| To further current biochemical knowledge, cellular interactions must be studied as they occur. To do this, analytical techniques must be fast, sensitive, and selective. As yet, no techniques satisfy all of these requirements, and measures must be taken in many areas of research to achieve these goals.; One of the significant issues involved in this type of analysis is the mechanism of analyte sampling. Sample removal is generally achieved by either pressure or electrophoretic flow mechanisms. The large pressures required to move fluid in capillary dimensions would destroy the system being sampled. Electrophoretic flow (EOF) allows the movement of chemicals from the source with minimal perturbations. Coupled to microdevices, EOF can provide real time sampling with low mass sensitivity, fast analysis, and low detection limits.; Electrophoretic flow has drawbacks because the reproducibility of retention times in capillary electrophoresis (CE) is poor due to analyte adsorption at the walls. Electrophroesis requires a charged surface to generate flow, but that surface also attracts charged biological molecules. Loss of sample and peak tailing result from analyte adsorption. A mechanism to dynamically alter flow rates or alter adsorption could improve reproducibility in CE.; In this research dissertation, a combined approach to these issues has been taken. First, a mechanism for flow monitoring using charged markers was developed to speed analysis in low flow situations. Second, the capillary wall was modified by adding titanium dioxide. Titanium dioxide has similar chemistry to silica but coated titanium dioxide surfaces are more pH stable than coated silica. The improved pH stability allows for more useful coatings. To dynamically control flow rates, external voltage control (EVC) of CE is applied. A discussion of the mechanism of flow control in EVC is investigated. Taking information from experiment and the literature, theory was compare to the experimental data; no good match of literature data or correction facts to theory was found. While the influence that is responsible for this discrepancy is still unclear, directions for future research are suggested. |
