By syx_gf on Monday, August 9, 2004 - 05:27 pm:

We have syrup that contains EDTA in the formulation. It has a long tail that captures and catches our peak of interest. We need the advice from knights of chromatography to tame the EDTA "dragon" and let the "princess" peak go.
Thanks for every help.

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By Anonymous on Tuesday, August 10, 2004 - 06:53 am:

Add cation to complex with the EDTA

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By syx_gf on Tuesday, August 10, 2004 - 05:15 pm:

What kind of cation? Can we use FeCl3?

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By Anonymous on Wednesday, August 11, 2004 - 08:01 am:

I'd first try copper acetate.

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By syx_gf on Wednesday, August 11, 2004 - 05:59 pm:

I think I have resolved the problem. I change my column with the more pure silica than the earlier (lowest metal contents). Result: the threatening tail is gone and releases our peak free.
Anonimous, thank you for your help. Maybe it will useful next day. Based on Lewis acid-base, what if we use soluble calcium salt to bind EDTA?

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By Chris Pohl on Saturday, August 21, 2004 - 05:50 pm:

syx_gf

The EDTA stability constant for calcium is 11 whereas the EDTA stability constant for copper is 18.7. That's more than nearly 100 million times that of the calcium complex so you can see that calcium won't compete very effectively when the cause of tailing as a transition metal. By the way, it's probably not a great idea to use iron since the pH of your separation needs to be quite low in order to keep it in solution and you'll need to add an excess of metal ion in order to completely complex to EDTA.