Report of the Ninth Interlaboratory Comparison Organised by the European Union Reference Laboratory for Heavy Metals in Feed and Food - IMEP-109: Total Cadmium, Lead, Arsenic and Mercury as well as Methylmercury and Inorganic Arsenic in Seafood

摘要

The Institute for Reference Materials and Measurements (IRMM) of the Joint Research Centre (JRC), a Directorate General of the European Commission, operates the European Union Reference Laboratory for Heavy Metals in Feed and Food (EU-RL-HM). One of its core tasks is to organise interlaboratory comparisons (ILCs) among appointed National Reference Laboratories (NRLs). This report presents the results of the ninth proficiency test (PT) of the EU-RL-HM which focused on the determination of total cadmium, lead, arsenic and mercury as well as methylmercury and inorganic arsenic in seafood.The test material used in this exercise was the Certified Reference Material (CRM) DOLT-4, dogfish liver of the National Research Council of Canada (CNRC). The material was relabelled to prevent recognition by the participants and was dispatched the second half of May 2010. Each participant received one bottle containing approximately 20 g of test material. Thirty-eight laboratories from 27 countries registered to the exercise of which 38 reported results for total Cd, 36 for total Pb, 33 for total As, 36 for total Hg, five for methylmercury and 10 for iAs. The assigned values for total Cd, Pb, As, Hg and methylmercury are the certified values taken from the DOLT-4 certificate. An attempt was made to establish an assigned value for inorganic As (iAs) using the results provided by a group of five laboratories expert in the field, following a similar approach to that used in IMEP-1071, a PT on total and inorganic arsenic in rice. Contrary to what was observed in IMEP-107, the results obtained by the expert laboratories for iAs was method dependent, therefore no assigned value could be established.The uncertainties of the assigned values, uref, were taken directly from the CRM certificate as provided by the producer for total Cd, Pb, As, Hg and methylmercury. Participants were invited to report the uncertainty of their measurements. This was done by the majority of the laboratories taking part in this exercise.Laboratory results were rated with z- and ¿-scores (zeta-scores) in accordance with ISO 135282. Since the concentration of iAs seems to be method dependent according to the results obtained by the expert laboratories, no scoring was provided to the laboratories that submitted results for iAs. The standard deviation for proficiency assessment (also called target standard deviation) was fixed to 15% by the advisory board of this ILC, on the basis of the outcome of previous ILCs organised by the EURL-HM and on the state-of-the-art in this field of analysis.Between 80 and 97.5 % of the laboratories performed satisfactory for total Cd, As, Hg and methylmercury. Regarding total Pb, 70 % of the laboratories scored satisfactory.