Molecular and isotopic analysis of oils by solid phase microextraction of gasoline range hydrocarbons

An improved method for molecular and stable isotope analysis of gasoline range hydrocarbons (C5–C10) in oils uses Solid Phase Microextraction. Analytes are sampled from the headspace above oil droplets and analyzed by gas chromatography and continuous-flow isotope-ratio mass spectrometry. Analytical considerations with this sampling technique include equilibration times, vapor pressure/temperature effects, and the presence of a complex matrix. Instrumentation factors such as column/split flows are also considered. The results are compared with an alternative purge and trap method. Molecular analyses prove reproducible between the two methods, however, stable carbon isotope ratios exhibit a non-systematic depletion and enrichment of 0.2–2.0‰ for 16 pre-selected compounds.