抄録
The presence of complexes of monomer sodium lauryl sulfate (SLS) and alkylparaben (methyl-, ethyl-, and butyl-parabens) can be observed by gel filtration on Bio-Gel P-4. Stability constants for the complex formation from monomer SLS and respective alkyl parabens in aqueous SLS solutions below critical micelle concentration (s) (cmc) were estimated from the elution curves of SLS and alkylparabens obtained by the tail analysis on Bio-Gel P-4. It was found that stability constants increased as the carbon number of alkyl group for alkylparabens increased. It was observed that stability constants for the complex formation in SLS micellar solutions solubilizing alkylparabens were nearly equal to those in the SLS solution below cmc. However, the partition ratio of respective alkylparabens between the aqueous and SLS micellar phases, found by considering a complex formation in the solubilized system, was approximately equal to the apparent partition ratio obtained without considering the complex formation, because concentration of the complexes was negligibly low compared with those of free alkylparabens in the aqueous phase.
