The dissolution behavior and thermodynamic properties analysis of pentoxyverine citrate in aqueous solutions of alcohols

Abstract

The objective of this work is to study the dissolution behavior and thermodynamic properties of pentoxyverine citrate in aqueous solutions of alcohols. The results of solubility data at temperature range from 278.15 K to 318.15 K were obtained by the isothermal equilibrium method under atmospheric condition. In pure solvents, the largest solubility data in mole fraction is found in water at 318.15 K (2.756 × 10−2), followed by ethanol (1.156 × 10−2), n-propanol (8.129 × 10−3), isobutanol (5.233 × 10−3), isopropanol (4.340 × 10−3) and 1-butanol (3.435 × 10−3). The order of solubility from large to small is consistent with the order of solvent polarity. The solubility profile in mixtures of (ethanol + water), (n-propanol + water) and (isopropanol + water) increases firstly and then decreases with the increasing mass fraction of alcohols at all studied temperatures, and it reaches a maximum at w = 0.60 (the mass fraction of ethanol) in mixtures of (ethanol + water) at all investigated temperatures, for two other binary mixtures, the mass fraction of n-propanol and isopropanol is 0.40. The analysis of extended Hildebrand solubility approach indicate the solvent–solvent interactions and specific interactions are unfavorable for the dissolution process. The values of relative average deviation (RAD) for crystalline pentoverine citrate demonstrated well correlation of solubility values with Apelblat equation and Jouyban-Acree model. The positive values of ΔHsolo and ΔSsolo for dissolution behavior indicate the dissolution process was not only endothermic but also entropic-favouring. Moreover, the enthalpy is the main contributing force to the Gibbs free energy during the dissolution of pentoverine citrate.