STRATEGIES FOR IMPROVING ELECTROPHORESIS DATA FROM THE COULTER DELSA

Different approaches to the determination of electrophoretic mobilitie s of colloids with the Coulter DELSA electrophoresis instrument are co mpared. The best procedure was to collect data near both walls of the cell and in the center of the sample chamber. The data are fitted to t he Komagata equation for electro-osmotic flow to give the mobility and the electro-osmotic velocity near the cell wall. The micrometer readi ng corresponding to the cell center was considered to be an unknown pa rameter which was obtained by fitting the parabola. This approach comp ensated for errors in determining the position of the cell walls. It w as shown that information about mobility distributions is more reliabl e for data collected near the center of the sample chamber. Measuremen ts were made successfully at temperatures up to 50-degrees-C. However, the cell position shifted with heating, so measurements made at the s tationary level determined at room temperature were incorrect.