Saturated Solubility and Thermodynamic Evaluation of l-Tryptophan in Eight Pure Solvents and Three Groups of Binary Mixed Solvents by the Gravimetric Method at T = 278.15–333.15 K

In this research, solubility of l-tryptophan in water, methanol, ethanol, acetone, isopropanol, n-butanol, acetonitrile, ethyl acetate, organic pure solvent, and in three binary mixed solvents (water + acetonitrile), (water + methanol), and (water + isopropanol) at the temperature range of T = 278.15–333.15 K was determined with the gravimetric method. The experimental results show that the solubility of l-tryptophan in the above solvents increased as temperature rose, and it achieved the highest dissolution efficiency in water. The improved Apelblat model, the Buchowski–Ksiazaczak λh model, the Redlich–Kister (CNIBS/R–K) model, and the Jouyban–Acree model were used to nonlinearly fit the experimental data of solubility, and the consistency was good. The physicochemical information of l-tryptophan provided in this report may be helpful for its extraction/separation, recrystallization, purification, and formulation development.