Triton's Limit of Detection (LOD)

sonnus · Apr 26, 2016

So after going through several posts and articles I put together a quick reference list of Triton's LOD. The only seawater reference I could find was from Karl K Turekian and I did not convert the ppm to mg/L since the table said "ppm= parts per million = mg/litre = 0.001g/kg". Randy and others have stated many times that Triton's test results don't clearly relay the LOD and that it's important to consider when correcting water parameters. The "Maximum Dosage" is based off either NSW or Triton's setpoints depending on which is lower minus the LOD to prevent overdosing. The maximum doses for most of the major elements are irrelevant since your tank probably wouldn't survive with huge deficiencies but I included them for reference.

I would assume that Triton takes the LOD into consideration when suggesting dosages of their products but if you want to use DIY or off the shelf supplements then hopefully this will make dosing trace elements easier for some.

JimWelsh · Apr 26, 2016

Nice table! I do want to make a few comments, though.

The statement on the table that "ppm= parts per million = mg/litre = 0.001g/kg" is nonsense. These numbers are in w/w, and would need conversion to w/v at "3.5% salinity", as the table states. At 20C, the conversion factor would be the density of NSW at S=35 and T=20C, which is 1.024763.

A good source for this kind of information that has been updated with much more current data than was available in 1968 can be found here. The data I used when I built my own similar table in Excel was from Pilson's text. There are a few significant differences between the numbers you cite from Turekian and the numbers that both Pilson and the MBARI Periodic Table show. Specifically, your numbers show NSW levels for Nickel, Zinc, Manganese, and Iron are all at least an order of magnitude higher than the Pilson and/or MBARI numbers.

I also note that your LOD number for Vanadium has a typo. The lower limit is 0.92, not 0.592.

The important "take away" message, IMHO, is to understand for which elements the Triton LOD is higher than the NSW level, and by how much that LOD is greater than the NSW level. That list includes, in ascending order of ratio of Triton setpoint to NSW level: Nickel, Chromium, Cadmium (all < 10 times), Manganese, Copper, Iron, Antimony, Selenium (all between 10 and 100 times), Titanium, Cobalt, Beryllium (all between 100 and 1000 times), and Lead, Mercury, and Tin (all > 1000 times).

Randy Holmes-Farley · Apr 26, 2016

I would just add that ocean surface level of iron is far, far lower. Way below Triton's limit of detection. Many of these vary with depth (most often for bioactive metals, being depleted at the surface) and we should really focus on surface levels since that is where our organisms live naturally.