| Structure-function relationships in high-density octadecylsilane stationary phases by Raman spectroscopy. 4. Effects of neutral and basic aromatic compounds. | |
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MedLine Citation:
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PMID: 14570186 Owner: NLM Status: PubMed-not-MEDLINE |
Abstract/OtherAbstract:
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The effects of aromatic compounds (toluene, benzene, p-xylene, anisole, aniline, and pyridine), temperature, and surface grafting method (surface- or solution-polymerized) on alkyl chain rotational and conformational order in a series of high-density octadecylsilane stationary phases ranging in surface coverage from 3.09 to 6.45 micromol/m2 are examined by Raman spectroscopy. Rotational and conformational order are assessed using the intensity ratio of the antisymmetric to symmetric v(CH2) modes as well as the frequency at which the symmetric v(CH2) band is observed. Alkyl rotational and conformational order decrease with decreasing surface coverage in these aromatic compounds, which is consistent with the behavior of these materials in air and in other solvents. In addition, order of the alkyl chains is dependent on solvent hydrophobicity, hydrogen-bonding ability, and basicity. The most hydrophobic compounds impart disorder to the stationary phase; the hydrogen-bonding aromatics increase the rotational order of homogeneously distributed, high-surface-coverage materials; and basic aromatic compounds increase the conformational order of high- and low-coverage materials as the basic compounds undergo silanophilic interactions with exposed surface silanols. From these observations, molecular pictures of the chromatographic interface that display interactions between the alkyl chains and these aromatic compounds are proposed. |
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Authors:
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Christopher J Orendorff; Michael W Ducey; Jeanne E Pemberton; Lane C Sander |
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Publication Detail:
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Type: Journal Article |
Journal Detail:
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Title: Analytical chemistry Volume: 75 ISSN: 0003-2700 ISO Abbreviation: Anal. Chem. Publication Date: 2003 Jul |
Date Detail:
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Created Date: 2003-10-22 Completed Date: 2004-04-16 Revised Date: 2004-06-21 |
Medline Journal Info:
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Nlm Unique ID: 0370536 Medline TA: Anal Chem Country: United States |
Other Details:
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Languages: eng Pagination: 3369-75 Citation Subset: - |
Affiliation:
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University of Arizona, Department of Chemistry, Tucson, Arizona 85721, USA. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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