Solid Phase Microextraction (SPME) and HAPSITE ER: Detection of an Explosive and Several Explosive Taggants in Air

Importance of Topic

A rapid and sensitive approach for detecting trace levels of explosives and their taggants in air samples is crucial for security screening, forensic investigations, and environmental monitoring. Combining solid phase microextraction (SPME) with a portable GC/MS system extends analytical capabilities into the field, enabling on-site sampling and analysis without complex sample preparation.

Objectives and Study Overview

The primary goal was to assess the performance of a PDMS/DVB SPME fiber coupled to a HAPSITE ER portable GC/MS for the detection of one peroxide explosive and six nitroaromatic taggants in air. Target compounds included:

• Triacetone triperoxide (TATP)
• 2-Nitrotoluene, 3-Nitrotoluene, 4-Nitrotoluene
• 2,3-Dimethyl-2,3-dinitrobutane (DMNB)
• 2,4-Dinitrotoluene (2,4-DNT)
• 2,6-Dinitrotoluene (2,6-DNT)

Methodology

An empty 40 mL VOA vial was spiked with known amounts of taggants and TATP to simulate an air sample. The SPME fiber was exposed to the headspace for 10 minutes, allowing adsorption of the semi-volatile analytes onto the PDMS/DVB coating. After sampling, the fiber was transferred to the SPME sampling chamber of the HAPSITE ER, and thermal desorption was conducted at 250 °C. GC separation used an Rtx-1MS column with a temperature program from 60 °C to 200 °C. Mass spectral data were collected over 43–300 amu at 1 scan/s during a 15-minute run.

Used Instrumentation

• HAPSITE ER rugged portable GC/MS with universal SPME interface
• SPME Sampling System including PDMS/DVB fiber and protective holder
• Rtx-1MS capillary column (15 m × 0.25 mm × 1.0 μm)

Results and Discussion

The total ion chromatogram demonstrated clear separation of all seven taggants and TATP within a single run. Retention times ranged from approximately 6.2 min for nitrobenzene to 9.8 min for 2,4-DNT. The high affinity of the PDMS/DVB fiber for nitroaromatic compounds enabled reliable adsorption at low vapor concentrations. Rapid desorption and MS detection confirmed each analyte with minimal carryover.

Benefits and Practical Applications

This combined SPME-GC/MS approach offers:

• On-site trace detection of explosives and taggants without solvent extraction
• Short analysis times suitable for security checkpoints and mobile forensic units
• Enhanced sensitivity for low-volatility semi-volatile compounds

Future Trends and Opportunities

Advances may include novel fiber coatings tailored to specific explosives, shorter GC gradients for faster screening, integration with automated sampling robotics, and coupling with machine learning for real-time identification. Miniaturization of MS detectors could further improve portability and deployment in remote locations.

Conclusion

The study validates the effectiveness of SPME sampling combined with the portable HAPSITE ER GC/MS system for rapid field detection of a peroxide explosive and multiple taggants. The method demonstrates strong potential for enhancing security and forensic capabilities through sensitive, on-site analysis of trace contaminants in air.