Stable Isotope Geochemistry


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Gerard Olack <[log in to unmask]>
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Stable Isotope Geochemistry <[log in to unmask]>
Wed, 10 May 2006 00:55:41 -0400
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HI David--

Dynamic BGD is supposed to integrate peaks that are on a sloping 
baseline.  Roughly, it finds sections in the runs that are "baseline" 
then connects them with a line that has a slope.  If you click on the 
"Dy" button, it will show you the dynamic background that's being used.  
Play with it. If the step width is too small, it will set a baseline 
point on the tail of a peak (not good), and if it's too large then it's 
no better than individual background.  I haven't had a chance to play 
with it on the newest patch, but it didn't deal well with abrupt changes 
in baseline, e.g. turning dilution off, and it didn't respond to the 
"start integration" times set in the method.  It was also buggy in the 
early patches, so we always collected data using the individual 
background--then reintegrated them if Dynamic BGD was needed.  You can 
check the Isogeochem archives under GC-IRMS Questions, namely item 
#9970, for more details.

take care

David Harris wrote:

> Isodat 2.0 for chromatography peak detection/evaluation offers several 
> background correction modes but I can find no explanation as to what 
> they various modes actually do.  Has anyone figured this out? I am 
> particularly interested in understanding the mode ' dynamic BGD' and 
> its parameter 'step width'