Selectivity in microemulsion electrokinetic chromatography

Microemulsion electrokinetic chromatography (MEEKC) is a most promising sep aration technique providing good selectivity and high separation efficiency of anionic, cationic as well as neutral solutes. In MEEKC lipophilic organ ic solvents dispersed as tiny droplets in an aqueous buffer by the use of s urfactants provide a pseudo-stationary phase to which the solutes may have an affinity either to the surface or they may even partition into the dropl ets. When the droplets are charged, typically negatively, they will migrate opposite to the electroosmotic flow and hence separation of neutral solute s may take place. In the present paper focus has been set on how to change selectivity in MEEKC. Changes in the nature of surfactant as well as in pH have been shown to be powerful tools in changing the selectivity. The type of lipophilic organic phase is of less importance for the separation of fai rly lipophilic solutes. Also changes in the temperature surrounding the cap illary may alter the selectivity. (C) 2000 Elsevier Science B.V. All rights reserved.