Stable Isotope Geochemistry


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Dr W Meier-Augenstein <[log in to unmask]>
Reply To:
Tue, 10 Feb 2004 07:55:57 -0000
text/plain (77 lines)
Dear Claire,

This sounds very much like you're falling victim to one of the myriad of
idiosyncrasies of ISODAT_NT.

Call me a dinosaur but I positively hate computerisation. Bring back the
analogue vacuum gauge of the Delta S and the tune potentiometers that
were phased out after the Delta+XL is all I can say.

(1) The Auto-tune (or Auto-focus) feature only iterates in a small
window around the current set values. In other words, there might be an
even better tune setting than the one this function "finds". There's an
options' menu somewhere where one can define the "window" width but I
don't recall where just now. I don't use it being a more hands-on kind
of guy having been weaned on the old fashioned potentiometers.

(2) Unless you (a) safe the result of your tune AND (b) pass it on to
the gas configuration, the software returns to the old/original tune
settings previously associated with this particular gas configuration
every time you start a data acquisition using this gas configuration
(and it doesn't matter if it's a sample run or a time, HV, or magnet
scan in Instrument Control). This is what I think is happening to you.

Disclaimer: These statements are only strictly true for ISODAT_NT ver1.5
since I haven't found the time to install ver2 yet.

Hope this helps.



> -----Original Message-----
> From: Stable Isotope Geochemistry
> [mailto:[log in to unmask]] On Behalf Of C Bickers
> Sent: 09 February 2004 17:00
> To: [log in to unmask]
> Subject: Delta XP tuning
> Dear All,
> I am currently working on a ThermoFinnigan Delta XP coupled
> via a GCIII interface to a Trace GC , with ISODAT 2.0.  After
> tuning cup 3, with reference gas CO2, I can achieve a signal
> intensity of ~7700 mV for m/z 45. After the injection of a
> standard, or even after carrying out a diagnostic test, the
> intensity drops by an order of magnitude.  After tuning cup 3
> once more, it easily returns to ~7700 mV signal, but again
> drops to ~700 mV when the system is operated.
> Has anyone experienced any problems like this and can offer any help?
> Thanks,
> Claire
> ----------------------
> Claire Bickers
> Organic Geochemistry Unit
> Biogeochemistry Research Centre
> School of Chemistry
> University of Bristol
> Cantock's Close
> Bristol
> BS8 1TS
> UK
> Tel: +44 (0)117 3316795
> [log in to unmask]