Dear Rebecca,

I think I should mention our technique too.  Revesz and others
"Determination of delta O-18 and delta N-15 in nitrate" Anal. Chem.
1997,69, 4375-4380.  This is an off line preparation technique, using
KNO3 and catalyzed graphite.
The advantage of this technique is that no other inorganic compounds are
interfering with the result.  So, you do not have to go through lengthy
and potentially not error free ionexchange or other separation
techniques to get clear nitrate from the mixture. We have been using it
for years by now.
Regards: Kinga Revesz
Rebecca Hood wrote:
>
> Who out there is out there doing 16O-18O ratios on nitrate? if so what's the
> latest technique and easiest ?
>
> Someone asked me for this information, as we don't do it here yet  I would
> be interested to find out how and what are the pitfalls.
> Samples they are thinking of are soil-water samples, at natural abundance
> levels. It has some interesting potential....
>
> I would be most grateful for all suggestions, comments, references etc...
>
> Thanks in advance for any assistance........
> Long live isogeochem....
>
> Rebecca Hood