Does biuret test work for most proteins, if not which ones and why?

Biuret test does not work for all kinds of proteins. It only works with proteins and peptides that have 2 or more peptide bonds.

Explanation:

The Biuret test is used to determine proteins and polypeptides that contain 2 or more peptide bonds.

It is made of potassium hydroxide and cupric sulfate, along with sodium and potassium tartrate.

It consists of treating a protein with Cu ++ in alkaline medium, producing a violet coloration by forming a coordination complex between the Cu ++ and the free electron pairs of the nitrogens of the amino groups of the peptide junction. At least two peptide bonds are necessary for the reaction to take place.

Therefore, this test does not serve to determine the amount of amino acids and peptides with a single peptide bond such as: tyrosine (amino acid), tryptophan (amino acid), alanine (amino acid), aspartame (peptide)

the ratio of the conjugate base to the acid required to attain the desired ph.