Just one last suggestion:
Every compound has some maximum amount of solubility, so trying to use very small liquid volumes could get frustrating. I've always found it easier to use a larger volume. A small error in measurement makes less of a difference this way also, although very precise dosing is not required with EI.
The inventor of this system intentionally designed it to be extremely forgiving in this regard. (I assume this was intentional.)
In any case, don't get caught up trying to measure 1/132nd tsp of something.
While not the inventor really, more the cheerleader.........the intent was a reaction to PMDD which users techy terms, mls, chem calculations, ppm's or this or that chemical salt, dosing daily and weighing X amount of this and that.
Testing and doing water changes if things got too far away from you, minimization of PO4, I think many found it a bit too much and it did not become as popular as what it could have been.
I just suggested simplifying it because I knew there were no risk and that the ranges where MUCH larger than those claimed(still today many insist the ranges are far narrower than they really are, and suggest there's risk, but this has been falsified multiple times in many different tanks by many different people)
So it was more a response to human issues than plant issues really, what makes it easiest for folks without incurring any more risk. PMDD came before EI and EI is 95-99% PMDD without the fear of algae added/removal of test kits.
Still have not met anyone who got into the fish hobby for their love of testing water samples. Have any of you?