tests!!!

• Test for lipids in a sample :

  1. Dissolve solid samples in ethanol
  2. add an equal volume of water and shake
  3. positive result: milky white emulsion forms
• Benedict's test : sugar

  • add equal volume of Benedict's reagent to a sample.
  • heat the mixture in a water bath ( 100 degrees C for 5 mins )
  • Positive result : colour change form blue to orange and brick-red precipitate forms
• Benedict's test for non-reducing sugars

  1. negative result : Benedict's reagent remains blue
  2. hydrolyse no-reducing sugars by adding 1cm^3 of HCL , heat in water bath for 5 mins
  3. neutralise mixture with sodium carbonate solution
  4. proceed with benedict's test as usual
• Test for proteins in a sample :

  1. add biuret solution
  2. add drops of dilute copper sulfate solution , swirl to mix
  3. POSITIVE RESULT : colour changes from blue to purple NEGATIVE RESULT : solution remains bl