Rebecca,

Neil Loader (Godwin Inst. For Quat. Res., Cambridge; presently at
Forschungszentrum, Julich) and I have a paper in press outlining a new
technique for oxygen isotope analysis of nitrates (Rapid Catalytic Oxidation
of CO to CO2  - On the development of a new approach to on-line oxygen
isotope analysis of organic matter, Rapid Communications in Mass
Spectrometry).

Basically our technique utilizes existing elemental analyser technology to
produce a sample of carbon dioxide gas (rather than CO) for oxygen isotopic
analysis. The on-line method relies upon the high temperature pyrolysis of
the sample over a carbon source followed by a rapid, non-contributive
catalytic oxidation over nickel powder at a temperature between 500 and 600
C. Between this temperature range the CO disproportionates to CO2 and
isotopic equilibrium prevails (the CO is simply pumped away).

Details: At present approximately 1.5 mg of silver-nitrate is used; run time
is 15 minutes per sample and precision is better than +/- 0.2 o/oo.

Note: we also use this technique for organic materials (cellulose) and we
hope to use it for sulphates in the future

Bill Buhay

----- Original Message -----
From: Rebecca Hood <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, August 04, 1999 5:08 AM
Subject: 16O-18O ratios of nitrate


> 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
>