Kris:

I am not that familiar with your Finnigan setup, nor did you mention
whether you are having problems with C, N, S standards, but have you
checked recently the isotopic composition of your various reference gases
that you inject independent of the continuous flow interface, i.e., by
dual-inlet analyses?  Usually reference gases become heavier as they are
used, in which case your standards would become heavier, not lighter, but I
suppose its possible for the opposite to occur.

Steve


>Hi
>I have a Finnigan delta S with a Hereaus combustion unit and
>trapping box. My values for standards have been getting
>lighter and lighter over the course of a few weeks.
>The blank is small so what else could be causing it? I have
>changed the combustion tube, no defference.
>Any suggestions are welcome.
>thanks
>
>kris
>
>
>
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