Investigations on molecular interaction of some amino acids with the drug levofloxacin in aqueous solution by volumetric and acoustic methods at different temperatures

Apparent molar properties (V∅ and K∅,s) of amino acids (glycine, L-alanine and L-valine) within the concentration range of (0.02-0.20) mol·kg−1 in aqueous (0.005, 0.01 and 0.03) mol·kg−1 Levofloxacin (LVFX) solutions are computed from the experimental density (ρ) and ultrasonic speed (c) values at T = (288.15, 293.15, 298.15, 303.15 and 308.15) K and P = 0.1 MPa. Derived parameters such as partial molar properties (V∅0 and K∅,s0) and their experimental slopes (SV and SK), transfer partial molar properties (ΔV∅0 and ΔK∅,s0), hydration numbers (nH) and Hepler's constant are computed from the data of apparent molar properties. The pair and triplet interaction coefficients have also been evaluated from transfer parameters. The linear variation of V∅0 with the number of carbon atoms in the alkyl chain of amino acids has been utilized to calculate the contribution of the charged end groups (NH3+,COO-), (CH2) group and other alkyl chains of the amino acids to V∅0. From the obtained parameters, some information in regard with the solute-solvent interaction in the systems studied was obtained. The co-sphere overlap model was used to interpret the positive transfer properties (ΔV∅0 and ΔK∅,s0). The volume and compression data suggest that there exist strong solute-solvent interactions in these systems, which increase with increase in temperature. It is inferred that amino acids studied act as structure-breaker (chaotropic effect) in aqueous LVFX solutions.