European interlaboratory comparison exercise for the analysis of PAHs on PM10 quartz filters

Eighteen European reference laboratories of air quality had been involved in a comparison of polycyclic aromatic hydrocarbon analysis based on particulate matter (PM) field samples collected on quartz filter. Four PM10 samples and two blanks were selected for the comparison with the aim of covering a representative range of concentrations typical of ambient air. Laboratory results were treated according to International Organization for Standardization 5725 from which repeatability and reproducibility values for the comparison were calculated. In general, intercompound median repeatability and reproducibility values ranged between the samples from 2.1 to 7.4% and 23.6 to 61%, respectively. The median relative overall expanded uncertainty (OEU) was 30% for the highest concentration filter sample reaching 50% for the lowest concentration filter samples. The OEU was higher for the lighter compounds (phenanthrene and anthracene), characterized by a higher blank level, and for compounds (chrysene or dibenzo[a,h]anthracene), which showed difficult analytical resolution. The median OEU and the analytical relative expanded uncertainties estimated by the participants were in line with the data quality objectives of the European Directive 2004/107/EC. No significant differences were observed when comparing the different analytical techniques from the exercise's results. However, other factors such as the use of certified reference materials and the laboratory blank were important causes of biases. Moreover, the chromatographic separation of several isomers was noted suggesting the importance of the use of specific columns more appropriate to the separation of unresolved isomers.