QUASIMEME: a preliminary study on the effects of sample handling on the measurement of trace metals and organochlorine residues in mussels

As part of the development of quality measurement of trace metals and organochlorine residues in marine biota, the QUASIMEME Project undertook an interlaboratory study to determine the magnitude of the errors associated with the sample handling of mussels (Mytilus edulis) prior to analysis. Mussels were distributed to participating laboratories which homogenized and freeze-dried five pools of 10 mussels. Each pool was analysed both by the participants and by a reference laboratory. Systematic errors resulting from the freeze drying and from contamination during analysis for the trace metals, particularly lead and organochlorines, were identified. In general, the errors associated with the sample preparation were of similar magnitude to the final measurement of the trace metals, whereas the errors for the measurement of the chlorobiphenyls and the organochlorine pesticides still dominated the overall variance and bias for the analysis.