Determination of chlorobiphenyls in seal blubber, marine sediment, and fish: interlaboratory study

Between 1988 and 1994, the International Council for the Exploration of the Sea, the Intergovernmental Oceanographic Commission, and the Oslo and Paris Commissions organized a stepwise interlaboratory study for determination of chlorobiphenyls (CBs) in marine media. The final parts of this study, in which 53 laboratories from 14 countries participated, focused on long-term precision, cleanup, and extraction. Calibration was controlled continuously by analysis of 10 CBs in an unknown solution. Participants were requested to analyze 3 CBs in a certified reference material fish oil (6 times); 10 CBs in cleaned and uncleaned marine sediment and seal blubber extracts; and 10 CBs in seal blubber oil, dried marine sediment, and wet, lean fish muscle tissue. The long-term precision study showed that, compared with earlier exercises in which only duplicate analyses were required, repeatability increased about 1.5-fold compared with reproducibility. The mean standard error for reproducibility of determination of 10 CBs in standard solutions improved from 1.22 to 1.15. The standard error improved from 1.36 to 1.25 (without CBs 28 and 31) for seal blubber oil and from 1.36 to 1.22 for dried marine sediment. In seal blubber oil and dried marine sediment, the major CBs 118, 138, 153, and 180 can now be determined by the group of participating laboratories with a reproducibility of 1.5 (about 50%). No significant differences were found between results for cleaned-up and uncleaned extracts. No acceptable results could be obtained for determination of CBs in lean fish muscle tissue. Biplots of principal component analyses are extremely helpful in evaluating the data generated by this type of study.