Strategies for improving electrophoresis data from the Coulter DELSA

Different approaches to the determination of electrophoretic mobilities of colloids with the Coulter DELSA electrophoresis instrument are compared. 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 the Komagata equation for electro-osmotic flow to give the mobility and the electro-osmotic velocity near the cell wall. The micrometer reading corresponding to the cell center was considered to be an unknown parameter which was obtained by fitting the parabola. This approach compensated for errors in determining the position of the cell walls.It was shown that information about mobility distributions is more reliable for data collected near the center of the sample chamber. Measurements were made successfully at temperatures up to 50°C. However, the cell position shifted with heating, so measurements made at the stationary level determined at room temperature were incorrect.