I'm working with a lead (II) ionophore to prepare potentiometric ion selective electrodes. Can anyone suggest something to add to the ionophore, besides PVC and a conducting salt, in order to improve sensitivity and selectivity?
Optimization of the amount of lipophilic site additive in the membrane can significantly improve ISEs selectivity.
Selectivity of your sensor refer to properties of ionophore, size of cavity but you can improved with change in plastisizer and additive and amounts of them.
The selectivity of ion-selective electrodes depends on the ratio of exchange current densities of the analyte ion to those of the interfering ions. In order to increase the analyte’s exchange current density PVC/plasticizer/ion carrier membranes are normally “conditioned by soaking them in about 0.01 M solution of the analyte. By this, membrane sites are “saturated” with the analyte ion and the corresponding exchange current density at the phase boundary membrane/sample solution is increased compared to the one of potentially interfering ions. The selectivity and stability will be improved by this, but the detection limit may be worse. Adding a small amount of an lipophilic anion together with a cation which is not bound to the lead ionophore may help to prevent electro neutrality during this conditioning process (see also: potassium membranes with valinomycin in which Na-phenyl borate has been added).
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