Barfoed's test
Chemical test for monosaccharides
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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+
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 mol dm-3 (molar) solution of copper(II) acetate in 1 % (0.17 mol dm-3) 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.