Partition of Amino Acids in Aqueous Two-Phase Systems Comprising Hydrophilic Organic Solvents and Salts

An aqueous two-phase system (ATPS) comprising a hydrophilic organic solvent and inorganic salt is advantageous because of its high polarity, low viscosity, and low cost. In this work, nine amino acids were partitioned in an ATPS that comprised hydrophilic organic solvents (2-methyl-2-propanol, tetrahydrofuran, and 2-propanol) and salts (Na2SO4, K2HPO4, and (NH4)2SO4). Amino acids were successfully extracted using different combinations of solvents and salts. The distribution ratio of amino acids in the ATPS containing ammonium sulfate increased with an increase in their hydrophobicity, except for that of alanine. The specific extraction of alanine was observed because of its salting-out effect in ammonium sulfate solution. The sulfate salts of amino acids exhibited higher extractability than amphoteric amino acids.