Dear list subscribers:

        Help!  Our Fisons Optima IRMS has a problem that we have been
unable to fix.  Has anyone seen this before?  A brief synopsis:

        We noticed poor precision of organic carbon and nitrogen standards
in continuous-flow mode (using a Carlo Erba elemental analyzer), so we ran
a 24-hour time scan on CO2 from the EA's reference gas injector.  All beams
and ratios OSCILLATE synchronously with a period of ~30-60 minutes; the
amplitude of the major beam oscillations is ~1E-10 A (with a trap
current=200 uA tuning).  The story is similar for injected N2.  These
oscillations showed up suddenly, within a 6-day span of unuse.  We have
since found the same oscillations (with smaller amplitude) in a time scan
of CO2 in the dual inlet.

        We have tested everything we can think of in order to track this
problem down, without success.  If anyone has suggestions or has seen this
problem before, I'd love to hear about it.

Thanks much!

Bryan

______________________________________
Bryan Bemis
Department of Geology
University of California
Davis, CA 95616

Lab (916) 752-3311
Fax (916) 752-0951
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