Test for Proteins

• What is the test for proteins?

  Biuret test.
• What does biuret reagent contain?

  An alkali and copper(||) sulphate.
• What colour is biuret reagent?

  Blue.
• What is the method for the biuret test?

  Sodium or potassium hydroxide is added to the sample to make it alkaline, then a few drops of a very dilute copper(||) sulphate solution is added before gently mixing.
• What does the biuret reagent detect?

  Peptide bonds.
• What is the positive test result for proteins?

  The solution turns from blue to lilac/purple.