Type of Document Dissertation Author Usher, Karyn Mae Author's Email Address firstname.lastname@example.org URN etd-07082005-191220 Title Formation of a Particle-Fixed Monolith and an Investigation of Intracolumn Broadening in Liquid Chromatography Degree Doctor of Philosophy Department Chemistry and Biochemistry, Department of Advisory Committee
Advisor Name Title John G. Dorsey Committee Member Mark A. Riley Committee Member Susan E. Latturner Committee Member William T. Cooper Committee Member Keywords
- Capillary Electrochromatography
- Band Broadening
- Liquid Chromatography
Date of Defense 2005-07-07 Availability unrestricted AbstractThe stationary phase used in a chromatography column and the way it is packed inside the column greatly influences the separation in a chromatographic system. In capillary electrochromatography, the column plays an even more vital role than in high performance liquid chromatography, since it acts as both the separation element and where the flow is generated. Traditional capillary electrochromatography columns have problems stemming from use of frits, which cause bubble formation and band broadening. They also suffer from movement of the charged stationary phase particles during separation, leading to spaces in the packed bed known as gapping. It has been suggested that these problems may be overcome by the use of monoliths for capillary electrochromatography experiments. The first part of this dissertation describes the formation of a particle fixed monolith, which uses no frit during the separation, and can be made by adding a few easy steps to the traditional method for making a capillary electrochromatography column by slurry packing.
The second part of the dissertation discusses band broadening in high performance liquid chromatography. High performance liquid chromatography is used in many branches of science and it represents an approximately two billion dollar a year industry. Although this technique has been around for over 30 years, there are still many unanswered questions regarding the fundamental processes that contribute to band broadening in the chromatographic system.
In 1956, van Deemter described the band broadening in a chromatographic system with equation . The A term represents eddy diffusion, the B term represents molecular diffusion, the C term represents resistance to mass transfer and u is the mobile phase velocity. Other equations have since been introduced to model efficiency data, and these include the equations of Giddings, Huber and Hulsman, Horvath and Lin, and Knox. This creates a plight for chromatographers who then need to decide what equation to use since all the equations are based on different theories. All the equations offer similar fits, so it may not seem particularly important which equation one uses. However, if the efficiency data is to be used to try and improve column technology, then the importance of the equation that is chosen becomes evident.
H = A + B/u + Cu 
By choosing solutes that experience only one or two known types of broadening, it is possible to chromatographically isolate the contributions to band broadening. Such a chromatographic isolation of the band broadening contributions is theoretically better than previously used methods because the experiments would be performed under normal chromatographic conditions. A series of experiments using uracil, benzene, toluene, ethylbenzene, propylbenzene and butylbenzene has been completed, and this data has given additional information about these processes. In the final portion of the dissertation, the four equations mentioned above were used to model plate height data, and the resultant fits were compared. The information presented in this study is useful for chromatographers who need to choose one of the equations to model their data.
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