Preferential solvation of quercetin in aqueous aprotic solvent mixtures

Solvatochromism of quercetin was studied in binary mixtures of water with dimethyl sulfoxide, N,N-dimethylformamide and N,N-dimethylacetamide at 25 degrees C by UV-Vis measurements. For all mixtures, a non-linear trend was observed in spectral shifts plotted against the bulk mole fractions. Deviation from ideal behaviour indicates that the solvation shell of quercetin differs in composition from the bulk because of preferential solvation. The solvent exchange model was applied in the analysis of solvatochromic data in order to quantify the extent of preferential solvation in the case of solute-solvent and solvent-solvent intermolecular interactions. The results show that the solvation shell of quercetin is enriched in aprotic solvent and the complex that was formed by the interaction between water and an aprotic solvent, over the whole composition range. The distribution of the solvent species in the solvation cage was obtained from the calculation of the local mole fractions as a function the bulk composition. It shows that the solvent-solvent interactions have great influence on the solvation behaviour of quercetin in aqueous aprotic solvent mixtures.