From the 1st of January 2008, the laboratory for Trace Elements at Sciensano (former CODA-CERVA), Tervuren, operates as National Reference Laboratory for Trace Elements in Food and Feed (NRL-TE). One of its core tasks is to organise proficiency tests (PTs) among laboratories appointed by the Federal Agency for the Safety of the Food Chain. This report presents the results of the proficiency test organised by the NRL-TE which focused on the determination of trace elements in food supplements. The results from the PT were treated in Sciensano, Tervuren.
The 2020 PT was obligatory for all laboratories approved for the analysis of heavy metals in foodstuff by the Federal Agency for the Safety of the Food Chain (FASFC). Eleven laboratories registered for and participated in the exercise.
The test material used in this test was a food supplement. The material was separated from the package after purchase and divided in small containers. Each participant received approximately 15 g of test material.
Participants were invited to report the mean value and measurement uncertainty on their results for arsenic (As), cadmium (Cd), lead (Pb) and mercury (Hg).
The assigned values (xa) and their uncertainty (u(xa)) were determined as the consensus of participant’s results. Standard deviations for proficiency assessment were calculated using the modified Horwitz equation.
Of the 11 laboratories that registered for participation, 11 submitted results for As, Cd and Pb, 10 submitted results for Hg. All but two of the z-scores that were calculated, were satisfactory. Estimation of a correct measurement uncertainty stays a difficult excersize: five of the calculated ζ-scores were unsatisfactory. Not all laboratories met the LOQ criteria for Hg [1].
No consensus value could be derived for Hg. The measurement of As was difficult, but overall the laboratories performed satisfactory. The performance of the laboratories to analyse Pb, and Cd in this matrix was very succesfull.
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