How many counts are you seeing at 4.5 and 220?
If it's a couple of counts then it maybe a tuning issue.
When did this issue start? Can you revert back to a tune file that gave you good background?
Old cones, even though cleaned, can sometimes give you elevated background too.
It's also worth running a Detector Cross Calibration to ensure the Discriminator is set correctly.
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From: PLASMACHEM-L: Analytical Chem.(ICP's, DCP's, MIP's). <[log in to unmask]> On Behalf Of Prasad Lavisetty
Sent: Tuesday, June 26, 2018 9:10 PM
To: [log in to unmask]
Subject: High Background at 4.5 and 220 mass
We have Thermo IcapQ ICPMS, recently we are facing problems with high background at mass 4.5 and 220. The performance at both standard and KED modes are failing in background (both mass 4.5 and 220). I cleaned the cones, nebulizer and spray chamber. I didn't touch the torch and lens. Still the performance is not meeting criteria. Can anybody suggest to solve this problem.
Any suggestions greatly appreciated.
Scientist, Teva pharmaceuticals, Inc.