Determination and Thermodynamic Model of the Solubility of Levodropropizine in 13 Pure Solvents at 283.15–323.15 K

In this paper, the solubility of levodropropizine, an important cough suppressant drug, in 13 pure solvents (including 8 alcohol solvents and 5 acetate solvents) was studied with the aid of a laser dynamic solubility-monitor device at a temperature from 283.15 to 323.15 K and atmosphere pressure. In the measured temperature range, the solubility of LVDP increases with increasing temperature and follows the following order: iso-butanol > iso-pentanol > n-hexanol ≈ n-heptanol > n-pentanol > n-propanol > n-butanol > iso-propanol > ethyl acetate > n-propyl acetate > n-butyl acetate > n-pentyl acetate > iso-propyl acetate. Three semiempirical models (modified Apelblat, three-parameter van’t-Hoff, and λh) and two activity coefficient models (Wilson and NRTL) were used to correlate solubility of LVDP as a function of temperature and the mixing thermodynamic properties of the 13 solutions were evaluated based on measured solubility and the parameter values of Wilson’s model.