Electrophoretic Focusing: An Alternative to Capillary Electrophoresis

Electrophoretic focusing is a new separation method intended to achieve high resolution within very short sample residence times because one fraction is separated at a time instead of all fractions at once, a characteristic of capillary and other zonal separation systems. Sample is inserted within a continuous buffer flow steam as a thin lamina and is collected in a single port at the exit end of the chamber. Applying an electric field transverse to the incoming sample and opposing this field with a carefully configured buffer flow a sample constituent can be selected and focused into the collection port for subsequent analysis. Monotonically changing either electric field or buffer cross-flow will yield a scan of the entire sample population. Stopping the scan increases the collection time for minor constituents. Extraneous sample is deflected out of the separation chamber through porous walls while the selected sample is focused in the center-plane of the separation chamber and collected without contact or interaction with the walls. Adverse effects of electroosmosis and other spurious flows are minimal. The design limits Joule heating and electrohydrodynamics during the electrophoresis process and thus should achieve a high resolution of separation in an analytical or preparative mode.