(378g) Solubility of L-Phosphinothricin and Its Hydrochloride in Water + (Methanol, Ethanol) Binary Solvent Mixtures from 278.15 K to 318.15 K

L-Phosphinothricin (L-PPT, (2S)-2-amino-4-(hydroxymethylphosphinyl)butanoic acid, CAS No. 35597-44-5) is the active ingredient of the broad-spectrum, nonselective herbicide DL-phosphinothricin ammonium salt. The separation and purification of L-PPT from aqueous solution containing organic and inorganic salts is one of the key technologies in the production of L-PPT. L-PPT can be solvated by water to form L-PPT monohydrate under certain conditions. L-PPT hydrochloride (CAS No. 73777-49-8) is usually obtained as an alternative product in the preparation process of L-PPT.

L-PPT and its hydrochloride can be separated from aqueous solution by using the method of anti-solvent crystallization. Methanol and ethanol are considered to be suitable anti-solvents for their good miscibility with the solution and high efficiency. The operational level of the anti-solvent crystallization process has a great effect on product quality; therefore, a reliable knowledge of the solubility of L-PPT and its hydrochloride in binary mixed solvents of water + (methanol, ethanol) is necessary for the design of a good crystallization process.

The solubility of L-PPT and its hydrochloride in water + (methanol, ethanol) binary solvent mixtures was experimentally measured from 278.15 K to 318.15 K by a static analytic method under atmospheric pressure. The experimental data showed that the solubility increased with the increasing temperature and decreased with the increase of alcohol concentration in the binary solvent mixtures. The experimental data were correlated by the modified Apelblat equation and CNIBS/R–K model. The correlation models were evaluated according to the relative average deviations. The results indicated the modified Apelblat equation showed better agreement with the experimental data. The local mole fractions of methanol in the local area around L-PPT were calculated, and the result showed that the preferential solvation of L-PPT was related to the solvent composition and temperature. The experimental data and the corresponding models can be used as essential data in the design of the crystallization process of L-PPT and its hydrochloride.