Type of Document	Dissertation
Author	Tate, Peter Anthony
URN	etd-04122005-182202
Title	Part I: Isocratic and Gradient Elution Reversed-Phase Liquid Chromatography for the Estimation of the Hydrophobicity Parameter Log K’W: Applications to Newer Generation Stationary Phases. Part II: Planar Electrochromatographic Instrumental Design and Results.
Degree	Doctor of Philosophy
Department	Chemistry and Biochemistry, Department of
Advisory Committee	Advisor Name Title John G. Dorsey Committee Chair Alan G. Marshall Committee Member J. Joseph Cronin Committee Member Oliver Steinbock Committee Member William T. Cooper Committee Member
Keywords	Reversed-Phase Liquid Chromatography Thin Layer Chromatography Hydrophobicity Chromatographic Theory Planar Electrochromatography Electroosmosis
Date of Defense	2005-04-11
Availability	unrestricted
Abstract The first half of this dissertation (Chapters 1-3) will discuss reversed-phase liquid chromatographic (RPLC) estimations of hydrophobicity. The RPLC retention values in purely aqueous mobile phases are used as measures of hydrophobicity. Unfortunately the accepted way of deriving these estimations is inaccurate. These values are normally obtained by performing isocratic chromatography through a limited range of mobile phase modifier concentrations (somewhere between 30%-70% modifier) and using the linear relationship between the logarithm of retention and modifier concentration to extrapolate a retention value for a purely aqueous mobile phase (log k’w). This linear relationship breaks down at low concentrations of modifier resulting in extrapolated values not representative of the actual chromatographic values. We have investigated newer types of RPLC columns using polar-embedded and polar-endcapped stationary phases for their ability to produce a more linear relationship throughout the range of modifier concentrations, therefore reducing error from extrapolation procedures. This work includes comparisons to other chromatographic retention modeling equations, as well as using gradient RPLC to obtain these estimations of hydrophobicity. The second half of this dissertation (Chapters 4-7) describes the development of instrumentation for planar electrochromatography (PEC). PEC is a new methodology for thin layer chromatography (TLC) where the solvent is pushed through a TLC plate by electroosmotic flow (EOF) rather than capillary action. This allows faster flow rates and better-predicted chromatographic figures of merit. Initial instrument design had major problems due to Joule heating, solvent evaporation and a vertical format. Instrumentation has evolved with horizontal formats, closed systems to eliminate solvent evaporation, and external pressurization for correct voltage profiles across a TLC plate. We now understand the reasons for early instrumental hindrances and have continually redesigned the instrument to combat each obstacle. The latest design has achieved the predicted linear voltage drop of the applied field and hence, consistent EOF. Further proving the efficacy of this technique, initial studies with a fluorescent marker visually prove the correct solvent flow profiles determined with our voltage readers.
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