# Please help me determine if this math for creating a stock solution and drug tre - (Nov/07/2018 )

Hi All,

I am new in my lab and having trouble figuring out how to create a stock solution of powdered Cisplatin (1g in a bottle).  And from there, determining how much of the stock I must add to media in order to treat my cells.

The molecular weight of cisplatin is 300.01 g/mol. I attempted to do some of the math myself.

I know that a 10mM concentration can be made using 3mg/mL. By multiplying by 1000 (to scale down to uM), I end up with 10,000 uM = 3000 mg/1000mL. I need a final concentration of 30uM, so I divided by 333.33 to end up with 30uM = 9mg/3mL.

For the cell treatment, I need a concentration of 30 uM. Does this mean that I can add 27 uL of the 30 uM stock to 9mL of media?

Did I approach this math correctly?

-mugjay-

do you want 30 uM in the medium (ie final concentration)? if so, then you can't use a stock which is already at that concentration.

using the 10 mM stock, use the formula v1c1=v2c2 (v=volume, c=concentration) and rearrange so that you can determine how much of the stock to use: v1=(v2c2)/c1. make sure you are consistent with the units.

v1=(9000 ul x .03 mM)/10 mM=27 ul of the 10 mM stock

try not to overcomplicate (or overthink) the problem

-mdfenko-

Thank you so much for your help! You are right, I was overthinking.

-mugjay-