Fast Analysis of Fire Debris Using an Agilent 5975T LTM GC/MSD with Capillary Trap Sampling (CTS)

Importance of the Topic

Arson investigations rely on detecting traces of accelerants in fire debris to establish intent and evidence. Traditional methods like SPME require lengthy sampling and analysis, often hindering timely results. The combination of Capillary Trap Sampling (CTS) and a transportable Agilent 5975T Low Thermal Mass GC/MS improves speed and selectivity, enabling rapid on-site confirmation of common hydrocarbon accelerants.

Objectives and Study Overview

This study aims to develop and validate a fast analytical workflow for identifying fire accelerants using CTS paired with an Agilent 5975T LTM GC/MS system. Key goals include:

• Comparing volatile profiles of debris samples to a 97 RON gasoline standard.
• Evaluating CTS performance against the conventional SPME-GC/MS method.
• Applying the optimized method to real-world samples, including gasoline, banana oil, diesel, and aviation kerosene.

Methodology and Instrumentation

Sample collection employed direct headspace trapping of volatile compounds for 1 minute using a six-port Pora PLOT Q CTS probe.

• Instrumentation:
  
  • Agilent 5975T LTM GC/MS system
  • Agilent HP-5ms LTM column (10 m×0.18 mm, 0.18 μm) with 1 m deactivated guard
  • Split/splitless inlet with TSP, manual injection, split ratio 20:1
• Operating conditions:
  
  • Carrier gas: helium at 1.4 mL/min constant flow
  • Oven program: 40 °C (0.8 min), ramp to 50 °C (12 °C/min), to 100 °C (30 °C/min), to 180 °C (90 °C/min), to 220 °C (120 °C/min)
  • MS: EI ionization, full scan m/z 45–300, transfer line 230 °C, source 230 °C, quadrupole 150 °C
• Reagents and standards: 97 RON gasoline, kerosene, diesel, alcohols, organic solvents

Main Results and Discussion

• Trap column selection: A 20×0.32 mm Pora PLOT Q column provided efficient capture of gasoline volatiles.
• Gasoline profiling: Total ion chromatograms (TIC) showed predominant aromatic peaks (m/z 91) corresponding to benzene derivatives. AMDIS-NIST library enabled key component identification.
• Comparison with SPME: CTS reduced sample prep from 40 minutes to 1 minute and GC run time from 40 minutes to under 7 minutes, achieving comparable chromatographic patterns.
• Real case applications: Overlapping extracted ion chromatograms (m/z 91) confirmed gasoline residues on burned denim. CTS also differentiated banana oil by its high xylene and butyl acetate content.
• Extended testing: Diesel and aviation kerosene TICs revealed distinct light hydrocarbon profiles, validating method versatility.

Benefits and Practical Applications

• Rapid on-site sampling and analysis enable faster forensic decisions.
• Minimal matrix interference enhances selectivity and reduces sample preparation steps.
• Portable GC/MS configuration supports field deployment and immediate confirmation.
• Applicable to a wide range of accelerants including gasoline, kerosene, diesel, and solvents.

Future Trends and Applications

• Integration with machine learning for automated pattern recognition and library matching.
• Development of smaller, battery-powered GC/MS instruments for true field portability.
• Expansion of CTS probe materials and trap chemistries to target emerging accelerant classes.
• Real-time data sharing and remote control for collaborative forensic investigations.

Conclusion

The combined use of Capillary Trap Sampling and the Agilent 5975T LTM GC/MS delivers a fast, reliable approach for identifying fire accelerants. This method significantly shortens sampling and analysis times while maintaining high selectivity and accuracy, offering clear advantages for forensic laboratories and on-site investigations.

Reference

1. Lloyd JA, Edmiston PL. Preferential Extraction of Hydrocarbons from Fire Debris Samples by Solid Phase Microextraction. J Forensic Sci. 2003;48(1):