The liquid extraction and spectrophotometric quantitation of uranium from different solid matrices is compared to supercritical fluid extraction (SFE) using various combinations of 2,2-dimethyl-6,6,7,7,8,8,8-heptafluoro-3,5-octadione (FOD), tri-n-butylphosphate (TBP), ethanol, and carbon dioxide measuring the UV absorption of the uranium-FOD complex. The matrix is shown to have a tremendous effect on the extractability of uranium from different solid matrices. Compared to liquid extraction, the SFE method yields higher recoveries, is significantly faster, is of equal or greater precision, and greatly reduces the amount of organic solvents used. In the second part of this work, the speciation of hydrophobic organic compounds (HOCs) in ancient sediments is studied by stepwise high temperature SFE and comparisons made to thermodesorption and soxhlet extraction. High temperature SFE recovers significantly more HOCs compared to soxhlet extraction. For low molecular weigh compound thermodesorption is the dominant mechanism whereas for high molecular weight compounds the mechanism is a combined effect of thermodesorption and solubility in the supercritical fluid.
