Coadsorption of mixed anionic and cationic surfactants in reversed-phase high performance liquid chromatography

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The combined effects of mixed alkylsulfonate and alkylamine surfactants on the liquid chromatographic retention times of aniline, phenylethylamine, benezene- sulfonic acid, and chromotropic acid are described by a quantitative thermodynamic model that assumes electrostatic interaction of charged solutes with the anionic and cationic surfactants in the adsorbed phase. The results of this study indicate (1) the synergistic effect of coadsorption (the total amount of the mixed surfactants adsorbed on the surface is higher than the amount of either individual surfactant adsorbed on the surface at the same total bulk concentration); (2) the competitive nature of the coadsorption processes (at any given bulk liquid concentration of one surfactant, the surface mole fraction of that surfactant decreases with increasing concentration of the other surfactant); and (3) the possibility of using liquid chromatography as a tool for the measurement of adsorption free energy of surfactants at the mobile phase/stationary phase interface.

Liquid chromatography, Adsorption