Calculations with x-times concentrated Buffers - (May/18/2011 )

Hi,

I have very embarrassing calculation problem.

Imagine I have a PCR reaction sample with a volume of 20 µl. After the
PCR reaction I want to put it onto a gel, so I need blue marker loading dye.
My blue marker loading dye is 6x concentrated so I would obviously take 4 µl
(4 µl of a 6x buffer in 24 µl volume then). Everything is fine then.

But now I am wondering how I can calculate the volume which would be required if
I used 7x buffer and got stuck in a caclulation...

1 x (20+X) = X x 7 (X = the volume of the buffer which is required)

It is obvious that it should be something between 3 and 4, but how can I calculate
it exactly?

simply divide the amount to which you want to add the 7x buffer by 6 and add that amount of 7x buffer.

just do the same as in the first calculation.

24/7 = 3.43

Podge on Tue Jun 7 15:47:21 2011 said:

that would work if the final volume you wanted was 24ul. all we know is that the sample volume is 20ul and you want to add a 7x buffer. the sample is 6/7 of final volume.