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Facilitated transport of salts by neutral anion carriers

Wiley-VCH Verlag
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Partitioning of ions from water to the membrane solvent (NPOE) can be quantified by Gibbs free energies of transfer, Gtr,NPOE(ion). These were derived from transport studies of lipophilic salts through supported liquid membranes (SLMs) in the absence of the carrier. Partition coefficients Kp for various salts can now be calculated. The neutral anion receptors uranyl sal(oph)enes 1-5 transport Cl- and H2PO<![IGNORE[$_{4}{-}$]]> as tetrapropylammonium salts. The transport is diffusion-limited and can be described by two transport parameters Dm and Kex. From the extraction constants Kex and the partition coefficients Kp of the transported salts, the association constants Ka of the anion receptors for Cl- and H2PO<![IGNORE[$_{4}{-}$]]> in NPOE were determined. Competitive transport with carriers 3 and 4 of NPr4H2PO4 and NPr4Cl demonstrated highly selective transport of H2PO<![IGNORE[$_{4}{-}$]]> even in the presence of excess of Cl-.

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