The Estimation of Amino Acid Nitrogen in Animal Tissues

Of the existing methods for the determination of amino acid nitrogen in animal tissues, those of Folin and Denis (1) and of Van Slyke (2) are best known and most extensively employed. Both of them are long and tedious and call for rather large tissue samples. Also methyl alcohol containing zinc chloride is employed as an extractive by Folin and Denis and ethyl alcohol as a protein precipitant by Van Slyke. In both cases there are grounds for believing (1, 3-6) that some of the amino acids are lost in the treatment with alcohol. An attempt has therefore been made to develop a method which would be free from these disadvantages. The one to be described is a modification of the GreenwaldBock-Blau (5-7) technique for the determination of the amino acid content of blood. It has been used by the author primarily for the analysis of liver and muscle.