Determination of Association Constants of Cyclodextrin-Nonionic Surfactant Inclusion Complexes by a Partition Coefficient Method

The partition behavior of isotopic labeled nonionic surfactants between carbon tetrachloride and an aqueous solution containing -cyclodextrin (-CD) was studied with a liquid scintillation counting technique. The association constants of the inclusion complexes were determined at different temperatures. It was found that the nonionic surfactants form 1 : 1 inclusion complexes with -CD. The results demonstrated that the smaller the HLB values of the nonionic surfactants, the greater the association constants with -CD, and that for the same surfactant the association constant is higher at lower temperatures.