Results of an interlaboratory study on organochlorine compounds (PCB, DDT, DDE) in seal blubber (Phoca vitulina)

In an interlaboratory study, initiated by the German Study Group on Seal Pathology, an extract of genuine (unspiked) seal blubber (Phoca vitulina) was analysed by 14 laboratories (15 participants) for six PCB congeners (Nos. 28, 52, 101, 138, 153, 180), 4,4′-DDT, and 4,4′-DDE. The choice of the analytical method (clean-up, GC) was left to the laboratories. From the data which were subjected to a statistical analysis, an interlaboratory comparison (R-values) was assessed. On the basis of the R-values (except PCB Nos. 28 and 52) which range from 1.29 to 1.89 for the analysed compounds, the overall comparability of the participating laboratories can be considered as satisfactory. From these results the conclusion has to be drawn that any comparison of residue data, produced by different laboratories, can only be justified under the assumption that the corresponding ranges of variation are observed and that data of the same distinct congeners are compared.