Re: Cup configurations on MAT
252
You may need to move your cups, but if you are going after
natural abundances of 15N15N there is another, potentially more
important issue. The filament in your instrument contains a thin
oxide coating that will emit CO from reaction with trace hydrocarbon
contaminants and NO from reaction with N2 analyte. These are low
enough in abundance that you might not notice their contribution to
measurements of singly-substituted molecules, but they can introduce
large systematic errors in analyses of doubly-substiuted isotopologues
(which typically make up only a few ppm of the analyte gas).
This issue can only be ignored if you are planning to analyze highly
enriched gases.
John
Hi
All,
I
am attempting to add m/z 30 to my nitrogen analysis. I have managed to
get the mass added in the ratio editor (thanks to a previous posting
by Gerald Olack in Nov 2004), however, I do not know which cup to
assign the mass. At present, my cup configuration for nitrogen is set
to cup 2 for m/z 28 and cup 5 for m/z 29. This was determined by a
Finnigan technician during install. This instrument has 6 cups
installed and I have tried placing m/z 30 in cup 6 but I get no
response in cup 6 when I check this with CO or N2 gas. My CO2
configuration uses cups 2 (m/z44), 4 (m/z45), and 6 (m/z46),
shouldn't N2 be the same cups but different magnet step? I have tried
this and get no response on any cups. Anyone out there with a MAT 252
and has managed to add m/z 30? Any help would be greatly
appreciated.
Brian
Jones
Stable
Isotope Ecology Lab
Eller
O&M Bldg. Rm 408
Dept. of
Oceanography
Texas
A&M University
College
Station, Tx. 77843-3146
Lab
979-845-8916
Cell
979-820-2745