ICP-MS 7900, mercury dilution false concentration

Hello Everyone
I have an issue with ICP-MS 7900 on mercury analysis. If we run 1:1 dilution after digestion the results are OK but when we need to analyze the further dilutions I get high concentration of mercury and amazingly the RSDs are not high to say it's a false pulse. Does any body had a similar experience? Please let me know if you needed further information.
Thank you

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  • HI,

    In the past I also had strange results in my Hg calibrations and samples.

    My sample were always acid digested in nitric acid, resulting in a total 100x dilution which was used to introduce into the ICP-MS. My calibration for Hg was usually from 0 to 10 ppb Hg.

    To get rid of the bad calibrations and strange sample measurements I started (advice Agilent) to rinse the sample probe, after each blank, CAL and sample, first in 5% NH4OH +0.2% Triton X-100, then a few seconds in milliQ water and then in 14% nitric acid. So you rinse in a range from high pH to low pH..

    Now my Hg calibrations and sample concentrations are always OK.

    Also Hg solutions are not that stable in plastic containers. CAL and sample solutions also need some HCl added.

    Hope this will help you a little bit Fingers crossedSlight smile

  • 14% HNO3 might be a little too much. Please keep in mind that the nickel cones can handle up to 10%. 

  • OK, thank for the warning, that might be true. However I use Pt cones and have no problems at all with 14% HNO3.Relaxed

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