title: 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.
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.
authors.affiliation: Departamento de Química and Departamento de Tecnologia de Alimentos, Centro de Ciências Exatas e Tecnológicas, Universidade Federal de Viçosa, Av. P. H. Rolfs, Viçosa, MG 36560-000, Brazil. luhen@ufv.br
authors.forename: Luis Henrique M da
authors.initials: LH
authors.lastname: Silva
authors.forename: Maria C Hespanhol da
authors.initials: MC
authors.lastname: Silva
authors.forename: Roney A N de
authors.initials: RA
authors.lastname: Aquino
authors.forename: Kelly R
authors.initials: KR
authors.lastname: Francisco
authors.forename: Marcus V C
authors.initials: MV
authors.lastname: Cardoso
authors.forename: Luis A
authors.initials: LA
authors.lastname: Minim
authors.forename: Jane S R
authors.initials: JS
authors.lastname: Coimbra
mesh_terms: D000838:Anions; D005295:Ferrocyanides / Q000737:chemistry*; D009599:Nitroprusside / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry*; D012996:Solutions / Q000737:chemistry; D013431:Sulfates / Q000737:chemistry*; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
chemical_list: D000838:Anions; D005295:Ferrocyanides; D012996:Solutions; D013431:Sulfates; D014867:Water; C012036:sodium sulfate; D009599:Nitroprusside; D011092:Polyethylene Glycols