Marc,

>  I see vast nonlinearity when analyzing a water sample. Reference 
>and sample peaks look fine and sample peak intensities are as 
>expected for the sample weight. It seems like, in contrast to the 
>reference gas ratio calculations, the H3 factor is not included in 
>the ratio calculations for the samples. The technician and I have no 
>more ideas. It is the first time D/H is measured on this machine.
>
>First of all: Is the H3 correction for the samples commonly 
>calculated automatically by the mass spec software or do you have to 
>correct the sample ratios manually for the H3 contribution?
>(Perhaps there is someone using the same isoprime mass spec and 
>could tell me about some hidden places in the Ion Vantage software 
>where a simple tick could solve all my problems...??)

If the Ion Vantage software is similar to the MassLynx software used 
to run an Isoprime, there is indeed a box that needs a tick for the 
software to use the H3+ correction factor when calculating a final 
delta value.

In MassLynx, you go to Edit Species, select H2, choose Reference Gas, 
and then the Molecule tab.  In the H3+ Correction section, there's a 
box labelled "Enable" which needs to be checked for the calculations 
to use the H3+ correction factor.  Incidentally, the "Use H3+ 
calibration data" box must have a check for the software to 
re-calculate the H3+ correction factor when you perform the routine 
to measure the H3+ correction factor.  I haven't used or seen the Ion 
Vantage software, but I imagine that it has something similar.

I hope this helps, and good luck!

Cheers,
Simon


-- 
*****
Simon Poulson
Research Associate Professor
Dept. of Geological Sciences & Engineering MS-172
University of Nevada - Reno
1664 N. Virginia St.
Reno, NV 89557-0138. USA
(775) 784-1104
Fax: (775) 784-1833
[log in to unmask]
http://www.mines.unr.edu/isotope/simonhome.html
*****