The determination by gas chromatography with atomic emission detection of total sulfur in fuels used as forensic evidence

In Japan, taxed diesel fuel from non-taxed fuel oil-A is illegally produced by removing coumarin, which is added as a non-taxed marker. The coumarin is removed using concentrated sulfuric acid and this produces a high viscosity and hazardous material, called “sulfuric acid pitch”, as a by-product. This compound has a detrimental effect on the environment and is hazardous to humans. The actions have been associated with organized crime with the illegally gained taxes becoming financial bases. To discriminate legal and diesel oil from illegal product, the peak area ratio RSC, the ratio of total sulfur to carbon (>C14), was used. RSC is calculated by the total areas of sulfur and carbon (>C14) from the gas chromatogram obtained by gas chromatography-atomic emission detection (GC-AED). Sulfur in legal diesel fuels is strictly regulated by a maximum limit, which was 50 ppm (and is now 10 ppm), but in the preparation of illegal diesel oil, in which coumarin is eliminated, sulfur cannot be removed. Therefore, the RSC of fuel oil-A and illegal fuel oil is over 15, whereas those for legal fuel oil and diesel fuel are under 2.0. Furthermore, these ratios do not change in weathering experiments. GC-AED was applied to an actual arson case and was found to be effective for the determination of total sulfur in trace amounts of accelerants detected in fire debris at the arson scene, and hence was effective for the characterization of the ignitable liquids used.