The power of the weak: recognition of ion pairs in water using a simple array sensor.

An array sensor comprising six off-the-shelf indicators doped in a poly(ether-urethane) recognizes five cations, seven anions and thirty-five ion pairs at pH 5-9 in water. Such a discrimination capacity and recognition efficiency (6 : 35) with > or = 93% accuracy is rare. Low cost and wide availability of various polymers and indicators could make this approach useful in numerous applications.