Dear Listmembers,

sorry, I should have given some more details about our machine. We´re
running a IR-laser-fluorination CF-IRMS. It means, that we heat our
samples in F2-atmosphere using a 30W CO2-laser (lamda=10600nm). After
liberating oxygen from our sample (0.2-0.3mg). After trapping F2
on KCl and freezing Cl2 in a cold trap, we collect our oxygen on
a 5A molecular sieve at temperature of liquid N2. Then the oxygen
is transported by He carriergas to the Europa 20-20 mass spectrometer
an we measure m/z 32,33 and 34 on three collectors in CF mode.

My problem was the drift on d18O-values up to 2.5permill.
William wrote, that the temperature in the lab should be constant
and, indeed, that may be a problem, since our lab at Bonn is not
air conditioned,

Andreas

--
Andreas Pack
Minerlogisch-Petrologisches Institut und Museum
Poppelsdorfer Schloss
D-53115 Bonn (Germany)
Phone: +49-(0)228-739782
Fax  : +49-(O)228-732763