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 normalisation of organic contaminant concentrations in biological materials. Lipids are routinely determined gravimetrically after extraction of the material with chlorinated solvents. A new method substituting chlorinated solvents for a cyclohexane/isopropanol mixture was to be evaluated by an intercomparison exercise. The participating laboratories were requested to determine total lipid content in three different samples of fish tissue following their own procedures as well as the new method described in a standard protocol. No 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 reproducibilities below 10% were obtained in the exercise. The results indicate the applicability of the harmonised method for the determination of total lipids as a cofactor in the analyses of contaminant concentrations in marine biota samples. [ABSTRACT FROM AUTHOR]