Hello,
I have a problem with signal stability in LC-MS/MS apparatus. It was turned off during the summer break and after turning it on again last week we can see a dift in signal for analytes that we did before the break. This loss is around 30-50% in every sample (around 7 min). Noise also is lower with every sample. We also noticed that after changing polarity back and forth for consecutive samples signal was higher over time. Then after few samples in negative ion mode signal begin to fall again.
Ion source was cleaned before first analysis but after turning it on.
Can we do something about this problem without hiring a service technician?
1.png is a TIC over 10 min with calibration solution.
Thank you for help.
What kind of mass filter is involved there? If it's a quadrupole mass filter, a slowly decaying signal might indicate that one or several of the rods may be contaminated with an insulating layer. In that case you can polish them with cerium dioxide polish, but make sure you don't deform them.
For me, the increased signal after chaging the polarity is the sign of ion charge or ion burns in the MS.
I work with a Waters instrument with stepwave technology, and in such cases, I wash the stepwave cautiously.
If the problem is still there when stepwave is clean, then the quads are probably dirty. Therefore, you will have to hire a service technician.
You can't do anything beyond what you've already did. I wanted to suggest that you clean the source, you did that. Call your service provider and ask for a preventive maintenance.
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