Dear Nico,



While I have no experience with the particular application you are working on, I have developed a method to separate N2 from CO2 for determination of d15N and d13C values from selected amino acids within the same GC run.  While formation of CO was not problem, separation between N2 and CO2 had to be better than 20s between peak end N2 and peak start CO2 so we could switch IRMS settings from 28/29/30 to 44/45/46 between peaks with enough time for the IRMS baseline to stabilize.


The best results I achieved with a Carbo-PLOT P7 (at the time Carbo-BOND columns were not available yet). If you prefer to work with PLOT (BOND) columns of a lower ID for better separation resulting in sharper, symmetrical peaks, you could try a Pora-BOND Q with an ID of 0.25 as this should also give good separation of permanent gases and C1 –C6 hydrocarbons.  Column ID affects separation more (for the better) than column length.


Another option when dealing with permanent gases, especially separation of CO from NO, would be a Molsieve 5A PLOT column. This column is now also available with an ID of 0.25.


Pora-PLOT U and Pora-BOND U are less effective at separating permanent gases.  These columns were specifically designed for polar volatiles (eg alcohols, ketons) and volatile halocarbons.









From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On Behalf Of Küter Nico
Sent: 05 January 2017 10:36
Subject: [ISOGEOCHEM] Separation of CO and N2 in a GC


Dear Community,


We are curious about an efficient way for separating N2 from CO in a GC to analyze CO for d13C and concentration.


We are already able to separate the species somewhat sufficient with 1) an Agilent 30m GC Carbonplot (0.32mm widebore, 1.5um film) by pushing it far below its lower temperature-limit (-70°C) and 2) quite well with an Agilent 50m PoraplotQ  (0.32mm widebore, 10um film, also at -70°C).  We use a HP 6890 GC that is coupled to a Delta V IRMS.


The important point is that we also need to analyze coexisting CO2, CH4 and C2H6. So these should not get lost during the separation process.


Again, the Poraplot Q does a good job, but we are curious if anyone in this community has experience with other columns or with the N2-CO separation in a GC in general.


Thanks a lot and best wishes for the New Year!




Nico Kueter
Institute for Geochemistry and Petrology
ETH Zürich
NW E-75.1
Clausiusstrasse 25
8092 Zürich



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