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Dear Clemente,

Apologies for asking the obvious questions first: where is your cold trap (at what point in the interface) and what are the dimensions of the trapping loop?

Assuming everything is ok with the set-up of your cold trap, are the AA samples you are analyzing very abundant in one (or more) particular amino acid(s); an amino acid you might not be interested in?

Example: collagen digest samples yield huge Gly peaks.  When I was carrying out CSIA of bone collagen digests we were mostly interested in Pro and Hyp so I heart-cut the Gly peak from the chromatogram so it would not enter the combustion interface. This way we could run more analyses before the cold trap became clogged.

Best wishes,

Wolfram



-----Original Message-----
From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On Behalf Of Clemente Recio
Sent: 02 March 2015 10:57
To: [log in to unmask]
Subject: [ISOGEOCHEM] N analysis by Isoprime GC-C-IRMS

Dear Colleagues,

We are trying to do N in aminoacids by
GC-combustion using an Isoprime MS coupled to an Agilent GC, and are having difficulties trapping the CO2 before the MS.

I would very much appreciate hearing from any of you with experience in similar work. It is obvious that we are doing something wrong, and I need help to identify our mistakes and sort those out.

Thanks,

Clemente


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Dr. Clemente Recio
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