Chemiluminescence detectors thermal energy analyzer

Chemiluminescent Detectors (Thermal Energy Analyzers) in Nitrosamine Analysis... 

The oldest chemiluminescent detector was the thermal energy analyzer (TEA), which was specific for N-nitroso compounds. N-nitroso compounds such as nitrosamines are catalytically pyrolyzed and produce nitric oxide which reacts with ozone to produce nitrogen dioxide in the excited ] state, which decays to the ground state with the emission of a photon. A photomultiplier in the reaction chamber measures the emission. Nitrosodi-methylamines have been detected to about 30-40 pg [108]. 

Two other types of element-specific detector for nitrogen currently in use coupled to SFCs are the nitrogen phosphorus detector (NPD) and the thermal energy analyzer (TEA). The NPD uses a hot, catalytically active solid surface immersed in a layer of dissociated H2 and O2 to form electronegative N and P ions which are detected on a nearby electrode [2]. NPD has been shown to have broad application in SFC, especially in the agrochemical industry [3]. The TEA, as described by Fine et al. [4], uses low-temperature pyrolysis, followed by ozone-induced chemiluminescence, for the detection of compounds containing NO2 groups. The TEA has been used for the determination of tobacco-specific nitrosamines and explosives [5]. Both of these detectors require spedlic standards of the analytes of interest for quantitation... 

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). 

TEA, thermal energy analyzer NSD, nitrogen selective detector RCD, redox chemiluminescence detector. 

Because of the very high toxicity of NDMA, sensitive analytical methods (suitable for levels in parts per 10 range) have been developed, all involving GC separation. Various mass spectrometric detection strategies have been employed to overcome the problem of possible direet interferences at the low m/z values employed (moleeular mass of NMDA is 74 Da), as described below. Earlier methods (e.g. BUledeau 1987 Tomkins 1995) used GC with detection by the so-called thermal energy analyzer , which is in fact a GC detector based on a chemiluminescent reaction of ozone with nitric oxide (NO) produced... 

The thermal energy analyzer (TEA) is a specific detector for the measurement of A -nitroso compounds and also responds to nitrosoamines, musk oils, foam blowing agents, and others. The TEA is based on chemiluminescence and was used to detect explosives as early as 1978 (220). The principle of the detector involves... 

The classical nitrosamine analysis was performed for many years by gas chromatography using a thermal energy analyzer (TEA) as detector. This special TEA detector was used due to its selectivity for nitrosamines based on the specific chemiluminescent reaction of ozone with the detector generated NO from nitrosamines. Today, with increased sensitivity requirements, the detection limits of the TEA, and also its complex operation, do not comply any more with the required needs for low detection limits and sample throughput. Mass spectrometric methods have increasingly replaced the TEA. 

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