Hi all,
We have a 6546 QTOF in house and recently I have noticed that the baseline of my runs is pretty high. I have cleaned the MS source very well and during tuning, I do not see any contamination, therefore I think it is coming from the LC side. We have replaced the pump heads and degasser recently so that also does not seem to be the issue. I have used a new column also, but the issue persists. I am not sure what is causing this high baseline. Any suggestions on how to resolve this? 
I did a system tune a month ago but have not performed detector gain adjustment. Could you please explain how to do so?
Here are the MS pictures
When in standard 3200 m/z mode, it is one of your options. It happens as part of a system tune also. It resets the gain so your baseline MS scan data is at 0, It is hard to see the baseline with the scans you shared.
Your reference ions look pretty abundant. You may be able to use a 1:10 dilution of the reference solution in 95:5 ACN:Water.
Is the change in the TIC abundance due to a change in reference ion abundance?
