Thank you to everyone that has replied to me on this issue.

The solution, if not the explanation, came in performing a new mass 
calibration. The old one seemed fine, always dropped right on top of 
the peak before centering, so I'm a bit at a loss as to why this 
would have an effect. If it was off I could see how it could affect 
the calculation for the jump....

Paul


At 06:52 PM 04/02/2009, you wrote:
>Paul
>
>We have had this issue and it normally ends with the filament blowing or the
>need to clean the source.  We also see the intensity of the std peaks begin
>to drift as well.
>
>Occasionally after the jump, the CO2 HV and magnet drop out and the filament
>turns off (not blown).  To alleviate that we need to delete the CO2 gas
>config under Editors, then Test Jump, then add a new gas configuration (CO2)
>and manually enter the magnet value.  This usually solves that issue of
>drifting C numbers after the jump.
>
>Mark
>
>
>Mark A. Teece
>Associate Professor
>Department of Chemistry
>SUNY-ESF
>http://www.esf.edu/chemistry/teece/
>Director: Environmental Science Stable Isotope Laboratory
>http://www.esf.edu/eassil/
>
>-----Original Message-----
>From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On Behalf
>Of Paul Eby
>Sent: Tuesday, February 03, 2009 4:57 PM
>To: [log in to unmask]
>Subject: [ISOGEOCHEM] drifting peak jump
>
>Members,
>
>I'm running d13C and d15N by EA on a Delta XL. Recently, it appears
>that the peak jump is shifting over the course of a rack:
>
>After calibrating the jump, C and N are both initially fine. As time
>progresses, C values get worse while N stays fine. Runs performed
>with no peak jump, C only, are also fine. Redoing the jump
>calibration resets the problem.
>
>Can anyone suggest a cause or solution?
>
>Paul Eby
>University of Victoria
>
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