Generating highly specific spectra and identifying thermal decomposition products via Gas Chromatography / Vacuum Ultraviolet Spectroscopy (GC/VUV): Application to nitrate ester explosives
Abstract: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… Show more
“…2). 26 Figure 1.(a) VUV spectra of nitrate ester explosives exhibiting fine structure at 300 ℃. (b) Thermal decomposition of nitroglycerine across the temperature range 200 ℃ (intact) to 300 ℃ (complete decomposition).Figure 2.Thermal decomposition products of nitrate ester explosives.…”
Section: Resultsmentioning
confidence: 99%
“…Gas chromatography-vacuum ultraviolet (GC-VUV) has since been utilized to study fatty acids, [2][3][4][5][6] hydrocarbons, [7][8][9][10][11][12][13] pesticides, [14][15][16][17][18] flavors, [19][20][21] fragrances, 19 drugs, [22][23][24][25] and explosives. 23,26 There has been little to no investigation into the performance of a benchtop GC-VUV in comparison to synchrotron facilities and no investigation in comparison to other instrumentation that acquire data in this wavelength range. 1 This will be investigated here in an effort to further establish the benchtop GC-VUV as comparable to previously utilized techniques.…”
Section: Introductionmentioning
confidence: 99%
“…17,[27][28][29] Previous analysis of nitrate ester explosives such as ethylene glycol dinitrate (EGDN), nitroglycerine (NG), and pentaerythritol tetranitrate (PETN) at temperatures exceeding 240 C revealed various decomposition products such as nitric oxide, water, carbon monoxide, oxygen, and formaldehyde. 26,30 These decomposition products were determined via the VUV spectral database. 31 The spectra of the decomposition products exhibited highly specific fine structure that has not been observed in the VUV spectra of the intact explosives; thus, suggesting vibronic (transitions in the electronic and vibrational energy levels) or Rydberg transitions (high energy excitation beyond the valence shell).…”
“…2). 26 Figure 1.(a) VUV spectra of nitrate ester explosives exhibiting fine structure at 300 ℃. (b) Thermal decomposition of nitroglycerine across the temperature range 200 ℃ (intact) to 300 ℃ (complete decomposition).Figure 2.Thermal decomposition products of nitrate ester explosives.…”
Section: Resultsmentioning
confidence: 99%
“…Gas chromatography-vacuum ultraviolet (GC-VUV) has since been utilized to study fatty acids, [2][3][4][5][6] hydrocarbons, [7][8][9][10][11][12][13] pesticides, [14][15][16][17][18] flavors, [19][20][21] fragrances, 19 drugs, [22][23][24][25] and explosives. 23,26 There has been little to no investigation into the performance of a benchtop GC-VUV in comparison to synchrotron facilities and no investigation in comparison to other instrumentation that acquire data in this wavelength range. 1 This will be investigated here in an effort to further establish the benchtop GC-VUV as comparable to previously utilized techniques.…”
Section: Introductionmentioning
confidence: 99%
“…17,[27][28][29] Previous analysis of nitrate ester explosives such as ethylene glycol dinitrate (EGDN), nitroglycerine (NG), and pentaerythritol tetranitrate (PETN) at temperatures exceeding 240 C revealed various decomposition products such as nitric oxide, water, carbon monoxide, oxygen, and formaldehyde. 26,30 These decomposition products were determined via the VUV spectral database. 31 The spectra of the decomposition products exhibited highly specific fine structure that has not been observed in the VUV spectra of the intact explosives; thus, suggesting vibronic (transitions in the electronic and vibrational energy levels) or Rydberg transitions (high energy excitation beyond the valence shell).…”
“…VUV has also been used in tandem with MS. [9] VUV has shown the ability to differentiate fatty acid methyl esters, pesticides, fuels, and more. [1,[10][11][12][13][14][15][16][17][18] VUV has been demonstrated to be able to differentiate 67 designer drugs. [10,[19][20][21].…”
The vacuum ultraviolet region includes wavelengths shorter than 200 nm. Electronic transitions of sigma and pi bonds lie in this region, which have the potential to yield structural information. Thus, a VUV detector should be able to detect nearly any molecule analyzable by gas chromatography. This study sought to determine the extent to which structurally similar phenethylamines are differentiated using their VUV spectra. Phenethylamines are a common drug class including pseudoephedrine and illicit drugs such as methamphetamine. Several phenethylamines are difficult to analyze by electron impact mass spectrometry due to their fragmentation giving the same mass to charge ratio fragments at similar ratios. While phenethylamines are generally differentiable by retention time, an extra layer of specificity is preferred in forensic analyses. A Vacuum Ultraviolet (VUV) spectrophotometer coupled to a gas chromatograph was used to collect VUV spectra at high frequency between 125-430 nm. Eight phenethylamines were analyzed for this work using GC/VUV. A calibration curve and limit of detection study was performed that indicates a limit of detection around 10 μg mL-1 and an upper limit of linearity around 1000 μg mL-1. The spectra, analyzed by Principal Component Analysis and Discriminant Analysis, indicate the ability to reliably differentiate each of the drugs from one another including structural isomers and diastereomers. Lastly, five "street" samples containing amphetamines were analyzed to demonstrate "real world" performance.
“…Recently, a new bench-top vacuum ultraviolet (VUV) spectroscopic detector has been developed for gas chromatography applications. 1,2 It has been applied successfully in a variety of applications areas, including pesticide, 3 fragrance, 4 fatty acid, 5,6 permanent gas, 7 petrochemical, 8–13 forensic, 14–16 and environmental analysis. 17 Compared with other electron absorption instrumentation, the VUV detector has several notable advantages.…”
The advent of a new vacuum ultraviolet (VUV) spectroscopic absorption detector for gas chromatography has enabled applications in many areas. Theoretical simulations of VUV spectra using computational chemistry can aid the new technique in situations where experimental spectra are unavailable. In this study, VUV spectral simulations of paraffin, isoparaffin, olefin, naphthene, and aromatic (PIONA) compounds using time-dependent density functional theory (TDDFT) methods were investigated. Important factors for the simulations, such as functionals/basis sets and formalism of oscillator strength calculations, were examined and parameters for future PIONA compound simulations were obtained by fitting computational results to experimental spectra. The simulations produced satisfactory correlations between experimental observations and theoretical calculations, and enabled potential analysis applications for complex higher distillate fuels, such as diesel fuel. Further improvement of the methods was proposed.
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