Cofactors in Biota: results of a German interlaboratory exercise on the determination of total lipids in fish tissue

The content of total lipids is a common cofactor necessary for a normalisat ion of organic contaminant concentrations in biological materials. Lipids a re routinely determined gravimetrically after extraction of the material wi th chlorinated solvents. A new method substituting chlorinated solvents for a cyclohexane/isopropanol mixture was to be evaluated by an intercompariso n exercise. The participating laboratories were requested to determine tota l lipid content in three different samples of fish tissue following their o wn procedures as well as the new method described in a standard protocol. N o significant differences in the overall means of total lipid content were found for the investigated samples regardless of the determination method. Using the harmonised protocol of the new method, between laboratory reprodu cibilities below 10% were obtained in the exercise. The results indicate th e applicability of the harmonised method for the determination of total lip ids as a cofactor in the analyses of contaminant concentrations in marine b iota samples.