Solute-micelle interactions in zwitterionic micellar chromatography

Equilibrium constants relating the solute concentration in the mobile phase and the solute-micelle complex concentration in the mobile phase were determined for two micellar zwitterions, dodecyldimethyl(3-sulfopropyl)ammonium hydroxide (inner salt) (SB-12) and myristyl betaine (MB-14), with a series of substituted benzene derivatives. The chromatographic capacity factors, k, were employed to calculate equilibrium constants (Keq). A rationale is suggested based on experimental results to aid in explaining the zwitterionic micelle-solute intermolecular interactions. Specific attention is given to the polar phenol molecule interactions with SB-12 and sodium dodecyl sulfate (SDS) obtained from membrane equilibrium experiments. Linear Scatchard plots indicate that one phenol molecule is bound to one zwitterion monomer in the micelle.