Frozen ati icp test samples
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Randy Holmes-Farley
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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.
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Which doesn't make sense to me. Don't believe it without further justification.
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Randy Holmes-Farley
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Let's see if I can get them to come here to justify their response.
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Started a thread with them here:
https://www.reef2reef.com/threads/concern-about-frozen-samples.357285/
https://www.reef2reef.com/threads/concern-about-frozen-samples.357285/
Randy Holmes-Farley
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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"
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"
Randy Holmes-Farley
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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.
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.
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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.
Will do. But I do have some issues in the tank currently so it's kind of bummer knowing this could mess with the resultsIf 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.
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.
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
Best,
Christoph
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,
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