Biuret test for Protein
Quick revise

The solution you need to use for this is called Biurets solution.

In some schools, this will be given to you as one solution, which is copper sulphate blue in colour, but in most you will be given two solutions to mix together.

  • The first step is to add equal volumes (dropwise) of 1% copper sulphate (sometimes called Biurets A) and either 1% potassium hydroxide or sodium hydroxide (Biurets B) to a test tube.
  • After adding Biurets A and B, you'll have a lump of blue precipitate at the bottom of the test tube.
  • Hand-warm the precipitate until it becomes liquid (you can do this in a water bath set at 40).
  • The easiest test to do to see the positive result is to test egg white or milk. Add some of the egg white to the Biurets solution in the test tube and mix thoroughly while still hand warming. The blue colour will change to violet if protein is present. If protein is not present, the blue colour will remain.

This video shows the Biuret test for Protein


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