FACTORS AFFECTING THE COMPOSITION OF THE BONDED STATIONARY PHASE IN LIQUID CHROMATOGRAPHY.

Persistent Link:
http://hdl.handle.net/10150/143046
Title:
FACTORS AFFECTING THE COMPOSITION OF THE BONDED STATIONARY PHASE IN LIQUID CHROMATOGRAPHY.
Author:
ZWIER, THOMAS ALAN.
Issue Date:
1981
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The stationary phase on chemically modified supports for liquid chromatography is described as a mixture of the surface-bonded species, the active unmodified surface, and associated mobile phase components. Each of these three factors in stationary phase formation is examined and improved qualitative and quantitative descriptions of the stationary phase are provided. The role of the active unmodified surface was examined by synthesizing a carbon support and chemically modifying it with octyl groups. The modified carbon had a greater affinity for lipophilic probes than an octyl silica. The lipophilicity of the octyl carbon was attenuated relative to the unmodified carbon. The physical state of the bonded species in C(,18) and C(,8) packings was studied using carbon-13 NMR. Peak widths of 2-7 ppm indicated a liquid-like nature but with restricted movement. Only the 7 to 10 carbons in a C(,18) chain farthest from the surface were sufficiently motile to produce a signal. The C(,8) packing showed more rigid chains with only the top 3 or 4 carbons responding. The liquid-like nature of a C(,18) chain increased with the lipophilic character of the solvent, indicating that solvation of the bonded species was directly related to the mobile phase composition. Changes in temperature had little effect on the physical state of the bonded species, but chromatographic enthalpy measurements showed that changes in stationary phase composition could be induced by warming the column and held by subsequent cooling. Quantitative measurements of stationary phase compositions revealed linear distribution isotherms for the organic modifiers methanol, acetonitrile, and tetrahydrofuran. Chromatographic selectivities for homologous n-alkanols correlated linearly with organic modifier concentrations in the stationary phases. The stationary phase volumes, which increased with increasing modifier concentrations, are interpreted as constituting filling of the pores in the support with a gradient of modifier enrichment toward the surface.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Liquid chromatography; Carbon compounds; Surface chemistry
Degree Name:
Ph.D.
Degree Level:
Doctoral
Degree Program:
Chemistry; Graduate College
Degree Grantor:
University of Arizona

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleFACTORS AFFECTING THE COMPOSITION OF THE BONDED STATIONARY PHASE IN LIQUID CHROMATOGRAPHY.en_US
dc.creatorZWIER, THOMAS ALAN.en_US
dc.contributor.authorZWIER, THOMAS ALAN.en_US
dc.date.issued1981en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe stationary phase on chemically modified supports for liquid chromatography is described as a mixture of the surface-bonded species, the active unmodified surface, and associated mobile phase components. Each of these three factors in stationary phase formation is examined and improved qualitative and quantitative descriptions of the stationary phase are provided. The role of the active unmodified surface was examined by synthesizing a carbon support and chemically modifying it with octyl groups. The modified carbon had a greater affinity for lipophilic probes than an octyl silica. The lipophilicity of the octyl carbon was attenuated relative to the unmodified carbon. The physical state of the bonded species in C(,18) and C(,8) packings was studied using carbon-13 NMR. Peak widths of 2-7 ppm indicated a liquid-like nature but with restricted movement. Only the 7 to 10 carbons in a C(,18) chain farthest from the surface were sufficiently motile to produce a signal. The C(,8) packing showed more rigid chains with only the top 3 or 4 carbons responding. The liquid-like nature of a C(,18) chain increased with the lipophilic character of the solvent, indicating that solvation of the bonded species was directly related to the mobile phase composition. Changes in temperature had little effect on the physical state of the bonded species, but chromatographic enthalpy measurements showed that changes in stationary phase composition could be induced by warming the column and held by subsequent cooling. Quantitative measurements of stationary phase compositions revealed linear distribution isotherms for the organic modifiers methanol, acetonitrile, and tetrahydrofuran. Chromatographic selectivities for homologous n-alkanols correlated linearly with organic modifier concentrations in the stationary phases. The stationary phase volumes, which increased with increasing modifier concentrations, are interpreted as constituting filling of the pores in the support with a gradient of modifier enrichment toward the surface.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectLiquid chromatographyen_US
dc.subjectCarbon compoundsen_US
dc.subjectSurface chemistryen_US
thesis.degree.namePh.D.en_US
thesis.degree.levelDoctoralen_US
thesis.degree.disciplineChemistryen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.identifier.proquest8304729en_US
dc.identifier.oclc683271987en_US
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