Kind of ion-selective membranes used in an ISE comprising:

1. Positively-charged, hydrophobic cations which, when dissolved in a suitable organic solvent and held in an inert support (e.g., poly(propylenecarbonate) filter or \(\ce{PVC}\)), provide membranes which are sensitive to changes in the activities of anions.
2. Negatively-charged hydrophobic anions which, when dissolved in a suitable organic solvent and held in an inert support (e.g., poly(propylene carbonate) filter or \(\ce{PVC}\)), provide membranes which are sensitive to changes of cation activities.
3. Uncharged “carrier” electrodes based on solutions of molecular complexing agents of cations and anions, which can be used for preparing ion exchanger membranes sensitive and selective to certain cations and anions.
4. Hydrophobic ion-pair electrodes of plasticized polymers (e.g., \(\ce{PVC}\)) containing a dissolved hydrophobic ion-pair respond to the ion activities of those components, which are relevant to the ion-pairs incorporated in the membrane. The responses can be Nernstian.

Examples:

1. Quaternary ammonium cations or cations of substitutionally inert, transition metal complexes of such ligands as derivatives of 1,10-phenanthroline.
2. Of type \(\ce{(RO)2PO2-}\), tetra-p-chlorophenylborate, dinonylnaphthalene sulfonate
3. Ion-dipole forming agents: antibiotics, macrocyclic compounds or other sequestering agents. Adduct forming agents, such as organotin compounds, activated carbonyl compounds, and some porphyrins.
4. Cationic drug substance as cation tetraphenylborate, or an anionic drug substance as tetraalkylammonium salt of the anion.