The properties of poly(oxyethylene) dicarboxylic (POEDC) and diphosphoric (POEDP) acids as macromolecular carriers (macroionophores) of metal cations have been investigated and compared to the properties of poly(ethylene glycol)s. The macroionophores were dissolved in 1,2-dichloroethane forming a flowing liquid membrane (FLM) in a multimembrane hybrid system. The system was composed of the FLM circulated between two cation-exchange membranes (CEM) which were applied as the interfacial separators between the organic (FLM) and aqueous feed (Zn(2+), Cu(2+), Ca(2+), Mg(2+), K(+), Na(+) nitrates) and stripping (H(2)SO(4)) solutions. Additionally, the FLM was dried continuously by pervaporation of water from its organic phase. The fluxes, selectivity, and separation characteristics have been determined under competitive transport regime. It was found that the pertraction properties of POE derivatives depend on cooperation between ionic end-groups and pseudocyclic structures of the polymer chain. For example, the following typical separation orders have been found for PEG-6000 based macroionophores: PEG-6000: K(+) > Zn(2+), Ca(2+), Na(+) > Cu(2+), Mg(2+) POEDC-6000 : K(+) > Zn(2+) > Na(+), Ca(2+), Cu(2+) > Mg(2+) POEDP-6000 : Zn(2+) > Cu(2+) > K(+) > Ca(2+), Mg(2+) > Na(+) (C) 2010 Elsevier Ltd. All rights reserved.