First on-line analysis of petroleum from single inclusion using ultrafast laser ablation

For many years, geochemical analysis of petroleum from single inclusions has been a challenging objective for fluid inclusion studies. In this study, individual petroleum inclusions have been selectively opened and analysed, for the first time, by coupling an on-line femtosecond laser with a gas chromatograph-mass spectrometer (GC-MS). GC-MS chromatograms show straight chained, branched and cyclic alkanes and aromatic hydrocarbons with carbon numbers ranging from 4 (iso-butane) to 19 (pristane). The distribution of these compounds is similar to that observed by on-line bulk crushing, and pyrolysis artefacts such as alkenes and ketones were not detected. Hydrocarbons with higher carbon numbers appear to have remained in the extraction chamber, a limitation that may be overcome by improvements to the inlet system. This pilot study proves that ultrashort laser pulses can be used to liberate unaltered oil from individual inclusions, thereby creating exciting opportunities for further research aimed at determining the nature of different hydrocarbon palaeo-fluids trapped within single minerals.