Dear Zheng-Hua,

What were those modifications in hardware and software that reduced your
memory-effect? This way it does not tell us very much why and how you
obtained this result. I am interested (and probably some others) to see a
bit more details...

Regards,
Pier.

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> 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
>
>