Pseudo-homogeneous micelle extraction of ion-associates formed between tetrabutylammonium ion and some aromatic sulfonate ions into nonionic surfactant micelle studied through the mobility measurements in capillary zone electrophoresis

Ion-association extraction of some aromatic sulfonate ions including alkylbenzene sulfonates with tetrabutylammonium ion (TBA+) into nonionic surfactant micelle has been investigated through the changes in the electrophoretic mobility. Nonionic surfactants of Brij 35 and Brij 58 were used as micelle substrates to which the ion-associates formed could distribute. The electrophoretic mobility of the aromatic sulfonate ions was measured by capillary zone electrophoresis in the presence of TBA+ and/or the nonionic surfactant to determine ion-association constants (Kass), binding constants of the anions to the nonionic surfactant micelle (KB), and binding constants of the ion-associates to the nonionic surfactant micelle (KB,IA). Nonlinear phenomena induced with the alkyl chain moiety were observed on Kass and KB by its linear structure and the mixed micelle formation, respectively. Larger KB values were obtained with Brij 58 as micelle matrix than with Brij 35, while the differences in KB,IA were small between Brij 58 and Brij 35.