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 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]
audaces fortuna iuvat