Dear Jason,
Can you clarify what you mean by a "few spikes"? There are compounds such as
COS, CS2, OS2 which can be generated under  combustion with low pO2. I would
have thought these to be unlikely and would also expect that the amount of
V2O5 would have some effect on their production. How does the amount of
injected O2 compare to the theoretical CO2 & SO2 production?
Roy Krouse
----- Original Message -----
From: "Jason Newton" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, October 13, 2004 7:49 AM


> Dear all,
>
> For the last couple of days I've been setting up routine sulphur
> isotope measurements for the first time on our mass spec (Delta plus
> XP + Costech EA), 0.8 m PTFE column at 80 degC, WO3/Cuy in reaction
> tube at 1020 degC.
>
> The first batch of standards (10 CP1 chalcopyrite and 2 of each of
> the usual IAEA and NIST stds) ran very well, although there is a
> linearity effect (mass spec related rather than EA-related) and the
> data also require a stretching factor to match them with accepted
> literature values.
>
> This morning I've been trying out a few tests of organic materials
> (feather, hair, plant etc.); however, the main SO2 peak is preceded
> by a few spikes. The spikes are a full minute before the main peak
> and so don't interfere with the results, but I'm puzzled as to what
> they represent. Are they an artifact due to the combustion of a
> (relatively) large amount of CO2 ? The spikes are present regardless
> of the presence/amount of V2O5 (0 to 0.5 mg) added to the samples
> (1.5  to 4 mg). Subsequent analyses are unaffected by this (i.e., no
> memory), and subsequent sulphide analyses run normally - so it would
> imply some relationship with C.
>
> Has anyone seen anything similar? Also, what internal lab standards
> are people using for organic d34S?
>
> cheers,
>
> Jason
>
>
> --
> ****************************************************
>
> Dr. Jason Newton
> East Kilbride Node Manager
> NERC Life Sciences Mass Spectrometry Facility
> Scottish Universities Environmental Research Centre
> Rankine Avenue
> Scottish Enterprise Technology Park
> East Kilbride
> G75 0QF
> UK
>
> e-mail: [log in to unmask]
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> ***NEW URL***
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