Excess adsorption of binary aqueous organic mixtures on various reversed-phase packing materials

► Excess adsorption isotherms were measured on 8 commercial reversed-phase columns of different silica structure. ► Adsorption of the same adsorbate on all studied columns is essentially identical when expressed in surface specific form. ► Adsorption of acetonitrile from water compared to adsorption of methanol from water. ► Standard isotherm for excess adsorption of acetonitrile and methanol from water is suggested.