Thermodynamic study on dynamic water and organic vapor sorption on amorphous valnemulin hydrochloride

The sorption of water and organic vapors on valnemulin hydrochloride was determined by dynamic vapor sorption at 25 °C. The adsorption-desorption behavior of water vapor and a series of organic vapors was investigated to probe the structural changes in valnemulin hydrochloride before and after sorption. The isothermal adsorption equilibrium data was evaluated using Guggenheim-Anderson-deBoer (GAB) and Brunauer-Emmett-Teller (BET) models. The BET model is applicable only at low relative pressures (0.1⩽RP⩽0.4) while the GAB model is applicable in the whole range of RPs (0.1⩽RP⩽0.9). The sorption kinetics at high RPs was determined by fitting the sorption data to the Avrami equation and the sorption content vs. time relationship could be predicted by the Avrami equation. Finally, the possible sorption mechanism of valnemulin hydrochloride was also discussed. [graphic not available: see fulltext]