Influence of fructose on the diffusion of potassium hydrogen phosphate in aqueous solutions at 25 °C

Highlights: • Diffusion coefficients of aqueous systems of fructose and potassium hydrogen phosphate measured with Lobo's cell. • Influence of the fructose on the diffusion of potassium hydrogen phosphate. • Interactions between of hydrogen phosphate anion and fructose. - Abstract: Diffusion coefficients have been measured at 25 °C for potassium hydrogen phosphate (K₂HPO₄, 0.101 mol kg⁻¹) in aqueous solutions containing various concentrations of fructose from (0.001 to 0.101) mol kg⁻¹, using a conductimetric cell (the Lobo cell) coupled to an automatic data acquisition system. Significant effects of fructose were observed on the diffusion of K₂HPO₄ in these mixtures, which are attributed to the interaction between HPO₄²⁻ anion (or other protonated forms) and fructose. Support for this comes from ¹H and ¹³C NMR spectroscopy, which are compatible with binding between the anomeric forms of D-fructose and the HPO₄²⁻ anion.