Solubility and thermodynamic properties of L-Pyroglutamic acid in pure and binary solvents

Abstract

The solubility of L-Pyroglutamic acid in H2O, methanol, ethanol, n-propanol, isopropanol and four binary solvent systems (H2O + methanol/ethanol/n-propanol/isopropanol) from (293.15–344.35) K was experimentally determined under atmospheric pressure by using isothermal saturation method. The results indicated that the solubility of L-Pyroglutamic acid in all the tested pure and binary solvent systems monotonously increased with increasing of the temperature at the measurable range. The solubility order of L-Pyroglutamic acid in pure solvents was ranked as: H2O > methanol > ethanol > n-propanol ≈ isopropanol. Part solubility of L-Pyroglutamic acid in the mixture of H2O + methanol/ethanol/n-propanol/isopropanol became larger than that in both pure solvents. Besides, Ideal model, the Apelblat model, λh model, Wilson model and NRTL model were used to correlate the experimental solubility data of L-Pyroglutamic acid in five pure solvent systems and the solubility in binary solvent systems were correlated by Ideal model, the Apelblat model, λh model, Wilson model, NRTL model, the Apelblat-Jouyban-Acree (A-JA) model and the Van't Hoff- Jouyban-Acree (Van't-JA) model. All of them gave satisfactory correlations. Finally, the mixing and dissolution thermodynamic properties, including Gibbs energy, entropy and enthalpy of L-Pyroglutamic acid in all tested solvents were calculated by the Wilson equation and the solubility data.