At 01:41 PM 5/11/99 +-200, you wrote:
>Hi everybody,
>I need some information about the drift (and drift corrections) of
con-flow mass specs. We measure O2 and observe a drift in 17O values up to
10 permil and in 18O up to 3.5 permil during a day. The values get steadily
lighter. Is this the normal range? How can it be corrected?
>Any information will be helpful.
>thanks in advance
>Bettina
>

We've seen drifts such as this in d13C measurements that are attributable
to high water levels. Try monitoring water for both drift and intensity,
and elliminate if high.

There is a good paper on the problem: "Water-Induced Errors in
Continuous-Flow Carbon Isotope Ratio Mass Spectrometry" Kirsten J. Leckrone
and John M. Hayes.


Paul Eby

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School of Earth and Ocean Science
University of Victoria

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