Dear Frank!

        We are doing similar C/N analysis with a CHNS/O 1108 + Delta plus.

        We have integrated the two equipments in our lab. We have enlarge
the lenght of the GC column of the EA from 2 to 3 meters to obtain better
C/N peak separation to enable the mass change operations be done without

        Also the amount of analysis that you have run with the column seems
to be quite large. You could detect the deactivation of the stationary
phase from haw long the analysis takes. We have changed our column when the
analysis time had increased around 30% from the brand new column.

        I hope these hints could help you.

        With our best regards,

Prof Dr. Miguel A. Maestro and the SXAIN/IRMS team
Universidade da Coruņa (SPAIN)

>Hi all,
>I would appreciate if somebody could point to me to the solution of
>the following problem: I am running a EA-MS  (Carlo Erba
>CHN 1110 + Delta C) for analysis of 13 C and 15 N in a variety of
>After switching the instrumen off and back on about two weeks ago,
>the CO2  showed a broad tailing, resulting in wrong results
>for 13C/12 C in standards and also too low measured C -
>concentrations. The N2 peak seems perfectly o.k., concentrations and
>isotope ratios. I have changed the O2 and carrier flow rates in all
>directions, put on new oxidation and reduction columns, renewed  the
>Anhydron water trap - but, alas, to no avail...
>Is it possible the chromatographic column needs to be changed (the
>instrument has done about 10000 measurements).
>Any help VERY welcome !
>Frank Pawellek
>Frank Pawellek
>Institut fuer Geologie
>Lehrstuhl fuer Sediment- und Isotopengeologie
>Ruhr-Universitaet Bochum
>Universitaetsstrasse 150
>44801 Bochum
>Phone: +49-234-700-5458
>Fax: +49-234-7094-571

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