V. Horvath et al., ION-EXCHANGE AT NEUTRAL CARRIER ION-SELECTIVE ELECTRODE MEMBRANES, Fresenius' journal of analytical chemistry, 346(6-9), 1993, pp. 569-571
Radiotracer experiments proved that neutral carrier (valinomycin) cont
aining plasticized PVC membranes behave as cation exchangers. The exch
ange capacity may be due to lipophilic salt additives, but there is al
so a native exchange capacity that may be due to hydrophilic salt cont
aminations trapped in the membrane.