J. Phys. IV France 03 (1993) C4-297-C4-303
Studies of cyclodextrin complexes by positron annihilationF.H. HSU1, J.M. MICHAEL1, L. SONG1 and D.W. ARMSTRONG2
1 Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30033, U.S.A.
2 Department of Chemistry, University of Missouri-Rolla, Rolla, MO 65401, U.S.A.
The positron annihilation technique has been applied to study cyclodextrin complexes formation. Lifetime spectra have been measured in aqueous solutions of nitrophenol isomers, cyclodextrins, and cyclodextrins mixed with nitrophenol isomers. The spectra were resolved into three lifetime components. The intensity, I3, of the longest-lived component was found to be decreased linearly with respect to the concentration of nitrophenol isomers in an aqueous solution. In the aqueous solution of cyclodextrins, concentration had little effect on I3. However, I3 increased with respect to the concentration of cyclodextrins in aqueous solutions mixed with a fixed amount of nitrophenol isomers. Several methods based on these findings are proposed to determine the formation equilibrium constants for inclusion complexes of nitrophenols by cyclodextrins.
© EDP Sciences 1993