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Tuesday, April 26, 2011

Estimation of Reducing Sugar by Dinitrosalicylic Acid Method


Estimation of Reducing sugar by DNS Method

For sugar estimation an alternative to Nelson-Somogyi method is the dinitrosalicylic acid method—simple, sensitive and adoptable during handling of a large number of samples at a time.

estimation of reducing sugar by DNS method


MATERIALS
  • Dinitrosalicylic Acid Reagent (DNS Reagent)
Dissolve by stirring 1 g dinitrosalicylic acid, 200 mg crystalline phenol and 50 mg sodium sulphite in 100 mL 1% NaOH. Store at 4°C. Since the reagent deteriorates due to sodium sulphite, if long storage is required, sodium sulphite may be added at the time of use.
  • 40% Rochelle salt solution (Potassium sodium tartrate).
PROCEDURE

  1. Follow, steps 1 to 3 as in Nelson-Somogyi's method to extract the reducing sugars from the test material.
  2. Pipette out 0.5 to 3 mL of the extract in test tubes and equalize the volume to 3 mL with water in all the tubes.
  3. Add 3 mL of DNS reagent.
  4. Heat the contents in a boiling water bath for 5 min.
  5. When the contents of the tubes are still warm, add 1 mL of 40% Rochelle salt solution.
  6. Cool and read the intensity of dark red colour at 510 nm.
  7. Run a series of standards using glucose (0–500 µg) and plot a graph.

Estimation of reducing sugar



CALCULATION
Calculate the amount of reducing sugars present in the sample using the standard graph.which is given in the last post "Determination of Reducing Sugars by Nelson-Somogyi Method"

REFERENCES
1. Miller, G.L. (1972). Anal. Chem., 31, p. 426.
2. Internet Sources

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