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Calculation help

micromolar molar mg/ml solution

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6 replies to this topic

#1 Mad Researcher

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Posted 05 May 2018 - 05:12 PM

Hi,

 

I have to make a solution and add it to the complete growth media (CGM) at 10 µM concentration. 

The manufacturer says, to make the solution at 50 mg/ml working concentration. How can I calculate to get a concentration of 10 µM?

The final volume of the CGM with 10 µM concentration is 8 ml.

 

I think I can use C1V1 = C2V2, but I am confused with the units. 

 

Thanks.


Cheers,

Mad Researcher

#2 bob1

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Posted 05 May 2018 - 06:15 PM

To wok out the molarity you need to know the molecular mass of the solute. If you know this you can substitute this into the equation N = mass/molar mass to give you number of mol per volume. (hint - you know there are 50 mg in 1 ml.., just make sure you convert this to g or convert the g/mol unit for your chemical to keep the units consistent!)

 

Now, as you know C*V also equals N, so you can use this to your advantage...

 

N = C * V

N= 10 uM * 8

N= 80 uM  - this is the amount you want finally. From this you can also work

 

V= N/C

V= 80/ conc in uM of your solution.



#3 Mad Researcher

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Posted 05 May 2018 - 06:19 PM

To wok out the molarity you need to know the molecular mass of the solute. If you know this you can substitute this into the equation N = mass/molar mass to give you number of mol per volume. (hint - you know there are 50 mg in 1 ml.., just make sure you convert this to g or convert the g/mol unit for your chemical to keep the units consistent!)

 

Now, as you know C*V also equals N, so you can use this to your advantage...

 

N = C * V

N= 10 uM * 8

N= 80 uM  - this is the amount you want finally. From this you can also work

 

V= N/C

V= 80/ conc in uM of your solution.

Thanks for the explanation Bob. The Mol weight of the chemical is 234 g/mol

When you say N = mass/molar mass, do you mean 234/50?


Cheers,

Mad Researcher

#4 bob1

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Posted 05 May 2018 - 06:41 PM

Other way around: 50/234 (or rather 0.05g/234 g/mol)...



#5 Mad Researcher

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Posted 06 May 2018 - 07:18 AM

Other way around: 50/234 (or rather 0.05g/234 g/mol)...

So, I calculated like this - 

0.05 g/ 234 g/mol = 0.0002 mol (is the unit correct).

N = C x V = 80 µM

V = N/C = 80/0.0002 = 400,000 (What would be the unit here?)

 

Is the overall calculation correct now?


Cheers,

Mad Researcher

#6 bob1

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Posted 06 May 2018 - 06:43 PM

One more unit conversion - you have the top correctly in mol, but remember this is for a 50 mg/ml solution so that 0.0002 is actually 0.0002 mol/ml,  The bottom is in micromol. Convert one or the other to get them to the same prefix - note that the 0.0002 is 0.2 mmol/ml and 80 umol is 0.08 mmol - if that helps keep it in some numbers that make sense. The final unit will be ml!

 

so V=N/C...



#7 Mad Researcher

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Posted 06 May 2018 - 07:00 PM

One more unit conversion - you have the top correctly in mol, but remember this is for a 50 mg/ml solution so that 0.0002 is actually 0.0002 mol/ml,  The bottom is in micromol. Convert one or the other to get them to the same prefix - note that the 0.0002 is 0.2 mmol/ml and 80 umol is 0.08 mmol - if that helps keep it in some numbers that make sense. The final unit will be ml!

 

so V=N/C...

 

Thanks, now it makes sense. The final answer is 0.4 ml or 400 µl.


Cheers,

Mad Researcher





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