Dielectric relaxation study of some solutions containing beta-cyclodextrinand dimethylsulfoxide

Dielectric spectra have been measured up to 72 GHz at 20 degrees C for solu tions of beta-cyclodextrin (CD) in the following solvents over the whole, s olubility range of CD: dimethylsulfoxide (DMSO), DMSO/1,4-dioxane mixture ( 2:1 molar ratio), DMSO/water mixtures (2. 1 and 1:2). The spectra are analy zed into a sum of Debye type spectral components. These are likely to be ca used by different physical processes. The discussion shows (i) that there i s a preferential CD-DMSO interaction, by far exceeding the CD-water interac tion, and (ii) that, concerning CD-DMSO, a loose interaction can be disting uished from the formation of an inclusion complex.