Molecular interactions of gentamicin sulphate in aqueous-l-asparagine/l-glutamine solutions at different temperatures: Volumetric, acoustic and viscometric properties

Abstract

The solute-solute and solute-solvent interactions are investigated by using the experimental values densities, ρ, ultrasonic speeds, u and viscosities, η of gentamicin sulphate in water and in aqueous l-asparagine/l-glutamine (1% and 2% l-asparagine/l-glutamine in water) solvents at temperatures (293.15, 298.15, 303.15, 308.15, 313.15 and 318.15) K and at atmospheric pressure. The experimental ρ and u data have been used to calculate the apparent molar volumes, Vφ, limiting apparent molar volumes, Vϕ°, apparent molar compressibilities, Ks, ϕ, limiting apparent molar compressibilities, Ks, ϕ°, transfer volumes, Vϕ, tr°, transfer compressibilities, Ks, ϕ, tr° and limiting partial molar expansivity of solute, Eϕ°. Also, the Falkenhagen Coefficients, A and Jones-Dole coefficients, B were evaluated from experimental viscosity data. The Gibbs free energies of activation of viscous flow per mole of solvent, Δμ1°# and per mole of solute, Δμ2°#, entropies, ΔSο and enthalpies, ΔHο of activation of viscous flow were also calculated and discussed in terms of transition state theory. These parameters have been discussed in connection with the electrostatic interactions between the zwitterionic groups of amino acids and drug molecules. The structure-making/breaking ability of the drug in these solutions was also analyzed using the signs and magnitudes of (∂2Vϕ°/∂T2) and dB/dT coefficients.