Hi Gavin,

My apologies, in my response to Fred's enquiry I should have pointed him towards the papers by members of Tom Brenna's group also (Goodman, Sacks, Tobias), and of course the work by Dawn Merritt.

Don't you just hate pre-senile dementia creeping up on you?

Best wishes,


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-----Original Message-----
From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On Behalf Of Gavin Sacks
Sent: 04 May 2011 20:47
To: [log in to unmask]
Subject: Re: [ISOGEOCHEM] GC-IRMS, peak shape and how it affect stable isotope ratios for carbon and hydrogen

Hi Fred, in addition to Wolfram's papers, there's a couple of other papers that have looked at peak size, combustion conditions, and background.  The effects of peak shape (tailing/fronting), to my knowledge, has not been systematically studied for a given amount of material on column (say, by changing phase ratio).  My experience has been that overloading doesn't compromise d13C linearity so long as baseline resolution is still achieved . . . which is a big "if".  Most of the work is on d13C, not D/H.

Goodman and Brenna, J Chrom A 1995 (discussion of peak size) Merritt and Hayes, 1994 An. Chem Merritt and Hayes, 1995 An Chem (discusses effects of incomplete oxidation, among other things) Wolfram's 1996 J Chrom A paper and his other refs.
Sacks, Zhang, and Brenna, 2007, An Chem (buried in the discussion is a section on the role of peak width and background noise in compromising

As I've said in other posts, reproducibly defining the background is usually the main issue with getting good precision.

- Gavin

> Dear IsoGeochem
> I have very difficult to find literature that concerns the subject of 
> the quality of the chromatography and how it affects the stable 
> isotope ratios in GC-IRMS.
> I'm thinking especially about peak shape (tailing/fronting, overload, 
> poor oxidation/reduction of oven, leakages, bad column etc), and not 
> so much about poor separation.
> Has anyone on this list done studies into this subject, that could 
> tell me a little about it, or maybe show some data on it? How does 
> peak shape, background and signal strength correlate and affect the 
> isotope ratios?
> Thank you very much!
> Best regards,
> Fred Martin Kaaby

Gavin Sacks
Assistant Professor of Enology

Dept. of Food Science & Technology
NYS Ag. Experiment Station
Cornell University
Geneva, NY 14456

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