Nitroprusside-PEO enthalpic interaction as a driving force for partitioning of the [Fe(CN)(5)NO](2-) anion in aqueous two-phase systems formed by poly(ethylene oxide) and sulfate salts |
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Authors: | Silva Luis Henrique M da Silva Maria C Hespanhol da Aquino Roney A N de Francisco Kelly R Cardoso Marcus V C Minim Luis A Coimbra Jane S R |
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Institution: | Departamento de Química and Departamento de Tecnologia de Alimentos, Centro de Ciências Exatas e Tecnológicas, Universidade Federal de Vi?osa, Av. P. H. Rolfs, Vi?osa, MG 36560-000, Brazil. luhen@ufv.br |
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Abstract: | Ions are known to concentrate in the salt-enriched phase of aqueous two-phase systems, with the only known exception being the pertechnetate anion, TcO(4)(-). 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)(5)NO](2-) anion was investigated in ATPS formed by poly(ethylene oxide) of molar mass 3350 and 35000 g mol(-1), and different sulfate salts (Na(2)SO(4), Li(2)SO(4), and MgSO(4)). 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. |
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