Tao,
   In addition to the previous issues, if these are air samples and your 
interested in the 1515 (30) your going to have significant interference 
(relative to the 15 abundance) from 16O14N made in the source

greg

Quoting Tao Fang <[log in to unmask]>:

> Dear All:
> 
> I have a question on N2:Ar ratio measurement. Is it
> possible to measure enriched N2 isotope (mass 29 and
> 30) by comparing with Ar peak? Whether all dual inlet
> mass spectrometer can measure mass ratio of 29/40 and
> 30/40, just like 28/29 and 28/30? or any special
> modification is necessary?
> 
> Any suggestion is welcomed!
> 
> Best regards
> 
> Tao
> 
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