Solubility Measurements and Correlation of Quetiapine Fumarate in 12 Individual Solvents and Tetrahydrofuran–Water from 283.15 to 323.15 K

The equilibrium solubility of quetiapine fumarate was determined in twelve individual solvents and one binary solvent mixture by the gravimetric method at atmospheric pressure over a temperature range of 283.15–323.15 K. The results showed that the solubility increases with increasing temperature in all selected solvents. The solubility order is tetrahydrofuran–water (mole fraction of tetrahydrofuran 0.8083) > tetrahydrofuran > n-propanol > dichloromethane > butanone > methyl isobutyl ketone > xylenes > ethyl formate > tert-butyl methyl ether > isopropyl acetate > toluene > hexane ≈ heptane. The modified Apelblat model, λh model, nonrandom two-liquid model, and van’t Hoff–Jouyban–Acree model were employed to correlate the experimental solubility. The four models provided satisfactory fits, as confirmed by the average relative deviation and the root-mean-square deviation. The modified Apelblat model showed the best performance among them. The accurate solubility data are essential for the design and optimization of the crystallization process of QF.