Selective Supercritical Fluid Extraction of Uranium(VI) using N-Phenyl-(1,2-Methano-Fullerene C60)61-Formohydroxamic acid and Simultaneous On-line Determination by Inductively-Coupled Plasma-Mass Spectrometry (ICP-MS)

Uranium(VI) is extracted with N-phenyl-(1,2-methano-fullerene C₆₀)61-formohydroxamic acid, PMFFHA, in dichloromethane by supercritical carbon dioxide (SF-CO₂)-dichloromethane (modifier) medium. A 2.0 µL aqueous uranium is extracted accurately and also preconcentrated in an especially designed extraction vessel of 80 µL capacity. The extracted microdrop orange-red colored uranium(VI)-PMFFHA complex in dichloromethane was online measured by fiber optics spectrometry and ICP-MS. The distribution ratio (D_UO2²⁺) of U(VI) was determined. The slopes of log D_UO2²⁺ versus PMFFHA concentration plot, the extracted species both in SF-CO₂ extraction (SFE) and the solvent extraction (SE) were determined to be 2.0 as UO₂(PMFFHA)₂ complex. The uranium is determined as low as 0.10 ng mL^-1 in presence of several cations and anions. The effect of diluents, modifier concentration, temperature and pressure on the extraction and separation of uranium was studied. The uranium is determined in human blood serum, natural water, seawater, standard samples and also in monazite sand. The PMFFHA has been successfully used as carrier for the selective and efficient transport of uranium(VI). The feed comprised of a solution of uranium(VI) and aqueous solution of diverse cations and anions in pH 4.5, while 1M HNO₃ was used as a stripping agent in the receiving compartment of permeated cell. Maximum transportation was observed for 12 minutes with t_1/2 equal to 6.3 min. The uranium(VI) was determined in presence of uranium(IV).