Year of Award

2010

Document Type

Dissertation

Degree Type

Doctor of Philosophy (PhD)

Degree Name

Chemistry

Department or School/College

Department of Chemistry and Biochemistry

Committee Chair

Christopher Palmer

Commitee Members

Mike DeGrandpre, Edward Rosenberg, Sandy Ross, Steven Lodmell

Keywords

capillary electrophoresis, fused silica capillaries, nerve agent, polymer coating, sensor

Abstract

Fused silica capillaries have become a major tool for many applications in analytical chemistry. These capillaries are physically robust, permit gasses or solutions to be introduced and pumped through with relative ease, and due to their small dimensions allow fast mass transfer to and from the capillary walls as well as miniaturization of analytical systems. This dissertation describes two projects that utilize modification of fused silica capillary surfaces for specific analytical applications.

The first project is to reverse the charge on the capillary surface by immobilization of cationic polymers, thus creating a very stable coating for application to CE separations. The chemistry proposed by Rosenberg et al. for the covalent attachment of amine polymers to silica is adapted to the modification of fused silica capillaries for CE applications. PEI and PAA were covalently bonded to the interior surface of fused silica capillaries utilizing 3-chloro- propyltrichlorosilane (CPTCS) or 3-glycidoxypropyl-trimethoxysilane (GPTMS) to anchor the polymers to the surface. The surface-bound polymers were subsequently quaternized using methyl iodide (MeI). The resulting modified capillaries were studied using CE, and were shown to provide reproducible, stable, and robust anodic EOF throughout the pH range of 2 - 10. Surface modifications utilizing CPTCS could be rinsed with up to 6 M HCl or 1 M NaOH without significant loss of surface modifier. The utility of the modified capillaries for the separation of simple anions and cations was demonstrated.

The second project involves modifying a fiber optic capillary to detect nerve agents by immobilizing fluorescent labeled acetylcholinesterase (AChE) to the surface and using evanescent waves to monitor the enzyme activity. The hypotheses for the chemical sensor are that the improved enzyme activity of a recombinant AChE, along with the improved sensing capabilities of the fiber optic capillaries, will improve detection limits and sensor robustness. The capillary based sensor is shown to work for the detection of warfare agent surrogates by following changes in fluorescein absorbance, but background emission from the capillary prevented potentially more sensitive detection by following changes in fluorescein fluorescence.

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© Copyright 2010 Jesse James Stine