IMEP-112 : total and inorganic arsenic in wheat, vegetable food and algae (report of the twelfth interlaboratory comparison organised by the European Reference Laboratory for Heavy Metals in Feed and Food)

The Institute for Reference Materials and Measurands (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). Two of its core tasks are to provide advice to the Directorate General for Health and Consumers (DG SANCO) on scientific matters and to organise interlaboratory comparisons (ILC) among appointed National Reference Laboratories (NRLs). This report presents the results of the twelfth ILC of the EU-RL-HM (former CRL-HM) which focused on the determination of total and inorganic As in wheat, vegetable food and algae. The test items used in this exercise are: wheat, spinach (SRM 1570a from NIST) and an algae candidate reference material. The test items were processed (in the case of wheat), bottled and labelled at IRMM and dispatched to the participants the second week of May 2011. Each participant received three bottles containing approximately 20 g of wheat, 15 g of spinach and 5 g of algae, respectively. Participation in this exercise was not limited to the NRLs but was open to laboratories from all around the world, to be able to judge the state-of-the-art of the determination of total and, more in particular, inorganic As in several food commodities. Seventy-four laboratories from 31 countries registered to the exercise, of which - 64 reported results in wheat, 49 in spinach and 51 in algae for total As, and - 43 reported results in wheat, and 40 in spinach in algae for inorganic arsenic. Thirty of the participants were NRLs of the EU-RL-HM network, out of which 13 reported values for inorganic As. The assigned values for IMEP-112 were provided by the certificates when available and otherwise by a group of seven laboratories expert in the field. The uncertainties of the respective assigned values (uref) were derived from the standard deviation of the means provided by the experts (uchar) and from the contribution for homogeneity (ubb) and stability (ust). Laboratory results were rated with z-and ζ-scores (zeta-scores) in accordance with ISO 13528. The standard deviations for proficiency assessment (also called target standard deviation) were fixed 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 to : - 15 % for total and inorganic arsenic in wheat. - 22% for total arsenic and 25 % for inorganic arsenic in vegetable food, to account for the difficulty introduced by the relatively low concentration of both measurands in this test material. - 15 % for total arsenic and 22 % for inorganic arsenic in algae. Most of the participants performed satisfactorily for total arsenic and for inorganic arsenic in vegetable food (75 and 85 %); 60 % did for inorganic arsenic in wheat but only 20 % of the laboratories reported satisfactory results in the algae test material.