Structure making behaviour of L-histidine in aqueous solutions of ampicillin sodium at different temperatures: Using physicochemical methods

Experimentally determined values of density (ρ), speed of sound (u) and viscosity (η) have been used to investigate solute-solvent interactions of L-histidine in aqueous ampicillin sodium (an antibacterial drug) solutions at different concentrations (0.035, 0.055, 0.075 and 0.095) mol kg−1, over a wide range of temperatures (293.15, 298.15, 303.15, 308.15 and 313.15) K and at atmospheric pressure. The experimentally determined density (ρ) data has been used to obtain various parameters, for instance: apparent molar volume (VΦ), limiting apparent molar volume (VoΦ), limiting apparent molar volume of transfer (VoΦ,tr), limiting molar expansivity (EoΦ) and hydration number (nH). The speed of sound (u) data helps to enumerate apparent molar isentropic compression (KΦ,S), limiting molar isentropic compression (KoΦ,S), limiting apparent molar isentropic compression of transfer (KoΦ,S,tr) and hydration number (nH) i.e., the number of water molecules hydrated to the amino acid. Relative viscosity (ηr), Jones-Dole coefficient-B (B) and viscosity B-coefficients of transfer (Btr) were calculated from viscosity (η) data. The results obtained from this data, showed the existence of physico-chemical interactions, (i.e., hydrophilic-ionic and hydrophilic-hydrophilic) in ampicillin sodium L-histidine solutions. The structure making behaviour of L-histidine in aqueous ampicillin sodium solution was studied in terms of Hepler's constant ∂2VΦo∂T2P, coefficient of thermal expansion (α) and temperature derivative of B-coefficient (dB/dT).