Rapid On-Site NIR Spectroscopic Characterization of CWA Liquids Using a Novel 3D-Printed Glass Cell

After an incident with suspected use of chemical warfare agents (CWAs) has occurred, fast and reliable detection and identification are pivotal to take the right actions and limit the afflicted damage. Current available methodologies face practical, selectivity, or sensitivity limitations. Near-infrared spectroscopy (NIRS) has been proven to be suitable for on-site analysis in various fields, but it is known to be challenging for the spectral analysis of liquids. The current study introduces a 3D-printed glass liquid cell that overcomes practical limitations of on-site NIR analysis of liquid samples while providing a single-use container for safe sampling and analysis of potentially very toxic compounds. The liquid cell can be implemented for most NIR detectors and is suitable for the analysis, storage, and transport of samples of interest. Validation experiments show that the cell can be manufactured and used in a reproducible manner and has no catalytic effect on sample degradation. The final design is applied to safely record information-rich spectra of several CWAs using two different NIR detectors, a high resolution benchtop laboratory instrument, and a small, rapid, portable device. Recorded spectra contain sufficient compound-specific information to distinguish between different classes of CWAs and different agents within the same class. Results from both instruments are in good agreement and comparable to theoretically predicted spectra and thus show the applicability of NIR spectroscopy to the analysis of CWAs. It is expected that the developed liquid cell is also useful for NIR analysis of liquids in other fields.