Head column field-amplified stacking from the flow: Stabilization of the sample plug position by using backpressure

Head column-field amplified sample stacking (HC-FASS) is one of the most po werful concentration techniques in capillary electrophoresis. In the presen t work we demonstrate that a laboratory-designed pneumatic sampler not only enables us to easily perform HC-FASS from stagnant sample solutions but al so permits us to carry out HC-FASS from sample stream, which creates an opp ortunity to lower the detection limit of analytes further. The influence of stacking time in case of the flowing sample on peak efficiencies and resol ution is discussed. It is demonstrated that the sample plug length can be k ept constant by monitoring the current in the capillary, which controls a f eedback system based on backpressure at the capillary outlet.