Biuret test is not given by:

Biuret test is used to detect the presence of peptide bonds ($-\text{CO}-\text{NH}-$).Proteins and polypeptides have peptide bonds. Urea (${\text{NH}}_2{\text{CONH}}_2$) also gives a positive biuret test upon heating because it forms biuret.Carbohydrates do not contain nitrogen or peptide linkages and therefore do not give the Biuret test.