Ag Calibration Curve on ICP-MS 7900

Hello everyone, 

I am having trouble to get a good calibration curve just for Ag. 

my standards are 0, 25 ppb, 50 ppb, 75 ppb, 100 ppb and 400ppb. And the matrix is 2% HNO3. 

All the other elements are good I get R=0.9999 but for Ag it is terrible. I have R=0.1123 like this. And I am not sure what to do! 

Thank you for your help 

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  • I did some more looking into the topic - please see the below link for ICP-MS general applications which I found helpful. Small trace amounts of HCl are not good for Ag as it will form AgCl which is true and I believe may be happening in your case. However, see below taken from the Wiki. Sorry if I might have caused some confusion 

    • Though adding a little HCl may precipitate Ag+ as chloride, adding more brings it back into solution as [AgCl2]- or higher Cl- complexes, depending on the Cl- concentration. By having Ag complexed with HCl as a source of Cl-, you shift the equilibrium away from free Ag+ ion to silver chloro-complexes. This slows the rate of silver loss by reduction.
    • Though solubility rules say that some metals (Ag, Pb, Hg) precipitate as chlorides, due to presence of chloride ions in water. In water, both Ag and Pb would indeed precipitate as chlorides. The situation is different in acid. AgNO3 is water soluble, but Ag+ is easily reduced to Ag(metal). The reduction is acid catalyzed or photo catalyzed, so nitric acid alone is not good for Ag.

    community.agilent.com/.../tips-and-tricks-for-icp-ms-general-applications

  • Thank you for sharing this. 

    First, my plan is to try not to use the standard which contain HCl 

    If it doesn`t work I will try to add HCL with Nitric when I prepare the all standards. 

    I hope one of them works :) 

  • If you decide you need to add some HCl, you only need 0.5% to keep the Ag in solution and not precipitate out. Best of luck!

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