Neutral Carriers for Anions

Liquid membranes based on classical anion exchangers normally exhibit roughly the same selectivity sequence with a preference for lipophilic and a rejection of hydrophilic anions [6]. The same holds for the response to cations of electrodes based on classical liquid cation exchangers, e.g., tetraphenylborates [12]. This is in contrast to neutral carrier membrane systems for cations where the ion selectivity is highly dependent on the free energy of the interaction of the ions with the ligand [1, 8]. If neutral carriers for anions are incorporated into solvent polymeric membranes, a wide variety of ion selectivities is expected to be made accessible [13].