Qualtative Analysis of Lipids

QUALITATIVE ANALYSIS OF LIPIDS SOLUBILITY TEST: The test is based on the property of solubility solubility of lipids lipids in organic solvents and insolubility in water. PRINCIPLE:The oil will float on water because of lesser specific gravity. TEST:Take 3ml of solvents in each test tube and add 5 drops of sample.For water and ehanol,it is insoluble and for chloroform and ether,it is soluble and hence the given sample is lipid. TRANSPARENCY TEST: All the lipids are greasy in nature.Therefore the test may be taken as group test for lipids. PRINCIPLE:The oil does not wet the paper. TEST:Take 3ml of ether in a test tube and dissolve 5 drops of oil in tit.Put a drop of the solution on the filter paper and let it dry.A transluoent spot on the filter paper was observed and this indioats the greasy character of the lipid. EMULSIFICATION TEST: When oil and water,which are immiscible, are shaken together, the oil is broken up into very tiny droplets which are dispersed in water.This is known as oil in water  emulsion.The water molecule due to the high surface tensions have atendency to come together and form a separate layer.this is why the oil and water emulsion is unstable in the presence of substances that lower the surface tension of water.Eg:Sodium carbonate,soap,bile salts etc.The tendency of the water molecule to coalesce is decresed and the emulsion becomes stable.Since bile salts cause the greatest decrease in surface tension they are best emulsifying agents. TEST:Take 3ml of water and add 5 drops of sample.In another test test tube 10ml of water is added to ethanolic solution of o f lipid contents and are mixed and two layers ofare observed and this confirms the presence of lipids. TEST FOR UNSATURATION: The unsaturated fatty acids absorb iodine at th double bonds until all the double bonds are saturated with iodine.Hence the amount of iodine required to impart its colour to the solution is a measure of the degree of the fatty acids. TEST:Take 1ml of of choloroform and add a methanol and one drop of oil.to this add 1 drop of iodine.Chloroform dissolve sample give red colour which decolourises the iodine giving brown colour.This indicates the presence of fatty acids.

experiment SOLUBILITY TEST: Take 3 ml of solvents in each test tube and add 5 drops of sample. Water  Ethanol Chloroform ether  TRANSPARENCY TEST: Take 3ml of ether in a testtube and dissolve 5 drops of oil in it.put a drop of the solution on a filter   paper and let it dry EMULSIFICATION TEST: Take 3ml of water and add5 drops of sample.in another  test tube 10ml of water is added to ethanolic solution of lipid contents and are mixed TEST FOR  UNSATURATION: Take 1ml of chloroform and add a methanol and 1 drop of oil.to this add 1 drop of iodine. TEST FOR  CHOLESTROL: Spot cholesterol on a silica gel over aglass slide.air dry and add visualizing agent and plaoe the slide in an oven at a 100 centigrade TEST FOR FREE FATTY ACIDS: Dilute alkaline solution added to phenolphthalein solution until pink  color.then this solution is added to test tube containing sample.

observation

Inference The given sample is a lipid

Insoluble Insoluble Soluble soluble A translucent spot on the filter paper 

Indicates the greesy character of the lipid

2 layers are observed

Confirms the presence of   lipids

Chloroform dissolves sample to give red color  which decolorizes the iodine giving brown colour 

Indicates the presence of  fatty acids

Green color is formed

Indicates the presence of  cholestrol

The pink color is decolorized on addition to lipid.

Confirms the presence of  lipids.