Dispersion in Capillary Electrophoresis Due to Sample Induced Modification of the Electroosmotic Flow

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ABSTRACTPROPOSAL NO.: CTS-0330604PRINCIPAL INVESTIGATORS: SANDIP GHOSALINSTITUTION: NORTHWESTERN UNIVERSITYDispersion in Capillary Electrophoresis due to sample induced modification of the Electroosmotic flow Electrophoresis is an important analytical tool in biological research, second only to the microscope. Its most familiar implementation is in "gel electrophoresis" where the sample migrates through a porous medium in a strong electric field and separates into a series of bands due to differences in the migration rates of its various components. Like a snapshot of runners on a racetrack, this pattern of bands provides a signature or fingerprint for identifying the chemical composition f the sample. If instead of having the sample migrate through the micro pores of the gel, it is injected at one end of a micro-capillary (10 to100 micron diameter), faster separation can be achieved, at a higher resolution and using a much smaller quantity of the sample, perhaps nanoliters. This technique is known as "capillary electrophoresis" (CE). If the capillaries are micro-channels etched on a glass or silicon wafer, entire biochemical protocols can be miniaturized into 'microfluidic chips'. This research is aimed at understanding how the concentration distribution of the sample evolves as it moves down the micochannel of a CE system, by using the basic equations of fluid flow and diffusion. Just as the quality of a microscope is determined by the resolving power of its optics, the figure of merit of a CE system is in the narrowness of the concentration peaks of the sample constituents. Fundamental understanding of the mechanisms of band broadening will result in the following: (1) suggest new designs to "push the envelope" on the smallness of concentrations that can be detected and subtleties in differences in molecular structure that can be resolved, (2) quantify the best achievable resolution limits, and (3) evaluate potential new designs using the predictive tools that this project seeks to provide. The broader impacts include the training of a graduate student and dissemination of results. In addition, the PI will collect and collate into an electronic "Album of Fluid Motion" images illustrating fluid flow on a micro-scale. This will be used by the PI in undergraduate and graduate level fluids classes and would also be made available to the research and educational community. This grant was funded under the NSF Math Sciences Priority Area.