In case of oil spill on the ocean, identification of the origin of spilled oil is very important for further investigation. However, it is difficult to distinguish between gas oils and fuel oil “A”s by using FID-gas chromatography because of apparent similarity in the chromatographic patterns obtained from these oils, especially when the oils are weathered.
In this report, we developed a new method to distinguish unknown oils into gas oils and fuel oil “A”s, using gas chromatographic/mass spectrometry with selected ion monitoring (GC/MS/SIM). Dibenzothiophene (DBT) derivatives (e.g., 4-methylDBT, 4,6-dimethylDBT, etc.) were found to be used as index compounds for classification of oils. DBT derivatives were detected clearly from the fuel oil “A”s by GC/MS/SIM monitored at
m/z 198 and 212 but not from gas oils. It should be noted that chromatographic patterns of DBTs were unchanged even if these oils were highly weathered. These results indicate that the present method is useful for identification of spilled oils on the ocean.
Moreover, further classification of chromatographic patterns from fuel oil “A”s and comparison of index peak ratios (4MDBT/C16) were found to be useful to distinguish among fuel oil “A”s from different origins even if these oils were weathered to some extent.
Although it is often that only very small amounts of oil samples could be obtained from the ocean, the high sensitivity of GC/MS/SIM enabled to analyze them.
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