Chemical fingerprinting of petrochemicals for arson investigations using two-dimensional gas chromatography - flame ionisation detection and multivariate analysis

Abstract

Two-dimensional gas chromatography is a mature, yet underutilised, separation technique able to provide the high resolution and peak capacity required for the study of complex samples such as oils. This paper presents the development of a comprehensive two-dimensional gas chromatography method with flame ionisation detection to profile easily available ignitable liquids commonly found in arson cases. The use of 2D chromatograms to profile different potential ignitable liquids was also explored for classification purposes. The chemical fingerprints produced were visually different and allowed the distinction of all the petroleum products tested. How the chemical fingerprints of each fuel changed over time was also assessed. Each sample was subjected to weathering with aliquots (1 mL) being collected every half hour for a five-hour period. Principal component analysis of the resulting data was able to demonstrate the effect of weathering for all fuels tested and established that it was still possible to differentiate between the various petrochemicals even after weathering. The work demonstrates an optimised analytical method for petrochemical product analysis that provides forensic scientists with a robust, fast and sensitive technique that can be used to determine not only which ignitable liquid was used in a fire (even after the fact) but also provide information on the specific fuel used.