Wenbo,

This may be of some help.  A brief description of our method for analysis
of C13 and O18  in atmospheric CO2 on a dual inlet mass spec (Micromass
Optima) can be found at:
http://www.Colorado.EDU/INSTAAR/SIL/equip/air.html

A simplified  schematic of the instrument and extraction system can also be
found through the link  called  "The first"  -on the above page.
(It takes you to :
http://www.Colorado.EDU/INSTAAR/SIL/equip/diagrams/1stairsa.html)

An example of results obtained from our analysis of a network of sites can
be found in:  P. Ciais, P. Tans, M. Trolier, J.W.C. White and R.J. Francy,
A large Nothern Hemisphere Terrestrial CO2 Sink Indicated by the 13C/12C
Ratio of Atmospheric CO2,  SCIENCE, Vol 269, p. 1098, (1995).

Also, should you wish to calibrate your results with other labs, efforts
are currently underway to "normalize"  results between various labs that
measure lots of sites.  We are using  common cylinders of atmospheric air
standards, and an approach that involves the analysis of replicate samples
from the same sites by different labs for intercomparison.  To achieve
truely comparable results of say (+/- 0.03 per mil or less for carbon) over
the long term is a bit tricky.  You may contact us for details if you are
interested.

Best of luck,

Bruce
_________________________________________________________
        Bruce H. Vaughn, Stable Isotope Lab
        Institute of Arctic and Alpine Research
        University of Colorado  CB 450
        Boulder, Colorado  80309

        Office: 303-492-7985                 [log in to unmask]
        Lab:  303-492-5495                    FAX: 303-492-6388
_________________________________________________________

>Could anyone please help me to provide some references for stable carbon
>and oxygen isotope analysis of atmospheric CO2? Currently, I am working on
>on-line continuous flow PreCon-GC-MS analysis of atmospheric CO2. I'd like
>also to try other possible methods for comparison. Thanks in advance.

>Wenbo Yang
>MSRC, SUNY at Stony Brook
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