Chromatography Forum

Hello!

I'm a new member !! I'm working in France.

I'm using a GC/MS apparatus (7890b+MSD5977E).

We tried to change the carrier gas Helium to Hydrogen but we are getting an abundance of the 69 ion in all traces that we cannot tune out, this affects the library identification.
The standard spectra tune seems to be ok.(see below the pic)

May you help me please ?

Best regards

Emmanuel

Nobody got an idea please

If I understand you correctly you have ion 69 in all your samples in the backgroung.

Maybe PFTBA valve is leaking ?

That's right in each samples...
Gonna check this valve

Thanks

If you switch from Helium to Hydrogen you will have quite a large amount of background ions when you first begin doing analysis. It takes a few weeks for the Hydrogen to clean out any and all contaminates from the gas flow path(it cleans really well) then once it reaches an equilibrium you will see better background.

If you scan in manual tune with the calibration gas valve closed, you will probably see a lot of ions present at first, over time they will be less and less. It looks like hydrocarbon background is high until it flushes out.

If you switch from Helium to Hydrogen you will have quite a large amount of background ions when you first begin doing analysis. It takes a few weeks for the Hydrogen to clean out any and all contaminates from the gas flow path(it cleans really well) then once it reaches an equilibrium you will see better background.

Can you use this to clean your flow path, even if you have no plans to switch to hydrogen for the analysis?

I ran one instrument on Hydrogen for a month or so, and when I switched back to Helium it had a super clean background when scanning with the cal valve closed. It would seem to work quite well to clean up a system, just takes a long time to do it. If you were to run Hydrogen any time the instrument was in standby, that would probably help keep things cleaner than normal I would imagine.