Sensitive and Fast Screening for Explosives: Utilization of Online Preconcentration and High Resolution Mass Spectrometryg

Significance of the Topic

The presence of explosive residues even at sub-parts-per-trillion levels in water sources poses a critical challenge for environmental safety and public health. Rapid and sensitive detection of these analytes supports contamination assessment, remediation strategies and regulatory compliance.

Aims and Overview of the Study

This work aims to establish a unified liquid chromatography–mass spectrometry method capable of screening 22 explosives and related degradation products in aqueous matrices in a single run. The approach integrates large-volume automated injection, online preconcentration and ultrahigh-resolution full-scan MS to improve sensitivity and throughput.

Instrumental Setup

The analytical platform comprises an EQuan MAX automated system coupled to a Thermo Scientific Hypersil GOLD PFP reversed-phase HPLC column for separation and a Thermo Scientific Exactive Orbitrap mass spectrometer operating under negative-ion APCI. Key parameters include:

• Injection volume: 4 mL via online loading column
• Mass resolution: 50 000 at full-scan (100–500 amu)
• Ionic source: APCI at 200 °C vaporizer, 80 µA corona current

Methodology

Water samples spiked with target compounds were processed through automated large-volume injection with a loading solvent (pure water) for preconcentration. Analytes were eluted by a gradient of 0.1 mM ammonium chloride in water and methanol and separated on a PFP stationary phase. Mass spectrometric data were acquired in full-scan at 5 ppm mass tolerance and quantified using linear or quadratic calibration over 0.5–1000 ppt ranges.

Main Results and Discussion

The method achieved limits of detection below 0.5–25 ppt and LLOQs ≤0.5 ppt for most analytes in pure water. When applied to spiked river water, all compounds were detectable at 100 ppt; half were quantified at 10 ppt and one third at 1 ppt. Sensitivity varied by compound, reflecting differences in trapping affinity and ionization efficiency. Ultrahigh resolution minimized background interference and facilitated accurate quantitation even in complex environmental matrices.

Benefits and Practical Applications

This high-throughput LC-MS protocol offers:

• Rapid screening of multi-class explosives in a single analysis
• Low-level quantitation suited for environmental monitoring
• Reduced sample preparation and solvent use through online extraction

Future Trends and Opportunities

Further enhancements may include optimized trap chemistries to boost affinity for low-trapping compounds, expansion to additional matrices such as soils and wastewater, and coupling with high-throughput data processing algorithms to support real-time monitoring networks.

Conclusion

The developed LC-MS workflow successfully balances speed, sensitivity and robustness, enabling sub-ppt detection of 22 explosives in water. Its integration of large-volume injection and ultrahigh-resolution MS positions it as a powerful tool for environmental surveillance and forensic investigations.

References

1. Yinon J, McClellan JE, Yost RA. Rapid Commun Mass Spectrom. 1997;11:1961–1970.
2. Zhao K, Yinon J. J Chromatogr A. 2002;977:59–68.
3. Ruzicka J, McHale KJ, Sanders M. Proceedings of the 57th ASMS Conference on Mass Spectrometry and Allied Topics; 2001; Philadelphia, PA.