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.
- 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).
- Follow, steps 1 to 3 as in Nelson-Somogyi's method to extract the reducing sugars from the test material.
- 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.
- Add 3 mL of DNS reagent.
- Heat the contents in a boiling water bath for 5 min.
- When the contents of the tubes are still warm, add 1 mL of 40% Rochelle salt solution.
- Cool and read the intensity of dark red colour at 510 nm.
- Run a series of standards using glucose (0–500 µg) and plot a graph.
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"
1. Miller, G.L. (1972). Anal. Chem., 31, p. 426.
2. Internet Sources