Analytical procedures to detect 2,3,7,8-TCDD at Seveso after the industrial accident of July 10, 1976

The analytical procedures used at Seveso (Milan, Italy) for the determination of 2,3,7,8-TCDD, and some isomers, in biological and environmental samples are reviewed in this paper. During the emergency period, up until the first 10 days of August, the extracts, mostly from soil or vegetation samples, were evaporated to dryness and then mixed with ⩽ 10-ml solvent. Of these solutions, aliquots up to 10 μl were injected into a low-resolution gas chromatograph (GC) combined with a low-resolution mass spectrometer (MS). Analytical sensitivity for vegetation and soil was < 10 ppb and ∼ 100 ppt, respectively—sufficient for the early mapping of the most heavily contaminated territory. After the emergency period, the greatest improvement in environmental sample analysis was the introduction of cleanup procedure which greatly reduced the presence of unwanted material in samples. Cleanup was followed by the complete removal of the solvent. Dry samples could be taken up with rather small volumes (⩾0.1 ml) of solvent, of which an aliquot was used for GC-MS analysis. The instrumental setup was kept as above. For animal samples, extraction entailed preliminary alkaline digestion followed by a number of cleanup steps. The final dry sample was taken to desired volume by adding solvent (⩾0.1 ml), of which a few microliters were injected in GC-MS apparatuses. Detection thresholds improved markedly and were < 10 ppt for agricultural soil and sediment, ⩽0.05 ppt for water, in the range of 60 to 200 ppt for air dust, < 10 ng/m2 and 10 ppt for wipe and scrape tests, respectively, < 50 ppt for vegetation, and 250 ppt for biological substrata. Major later improvements in TCDD assay were the use of high-resolution gas chromatography (hrGC-MS), in some cases combined with high-resolution mass spectrometry (hrGC-hrMS). This provided greater specificity, sometimes accompanied by a very marked increase in detection sensitivity.