# I would like to make 1000x working stock for 40ng/ml solution?

I have 100mg of lyophilized drug I want to use in cell culture media. The established protocol we are using calls for 40ng/ml of this drug to 50ml final volume of media. What is a good way to go about diluting down to get to a 1000x working stock I could aliquot and freeze?

I appreciate any help!

Relevance
• 1 month ago

So, the 1000x stock would be 40 ug/mL. But to directly dilute the 100 mg of drug down to that would require a volume of 1X10^5 ug / 40 ug/mL = 2500 mL.

As long as the drug is stable in solution, I would probably make a 4 mg/mL stock by dissolving the 100 mg / 4 mg/mL = 25 mL. You could certainly aliquot this and freeze  this 4 mg/mL stock.

1 mL of this 4 mg/mL stock will make 100 mL of the 1000X working stock.

OR, you could dissolve the initial 100 mg of drug in 100 mL to give a 1.00 mg/mL stock, and aliquot and freeze that. 1 mL of this stock will make 25 mL of the 40 ug/mL (1000X) working stock.

That help?