Supercritical fluid extraction of polychlorinated dibenzo‐p‐dioxins from municipal incinerator fly ash

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Abstract
The supercritical fluid extraction of polychlorinated dibenzo‐p‐dioxins from an incinerator fly ash sample has been investigated; supercritical nitrous oxide and its mixtures with methanol and toluene were employed as mobile phases.Recoveries of individual polychlorinated dibenzo‐p‐dioxins congeners were calculated from results of analysis of 13C‐labeled dioxins by high resolution GC‐MS employing selected ion monitoring. The extraction procedure was compared with extraction in a Soxhlet apparatus, which is currently used as a standard method for removing chlorinated dibenzo‐p‐dioxins from fly ash samples: the results indicated that the time required for the extraction and clean‐up can be reduced from 24 to 2.5 hours/sample. Quantitative recovery of the chlorinated dibenzo‐p‐dioxins was achieved at μg/kg levels, the relative standard deviation was between 1.8 and 5.8%.The use of a virtually inert fluid such as pure nitrous oxide provides significant improvement over conventional extraction procedures because no solvent residue is left in the processed extract.