Dear Bryan,
You might be interested in knowing something else in addition to GasBench II
and GV's MulitFlow Geo.
Our lab is equipped with a Finnigan CarboFlo device to run large carbonate
samples (2-4 mg). As you probably know, this device has some memory-effect
issues, particularly when running small samples. In order to minimize this
effect, I modified this device a bit both for the hardware and therefore
software. Now this device runs very well. Here are some numbers you might want
to know:
---------------------------------------------
Auto carousel: 39 samples
Standard Dev.: d13C=0.03 permil, d18O=0.1 permil
Experiment time: ~30 hours
Acid volume: ~10 ml
Reaction temp: 120 degree C
----------------------------------------------
To check the memory effect on the modified CarboFlo, I had used four carbonate
standard samples (NBS-18, CHCC, ANU P3, ANU M2), which d13C values range from
+2.24 to -10.68 permil, I found the memory-effect is tremendously reduced to
almost none at this d13C range, as you can see from d13C standard deviation
above.

Cheers,

Zheng-Hua



>===== Original Message From Stable Isotope Geochemistry
<[log in to unmask]> =====
>Dear All,
>
>       We currently have VG-micromass-GV "optima" IRMS at our lab which
>we have been using for bulk carbon and nitrogen stable isotopes for the
>past 11 years. For the most part, the instrument has operated
>exceptionally well, with a few minor exceptions. One thing I don't like
>is the operating software; I'm not a big lover of OS2, as I wish we had
>something windows based, as it would certainly make data manipulation
>easier.
>
>Currently we are looking into acquiring a new instrument and I have
>researched both the DeltaPlus and GV's Isoprime. From those of you who
>have responded via the ISOGEOCHEM site, there seems to be two camps out
>there: those who prefer Finnigan instruments and those who prefer GV
>instruments. It would seem preference may be a function of what
>instruments people have worked on in the past and feel comfortable with,
>or what was previously available at a particular lab. Certainly there
>are features that are different between the two companies, for example
>the operating software: Isodat NT vs MassLynx, but I don't know how
>other hardware components(mass spectrometer, EA, GC, and respective
>carbonate devices) compare.
>
>I am particularly interested in the ability to measure carbonates via
>continuous flow and have heard that ThermoFinnigan's GasBench II
>operates well for these measurements. I have not heard to much regarding
>GV's MulitFlow Geo, and am wondering how it stacks up to the other
>carbonate devices (i.e. Kiel). I know precision drops with the gas
>benches compared to a Kiel system, but we are not doing paleoclimate
>work and a drop in precision isn't critical, especially given our
>research questions. I think GV and ThermoFinnigan both state that
>precision is about .1permil for carbon and oxygen isotopes via CF. Have
>any of you run carbonates using the MultiFlow Geo? Can large carbonate
>samples(500ug - 1500ug) be run on the MultiFlow? I know ThermoFinnigan's
>Gas Bench has an autodiluter, capable of reducing the signal to the mass
>spec, but do not know if GV's MultiFlow has this capability?  I suspect
>it does, but would be interested to hear any feedback on the
>subject........
>
>                              Regards-
>                              Bryan Taplin
>
>Bryan Taplin
>Environmental Scientist
>US Environmental Protection Agency
>NHEERL- Atlantic Ecology Division
>27 Tarzwell Drive
>Narragansett, RI 02882
>Tel. (401) 782-9607
>Fax (401) 782-3030

Dr Zheng-Hua Li
Senior Research Associate
306 G&G Building
Dept of Earth and Planetary Sciences
University of Tennessee
Knoxville, TN 37996
USA
Tel: 1-865-974-9622
Fax: 1-865-974-2368
http://web.utk.edu/~zli