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Salt and EDTA - confused (Mar/24/2010 )

Hello everyone,

I hope everyone is doing well. Spring has finally arrived here and it feels gooood :P

I have a rather stupid question but I really need enlightment on this, so I put my pride under a rock, and I jump.
I extract hard tissues with EDTA, a bit of detergent and proK.
People always mention high concentrations of salt in my extraction buffer, but EDTA being an acid...I need a biochemist to explain me where the salt is (told you it was stupid).
The reason I'm asking is because I use some guanidine hypochloride based buffer, mixed with my extract (heavily concentrated in EDTA) to bind on silica and the reaction is pH and salt dependant. Does 0.5M EDTA modify the salt content?
I hope I am clear. This isn't in my head :o .

Thank you.



Maybe because you dont use pure EDTA but one of the salts like EDTA, tetrasodium salt ?

Good question though.


I don't think so. Here is what I am using from Fisher (cat # BP2482-500)

Ethylenediaminetetraacetic Acid (0.5M Solution/pH 8.0), Fisher BioReagents
Ethylenediamine Tetraacetic Acid
0.5 M Solution, pH 8.0 (for DNA Work)
Clear, Colorless Liquid
Application:EDTA is used extensively in molecular biology to minimize metal ion impurities in reaction buffers. Ideal for DNA work.
F.W. 292.25

I guess the manufacturer uses NaOH to get the pH right, but this is no salt either.


no, but it does increase the ionic strength of the medium (and also contributes sodium ions).


It's called acid because it has functional acid groups (-COOH)....but at pH 8 the H+ is replaced by a Na+ (though it is dissociated in the solution)....


Sooo the more EDTA you use, the more salt you have.


This site is awesome !!!


Don't forget that the guanidine HCl is also a type of salt.


So adding lots of EDTA to the Qiagen PB buffer would decrease the efficiency of the DNA binding to silica, right?
What could be done to restore the balance?