Studies of the complexation of sugars by diffusion-ordered NMR spectroscopy

In the presence of lanthanide cations, some sugars with a special relationship between their hydroxyl groups are able to form complexes in water. Diffusion-ordered NMR spectroscopy (DOSY) can be used as a tool to distinguish between the complexed and noncomplexed forms in a mixture due to the differences in their relative diffusion coefficient values. The lowest diffusion was attributed to the complexed species because of the increase in both size and molecular weight when compared with the noncomplexed forms. Mixtures of sugars of the same molecular weight and also the isomers of a single monosaccharide can be ‘separated’ by DOSY on the basis of their different tendencies to form complexes with different diffusion coefficient values.