switching from N2 carrier to He

[mblack]

Hi everyone,

I'm trying to troubleshoot a GC-ECD with N2 carrier set up to run N2O using porapak Q columns. I think I have a leak but want to check where and what the leak is using a continuous flow isotope mass spec and Argon. In order to do this I will need to run He rather than N2 as the carrier. Will this pose a problem for the GC or columns, or subsequent analysis when I switch back to N2 as the carrier? Would 24 hours be sufficient purging of He?

Thanks in advance,
Matt

[AICMM]

Matt,

Switching to helium while you hunt for a leak should not harm anything. Your ECD might be unhappy since there is no beta moderator but you could turn it off while you find your leak. You might need to let you column re-equilibrate after you switch back but it should not take very long.

By the way, what levels of N2O are you looking at with the ECD?

Best regards.

[mblack]

Thanks for the reply. The GC is purging with He as I write this. I've capped off the ECD and will run the tests with it off, thanks. We are looking at N2O concentrations typically around 300ppb+.