Hi Dmitry,


Do you have the exterior ramped GC column on your EA IsoLink? If so, it'll be difficult to fit a longer GC column inside the shallow compartment. If your column is located in the internal compartment, there's more space for a longer GC column, which might help separate the N2 and CO peaks more effectively.


Hopefully someone will offer a simple solution, but on the extreme end you could also consider additional capillary GC separation like Paul Brooks' suggests in the 2010 Isogeochem post linked here: https://list.uvm.edu/cgi-bin/wa?A2=ind1007&L=ISOGEOCHEM&P=58792 (July 2010, post ID = 58792). I've thought about implementing something similar on our TC/EA for organic samples, but haven't worked up the nerve yet.


Cheers,

Jordon

----------------------------

Jordon Munizzi, PhD

Research Facility Manager


Department of Earth and Environmental Sciences

University of Kentucky

Ph: (859) 270-9177

Fax: (859) 323-1938

[log in to unmask]

isotopes.as.uky.edu


From: Stable Isotope Geochemistry <[log in to unmask]> on behalf of Dmitry Kopylov <[log in to unmask]>
Sent: Tuesday, July 2, 2019 9:55:48 AM
To: [log in to unmask]
Subject: [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

image.png