Detection of Accelerants in Arson Residues using Thermal Desorption-GC/MS

Importance of the Topic

Fire debris analysis for flammable accelerants plays a critical role in forensic investigations of suspected arson events. By detecting residual traces of gasoline, kerosene, diesel or other solvents, analysts provide legal evidence to determine fire origin and support judicial outcomes.

Objectives and Overview

This study demonstrates the use of thermal desorption coupled with gas chromatography–mass spectrometry (TD-GC/MS) to identify semivolatile accelerant residues in charred fire debris. It evaluates methodology for simulating arson scenarios on wood samples and compares chromatographic profiles of standard accelerants and post-combustion residues.

Methodology and Instrumentation

Wood samples were exposed to 8–10 mL of accelerant (gasoline, kerosene, diesel) for 5–10 minutes, ignited, then extinguished. After cooling, 50 mg of uncontaminated wood debris was collected and placed in a thermal desorption tube. Analysis employed a Dynatherm 9300 thermal desorber interfaced to a GC/MS system.

Instrumentation

• Thermal Desorber: Dynatherm 9300
  • Valve oven temperature: 130 °C
  • Transfer line temperature: 130 °C
  • Tube heat: 100 °C for 1 min
  • Trap heat: 300 °C for 5 min
• GC/MS System
  • Column: CP-Select 624, 30 m × 0.25 mm × 0.14 µm
  • Carrier gas: Helium, 50:1 split ratio
  • Injector temperature: 300 °C
  • Oven program: hold at 30 °C for 3.2 min, ramp 8 °C/min to 200 °C, hold 1 min

Main Results and Discussion

Chromatograms of paper tissue spiked with gasoline and kerosene standards exhibited expected low-, medium- and high-boiling peaks. Dynamic headspace analysis of charred debris retained only semivolatile components, yet preserved a clear gasoline fingerprint. Reproducibility trials on carpet samples spiked with 200 ng/µL of 4-phenylcyclohexene yielded an average area count of 4.25 × 10^7 with a relative standard deviation of 1.87 %.

Benefits and Practical Applications

• Non-destructive thermal desorption preserves sample integrity and prevents loss of semivolatiles.
• Integration with GC/MS delivers sensitive and specific identification of complex accelerant mixtures.
• The method provides reliable evidence for forensic casework and supports legal proceedings.

Future Trends and Applications

Advances may include enhanced sorbent materials for targeted trapping of ultralow-level compounds, miniaturized GC/MS systems for on-site screening, and machine learning algorithms for automated interpretation of complex chromatographic patterns.

Conclusion

Thermal desorption–GC/MS offers a robust approach for detecting flammable accelerants in fire debris. It reliably captures semivolatile profiles post-combustion, ensuring accurate identification of gasoline, kerosene and diesel residues in forensic investigations.

References

No formal literature references were provided in the original text.