Development of a certified reference material for benzo[a]pyrene and benz[a]anthracene in olive oil

This paper describes the development of an olive oil certified reference material containing benzo[a]pyrene and benz[a]anthracene. A method combining solid phase extraction and gas chromatography-isotope dilution mass spectrometry was used for the assignment of certified values and long-term stability study. The method was demonstrated to be suitable for the value assignment of both polycyclic aromatic hydrocarbons (PAHs) as our result was in good agreement with those from other metrology institutes in an international comparison (CCQM-K146) on determination of benzo[a]pyrene in olive oil. A metrological approach was taken to consider potential biases when certifying the mass fraction values of these two PAHs. The certified values with their associated uncertainties at approximately 95 % confidence level obtained for benzo[a]pyrene and benz[a]anthracene in olive oil were 9.85 µg/kg ± 0.75 µg/kg and 8.05 µg/kg ± 0.48 µg/kg, respectively. The measurement uncertainty was obtained by combining the uncertainty contributions from characterisation, homogeneity and stability of the material. Since the mass fraction levels of PAHs in the CRM are about five times higher than the regulatory limits or quantification limits, the practical use of the CRM is as a positive control for PAH monitoring in edible oil samples.