HI Greg--

Werner has a nice diagram in his paper:
Isotopes Environ. Health Stud., Vol 39, No2, June 2003, pp 85-104.  The 
online 18O/16O analysis: development and application.

Basically, put a length of tubing and a four-way switching valve in 
between the reactor and the GC.  You can loop the tubing around and 
stick it into a liquid N2 dewar during a run.  Afterwards, remove the 
dewar and switch the valve to warm it up and vent any trapped material 
out (not through the GC).  The valve should be rigged up with another He 
source (T off the purge line) so there is always He flowing through the 
GC and to the Conflo.   If you're doing anything fancy, e.g. online 
fluorination, you'll need the acid trap in line before the cold trap. 

take care

gerry


Greg Cane wrote:

> I'm looking at inserting an H2O/CO2 trap after an on-line pyrolysis 
> reactor (TC/EA) based on Saurer's 1998 Paper (Oxygen Isotope Analysis 
> of Cellulose: An Interlaboratory Comparison; Anal. Chem.) 
> Unfortunately, there's not much detail in the specs. of the trap, i.e. 
> how long it is, diameter, trap composition (glass, stainless steel?), 
> etc. Can anyone offer details on what works for them?
>
> Much appreciated,
>
> Greg
>