Report of the Tenth Interlaboratory Comparison Organised by the European Union Reference Laboratory for Heavy Metals in Feed and Food - IMEP-110: Total Arsenic, Cadmium, Mercury and Lead in Vegetable Food

Abstract

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 tenth ILC of the EU-RL-HM which focused on the determination of total arsenic, cadmium, mercury and lead in vegetable food. The test material used in this exercise was the Standard Reference Material SRM 1570a, spinach leaves of the National Institute of Standards and Technology (NIST). The material was rebottled and relabelled to prevent recognition by the participants and was dispatched at the beginning of June. Each participant received one bottle containing approximately 15 g of test material. Thirty-five laboratories from 24 countries registered to the exercise of which 35 reported results for total Cd and total Pb, 32 for total As and 31 for total Hg. The assigned values for total As, Cd and Hg are the certified values taken from the SRM 1570a certificate. For total Pb, the "information value" provided by NIST in the SRM certificate was used as assigned value. The uncertainties of the assigned values (uref) for total As, Cd and Hg, were taken directly from the CRM certificate as provided by the producer. No uref is provided by NIST for the total Pb concentration because the total Pb content is only provided as "information value". Participants were invited to report the uncertainty of their measurements. This was done by the majority of the laboratories taking part in this exercise. Laboratories' results were rated with z- and zeta-scores for total As, Cd, and Hg in accordance to ISO 13528. No zeta-scores were given for total Pb because uref was not known for that measurand. The standard deviation for proficiency assessment (also called target standard deviation) was fixed to 15 % for all the measurands by the advisory board of this ILC, on the basis of the outcome of previous ILCs organised by the EU-RL-HM and on the state-of-the-art in this field of analysis. More than 80 % of the participants performed satisfactory for total Cd and Hg. Around 70 % of the participants obtained a satisfactory z-score for total arsenic with a relatively high number (8 laboratories) of participants having overestimated the total content of arsenic in the test material. When looking at the zeta-scores, 60 to 65 % of the reported results were satisfactory when the associated uncertainties are taken into account.JRC.DG.D.6-Food Safety and Qualit