Determination of association constants of cyclodextrin-nonionic surfactantinclusion complexes by a partition coefficient method

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