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 less than or equal to 10-ml solvent. Of these solutions, aliquots up to 10 microliter were injected into a low-resolution gas chromatograph (GC) combined with a low-resolution mass spectrometer (MS). Analytical sensitivity for vegetation and soil was less than 10 ppb and approximately 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 (greater than or equal to 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 (greater than or equal to 0.1 ml), of which a few microliters were injected in GC-MS apparatuses. Detection thresholds improved markedly and were less than 10 ppt for agricultural soil and sediment, less than or equal to 0.05 ppt for water, in the range of 60 to 200 ppt for air dust, less than 10 ng/m2 and 10 ppt for wipe and scrape tests, respectively, less than 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.