1. Quantitative analysis of Carbohydrate
Total soluble carbohydrate
Reducing carbohydrate
Aldo reducing carbohydrate
Quantitative analysis of Carbohydrate

2. Extraction of soluble carbohydrate
Accurately weighed sample
Boiling 80% neutral ethanol/6h
Filter
Complete to 50ml in volumetric flask

3. Phenol-sulfuric acid method
1 ml extract + 1 ml 5%phenol then 5 ml sulfuric acid conc.
Distilled water as blank sample
Standard curve is done by pure glucose.
Measuring in spectrophotometer at 490 nm.

4. Total reducing sugars Schoorl method (volumetric method)
Reducing sugars + Cu++ (more than enough to oxidize all available reducing sugars)→ R-COOH + Cu2O↓ (equivalent to the amount of sugars)
Cu++ (the excess) + KI I2 (equivalent to the amount of excess Cu++ ) + K2SO4
I2 +Na2 S2O3 → 2I−+ Na2S4O6 (Titration from blue to colorless in presence of starch indicator)
H2SO4 dil.

5. Total reducing sugars Colorimetric method
R-CHO + Cu++ → R-COO− + Cu2O↓ (weight)
Cu2O↓ + molybdic → blue color
The intensity of the color is related to the concentration of the sugars.
Ferricyanide (yellow; measured at 420 nm) is reduced by sugars to Ferrocyanide (colorless) in relation with the concentration

6. Aldo reducing sugars Iodine in alkaline medium
I2 + NaOH → NaOI (Hypoiodide; a weak oxidizing agent that can oxidize only aldosugar but not ketosugars; should be more than enough to oxidize all available aldosugars)
R-CHO + NaOI → R-COONa
NaOI (excess) + H2SO4 → I2 (equi. to the excess)
I2 +Na2 S2O3 → 2I−+ Na2S4O6 (Titration from blue to colorless in presence of starch indicator)

7. Schoorl method Na2S2O3 (0.0901N)
10 ml sugar solution (or water in the blank)
Then 10 ml Fehling’s mixture
Then heating 2 min. then cooling
Then adding 10 ml KI + 10 ml H2SO4 dil
Then 2 ml starch indicator
Titration from blue to colorless
flask

8. Iodine alkaline Na2S2O3 (0.0901N)
10 ml sugar solution (or water in the blank)
Then 2 drops NaOH + 10 ml iodine solution
Let in dark place for 2 min.
Then adding 10 ml H2SO4 dil.
Then 2 ml starch indicator
Titration from blue to colorless
flask

9. Calculation
mg/l = (Vb-Vs) х N х 10 х 9 х 100