Thank you for this suggestion.  However, it is unlikely that this is the
problem as we are using an Oztech hydrogen standard with D/H values in the -10
to -100 permil range.


>===== Original Message From Stable Isotope Geochemistry
<[log in to unmask]> =====
>Jonanthan - its most likely the H2 gas you are using for your reference -
>many, if not most,  North American suppliers of H2 compressed research gases
>have dD values lower than -1000 permil, making the peak very hard to find.
>You may need to find a different supplier or get someone to send you an
>ampoule of H2 gas with "normal" dD values. Len
>Leonard I. Wassenaar, Ph.D.
>National Water Research Institute
>Environment Canada
>11 Innovation Blvd.
>Saskatoon, SK
>S7N 3H5
>tel: (306) 975-5747
>fax: (306) 975-5143
>-----Original Message-----
>From: Jonathan Horton [mailto:[log in to unmask]]
>Sent: Monday, January 22, 2001 11:18 AM
>To: [log in to unmask]
>Subject: [ISOGEOCHEM] HD problems on Finnegan delta plus
>Hello all.
>I am using a new delta plus and am struggling to find hydrogen on it
>  (dual-inlet mode). I fill the bellows, and have looked for a peak with
>  BDAC value around 1000; I have tried retuning the source, but to no avail.
> The instrument has been used with the precon for N2O, where it worked just
>  fine. Specifically what I've done is:
>  1) close SGE and look at background on cups 3,2,and 1 using B-scan (a
>  little water, N2, nothing else) (I can't figure out how to do a B-SCAN
>  using cups 7 and 8, which would be more useful in this case...)
>  2) put Oztech standard H2 into inlet A1 and into bellows (pressure
>  increases in bellows to >100) (I've tried 2 different standard bottles to
>  rule out bad gas)
>  3) leave source tuning as was for CO2; adjust BDAC from 10 to 3000 in
>  ACON-D, INST-control
>  4) I find a very large peak (>10V) in cup 7 (mass 2) at around BDAC 2500;
>  small peak (0.2 V) in cup 7 at BDAC 1300; but at no point during the scan
>  is there ANY change in the voltage on cup 8 (mass 3) - it stays constant
>  0.001V
>  5) changed source tuning settings to match values given for old (returned)
>  delta plus for HD mode (I don't have a record of source tunings used for
>  HD during install); repeat step 3, result same as item 4
>  6) when I get a peak (the large one at BDAC 2500 and the small one at BDAC
>  1300), I've looked at the peak shape - cup 7 has a peak shape, cup 8 is
>  always a flat line.
>  7) I've done a baseline check to see if the amplifiers are working: the
>  baselines (source off) for cups 7 and 8 are around 185, voltage readings
>  are -10 and -8 (respectively). With the source on, baselines are 210 and
>  185, voltage readings +8 and -8. So, turning the source on does not change
>  the baseline in cup 8, but does slightly change it in cup 7. I hope this
>  doesn't mean there's anything wrong with the amplifiers on cup 8... ???
>  I'm assuming that I still don't have the right combination of BDAC, HVDAC
>  and source settings (X1, extraction, etc.) to find the right signal. What
>  procedure should I use to try to find the correct settings? I assume there
>  are standard starting points, and that one simply tweaks the knobs in a
>  particular order to find the right settings. Or, maybe not! Is there a
>  calibration procedure for HD? In short, what do you do with a new
>  instrument to find the HD peak?
>Thank you in advance for your help,
>Jonathan Horton
>Research Associate
>Department of Biology
>Virginia Polytechnic Institute
>  and State University
>Blacksburg, VA 24060-0406
>phone: (540) 231-8713
>fax: (540) 231-9307
>email: [log in to unmask]

Jonathan Horton
Research Associate
Department of Biology
Virginia Polytechnic Institute
  and State University
Blacksburg, VA 24060-0406
phone: (540) 231-8713
fax: (540) 231-9307
email: [log in to unmask]