The setup consists of a high voltage source, two platinum electrodes, a photon counting system and a PEEK three-way union. The whole system is enclosed in a black box to avoid external radiation. The electrophoretic separation occurs in a fused silica capillary, the CL reagent is introduced into the system by gravity. The separation capillary is partially introduced into the reaction capillary constituting an on-column coaxial flow interface. Two injection modes of the sample are possible: electrokinetic injection and injection by gravity.