EURL-FA control proficiency test report : determination of the mass fraction of the total selenium in compound feed for rabbits

The European Union Reference Laboratory for Feed Additive Control (EURL-FA Control) organised a proficiency test (PT) for the determination of the mass fraction of total selenium in compound feed, to support the Commission Directive 86/403/EEC concerning additives in feeding stuffs. 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, among others, selenium as sodium selenite) which, after appropriate processing, was bottled, labelled and dispatched to participants on May 22, 2018. 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 four OCLs from 20 countries - representing several EU Member States, Norway and Switzerland - registered to the exercise and reported results at the end of June 2018. Laboratory results were rated using z' and ζ (zeta) performance scores in accordance with ISO 13528:2015. The relative standard deviation for proficiency assessment (σpt) of 15 % of the assigned value was derived from the reproducibility standard deviation reported in the CEN standard EN 16159:2012. Twenty three (out of 25) laboratories reported satisfactory results (according to the z' score). This confirms the ability of most NRLs in monitoring maximum levels set by the Commission Directive 86/403/EEC concerning additives in feeding stuffs.