Recently we have been experiencing the baseline dropping below 0 in our chromatograms. To try to remediate this issue, we have been experimenting with changing the target % for m/z 219 and m/z 502 to 50% and 3% respectively. We have also tried 50% and 5% & 55% and 3% & 55% and 5%. There was an increase in EM volts with the m/z 219 at 50% and m/z 502 at 3% but once we tried that combination again, the EM volts decreased back to it's original EMV. Can tuning the GCMS too frequently cause the EM volts to be stagnant? Can running too many tunes affect the sensitivity/EM volts?
This was also our last resort. We have tried clipping the column on the GC and MS ends, changing liners, cleaning sources... just about everything. Please help!