In this work, partitioning of amino acids such as glutamic acid, phenyl anine and tryptophan in aqueous and ionic liquid phases at 298.15 K and atmospheric pressure was measured. [C4mim][Tf2N] is used due can produce two phase with water rapidly. Studying the effect of liquid solution pH on amino acids partitioning shows that increasing of pH results in decreasing of amino acid partitioning coefficient. This phenomenon pertains to electrostatic interactions between cation of amino acid and anion of ionic liquid which reduces when pH increases. Considering the effect of pH, liquid-liquid equilibrium data of amino acids was obtained in a pH that owning maximum partioning coefficient. Chemical...