Xanthoproteic Test key words tyrosine, tryptophan

Xanthoproteic Test

This test will determine if residues of tyrosine or tryptophan are present. The solution to be tested is treated with concentrated nitric acid, which will nitrate the benzene riugs of those residues. The nitrated aromatic ringR are yellow in color and are (:alled Xanthoproteic acids (Xantho, = yellow, Greek). If base is added. the color becomes more intense and the color will shift more to orange.

Procedure

Carefully add 1 ml of concentrated nitric acid to 2 ml of amino acid solution in a test tube. Stir well with a glass stirring rod and heat.