (phenol, caffeine, and sodium 2-naphthalene sulfonate) was investigated. The same mobile phase (methanol:water, 20:80, v/v) and temperature (T = 298 K) were applied and two duplicate columns (A and B) from each batch of packing material (neat silica, simply endcapped or C1 phase, 0.42, 1.01, 2.03, and 3.15 micromol/m2 of C18 alkyl chains) were tested. Adsorption data of the three compounds were acquired by frontal analysis (FA) and the adsorption energy distributions (AEDs) were calculated using the expectation-maximization method. Results confirmed earlier findings in linear chromatography of a retention maximum at an intermediate bonding density. From a general point of view, the saturation capacity of the adsorbent tends to decrease with increasing bonding density, due to the vanishing space intercalated between the C18 bonded chains and to the decrease of the specific surface area of the stationary phase. The equilibrium constants are maximum for an intermediary bonding density (approximately 2 micromol/m2). An enthalpy-entropy compensation was found for the thermodynamic parameters of the isotherm data. Weak equilibrium constants (small deltaH) and high saturation capacities (large deltaS) were observed at low bonding densities, higher equilibrium constants and lower saturation capacities at high bonding densities, the combinations leading to similar apparent retention in RPLC. The use of a low surface coverage column is recommended for preparative purposes.
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Affiliation(s)
- Fabrice Gritti
- Department of Chemistry, University of Tennessee, Knoxville, TN 37996-1600, USA
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