Oxygen Peak missing in MS

[rodrigue]

That dip in the baseline could be related to an experiment I tried last week. I was trying to see if Nitrogen could be substituted for He or H2 as carrier gas in GC/MS. The chromatography we very good, but I lost nearly 90% of my sensitivity. It could be that when the Argon is eluting from the column it is suppressing the ionization in the source and it causes the loss of the analytes. That would also explain the dip in the baseline. Does the dip occur if you inject only Argon with no other gasses added?

Hi,

Finally I have done this test, and when I take a sample of only Argon the baseline is dropping too.
I understand that the ionization can be suppressed, but I am still able to see both methane and oxygen. I mean if this is suppressed should be suppressed always.

[rodrigue]

Hello rodrigue,
It seems you may have the wrong column for this application. Please contact Agilent at: 1-800-227-9770, select option #3, then option #3 again, and lastly option #1. Or send an email to GC-Column-Support@Agilent.com so that you can receive assistance for this issue.

Thanks for the advice, I have made some contact with Agilent before about the columns (I am base in Germany, so I haven't call the US number you gave me) and they only reply that I need a Wax column for BTEX and a Al2O3 Plot for hydrocarbons.
I mean they haven't been very helpful so far.

Thanks a lot anyway.

[James_Ball]

That dip in the baseline could be related to an experiment I tried last week. I was trying to see if Nitrogen could be substituted for He or H2 as carrier gas in GC/MS. The chromatography we very good, but I lost nearly 90% of my sensitivity. It could be that when the Argon is eluting from the column it is suppressing the ionization in the source and it causes the loss of the analytes. That would also explain the dip in the baseline. Does the dip occur if you inject only Argon with no other gasses added?

Hi,

Finally I have done this test, and when I take a sample of only Argon the baseline is dropping too.
I understand that the ionization can be suppressed, but I am still able to see both methane and oxygen. I mean if this is suppressed should be suppressed always.

Could you make a standard that is Oxygen and Methane in Helium and see if you have the same problem? That would let you know if the Argon is what is causing the problem.