Kathy,
We use UHP. The reference gas cylinders last an incredibly long time;  
so it isn't really that expensive in the long run.
-- 
Charlotte Lehmann
Assistant in Instruction
Bates College
Department of Geology
206A Carnegie Science Building
44 Campus Avenue
Lewiston, ME 04240
Phone: 207-786-6485
FAX: 207-786-8334


Quoting Kathryn Venz Curtis <[log in to unmask]>:

> Hi All,
>
> We are getting ready to measure the nitrogen isotopic values of N2O
> produced via the "Bug Method"  (i.e., Sigman et al. and Casciotti et
> al.).   I am looking into getting a N2O tank from our vendor to use as
> the reference gas.   What is the minimum grade N2O that is required for
> use as the reference gas?  Do I need UHP or can I get away with
> something less expensive? There seems to be a variety of options at a
> great range of cost.
>
> Thank you,
>
> Kathy
>
>
>
> -- 
> Kathryn Venz Curtis, PhD
> Stable Isotope Mass Spec Lab Manager, Senior Chemist
> Soil and Water Science Department
> 2169 McCarty-A University of Florida
> Gainesville, FL  32611-0292             Phone: (352) 392-1951 ext.242