Frozen ati icp test samples

Discussion in 'Reef Chemistry by Randy Holmes-Farley' started by Rajil, Feb 5, 2018.

  1. Rajil

    Rajil Member

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    So my samples froze in my car before I could drop them in the mail. Should it be okay or should I open and recollect? Surely they freeze in transit sometimes right?
     
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  2. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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    That is a tricky issue. Freezing will greatly increase the salinity in the unfrozen water and might induce precipitation of calcium carbonate, which will, in turn, take other things out of the water permanently. Other salts will also precipitate, but most of them will redissolve.
     
  3. Rajil

    Rajil Member

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    Thanks! I did end up getting an official response from ati. Per their email the freezing wouldn't have an impact.
     
  4. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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    Which doesn't make sense to me. Don't believe it without further justification.
     
    Last edited: Feb 6, 2018
  5. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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    Let's see if I can get them to come here to justify their response.
     
  6. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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  7. Rajil

    Rajil Member

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    Sounded fishy to me too. I honestly still sent it off, partly out of curiosity.
     
  8. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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    Perhaps this freezing can be OK due to the unusual form of calcium carbonate (ikaite) that forms at very low temps (see link below), which appears to redissolve at higher temps (unlike calcite or aragonite). Most of the major ion minerals certainyl will redissolve. My main question is the trace metals that may get into carbonate or oxides.

    That said, since so many folks samples are freezing, I think it would be interesting to see if trace metals that get incorporated into such precipitates will redissolve and give the same values before and after substantial freezing.

    https://www.the-cryosphere.net/8/1469/2014/tc-8-1469-2014.pdf
    "In our study, ikaite precipitated in sea ice at temperatures below – 4 ◦C"
     
  9. Cory

    Cory Valuable Member R2R Supporter Article Contributor

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    If your sample freezes, what elements would you pay no attention to?
     
  10. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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    My primary concern before I found out the form of calcium carbonate that forms is unstable and will redissolve was for elements that get incorporated as impurities in calcium carbonate but that start low to begin with, so a little uptake into crystals might take out a substantial portion of them. I've not really looked to see which are most prone to this issue, but trace metals in general.
     
  11. Cory

    Cory Valuable Member R2R Supporter Article Contributor

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    So a frozen sample wont effect the major elements, just trace metals, correct? Mine was shipped and it was -40 c back then. So id expect it would freeze.
     
  12. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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    Assuming ikaite is the calcium carbonate crystal that formed when it froze, I think it is unlikely to substantially impact the major elements since the primary major element precipitates (NaCl, CaSO4, etc.) will redissolve.
     
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  13. Cory

    Cory Valuable Member R2R Supporter Article Contributor

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    If you get your test redults back please post them here :)

    Im having an issue with mine that froze and id be curious if yours is strangely off too.
     
  14. Rajil

    Rajil Member

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    Will do. But I do have some issues in the tank currently so it's kind of bummer knowing this could mess with the results
     
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  15. Rajil

    Rajil Member

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    http://lab.atiaquaristik.com/share/540a92b8b0366107af30

    Got it back this morning. The phosphate, and slightly off salinity have been corrected since the sample was sent off. I've had some issues for months keeping certain corals alive. Some of the results are surprising, the tin, copper and aluminum. When we first started having issue we ran poly filter for weeks with no color change.
     
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  16. Christoph

    Christoph Active Member R2R Supporter R2R Excellence Award

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    IMHO to deliver meaningful analysis data the ICP providers need to acidify the samples prior to measurement. Even if precipitation of CaCO3 would occur in partly frozen water everything should redissolve nicely once acidified.

    Best,
    Christoph
     
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  17. Cory

    Cory Valuable Member R2R Supporter Article Contributor

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    Could we do this ourselves before sending it off?
     
  18. Christoph

    Christoph Active Member R2R Supporter R2R Excellence Award

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    No, since you would require suprapure acid (otherwise you would risk introducing contaminants that give you false-positives on some elements) and the acid type and concentration needs to be the same for all standards and samples to get reliable results.

    br,
    C
     
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