Thermal energy analysis detection

J. M. F. Douse, Dynamic Headspace Method for the Improved Clean-up of Gunshot Residues prior to the Detection of Nitroglycerine by Capillary Column Gas Chromatography with Thermal Energy Analysis Detection, Journal of Chromatography 464 (1989) 178. 

J.M.P. Douse, Trace analysis of explosives at the low nanogram level in handswab extracts using columns of Amberlite XAD-7 porous polymer beads and sdica capillary column gas chromatography with thermal energy analysis and electron capture detection , J. Chromatogr., 328 (1985) 155-165. 

The prototype of the tobacco specific nitrosamines, NNN, has been detected in both tobacco smoke and unburned tobacco. Various analytical methods have been used including gas chromatography (GLC) (13,14,15,16) combined GLC-mass spectrometry (17), thin layer chromatography (18) high pressure liquid chromatography (HPLC) (19,20), and combined HPLC-thermal energy analysis (21). 

Volatile and gaseous products of propellant combustion remain inside the gun barrel and cartridge case for some time and their detection and quantitative determination by means of gas and liquid chromatographic methods (thermal desorption GC-MS, GC-thermal energy analysis, LC-MS/MS) can help in establishing, whether the gun was fired up to 3 days, 2-3 weeks or more than 3 weeks before examination [19, 20]. 

Where the target analyte contains heteroatoms such as nitrogen, phosphorus and sulfur, atom-selective detectors can provide an ideal detection method. A number of examples appear in the literature of the use of a detector called a thermal energy analyser (TEA) for the measurement of A-nitroso compounds [14-17] and aromatic nitro compounds [18]. This has also been used as an HPLC detector [19, 20], and a modified TEA has been reported to be useful for analysis of amines and other nitrogen-containing compounds [17]. Unfortunately, this technique appears not to have gained in popularity, since no reports have appeared in the literature for over two decades. 

Nitrosamines (Method 607). The nitrosamines are extracted with methylene chloride, treated with HC1, concentrated, and solvent exchanged to methanol for direct nitrogen-phosphorus or thermal energy analyzer (TEA) detection. Provision is made for Florisil or aluminum oxide column cleanup prior to GC analysis. The GC column liquid phase is 10 Carbowax 20 M plus 2 KOH. N-Nitrosodiphenylamine thermally degrades to diphenylamine in the GC and is measured as diphenylamine after prior removal of any diphenylamine occurring, as... 

Differential thermal analysis, then — which should perhaps be more properly called differential temperature analysis — is capable of detecting the release or absorption of thermal energy, the temperature range within which such changes take place, and, if properly carried out, the number of thermal reactions occurring. 

A sensitive and selective chemiluminescent detector that has made an appreciable impact on the analysis of nitrosamines in environmental samples in the last several years is the thermal energy analyzer or (TEA) (15-19). This detector utilizes an initial pyrolysis reaction that cleaves nitrosamines at the N-NO bond to produce nitric oxide. Although earlier instrumentation involved the use of a catalytic pyrolysis chamber (15,17,19), in current instruments, pyrolysis takes place in a heated quartz tube without a catalyst (20). The nitric oxide is then detected by its chemiluminescent ion react with ozone. The sequence of reactions can be depicted in Figure 1. A schematic of the TEA is shown in Figure 2 (17). Samples are introduced into the pyrolysis chamber by direct injection or by interfacing the detector with a gas chromatograph (15,17,21,22) or a liquid chromatograph (22-25). 

Various GC methods have also been developed for the determination of nitrate, but the ions must be derivatized to achieve suitable volatility before GC analysis. Nitrate is commonly determined as nitrobenzene, which can be detected with an electron-capture detector or a thermal energy analyzer at levels of 0.05 or O.lpgmH, respectively. 

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