Chemometric Determination of Target Compounds Used to Fingerprint Unweathered Diesel Fuels

Abstract

Existing oil fingerprinting standard methods target mostly high-molecular-weight biomarkers for discrimination between samples. Fingerprinting of light petroleum distillates like diesel fuel is problematic with these methods because many of the target analytes are not present. To address this problem, 14 diesel fuel samples from refineries throughout the United States and Canada were analyzed by GC/MS. For each sample, peaks were integrated in 62 different extracted ion chromatograms that represented 22 classes of petroleum constituents. Over 300 individual peak ratios were calculated per sample. Principle components analysis (PCA) was used to reduce the number of ratios needed to differentiate the samples. Nine significant peak ratios were identified by PCA. The ratios included compounds in alkylbenzene, alkylphenanthrene, and sesquiterpane petroleum classes. The PCA model removed peak ratios that contributed to instrument replicate variability, which improved differentiation among samples. Real-world spill samples not subjected to evaporative or other weathering processes were used to test the robustness of the model with excellent results. The spill samples were readily seen to be significantly different. Additional studies such as the effects of weathering on these peak ratios are needed before this approach can be evaluated as a useful spill fingerprinting method.