History shows that chemical warfare agents (CWAs) are the most widely proliferated and used weapon of mass destruction (WMDs). Unlike ultrapure laboratory grade chemicals, munitions grade CWAs used in these attacks are likely to contain impurities from the storage container, degradation, or unreacted precursors. All of which often cause fluorescence when analyzed using 785 nm-based Raman analyzers. In order to minimize fluorescence in these types of real-world threats, the Rigaku portfolio of handheld Raman analyzers uses a longer wavelength laser at 1064 nm, which leads to more reliable identifications and shorter measurement times.
To demonstrate the capabilities of 1064 nm Raman to identify real-world threats, spectra of munitions grade CWAs were collected using a Rigaku 1064 nm Raman analyzer under secure conditions at Edgewood Chemical and Biological Center (Roy et al. 2015). These spectra were compared to library spectra of pure agent (examples shown in Figures 1-2). The high correlation between munitions grade spectra and library spectra indicate that matching algorithms confidently ID the threat.
Figures 1 & 2. Pure (blue) and munitions grade (red) spectra of sarin (GB), and soman (GB), collected with 1064 nm laser excitation.
The fluorescence reduction of 1064 nm Raman compared to 785 nm was demonstrated in the sample study where spectra of munitions grade compounds in the examples shown in Figures 3 and 4. The Raman signatures were clearly visible for spectra collected on a Rigaku Raman analyzer with a 1064 nm laser excitation versus the 785 nm-based system.
Figures 3 & 4. Raman spectra of muitions grade sarin (GB) and soman (GD) collected at 785 nm (red) and 1064 nm (blue).
The handheld Rigaku portfolio of 1064 nm Raman analyzers has the ability to detect and identify both pure and munitions grade G Series nerve agents. In addition, this study shows significantly less fluorescence interference than the spectra generated with a traditional 785 nm Raman. The military and first responders can expect shorter measurement times and the ability to measure a wider range of real-world compounds.