Extraction Equilibria of Amino Acids with Quaternary Ammonium Salt

Abstract

The extraction equilibria of various amino acids with tri-n-octylmethylammonium chloride (TOMAC) were studied in the high pH range. TOMAC reacted with the anion of amino acid and OH^– according to the stoichiometric ratio determined by ionic valency. The extraction equilibrium constants K_A of various amino acids differed considerably and could be correlated well with each hydrophobicity scale. The highest K_A value obtained for tryptophan was larger than the lowest value for glycine by a factor of about 260. These findings suggested that separation of amino acids is possible by utilizing the differences in K_A values. The extraction equilibrium constants of inorganic anions which were present in the fermented broth was comparable to those of amino acids exhibiting a low degree of extraction.