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EURL-FA Control Proficiency Test Report: Determination of the mass fraction of the total cobalt in compound feed for rabbits

The European Union Reference Laboratory for Feed Additive Control (EURL-FA Control) organised a proficiency test (EURL-FAC 2017-2) for the determination of the mass fraction of total cobalt in compound feed, to support the Commission Implementing Regulation (EU) No 131/2014 concerning the authorisation of various cobalt(II) compounds as feed additives. This proficiency test was open to National Reference Laboratories (NRLs) and official feed control laboratories (OCLs). The material used as test item was a commercially available compound feed for rabbits (containing the coated granulated cobalt (II) carbonate, 3b304 ) which, after appropriate processing, was bottled, labelled and dispatched to participants on June 21, 2017. 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. Twenty one NRLs and two OCLs from 21 countries - representing EU Member States and Norway - registered to the exercise and reported results at the end of August 2017. Laboratory results were rated using z' and zeta scores in accordance with ISO 13528:2015. A relative standard deviation for proficiency assessment (σpt) of 16 % of the assigned value was set according to the modified Horwitz equation. Twenty (out of 23) laboratories reported satisfactory results (according to the z' score). This confirms the ability of most NRLs in monitoring maximum levels set by the Commission Implementing Regulation (EU) No 131/2014 in this type of animal feed. The majority (74 %) of the participating laboratories provided realistic estimates of their measurement uncertainties.