IMEP-33, total cadmium and lead in baby food : interlaboratory comparison report, December 2011

The Institute for Reference Materials and Measurements (IRMM) of the Joint Research Centre (JRC), a Directorate-General of the European Commission, operates the International Measurement Evaluation Programme® (IMEP). It organises interlaboratory comparisons (ILC's) in support to EU policies. This report presents the results of an ILC which focussed on the determination of total Cd and Pb in baby food in support of Commission Regulation (EC) No 1881/2006 of 19 December 2006 setting maximum levels for certain contaminants in foodstuffs. The test material used in this exercise was baby food formula purchased in a local pharmacy and prepared by the Reference Material Unit of the IRMM for this exercise. Each participant received one bottle containing approximately 15 g of test material. Sixty-six laboratories from 23 countries registered to the exercise and 61 of them reported results. Participants were asked to analyse the measurands in the powder and in the reconstituted form. The assigned value for total Cd was determined by LGC Ltd (UK) and IRMM using direct isotope dilution inductively coupled plasma mass spectrometry. The assigned value for total Pb was determined at IRMM using the same technique as for Cd. The standard deviation for proficiency assessment σ was set at 22 % of the assigned value based on the modified Horwitz equation. Laboratories were rated with z- and ζ-scores (zeta-scores) in accordance with ISO 13528. Most of the participants reported uncertainties with their results. The outcome of this exercise is clearly characterised by the very low level of Cd and Pb content in the test material which triggered a high number of "less than" values, overestimation especially for lead very likely due to contamination, and a visible method influence in the case of lead. The results were also evaluated with regard to the reported limit of detection and some incoherencies were observed here as well. Finally, the dilution factor between the reconstituted form and the powder, which should be 8, was investigated.