1. Expt.1: Qualitative Tests for Carbohydrates and Amino Acids
BCH 2720 IBM
Expt.1:
Qualitative Tests for Carbohydrates and Amino Acids

2. 1a: Carbohydrates Characterization
Molisch’s Test : carbohydrate
Barfoed’s Test : Monosaccharides and Oligosaccharides
Seliwanoff Test : Differentiation of Ketose from Aldose
Iodine Test : Cellulose, Starch, Dextrin

3. Experiment 1 I. Principle Qualitative Tests for Carbohydrates
1. Molisch’s Test
- test for carbohydrates
a-naphthol
Pentose/
Hexose
conc.H2SO4
Furfural
5-hydroxymethyl furfural
(Purple complex)
- H2O
2. Barfoed’s 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)

4. Barfoed's Test
RCHO  +  2Cu2+  +  2H2O ----->   RCOOH  +  Cu2O  +  4H+
Barfoed's reagent reacts with monosaccharides to produce cuprous oxide at a faster rate than disaccharides do

5. Monosaccharide & Disaccharides
Glucose
Fructose
Disaccharides 
Maltose
Lactose
Sucrose

6. Ketone & Adehyde

7. Polysaccharide
Starch
Glycogen
Cellulose

8. Molisch’s 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.

9. Barfoed’s Test Test for Monosaccharides and Oligosaccharides
Using 0.5 ml of test solution, mix with 2.5 ml of Barfoed’s 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.

10. Seliwanoff Test Test for Differentiation of Ketose from Aldose
Add 0.5 ml of the test solution to 2.5 ml of the Seliwanoff’s 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.

11. 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.

12. 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.)

13. 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

15. Ruhemann’s Pruple

16. Lab Report Control is Water Date of Experiment : 24 Jan 2006 (Tue)
Date of Submission: 10 Feb 2006 (Before 5:00p.m.) (Fri)
Demonstrator in-charge: Edmond
Room no. : MMW 612A

17. Lab Report (Con’t) Title and Introduction - 0.5 M Results – 2.5 M
Discussion – 5 M
Conclusion and Recommendation – 1.5 M
Reference – 0.5 M