Nucleation Kinetics of Ascorbic Acid in Various Aqueous Solvents

Abstract

The nucleation kinetics of ascorbic acid in water and binary solvent systems of ethanol−water and isopropanol−water have been analyzed by the classical nucleation theory. For that, in total, 3065 data of induction time were collected by the isothermal method at five supersaturations in each solvent system. The induction time data are well represented with the Poisson probability distribution to determine the nucleation rate (J) and growth time (t g ). The nucleation rate is found to be highest in water (1319.87 m −3 s −1 ) and decreases with increasing the alcohol composition in the binary solvent systems, showing the minimum nucleation rate (179.24 m −3 s −1 ) in the isopropanol−water system with a 0.6/0.4 mole fraction ratio. Furthermore, the kinetic parameter (A) decreases, whereas the thermodynamic parameter (B) increases with an increase in the alcohol composition in the aqueous solvent system. The interfacial energy (γ), critical radius (r c ), and Gibbs free energy (ΔG c ) were observed to be high for solvent systems with higher alcohol composition, which indicates a lower interaction between the solute and solution due to high interfacial tension.

Comparison of the interfacial energy and pre-exponential factor for isonicotinamide in various solvents from the induction time and metastable zone width data

“…24 As the nucleation process of a substance is often affected by the selection of solvent, comparison of the nucleation behaviors in different solvents has been an important research issue. 25–35 In this study, the induction time and MSZW for INA in various solvents, including methanol, acetone, acetonitrile, and ethyl acetate, were experimentally measured under various conditions. The interfacial energy and pre-exponential factor for INA in each solvent obtained from the MSZW were compared with those obtained from the induction time.…”