 | This article needs additional citations for verification. (May 2015) |
 Positive Benedict's test | |
| Classification | Colorimetric method |
|---|---|
| Analytes | Reducing sugars |
Benedict's reagent (often called Benedict's qualitative solution or Benedict's solution) is a chemical reagent and complex mixture of sodium carbonate, sodium citrate, and copper(II) sulfate pentahydrate.[1] It is often used in place of Fehling's solution to detect the presence of reducing sugars. The presence of other reducing substances also gives a positive result.[2] Such tests that use this reagent are called the Benedict's tests. A positive test with Benedict's reagent is shown by a color change from clear blue to brick-red with a precipitate.
Generally, Benedict's test detects the presence of aldehyde groups, alpha-hydroxy-ketones, and hemiacetals, including those that occur in certain ketoses. Thus, although the ketose fructose is not strictly a reducing sugar, it is an alpha-hydroxy-ketone which results to a positive test because the base component of Benedict converts it into aldoses glucose and mannose. Oxidizing the reducing sugar by the cupric (Cu2+) complex of the reagent produces a cuprous (Cu+), which precipitates as insoluble red copper(I) oxide (Cu2O).[3]
The test is named after American chemist Stanley Rossiter Benedict.[4]
- ^ Robert D. Simoni; Robert L. Hill; Martha Vaughan (2002). "Benedict's Solution, a Reagent for Measuring Reducing Sugars: the Clinical Chemistry of Stanley R. Benedict". J. Biol. Chem. 277 (16): 10–11. doi:10.1016/S0021-9258(19)61050-1.
- ^ Collins Edexcel International GCSEBiology, Student Book (ISBN 978-0-00-745000-8) p.42-43
- ^ "Carbohydrates - Benedict's Test". dept.harpercollege.edu. Retrieved 2020-03-08.
- ^ Benedict, S. R. (1 January 1909). "A Reagent For the Detection of Reducing Sugars". J. Biol. Chem. 5 (6): 485–487. doi:10.1016/S0021-9258(18)91645-5.