Date of Award

Fall 2014

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Chemistry

First Advisor

Mary J. Wirth

Committee Member 1

Chittaranjan Das

Committee Member 2

Garth Simpson

Abstract

Capillaries packed with a silica colloidal crystal (SCC) of 470 nm nonporous particles have recently been shown to offer significant improvements in the peak width, resolution, and speed of protein analysis due to the reduction of the A and C term broadening contributions of the Van Deemter equation. While protein separations using this technology have shown vast improvements, small molecules remain largely unexplored. As the SCC allows for an approximately diffusion limited system, extremely high plate numbers are expected for small molecule separations. The research presented herein studies the feasibility of pressure-driven small molecule separation using SCCs and commercial instrumentation. Studies are performed both in capillaries and stainless steel columns.

Separating small molecules presents a unique challenge due to their size and high diffusion coefficients. For capillary SCC separations, these properties are shown here to exacerbate problems in the nano-ultra high performance liquid chromatography (UHPLC) commercial instrumentation, such as extra-column band broadening and adherence to tubing walls. While this is less of a problem for gradient separations, isocratic separations are considerably affected. Thus, the full potential of these capillary columns cannot currently be realized. Separations using UHPLC and stainless steel columns circumvent these problems. However, an unprecedented amount of broadening from longitudinal diffusion was found to limit the achievable plate heights in these columns to about 200,000 plates/m, which is on par with the latest commercially available columns. Significantly higher flow rates will need to be achieved to increase efficiency.

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