Results from two interlaboratory comparisons on the measurement of trace element contents in food supplements – State of the art of control laboratories in Europe

Abstract This article deals with the outcome of two interlaboratory comparison (ILC) projects run in parallel on the same material about the analysis of total As, Cd, Pb and Hg in food supplements. The IMEP-106 project was run for National Reference Laboratories (NRL) and the IMEP-28 was open to all control laboratories. Thirty-three NRLs registered to the IMEP-106 exercise and 62 laboratories registered to the IMEP-28 exercise. In the 91 laboratories who have submitted results, 29 countries were represented. The test material used was the candidate standard reference material SRM 3256 provided by NIST, the matrix being green tea food supplement. Most of the participants in both exercises have detected and quantified all measurands, despite small sample size and low contents. Furthermore, it can be said that measurement quality was similar between NRLs and the other laboratories. Finally, the pooling of the results of the two exercises allowed detecting a method influence in the determination of total Hg, with laboratories using solid sampling based methods performing better.