Report on the interlaboratory comparison organised by the European Union Reference Laboratory for Polycyclic Aromatic Hydrocarbons : four marker PAHs in coconut oil

This report presents the results of the interlaboratory comparison (ILC) organised as a proficiency test (PT) by the European Union Reference Laboratory for Polycyclic Aromatic Hydrocarbons (EURL-PAHs) on the determination of the four EU marker PAHs, benz[a]anthracene (BAA), benzo[a]pyrene (BAP), benzo[b]fluoranthene (BBF) and chrysene (CHR) in coconut oil. The test material used in this exercise was commercial coconut oil, acquired from a local supermarket and spiked with a finely melted and homogenised mixture of PAHs in the EURL-PAH premises. In addition participants received a solution of PAHs in toluene or acetonitrile (solvent chosen by them) with known PAH content for the verification of their instrument calibration. Twenty-eight officially nominated National Reference Laboratories (NRLs) and 23 Official food Control Laboratories (OCLs) of the EU Member States, Norway and Iceland participated to the study. The test material was characterised by the EURL-PAH. The assigned values and their uncertainties were determined from independent replicate measurements on two different days by isotope dilution mass spectrometry which confirmed the nominal values derived from the gravimetric preparation. Participants were free to choose their method of analysis. The performance of the participating laboratories in the determination of the target PAHs in the test material was expressed by both z-scores and zeta-scores. Additionally, the compliance of reported method performance characteristics was checked against specifications given in legislation. This PT demonstrated the competence of the participating laboratories in the analysis of regulated PAHs in coconut oil. About 82% of the reported test results were assessed as satisfactory, based on the z-scores. Participants were requested to assess the compliance of the sample against legislative limits. Eighty six percent of the participants assessed correctly the compliance of the test material.