Nitrosamines detection systems

Confirmation of identity of nitrosamines via an independent detection system is desirable since a higher level of confidence is achieved if a different physical property or structural characteristic is measured. Mass spectrometry (MS) has been used... 

The effort required to establish identity of a nitrosamine in an environmental sample depends on the nature of the problem and the specificity of the primary detection system. TEA response is much stronger evidence of identity than response from a flame ionization or nitrogen-specific detector. If TEA response is supported by chemical (9) or ultraviolet photolysis (8) supporting data, identification is adequate for many... 

For instance, the chemotherapeutic drug cyclophosphamide is in most cases immunosuppressive however, it can also induce autoimmunity (Hutchings et al., 1985). Likewise, dimethylnitrosamine, a nitrosamine detected in some foods, has been shown to have both suppressing and enhancing effects on the immune system (Yoshida et al., 1989). 

Richardson et al. [117] have applied gas chromatography with a chemiluminescence detection system to the determination of microgram levels of nitrosamines (N-nitrosodimethylamine, A-nitrosodiethylamine, A-nitroso mo rpho 1 i nc and A-... 

At sufficiently high temperatures, the detector also responds to a variety of nitroaro-matics and to (V-nitrosodimethylamine. NOz yields of 0.70 and 0.90 were obtained for 2,4-DNT and TNT, respectively. The detection system exhibits a linear response for all nitrogen-containing compounds studied, and the detection limit for the determination of organic nitrates was found to be 0.05pmol. The relative response factors for aromatic nitro compounds and nitrosamine for the pyrolyser/luminol detector are presented in Table 3. 

MS is not the only highly sensitive and selective detection system that can be interfaced with GC. For example, consider another compound class of special safety concern as extractables/leachables, A-nitrosamines.f A-Nitrosamines are formed during mixing and vulcanization of certain types of rubber, by the reaction of various secondary amines with nitrosating agents " and can be found at trace levels (ng/g) in components fabricated from these rubbers. 

Singer et al. developed a specific method in which a postcolumn reaction detection system is used for HPLC. This system is useful for those compounds which can be hydrolyzed in a dilute acidic solution to give the nitrite ion. This method involves the use of the Griess reagent in the postcolumn reactor for production of chromophores from A-nitrosamines. The theoretical detection limit for this method was reported to be 0.5 nmol. However, owing to the slow reaction kinetics of some nitroso compounds, this technique requires both an air segmentation system and a high-temperature reactor. 

Richardson et al. [117] have applied gas chromatography with a chemiluminescence detection system to the determination of microgram levels of nitrosamines (N-nitrosodimethylamine, N-nitrosodiethylamine, N-nitrosomorpholine and N-nitrosodiethanolamine, N-nitrosopyrrolid-ine, N-nitrosopiperidine and N-nitroso-5-methyl-l,3-oxazolidine) in potable water supplies. Nitrosamines may be removed from aqueous media by solvent extraction and subsequently concentrated by evaporation of the solvent, in order to detect levels as low as O.Olpg L... 

Metabolic activation systems—such as microsome-, cell-, and host-mediated assays—have been included in mammalian cell mutagenesis systems. Microsome-mediated assays have been used to detect many chemicals, including nitrosamines, polycyclic hydrocarbons, aflatoxins, and vinyl chloride. Cell-mediated assays seem to be a better indicator of in vivo metabolic pathways. Microsome-mediated assays seem suitable for general screening of chemicals, and cell-mediated assays are more valuable in the assessment of data. 

In the analysis of nitroaromatic explosives, TEA is similar to the systems used for nitrosamines except for the fact that temperatures must be higher. Several papers have reported that the temperature of the TEA pyrolysis furnace can affect the selectivity of the detector. A study carried out by Douse [34] to detect traces of several explosives at the low nanogram level revealed that the chromatograms obtained by GC-TEA for both pure compounds and spiked handswabs clearly showed the superior selectivity of TEA in reducing the temperature from 800 to 700°C. Reduction from 700 to 550°C further... 

G. Favaro, G.A. Sacchetto, P. Pastore, M. Fiorani, Liquid chromatographic determination of non-volatile nitrosamines by post-column redox reactions and voltammetric detection at solid electrodes. Study of a flow reactor system based on Ce(IV) reagent, Anal. Chim. Acta 273 (1993) 457. 

Studies in vivo with different A-nitrosamines and their effect on the glutathione levels in hepatocytes reveal that these compounds are inhibitors of the enzymatic mitochondrial activity. " The chemical stmcmre of the A-nitrosamines plays an essential role in the alteration of these hepatic levels, confirming the hepatotoxic activity developing these compounds in the organism. On the other hand, teratogenic effects caused by the activity of A-nitrosamines have been detected, particularly at the level of the central nervous system. ... 

In retrospect, the development and standardization of S-9 has centered around a limited number of chemical types, i.e., iV-nitrosamines, aromatic amines, and polycyclics. Accordingly, the ability of microbial systems supplemented with S-9 to detect these chemicals has been rather consistent. However, the converse also appears true chemicals, other than those types with which the testing has been standardized, that are metabolized in vivo to their active forms are not as consistently detected in such in vitro testing. While further discussion of this point is reserved for later, suffice it here to note that, in general, poorly activated types include azonaphthol dyes carbamyl and thiocarbamyl compounds phenyls polyhalogenated aromatics, cyclics, and aliphatics benzodioxoles and symmetrical hydrazines. 

Therefore, to increase the spectrum of compounds that can be studied in the cell-mediated mutagenesis system, Langenbach et al. have used primary cultures of rat liver cells to activate two known classes of liver carcinogens (nitrosamines and aflatoxins), and V79 cells to detect their mutagenic metabolites. A schematic diagram summarising the procedure and technique is shown in Fig. 2. Conversion from ouabain susceptibility to ouabain resistance, a mutation associated with the surface member Na /K ATPase, was used as the genetic marker. Typical data obtained with several nitrosamines and aflatoxins are summarised in Table 5. 

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