In this article we will discuss about the three main tests for lipids:- 1. General Test for Lipid 2. Solubility Test for Lipid 3. Emulsification Test for Lipid.
General Test for Lipid:
1. Sudan III test Procedure:
Take 0.5 ml ether or chloroform in a test tube and add 0.5 ml sample—drop by drop till the sample is fully dissolves. Add one drop of Sudan III reagent.
Observation:
Red colour appears.
Inference:
The sample contains fat.
2. Acrolein test:
Procedure:
Take 0.5gm powdered sodium bi-sulphate (NaHSO4) or potassium bi-sulphate (KHSO4) in a clean dry test tube, add 3 to 4 drops of sample. Mix thoroughly and heat.
Observation:
An irritating smell of acrolein is felt.
Inference:
Sample contains fat.
Solubility Test for Lipid:
Procedure:
Take five test tubes marking A, B, C, D, E. Put 5 ml—water, absolute alcohol, ether, chloroform and benzene one in each test tube. Add 3 to 4 drops of sample in each test tube, shake thoroughly, allow to stand.
Observation:
(1) In test tube A drops of oils are seen floating on the surface of water,
(2) In test tube B oil drops settle at the bottom of alcohol,
(3) In test tubes C, D and E the sample is mixed.
Inference:
The sample contains fat, as it is not soluble in water (test tube A) but soluble only in organic solvents (test tube B, C, D, E) and sinks to the bottom in alcohol (B).
Emulsification Test for Lipid:
Procedure:
Take 3 ml sample in a test tube, add 2 drops of oleic acid, shake well. Add 2 drops of the mixture to another test tube containing 3 ml 10% caustic soda.
Observation:
Emulsion is formed (acid neutralize alkali forming soap).
Inference:
The test sample contains fat.