The retention/migration behavior of insulin and five synthetic insulin analogues in CZE, MEKC and MEEKC employing seven different detergents within the latter two techniques has been investigated. Substantial changes in separation selectivity in MEKC could be observed for several insulins when moving from SDS to cholate-based micellar systems. Customized separations could be achieved by using mixtures of SDS and deoxycholate. A similar effect could be observed in MEEKC although the overall quality of MEEKC separations was inferior to those obtained with MEKC.