Myles and others:

This is a topic I have asked to be included in the discussion session at
the upcoming Canadian CF-IRMS meeting in Montreal.

I have found that the use of quartz liners in the combustion tube in a CE
NA 1500 Series II NC elemental analyzer leads to significant broadening of
both N2 and CO2 peaks in both the TCD and the mass traces compared to the
peaks obtained when the liners are not used.  This is the case for both
samples and standards, regardless of whether the chemicals in the
combustion tube are new or used.  I have tried using the quartz liners
oriented with the pre-cut slots at the bottom and at the top, and have cut
additional slits in the liners using an Isomet saw as suggested to me by
Andrea Lini, all without success.  I'm sure Bruno Lavettre of Costech will
disagree with these comments, and I have a great deal of respect for Bruno,
but I have seen this happen repeatedly.  I wish the liners worked better,
because I agree that vacuuming chromium trioxide out of the combustion tube
is not a very pleasant alternative.  I hope that Paul Brooks might share
the design of his vacuum system at the CF-IRMS meeting and that we might
put the design on the Isogeochem web site.

Steve


>A note to all CF-IRMS users:
>
>Our lab performs C and N isotope analysis. The vacuum method of removing
>the ash from the combustion tube is used here. Some other labs use a
>quartz liner (swarf crucible) in the combustion tube  to collect the ash.
>In my opinion the use of a quartz liner seems to be an easier and less
>toxic way of removing the ash so I am investigating the possibility of
>using the quartz liner method, provided that the use of it does not
>degrade the resulting data.
>
>I will be grateful if many of you with experience regarding the following
>question will post your comments: In your experience does the use of a
>liner (swarf crucible) significantly (or insignificantly) affect the
>accuracy and/or precision of C or N isotope measurements?
>
>
>Myles Stocki
>
>Stable Isotope Facilities
>University of Saskatchewan
>Canada


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