Report on the 11th inter-laboratory comparison organised by the European Union reference laboratory for polycyclic aromatic hydrocarbons : four marker PAHs in spiked olive oil

The proficiency test here reported concerned the determination of the four marker polycyclic aromatic hydrocarbons (PAHs) in an olive oil test sample: 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 43. The PT was organised according to ISO Standard 17043:2010. The test material used was olive oil spiked with the target PAHs. Participants also received a solution of the PAHs either in an organic solvent for checking their instrument calibration. The results from participants were rated with z-scores and zeta-scores. About 94.4 % and 90.5 % of the results reported by NRLs and OCLs respectively were attributed with z-scores with an absolute value of below two, which is the threshold for satisfactory performance. The zeta-score ratings were worse, which indicates problems in the estimation of reliable measurement uncertainty values.