PHASE-BEHAVIOR OF ALPHA-AMINO-ACIDS IN MULTICOMPONENT AQUEOUS ALKANOLSOLUTIONS

A model describing the partitioning behavior of alpha-amino acids in s ystems containing water and partially miscible alkanols is presented. It incorporates a relationship expressing the solubilities of amino ac ids in miscible aqueous alkanol solutions and makes use of the phase b ehavior of the solute-free solvent system and the solubilities of amin o acids in the pure solvent components. The solubilities of several am ino acids in aqueous ethanol and isomeric propanol solutions and their partition coefficients in the 1-butanol + water system were taken fro m the literature and could successfully be described with a single, am ino acid specific, ternary interaction parameter. it is demonstrated t hat this parameter is related to well-established hydrophobicity scale s for amino acid side-chain moieties. Without additional parameters th e partition coefficients of amino acids in 1-octanol/water were predic ted from the model and compare well with literature values. The extens ion of the model to multicomponent solvent systems is straightforward and was demonstrated for the case of the ternary solvent system water + ethanol + 1-butanol.