DNS METHOD FOR GLUCOSE ESTIMATION(WRITTEN FORMAT). PDF

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THE DOCUMENT HAS THE WRITTEN METHOD OF THE PRACTICAL : -
ESTIMATION OF GLUCOSE BY DNS METHOD....

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Experiment No. Date:

ESTIMATION OF REDUCING SUGARS BY DNSA REAGENT

Aim To estimate the amount of reducing sugars present in the given sample by DNSA method. Principle Sugars with reducing property arising out of the presence of a potential aldehyde or keto group are called reducing sugars. Ex. Glucose, galactose, lactose, maltose etc. 3,5 dinitrosalicylic acid (DNSA) is reduced to 3-amino5-nitrosalicylic acid in the presence of reducing sugars in an alkaline solution. The reducing sugar is oxidized to sugar acid and Rochelle’s salt reduces the tendency to dissolve oxygen by increasing the ion concentration in the solution. Phenol increases the amount of color produced during the color-developing reaction. Sodium bisulphite stabilizes the color obtained and reacts with any oxygen present in the medium. Alkaline medium (NaOH) is required for the red-ox reaction between DNSA and glucose, or other reducing sugars.

Materials  Dinitrosalicylic acid reagent (DNSA reagent): Dissolve by stirring 1 g dinitrosalicylic acid, 200 mg crystalline phenol and 50 mg sodium sulphite in 100 ml of 1% NaOH. Store at 4ºC.  40% Rochelle salt solution (Potassium sodium tartarate).  0.1N NaOH Procedure 1. Pipette out 3 ml of the unknown solution. 2. Add 3 ml of DNSA reagent to it. 3. Heat the contents in a boiling water bath for 5 min.

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When the contents of the tube are still warm, add 1 ml of 40% Rochelle salt solution. 5. Cool the solutions and read the intensity of the dark red color at 510 nm. 6. Run a blank and also a series of standards using glucose (0 to `250 µg) and plot the standard graph.

Result...