Advancement in oil forensics through the addition of polycyclic aromatic sulfur heterocycles as biomarkers in diagnostic ratios.

In current oil spill forensics, diagnostic ratios of hydrocarbon biomarker responses are commonly used to compare oil spill samples to source materials in order to determine the identity of the oil. This well recognized procedure was developed by the European Committee for Standardization (CEN) with corresponding published EN 15522-2 Oil Spill Identification guidelines. However, it is further recognized that weathering can have a negative effect on some of the biomarkers used in the analysis, leading to decreased confidence in the result. In this study, polycyclic aromatic sulfur heterocycles (PASHs) and their alkylated forms (APASHs) were assessed for their potential as additional biomarkers. With the aim of identifying stable PASHs and APASHs useful as weathered oil biomarkers, the superior specificity of gas chromatography with high resolution mass spectrometry was exploited to determine chromatographic peak responses for sixteen petroleum oil samples. Extensive study, involving microcosm extreme weathering and spreadsheet development, led to the identification of 19 new diagnostic ratios based on newly discovered stable PASH and APASH biomarkers. Application of the extended diagnostic ratio suite showed high potential to improve the forensic attribution of post-spill weathered oil back to its original source.