Reports on the ICES/IOC intercomparison exercise on hydrocarbons in biological tissues (2/HC/BTJ and the ICES intercomparative study (3/HC/BTJ on PAH in biological tissues

A homogenate was prepared from approximately 4,000 Mytilus edulis sampled near the municipal sewer outfall of Boston, Massachusetts, U.S.A. Subsamples were placed in jars. Then a set of subsamples were freeze-dried. Both wet homogenate and freeze-fried homogenate samples were checked for non-homogeneity by analyses of randomly selected subsamples by the W.H.0.I. coordinating laboratory. Three randomly selected freeze-dried subsamples were distributed to each of fifty participating laboratories from twenty-four countries. Specific requirements for analyses and reporting of data were precluded given the realities of variations in local and regional regulating requirements, economic considerations, and availability of properly educated and trained personnel. The use of either of the following were recommended: U.V.-fluorescence spectrometry, HPLC, GC or GCMS for measurement of hydrocarbons after extraction and isolation. A written explanation of methodology used was requested from each laboratory. Analyses in the W.H.0.I. laboratory showed that relative standard deviations of+ 10% could be attained for U.V.-fluorescence analyses of either freeze-dried or wet homogenates and did not markedly vary with the use of either chrysene or an EPA/API Arabian Light Crude Oil as a calibration sample. Gas chromatographic analyses for alkanes were less precise with r.s.d.'s (relative standard deviations) of+ 10 to 50% because of the low relative abundance of n-alkanes and branched alkanes in the gas chromatographic signal. GC/MS quantitative analyses in the W.H.0.I. laboratory gave+ 5% to+ 17% r.s.d. for concentrations of 6 x 10-9 g/g dry weight tissue to 200 x 10-9-g/g dry weight tissue for seven PAH. The data show that freeze-drying resulted in the loss of naphthalenes through phenanthrene in the aromatic hydrocarbons and resulted in a change of tissue matrix which could cause substantial inaccuracies in reported concentrations depending on extraction procedures and checks on recoveries.