Forensic Investigations of Diesel Oil Spills in the Environment Using Comprehensive Two-Dimensional Gas Chromatography–High Resolution Mass Spectrometry and Chemometrics: New Perspectives in the Absence of Recalcitrant Biomarkers

Abstract

Forensic investigations of oil spills aim to find the responsible source(s) of the spill. Oil weathering processes change the chemical composition of the spilled oil and make the matching of oil spill samples to potential sources difficult. Diesel oil spill cases are more challenging, because biomarkers recalcitrant to long-term weathering are absent. We developed and tested a new method for the analysis and matching of diesel oil spills using two-dimensional gas chromatography–high resolution mass spectrometry (GC × GC – HRMS) and 2D-CHEMSIC (2-Dimensional CHEMometric analysis of Selected Ion Chromatograms), an extension of the CHEMSIC method to GC × GC data. The 2D-CHEMSIC performs pixel-based analysis using chemometrics on concatenated sections of 2D extracted ion chromatograms to assess the overall chemical variability of the samples, with potential applications for matching spill-source pairs in forensic investigations. The method was tested on samples from a number of diesel oil spill cases, (i) distinguishing chemically similar source diesels, (ii) investigating weathering effects on spill samples to determine type and degree of weathering, and (iii) improving the matching of diesel oil spills affected by weathering. Positive matches for spill-source pairs were identified after excluding the signals from the hydrocarbons most susceptible to evaporation, and photo-oxidized spills were also matched due to the presence of unaffected hydrocarbons. Forensic diagnostics obtained by the 2D-CHEMSIC were validated by the conventional CEN-Tr method.

Recent forensic applications of enhanced chromatographic separation methods

“…Unfortunately, lighter compounds, helpful for identification, are more susceptible to weathering and biodegradation. A study by Alexandrino et al [17] used comprehensive 2D-GC with high-resolution MS (2D-GC-HRMS) with chemometric analysis to analyze similar diesel oils and weathered samples. Thirty-two samples were studied with 12 coming from actual cases of marine spills.…”

“…In addition, enhanced separation methods in liquid chromatography and enhanced separation methods in supercritical fluid chromatography applicable to the forensic discipline from 2015 to 2020 will be reviewed. The applications discussed include arson investigations [13][14][15][16], environmental forensics [17,18], sexual assault investigations [19], toxicology [6,11,[20][21][22], and illicit drug analysis [5,7,8,21,[23][24][25][26][27][28].…”

Indicators of Natural and Anthropogenic Emission Source Impact

“…Finally, the relative abundance of petrol components (e.g. pristane and phytane) compared to n-alkanes was considered to highlight the vehicle emission impact [Hamilton et al 1984, Alexandrino et al 2019, Alkhafaji 2021.…”

Portable Analytical Techniques for Monitoring Volatile Organic Chemicals in Biomanufacturing Processes: Recent Advances and Limitations

“…GC is one of the most popular and active analytical technologies in bioengineering (Mcnair and Miller, 2010). The analytes of interest could be in gas, liquid or solid, with molecular weight ranging from 2 to 1,000 Da, which has shown extensive applications in food inspection (Bianchi et al, 2006), pesticide detection (Zhang et al, 2006), environmental monitoring (Viola et al, 2019), forensic investigation (Alexandrino et al, 2019), and quality control of petroleum products (Coutinho et al, 2018). In addition, GC analysis is widely used in the inspection of human organ functions (Young et al, 2019) and screening of cancer cells, such as hematological malignancies (Tang et al, 2017) and breast cancer (Lavra et al, 2015).…”