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Assessing Carbon and Hydrogen Isotopic Fractionation of Diesel Fuel n-alkanes During Progressive Evaporation |
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| Authors: | Syahidah A. Muhammad Ph.D. Alan R. Hayman Ph.D. Robert Van Hale Ph.D. Russell D. Frew Ph.D. |
| Affiliation: | 1. Department of Chemistry, University of Otago, P.O. Box 56, Dunedin, New Zealand School of Industrial Technology, Universiti Sains Malaysia, Penang, 11800 Pulau Pinang, Malaysia;2. Department of Chemistry, University of Otago, P.O. Box 56, Dunedin, New Zealand;3. Department of Chemistry, University of Otago, P.O. Box 56, Dunedin, New Zealand Division of Nuclear Techniques in Food and Agriculture, International Atomic Energy Agency, P.O. Box 100, 1400, Vienna, Austria Additional information and reprint requests: Russell Frew, Ph.D. Department of Chemistry University of Otago P.O. Box 56 Dunedin New Zealand E-mail: rfrew@chemistry.otago.ac.nz |
| Abstract: | Compound-specific isotope analysis offers potential for fingerprinting of diesel fuels, however, possible confounding effects of isotopic fractionation due to evaporation need to be assessed. This study measured the fractionation of the stable carbon and hydrogen isotopes in n-alkane compounds in neat diesel fuel during evaporation. Isotope ratios were measured using a continuous flow gas chromatograph/isotope ratio mass spectrometer. Diesel samples were progressively evaporated at 24 ± 2°C for 21 days. Increasing depletion of deuterium in nC12–nC17 alkanes in the remaining liquid with increasing carbon chain length was observed. Negligible carbon isotope fractionation was observed. Preferential vaporization was measured for the shorter chain n-alkanes and the trend decreased with increasing chain length. The decrease in δ2H values indicates the preferential vaporization of the isotopically heavier species consistent with available quantitative data for hydrocarbons. These results are most important in the application of stable isotope technology to forensic analysis of diesel. |
| Keywords: | forensic science stable isotope compound specific hydrocarbon fractionation fingerprinting |