Some comments:
1.
Wouldn't it be funny if the differences that Ron saw had nothing to do with metals, but rather one of the many other possibilities, such as ammonia, nitrite, organics, etc. etc? Well, actually it wouldn't be funny. Unfortunately, this protocol won't get at the biological differences. I don't think simple testing of more salt mixes will either. Perhaps that is something that can be pursued in other ways in other studies.
2.
I would advise again to test NSW in addition to the RO/DI water. Without both, you will never know whether any elevated metals that you see came from the salt mixes themselves, or from some artifact of the methodology, such as the sampling implements, the mixing containers, the sample bottles, or some artifact in the ICP-MS testing itself. Scientists were mislead for many years by impurities arising from their handling of NSW samples. I think it is a mistake to think that a bunch of folks who have never done anything like this before won't suffer the same problems (whatever they may be). Even if the folks involved were to read in detail how these studies need to be done, whether or not their first tries at something difficult will succeed is an open question. I don't know what is involved, but when I read words like "Ultraclean room techniques" in "Chemical Oceanography" that does not sound like something that aquarists can whip up in a back room somewhere. This is why I did not respond to Bill's question about how to collect samples: I don't know.
Sending the RO/DI water will help a lot, but not necessarily solve this problem, especially since we are not sure exactly where the problems will come from.
Comments more specifically on the protocol:
3.
Mix each with RO/DI water to a s.g. of 1.025.
Why pick a vlaue below nsw salinity? I'd use a calibrated conductivity probe, and aim for 53 mS/cm (35 ppt salinity). Alternatively, a
refractometer will do, but again pick NSW salinity.
Without knowing that otherwise is OK, I'd mix the solutions in teflon containers and send them in teflon bottles, since teflon bottles have specifically been mentioned as suitable. If someone finds that something else is suitable, then that will be fine, but I don't know at this point. Teflon is quite expensive, and will icnrease costs for the study.
I would not let the samples contact anything made of glass or metal.
4.
Make the initial mix a little high in s.g. so that we can adjust to 1.025 by adding water, not salt. This should improve consistancy somewhat.
I'm not sure why you'd want to do that. If you are tallking about mixing to 36 ppt and then diluting to 35 ppt, that would be OK, but if you are talking about 40 ppt or more, taht risks precipitation of things that might otherwise stay in solution.
5.
Stir until thouroughly dissolved and measure initial pH.
Continue to peroidically stir and let sit to allow any precipitates to settle.
Any aeration at this step? Some salt mixes initially mix to very high pH. Without aeration, the high pH may accelerate the precipitation of things, and result in artificial differences between brands just based ont eh initial pH.
6.
It is easy to get tables of NSW elements. We posted them in Ron's magazine author forum during one of the discussions about Ron's initial test results on aquaria:
http://reefcentral.com/forums/showthrea ... adid=61689