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UBC Theses and Dissertations

Dynamic complexation of solutes in capillary electrophoresis Bowser, Michael T.


A general theory that describes analyte migration behavior in chromatography, electrophoresis, and ultracentrifugation is described. The theory accounts for multiple stoichiometry and multiple additive interactions through the use of individual capacity factors. The unified separation theory includes a general expression for resolution which shows that the resolution of a pair of analytes is linearly related to the ratio of the linear velocities of the two analytes. A CE separation with the presence of both 1:1 and 1:2 stoichiometry analyte-additive interactions is described using the general separation theory. The effect of the higher order interactions on the mobility of the analyte and methods for detecting deviations from the 1:1 model are discussed. Multivariate binding isotherms are used to describe the effect of multiple equilibria on analyte mobility. The effect of secondary interactions on the shapes of these curves is determined. The general theory is especially useful in describing hybrid techniques such as capillary electrochromatography. The statistical methods for estimating equilibrium constants from binding experiments are compared using Monte Carlo analyses. Simulated experiments with realistic error assumptions are used to compare the accuracy and precision of the nonlinear regression to the three linear plotting methods. The effect of the additive concentration range and the maximum response range was demonstrated. It was shown that binding constants estimated using nonlinear regression were generally more accurate and more precise than constants estimated using one of the linear transformations. The effect of experimental conditions on the precision of the binding constant estimates was shown to be related to the curvature in the binding isotherm. The solvent can have an important effect on analyte-additive interactions in CE. An assay for an oligomeric porphyrin anti-cancer drug was used as an example of nonaqueous CE separations. It was shown that the dipolar interaction between the porphyrins and a nonionic polyether surfactant (brij 35) could be used to improve separation selectivity. A group of monomeric porphyrin acids was studied to gain insight into the mechanism of the brij 35- porphyrin interaction in nonaqueous buffers. It was proposed that brij 35 interacts with the carboxyl groups on the porphyrins through dipolar interactions. It was also suggested that the orientation of porphyrin acids in the electric field might have an effect on their mobilities.

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