MEASUREMENTS OF SELF-DIFFUSION COEFFICIENTS OF MONENSIN IN CHLOROFORMSOLUTION BY PFG-NMR

The self-diffusion coefficients D of MonH . H2O and MonNa have been me asured by pulsed held gradient NMR (PFG-NMR) as a function of the conc entration C. An exponential dependence of D on C has been found and ex plained on the basis of the free volume theory. The diffusion coeffici ents in the infinite dilute solution D()) for MonH . H2O and MonNa hav e been estimated by extrapolating to C = 0 using the relationship betw een diffusion coefficient and solute concentration based on free volum e theory. Valves of D(0) estimated in this way have been applied to th e Stokes-Einstein equation in order to obtain Stokes' radii. The radiu s of MonNa (0.511 nm) was larger than that of MonH . H2O (0.484 nm). T hese values were not very different from the radii of gyration (0.435 nm) in crystalline MonH . H2O.