Hi Jennifer,

What difference in peak size are you getting between your tin blank and
your no tin blanks on the EA chromatogram?  I don't have data in front of
me, but using uncleaned cups from costech, I think ours are somewhere
around a ug.

-Brett

At 05:01 PM 3/14/2003 -0800, you wrote:
>Hello Everyone,
>
>I have a problem with my mass spectrometer - EA system.  When we run
>empty tin cups we are getting a higher than normal background for
>beam 44 (6 to 9 E-10).  I've tried different batches, sizes and types
>of tin cups and still the same problem.  Interestingly, when we run
>real blanks (i.e., no tin cup is dropped, but everything else remains
>the same) we don't see the high background.  This leads me to believe
>that the tin cups are contaminated.  Has anyone else noticed a
>problem with the tin cups supplied by Elemental Microanalysis Limited
>beginning in December 2002?  Can anyone think of what else may be
>causing our high background if it is not the cups?  I have changed
>the gases (O and H) and the He purifier, heated the GC column to give
>it a cleaning, changed the combustion column using both pre-packed
>columns and columns we packed but still the problem persists.  I've
>checked for leaks on both the EA and mass spec and even cleaned the
>source.
>
>Any help would be greatly appreciated.
>
>Jennifer
>
>
>------------------------------------------------------
>Jennifer Mckay
>Agente de Recherche / Research Associate
>GEOTOP - Universite du Quebec a Montreal
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>Montreal, Quebec, Canada
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>
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----------
Brett Longworth
Department of Geosciences
University of Massachusetts

"Pluralitas non est ponenda sine necessitate"
                      -William of Ockham