Enthalpies of transfer of amino acids from water to aqueous solutions of sodium nitrate and sodium perchlorate at T=298.15 K

Enthalpies of solution of glycine, L-alanine and L-serine in water and aqueous solutions of NaNO3 and NaClO4 have been determined at T = 298.15 K with a calorimeter. Enthalpies of transfer (Delta H-tr) from water to aqueous solutions of salts were derived and interpreted in terms of electrostatic interaction and structural interaction. At,H decreases with increasing salt concentration in the composition range studied. The transfer enthalpies of amino acids from water to NaNO3 Solution and low concentration NaClO4 solution vary in the sequence L-serine < glycine < L-alanine while glycine < L-serine < L-alanine in NaClO4 solution above 2 mol kg(-1). The difference may be due to ion association at high concentration, weakening the interaction with L-serine more than with glycine. (C) 2005 Elsevier B.V. All rights reserved.