Micellar electrokinetic chromatography is a widely used analytical separation technique. To achieve separation, it uses interaction of analytes with charged micelles present in the background electrolyte (BGE). Not only the mobilities of analytes but also mobilities of small inorganic ions, usually contained in the BGE, are influenced by the presence of micelles. Description of interactions between inorganic ions and micelles is needed for better understanding electrophoretic separations in BGEs containing micelles. Determination of physico-chemical constants (interaction constants, mobilities of complexes) by capillary electrophoresis is based on accurate determination of effective mobilities. For this reason, accurate determination of mobility of electroosmotic flow (EOF) is also necessary but complicated in BGEs containing charged micelles, because the neutral EOF marker can be mobilized by interaction with the micelles. In this work a new two-detector method for determination of effective mobility in interacting BGEs was proposed. In this method the analyte is placed in the BGE containing charged micelles, while the marker zone is in the BGE without micelles and so the possible interaction is avoided. Using this method, dependence of sodium cation mobility on concentration of lithium...