Biuret test is used for the detection of :

The Biuret test is a chemical test used for detecting the presence of peptide bonds, indirectly protein, as the proteins are made up of amino acids connected together with peptide bonds. In the presence of peptides, a copper(II) ion forms a violet-colored coordination complex in an alkaline solution. The Biuret reaction can be used to assess the concentration of proteins because, peptide bonds occur with the same frequency per amino acid in the peptide.