Report on the second inter-laboratory comparison test organised by the Community Reference Laboratory for Polycyclic Aromatic Hydrocarbons : 15+1 EU priority PAHs in edible oil and acetonitrile

This report presents the results of the 2nd inter-laboratory comparison (ILC) of the Community Reference Laboratory for Polycyclic Aromatic Hydrocarbons (PAHs) on the determination of the 15+1 EU priority PAHs in edible oil and acetonitrile, which was conducted along the lines of the IUPAC-AOAC International Harmonized Protocol for the Proficiency Testing of Analytical Chemical Laboratories. In agreement with the National Reference Laboratories the test materials used in this exercise were solutions of the 15+1 EU priority PAHs in edible oil and acetonitrile, respectively. The solutions were prepared gravimetrically. The assigned concentration values of PAHs in edible oil and in acetonitrile were calculated from the gravimetric preparation data. The uncertainties of the assigned values were determined for each analyte-matrix combination taking into account the uncertainty of the certified mass fraction of the neat substances as well as the uncertainty stemming from all manipulations of the respective materials. Uncertainties are reported as expanded uncertainties with a coverage factor of 2, approximating a 95% confidence interval. Only officially nominated National Reference Laboratories of the EU Member States, and from countries covered by the Technical Assistance and Information Exchange programme of the European Commission were admitted as participants. However, from latter countries only one laboratory reported results. The participants were free to choose the method for the analysis of the materials. z-Scores were calculated for the edible oil from the analytes' contents based on gravimetrical data. The reported values of the laboratories for PAHs in acetonitrile were not rated. Most of the reported values for the oil material lay within the 95% confidence interval of the target standard deviation, indicating that the participating laboratories were performing satisfactorily with respect to internationally accepted standards. However, in some cases a bias and/or a high variability were discovered and some analytes consistently caused specific problems. It is therefore recommended to investigate this further and to organise ILCs on a regular basis.