Patent ID: 7169278

Claim:
A free-flow electrophoresis (FFE) apparatus for separating particles with a separation chamber adapted for the flow-through of a separation medium and defined by a floor, a cover and spacers to maintain the floor and the cover at a distance from each other, the FFE apparatus further comprising: (a) a dosage pump for conveying a separation medium that enters the separation chamber by way of medium feed lines and that leaves said separation chamber by way of outlets; (b) an anode and a cathode located at a distance from each other for applying an electric field in the separation medium that flows between these two electrodes; (c) sample injection points for adding a mixture of particles to be separated in the separation medium; (d) fractionation points for removing the particles in the separation medium that have been separated by FFE; and (e) selectively defined charge labels for coupling with particles to be separated and for generating charge-modified particles that have a different migratory behavior in FFE due to their selectively modified net surface charge than non-charge-modified particles; wherein the FFE apparatus further comprises two focusing areas arranged in the vicinity of the anode or cathode and between the separation medium and these two electrodes, whereby said focusing areas consist of a focusing buffer that is fed to the focusing areas via separate feed lines, the focusing buffer flowing in the same direction like the separation medium, but having much higher electrical conductivity than the separation medium such that a fluidic boundary is created between the separation medium and the focusing buffer in an area between the anode and cathode, whereby charge-modified particles are focused within the separation medium and close to these fluidic boundaries at the border of the focusing areas.