What is the anthrone test used for?

The anthrone test is a general test for all carbohydrates.

An anthrone is a planar tricyclic aromatic ketone. In the basic skeleton of an anthrone, the two aromatic rings are linked by a keto group and a methylene group (sp3 carbon) in such a way as to form a six-membered cyclic ketone in the middle of the condensed-fused ring system. Thus, the simplest Anthrone, anthracene-10(9H)-one, is formed by the reduction of the structure of anthracene-9,10-dione (anthraquinone) to form anthrone skeleton, which has one keto (C5O) group.

Anthrone is a tricyclic aromatic ketone that can be used, for example, for calorimetric determinations of carbohydrates in biological fluids. It can be synthesized by partial reduction of anthraquinone with several reagents, such as sodium hydrogen sulfite, tin chloride, or tin. In this test, carbohydrates also get dehydrated when they react with conc. H2SO4 to form furfural. This furfural reacts with Anthrone to give bluish green coloredcomplex.

Anthrone reagent: 2 g of Anthrone is dissolved in 1 liter of concentrated H2SO4. The freshly prepared reagent should be used for the test. Procedure and observations- Add 0.5-1 ml of the test solution to about 2 ml of anthrone reagent and mix thoroughly. Observe whether the colour changes to bluish-green. If not, examine the tubes again, keeping them in a boiling water bath for 10 min.

Limitations of Anthrone Test: The Anthrone test gives a negative result in samples that are carbohydrates like D-glucose phenylosazone and D-glucose phenylosotriaole but does not form furfural or hydroxy furfural in the dehydration step.