Temperature-dependent volumetric and ultraacoustic studies of α-amino acids in aqueous acetylsalicylic acid drug solutions

Present paper reports the results of densimetry and ultrasonic velocimetry studies of solutions of glycine, L-serine, L-proline, L-asparagine monohydrate and L-arginine in aqueous non-steroidal anti-inflammatory acetylsalicylic acid as a function of its molality. For this purpose, density and ultrasonic velocimetry data were obtained at atmospheric pressure as a function of amino acid concentration at fixed acetylsalicylic acid concentration (m = 0.001, 0.005 or 0.010 mol . kg(-1)) and temperature (T = 303.15, 308.15 or 313.15 K). The density and ultrasonic velocity data have been used to calculated the apparent molar volume (V-2,V- phi) and apparent molar isentropic compressibility (kappa(S, 2,) (phi)) of studied solutions. The standard molar volume (V-2,V- (o)(phi)) and compressibility (kappa(S, 2,) (0)(phi)) were determined by least least-squre fitting of respective apparent properties to the amino acid molality. Further, these data were used to calculate standard transfer volume (Delta V-t(2,) (o)(phi)) and compressibility (Delta(t)kappa(0)(S, 2, phi)) of the studied solutions. The results have been interpreted in terms of different solute-solvent interactions and effect of acetylsalicylic acid on hydration of amino acids. Significant effect of added acidic cosolute drug on solute-solvent interactions including hydration of amino acids has been observed. Negative standard transfer volumes in the case of L-arginine in presence of drug validate the charge transfer to L-arginine from drug and hence enhanced electrostriction of the solvent. (C) 2018 Elsevier B.V. All rights reserved.