Explosives in forensic science using benchtop ARL EQUINOX 100 X-ray Diffractometer

Significance of the Topic

Efficient and accurate analysis of explosive materials is a critical component of forensic investigations and counterterrorism efforts. Improving detection methods is essential due to the persistent threat of improvised explosive devices (IEDs) in both law enforcement and military contexts.

Objectives and Overview

This application note evaluates the performance of the benchtop Thermo Scientific ARL EQUINOX 100 X-ray diffractometer for rapid identification and quantification of explosive substances.
The study aims to:

• Demonstrate qualitative and quantitative phase analysis of various explosives.
• Assess instrument portability and suitability for field deployment.
• Highlight the ability to identify minor components and contaminants.

Methodology

Samples were provided by law enforcement authorities. Measurements were performed in reflection geometry using Cu Kα radiation with a 5 to 10 minute acquisition time. Data processing involved MDI JADE 2010 and the ICDD pdf4 Organics database. Quantification of crystalline and amorphous fractions was achieved through WPF Rietveld refinement.

Instrumentation Used

• ARL EQUINOX 100 benchtop X-ray diffractometer with curved position sensitive detector
• 50 W micro-focus X-ray tube (Cu or Mo) or 15 W Co tube with mirror optics
• Battery-capable, no external water chiller required
• Software: MDI JADE 2010, ICDD pdf4 Organics database

Main Results and Discussion

• Ammonium Nitrate sample: Predominantly polymorph 4 with minor polymorph 2 and traces of TATB.
• Sodium Chlorate mixture: Contains approximately 80% amorphous binder (PEG) and minor cobalt hydroxide, alongside the crystalline sodium chlorate.
• TNT sample: Identified TNT matrix with trace amounts of triethylaminium picrate and octogen.

These results demonstrate the instrument’s capability to detect both major and trace phases in complex explosive formulations.

Benefits and Practical Applications

• Rapid analysis (5–10 minutes) enables timely forensic decision-making.
• Portable design facilitates deployment in mobile or field laboratories.
• High sensitivity to crystalline and amorphous phases supports comprehensive mixture characterization.

Future Trends and Potential Applications

Advancements in detector technology and data analysis algorithms may further reduce measurement times and improve phase discrimination. Integration with automated sampling systems could enable continuous monitoring in high-threat environments. Expansion of reference databases will enhance identification of novel or improvised explosive mixtures.

Conclusion

The ARL EQUINOX 100 bench-top XRD provides a robust and efficient tool for forensic explosives analysis. Its rapid data acquisition, portability, and precise phase quantification make it well-suited for both laboratory and field operations.

References

• Welzmiller, S., Pilliere, H. Application Note AN41129: Explosives in Forensic Science Using Benchtop ARL EQUINOX 100 X-ray Diffractometer. Thermo Fisher Scientific, 2021.