Calorimetric Determination of Glucose by the 3,5-dinitrosalicylic acid Method

1. Calorimetric Determination of Glucose by the 3,5-dinitrosalicylic acid Method • Several reagents have been employed which assay sugars by using their reducing properties. • This method tests for the presence of free carbonyl group (C=O), the so-called Reducing Sugars. • This involves the oxidation of the aldehyde functional group present in glucose and the ketone functional group in fructose. oxidation CHO COOH

2. Calorimetric Determination of Glucose by the 3,5-dinitrosalicylic acid Method • The chemistry of the reaction is complicated since standard curves do not always go through the origin and different sugars give different color yields. • The method is therefore not suitable for the determination of a complex mixture of reducing sugar.

3. Materials 1. Standard Glucose Solution: • 0.1g anhydrous glucose is dissolved in distilled water and then raised the volume to 100 ml with distilled water. 2. Dinitro salicylic acid reagent: a. Solution "a" is prepared by dissolving 300g of sodium potassium tartarate in about 500 ml distilled water. b. Solution "b" is prepared by dissolving 10 g of 3,5-DNS in 200 ml of 2N NaOH solution. c. The DNS reagent is prepared by mixing solutions a & b and raising the final volume to 1 litre with distilled water.

4. 60 5 55 10 50 45 15 40 20 35 25 30 Glucose (ml) 0 0.2 0.4 0.6 0.8 1 H2O (ml) 7 7 7 7 7 7 H2O (ml) 1 0.8 0.6 0.4 0.2 0 Shake Well COOL Read the Optical Density at 540 nm DNS (ml) 2 2 2 2 2 2

5. Results Samar A. Damiati