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(II) acetate to copper(I) oxide (Cu₂O), which forms a brick-red precipitate.^[1][2]

RCHO + 2Cu²⁺ + 2H₂O → RCOOH + Cu₂O↓ + 4H⁺

Barfoed's test

Positive result in Barfoed's test
Classification	Colorimetric method
Analytes	Monosaccharides

(Disaccharides may also react, but the reaction is much slower.) 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,^[3] may interfere.

Its author is the Danish chemist Christen Thomsen Barfoed^[1] and it is primarily used in botany.^{[citation needed]}

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 copper (II) acetate in 1% acetic acid solution.^[4] The reagent does not keep well and it is therefore advisable to make it up when it is actually required.^[5]

Procedure

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