Wolfram,

Thanks for the reply. I was going to use liquid nitrogen for the CO2 trapping.  Is that too cold?  Is calculating the trapping capacity of the liquid nitrogen trap as easy as calculating the volume of tube and using PV=nRT and perhaps cutting it by 50% since I don't want to block the flow?  And you're comfortable that trapping of CO2 is thorough enough not to affect the CH4 analysis?

Thanks,

David

David DenHaan
Laboratory Technician
National Laboratory for Agriculture and the Environment
Ames, IA

-----Original Message-----
From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On Behalf Of Wolfram Meier-Augenstein (aps)
Sent: Thursday, May 26, 2016 9:39 AM
To: [log in to unmask]
Subject: Re: [ISOGEOCHEM] Using Precon for CH4 and CO2 separation

Hi David,

What you propose doing should work.  You could use a methanol/liquid N2 mix (-98C) to be sure to trap CO2 without it breaking through if you feel dry ice/acetone (-78C) might be cutting it too finely.

Best,

Wolfram
________________________________
From: Stable Isotope Geochemistry <[log in to unmask]> on behalf of Denhaan, David <[log in to unmask]>
Sent: 26 May 2016 15:20
To: [log in to unmask]
Subject: [ISOGEOCHEM] Using Precon for CH4 and CO2 separation

Dear List,

I'm trying to analyze CH4 and CO2 from the headspace of a bacterial culture with a labeled acetate substrate.  Depending on the enrichment in CO2 and methane evolved I should be able to show which bacteria are active.  I have a Precon hooked up to the gasbench GC and a Delta V.  I 'm hoping to trap the CO2 from the headspace on the manual trap this would let the CH4 pass through to be combusted and measured.  When that's done I would raise the manual trap and measure the CO2.  Is this a sound approach?  I'm worried about how much CO2 can be trapped on the manual trap and how complete the trapping is.  If CO2 comes through the manual trap I won't be able to distinguish it from the CH4.

Thanks,

David

David DenHaan
Laboratory Technician
National Laboratory for Agriculture and the Environment Ames, IA





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