Volumetric, acoustic and viscometric studies of solute-solute and solute-solvent interactions of glycine and its peptides in aqueous solutions of an antidepressant drug at different temperatures

Abstract

From the density (ρ), speed of sound (u) and viscosity (η) measurements, the interactions of glycine, glycylglycine and glycylglycylglycine with antidepressant drug, nortriptyline hydrochloride have been investigated in aqueous medium at temperatures, T = (293.15–313.15) K and experimental pressure p = 0.1 MPa. From the experimental density measurements, apparent molar volume (VΦ), limiting apparent molar volume (VoΦ) and partial molar volumes of transfer (VoΦ,tr) have been determined for various solutions of glycine, glycylglycine and glycylglycylglycine in aqueous nortriptyline hydrochloride. In addition, using speed of sound data, apparent molar isentropic compression (Ks,Φ), limiting apparent molar isentropic compression (Kos,Φ) and partial molar isentropic compression of transfer (Kos,Φ,tr) have been calculated. Pair and triplet interaction coefficients are also determined from VoΦ,tr values using McMillan-Mayer theory. Further, apparent molar expansibility (EoΦ) and Hepler's constant values ∂EoΦ∂TP have been evaluated to assist the interpretations earned from the volumetric and acoustic analysis. The viscosity coefficients A and B, viscosity B-coefficient of transfer (Btr) and temperature derivative of B-coefficients (dB/dT) have been determined from viscosity data. The results were interpreted in terms of different kinds of intermolecular interactions present in the ternary systems (amino acid/peptides + water + nortriptyline hydrochloride) through a cosphere overlap model. The Hepler’s constant and temperature derivative of B-coefficients (dB/dT) confirms the structure breaking nature of the solute.