5% Phenol is being used for the method while 90-96% sulfuric acid is used. For the standard curve you can go for u Molar concentration of glucose. 

Dear Sagar,

Find in attached, a chapter on carbohydrate, color reactions.

You'll find in:

MATERIALS

Phenol 5%: Redistilled (reagent grade) phenol (50 g) dissolved in water and diluted to one litre. Sulphuric acid 96% reagent grade.

Standard glucose: Stock—100 mg in 100 mL of water. Working standard—10 mL of stock diluted to 100 mL with distilled water.

PROCEDURE

1. Follow the steps 1 to 4 as given in anthrone method for sample preparation.

2. Pipette out 0.2, 0.4, 0.6, 0.8 and 1 mL of the working standard into a series of test tubes.

3. Pipette out 0.1 and 0.2 mL of the sample solution in two separate test tubes. Make up the volume in each tube to 1 mL with water.

4. Set a blank with 1 mL of water.

5. Add 1 mL of phenol solution to each tube.

6. Add 5 mL of 96% sulphuric acid to each tube and shake well.

7. After 10 min shake the contents in the tubes and place in a water bath at

25–30°C for 20 min.

8. Read the colour at 490 nm.

9. Calculate the amount of total carbohydrate present in the sample solution using the standard graph.

Thank you Talaat for your answer.

I would like to know about the role of Phenol in this assay. It seems that color is observed after addition of sulfuric acid and phenol intensify that color. Other than that, what is the role of phenol in this reaction?

Dear Sagar,

Thank you too. The  PRINCIPLE of using phenol in this assay is:

In hot acidic medium glucose is dehydrated to hydroxymethyl furfural. This forms a green coloured product with phenol and has absorption maximum at 490 nm.

Best wishes

Hello everyone,

I have a question. I'd like to  now what is the color standard glucose solution for calibration curve to measure Carbohydrate in soil? 

Thank you,

hi. I got a question. What if we only use water as a blank. Does it makes any large different? Because i still got a nice linear line of standard calibration curve.