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

Abstract 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 ( V Φ ), limiting apparent molar volume ( V o Φ ), limiting apparent molar volume of transfer ( V o Φ,tr ), limiting molar expansivity ( E o Φ ) and hydration number ( n H ). The speed of sound ( u ) data helps to enumerate apparent molar isentropic compression ( K Φ,S ), limiting molar isentropic compression ( K o Φ,S ), limiting apparent molar isentropic compression of transfer ( K o Φ,S,tr ) and hydration number ( n H ) i.e., the number of water molecules hydrated to the amino acid. Relative viscosity ( η r ), Jones-Dole coefficient- B ( B ) and viscosity B -coefficients of transfer ( B tr ) 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 ∂ 2 V Φ o ∂ T 2 P , coefficient of thermal expansion ( α ) and temperature derivative of B -coefficient ( dB / dT ) .