Hobby ICP study - Evaluating the Repeatability and Differences between ICP Tests

[Thales]

Thanks @Thales for sharing this study! The mathematical rigor really helps with perspective.

Did you send out sterilized salt water samples?

We did not. The point of this study was not to make ICP testing better, it was to help understand results of the hobbyist experience.

I wonder if there is a difference between samples that have been sitting in the collection vial for different amounts of time - I usually overnight my tests to ICP-analysis and they test them same day, so that’s 24 hours of “sit” time, vs other samples could feasibly sit in the vial for 2 weeks before testing. I guess it’s hard to predict when a company will measure your sample, but maybe one variable could be removed by either sterilizing the sample or letting the samples sit longer before shipping to the higher turn-around companies?

I’m curious how much phosphate and trace could get fixed by biofilms that form on the sides of the vial or taken up by bacteria/plankton that may then get filtered out before they run the test? (I am assuming there is some mechanical sample filtration prior to ICP testing - or is everything including small particulate matter getting vaporized and counted in the ICP?) I suppose then some of the differences could be explained by different pre-filtering or handling process.

This is an area of concern for sure. Asking hobbyists to fix a sample comes with problems and expense, so I doubt we are going to see much motion in this area.

 

[L/B Block]

@Thales -def great article. Really nice add with the CV. Unfortunately being jaded -not surprised at the least!

However because this is a private forum I will name names (ATI) -on the last ICP test I took the sample at the same time as I did my PO4 test- ICP came in at .3, Hanna -.31
CA ICP 409, Trident 406. Caveat -trident had tested 7 hrs prev and first AFR dose already in the system.

Still..hmm. I realize it is anecdotal.
I have 7 tests (maybe 6) and may compare results on the nitrate, phosphate, CA, & ALK and compare accordingly.

 

[PjFish]

Awe shit. First ones free. The next one will cost ya. Then you just became his customer. Unfortunately I can’t store 600 gallons. Sad guy.

Anyone ever sent Bob’s SW to ICP?

 

[Thales]

Anyone ever sent Bob’s SW to ICP?

I did once, but I can't seem to find it.