The two main ways to test for lipids in a sample substance is through the Sudan Red test and the Grease Spot test. Sudan Red is a dye that is lipid soluble. Therefore, when Sudan Red is added to a sample that contains lipids, the dye will colour the lipids red. The Grease Spot test can also be used identify the presence of lipids in a sample. Lipids make unglazed paper, such as the outside of a paper bag, translucent.
- Skill level:
Things you need
- Sample for Testing
- Beakers or Droppers
- Sudan Red
- Brown Paper Bag
Use a cotton swab to apply a few drops of the sample to the paper bag.
Allow the sample to dry on the bag for several minutes.
Hold the paper bag up to a light after the sample has dried completely. If a grease spot remains, the sample contains lipids.
Measure 2ml of oil and 2ml of water.
Add the oil and water to the test tube.
Add 3 drops of Sudan Red.
Shake the test tube and observe. The Sudan Red will colour any lipids in the sample.
Tips and warnings
- During the Grease Spot test, make sure to allow all spots to dry thoroughly. Otherwise, you may think that a wet spot is really a grease spot.
- Be careful with the Sudan Red, because it can stain clothing.
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