Insight into Interactions of l-Arginine/l-Histidine with Drug Betaine Hydrochloride in Aqueous Medium at Different Temperatures by using Physicochemical Methods

Abstract

Studies on physicochemical properties of l -arginine/ l -histidine in aqueous solutions of betaine hydrochloride are beneficial in understanding solute-solvent interactions. The densities, ρ , ultrasonic speeds, u and viscosities, η of l -arginine and l -histidine in water and in aqueous-betaine hydrochloride (1 % and 2 % betaine hydrochloride in water, w/w) solvents have been experimentally measured at six temperatures (293.15, 298.15, 303.15, 308.15, 313.15 and 318.15) K and at atmospheric pressure in nine different concentrations. Related molecular and thermodynamic properties like the apparent molar volume, V φ , limiting apparent molar volume, and transfer volume, , were also evaluated in this study using density data. Likewise from the ultrasonic data, different thermo-acoustical parameters, such as apparent molar compressibility, , s K φ , limiting apparent molar compressibility, , s K οφ and transfer compressibility, , , s tr K οφ have been evaluated. The trends in transfer properties have been interpreted in terms of cosphere overlap model. In addition, the rheological data have been used to determine Falkenhagen Coefficient, A , Jones-Dole coefficient, B , free energy of activation of viscous flow per mole of solvent, and solute, #2 , entropies, # S ο ∆ and enthalpies, # H ο ∆ of activation of viscous flow. Hydration number, H n has also been calculated. Different parameters such as nature of solute, solute-solvent interactions, etc., were categorized by using different analytical and physical loom. The results show that the studied drug is a structure maker compound in all systems of this work. The free energy parameters indicate the formation of transition state in the presence of amino acids. The solute co-solute interactions are strongest in the system containing l -arginine.