Hi Ulrike,

Have you considered using a cavity rind down spectroscopy (CRDS) type of instrument for your water analysis?

I've spent the last 2 years analyzing water samples using a TC/EA-IRMS system but had the extreme luck of getting introduced to CRDS, meanwhile. The system uses no consumables other than the vials and septa as opposed to the TC/EA glassy carbon tube that costs $1000 and packing the tube with granules every 400 injections, not to mention the frequent use of bracketing standards, besides the filament change and the ion source clean up. I believe Willi Brand himself (the senior author on Gehre et al. article) is in the process of testing one, now.

In case you're interested, you can check www.picarro.com/isoanalyzers/isotopicliquid.php for more info.

As for standards, we split them up in 2ml quantities, use polyseal caps with borosilicate vials, wrap Teflon tape on the threads,  flush the top of the vial with Argon, seal them and freeze them to avoid any fractionation. We calibrate several working stds against SMOW/SLAP and we do monthly checks with SMOW/SLAP perse. let me know in case you have further questions.

Hope this helps.

Nabil

On Tue, Dec 9, 2008 at 2:20 AM, Ulrike Schulte <[log in to unmask]> wrote:

Dear listmembers,

from next year on we want to start on-line water analysis (delta18O, deltaD) with a TC/EA (equipped with a liquid autosampler) coupled to a MAT 253.
We know the publication of Gehre et al. (2004) about continous flow analysis of water sample but we would like to get in contact with people who already use this method successfully.
At the moment we are discussing intensively how to do the calibration of the system with SMOW, SLAP and GISP and how to store these reference materials after the ampule has been opened: Is it better to store it in a large bottle or vial (25 ml, glas or plastic?) and to reopen this bottle regularly for calibration checks or should we split the water in for example 1 ml portions and store it in very small vials?
How often do you check your system with these RMs?
How many secondary standards do you use, what?s the difference in their isotopic composition and how did you produce them?
Probably a lot of questions will rise during the next months and we will be glad about any information, literature or warnings....

Thanks in advance and have a nice day

Ulrike Schulte



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Dr. Ulrike Schulte
Institut für Geologie, Mineralogie und Geophysik
Lehrstuhl für Sediment- und Isotopengeologie
Ruhr-Universität Bochum
Universitätsstr. 150

D-44801 Bochum

Tel.: 0234/32-25454
Fax.: 0234/32-14571
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