Peter, I just use 99.999% purity N2 as a reference gas.  This seems to have
an isotope ratio close to 0.00, my current tank is 0.8 per mil.

I haven't tried to measure low concentration N2 but be carful
transfering  from one container to another with syringes in air.  This can
result in very bad contamination from air without special equipment.

Hope this helps, Paul Brooks.


At 03:00 PM 5/31/00 +0200, you wrote:
>Hello,
>
>We will start to measure 15N in nitrogen-gas, using europa uk's
>ANCA-TGII. Can you give me some tips, especially on where to get
>N2-reference gas for the analysis? Also, if there are  people
>measuring N2 using the same equipment, can you give me some
>practical advice (concerning the event files, etc...). We would like
>to measure N2 far below atmospheric concentrations (some % if
>it's possible). Thank you very much for your time.
>
>Peter.
>-----------------------------------------
>Peter Vervloedt
>Ghent University
>Laboratory of Applied Physical Chemistry
>Coupure Links, 653
>9000 Gent
>tel.: +32 9 264 60 00
>fax.: +32 9 264 62 30
>e-mail: [log in to unmask]
>----------------------------------------