There was a gentleman on another forum that decided to get involved in the DEF market and was very knowledgeable. He was always online answering questions. I initially bought a couple of his 2.5 gallon DEF containers, but just haven't had the opportunity or need to store that much DEF while on the road. He later came out with the magnetic collar. Being a gadget guy, I figured I might just need one at some point.
Magnetic CollarI asked him if a test strip could be produced, like the coolant strips, so that questionable DEF purchased off the shelf could be quickly tested. (I got a box of DEF from Walmart that had been used and refilled with water). He said that a strip really couldn't be used, but if the DEF is questionable, drop a small amount on the ground or piece of cardboard. It should turn to crystal like you see at the pumps.