GeoVOC: A SIFT-MS method for the analysis of small linear hydrocarbons of relevance to oil exploration

The rate coefficients of the ion–molecule reactions between O2+, H3O+, and a range of linear saturated hydrocarbons, and between common hydrocarbon product ions from these reactions and water were determined using a flowing afterglow selected ion flow tube mass spectrometer. Using these data, the selected ion flow tube-mass spectrometry (SIFT-MS) technique was applied to the real-time measurement of linear saturated hydrocarbons in dry and moist headspace samples without sample preparation. Using a Voice100 SIFT-MS instrument the Geochemical VOC method (GeoVOC) has been assessed against calibrated standards and found to give an experimental RMS precision to within 2% for dry and 6% for humid hydrocarbon samples in the ppm range. The application of SIFT-MS and development of the GeoVOC method offers a fast convenient means of assessment of hydrocarbon seeps.