A more accurate analysis of alkylated PAH and PASH and its implications in environmental forensics

Abstract

The accurate measurement of polycyclic aromatic hydrocarbons (PAH), polycyclic aromatic sulfur heterocycles (PASH), and their alkylated homologues is essential at all levels of risk assessment and remedial decision-making. In the field of environmental forensics, diagnostic ratios of these compounds are used to delineate fossil fuel-based sources from one another and to assess the degree of weathering occurring on-site. Fresh and weathered coal tar and crude oil samples from different locations were analysed by gas chromatography/mass spectrometry. The same files were analysed by selected ion extraction of one-ion and two-ion signals from full-scan data and compared to a new data analysis method using spectral information from homologous isomers. Findings showed that using too few ions produced false positives and concentrations much higher than those found using the homologous isomer spectral method, which adversely affected the corresponding diagnostic ratios used by forensic scientists.

Keywords:

• alkylated PAH
• alkylated PASH
• PAH₃₄
• diagnostic ratios
• environmental forensics
• fragmentation patterns
• oil spill fingerprinting
• weathering
• GC/MS

Acknowledgements

The authors appreciate the assistance of Gerstel (GmbH and USA), Agilent Technologies, and Shimadzu for their contribution of instrumentation used in this research. Also appreciated are the utilities that provided samples for this project.