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molar and percentage dilution help


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#1 friend26

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Posted 17 March 2010 - 09:55 AM

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..

#2 pito

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Posted 17 March 2010 - 10:01 AM

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

If you don't know it, then ask it! Better to ask and look foolish to some than not ask and stay stupid.


#3 friend26

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Posted 17 March 2010 - 10:19 AM

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


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.

#4 pito

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Posted 17 March 2010 - 10:42 AM

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 10ÁM 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.

If you don't know it, then ask it! Better to ask and look foolish to some than not ask and stay stupid.


#5 friend26

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Posted 17 March 2010 - 11:12 AM

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 10ÁM 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.

#6 mdfenko

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Posted 17 March 2010 - 12:12 PM

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.

Edited by mdfenko, 17 March 2010 - 12:14 PM.

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