Question

The molecular weight of vincristine, a pharmaceutical drug, is 923.04 g/mol. It is supplied in 1 mg per vial. You want to treat your culture cells with a final concentration of 17 hM vincristine and will need 15 mL of cells for your experiment. You only want to add 20 mL of vincristine solution to your cells. What concentration should you make your stock solution of vincristine in order to make this 20 uL addition? Please show all work

Answer 1

First we shall convert all units to the same prefix, giving molarity in mM and volume in mL:

1 ul = 0.001 mL

17 nM = 17 x 10ˉ⁶ mM

We can calculate the concentration of stock solution using the following equation:

MiVi = MfVf

Where:

Mi - Initial molarity
Vi - Initial volume
Mf - Final molarity
Vf - Final Volume

Substituting the values we get:

Mi x 15 mL = 17 x 10ˉ⁶ mM x 0.02 mL

Rearranging to give an equation for Mi we get:

Mi = (17 x 10ˉ⁶ mM x 0.02 mL) / 15 mL = 2.27 x 10ˉ8 mM

The initial concentration of the stock solution is 2.27 x 10ˉ8 mM.

If you would prefer to give your answer in nM:

2.27 x 10ˉ2 nM.