Paul,

      Yes, I put a small plug of quartz wool on top of the chromium oxide
and another in the bottom of the insert.  I haven't had an insert stick
yet.  I routinely use the inserts with the slots at the bottom but I've
tried them upside down (slots at the top) and they seem to work just fine.
You might try that just as a test  to see if sample residue seeping through
the slots is the problem.  ---   Steve






                      Paul Eby
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                      Sent by: Stable          cc:
                      Isotope                  Subject:  EA insert tubes
                      Geochemistry
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                      UVM.EDU>


                      09/25/2004 03:22
                      PM
                      Please respond to
                      Stable Isotope
                      Geochemistry






On our Fisons 1500 EA, we generally use insert tubes to collect sample ash.
Lately though, I've been having trouble with them breaking when I try to
replace them.

They don't slide right out - they are at first stuck at the bottom, and
when I try to wiggle it loose, it breaks near the bottom leaving a large
chunk inside. That means replacing the entire combustion tube. I'm not
running anything unusual in terms of samples, N and C in tin capsules,
sediments and freeze dried marine tissue.

The inserts have the slits cut into them, so I suspect that sample residue
is seeping through and fusing with the quartz outer tube. Has anyone else
experienced this, and perhaps have a trick or two? Do others put a small
plug of quartz wool on top of the chromium oxide?

Paul Eby
University of Victoria