Question

Hello,

In an experiment to determine the concentration of glucose in a sample, we are supposed to make a glucose assay with glucose solutions of known concentration. The absorbance for each solution of known concentration will be plotted, so that we can use the line of absorbance rates to later find the concentration of our unknown sample. We need to make our own dilutions for the assay.

We are given a stock glucose solution of 10mg/mL (1000mg/dL). My group wants to make solutions with concentrations 0mg/dL; 100mg/dL; 200mg/dL; 300mg/dL; 400mg/dL; and 500mg/dL. We are unsure of the best way to make the dilutions.

Would we make a 100mg/dL dilution be adding 1 part of stock and 9 parts deionized water? And a 200mg/dL dilution by adding 2 part stock and 8 parts deionized water; 300mg/dL as 3 parts stock and 7 parts deionized water, and so on? I'm unsure of how to do this.

Thank you!

Answer 1

For an absorbence measurement experiment, we hardly need 10 mL (1000 dL) of a solution. So, I am expressing a preocedure to make 1000 dL of the required solution.

Please use the formula,

S₁V₁ = S₂V₂

S₁ = strength of stock solution, i.e, 1000mg/dL.

V₁ = volume reqired (need to calculate as shown below)

S₂ = strength of solution you want to make (100mg/dL, 200mg/dL, 300mg/dL, 400mg/dL and 500mg/dL)

V₂ = volume of solution you want to make (1000 dL)

For preparing a 100mg/dL solution.

S₁V₁ = S₂V₂

=> 1000mg/dL * V₁ = 100mg/dL * 1000 dL

=> V₁ = 100 dL

Take 100 dL of the stock solution in a measuring flask and dilute it with deionised water upto 1000 dL.

Similarly, for 200mg/dL, take V₁ = 200 dL and dilute it with deionised water upto 1000 dL.

for 300mg/dL, take V₁ = 300 dL and dilute it with deionised water upto 1000 dL.

for 400mg/dL, take V₁ = 400 dL and dilute it with deionised water upto 1000 dL.

for 500mg/dL, take V₁ = 500 dL and dilute it with deionised water upto 1000 dL.

For making different amount of required solution (V₂), please follow the procedure as mentioned.