Fixing False Negatives, Using 2DGC-TOFMS to Correctly Identify Ignitable Liquid Residues in Wildfire Investigations – Pittcon 2019

Dr. Sandau to present on cutting edge ILR analysis at Pittcon 2019!

Dr. Court Sandau will present Fixing False Negatives, Using 2DGC-TOFMS to Correctly Identify Ignitable Liquid Residues in Wildfire Investigations,  authored by Court Sandau, Phil Richards, Lisa N. Kates, and Michelle Misselwitz, at Pittcon 2019.


Wildfires continue to grow in frequency and intensity. Over 80% of wildfires are human caused, with over 20% being attributed to arsonous acts. The ability to detect ignitable liquid residues (ILRs) in wildfire debris samples can be very problematic compared to structural fire debris samples.

Detection of ILRs in wildfire debris is complicated by the presence of natural interferences. Wildfires provide exceptionally difficult matrices compared to structural fires due to the facts that: ILRs are present at lower concentrations; ILRs are more dispersed; thousands of natural compounds are present at very high concentrations compared to ILRs; structural similarity of natural compounds to ILR indicator compounds; and matrix combustion forms thousands of interfering compounds.

The resolving power of two-dimensional gas chromatography (2DGC) combined with the sensitivity of a TOF-MS permits superior separation and detection of ILR from matrix interferences compared to conventional one-dimensional gas chromatography (1DGC). The high abundance of natural interferences dwarfs the ILR compounds in size and will mask their detection using conventional 1DGC. As arsonous wildfires can ignite with very low volumes of ignitable liquid,  better detection limits are required in order to find and identify ILRs in wildfire debris samples.

Case samples analyzed on both 1DGC and 2DGC showed re-analysis by 2DGC changed 7% of negative samples to positive for ILR, and 22% went from tentative to positive for ILR. Inspection of the Stauffer compounds shows some groups are more useful for ILR identification than others. The Three Musketeers Group was ubiquitous, while the Twin Towers and Five Fingers Groups were non-detects by 1DGC but present in up to 90% of positive samples by 2DGC.

This presentation will summarize how 2DGC-TOFMS was used to positively identify ILRs in wildfire debris samples when conventional methods were unable to determine ILR presence.

Find more information about Pittcon 2019, here.