The estimation of protein by the biuret and Greenberg methods

Abstract

For the estimation of small amounts of protein in biological fluids such as serum, urine and cerebrospinal fluid, as well as in certain foods such as milk, there have been many attempts to utilize colour tests. Perhaps the two most important of these are the biuret test, and the test for tyrosine introduced by Folin and his colleagues, and applied to serum, albumin and globulin by Fine [1935] applied the biuret test to these two serum proteins. The colour produced was matched in a colorimeter against that produced by a standard serum of which the protein content had been determined by Kjeldahl estimations. No correction factor was employed to distinguish between albumin and globulin, since equal weights of these were stated to produce equal intensities of colour.