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Analysis of Ag, Sb, Sn (ICP-MS Agilent 7900)

metallica

Hi everyone. Im using the Agilent 7900 for the analysis of a bunch of analytes in water samples without any problems, except for Ag, Sb and Sn. Im having a problem with the calibration curves of these three analytes because the calibration curves are not linear, it almost seems theat I swaped the points of the calibration between each other. So of course I tried to clean every part, changed all tubings, I have new conuses, every reference material and solution are fresh. Im using macerated plastic bottles for storage of the solutions, adding HNO3 into every solution. Im using He mode, and I chose the following isotopes: Ag 107; Sn 118; Sb 121. The points of the calibration curves for the Ag and Sb are 1; 25; 50; 75; 100 ppb and for the Sn 10; 250; 500; 750; 1000 ppb. And I measure them together with the following analytes: Li, Be, B, V, Se, Sr, Mo, Ba.  So I was wondering, if anyone has a similar problem. Or someone has an idea what should I try. Thank you very much.

  • 0

    Hello !

    Could you provide some calibration snapshots? Which points (lower or higher) are showing that behaviour?

    These elements come in the same mother calibration solution? Do you think you can have any source of chlorine from the plastics?

  • 0 in reply to Agilent

    Hi Rodolfo, the behaviour is very random. Mostly the higher points showing that behaviour. I am fighting with it for almost a year. Sometimes helps when I make fresh calibration, but in the next analysis its bad again, or sometimes the calibration curve is beautiful, but the CRM for the QC check is horrible. And I dont change anything in the method between the analyses. I use always the same type of bottles, I soak them overnight with 10% HNO3. And when I am making the calibration curve, I always use a high purity single component solution (1000 mg/l) for every single element. So I dont really know, where are we doing mistakes. Do these elements have some memory efect? Or are they that problematic elements, that they need some special care, maybe other settings in the method?   I print screened some calibration curves, the bad ones and the good one too.   Thank you.

  • 0

    Hi Metallica,

    This is a typical problem of the chemical stability of the elements. Ag, Sb, Sn aren't good stable in low concentration HNO3. However if there is some HCl present then the stability is far more better. I don't know the HNO3 concentration but try to repeat the test when adding extra (1%?) HCl to all the blanks and standards. probably it goes much more better.

  • 0 in reply to edgarvs

    Hi Edgar, thank you for your response. I actually thought about the HCl, but I always assumed that the ICP MS doesnt like HCl. But I definitelly try it. Thank you.

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