Lippa, K.
, Sander, L.
and Mountain, R.
(2005),
Molecular Dynamics Simulations of Alkylsilane Stationary Phase Order and Disorder. 1. Effects of Surface Coverage and Bonding Chemistry, Analytical Chemistry
(Accessed January 17, 2025)
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Molecular Dynamics Simulations of Alkylsilane Stationary Phase Order and Disorder. 1. Effects of Surface Coverage and Bonding Chemistry
Published
Author(s)
, ,
Abstract
Shape-selective polymeric alkylsilane stationary phases are routinely employed over the more common monomeric phases in reversed-phase liquid chromatography (RPLC) to improve the separation of geometric isomers of shape-constrained solutes. We have investigated the molecular dynamics of chromatographic models that represent both monomeric and polymeric stationary phases with alkylsilane surface coverages and bonding chemistries typical of actual materials in an effort to elucidate the molecular-level structural features that control shape-selective separations. The structural characterization of these models are consistent with previous experimental observations of alkyl chain order and disorder: 1) alkyl chain order increases with increased surface coverage; and 2) monomeric and polymeric phases with similar surface coverages yield similar alkyl chain order (although subtle differences exist). In addition, a significant portion of the alkyl chain proximal to the silica surface is disordered (primarily gauche conformations) and the distal end is most ordered. Models that represent shape-selective RPLC phases possess a significant region of distal-end chain order with primarily trans dihedral angle conformations. This is consistent with the view that the alkyl chains comprising polymeric stationary phases contain a series of well-defined and rigid slots in which shape-constrained solutes can penetrate and hence be selectively retained.Citation
Analytical Chemistry
Volume
77 No 24
Pub Type
Journals
Keywords
alkylsilanes, C18, molecular dynamic simulation, monometric, polymeric, reversed-phase liquid chromatography, RPLC, shape selectivity
Citation
Issues
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Created December 1, 2005, Updated February 17, 2017