Studies of the Measurement of the Intermicellar Concentration of Surfactants by Gel Filtration

Abstract

Abstract Equations are derived which are used to calculate the intermicellar concentration (Cs) of a surfactant from measurements of the elution volumes of micelles, the elution front and the intermicellar monodisperse molecules or ions. These quantities are obtained by the gel filtration of a surfactant charged in band form through a gel column previously filled with the same surfactant at a lower concentration. The Cs values found are not constant, but increase and the increase becomes less pronounced with the concentration (C) of the surfactant, both for sodium dodecyl sulfate and α-dodecyl-ω-hydroxyhexa(oxyethylene). This confirms that the concentration C–Cs of the micelles which move during the gel filtration is smaller than the usually-employed concentration C–Cm of micelles in a stationary state, where Cm denotes the critical micelle concentration.