Report on the 8th inter-laboratory comparison organised by the European Union Reference Laboratory for Polycyclic Aromatic Hydrocarbons : Four marker PAHs in a dry extract of St John's wort

The proficiency test here reported concerned the determination of the contents of four marker polycyclic aromatic hydrocarbons (PAHs), and of their sum in an food supplements test sample. The set of marker PAHs consists of benz[a]anthacene, benzo[a]pyrene, benzo[b]fluoranthene, and chrysene. Participants to these PT were National Reference Laboratories for PAHs (NRLs-PAHs) and EU official food control laboratories. The number of participants was in total 48. The PT was organised according ISO Standard 17043:2010. The test material used was a commercial dry extract of St. John's wort. Participants also received a solution of the same PAHs either in acetonitrile or in toluene for checking their instrument calibration. The results from participants were rated with z-scores and zeta-scores. About 68 % of the reported results were attributed with z-scores with an absolute value of below two, which is the threshold for satisfactory performance.JRC.D.5-Standards for Food Bioscienc