Barfoedsche sample

The barfoedsche sample or Barfoed'sche sample is a method to remove monosaccharides (simple sugars), such as. B. glucose , galactose , mannose , fructose of di- , oligo- or polysaccharides . This evidence was found in 1873 by the Danish chemist Christen Thomsen Barfoed .

In this method, the Barfoed's reagent , a mixture of dissolved copper acetate , sodium acetate and acetic acid , is mixed with solutions of the sugars to be examined and heated in a water bath for a few minutes. If the given sample is a monosaccharide solution, a reddish color and reddish brown color quickly develop from copper (I) oxide (Cu ₂ O), which is produced by reducing the copper (II) ion of the Barfoed solution in a weakly acidic environment precipitates out as precipitation. Disaccharides only react after prolonged cooking, which enables them to be differentiated.

Reaction equation

The detection reaction is similar to the Fehling's test , but under acidic conditions. The aldehyde function of an aldose is oxidized to acid , copper in oxidation level + II is reduced to oxidation level + I:

{\ displaystyle \ mathrm {R-CHO + 2 \ Cu ^ {2 +} + 2 \ H_ {2} O \ longrightarrow R-COOH + Cu_ {2} O + 4 \ H ^ {+}}}

literature

VK Ahluwalia, S. Dhingra: Comprehensive Practical Organic Chemistry: Qualitative Analysis . Universities Press India 2004, ISBN 81-7371428-2 , p. 17 ( limited preview in Google book search).

Individual evidence

↑ C. Barfoed: About the detection of glucose alongside dextrin and related bodies . In: Journal for Analytical Chemistry . 12, No. 1, 1873, p. 27. doi : 10.1007 / BF01462957 .

[barfoed-1] C. Barfoed: About the detection of glucose alongside dextrin and related bodies . In: Journal for Analytical Chemistry . 12, No. 1, 1873, p. 27. doi : 10.1007 / BF01462957 .