System peaks of cyclodextrins in capillary electrophoresis

Using a running buffer containing cyclodextrins (CDs) and 2-[N-cyclohexylam ino]-ethanesulfonic acid (CHES), positive system peaks were observed in the analysis of a ganglioside mixture by CE-UV, These system peaks were relate d to CDs in the running buffer because these peaks were also detected when a plug of solution devoid of CDs but having the same CHES concentration and pH as the running buffer was injected, Neutral CDs were separated owing to the formation of inclusion complexes with the anionic CHES ion. One possib le explanation for the positive system peaks is that the anionic CD-CHES in clusion complex Is displaced by co-ions with higher UV absorptivity.