Partition coefficients and solubilities of alpha-amino acids in aqueous 1-butanol solutions

The partition coefficients of seven alpha-amino acids in the system water + 1-butanol have been measured at 25 degrees C from the very dilute region up to saturation. The solubilities of these amino acids in the pure solvents and in the miscible composition range of the solvent system have also been studied in this work. It was found that the partition coefficients of the amino acids and the composition of the phase-partitioning system are strongly dependent on the amino acid concentration and on the chemical nature of their side-chain moiety. The experimental data were successfully correlated with a thermodynamic model which describes conveniently defined excess solubilities via a simple excess Gibbs energy model having a single amino acid specific parameter. In addition, a simple method for the estimation of the solubility of amino acids in pure alkanols is presented.