Uncommon temperature effect on the interaction between levodopa and β-cyclodextrin seen by diffusometry and NMR spectroscopy

Abstract Experimental ternary mutual diffusion coefficients ( D 11 , D 22 , D 12 and D 21 , obtained by the Taylor dispersion method, are reported for aqueous solutions of levodopa (L-dopa) + β-cyclodextrin (β-CD) solutions at 310.15 K and concentrations up to 0.007 mol dm −3 . Comparison of these experimental results with data predicted by a model of the diffusion that includes inclusion complexes, it is possible to conclude that the association equilibrium at 310.15 K has little effect on the diffusion properties. Support for this comes from 1 H NMR spectroscopy, which shows that there are no interactions, which may be related to the reduced L-dopa/cavity interactions resulting from both the amine and carboxylate groups on L-dopa being charged.