Dissertation
Design considerations for dynamic field gradient focusing
Washington State University
Doctor of Philosophy (PhD), Washington State University
12/2009
DOI:
https://doi.org/10.7273/000006173
Abstract
Dynamic field gradient focusing (DFGF) utilizes an electric field gradient and an opposing hydrodynamic flow to simultaneously separate and concentrate charged analytes according their individual electrophoretic mobilities. Realization of the full potential of DFGF has been hindered by several performance bottlenecks that have led to reproducibility issues, diminished concentration factors and lower than expected resolution and peak capacity. To address the performance bottlenecks, which include voltage degradation, electrode placement, membrane structural stability, membrane concentration polarization and resistance to current through the membrane, a nonlinear, numerical simulation along with experimental results was used. It was determined that these bottlenecks were not limitations of the technique, but rather engineering issues that could be addressed and alleviated. However, two final issues, the inability to separate small molecules and the restriction of the instrument to the analysis of only negatively charged species, remained. To extend the applicability of DFGF to the analysis of low molecular weight species, a membrane-less DFGF device was developed. Without a semi-permeable membrane, the individual electrodes are located within the separation channel. Electrolysis products due to the reaction of water on the surface of the electrodes were dealt with by incorporating a high-capacity, low-conductivity buffer and an on-column degassing system. The separation of three low molecular weight dyes is shown. The ability to separate negatively and positively charged species was extended to DFGF by the construction of a voltage controller capable of operation under normal and reversed polarity fields. This allowed for the separation of negatively charged species, positively charged species, as well as, the simultaneous separation of oppositely charged species. In addition, the ability to dynamically control the electric field allowed for two oppositely charged species to be initially focused and then made to contact and ultimately switch positions within the separation channel. The elimination of the performance bottlenecks has led to the development of a reproducible and robust DFGF system. In addition, new applications for DFGF are described, extending the utility of DFGF to different areas of research.
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Details
- Title
- Design considerations for dynamic field gradient focusing
- Creators
- Jeffrey Michael Burke
- Contributors
- Cornelius F. Ivory (Chair)Su Ha (Committee Member) - Washington State University, School of Chemical Engineering and BioengineeringRaymond Reeves (Committee Member) - Washington State University, School of Molecular BiosciencesHerbert H. Hill Jr. (Committee Member) - Washington State University, Department of Chemistry
- Awarding Institution
- Washington State University
- Academic Unit
- School of Chemical Engineering and Bioengineering
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 176
- Identifiers
- 99901055120301842
- Language
- English
- Resource Type
- Dissertation