he C4D is an electrochemical method of detection simultaneously introduced by two research groups (Fracassi da Silva and do Lago, and Zemann and co-workers). Two electrodes are positioned outside the capillary. A high-frequency signal is applied in the first electrode. The signal that pass through solution inside of the capillary go to the second electrode and is reading by electronic circuit. The current that flows through the detection cell is proportional to the conductivity of the solution inside of the capillary. Such an approach prevents the interference from the high-intensity electric field needed for the electrophoresis and allows easy removal of the capillary from the detector.