Investigation of amino acid partitioning in aqueous two-phase systems containing polyethylene glycol and inorganic salts

The partitioning behavior of three amino acids, L-tryptophan, L-phenylalanine, and L-tyrosine, has been studied in aqueous two-phase systems of polyethylene glycol (PEG6000) + salts + H2O at 298.15 K. The salts used were magnesium sulfate, sodium sulfate, and ammonium sulfate. The effects of tie line length, salt, and side chain structure on the partition coefficients of amino acids have been studied. The results showed that increasing amino acid hydrophobicity and tie line length led to a corresponding increase of the partition coefficients. In addition, we also showed that the partition coefficients of the amino acids in the systems containing Na2SO4 are also significantly greater than the other two salts. The experimental data are correlated using a modified virial-type model. Comparisons between model and experimental data reveal a good agreement.