Seliwanoff’s test

By careful choice of both the reaction conditions and the phenolic compound used, it may be possible to produce a colour that is characteristic of a particular carbohydrate or related group, so giving some degree of specificity to the method. Thus, Seliwanoff s test uses hydrochloric acid and either resorcinol or 3-indolylacetic acid to measure fructose with minimal interference from glucose. The colour produced by pentoses with orcinol (Bial s reagent) or p-bromoaniline is sufficiently different from that produced by hexoses to permit their quantitation in the presence of hexoses. However, none of the methods based on the formation of furfural or its derivatives can be considered to be entirely specific. 

Seliwanoff s test analy chem A color test helpful in the identification of ketoses, which develop a red color with resorcinol in hydrochloric acid. s3 liv3,nofs, test sellite liNORG chem A solution of sodium sulfite (Na2S03) used in the purification of 2,4,6-trinitrotoluene to remove unsymmetrical isomers. se,lTt ... 

There are a number of well-known tests for carbohydrates which depend on color formation. Thus in the Molisch test the substance is treated with mineral acid in the presence of a-naphthol and a characteristic purple color is formed. In Seliwanoff s test only ketoses give an immediate red color when warmed with mineral acid and resorcinol, and similarly ketoses give a blue coloration when warmed with sulfuric acid and diphenylamine in the Ihl-Pechmann reaction. 

Seliwanoff s test A test for ketose SUGARS in solution. The reagent used consists of resorcinol dissolved in hydrochloric acid. A few drops are added to the solution and a red precipitate indicates a ketonic sugar. The test is named for the Russian chemist F. F. Seliwanoff. 

Seliwanoff s test A biochemical test to identify the presence of ketonic sugars, such as fructose, in solution. It was devised by the Russian chemist F. F. Seliwanoff. A few drops of the reagent, consisting of resorcinol crystals dissolved in equal amounts of water and hydrochloric acid, are heated with the test solution and the formation of a red precipitate indicates a positive result. 

General color reactions of this type include the Molisch test with a-naphtfiol and concentrated sulfuric acid and the anthrone reaction with anthrone and sulfuric acid. The latter is used for quantitive colorimetric determinations. Reaction conditions can be chosen so that only ketoses react (HCl - - resorcinol, Seliwanoff s test) or only pentoses (HCl -b orcinol. Rial s test). These reactions help to distinguish the various sugars. 

Ketoses are dehydrated more rapidly than aldoses to give furfural derivatives that can be condensed with phenols. In the Seliwanoff test for ketoses, the aqueous carbohydrate sample is treated with 3 M hydrochloric acid containing resorcinol. A deep-red precipitate is formed, indicating the presence of ketose(s). The faster rate of dehydration of ketoses by HCl versus the dehydration of aldoses permits the specific detection of ketoses [10,11]. 

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