Stable Isotope Geochemistry


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Dr W Meier-Augenstein <[log in to unmask]>
Reply To:
Wed, 18 Feb 2004 14:56:56 -0000
text/plain (77 lines)
Dear Harro and others interested in this subject,

This is me shooting from the hip again.

Health and safety regulations in Europe require special precautions
being taken when working with CO, irrespective of context or amount. In
other words, if you plan to keep/store/use a CO cylinder in your lab (or
to generate CO in situ), proper ventilation has to be provided. This
usually means active exhaust / vent lines.

Reasons: (1) CO is classified as highly toxic (T) and (2) extremely
flammable (F+) since it forms flammable mixtures with air at 7.4 < vol%
in air < 12.5. It therefore comes with a raft of R and S risk and safety
numbers attached (to wit R12, R23, S9, S16, S33A, S36A and S45).

With regards to the suggestion of using CO2 instead of CO as reference
gas for 18O work by monitoring the CO+ generated in the ion source, I'm
afraid this won't work. Been there, done that, didn't get the T-shirt
though (in 1996 to be precise). With the usual benefit of 20/20
hind-sight vision, the explanation is rather obvious: isotopic
fractionation during formation (= mass fragmentation) since the reaction
and the product formed are a function of (a) [partial] pressure and (b)
isotopic make-up of the CO2 used - plus one's choice of source



> -----Original Message-----
> From: Stable Isotope Geochemistry
> [mailto:[log in to unmask]] On Behalf Of H.A.J. Meijer
> Sent: 18 February 2004 14:22
> To: [log in to unmask]
> Subject: Re: CO gas for CF-IRMS
> Dear Colleagues,
> The question by Jean-Pierre Girard and the following
> discussion is most interesting to me, as we are in the
> process of buying a GVI Isoprome. Originally it was intended
> to be just for 2H of water, but presently we are discussing
> the extension to 18O as well. And that brings us into the CO
> buisiness. I did not realise these security problems before,
> and the discussion brings me to some questions:
> (1) Why would the CF use of the Isoprime (or the Finnigan
> equivalent) use more CO than the dual inlet? After all it is
> just the short reference pulse each time that uses the gas?
> (2) How can you run a dual inlet system in combination with
> elemental analyser  combustion/pyrolysis? Or do you just use
> the dual inlet arrangement as a smart kind of reference gas injector?
> (3) Did anyone try CO2 (with about 8% of CO+ formed in the
> source) or even enriched N2 (with 15N15N added) as a
> substitute for CO?
> regards,
> Harro Meijer
> --
> Prof. dr. Harro A.J. Meijer
> Centrum voor IsotopenOnderzoek (CIO), Rijksuniversiteit
> Groningen Nijenborgh 4, 9747 AG  Groningen, Netherlands
> tel +31-50-3634760   fax +31-50-3634738