Graduate Studies
Novel Switchable Stationary Phase Methods For Supercritical Fluid Chromatography
Abstract
dc:description.abstractIn the first part of this thesis, a supercritical fluid chromatography-flame ionization detection (SFC-FID) system employing a modified water stationary phase was investigated for the analysis of organic bases. The method uses a stainless steel capillary column coated with water containing NH4OH, which was also used to hydrate the system. In this way, the pH of the water stationary phase can be effectively altered to help control the ionization of organic base analytes and greatly improve their peak shape and elution properties, contrary to the poor results observed on a pure water stationary phase for the basic analytes, which occurs due to their charged state in the otherwise naturally acidic CO2/water phase interface. Overall, the NH4OH modified system showed good performance over a wide range of column temperatures and CO2 pressures tested. The results show that this approach can be useful for the elution of organic bases over a wide range of pKa values (tested up to 10.4). In the next part, a novel, externally pH switchable water stationary phase for use in SFC was investigated. By adding NH4OH to the water coating and system hydration, changes in CO2 pressure and temperature allow a wide range of stationary phase pH conditions (~3-9) to be achieved. Through pressure/temperature manipulation or adding/removing NH4OH to the system two operating modes, basic and acidic, respectively could be achieved which allowed retention control of ionizable analytes. In the final part, a dual column system comprised of a pH switchable water stationary phase column and a conventional non-polar capillary column was explored for use in SFC. By removing or adding NH4OH to the system hydration source, the water stationary phase pH can be rapidly switched between acidic (pH~3) and basic (pH~9) in seconds, while the operating character of the conventional column is unchanged. This switch modulates the velocity of ionizable analytes about 20-fold in the system, whereas non-ionizable analytes are not affected. In this way, the retention time of acids and/or bases can be reproducibly altered (<1% RSD; n=3) in SFC separations. As a result, analyte selectivity and resolution can be readily controlled during analyses.
Degree
thesis:*- Name thesis:degree_name
- Doctor of Philosophy (PhD)
- Discipline thesis:degree_discipline
- Chemistry
- Grantor dc:publisher.institution
- Graduate Studies
- Year dc:date.issued
- 2024
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Nai, Emmanuel Anyetei
- Advisor dc:contributor.advisor
-
- Thurbide, Kevin
- Committee members dc:contributor.committeemember
-
- Kimura-Hara, Susana
- Thangadurai, Venkataraman
- Shi, Yujun
- Lai, Edward
Subjects
dc:subject × 3Rights
dc:rights- Statement dc:rights
-
- University of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.
- Language dc:language.iso
- en
Identifiers
dc:identifier.*- OAI identifier oai:identifier
- oai:ucalgary.scholaris.ca:1880/119829