Measurement of PAHs in environmental matrices: results from an interlaboratory comparison on the different steps of the measurement procedure

Proficiency testing (PT) is becoming a feature of laboratory accreditation and the PT results are used to assess the technical competence of the participating laboratories. ISPRA (former APAT) plays an important role in supporting the Italian laboratories belonging to the network of the Regional Environmental Agencies to improve the quality of their analytical measurements. As a consequence, ISPRA organized an interlaboratory comparison to assess the performance of the laboratories on PAH measurement procedure. The interlaboratory comparison was drawn separating the different steps of the measurement (from the extraction to the instrumental measurement). Two matrix reference materials: (1) a polluted soil and (2) an extract reference material of the same polluted soil and a “blind” PAH mixture standard stock solution were distributed to 59 Italian laboratories. The results of interlaboratory comparison showed a significant dispersion of the PAH measurements that masks the effects of the different extraction and cleanup procedures used, but it is consistent with the results of other European interlaboratory comparisons.