Nitrosamines thermal energy analyzer

The data in Table I are also significant in terms of the type of analysis to determine the presence of NDMA. In all cases analysis was done using gas chromatography coupled with a Thermal Energy Analyzer, a sensitive, relatively specific nitrosamine detector (12). Further, in six of the studies, the presence of NDMA in several samples was confirmed by gas chromatography-mass spectrometry (GC-MS). The mass spectral data firmly established the presence of NDMA in the beer samples. 

Reliable analytical methods are available for determination of many volatile nitrosamines at concentrations of 0.1 to 10 ppb in a variety of environmental and biological samples. Most methods employ distillation, extraction, an optional cleanup step, concentration, and final separation by gas chromatography (GC). Use of the highly specific Thermal Energy Analyzer (TEA) as a GC detector affords simplification of sample handling and cleanup without sacrifice of selectivity or sensitivity. Mass spectrometry (MS) is usually employed to confirm the identity of nitrosamines. Utilization of the mass spectrometer s capability to provide quantitative data affords additional confirmatory evidence and quantitative confirmation should be a required criterion of environmental sample analysis. Artifactual formation of nitrosamines continues to be a problem, especially at low levels (0.1 to 1 ppb), and precautions must be taken, such as addition of sulfamic acid or other nitrosation inhibitors. The efficacy of measures for prevention of artifactual nitrosamine formation should be evaluated in each type of sample examined. 

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... 

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]. 

Based on animal studies, A-nitrosamines are compounds with proven carcinogenic effect. The search for sources and reduction of human exposure to their action is now one of the most important research problems. Currently, a major problem is the presence of A-nitrosamines and their precursors in food. Determination of A-nitrosamines in food relies on isolating these compounds by vacuum distillation in a basic medium, in the presence of liquid paraffin, followed by extraction with dichloromethane, pre-concentration of the sample, and analysis using GC. A thermal energy analyzer coupled to a gas chromatograph can serve as an efficient detector for these compounds. 

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... 

The choice of detector is critical to the specific types of chemicals to be analyzed. Some units will detect everything and the output will resemble noise some will detect only certain types of chemicals. The latter type is preferred, and in the case of nitrosamines, the thermal energy analyzer/detector is the method of choice. Because smoke condensate is filthy, the cheaper, packed column is invariably used. Generally it gives adequate separation of the nitrosamines. 

To convert chemically bound nitrogen to nitric oxide, the sample is submitted to oxidative pyrolysis. As the light emission occurs, light intensity is measured by a photomultiplier tube through a band pass filter. Application thermal energy analyzer (TEA) for nitrosamines. 

Adams, J.D., K.D. Brunnemann, and D. Hoffmann Chemical studies on tobacco smoke. LXXV. Rapid method for the analysis of tobacco-specific A-nitrosamines by gas-liquid chromatography with a thermal energy analyzer J. Chromatography 256 (1983) 347-351. 

Sen, N.P. and S. Seaman Gas-liquid chromatographic-thermal energy analyzer determination of A-nitrosodimethylamine in beer at low parts per billion level J. Assoc. Off. Anal. Chem. 64 (1981) 933-938. Sen, N.P. and S. Seaman Volatile A-nitrosamines in dried foods J. Assoc. Off. Anal. Chem. 64 (1981) 1238-1242. 

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

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). 

It was initially reported by Fan et al in 1976 that four of seven herbicides purchased in retail outlets had contained measurable concentrations of nitrosamines as detected with a thermal energy analyzer (43). Three of the herbicides consisted... 

The determination of volatile nitrosamines in crops and soils treated with dinitroaniline herbicides was reported by West and Day (47). Measurement was accomplished by means of a gas chromatograph-thermal energy analyzer. The sensitivity of the methods was 0.2, 0.05 and 0.01 ppb for dipropylnitrosamine in crops, soil and water respectively. 

N-nitrosamines generated at low levels from secondary amines liberated from some of the accelerators can cause health concerns and have been subject to regulation. Volatile N-nitrosamines are quantified using GC with a thermal energy analyzer. 

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. 

Al-Nitrosamines are potent animal carcinogens which may be present at trace levels in many products. Since the development of the thermal energy analyzer made their detection a relatively simple matter, it has become routine to specify that commercial products be free of these compounds. This is particularly true in cosmetic raw materials, most im-... 

In the United States, it is more common to use the product synthesis chemistry to predict which nitrosamines might logically be present, then determine these by specific methods. The methods normally used are GC with MS or thermal energy analyzer detection or HPLC with thermal energy analyzer detection. The pitfall in this approach is that nitrosamines can be present from unexpected sources such as contaminants or trace additives. Such nitrosamines will probably only be detected by the nonspecific methodology. 

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