You'd pay a lab about $45, same as I did for my quality control check. A few of the ions--like nitrate or ammonium--will probably get tested with some kind of c

You'd pay a lab about $45, same as I did for my quality control check. A few of the ions--like nitrate or ammonium--will probably get tested with some kind of color-change reaction, and quantified with a visible-light spectrophotometer. The rest will be from ICP (inductively coupled plasma), a precisely-quantified version of the same effect as where different elements make a flame turn different colors.