Phil,

We have gotten W-85 from Union Carbide since 1985.  It was an experimental
zeolite that was made in the early '80s for potential use in sewage
treatment plants, the way I understand it.  However, the zeolite was
unstable and the manufacturing was discontinued pretty soon after the first
batch was made.  A few years ago we got some more W-85 from Union Carbide,
and they told us that that aliquot was the last batch they had, so the
supply possibly is depleted.

We have sucessfully freeze dried samples with only NO3 (groundwater) and
run the residue on an EA-CFIRMS with the O2 turned off and a little sucrose
added.  We have also adjusted the pH on NH4 samples, freeze dried them and
then run the residue in through the EA.  The problem comes in when you have
organic N and NH4 and NO3 in the same sample.  We have been using a
modified version of the pretreatment technique of the Sigman et al 1997
(Marine Chem 57 pg 227) to get rid of the organic N and then rapid-stilling
(ala Velinsky) the NH4 over to an acid trap, converting the NO3 to NH4 with
devardas alloy and then rapid-stilling that over into an acid trap.  At
this point you can either adsorb the NH4 on W-85 (if you have any stable
form left) or adjust the pH to below 3, freeze dry and run the residue.  We
have found that our W-85 is a bit unstable at this point, some batches
adsorb better than others so it is important to come up with an alternative
technique.  When the new pyrolosis EA systems come out you should be able
to run NO3 for N and O isotopes much better than we can now in combustion
systems.  NH4 seems to run pretty well now, but we had to fiddle around
with the protocol to run NO3.  I don't know about running organic N, if you
can distill out the NH4 and the NO3 and run the residue, we have found that
the pretreatment is necessary in freshwater samples because the organic N
component is so high and some seems to break down and come over with the
NH4.  Carol Kendall has a technique, I think, that adsorbs NO3 on an ion
exchange resin, that may be useful in the separation of organic N from NO3?
 Does anyone know of a protocol to sucessfully run N-15 on organic N?

Bill

At 09:34 PM 9/17/98 +1000, you wrote:
>Dear Colleagues,
>        I am trying to track down a source of  Zeolite W-85 formerly
manufactured
>by Union Carbide. It is used as a method for scavenging ammonia from
>aqueous solutions for determination of nitrogen isotopic ratio at natural
>abundance  See:Velinsky, D. J., et al Mar. Chem. 26, 351-361 ( 1989).I
>should be grateful for advice of suppliers, or of alternative techniques of
>comparable effectiveness and efficiency.
> thanks for your help.
> Phillip Ford
>
>Dr Phillip W. FORD
>CSIRO Division of Land and Water
>GPO Box 1666,
> Canberra, ACT 2601,
> Australia
>tel +61 ( 02 ) 6246 5559
>fax. + 61 ( 02 ) 6246 5560.
>
>*****************************************
>
William J. Showers
NCSU Stable Isotope Lab
North Carolina State University
Raleigh, NC 27695-8208

(919) 515-7143 Voice
(919) 515-7802 Fax

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