Stable Isotope Geochemistry


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Dr W Meier-Augenstein <[log in to unmask]>
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Sat, 30 Jul 2005 16:18:13 +0000
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Hi Adam,

Do both peaks broaden (H2 and CO) or only the H2 peak?

If its only the H2 sample peak, I'd be tempted to say something's messing 
up the He flow in the reactor (usually spilled silver starting to build up 
at the bottom of the reactor tube); but for that to happen after only ten 
runs is pushing it a bit.

I take it all the usual suspects have been ruled out, such as air breaking 
in due to problems with the AS isolation valve or a GC column that hasn't 
been baked out for a while?

If both sample peaks broaden and eventually vanish, my money would be on 
the column. Perhaps the fact it happened when you run your benzoate samples 
was merely a coincidence.



On Jul 29 2005, Adam Zoltan Csank wrote:

> Hello all,
> I've been attempting to run some Benzoic acid on the TCEA, however, it 
> seems that after a little over ten samples have been run my peaks begin 
> to tail until they they disappear. The cause of this problem is that 
> the graphite crucible seems to be softening and degrading and so is not 
> allowing the samples to reach the hot spot. I am wondering if maybe the 
> benzoic acid is reacting with the graphite somehow. Or if , since we 
> have been cleaning and reusing our crucibles, the crucibles themselves 
> weaken over time.
> I would be curious to know if anyone else has had this problem, and if 
> anyone has any ideas as to what could be the cause.
> Thanks in advance,
> Adam
> Adam Zoltan Csank
> Department of Geological Sciences,
> University of Saskatchewan,
> 114 Science Place,
> Saskatoon, SK, Canada,
> S7N 5E2
> phone (o) (306) 966-5737
>               (h) (306) 665-2797
> email <[log in to unmask]>