Review of the sampling and pretreatment methods for dioxins determination in solids, liquids and gases

The analytical requirements for the determination of dioxins (e.g. PCDD, PCDF) are unique in comparison with those for other routinely monitored chemicals: dioxins are measured in parts per trillion (ppt) and lower levels in technical and environmental samples, whereas other organics are measured in parts per million (ppm) or parts per billion (ppb). The ultra-trace analysis of dioxins requires a high sample enrichment obtainable by the use of efficient extraction methods and highly selective purification/fractionation techniques. Furthermore, highly sensitive equipment (e.g. high resolution gas chromatography - HRGC) with detection levels in the ppt range must be used to isolate and separate a huge number of dioxin congeners. The quantification of the dioxins by a high resolution mass detector (FIRMS) requires the use of internal and labeled standards. This paper reviews and compares the classic and modern pretreatment methods, namely extraction and clean-up, that are currently used in dioxin analysis in industrial samples and that were improved or developed in the last 25 years. In addition, the standard methods for dioxin sampling from in emission source (flue or stack gas) are examined and compared with new, automated techniques.