Experiment: Detection of Lipids

 Experiment: Detection of Lipids

Aim

To detect the presence of lipids in the given sample using standard biochemical tests.

 Principle

Lipids are organic compounds that are insoluble in water but soluble in organic solvents such as ethanol. Their presence can be detected qualitatively by exploiting their physical properties, such as the formation of translucent grease spots on paper and the formation of a milky emulsion when an alcoholic extract is diluted with water.

 Requirements

 Given sample

 Filter paper / brown paper

 Ethanol

 Distilled water

 Test tubes

 Dropper

 Water bath (if required)

 Procedure

A. Grease Spot Test

1.  Take a small amount of the given sample.
2.  Rub the sample gently on a clean, dry filter paper or brown paper.
3.  Allow the paper to dry for a few minutes.
4.  Hold the paper against light and observe.

 B. Emulsion Test

1.  Take a small quantity of the given sample in a test tube.
2.  Add 2–3 ml of ethanol and shake well.
3.  Filter the mixture if necessary.
4.  Add an equal volume of distilled water to the filtrate.

 Observe the appearance of the solution.

 Observation 

Test	Observation	Test
Grease Spot Test	Formation of a translucent greasy spot on paper	Grease Spot Test
Emulsion Test	Formation of a milky white emulsion	Emulsion Test

 Result

The given sample shows positive tests for lipids, as evidenced by the formation of a translucent grease spot and a milky emulsion. Hence, lipids are present in the given sample.

(If no such changes are observed, lipids are absent.)

 Precautions

1.  Use clean and dry glassware.
2.  Handle ethanol carefully as it is highly flammable.
3.  Do not touch the filter paper with oily fingers.
4.  Avoid contamination of the sample.
5.  Dispose of chemicals properly after use.

 Viva-Voce Questions

 What are lipids?

 Why are lipids insoluble in water?

 Name any two biological functions of lipids.

 Why is ethanol used in the emulsion test?

 What does a milky emulsion indicate?

 Name any two lipid-rich food substances.

 Short Viva Answers:

 Lipids: Organic compounds including fats and oils, insoluble in water.

 Function: Energy storage, membrane structure, insulation.

 Ethanol role: Dissolves lipids to form an emulsion with water.