Topic: No Signal on the Mass Spec


I am having a problem with my mass spectrometer. It is a Waters Acquity TQD. No signal is being detected but there is some noise. When I let water directly infuse through to the detector (meaning it does not go through the chromatogram), there is a peak at ~42 m/z. I tried directly infusing known standards, such as a Phenylalanine solution, and a concentrated solution of Antipyrine. No peak showed up except for the same peak at ~42 m/z. Interestingly enough, when I increased the flow rate, the peak height at ~42 m/z decreased. Decreasing the flow rate increased the peak.

Today, I replaced the ESI Probe, but I'm still having the same problem. Any suggestions would be helpful. I am planning to take apart the entire machine tomorrow and do a thorough maintenance check. If there are any books or good manuals on how to perform this take, that would be helpful too.

Please help me, and thank you in advance for your time.