Surface and micellar properties of some amphiphilic drugs in the presence of additives

In this study, the surface properties (in water and in the presence of varying concentrations of NaCl, CTAB, and TX-100) of four amphiphilic drugs are presented. The parameters evaluated are cmc (critical micelle concentration), Gamma(max) (maximum surface excess concentration at the air/water interface), and A(min) (minimum area per surfactant molecule at the air/water interface). Gamma(max) increases and cmc/A(min) decreases with increasing concentration of the additives. The cmc values calculated using a dye solubilization method for the systems also follow the same trend. The behavior is explained on the basis of counterion adsorption and mixed micelle formation.