Thermodynamic properties of l-Theanine in different solvents

The solubility data of l-Theanine in pure water and three kinds of water + organic solvent mxitures were measured in temperature ranges from (278.15 to 13.15) K by using an equilibrium method. The results show that the solubility of l-Theanine increases with the increasing of temperature in all selected solvents. The modified Apelblat equation and the λ-h model were applied to correlate the solubility data in pure water, while the modified Apelblat equation, the λ-h model, the NRTL model and the Jouyban-Acree model were applied to correlate the solubility data in binary solvent mixtures. Furthermore, the mixing thermodynamic properties of l-Theanine in different solvents were also calculated based on the NRTL model and experimental solubility data.