SWITCHING OF ION SELECTIVITY OF MEMBRANES BY LIPOPHILIC IONIC SITES

Potentiometric anion and cation selectivities of PVC membranes based o n a thioamide calix[4]arene derivative are described. The influence of the internal electrolyte and membrane composition on ion selectivitie s were determined. Membranes without added lipophilic salts showed hig h selectivity for perchlorates over other anions with linear responses in the range of pClO(4)(-) 1-5 with a slope of 58.6 mV x 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 p roper choice of lipophilic salts, plasticizer for membrane preparation and the membrane conditioning can alter and moderate the ion selectiv ity.