[shona788]

There's a partition coefficient experiment, in the aqueous phase we have complexed copper with ammonia; [Cu(NH3)4]2+
I know that practically all the copper is converted into the complex ion but i still need to test for the virtual absence of free copper ions in the aqueous layer. Any idea about this one?

[rabolisk]

Flame test? I think there may also be commercial copper ion test kits that rely on some sort of chemical reaction. A lot of these tests seem to rely on reacting copper with ammonia, so those certainly would not work, but maybe others would.