dilution question - (Mar/23/2005 )

I need to prepare 700mL of 1X TAE using 50X TAE buffer stock (contains 2M Tris base, 5.71% v/v glacial acetic acid and 50mM EDTA).

I did 1/50*(700) = 1400mL 50X TAE.

I need to dilute this 1400mL 50X TAE to 700mL 1X TAE. So 1400/700 = 2

So I plan to add 2mL 50X TAE + 698mL H2O. This will give me the 700mL. My question is: is this the way to do it, and will this give me the needed 700mL 1X TAE?

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Hi

You should use this formula C1.V1 = C2.V2 (C for concentration and V for Volume). In your case you have 50.x = 1 (final concentration) .700 (volume you want) so x, being the volume of TAE 50X you need to make the 700ml TAE 1X, is 700/50 = 14ml.

In your case you don't care of knowing that you have a stock of 1400 ml; all you care of is its concentration.

Hope this helps!

sabrina

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Hi,
Ok, that was what I was trying to do, but I guess I just multiplied it wrong. I was doing (1/50)*700, so that is 14mL. This 14mL is the concentration of the 50X TAE right? So, I use 14mL of this 50X TAE and add in 686mL H2O to get 700mL of 1X TAE buffer?

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you made a mistake in your formula : 700/50 = 14ml!!!

so you're right in both cases...

in general cases :
for preparing a volume V of solution using a stock at Nx (N = 10 20 5 or whatever but a number), you can simply do :
volume V2 of stock to pick : V2 = V/N

hence for your solution :
v=700ml
N = 50
v2 = 700/50 = 14ml
obviously qsp 700ml with water !

this formula is better in case of preparing solution with many stocks solutions. You calculate for each stock solution te volume to pick (V2, V3....) and finally qsp V (v=volume of new solution)
cheers
fred

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