title: Effects of increasing polymer hydrophobicity on distribution ratios of TcO4- in polyethylene/poly(propylene glycol)-based aqueous biphasic systems.
abstract: The partitioning behavior of the pertechnetate anion was studied in aqueous biphasic systems (ABS) formed from (NH4)2SO4 and four types of polymers-poly)ethylene glycol) PEG, poly(propylene glycol) (PPG), Pluronic (a PEG/PPG block copolymer), and polyvinylpyrrolidone (PVP). Phase diagrams are reported for five (NH4)2SO4-polymer ABS systems including the polymers PEG-2000, PEG-3400, PEG-12,000, Pluronic-L64 (average molecular mass approximately 2900), and PVP-K15 (average M(r) approximately 10,000). Distribution ratios for the TcO4- anion in each of these ABS were investigated as a function of increasing salt concentration. In addition, the water-insoluble polymer PPG-2000 was studied. Pertechnetate partitions nearly quantitatively to the polymer-rich phase in each ABS, however, distribution ratios of near one were found for the PPG system. The relative ordering of the distribution ratios is PPG << PVP << PEG-2000 < PEG-3400 approximately PEG-12,000 < Pluronic-L64 for the three PEG-ABS systems, distribution ratios of the sulfate anion decrease in the order PEG-2000 > PEG-3400 > PEG-12,000, exhibiting the expected increase in phase incompatibility with increasing polymer M(r). Investigation of pertechnetate partitioning in two additional ABS based on K3PO4 and NaOH with Pluronic-L64 revealed trends similar to those reported for PEG-2000; the distribution ratio (D) values increase in the order NaOH < (NH4)2SO4 < K3PO4. Despite the higher distribution ratios from Pluronic-L64 at lower concentrations than found for PEG, the limited useable range of salt concentrations available may limit the practical utilization of this polymer in ABS separations.
authors.affiliation: Department of Chemistry, Northern Illinois University, DeKalb, 60115, USA.
authors.forename: R D
authors.initials: RD
authors.lastname: Rogers
authors.forename: J
authors.initials: J
authors.lastname: Zhang
mesh_terms: D009391:Nephelometry and Turbidimetry; D009994:Osmolar Concentration; D011092:Polyethylene Glycols / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D011205:Povidone / Q000737:chemistry; D011409:Propylene Glycols / Q000737:chemistry*; D012492:Salts / Q000737:chemistry; D013670:Sodium Pertechnetate Tc 99m / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry*; D013431:Sulfates / Q000737:chemistry; D013499:Surface Properties; D017186:Titrimetry
chemical_list: D011108:Polymers; D011409:Propylene Glycols; D012492:Salts; D012997:Solvents; D013431:Sulfates; C012504:polypropylene glycol; D011092:Polyethylene Glycols; D013670:Sodium Pertechnetate Tc 99m; D011205:Povidone