Bettina,

We also measure O2 by continuous flow (as you know) and we do not see
such drift. Measured ratios for reference gas injections, for example,
are very stable for days, weeks, months, and even years. Your drift is
not "normal" in this sense. As your values indicate that 17O/16O is
changing independently from 18O/16O it would appear that part of the
problem may be moisture? How is your drift measured?

-Ed Young




Hagen 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