METHOD FOR SELECTIVE DETERMINATION OF TYROSINE AND PHENYLALANINE IN AQUEOUS SOLUTION

FIELD: analytical chemistry of organic compounds, amino acids. ^ SUBSTANCE: invention relates to a method for selective determination of tyrosine and phenylalanine in an aqueous solution that involves preparing an aqueous-saline solution of tyrosine and phenylalanine mixture, extraction of these amino acids with an extractant representing a mixture of hydrophilic solvents. Analysis of an organic phase involves addition of lithium sulfate as a desalting agent to an aqueous solution of amino acids analyzed in the amount 20-25 wt.-% to the solution mass. As an extractant the method involves using three-component mixture of hydrophilic solvent consisting of 45-45.5 wt.-% of isopropyl alcohol, 30-30.5 wt.-% of acetone and 24-25 wt.-% of ethyl acetate in the volume ratio of solvents mixture and aqueous-saline solution = 1:10. The potentiometric titration method is used for analysis of an organic phase. Proposed method provides the selective determination of tyrosine and phenylalanine in an aqueous solution by using liquid extraction and in enhancing precision of analysis. Invention can be used in development of processes for continuous fermentation of proteins. ^ EFFECT: improved assay method. ^ 1 tbl, 9 ex