NH2 is actually a amidogen,...its a amino group in organic chem/ and a amino ion in inorganic chem. its a compound radical and is not present in a seperate state. it readily reacts with H+(NH2 + H -> NH +H2) or OH-(NH2 + OH -> NH +H2O) ph depending. basically its ammonia that losses a H+ in water resulting in H3O+ and NH2, which then reacts with H+ or OH- (which ever has the greater concentration). it also reacts with other things but thats the basics.
so to answer your question, no, you dont need to test for it
