Good Morning Everybody,
We're struggling to get good precision
with our GV Isoprime/Dual Inlet. We are running 100ug carbonate
samples/standards. We've achieved the specified +/-0.05 d18O (1 sd)
on some runs, but it doesn't last. Our last 4 runs resulted in
+/- 0.07, 0.12, 0.22, 0.09 d18O (1 sd).
The mass spec seems to be working beautifully
as indicated by the peak shape, all open analysis, and single cold
finger volume anlaysis with ref gas on both sides of the dual inlet.
We learned some techiques from our
esteemed and helpful GV service engineers regarding the carbonate prep
line. These include replacing the prep line and heating the prep line
between runs. We saw improvements in performance, especially after
heating the line. Unfortunately, the good data quality deteriorates
quickly (several runs). We've experimented with heating the prep
line continuously, heating between samples, and not heating at
all. Our latest experiments involve replacing the 1/16" ss prep
line with fat tubing (1/4" convoluted ss tubing). The fat tubing
showed promising results at first, but alas, has deteriorated again (above
data collected with fat tubing).
I like the rapid pumpdown and definitive leak
checking that the fat tubing allows. My thought was
that the increased conductance and lower surface area to volume ratio
of the fat tubing would be a great benefit.
When using 1/16" tubing, it
is standard 316 ss tubing that is cut with a
Any ideas or suggestions for further testing
would be greatly appreciated.
ICPMS Lab Manager
Department of Geological Sciences, Marine
Unviversity of California Santa Barbara
Barbara, CA 93106
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