BCH 2720 IBM

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BCH 2720 IBM

• Expt.1
• Qualitative Tests for Carbohydrates and Amino
  Acids

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1a Carbohydrates Characterization

• Molischs Test carbohydrate
• Barfoeds Test Monosaccharides and
  Oligosaccharides
• Seliwanoff Test Differentiation of Ketose from
  Aldose
• Iodine Test Cellulose, Starch, Dextrin

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Experiment 1 Qualitative Tests for Carbohydrates
I. Principle
1. Molischs Test - test for carbohydrates
a-naphthol
conc.H2SO4
Pentose/ Hexose
Furfural
5-hydroxymethyl furfural (Purple complex)
- H2O
2. Barfoeds Test - test for reducing sugars
- test for distinguishing monosaccharides and
disaccharides
Slightly acidic
Reducing sugar 2Cu2
2Cu oxidized sugar
Cu2O (brick red ppt)
3. Seliwanoff Test - test for distinguishing
ketose from aldose
resorcinol
conc. HCl
5-hydromethyl furfural
Ketohexose
red complex
dehydration
4. Iodine Test - test for starch
Starch I2
starch - I2 complex (deep blue)
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Barfoed's Test
RCHO    2Cu2    2H2O -----gt   RCOOH    Cu2O 
  4H Barfoed's reagent reacts with
monosaccharides to produce cuprous oxide at a
faster rate than disaccharides do
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Monosaccharide Disaccharides 

• Monosaccharide
• Glucose
• Fructose
• Disaccharides 
• Maltose
• Lactose
• Sucrose

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Ketone Adehyde
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Polysaccharide

• Starch
• Glycogen
• Cellulose

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Molischs Test

• Test for carbohydrate materials
• Using 2 ml of test solution in a test tube, add
  50 ?l of the ? 1-naphthol, mix and then allow 1
  ml of conc. Sulphuric acid to flow down the side
  of the inclined tube to layer under the mixture.
  Note the colour at the junction.

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Barfoeds Test

• Test for Monosaccharides and Oligosaccharides
• Using 0.5 ml of test solution, mix with 2.5 ml of
  Barfoeds solution in a test tube and boil for 15
  minutes. Note the time of first sign of
  precipitate appears. After 15 minutes, cool it
  down and observe the amount of precipitate in
  each tube.

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Seliwanoff Test

• Test for Differentiation of Ketose from Aldose
• Add 0.5 ml of the test solution to 2.5 ml of the
  Seliwanoffs reagent. Place the tubes in boiling
  water and note the results and continue heating,
  observe the colour change at 1 minute interval
  for 5 minutes.

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Iodine Test

• Test for Cellulose, Starch, Dextrin
• Add 50 ?l of aqueous iodine solution to 4 ml test
  solution. Record the colours observed. Then heat
  the tubes 5 mins, record the effect on the
  colours, cool the tube again and note the effect
  on the colours.

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1b. General Properties of amino acids

• The Ninhydrin Reaction oxidising agent
• (It reacts with ?-amino acids to produce a
  purple coloured compound to measure the amount of
  ?-amino acid in a sample.)

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The Ninhydrin Reaction

• Mix 1 ml of test solution and 50 ?l of ninhydrin
  reagent in a test tube. Boil for 5 minutes and
  observe the colour change. (Tyrosine, Tryptophan
  Proline)
• serial dilution of glycine

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Ruhemanns Pruple
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Lab Report

• Control is Water
• Date of Experiment 24 Jan 2006 (Tue)
• Date of Submission 10 Feb 2006 (Before 500p.m.)
  (Fri)
• Demonstrator in-charge Edmond
• Room no. MMW 612A

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Lab Report (Cont)

• Title and Introduction - 0.5 M
• Results 2.5 M
• Discussion 5 M
• Conclusion and Recommendation 1.5 M
• Reference 0.5 M