All,

Any thoughts on a procedure for measuring isotope ratios in
gas-phase NO2?  Making the 15N measurements is easy and published methods
exist.  But the 18-O measurements?  We have collected NO2 with a mist
chamber to produce nitrite, but this will produce a rapid exchange of
oxygen with water.  So the question really is a two-step one:

How to collect NO2 without fractionating it for oxygen?
How to measure the isotope ratios?  Pure NO2 could be introduced into the
source, I suppose, but has anyone done this?

Comment appreciated!

Eric Steig