Has the customer tried Chelex-100 resin? Chelex has a particularly high
affinity for the Fe+++ and Cu++ ions and also binds other di- and
tri-valent cations very strongly.
I would recommend a "batch" method, where the the sample solution is
stirred with the Chelex for many hours (overnight), followed by filtration
or centrifugation to remove the resin. I used to use this method for
removing metal cations from bacterial lipopolysaccarides prior to analysis
by 31P or 13C NMR (see J. Biol. Chem. 258: 13466-13477, 1983). Of course,
chelators must be used at the appropriate not-too-acid pH to be effective.
Soil extracts could conceivably contain microbial iron chelators,
"siderophores" that bind Iron(III) with exceptional affinity. Chelex
may not be effective if such complexes are present. Bentley et al
(1986, Biochem. 25:1455-1457) report a method for de-ferration of a
siderophore from Microsporum gypseum.
Good luck.
--Mike
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Michael Strain strain@mango.uoregon.edu
Institute of Molecular Biology desk/voice-mail: 541-346-4605
and Department of Chemistry lab: 541-346-4036
University of Oregon FAX: 541-346-5891
Eugene, OR 97403
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On Mon, 11 Aug 1997, doug meinhart wrote:
> Dear Readers,
>
> I was asked by a customer who is applying for membership
> to post the following request to ammrl for advice:
>
> Does anyone have information or literature references about soil extraction
> for 31P NMR analysis?
> The two problems seem to be 1) a protocol for the extraction procedure
> and spectroscopy and 2) broadening from paramagnetic (Fe and others)
> impurities.
> As far as paramagnetic impurities, the customer has tried
> ion exchange columns with limited success.
> Does anyone know of other methods to remove or sequester the paramagnetic
> ions,
> preferably in a diamagnetic spin state, so to be able to record the 31P
> NMR?
> I have heard of a compound called "Tiron," used to sequester Fe, but
> have no references about its use.
>
> Any comments?
> I will forward answers to the customer and make a general posting if
> applicable.
>
> Doug Meinhart, Ph.D.
> NMR Product Manager
> JEOL USA 11 Dearborn Road, Peabody, MA 01960
> tel 508-536-2303 fax 508-536-2288
> email: meinhart@jeol.com
>