EGTA Stock Solution

Hi out there!
I have two (hope so) simple questions:
First: Is it possible to make Stock-Solutions of EGTA? - I am not sure
if EGTA, once brought into solution, won't loose its capability to
chelate metals, eg. ca2+. Would be nice if it works...
Second: If it is possible, is there a special receipe or so how to
solve EGTA best?

Thanks for your help, all the best...
Thomas

In article <[Only registered users see links. ]> , [Only registered users see links. ] (tomte) wrote:

No, it is very stable and stocks can be stored for years.


Same as EDTA. A most typical stock is 0.5M final and is
obtained by slowly adding dry NaOH to a free acid until
it starts dissolving. The final pH is typically adjusted
to 7.5-8.0.

DK

On Thu, 11 Sep 2003, Richard P. Grant wrote:


It works. I worked in a lab that did this and used the stock to stop
platelets aggregating.


Yes. I think some people used to heat it, too, if they were impatient.

While we're on the subject, this 'pH it to get it into solution' business
has always irritated me. We know the pKas of EGTA, right (or at least we
can look them up somewhere, although this data is often a pain to find)?
And we know how acids and bases work, right? So why can't we *calculate*
how much NaOH we need to add to get the right pH, then just mix the EGTA,
NaOH and water together, and let it all dissolve on its own (well, in the
company of a stirrer, anyway)?

I did this at one point with EDTA; 93.05g of Na2.EDTA (FW 372.2), 10.14g
of NaOH (FW 40), 500 ml dH2O, let it all dissolve, and it's bang on pH
8.0, at 500 mM EDTA.

If you don't trust this method, you can always go a bit short on the NaOH
and then pH it to your satisfaction otherwise; even if it's not perfect,
it'll save a lot of time.

tom

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On Fri, 12 Sep 2003, Richard P. Grant wrote:


I'll drink to that. Also, the maths is bleeding fiddly.


Hmm. One might argue that we're adding the NaOH to get it to the right pH,
and that bringing the EDTA into solution is a side-effect. However, that
way madness lies, so i won't.

tom

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