New Technologies for Metal Ion Separations: Aqueous Biphasic Extraction Chromatography (ABEC). Part I Uptake of Pertechnetate

Polyethylene glycol (PEG) based-aqueous biphasic systems (ABS) have been adapted to a solid aqueous biphasic extraction chromatographic (ABEC) mode by grafting high molecular weight PEGs to a solid support and using high ionic strength salt solutions as mobile phases. The new resins behave as an ABS: in the presence of high ionic strength solutions of water-structuring anions (e.g., SO4 2-, CO32-, OH-, etc.), chaotropic ions (e.g., Tc043-) are retained. Stripping is accomplished by washing the resins with water, thus lowering the ionic strength and no longer mimicking an ABS environment. Monomethylated PEGs (Me-PEGs) of average molecular weight 350, 750, 2000, and 5000 have been grafted to chloromethylated polystyrene-1%-divinylbenzene. Quantitative uptake of tracer-scale pertechnetate has been achieved from NaOH, (NH4)SO4 K2CO3, and K3PO4 for the two higher molecular weight PEG resins, with retention increasing as the molecular weight of the grafted Me-PEG increases. No uptake is observed from water.