I am using a ThermoFinnigan Trace GC with a Polaris Q ion trap mass analyzer and an AT-WAX column (from Altech). I am consistently observing sharp, spiky features in the background. They appear even when I do not perform any sort of injection, and their appearance time is consistent from run to run for a given temperature ramp program. I have tried switching septa and septum style; no change. The associated masses are higher than my analytes of interest, so I can set the mass window to avoid them, but I still want to know what causes these features. Thanks for any ideas.