Ion 191 baseline hump

[radwanagdy]

Hello,
I ran a whole oil on the GCMS,the separation,resolution and everything are more than perfect except ion 191,there is a baseline hump in that ion.the injector type is cool on column and the oil was run on a new column Also,there was no leak.

Any suggestion
Thanks

[rb6banjo]

Does the "hump" go away if you bake out the column and run a blank (no sample injection)?

Is there a chance that your sample contains a large concentration of 2,6-di-tertbutyl phenol? The base mass is 191. It's a common antioxidant.

[radwanagdy]

Hello,
Yes the hump exists in the blank and I did a conditioning for the column but nothing changed.Also I've tried different oils but the hump exists in all and by the way these oils did not show any hump in their previous runs.

[James_Ball]

I was thinking sulfur but it has a peak at 192m/z, if it is 191.5 or above maybe that is the culprit.

Have you tried replacing the inlet liner or trimming about 10cm from the front of the column?