Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2025 Jan 20;10(3):owaf002.
doi: 10.1093/fsr/owaf002. eCollection 2025 Sep.

A novel signal processing approach enabled by machine learning for the detection and identification of chemical warfare agent simulants using a GC-QEPAS system

Nicola Liberatore  1 , Giorgio Felizzato  2 , Sandro Mengali  1 , Roberto Viola  1 , Francesco Saverio Romolo  2
Affiliations

A novel signal processing approach enabled by machine learning for the detection and identification of chemical warfare agent simulants using a GC-QEPAS system

Nicola Liberatore et al. Forensic Sci Res. .

Abstract

The detection and identification of chemical warfare agents (CWAs) present challenges in emergency response scenarios and for safety and security applications. This study presents the development and validation of an innovative analytical method using a gas chromatography (GC) and quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor for the detection of stimulants for six CWAs. Following the guidelines of the European Network of Forensic Science Institute (ENFSI) and the Commission Implementing Regulation (EU) 2021/808, the analytical method was validated. The validation results demonstrated the robustness and reliability of both the GC and QEPAS modules. Moreover, with regard to the toxicological threshold levels, this study highlights the efficacy of a prototype of a portable device for real security and safety applications. Furthermore, a machine learning (ML) approach was developed to automate the detection and identification of CWAs' stimulants. The workflow involved two interconnected stages: detection based on chromatographic retention times (RTs), and identification using infrared (IR) spectra through the one-class support vector machines classifier. The classifier was activated only after obtaining a positive detection based on RTs. The results highlight the ML model's effectiveness in CWA detection and identification, combining RT analysis and IR spectrum classification, achieving 97% accuracy at a 95.5% confidence interval and 99% accuracy at a 99.7% confidence interval; this result demonstrates the model's utility for real-world security and safety applications for CWAs.

Keywords: chemical warfare agents; chemical weapons; forensic sciences; gas chromatography; machine learning; quartz enhanced photoacoustic spectroscopy.

PubMed Disclaimer

Figures

Figure 1
Figure 1
Sensing scheme of the GC-QEPAS sensor. MEMS: micro-electromechanical systems; IR: infrared; QEPAS: quartz enhanced photoacoustic spectroscopy.
Figure 2
Figure 2
Target analyte chemical structures. DMMP: dimethyl methyl phosphonate; DEMP: diethyl methyl phosphonate; TMP: trimethyl phosphonate; DES: diethyl sulfide; DPGME: dipropylene glycol methyl ether.
Figure 3
Figure 3
The injection of the sample into the chamber using a syringe (A) and the hot crucible positioned below the septum, used to facilitate the sample evaporation (B).
Figure 4
Figure 4
The probability density functions of the Gaussian distributions of target analytes. DES: diethyl sulfide; DPGME: dipropylene glycol methyl ether; DMMP: dimethyl methyl phosphonate; TMP: trimethyl phosphonate; DEMP: diethyl methyl phosphonate.
Figure 5
Figure 5
Probability density functions compared with ranges of two times the standard deviation. DES: diethyl sulfide; DPGME: dipropylene glycol methyl ether; DMMP: dimethyl methyl phosphonate; TMP: trimethyl phosphonate; DEMP: diethyl methyl phosphonate.
Figure 6
Figure 6
Infrared spectrum of dimethyl methyl phosphonate.
See this image and copyright information in PMC

References

    1. Chemical Weapons Convention. Convention on the Prohibition of the Development, Production, Stockpiling and Use of Chemical Weapons and on their Destruction . Paris; 1993.
    1. Ganesan K, Raza SK, Vijayaraghavan R. Chemical warfare agents. J Pharm Bioallied Sci. 2010;2:166–178. - PMC - PubMed
    1. Fish JT, Stout RN, Wallace E. Practical Crime Scene Investigations for Hot Zones. 1st ed., vol. 52. Boca Raton (FL): CRC Press; 2010.
    1. World Health Organization (WHO) . Public Health Response to Biological and Chemical Weapons: WHO Guidance. Geneva: WHO; 2004. - PubMed
    1. Kangas MJ, Burks RM, Atwater J, et al. Colourimetric sensor arrays for the detection and identification of chemical weapons and explosives. Crit Rev Anal Chem. 2017;47:138–153. - PMC - PubMed

LinkOut - more resources