Solubility and the solution thermodynamics of l-proline in the aqueous binary mixture of NaCl and KCl solution

Abstract

This paper presents a comprehensive investigation into the equilibrium solubility and thermodynamic behavior of l-proline, a biologically and pharmaceutically significant protogenic non-essential amino acid, in both aqueous and aqua-electrolytic solutions. The study explores the effects of concentration variations at specific temperatures and temperature variations at specific concentrations. The experimental analysis is conducted using analytical gravimetric techniques. The observed phenomena are explained based on various chemical interactions, including ion-dipole and dipole-dipole interactions, present in electrolytic and pure aqueous solutions of the amino acid. The salting in/out effect is also considered to support the solubility results. The experimental results demonstrate that l-proline exhibits increased solubility in the presence of electrolytes compared to pure aqueous solutions, considering the variations in both temperature and concentration. Furthermore, the solubility of l-proline is found to be higher in the presence of KCl than NaCl as an electrolyte in aqueous media. The physical properties and sizes of both the amino acid and electrolytes are identified as crucial factors influencing the observed solubility trends. © 2023 Elsevier B.V.