Sensitivity issues in "He" mode. Agilent 7850 ICP-MS

Hello. Dear colleagues, may I seek your advice about my problem?

I have sensitivity issues with Agilent 7850 ICP-MS in "He" mode. Usually, I carry out measurements a couple times a week. And before every measurement I have to purge the cell with helium at 12 ml/min via MassHunter settings (Cell maintenance) or by unscrewing the relief valve manually. If I don`t do that, signal intensities in "He" mode are very low, sometimes the instrument can`t even perform the tune in this mode because "Sensitivity is too low". Is it normal that I need to purge the cell every time or I have some malfunction in my instrument?

Also, recently we`ve installed Hydrogen line. And when working in two modes ("H2" and "He"), again, the sensitivity in "He" mode is quite low compared to some our previously obtained data, despite purging the cell with H2 (10 ml/min) and He (12 ml/min) simultaneously beforehand. So, I have the same question - what is the problem with sensitivity? In Element Selection settings we had Stabilization time 10 sec for He after H2, is it enough?

I should note, that for the Tune before acquisition in Startup configuration I always check only Torch Axis and Plasma Correction. Other Tunes I check from time to time. Is it OK, or I should check all Tunes (maybe except P/A factor) each time when I ignite the plasma? 

Thank you in advance for your ideas!

  • Hi,

    1. It is not normal, that you have to purge the cell gas lines every time

    2. Ou should perform at least following "Tests" during Plasma ignition: Torch Axis - EM - Resolution/Axis. But a performance report every day would be nice (and therefore you should select "lenses tune" as well)

    3. I think you are having a leak in the gas line. Are you closing the gas bottles every time? i would recommend not doing this. 

    You should check the Cell Gas Lines for leaks. to do so, do the following:

    Close the pressure regulators at the gas cylinders. with the instrument in standby, open the maintenance dialog from the "Cell/Raktion Gas Tab".

    Now you can set up a gas flow (12 ml/min for He and 10ml/min fpr H2). Leave this running over night (as it takes quite a loing time). If your gas lines are sealed correctly the meter readings should show a measured flow >0.2ml/min. If not, there this a leak. 

    Good luck


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