Volumetric, compressibility and conductometric studies of L-histidine in aqueous poly ethylene glycol solutions at different temperatures

Abstract

Polymers are a versatile class of materials that have a wide range of applications, due to their unique physical and chemical properties. In this study, the effect of molar mass of PEG and temperature on the thermodynamic properties of aqueous solutions of L-histidine, has been studied. For this purpose, density, sound velocity and specific conductivity for solutions of L-histidine in pure water and in aqueous solutions of 0.02 w/w of PEG400, PEG2000 and PEG6000 have been measured at T = (298.15, 308.15 and 318.15) K. From the values of experimental density and sound velocity, the apparent molar volume, ɸ ʋ and apparent molar isentropic compressibility, ɸ K were calculated and extrapolated to infinite dilution. The transfer apparent molar volume at infinite dilution, ɸ and the transfer apparent molar isentropic compressibility, ɸ of L-histidine from water to aqueous PEG solutions have been studied. Also, by using of the measured specific conductivity for the investigated solutions in this work, molar conductivity Λ was calculated. The results show that the values of Λ for all the examined systems decrease with the increase in the concentration of amino acid.