What is Barfoed's test and its principle?
This test is a specific test for monosaccharides.
This test is also a copper reduction test but differs from Fehling's and Benedict's test in the medium of reduction. The reduction takes place in acidic medium and unlike Benedict's and Fehling's test where we learnt that reduction takes place in alkaline medium. Only strong reducing agents can reduce cupric ions in acidic medium and since monosaccharides are strong reducing agents, they give this test.