Barfoed’s Test- Definition, Principle, Procedure, Result, Uses


Barfoed’s test is a chemical test that detects the presence of reducing monosaccharides in a solution and distinguishes them from reducing disaccharides. Reducing sugars are those that can donate electrons to other molecules and reduce them. Monosaccharides are simple sugars that consist of one sugar unit, such as glucose and fructose. Disaccharides are sugars that consist of two sugar units linked by a glycosidic bond, such as sucrose and lactose.

Barfoed’s test is based on the reaction of reducing sugars with copper acetate in a dilute acetic acid solution. The copper acetate acts as an oxidizing agent that accepts electrons from the reducing sugars and forms a red precipitate of copper(I) oxide. The acetic acid provides an acidic pH that slows down the reaction of disaccharides, which need to be hydrolyzed first before they can react with copper acetate. Therefore, monosaccharides react faster than disaccharides and produce a red precipitate within 1-2 minutes, while disaccharides take longer than 3 minutes to produce a red precipitate.

Barfoed’s test is useful for identifying reducing monosaccharides and differentiating them from reducing disaccharides in a solution. However, it has some limitations, such as interference from chloride ions in urine samples and false positive results from high concentrations of disaccharides.