Sensitivity loss in 4000 QTRAP

[analyst33]

Dear Colleagues,

I observed a drastic sensitivity loss (decrease in intensity of both peaks and base line) in 4000 QTRAP (AB Sciex) mass spectrometer. It happened during 1-2 days. During the sequence of LC-MS analyses the intensity dropped about 2 orders of magnitude between the first and last samples (typical samples, analysed many times before with the same method). It looked like a case of contamination. However, the standard cleaning procedure did not help. PPGs tuning mix gave peaks of very low intensities. The drift test didn't prove any contamination. Changing the detector voltage also did not help. Even the electrode was replaced for a new one (although the old one seemed fine) - with no effect. It was the moment for the service to come. We had a suspicion that electronics can be the reason of sensitivity loss. The service technician checked electronics and said that it is not the reason of the problem.
Do you have any possible solutions to my problem or any suggestions? I would really appreciate any suggestions and advices.

[gassensmith]

You checked that you still have a good vacuum?

[zxl02]

Hi, What is your standard cleaning procedure? Does it include cleaning both sides of the orifice? If yes, you may go ahead to check the CEM itself and further the signaling board.