Hello,
I am working on the installation of an Agilent ICP-MS 7700s equipment. I am only using He mode. I have tested No Gas mode and everything seems just fine. Also several CRM have been tested with acceptable results. However, when He mode is tested calibration curves and results don't make sense (calibration curves attached). Increasing the He flow seems to improve the problem in the so-called HEHe mode. The tune parameters used for each mode and some calibration curves corresponding to the three modes are attached to this question. I would be grateful if you can give me some advice about this issue.
The following two links may be helpful:
https://www.scientistsolutions.com/forum/analytical-chemistry-environmental-analysis-icp-icp-ms/he-mode-vs-no-gas-agilent-7700x
https://www.scientistsolutions.com/forum/analytical-chemistry-environmental-analysis-icp-icp-ms/low-sensitivity-he-gas-mode-icp-ms
Good Luck Oscar Balladares
Dear Oscar
What you see in He-mode is most certainly the loss in Na signal due to ion scattering after collisions with the gas. Ligther isotopes are usually suppressed more substantially by collisions as indicated by the low slope of your calibration curve. In HEHe mode extra kinetic energy is imposed to the ions before entering the collision cell and scattering loss is reduced. At the same time however, your KED performance may get worse.
You will probably see the same effect even more pronounced for Li, Be and B. The question is however why to use He mode at all for Na analyses. I wouldn't deem that necessary.
Hope this helps,
Bodo
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