A STUDY OF THE BINDING OF DIMETHYLDODECYLAMINE OXIDE BY BETA-CYCLODEXTRIN USING SURFACE-TENSION MEASUREMENTS

A surface tension method developed previously has been used to investi gate the formation of inclusion compounds between dimethyldodecylamine oxide (DDAO) and beta-cyclodextrin, at pH values in the range 2 to 8, in the absence and in the presence of added 0.10 M NaCl. Thermodynami c activities of the DDAO are inferred from measurements of surface ten sion at concentrations lower than the critical micelle concentration o f the surfactant. Binding constants are determined directly from the e ffect of added cyclodextrin on the surface tension vs concentration cu rves for DDAO in water and in the 0.10 M NaCl solutions. Binding effec ts are discussed in relation to the charge of the DDAO head group, whi ch can be controlled by varying the pH, and the screening effect of th e added electrolyte. (C) 1994 Academic Press, Inc.