Switching of ion selectivity of membranes by lipophilic ionic sites

Potentiometric anion and cation selectivities of PVC membranes based on a thioamide calix[4]arene derivative are described. The influence of the internal electrolyte and membrane composition on ion selectivities were determined. Membranes without added lipophilic salts showed high selectivity for perchlorates over other anions with linear responses in the range of pClO4− 1–5 with a slope of 58.6 mV × decade−1. Addition of potassium tetrakis[3,5-bis(trifluoromethyl)-phenyl]borate (KTFPB) gave good selectivities of membranes towards lead(II) cations with a near-Nernstian slope of the Pb(II) response. We showed that a proper choice of lipophilic salts, plasticizer for membrane preparation and the membrane conditioning can alter and moderate the ion selectivity.