# molar and percentage dilution help - (Mar/17/2010 )

Hello,

I wanted to clarify something.

I am trying to prepare a 5mM stock solution of a drug, whose MW=1209.42g/l.

I have to prepare the dilutions s

o that the final DMSO % is not more than 0.2%, in 5ml media.

Below are my calculations.

Could someone please check and let me know, if I am doing correct.And suggest an easier way to do that. Especially if I need further dilutions, how will I do that.

5 mM stock solution,

0.005 x 1209.42=6.047 g/l

= 6.047 mg/ml

The tablet is in 10 mg, so

10 mg / 6.047 mg/ml = 1.64 ml

4. Filter sterilize it, in hood

All dilutions in RPMI +5 %FBS

5. 10uM(1/500 stock) = 10ul stock in 5 ml media

6. 5uM(1/1000 stock) = (5ul stock + 5ul DMSO) in 5 ml media

7. 2.5uM(1/2000 stock) = (2.5ul stock + 7.5ul DMSO) in 5 ml media

8. 1uM(1/4000stock) = (1ul stock + 9ul DMSO) in 5 ml media

Thanks a bunch..

Without checking everything I have the following question: mM is given in....

Check you calculations on the correct unit

(I didnt recalculate your number so they might be ok, but I do not understand how you speak of 5mM and dont even mention #mol/liter

pito on Mar 17 2010, 11:01 AM said:

Check you calculations on the correct unit

(I didnt recalculate your number so they might be ok, but I do not understand how you speak of 5mM and dont even mention #mol/liter

Here it is :

5mM = (5mmol/L)(1L/1000mL)(1mol/1000mmol)(1209.42g/mol) = 6.047mg/mL = (10mg/1640uL)(1000uL/1mL)

Does that answer your question. or is it wrong.

check your original post where you state that you have a MW of MW=1209.42g/l....

and whats the point of using 1L/1000mL ???? You can also multiply with 1.542 gram/1.542x1^-3 kg ....

5mol/l x 1209.42 g/mol = 6.047g/l and this is the same as 6.047 mg/ml

(I see where you got the (1L/1000mL).(1mol/1000mmol) from, but its kinda weird how you use it)

and if you have a tablet of 10mg then you indeed need 1.64ml (better is 1.65ml, check your calculation: 1/6.047 x 10= 1.653...)

ind indeed if you want to make a 10µM from 5mM you need to dilute it 500 times but not like you do it.

if you dilute somthing 1/2 you take 0.5liter of the stock and add 0.5liter of the dilutant....

maybe diluting 500 times doenst matter so much... I dont know how accurate it has to be for you.

pito on Mar 17 2010, 11:42 AM said:

and whats the point of using 1L/1000mL ???? You can also multiply with 1.542 gram/1.542x1^-3 kg ....

5mol/l x 1209.42 g/mol = 6.047g/l and this is the same as 6.047 mg/ml

(I see where you got the (1L/1000mL).(1mol/1000mmol) from, but its kinda weird how you use it)

and if you have a tablet of 10mg then you indeed need 1.64ml (better is 1.65ml, check your calculation: 1/6.047 x 10= 1.653...)

ind indeed if you want to make a 10µM from 5mM you need to dilute it 500 times but not like you do it.

if you dilute somthing 1/2 you take 0.5liter of the stock and add 0.5liter of the dilutant....

maybe diluting 500 times doenst matter so much... I dont know how accurate it has to be for you.

The how do you suggest to make a 5mM stock with 1209.4g, M,wt ( suppliedin 10mg form), to 10, 5, 2.5, 1uM , with a final volume of 5ml media, the drug needs to be dissolved in DMSO, with final concentration of DMSO being not mare than 0.2%

Will really appreciate your suggestions.

your calculations look mostly fine (pito is correct that you should make 1.65ml). you will be maintaining 0.2% dmso throughout. it would be more precise to add 10ul stock+dmso to 4.99ml medium.