dilution question - (Aug/29/2013 )

You are provided with an antibody solution (Ab) that has a concentration of 600 microgram/microlitre

For lab, it is necessary make the following dilution.

5ul of 1:60 Ab + 5ul of buffer to make a __________ dilution at ________ ug/ul.

Can someone help in solving this problem.  It seems that I am missing some basic concept.  I get the ug/ul, but I don't get the dilution.

Please explain in detail. 

You make a 1:60 dilution of the Ab. That means, if your starting concentration was 600 ug/ul, you will get a concentration of 1:60 * 600 = 10 ug/ul.

Now you take 5 ul of that, which is 5 * 10 ug = 50 ug. And in which volume do we have these 50 ug when we add 5 ul buffer to the whole thing ? 5ul+5ul = 10 ul, so you have 50 ug in 10 ul volume.

So your concentration is 5 ug/ul now.

Compared to the initial Ab concentration, its 5/600 = 1:120 dilution.

Tabaluga on Thu Aug 29 22:02:06 2013 said:

Compared to the initial Ab concentration, its 5/600 = 1:125 dilution.

watch your math, 5/600=120 (2x diluted from 1:60)

Ooops, you're right of course. Edited it in my post.