[CoolGuyNice]

So for my assignment we had to test which water sample would be the healthiest to drink using industry standards. The tests we used were the chloride ion analysis, pH and measured the conductivity. Upon receiving back my draft, my teacher said i had to find and research some challenging concepts about the tests and or the samples that would be used outside the classroom setting. Honestly, I've been on so many sites and its difficult trying to find anything about how the tests relate let alone challenging concepts. I've discussed how the interrelationships as best as i could but i have no idea what a 'challenging' concept may be.
Any help or a link to some good sources would be of great help and would be greatly appreciated.