What I'm thinking to do with the probe is something like this:
Take some clear, settled IO salt water at normal salinity. Determine the calcium by ICP/AA using standard additions of calcium ions (acidified and filtered and also not acidified and filtered, to show that it is all in solution).
Then determine the calcium in that non acidified IO with the probe.
Determine the calcium in IO that has standard additions of calcium.
Same for standard additions of magnesium.
Determine the calcium concentration as the IO is diluted slightly with DI water.
These tests should show whether the probe is basically accurate, and how it is impacted by magnesisum and salinity.
If anyone has other suggestions, I'm happy to consider them.
