This is a technical post. I’m writing for other scientists who use the same (or similar) instrument as I do to ask a technical question. I’m having a problem with the mass spectrometer and need the advice of others.
If the mechanics of isotope ratio mass spectrometry aren’t your thing, you might wanna stop reading now. If you’re interested in the types of challenges that arise with these high-falutin’ instruments, you might keep going.
I’m getting intermittent power fluctuations through the source. These are little 1-second-long sinusoidal waves of around 10-20mV. These are often overprinted on broader waves or interferences (maybe 100 seconds?) of around 50mV. These are wrecking our analyses.
There was an alarm on our UPS/power conditioner, so I had it serviced. I also cleaned the source while the instrument was shut down. There was nothing consequentially wrong with the UPS. The alarm was a pre-programed service alarm.
I restarted the instrument and immediately observed the same pattern.
I thought maybe it was a Gasbench thing, so for grins I switched over to the Conflo and observed the same thing. Notice, however, how the interference comes and goes.
After that, it seemed to go away. I tuned the instrument and got good results. I set it to run on-offs over night. Most of them look great. However, on occasion things would go wrong for a half hour or so, resulting in on-off sets like this:
I’ve cleaned the source and serviced the UPS, as well as done a hard reboot of the system since I had to completely shut it down for the UPS service. What am I missing?
If you have ideas, please let me know in the comments below or by e-mail to pennilyn (dot) higgins (at) rochester (dot) edu.