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Glucose and other reducing sugars

Benedict's Solution or Quantitative Benedict's solution have been widely used to detect and measure concentrations of reducing sugars.The method described here can detect lower concentrations of reducing sugars using DNSA reagent.

On boiling with reducing sugars 3,5 dinitrosalycylic acid (DNSA) reagent changes from yellow to red.

Small volumes of the reagent and test sample are boiled for 5-10 minutes, then diluted with water and the absorbance read using the green LED of the colorimeter.

Concentrations of reducing sugar down to below 0.5mM, (90µg of glucose/cm3), can be detected using this test. Small volumes of test solutions can be used, (typically 0.3cm3 for a standard cuvette).

Safety

eye-protection
caution
 WEAR EYE PROTECTION
TAKE CARE WITH BOILING WATER

DNSA reagent contains 0.4M NaOH
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Results

    DNSA
    The test result with no glucose was used to calibrate the colorimeter instead of water.
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Methods

  • Add 0.3cm3 of the sample to be tested to 0.3cm3 of DNSA reagent in a test tube.
  • Stand the test tube in boiling water for 5 -10 minutes.
  • Add 3cm3 of water and read absorbance with green light.
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