Baseline disturbances in the TIC

Discussions about GC-MS, LC-MS, LC-FTIR, and other "coupled" analytical techniques.

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Our GCMS (6890/5973 EI) contains two columns, one that goes to the MS and another that goes to the TCD/FID detectors. Both columns are 60m GS-GasPro. We use a gas sampling valve that injects the same sample onto both columns. The baseline disturbance is only seen in the TIC, there are no noticeable changes in the baseline for the FID or TCD channels. There are no unusual mass fragments showing up other than ones associated with air (18, 28, 32, 40, 44).
The baseline disturbance started to occur after analyzing samples of CF4 gas. I injected CF4 from one cylinder three times and the TIC was normal for each run. On the second cylinder of CF4 the baseline disturbance started to occur. We have been told that it's possible there is oil in the gases from a compressor but it is not known for certain. I'm wondering if this is what is causing the issue. I have tried to recondition the column several times and removed the first ~15cm of the inlet side of the column connected to the MS. The baseline disturbance is still occurring. The third image is the most recent helium injection.



I figured out it was the filament. I switched from filament 1 to 2 and the baseline is normal. Time to replace the filament.
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