Novel Switchable Stationary Phase Methods For Supercritical Fluid Chromatography

Nai, Emmanuel Anyetei

Novel Switchable Stationary Phase Methods For Supercritical Fluid Chromatography

dc.contributor.advisor	Thurbide, Kevin
dc.contributor.author	Nai, Emmanuel Anyetei
dc.contributor.committeemember	Kimura-Hara, Susana
dc.contributor.committeemember	Thangadurai, Venkataraman
dc.contributor.committeemember	Shi, Yujun
dc.contributor.committeemember	Lai, Edward
dc.date	2024-11
dc.date.accessioned	2024-09-20T18:49:46Z
dc.date.available	2024-09-20T18:49:46Z
dc.date.issued	2024-09-19
dc.description.abstract	In 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.
dc.identifier.citation	Nai, E. A. (2024). Novel switchable stationary phase methods for supercritical fluid chromatography (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.
dc.identifier.uri	https://hdl.handle.net/1880/119829
dc.language.iso	en
dc.publisher.faculty	Graduate Studies
dc.publisher.institution	University of Calgary
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.
dc.subject	Supercritical Fluid Chromatography
dc.subject	Water Stationary Phase
dc.subject	pH Switchable Stationary Phase
dc.subject.classification	Chemistry--Analytical
dc.title	Novel Switchable Stationary Phase Methods For Supercritical Fluid Chromatography
dc.type	doctoral thesis
thesis.degree.discipline	Chemistry
thesis.degree.grantor	University of Calgary
thesis.degree.name	Doctor of Philosophy (PhD)
ucalgary.thesis.accesssetbystudent	I do not require a thesis withhold – my thesis will have open access and can be viewed and downloaded publicly as soon as possible.