Confirmation of the Mukerjee term in an extended Corrin-Harkins relation using an anionic amphiphilic drug

The amphiphilic behavior of the S-enantiomer of 3(S)-[(2-carboxyethyl)sulfanyl]-3-[2-(8-phenyloctyl)phenyl] propionic acid disodium salt (C26H32O4S.2Na) has been investigated as a function of the ionic strength, mu (buffer and simple electrolyte). The linearity predicted by the Corrin-Harkins relation (J. Am. Chem. Soc. 1947, 69, 683-688) is observed at low buffer concentrations, and it is verified that the nature of the buffer is of less importance than the concentration of the counterion. At high counterion concentrations, the salting-out effect predicted by Mukerjee in 1965 (J. Phys. Chem. 1965, 69, 4038-4040) and 1967 (Adv. Coll. Interf. Sci. 1967, 1, 241-275) manifests itself, and a more complete equation resulting from attaching a salting-out term to the Corrin-Harkins relation, as used recently by Mukerjee and Chan (ACS Abstracts of Papers 1993, 206, COLL 164; Ph.D. Thesis, University of Wisconsin, 1993), gives a better representation of the experimental data. It is shown that the parameter values obtained from this equation are reasonable and predict self-association in the form of micelles rather than as small aggregates.