Non-contact detection of chemical warfare simulant triethyl phosphate using PM-IRRAS
Department of Chemistry, University of Guelph, Guelph, Ontario, Canada.Analytica chimica acta (Impact Factor: 4.51). 08/2012; 737:45-54. DOI: 10.1016/j.aca.2012.05.059
Polarization modulation-infrared reflection absorption spectroscopy (PM-IRRAS) was employed to detect the chemical warfare agent (CWA) simulant triethyl phosphate (TEP) on gold, as well as on US military paint, i.e., chemical agent resistant coating (CARC). The targeted CWAs (G and V-series nerve agents) are characterized by phosphoric group vibrations present in the 1200 cm(-1) region. TEP displays two prominent peaks at 1268 cm(-1) and 1036 cm(-1) corresponding to P=O and (P)-O-C vibrations, respectively. A droplet of TEP solution in cyclohexane was deposited on gold and CARC substrates and after solvent evaporation PM-IRRAS spectra were collected in the 1200 cm(-1) region. The integrated peak area of the PO and (P)OC vibrations was used to construct calibration curves and to determine the experimental limit of detection (LoD). In the case of gold as the substrate the estimated LoD of ~0.48 μg and 1.23 μg was obtained for the P=O and (P)-O-C vibrations, respectively. In the case of CARC, a LoD of 24 μg was determined. These detection limits are at least 3 orders of magnitude lower than the typical lethal dose of G and V-series nerve agents, demonstrating potential of PM-IRRAS for non-contact detection of these CWAs.
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ABSTRACT: Polarization modulation–infrared reflection absorption spectroscopy (PM-IRRAS) was employed to analyze two unique samples: (1) an industrially prepared alkoxysilane-pretreated aluminum alloy (AA6111) in the absence and presence of a ∼600-nm-thick lubricant coating and (2) a chemical warfare agent simulant, triethyl phosphate (TEP), on glass. For the pretreated aluminum samples, PM-IRRAS spectra were analyzed for three distinct regions; the SiO stretching vibration around 1120 cm−1, the NH2 bending mode at ∼1600 cm−1 and the CH stretching region around 2900 cm−1. Our results showed that increasing the curing temperature (from 55 to 100 °C) improved the overall extent of cross-linking within the siloxane network. In addition, the spectra of lubricant (top coating) and the underlying siloxane layer for the aluminum samples with lubricant were collected for the same sample. Our results show that the nature of the siloxane film remains intact and unaltered after deposition of the lubricant top-coat. For detection of TEP on glass, the band at 1268 cm−1, corresponding to the P═O vibration, was monitored. A droplet of TEP solution in dichloromethane was deposited on glass. After solvent evaporation had occurred, the intensity of the P═O vibration band was used to construct calibration curves to determine the experimental limit of detection, which was found to be ∼200 μg for TEP on glass. Figure Schematic of a akoxysilane network and PM-IRRAS spectrum of the alkoxysilane film at aluminum surface
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ABSTRACT: In order to detect contaminants on surface, a method for surface contamination detection was developed based on multi-angle infrared differential absorption spectra. As contaminants' absorption ability varied with measurement angles, the spectral features of contaminants could be extracted from multi-angle observations. Firstly, multi-angle measurement model of chemical contaminants was introduced. Then three typical compounds: poly (dimethylsiloxane), triethyl phosphate and methyl salicylate were measured both in laboratory and field on different substrates. The results showed that, with multi-angle infrared differential absorption spectra, this method could extract directly spectral features of contaminants both in laboratory and field on typical surfaces, and spectral features of contaminants got more distinct with more smooth substrate and larger difference between two incidence angles employed. This method had application potential in immediate responding for chemical contaminants detection.
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