Marylyn, Linda, Dachun & others

Keisuke Koba emailed me about a method published by Charles T. Garten, Jr.
in 1992, hasa anyone tried this method?

Bill

Hi Bill:
I have used ion-exchange resin (H+ type for cation exchange)
to collect NH4 from diluted H2SO4.
You can find this procedure in
Garten Jr. 1992 Nitrogen isotope composition of ammonium and nitrate
in bulk precipitation and forest throughfall
International Journal of Environmental Analytical Chemistry 47 33-45
I am not sure why we can get good precision with IER.
But as far as I experienced, IER works great.
The problem is IER contains a lot of S and if you use conflo
you can suffer from long tailing of SO4.
So, I don't use IER with conflo.
I hope it helps
Kei
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Keisuke Koba
The Ecosystems Center
Marine Biological Laboratory
Woods Hole MA 02543
508-289-7697 (tel) 457-1548 (fax)
495-0087 (home)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Graduate School of Informatics
Kyoto University Japan




At 11:11 AM 05/31/2000 -0400, you wrote:
>>Aside from the dificulty in locating it, we are having great difficulty
>>using it to get NH4 out of test solutions, trying to replicate work by
>>Velinksy, Fogel & others. The way you dry the zeolite after getting out
>>out of the NH4 solution (dessicator, freeze drying, oven drying) seems to
>>affect the d15N by 1-2 permil. If anyone has any great tips, please let me
>>know. This work has also produced some data on isotopic effects of drying
>>NH4 solutions (freeze-drying, oven drying) which I will send in an other
>>email, when I can tabulate it all up.
>>
>In regards to this point of drying, freeze-drying or other vacuum drying is
>not a good idea for the initial drying. The best thing that worked for us
>was a low tmeperature oven (50C) with either dry N2, He, or Ar flowing
>slowly through the oven. I doin't think a dessicator would necessarily have
>the capacity to dry the zeolite as thoroughly.
>
>Another point, in switching from conventional, old-timey sealed tube
>combustion to spiffy EA work, we encountered another problem that
>previously was not an issue. We typically use N2 gas flowing through the
>oven. When we loaded the zeolite-ammonium powder into the Al boats, we
>analyzed them as per usual. It turns out that there was, as expected, quite
>a bit of N2 gas trapped in the zeolite--Duh. In sealed tube method, that N2
>was simply pumped away.
>
>For this to work with the EA, He or Ar, would have to be used rather than
>N2. Even oxygen would work I think.
>
>Final detail, the amount of time for the drying should not be shortened,
>but it can be lengthened.
>
>Marilyn
>
>Dr. Marilyn L. Fogel, Senior Scientist
>Carnegie Institution of Washington
>Geophysical Laboratory
>5251 Broad Branch Rd., NW
>Washington, DC 20015
>USA
>202-686-2410 ext 2480
>FAX 202-686-2419
>