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Construction of Maltose Standard Curve by DNS Method
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Materials Required:

 

  1. Test/Boiling tubes
  2. Pipettes [glass/micropipette]
  3. Waterbath
  4. Colorimeter

 

Reagent Required:

 

  1. 3,5-dinitrosalicylic acid [DNS].
  2. Maltose working solution.
     

Preparation of Reagents:

 

  1. 3,5-dinitrosalicylic acid [DNS]:  About 1g of DNS is dissolved in 50ml of distilled water. To this solution add about 30g of sodium potassium tartarate tetrahydrate in small lots, the solution turns milky yellow in colour. Then add 20ml of 2N NaOH, which turns the solution to transparent orange yellow colour. The final volume is made to 100 ml with the distilled water. This solution is stored in an amber coloured bottle.
  2. Maltose working solution :  180mg of maltose is weighed and made up to 100ml with distilled water.

        
     

Procedure:

 

  1. Pipette out standard maltose solution in the range of 0.2, 0.4, 0.6, 0.8 and 1 ml, into 5 separate test tubes.
  2. A test tube containing a blank solution is also prepared.
  3. Using distilled water, bring the volume up to 2ml in each test tube, including the test tube containing the blank solution.
  4. Add 1 mL of DNS reagent to each tube and cover the test tubes with aluminum foil.
  5. Heat the contents in the test tubes in a boiling water bath for 5 minutes.
  6. Cool the test tubes to room temperature, after taking them out of the water bath.
  7. Then add 9ml distilled water to each test tube and mix well.
  8. Take 1ml from each test tube into different cuvettes and place each cuvette in a colorimeter and record the intensity of dark orange red colour at 540 nm as the 'absorbance' or OD.
  9. Plot a graph with the amount of maltose on X axis Vs OD at 540nm (A540nm ) on Y axis.

 

Result:


The intensity of the colour observed will be proportional to the concentration of maltose present in the solution.

     

 

 

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