查看文章

Ions are known to concentrate in the salt-enriched phase of aqueous two-phase systems, with the only known exception being the pertechnetate anion, TcO₄^-. We have discovered a second ion, nitroprusside anion (NP), which is markedly transferred from the salt phase to the polymer phase. The partitioning behavior of [Fe(CN)₅NO]^2- anion was investigated in ATPS formed by poly(ethylene oxide) of molar mass 3350 and 35000 g mol^-1, and different sulfate salts (Na₂SO₄, Li₂SO₄, and MgSO₄). On the basis of a model, the nitroprusside high affinity for the macromolecular phase was attributed to an enthalpic specific interaction between the anion and ethylene oxide unit. Partition coefficients increased exponentially with tie-line length increase, reaching values as high as 1000 and showing a relationship very dependent on the salt nature, but independent of the polymer molar mass.