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Generating highly specific spectra and identifying thermal decomposition products via Gas Chromatography / Vacuum Ultraviolet Spectroscopy (GC/VUV): Application to nitrate ester explosives
摘要： Gas chromatography/mass spectrometry (GC/MS) is a "workhorse" instrument for chemical analysis, but it can be limited in its ability to differentiate structurally similar compounds. The coupling of GC to vacuum ultraviolet (VUV) spectroscopy is a recently developed technique with the potential for increased detection specificity. To date, GC/VUV has been demonstrated in the analysis of volatile organic compounds, petroleum products, aroma compounds, pharmaceuticals, illegal drugs, and lipids. This paper is the first to report on the utility of GC/VUV for explosives analysis in general, and the first to report on thermal degradation within the VUV cell and its analytical utility. The general figures of merit and performance of GC/VUV were evaluated with authentic standards of nitrate ester explosives (e.g., nitroglycerine (NG), ethylene glycol dinitrate (EGDN), pentaerythritol tetranitrate (PETN), and erythritol tetranitrate (ETN)). In addition, the explosive analytes were thermally degraded in the VUV cell, yielding reproducible, complex and characteristic mixtures of gas phase products (e.g., nitric oxide, carbon monoxide, and formaldehyde). The relative amounts of the degradation products were estimated via spectral subtraction of library spectra. Lastly, GC/VUV was used to analyze milligram quantities of intact and burned samples of double-base smokeless powders containing nitroglycerine, diphenylamine, ethyl centralite, and dibutylphthalate.
关键词： Thermal degradation,Nitrate ester explosives,Vacuum ultraviolet spectroscopy,Gas chromatography
更新于2025-09-04 15:30:14
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Preparation and characterization of a novel nanocomposite coating based on sol-gel titania/hydroxyapatite for solid-phase microextraction
摘要： In this work a novel nanocomposite coating with high thermal stability and high durability is prepared. The surface of the stainless steel as a support was initially modified by (3–mercaptopropyl)trimethoxysilane. Surface characteristics of pure titania (TiO2), pure hydroxyapatite (HAP) and Hap/TiO2 nanocomposite coating were investigated and compared by energy dispersive X–ray (EDX) spectroscopy as well as by field emission–scanning electron microscopy (FESEM). The mutual effects of components on each other were discussed. Addition of HAP sol to the pure TiO2 sol, considerably changes the coating morphology. The applicability of the sol–gel HAP/TiO2 fiber was assessed for the headspace solid–phase microextraction (HS–SPME) of benzene, toluene, ethylbenzene and xylenes (BTEXs) from water sample followed by gas chromatography–mass spectrometry (GC–MS). Important parameters affecting the extraction efficiency were investigated. The efficiency of HAP/TiO2 nanocomposite coating was compared with other reported fibers and showed very good results. Under optimal conditions, the detection limits (S/N = 3) were in the range of 0.04 to 1 μg L?1, and the limits of quantification (S/N = 10) were between 0.1 and 4 μg L?1. The relative standard deviations (RSDs) for each fiber (at 20 μg L?1 and n = 5) were in the range of 1.76 to 8.18%, while the RSDs between fibers were 3.03 to 10.02%. The method showed a large linearity in the range from 0.1 to 1000 μg L?1 with correlation coefficients of > 0.995.
关键词： Gas chromatography–mass spectrometry,BTEX,Hydroxyapatite,Solid-phase microextraction,Sol–gel technology,Titania
更新于2025-09-04 15:30:14