I have a SciEx QTRAP 5500 which I use to quantify phenylalanine. I recently saw a drop in sensitivity on the order of 10-fold and reduced repeatability in my standards.

I conducted a full cleaning according to the manual which resulted in no change. I then replaced the electrode and when optimizing its location, I observed massive fluctuations of the detected Q1. I know the expected Q1 is 164. This would appear for a few seconds, then would not be detected at all for a while, then would appear again. Many other Q1 values would be appearing - seemingly at random - as well. A fluctuating TIC was also observed between 4E7 and 6.5E7.

Does anyone have suggestions on what may be going on here?