The reference given to you by Myq Larson is a good place to start.  (Stark
and Hart, (1996)) Soil Sci Soc Am J 60:1846-1855.

 This method has the limitation of requiring relatively large amounts of
soil extracts.  Various incarnations of this method are used widely.  For
smaller soil quantities, Risgaard-Petersen, Rvsgaard, and Revsbech have
published two methods which require much less N.

"A combined microdiffusion-hypobromite oxidation method for determination of
15N isotope in NH4+" (Published in Soil Sci soc Am J recently)

and

"A sensitive assay for determination of 14N/15N isotope distribution in NO3-
J microbiological methods "  (1993)  17:155-164

These methods are sensitive to very small quantities of N but require that
your machine be tuned for 30N2 / 29N2 ratio.


Good luck
> -----Original Message-----
> From: Armand Krueger [SMTP:[log in to unmask]]
> Sent: Monday, January 26, 1998 9:36 PM
> To:   [log in to unmask]
> Subject:      Nitrate & Ammonia on soils
>
>     Dear all,
>
> I'm looking for a good procerure to sererate ammonia and nitrate in
> agricultural soils that have low concentrations of nitrogen in them. I'm
> using a Carlo Erba nitrogen analyzer coupled to a Uropa Tracermass 20/20,
> I
> would like to take a small volume of solution put it on chromosorb and
> combust the sample for nitrogen isotope ratios if possible.
>
>
>                        Thanks  Armand
>
> Armand Krueger
> University of Wisconsin
> Horticulture Research Lab
> W 6797 Kampen Road
> Arlington, WI 53911
>
> Phone: (608)635-2026
> Fax: (608)635-7428
> email: [log in to unmask]