Hi,

The problem definitely lies in the nafion water trap as HCO2
is formed in the ion source because water is reacting with
the CO2. The reason that you still see an increase in mass 45 and 46 even
after changing your Nafion trap seems to be that the capillary going from
the water trap to the ion source is saturated with water as a result of
the failure of your first nafion trap. Subsequently, the CO2 is still
reacting with the remaining Water after the trap. I recommend using a
heat gun to heat up the capillary going from the trap to the ion source
thoroughly,including the open split, making sure to shut off the on/off
valve that leads directly to the souce so that the water vapor won't
end up there (you can also disconnect the capillary that feeds in to the
source while evaporating the water). Hope this will help.

Nabil Saad

On Thu, 20 Jul 2000, Paul Eby wrote:

> Hello all,
>
> I'm hoping someone can shed some light on a problem I am having (GC-IRMS,
> MAT252). My background levels for CO2 are elevated, but on masses 45 and 46
> only. The source seems to be my Nafion trap, as the 45 (and 46) signal
> increases drastically (perhaps 200mV) when I heat the trap, and falls to
> normal when the trap is removed. Mass 44 is unaffected throughout all of
> this (~9mV).
>
> I replaced the Nafion tubing, but am still getting the same problem.
> Another trap in the lab made from the same batch is working fine. Does
> anyone have any suggestions? What compound can give masses 45 and 46 but
> not 44? Nafion is a fluorinated polymer, but the only fluorine compound I
> can dream up that has a mass of 45 is NCF. Doesn't seem very likely....
>
> Paul Eby
>
> [log in to unmask]
> Biogeochemistry Lab
> School of Earth and Ocean Science
> University of Victoria
>
> phone: 250-721-6183
> fax:   250-472-4620
>