Real-time vapor detection of nitroaromatic explosives by catalytic thermal dissociation blue diode laser cavity ring-down spectroscopy

Abstract

A compact blue diode laser catalytic thermal dissociation cavity ring-down spectrometer (cTD-CRDS) to detect vapors of nitroaromatic explosives is described. The instrument uses heated platinum (IV) oxide catalyst to convert nitroaromatic compounds to NO2, which is detected at 405 nm. Using the relatively volatile nitrobenzene as a test compound, we show by Fourier Transform Infrared Spectroscopy (FTIR) in off-line experiments that nitroaromatics can be quantitatively converted to NO2. The cTD-CRDS detection limit was 0.3 parts-per-billion by volume (pbbv) and sufficiently low to allow the detection of a room temperature sample of 2,4,6trinitrotoluene (TNT) without sample preconcentration. Highlights• A catalytic thermal dissociation converter of nitroaromatics to NO2 was developed.• Catalytic conversion of nitroaromatics to NO2 was shown by FTIR to be quantitative.• A compact blue diode laser cavity ring-down spectrometer (CRDS) was constructed.• The CRDS was equipped with a catalytic converter and a reference channel.• Real-time sensing of 2,4,6-trinitroluene (TNT) by cTD-CRDS was demonstrated.

A gas chromatograph for quantification of peroxycarboxylic nitric anhydrides calibrated by thermal dissociation cavity ring-down spectroscopy

“…the sum" (LRS) algorithm (Everest and Atkinson, 2008;Taha et al, 2013) and at a diode laser pulse repetition rate of 1 kHz.…”

A compact, high-purity source of HONO validated by Fourier Transform Infrared and Thermal Dissociation Cavity Ring-down Spectroscopy

“…Gas streams exiting the HONO sources were analysed using an FTIR spectrometer (Bruker Tensor 27) equipped with a liquid nitrogen cooled mercury cadmium telluride (MCT) detector and a White multi-pass gas cell with a 6.4 m optical path length and an internal volume of 0.75 L (Gemini Scientific Instruments, Venus series) in a similar fashion as described earlier (Taha et al, 2013). Spectra were acquired continuously at a time resolution of 30 s. Background spectra were recorded with HCl inline but with the 110 NaNO2 bypassed, which resulted in the observed spectra showing the change in trace gas concentrations.…”

Advances in explosives analysis—part II: photon and neutron methods

“…Fortunately, NO 2 gas has a strong absorption in the UV from 400-450 nm and NO and N 2 O absorb in the IR (5.26 μm and 4.55 μm, respectively). Gas concentrators [158] and catalytic reactions with platinum (IV) oxide hydrate [160] have been used to detect NO 2 down to the parts-per-billion by volume (ppbv) level. Specifically, catalytic thermal dissociation using platinum oxide hydrate on TNT, 2,4-DNT, and 1,3-DNB to produce NO 2 achieved detection at the 0.5 ppbv level using UV-CRDS without sample preconcentration after only 1 s data acquisition [160].…”

“…Gas concentrators [158] and catalytic reactions with platinum (IV) oxide hydrate [160] have been used to detect NO 2 down to the parts-per-billion by volume (ppbv) level. Specifically, catalytic thermal dissociation using platinum oxide hydrate on TNT, 2,4-DNT, and 1,3-DNB to produce NO 2 achieved detection at the 0.5 ppbv level using UV-CRDS without sample preconcentration after only 1 s data acquisition [160]. Wojtas reported practical application of the preconcentration technique, detecting NO 2 at a LOD of 10-100 ppbv from AN and NG in a Polish mine facility [161].…”