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