The certification of the mass fractions of elements in mussel tissue : certified reference material ERM-CE278k

This report describes the production of ERM®-CE278k, a mussel tissue material certified for the mass fractions of 13 elements. The material was produced following ISO Guide 34:2009. The starting material was wild mussels (mytulis edulis) harvested off the coast of the Netherlands. The mussels were collected in late spring, steam-cooked, shelled and frozen. About 150 kg of mussel flesh was freeze-dried, frozen in liquid nitrogen and milled before sieving to obtain a fine powder. Between unit-heterogeneity was quantified and stability during dispatch and storage was assessed in accordance with ISO Guide 35:2006. Within-unit heterogeneity was quantified to determine the minimum sample intake. The material was characterised by an intercomparison among laboratories of demonstrated competence and adhering to ISO/IEC 17025. Technically invalid results were removed but no outlier was eliminated on statistical grounds only. Uncertainties of the certified values were calculated in compliance with the Guide to the Expression of Uncertainty in Measurement (GUM) and include uncertainties related to possible heterogeneity and instability and to characterisation. The material is intended for quality control and assessment of method performance. As any reference material, it can also be used for control charts or validation studies. The CRM is available in glass vials containing 8 g of dry powder closed under a nitrogen atmosphere. The minimum amount of sample to be used is 200 mg.