Barfoed's test


Barfoed's test is a chemical test used for detecting the presence of monosaccharides. It is based on the reduction of copper acetate to copper oxide, which forms a brick-red precipitate.
The aldehyde group of the monosaccharide which normally forms a cyclic hemiacetal is oxidized to the carboxylate. A number of other substances, including sodium chloride, may interfere.
It was invented by Danish chemist Christen Thomsen Barfoed and is primarily used in botany.
The test is similar to the reaction of Fehling's solution to aldehydes.

Composition

Barfoed's reagent consists of a 0.33 molar solution of neutral copper acetate in 1% acetic acid solution. The reagent does not keep well and it is therefore advisable to make it up when it is actually required.

Procedure

2-3 drops of Barfoed's reagent is added to 1 mL of given sample in a test tube and boiled for 30 seconds and then allowed to cool. If a red precipitate occurs, a monosaccharide is present.