Equilibrium Solubility Determination and Modeling for Cinosulfuron in Several Cosolvent Mixtures

Cinosulfuron was dissolved in a series of cosolvent mixtures, which involved five pure solvents as raw materials and formed four sets of mixed solvents according to their pairs by mixing methanol, ethanol, n-propanol, and N,N-dimethyl formamide (DMF) in water. Taking 278.15 K as the starting temperature and referring to the principle of the isothermal static state, the temperature is gradually increased at 5 K intervals until it reaches 323.15 K. Under normal pressure (101.1 kPa), when the mole fraction of the solute did not change, the value obtained by HPLC was the equilibrium solubility of cinosulfuron. From the point of view of temperature, the influence on the solute cannot be ignored. The amount of cinosulfuron dissolved from a low value to a high value with the temperature from low to high. In addition, the difference was that the water content of the mixed solvent was repulsive to the dissolution of the solute. When the water content was from low to high, the mole fraction of cinosulfuron was from high to low. In any temperature environment, the same proportion of water was added to the four organic solvents. Compared with other solvents, the mixture of DMF and water had an absolute dissolution advantage. Besides, the Jouyban–Acree model, van’t Hoff–Jouyban–Acree model, and Apelblat–Jouyban–Acree model were used to correlate the solubility of cinosulfuron. The largest relative average deviation and root-mean-square deviation were 1.01 × 10–2 and 1.78 × 10–4 based on the correlation results, respectively. The acquisition of solubility helps in obtaining solubility parameters, which is a measure of intermolecular forces. Solubility is required in the fields of recrystallization and fractional crystallization in the chemical industry, as well as the synthesis and separation of compounds.