Inter-comparability of analytical laboratories in quantifying polycyclic aromatic hydrocarbons collected from industrial emission sources

Abstract

We report an inter-laboratory comparison of analytical laboratories involved in the quantification of polycyclic aromatic hydrocarbons (PAHs) collected by sampling organisations from industrial stacks (e.g. waste incinerators). Four reference solutions were prepared containing nominally 10 ng/ml, 50 ng/ml, 200 ng/ml and 500 ng/ml of naphthalene, benzo[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene and dibenzo[a,h]anthracene prior to despatch to five analytical laboratories with quantification requested in accordance with ISO 11338-2. Across four of the laboratories (the 5th returned unusable data), significant deviations from the reference concentrations were found frequently in excess of the benchmarks of 37 %—from the validation data in ISO 11338-2—and 21 %—from the Environment Agency for England’s Monitoring Certification Scheme. Also, much of the variance was systemic in nature indicating a possible issue with the quality of some of the stock solutions used by the laboratories for calibration. Whilst more proficiency testing would be welcomed to monitor and improve performance, this should be provided in addition to more support for analytical laboratories. A key mechanism of support is the standards themselves and there is a timely opportunity in that ISO/TC 146/SC 1 are due to revise ISO 11338. Possible improvements include full validation of high performance liquid chromatography and gas chromatography–mass spectrometry methods (to better understand what performance can reasonably be expected from laboratories), a requirement to correct results to individual laboratory PAH extraction efficiency, and a required uncertainty stipulated for the overall method (also aiding setting pass/fail criteria for proficiency testing).