Dosage Colorimétrique du Glucose

Mesure de l'analogue de la glycémie par la méthode DNS

Colorimetry Intermediate (High School) 60 min ~$10,00

Objectif

Déterminer la concentration en glucose par la méthode colorimétrique à l'acide dinitrosalicylique (DNS) et comprendre la chimie des sucres réducteurs.

Contexte

The DNS method is a classic colorimetric assay for reducing sugars. 3,5-dinitrosalicylic acid (yellow) is reduced by the free aldehyde group of glucose to 3-amino-5-nitrosalicylic acid (orange-red). The color change occurs upon heating, and the intensity at 540 nm is proportional to the reducing sugar concentration. This method is widely used in food science and fermentation monitoring.

Avertissements de sécurité

  • DNS reagent contains NaOH — corrosive to skin
  • Boiling water bath — handle tubes with tongs
  • Cool tubes before opening to prevent splattering
  • DNS reagent stains skin yellow

EPI requis

goggles gloves lab_coat

Matériaux

  • DNS reagent (100 mL)
    1% DNS in NaOH with sodium potassium tartrate
  • Glucose stock solution (100 mL)
    10 mg/mL in water
  • Unknown sugar solution (20 mL)
  • Distilled water (200 mL)

Équipement

Spectrophotometer or colorimeter Cuvettes Boiling water bath Test tubes (10) with caps Pipettes (1 mL, 5 mL) Ice bath Timer

Procédure

1

Prepare glucose standards: 0, 1, 2, 4, 6, 8, 10 mg/mL by diluting the stock solution.

10 min
2

Add 1 mL of each standard and the unknown to labeled test tubes. Add 1 mL of DNS reagent to each tube.

5 min DNS contains NaOH
3

Place all tubes in a boiling water bath for exactly 5 minutes. The color changes from yellow to orange-red.

5 min Use tongs for hot tubes
4

Transfer tubes immediately to an ice bath to stop the reaction. Cool for 2 minutes.

2 min
5

Add 8 mL of distilled water to each tube and mix well.

5 min
6

Measure absorbance at 540 nm. Zero with the blank (0 mg/mL glucose).

15 min
7

Plot the calibration curve and determine the glucose concentration of the unknown.

18 min

Résultats attendus

A linear calibration curve from 1–10 mg/mL glucose. The color intensifies from pale yellow (blank) to deep orange-red (10 mg/mL). Non-reducing sugars like sucrose give no color change.

Nettoyage

Neutralize DNS waste with dilute HCl before disposal. Clean test tubes immediately as dried DNS residue is difficult to remove.

Détails

Catégorie
Colorimetry
Difficulté
Intermediate (High School)
Durée
60 min
Coût estimé
$10,00
Étapes
7
Matériaux
4

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Frequently Asked Questions

What is the objective of Dosage Colorimétrique du Glucose?
Déterminer la concentration en glucose par la méthode colorimétrique à l'acide dinitrosalicylique (DNS) et comprendre la chimie des sucres réducteurs.
How difficult is Dosage Colorimétrique du Glucose?
This experiment is rated as Intermediate (High School). It takes approximately 60 minutes to complete.
What safety precautions are needed for Dosage Colorimétrique du Glucose?
Key safety precautions include: DNS reagent contains NaOH — corrosive to skin; Boiling water bath — handle tubes with tongs; Cool tubes before opening to prevent splattering.
What materials are needed for Dosage Colorimétrique du Glucose?
The main materials required are: DNS reagent, Glucose stock solution, Unknown sugar solution, Distilled water.
What results should I expect from Dosage Colorimétrique du Glucose?
A linear calibration curve from 1–10 mg/mL glucose. The color intensifies from pale yellow (blank) to deep orange-red (10 mg/mL). Non-reducing sugars like sucrose give no color change.