dl-isoprenaline hydrochloride solubility in four binary solvents at saturation: Thermodynamic analysis, Hansen solubility parameters and Molecular simulation

Abstract The solubility properties of dl-isoprenaline hydrochloride (dl-IPN) in four kinds of binary-solvents systems {(n-propanol, n-butanol, 2-propoxyethanol and 2-butoxyethanol) + methanol} at temperature range of 278.15-323.15 K under 101.3 kPa was further investigated using the laser monitoring technique. According to the result about solubility of dl-IPN in these chosen binary solvents, it is obvious that dl-IPN is more soluble at higher temperature. Additionally, the solubility values of dl-IPN, in all the investigated binary solvent mixtures, is improved with increasing mass fraction of co-solvent (methanol). The Hansen solubility parameters (HSPs) interpretate reasonably the order of dl-IPN solubility in these binary-solvents systems. Furthermore, the molecular dynamic (MD) simulation is employed to describe the molecular interactions of the types solute-solvent and solvent-solvent, and the obtained results confirm that solute-solvent and solvent-solvent molecular interactions have deep impact on the solubility of dl-IPN. The obtained experimental data about the solubility of dl-IPN is fitted by five models (λh equation, Apelblat equation, Jouyban-Acree-Apelblat (J-A-A) model, Ma model and Sun model). The analysis of thermodynamic properties was based on the values of the calculated thermodynamic parameters. It can be concluded that the dl-IPN dissolution process is entropy-motivated and endothermal in all the investigated binary-solvents systems, and that the main contribution to ΔdisGo is due to enthalpy.