Part B: Quantitative determination of carbohydrates
Materials and reagents
1. 2mM glucose
2. Sugar samples (unknown concentration)
3. Dinitrosalicylic acid reagent. Weigh 5g of 3, 5-dinitrosalicylic acid and
dissolve in 1 litre of 4% (w/v) sodium hydroxide.
4. 40% (w/v) sodium potasstium tartrate solution
Equipments and supplies
1. Water bath: set at 90 – 95oC.
2. Ice bucket
3. Spectrophotometer
4. Test tubes
5. 1 and 5ml pipettes
Experimental procedure
1. Bring 10 test tubes and add the reagents as shown in Table 2.2.
2. Mix the components thoroughly.
3. Boil in water bath (90 – 95oC) for 5min.
4. Optional: Add 0.5ml of 40% sodium potassium tartrate (Rochelle salt)
solution to stabilise the colour.
5. Allow the reaction samples to cool down at room temperature in an ice
bucket.
6. Read absorbance at 540nm using test tube no. 1 as a blank.
7. Plot standard graph between A540 and amount of glucose (mg).
8. Find out amount of glucose sample and calculate as %(w/v).
9. Determine whether or not the use of wavelength at 540nm is appropriate
by varying the wavelength, i.e., from 400 to 700nm and measuring the
absorbance.