Comparison between supercritical fluid extraction (SFE) using carbon dioxide/acetone and conventional soxhlet extraction with toluene for the subsequent determination of PCDD/PCDF in a single electrofilter ash sample

A single electrofilter ash sample from a municipal waste incinerator was analyzed for PCDD/PCDF. Different pretreatment procedures (chemical: sulfuric acid/no acid; mechanical: ground/not ground) were performed with two independent but identical samples each were subsequently Soxhlet extracted with toluene or subjected to SFE. It was shown, that an acid treatment subsequently combined with SFE gives the most favourable extraction efficiency. Consequently a severe underestimation of PCDD/PCDF concentrations can result from SFE extraction without preliminary acid treatment of the ash.