Solubility Behavior and Polymorphism of <scp>l</scp>-Arginine <scp>l</scp>-Pyroglutamate in Nine Pure Solvents and a Binary Water + Ethanol System
Shen Hu, Jiaming Han, Haoyou Liu, Jingxuan Qiu, Yue Zhao, Ying Guo, Haishuang Huang, Hui He, Peng Wang
Abstract
The solubility data of l-arginine l-pyroglutamate were determined by the static gravimetric method from 283.15 to 323.15 K in nine pure solvents (water, methanol, ethanol, isopropanol, acetone, acetonitrile, dichloromethane, ethyl acetate, and n-hexane) and a water + ethanol binary solvent system. According to experimental results, solubility was positively correlated with temperature. In the selected solvent systems, three different polymorphs denoted as α-form, β-form, and γ-form were found. In addition, from the data analysis results, the polarity, hydrogen bonding, Hildebrand solubility parameters, and the molecular structure affected the dissolution equilibrium. Two thermodynamic models including the modified Apelblat model and the Yaws model were used to correlate the solubility data. Meanwhile, these models were evaluated by the Akaike information criterion method.