Hello Dmitry,

There is an extensive discussion of this separation issue in several older papers and especially in Farquahar et al 1997.

One way we have found to get around this problem is to work with an Elemental Analyser separating gases with a "purge and trap" system rather than a GC column. You can find a discussion comparing both techniques in Fourel et al RCM 2011.

If you want to discuss it in greater detail or send some test samples please do not hesitate to contact me off the list.

Good luck.

Best regards,

Dr François FOUREL

 Université Claude Bernard Lyon 1
 3 rue Raphaël Dubois - Bât. Forel
 Tél : +33 (0) 4 72 43 16 81
 Email : [log in to unmask]
De : Stable Isotope Geochemistry <[log in to unmask]> de la part de Dmitry Kopylov <[log in to unmask]>
Envoyé : mardi 2 juillet 2019 15:55
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Objet : [ISOGEOCHEM] N2 / CO separation

Dear all,

I'm trying to arrange the measurement of d18O in N-containing organics (in hair).
The problem is this substance gives a large N2 peak which is registered on the same collectors with CO. The N2 peak stays so close to CO peak that it leaves no time for correct background detection and leads to big errors in d18O measurement.
I have tried to decrease the reactor and column temperatures, to increase the start slope / end slope settings, to burn the column at 190 C for several hours. It helps a little, but doesn't solve the problem completely.
Does anybody know the ways to improve the separation of these two peaks?
Maybe there is a possibility to use another type of column? In the Thermo catalogue there is only one type of column for d18O analysis, but possibly there are other options?
I'm attaching the example of spectrum acquired with method: 1450 / 60 (Furnace / Oven temp.), 100 / 100 (Carrier and Reference flows).
My equipment is DeltaV Advantage + ConFlo IV + EA Isolink Flash IRMS.

Will be wery grateful for your advices!

Best wishes,
Dmitry Kopylov