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Hi Rich,

1) When you say you get the same response with no sample, do you also imply
you have triggered the EA to run through a cycle? Furthermore, if you
create a run without the EA, but keep the reference peak timing, do you see
the same result?

2) What if you inserted a third or forth reference peak? Would the trend
continue?

3) How many peaks are in your CO2 on/off runs?

4) Is the first peak of a CO2 on / off heavier?

andy

On Wed, Jan 25, 2017 at 2:04 PM, Harlow, Benjamin <[log in to unmask]> wrote:

> Hi Rich,
>
>
>
> Sometimes the issue is mechanical; i.e. the pnuematic piston to actuate
> the reference. The first time it is turned on after a bit of idle time, it
> can be slow to engage. You can easily check with the cover off your
> interface.
>
>
>
> If this is the case, you may not see a problem after several on-offs in a
> row. But in the amount of time spent idle for peak center, sample drop, N2
> peak, and CO2 peak, a crusty actuator could be more noticeable. We always
> prefer to use more than one reference pulse and evaluate with the latest
> pulse to account for allow for conditioning of the actuator. You could look
> at your std on offs early in the day or week and see if the first peak
> looks more disparaging.
>
>
>
> It seems I replace one SMC piston in our Thermo interfaces every few
> years. They are about $30.
>
>
>
> Cheers, Ben
>
>
>
> *From:* Stable Isotope Geochemistry [mailto:[log in to unmask]] *On
> Behalf Of *Travis Horton
> *Sent:* Wednesday, January 25, 2017 12:49 PM
> *To:* [log in to unmask]
> *Subject:* Re: [ISOGEOCHEM] Elemental Analyzer CO2 reference peaks
>
>
>
> Hi Rich et al.,
>
>
>
> Have you checked how your peak backgrounds are set?  I'm only familiar
> with Isodat, but depending on your software and its peak background
> detection settings you might find the cause of your disparity.  How much
> time do you have between your monitoring gas peak injections?  The first
> injection might still be coming down (zoom in a lot on the spectrogram)
> when the second injection goes in....even a mV or two difference can
> influence the values.
>
>
>
> Hope this helps!
>
>
>
> Travis
> ------------------------------
>
> *From:* Stable Isotope Geochemistry [[log in to unmask]] on behalf
> of Dabundo, Richard C [[log in to unmask]]
> *Sent:* Thursday, January 26, 2017 5:40 AM
> *To:* [log in to unmask]
> *Subject:* [ISOGEOCHEM] Elemental Analyzer CO2 reference peaks
>
> Hello,
>
>
>
> I'm having an issue with CO2 reference peak deviation during an Elemental
> Analyzer N and C run. Two CO2 reference peaks are produced following the C
> sample peak. Originally, the first peak was consistently ~1.1‰ lighter than
> the second peak. After creating a new N2 to CO2 jump calibration, the first
> reference peak became consistently heavier than the second by about 0.6‰.
> We have sufficient distance between the sample and reference peaks, and the
> same issue results even if no samples are loaded. CO2 on-offs are fine,
> with a standard deviation of about 0.04‰. Does anyone know what may be
> causing our disparity?
>
>
>
> Thanks,
>
>
>
> Rich Dabundo
>
>
>
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-- 
Andrew Schauer
206.543.6327
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*http://isolab.ess.washington.edu/ <http://isolab.ess.washington.edu/>*