Carbohydrates - Barfoed's Test
Shows positive test for:
Reducing monosaccharides are oxidized by the copper ion in solution to form a carboxylic acid and a reddish precipitate of copper (I) oxide within three minutes. Reducing disaccharides undergo the same reaction, but do so at a slower rate.
How to perform the test:
One ml of a sample solution is placed in a test tube. Three ml of Barfoed's reagent (a solution of cupric acetate and acetic acid) is added. The solution is then heated in a boiling water bath for three minutes.
A positive test is indicated by:
The formation of a reddish precipitate within three minutes.
a negative test (left) and a positive test (right)