| Capillary electrophoresis (CE) is a separation technique in which charged molecules are separated from one another in an electric field. The use of organic solvents in CE offers different separation characteristics compared to purely aqueous media. However, the mechanism responsible for solvent-induced selectivity changes was not well understood. The most commonly used mobility model, the Huckel equation, does not predict the different separation characteristics observed in organic or aqueous-organic media. This model only considers the viscous drag, or hydrodynamic friction, experienced by an ion.; This thesis demonstrates that a theoretical mobility model accounting for charge-induced friction can explain solvent-induced selectivity changes in CE. The Hubbard-Onsager dielectric friction model successfully predicts the mobility behavior of organic anions and cations in methanol-water, acetonitrile-water, ethanol-water and 2-propanol-water media. As predicted by this model, the changes in ion mobility correlate with the corresponding changes in solvent viscosity (eta), dielectric constant (epsilon) and dielectric relaxation time (tau). Dielectric friction is thus used to explain the solvent-induced selectivity changes observed herein and elsewhere. This is the first report showing the importance of solvent tau on mobility in CE.; Despite its success in aqueous-organic media, the Hubbard-Onsager model does not explain mobility behavior in nonaqueous methanol-acetonitrile media. This is explained by the continuum nature of the model, whereby the different ion-solvent interactions in acetonitrile and methanol are not taken into account. Further, no evidence is seen for temperature-induced selectivity changes resulting from dielectric friction.; Consistent with a theoretical model, the ionic strength effects generally vary with ion charge (z), solvent content and temperature as a function of z/etaepsilon1/2. Departures from this trend in nonaqeuous media are attributed to ion association.; Finally, in an alternate project, polyamines are derivatized with 1-pyrenebutanoic acid succinimidyl ester (PSE) and analyzed using micellar electrokinetic chromatography with laser-induced fluorescence detection. This derivatization allows for sensitive and selective detection of the polyamines. Detection limits for PSE-labeled putrescine, cadaverine, spermidine and spermine are 2, 2, 4 and 5 nM, respectively. |
