Binary Solid–Liquid Solubility Determination and Model Correlation of Quizalofop- p -ethyl in Different Pure Solvents

The solid–liquid equilibrium for quizalofop- p -ethyl in 12 solvents (methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, N, N -dimethylformamide (DMF), acetone, acetonitrile, ethyl acetate, 1,4-dioxane, toluene, and 1-hexane) was measured by using a static equilibrium method at temperatures T = 273.15–313.15 K under a pressure of 101.2 kPa. The results show that the solubility in those 12 monosolvents increases with increasing temperature. At a given temperature range, they gradually decrease in the following order: 1,4-dioxane > acetonitrile > DMF > toluene > acetone > ethyl acetate > 1-butanol > 1-propanol > 1-hexane > 2-propanol > ethanol > methanol. Moreover, a modified Apelblat model, λh model, Wilson model, and NRTL model were used to correlate the experiment values. Compared with the results of the above models, the calculated values provided good results with the experimental data. Consequently, the values of root-mean-square deviation (RMSD) and relative average deviation (RAD) were no more than 4.57 × 10 –4 and 2.29%, respectively. Furthermore, the thermodynamic properties of quizalofop- p -ethyl in monosolvents were calculated. From the analysis results, the dissolution process of quizalofop- p -ethyl was a spontaneous and entropy-driven process. The experimental solubility and the models in this study could be helpful in the application in the field of purification and recrystallization.