Surfactants such as didodecyldimethyl ammonium bromide (DDAB) and 1,2-dilauroyl-sn-phosphatidylcholine (DLPC) form bilayers at the walls of bare silica capillaries. Once formed, these bilayers are stable in the absence of surfactant in the buffer. DDAB provides a cationic bilayer coating which yields a strong reversed EOF and is effective for separation of cationic proteins. DLPC provides a zwitterionic bilayer coating which is effective for both cationic and anionic proteins. The electroosmotic flow (EOF) is strongly suppressed in DLPC-coated capillaries, thus low mobility proteins are slow to elute, and so the coating is favored for separation of high mobility proteins.
