The Benedict’s test is a simple laboratory test used to detect reducing sugars and some aldehydes.
Definition
Benedict’s test uses Benedict’s reagent, which is a blue solution containing copper(II) sulfate, sodium carbonate, and sodium citrate.
Principle
- Reducing sugars (like glucose, fructose, lactose, maltose) and aldehydes can reduce the copper(II) ions in Benedict’s reagent to copper(I) oxide.
- This reduction occurs in alkaline medium provided by sodium carbonate.
- Sodium citrate keeps the copper ions in solution until the reaction takes place.
Observation
- When the test solution is heated with Benedict’s reagent, the blue solution changes color depending on the amount of reducing sugar present:
- Green (low amount)
- Yellow
- Orange
- Brick-red (high amount, due to copper(I) oxide precipitate).
Uses
- To detect reducing sugars in urine (important in diabetes testing).
- To distinguish between reducing and non-reducing sugars.
- To identify the presence of aldehyde groups in certain compounds.