Temperature-dependent volumetric and viscometric properties of amino acids in aqueous solutions of an antibiotic drug

Abstract

AbstractVolumetric and viscometric properties of glycine and methionine (amino acids) in a 0.2 vol. % amikacin sulphate (antibiotic drug) aqueous solution with the molality range of 0.025 mol kg−1–0.25 mol kg−1 were measured over the temperature range of 20°C–40°C at the interval of 5°C. Different parameters like apparent molar volume (ϕ V), apparent molar adiabatic compression (ϕ κ), isentropic compression (κ S) along with other acoustical parameters were calculated. Parameters like viscous relaxation time (τ), free volume (V F), internal pressure (Π I), and molar cohesive energy (MCE) were calculated from dynamic viscosity measurements. The ϕ V values are positive in both cases, but with higher magnitude observed in methionine. These positive values of ϕ V are indicative of strong solute-solvent interactions at all temperatures. In case of methionine there is a sharp initial increase in the ϕ V values which become almost constant with further additions of the amino acid. Structural differences in the two amino acids studied are clearly reflected in the different nature of the plots of different parameters. In case of an amino acid-drug system, dynamic viscosity increase has been attributed to the increase in the hydrophilic-ionic and hydrophilic-hydrophilic interactions with the increase in the amino acid concentration which in turn may cause more frictional resistance to the flow of the solution. All other parameters are discussed in terms of solute-solvent and solvent-solvent interactions.