Dear List Members

As I understand it, the Isodat software does not include m/z30 in its 
calculation of del15N/14N and thus this step has to be done off-line. Using 
the the peak areas from Isodat and the equation del = 
[(Rsample/Rstandard)-1]*1000, I get a value of 63 per mil for air. I feel 
I'm making a simple mistake somewhere, but can't think where. Can someone 
please point me in the right direction?

Also, I've just started measuring CO2 on a Trace GC Ultra with a 25m 
Poraplot Q column. The samples are headspace gas from sediment core 
incubations. The GC method I'm using is isothermal (35C). There are two 
peaks, the first of which is all m/z46 and tends to be non-Gaussian, the CO2 
peak elutes second at about 150s. Would the first peak be NO2? Why would the 
peak shape be so poor?
Thanks in advance for the help!

Melissa..

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Melissa D. Bautista
IRMS Research Technician
Centre for Coastal Biogeochemistry
Southern Cross University
P.O. Box 157 Military Road
Lismore NSW 2480 Australia
phone:  +61 266 269 565
mobile:  +61 431 928 278
email:  [log in to unmask]
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audaces fortuna iuvat