I used two concentrations of glucose 0-1 mg/ml and 0-25 mg ml. The problem is that the higher concentrations are similar in color and the lower concentrations a clear difference can be noticed. This situation has led me to believe that may DNS method may be used on very low glucose concentrations. However, I am not sure and I am really in need of your expert opinions.
Preparation of DNS: Mix 30 g of sodium potassium tartarate with 1 g DNSA and 1.6 g of NaOH. Make the solution up to 100 ml with distilled water.
Preparation of glucose standard: 10g anhydrous glucose is dissolved in distilled water and then raised the volume to 100 ml with distilled water. 1 mg/ml was prepared by taking 1 ml from the original stock solution and adding it to 99 ml ddH2O.
I learned when I was in Spain this method. Levels to mesure glucose in water with good lectures are between 0.2mg/L-2mg/L.
If you have a problem with high concentrations, you have to make dilutions in order to achieve a concentration between the upper and lower limits for this method. It's an SOP in chemical analyses. It is the only way to resolve this problem. Of course in the final calculations, the dilutions must be taken into account.
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