Investigation of the effects of cyclodextrins and organic solvents on the separation of cationic surfactants in capillary electrophoresis

The use of α- and β-cyclodextrin (CD) to understand and to improve the separation of a series of cationic surfactants, homologues of alkylbenzyldimethyl ammonium compounds (ABDACs) with an alkyl chain of varying length (C10–C18), in capillary electrophoresis (CE) is reported for the first time. Similar to the effects of organic solvents, the presence of α- or β-CD in the running buffer was found to reduce peak tailing/loss for the longer-chain ABDACs. Based on fluorescence measurements, it was found that formation of host–guest complexes occurred between α- or β-CD and various ABDACs, with the likelihood that the hydrophobic alkyl chain including into the CD cavity and the positively charged ammonium group remaining outside the cavity. The effects of α- or β-CD can be interpreted in terms of a shift away from the formation of (1) micelles in the buffer system and (2) surfactant aggregates at the fused-silica capillary walls, as a result of the formation of inclusion complexes between α- or β-CD and ABDACs.