Is it necessary to use the conducting polymer in between sensing membrane and electronic conductor (I am using graphite surface) if the proposed ion selective electrode shows high potential stability (no water layer formation)? Does the conducting polymer play the role in sensing mechanisms or is it only used to increase the potential stability of ISEs?
No, in fact you can use any conductor such as aluminium if you deposit the ISE membrane onto it form a solution.
At any interface of two different materials there will be a potential difference. This has to be stable and is included in the total EMF of the electrochemical cell used. But even the most sensitive high impedance voltmeter draws about 10 to minus 14 amps through the cell. This unavoidable current should not change the potential difference under discussion (polarize). Thus, there has to be an interfacial charge transfer with an exchange current density much greater and. Often, redox-reactions are established at those interfaces.
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