Determination of solubilities of uranium complexes in supercritical CO2 byon-line laser-induced fluorescence

A new approach to the measurement of solubilities in supercritical CO2 is r eported, utilizing laser-induced fluorescence, This selective technique was found to be capable of rapid multipoint solubility measurements with high sensitivity (10(-9) M). The sensitivity enables measurements to be performe d with small amounts of analytes and at low pressure, 80-130 atm, typically below the range of other methods. Four uranyl complexes were investigated using this method, UO2(TTA)(2). H2O, UO2-(TTA)(2). TBP, UO2(TTA)(2). TOPO, and UO2(NO3)(2). 2TBP (where TTA = thenoyltrifluoroacetone, TBP = tributyl phosphate, and TOPO = trioctyl phosphine oxide). Comparison with solubility data previously obtained with UV-visible spectroscopy shows good agreement between the techniques. We have shown that the Chrastil solubility equatio n is equally valid at lower ScF densities, and consequently, solubility val ues determined at high pressures can be extrapolated to the low-pressure re gions and vice versa for solid materials.