Hydration properties and proton exchange in aqueous sugar solutions studied by time domain nuclear magnetic resonance

Proton NMR relaxation rates (R₁ and R₂) were measured in aqueous solutions of sucrose, d-glucose and d-fructose with increasing concentration. The measurements were carried out using Bruker PC 20 NMR Process Analyzer. Inversion recovery and CPMG pulse sequences are used for the measurement of relaxation rates. Results show that the values of relaxation rate increase as the concentration of the sugar is increased. The relaxation rate appears to be higher for sucrose solutions as compared to glucose or d-fructose solutions. These results were discussed on the basis of molecular association between sugar and water molecules through hydrogen bonding. The water self diffusion coefficient was measured in these sugar solutions by using pulse field gradient NMR method. As expected, the water self-diffusion coefficient was reduced with increased sugar concentrations. The results of translational mobility exhibited a higher mobility for fructose than glucose or sucrose in aqueous solutions.