Question

I am trying to work backwards on a serial dilution.

If my diluted sample has a concentration of 21.2 uL/mL and it is a 1:625 dilution, what would the concentration of the original stock be?

Answer 1

In serial dilution, the concentration decreases by the same factor in every successive step. In serial dilutions, you multiply the dilution factors for each stem.

In serial dilutions, concentration of the diluted smaple is obtained by multiplying the concentraion of stock solution with the dilution factor, i.e.,

conc. of diluted sample = Dilution factor x conc. of stock solution

As given in the question,

concentration of diluted sample = 21.2 uL/mL

dilution factor = 1 : 625

therefore,

21.2 uL/mL = 1/625 x conc. of stock solution

conc. of stock solution will be = 21.2 x 625 = 13250 uL/mL = 13.25 x 10³ uL/mL