Here are my two cents on an item by item explanation:
> organic: S, N, C
These three can be done using the EA-ConFlo. Inorganic S is not difficult
and beware of "old wives tale" regarding S contamination. See my
explanation on ISOGEOCHEM of a few years back regarding SO2. It works fine.
Organic S may be another story depending on type and S concentration in the
> aqueous: S (SO4), C (DIC), N (NO3, NH4)
DIC can be done with the GasBench. SO4 from Ba precipitate gives BaSO4 and
can be done on the EA-ConFlo (<0.5mg BaSO4). Do not use more than 0.5mg due
to the difficulty in combusting BASO4 (From Ann-Lise Normand, Calgary, PhD
thesis presented at the 1rst Canadian CF-IRMS Workshop).
> water: O and H
The GasBench can indeed do these.
> mineral: C (carbonates)
GasBench can do carbonates. It can work well with pure calcite or dolomite
However it does have some potential drawbacks. For mixed minerals it may be
difficult to do the temperature-timed reaction-separation as explained in
the Al-Aasm I., Taylor B. paper, 1988(?). Hi Mg and Fe minerals such as
siderite and magnesite may be difficult to prepare and analyse due to the
long reaction times needed (e.g. siderite needs 3 days at 50oC and magnesite
needs 3 weeks at 50 oC and this is for isotopically correct gas values not
100% reaction). Off-line may still be the best option for some of these.
> gas: C (atm CO2)
Depending on the precision needed, dual-inlet is still the most accurate
(better then 0.02permil). This kind of precision is needed in atmospheric
monitoring. For many projects however, you can use a slightly modified
PreCon device (Ehrlringer lab in Utah and our own work here on CO2 in
ice-cores). You can also prepare (concentrate) samples off-line and inject
through a septum modification on the EA-ConFlo (Ehrlringer lab; as well as
Wassenaar L, Koehler G, On-line technique for determination of del 18O and
del 17O of gaseous and dissolved O2, Analytical Chem, 1999)
> The EA will handle the organic samples (though I understand S
> can be a bit tricky).
Organic S can be tricky.
> For H in water with the gas bench system, Finnigan is recommending H2/H2O
> equilibration using a coated platinum catalyst.
> We will have a multi-purpose, off-line sample processing line, though its
> use will be much more limited if we go with the gas bench.
1) Easyer to monitor instrument performance.
2) Well known and proven technology
3) For continuous-flow H2 or O as CO; you can reference inject from the
dual-inlet. No need for CO monitors and special ventilation since only the
pumps need venting. Very little gas is used at a time allowing to store the
main cylinders elswere. This means you don't have to flush your ConFlo
regulators each time you change to CO or H2 and back to N2-CO2 in order to
4) All off-line preps can be analysed on a dual-inlet
5) Calibration of some internal standards for the continuous flow systems
can be done on this.
Hope this is of some help
UniversitÚ d'Ottawa / University of Ottawa
Sciences de la Terre / Earth Sciences
Laboratoires d'isotopes- G.G. Hatch -Isotope Laboratories
140 Louis Pasteur
Ottawa, Ontario, Canada, K1N 6N5
Tel: (613) 562-5800 xt 6839 (Bureau / Office)
xt 6836 (Lab)
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