The European Union Reference Laboratory for Heavy Metals in Feed and Food (EURL-HM) organised a proficiency test (EURL-HM-23) for the determination of total As, Cd, Pb, Hg, and inorganic As (iAs) in palm kernel expeller to support theo Directive 2002/32/EC on undesirable substances in animal feed. This PT was open only to National Reference Laboratories (NRLs). The EURL-HM-23 test item was a palm kernel expeller spiked with As, Cd, Hg and Pb. The homogeneity and stability of the test item were evaluated and the assigned values were derived from the results reported by the selected expert laboratories.
Thirty four National Reference Laboratories from thirty countries (all EU member states plus Iceland and Norway) registered to the exercise and reported results. Laboratory results were rated using z- and zeta (ζ-) scores in accordance with ISO 13528:2015. The following relative standard deviations for proficiency assessment (σpt) were set according to the modified Horwitz equation: 15% for total As and iAs; 16% for Cd; 17% for Pb and 22% for Hg. More than 87% of the participating NRLs reported satisfactory results (according to the z-score) for total As, Cd, Pb and Hg, and more than 76% for iAs, thus confirming their ability in monitoring maximum levels set by the EU Directive 2002/32/EC. Most of the laboratories provided realistic estimates of their measurement uncertainties.