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The distribution of alkyl paraben in aqueous sodium lauryl sulfate micellar solutions

1978; Elsevier BV; Volume: 66; Issue: 1 Linguagem: Inglês

10.1016/0021-9797(78)90180-7

1095-7103

Ayako Goto, Fumio Endo,

Thermodynamic properties of mixtures

The apparent distribution coefficients, Ka, for methyl-, ethyl-, and butylparabens between the sodium lauryl sulfate (SLS) micellar and aqueous phases were measured from the elution curves of SLS and alkyl paraben obtained by the tail analysis on Bio Gel P-4. The results show that the Ka was a linear function of the molar fraction of alkyl paraben in the micellar phase (Xsm). In view of this relationship, the distribution coefficients, Kt, were estimated from the Ka values on the basis of ideal solution theory. The free energy change of a solubilizate for a transition from the aqueous to micellar phase, ΔGt, was calculated from the Kt. The solubilized system was analyzed thermodynamically on the basis of the ΔGt. The results show that an approximately linear relationship exists between the ΔGt and the carbon number of the alkyl paraben. Furthermore, the CMC decreasing effect which describes stabilization of micelle on solubilization was confirmed experimentally to be correlated with ΔGt.