Depolarization thermocurrents in frozen aqueous solutions of mono- and di-saccharides

The dielectric behaviour of frozen aqueous solutions of the monosaccharides glucose, galactose, mannose, ribose and arabinose and the disaccharides cellobiose, lactose and maltose was studied by the depolarization thermocurrent (DTC) method in the temperature range 80–270 K and over a wide range of concentrations (0.0003–1.5 mol/l), to obtain information on the state of water in the solutions. The results show that the saccharides studied can be subdivided into two classes regarding their hydration behaviour. The solutions of glucose, galactose and mannose are characterized by a continuous transition from hydration (i.e. affected by the solute molecule) to free (i.e. non-affected) H₂O molecules. The solutions of ribose, arabinose, cellobiose, lactose and maltose are characterized by the presence of two dicrete kinds of H₂O molecules, namely free and hydration molecules. These results are discussed in terms of a hydration model.