Salinity Discrepancy | Refractometer vs ATI ICP

Whasmack · Oct 3, 2019

So, I received my ATI ICP test results - and it says my salinity is super low?? 30.96PSU & it's supposed to be 35.0
I have 3 different refractometers that I've calibrated with BRS 1.026 solution and they all read my salinity at 1.026.
Has anyone else experienced this? Which one is correct?

User1 · Oct 3, 2019

I've used ATI and the first time it reported that my salinity was also low. Not to the degree what you report but it was low. I then bought a calibration solution, checked my digital tester, and low and behold ATI was correct and I was not.

I would send them an email. They reply pretty quick and just ask them about it and how you test at home and see what they say or suggest. In my case though their test was correct and spot on. I was low.

Whasmack · Oct 3, 2019

Ok - I'll see what they say. I will admit that I keep the solution in my tank rook; which is probably ~ 70 degrees. I think the solution says 25 C on it.

Whasmack · Oct 4, 2019

From ATI -
Unfortunately, your sample samples are no longer available, as we can only hold them for 7 days. However, I was able to look at the series of measurements from your sample water and could not detect any deviation or other errors. From the point of view of measurements, the salinity specified by us is correct. When looking at the analysis protocol is striking that there is a shift in the proportions in your aquarium. Meaning, Na and Cl are okay for salinity, but the other quantities are increased. In determining the salinity by us only Na and Cl are used, as they account for more than 85% in natural seawater. If it comes to a quantity shift, as you can see it, a measurement with a Refrakatormeter can show an increased, or a decreased Salinity. In your case now an increased.

Westside Guy · Oct 4, 2019

Use RO on the 3 refractometers instead of the BRS 1.026 solution and calibrate the PPT's reading to 0. Then see what the reading is with the tank's water.