Membrane characterization of anion-selective CHEMFETs by impedance spectroscopy

Impedance spectroscopy can be used to determine the influence of several me mbrane parameters on the membrane resistance of anion selective CHEMFETS. T he concentration of the ammonium sites in the membrane, the anion-receptor complex stoichiometry, and the polarity of the membrane matrix are of parti cular importance. In general the resistance of polysiloxane membranes is hi gher than that of PVC membranes. However, in polysiloxane membranes the mem brane polarity can be influenced by the type or concentration of polar subs tituents on the polysiloxane chain. Polysiloxane ion-exchange membranes wit h 25 mol % of polar sulfone substituents exhibit the same conductance as NP OE plasticized PVC membranes. Remarkably, the membrane resistance of cation -selective polysiloxane membranes is much lower and is much less dependent on the substituents.