Performance of a physically adsorbed high-molecular-mass polyethyleneimine layer as coating for the separation of basic proteins and peptides by capillary electrophoresis

A simple method for the preparation of a polyethyleneimine (PEI) coating on the inner surface of fused-silica capillaries for capillary electrophoresis (CE) is reported. The PEI layer can be coated on the silica surface by just flushing the capillary with a solution containing high-molecular-mass PEI. The physically adsorbed layer appears to be very stable and can be used in a pH range of 3-11. In comparison to described methods to fabricate an immobilized PEI layer, the proposed method does not require an immobilization step, is simple and the preparation time of the coating is less than two hours. Good reproducibilities of migration times of basic proteins and peptides were obtained on the same PEI-coated capillary as well as on different PEI-coated capillaries. For basic proteins efficiencies ranging from 300 000-500 000 plates per meter were normally found.