Investigation on molecular interaction of amino acids in antibacterial drug ampicillin solutions with reference to volumetric and compressibility measurements

The interactions of some simple amino acids (AA) like alanine, valine and leucine with drug ampicillin (AMP) as a function of temperature have been investigated by combination of volumetric and acoustic methods. Densities and speeds of sound of alanine, valine and leucine in aqueous solutions of ampicillin have been measured at T =(305.15, 310.15 and 315.15) K and atmospheric pressure. The apparent molar volume (V-Phi), the partial molar volume (Delta(0)(Phi)), limiting apparent molar expansibility (Phi(0)(E)) and standard partial molar volumes of transfer (Delta V-phi) for amino acids from water to aqueous ampicillin solutions have been calculated from density data. Partial molar adiabatic compressibility (K-Phi,K-s) and partial molar adiabatic compressibility of transfer (Delta K-Phi,S(0)) have been calculated from speed of sound data. The pair and triplet interaction coefficients have been calculated from both the properties. The results have been explained on the basis of competing patterns of interactions of co-solvent and the solute. (C) 2012 Elsevier B.V. All rights reserved.