Benedict’s test for Glucose Procedure

In this benedict’s test for glucose procedure post we have briefly explained benedict’s test principle, objectives, requirements, benedict’s test method procedure, uses and limitations.

Benedict's test method

Benedict’s test method is a straightforward chemical procedure for detecting reducing sugars. Carbohydrates with a free aldehyde or ketone functional group in their chemical structure are known as reducing sugars. Monosaccharides like glucose and fructose, as well as disaccharides like lactose and maltose, are among them. Some sugars, such as glucose, are known as reducing sugars because they may transfer hydrogen’s (electrons) to other molecules through a process known as reduction.

A reduction reaction occurs when reducing sugars are combined with Benedict’s reagent and heated, causing the Benedict’s reagent to change colour. Depending on the amount and type of sugar, the colour can range from green to dark red (brick) or rusty-brown. Benedict’s reagent is the solution used to detect simple carbohydrates like glucose in Benedict’s test method. It’s a vivid blue solution made by combining distilled water with copper sulphate pentahydrate (CuSO4. 5H2O), sodium citrate (Na3C6H5O7), and sodium carbonate (Na2CO3).

Principle

Benedict’s test method is carried out by heating the reducing sugar in the presence of Benedict’s reagent. The presence of alkaline sodium carbonate transforms sugar to enediols, a powerful reducing agent. Due to the development of cuprous oxide, the mixture will change colour from blue to brick-red precipitate during the reduction phase (Cu2O). Cupric (Cu2+) or copper (I) copper is converted to cuprous (Cu+) or copper (I) copper (II). Cuprous oxide, which is red in colour, is insoluble in water and must be separated. When the sugar content is high, the colour turns crimson and the amount of the precipitate grows.

Requirements

5 % Glucose

Anhydrous sodium carbonate:100 gm

Sodium citrate: 173 gm

Copper (II) sulfate pentahydrate: 17.3 gm

Benedict's test for Glucose Procedure

2 mL (10 drops) Benedict’s reagent, pipette into three clean and dry test tubes. In each test tube containing Benedict’s reagent, add approximately 1ml of each of the test solutions and water. Heat the mixture directly over the flame or in the test tubes in a boiling water bath for 3-5 minutes. Look for colour changes in the solution or the production of precipitate in the  tubes.

Interpretation

Benedict’s test method is positive when the colour of the precipitate changes from blue to brick red (glucose). Benedict’s test method was negative: there was no change in colour (sucrose) or water. Because the intensity of the red colour and the volume of precipitate alter as the concentration of reducing sugar in the solution changes, the result can also be interpreted as:

Benedict’s test
Benedict’s test

Benedict’s test method: Benedict’s test for glucose procedure

Applications

1. Benedict’s test method is most commonly used to detect the presence of simple carbohydrates in an unidentified analytes. Benedict’s test method can be used to look for free aldehyde or ketone functional groups in reducing sugars. A monosaccharide or a disaccharide might be used as the reducing sugar.

Limitations

1. Benedict’s test method will not yield positive findings for all disaccharides. The disaccharides’ ability to produce favourable results is limited. Benedict’s test method can be performed to check for glucose in the urine, although it is not approved or utilised to diagnose diabetes mellitus.

Further Readings

Reference