Nitrosamine detectors

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. 

Confirmation of the identities of nitrosamines generally is accompHshed by gas chromatography—mass spectrometry (gc/ms) (46,87). High resolution gc/ms, as well as gc/ms in various single-ion modes, can be used as specific detectors, especially when screening for particular nitrosamines (87) (see Analytical LffiTHODS Trace and residue analysis). 

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. 

Morristown, NJ) for the ion source. No carrier gas separator was used. For determination of nitrosamines and TBDMS derivatives of hydroxy-nitrosamines, columns and operating conditions were identical to those for GC-TEA analyses For most work, the He flow rate was 15 cc/min and the column effluent was split 1 1 between a flame ionization detector and the mass spectrometer. The stainless steel splitter, solvent vent valve (Carle Instruments, Fullerton, CA), and associated plumbing were... 

Radioisotope-labeled nitrosamines have proven valuable in development of analytical methods and for demonstrating efficiency of recovery of nitrosamines from tobacco products and smoke (37-39). The very high specific activity required for low part-per-billion determinations has discouraged most analysts from using this approach. Unless a radiochromatographic detector with adequate sensitivity is available, samples must be counted independently of the final chromatographic determination, and one of the advantages of internal standardization, correction for variation in volume injected, is lost. 

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... 

The NO + 03 chemiluminescent reaction [Reactions (1-3)] is utilized in two commercially available GC detectors, the TEA detector, manufactured by Thermal Electric Corporation (Saddle Brook, NJ), and two nitrogen-selective detectors, manufactured by Thermal Electric Corporation and Antek Instruments, respectively. The TEA detector provides a highly sensitive and selective means of analyzing samples for A-nitrosamines, many of which are known carcinogens. These compounds can be found in such diverse matrices as foods, cosmetics, tobacco products, and environmental samples of soil and water. The TEA detector can also be used to quantify nitroaromatics. This class of compounds includes many explosives and various reactive intermediates used in the chemical industry [121]. Several nitroaromatics are known carcinogens, and are found as environmental contaminants. They have been repeatedly identified in organic aerosol particles, formed from the reaction of polycyclic aromatic hydrocarbons with atmospheric nitric acid at the particle surface [122-124], The TEA detector is extremely selective, which aids analyses in complex matrices, but also severely limits the number of potential applications for the detector [125-127],... 

Volatile nitroso compounds were determined in hams processed in elastic rubber nettings by SPE and GC-CLD577. By a similar method A-n i tro sodi ben zy lamine (278b), a semivolatile nitrosamine, was determined in these products by SPE followed by GC interfaced to a nitrosamine-specific TEA-CLD detector the coefficient of variation was 10.6% at the 2.1 ppb level578. The nitrosamines detected in ham most likely originate from the amine precursors in rubber and from the nitrite commonly used in the meat curing process. 

The diffusion-limited electrochemical oxidation of V-nitrosamines in an aqueous pH 1.5 buffer was demonstrated at a GCE coated with a film of mixed valence ruthenium oxides, stabilized by cyano crosslinks. This electrode was used in a potentiostatic amperometric detector for FIA and HPLC, to allow the determination of representative N-nitrosamines (278a, 278c and 278d) for 278c, LOD was 10 nM and RSD 2% at 0.80 pM... 

Because N-nitroso compounds can have such a wide variety of physical and chemical properties, and because they can be formed from a wide variety of precursors. analysis at the trace level is difficult. The most widely used technique is the use of a nitrosamine specific detector, called a TEA, which can be interfaced to either a gas chromatograph (GC) or a high pressure liquid chromatograph (HPLC) (31,32). General screening procedures which have been designed to detect all N-nitroso compounds have been developed (33,34). Structural confirmation of N-nitroso compounds is gen-... 

V-Nitrosodiethanolamine has been found in many complex matrices such as cutting and grinding fluids and cosmetics. Analysis for V-nitrosodiethanolamine is complicated by the matrix and a clean-up technique with derivatization is typically required before quantitation of the analyte to achieve adequate sensitivity and selectivity. Ammonium sulfamate may be added to the sample to prevent the artifactual formation ofV-nitrosamines. Derivatives of V-nitrosodiethanolamine have been prepared by acylation, trifluoroacylation, trimethylsilylation and methylation. The derivatives have been analysed by gas chromatography using flame ionization and mass spectro-metric detectors (Occupational Safety and Health Administration, 1990). 

The GC-TEA conditions used for the detection of volatile nitrosamines have been described by Fine and Rounbehler (8). A 14 x 1/8" stainless steel column packed with 5% Carbowax 20M containing 2% NaOH on Chromosorb W HP (80-100 mesh) was operated at 175°C with argon gas as the carrier at a flow rate of 15 mL/min. A TEA was used as the detector with dry ice/ethanol as the cold trap. The HPLC-TEA was constructed by sequentially connecting a high pressure pump (Altex, model 110), an injector (Waters, model U6K), a yPorasil column (Waters), and a TEA. The operation of HPLC-TEA has been described by Fine, et al.( ). 

U.S. EPA Method TO7 describes the determination of N-nitrosodimethylamine in ambient air (U.S. EPA, 1986). The method is similar to the NIOSH method discussed above and uses Thermosorb/N as adsorbent. The air flow is 2 L/min and the sample volume recommended is 300 L air. The analyte is desorbed with methylene chloride and determined by GC/MS or an alternate selective GC system, such as TEA, HECD, or thermoionic nitrogen-selective detector. The latter detector and the TEA are more sensitive and selective than the other detectors. Therefore, the interference from other substances is minimal. Other nitrosamines in air may be determined in the same way. 

Highly selective to compounds containing nitrogen and phosphorus Nitrogen-phosphorus detector Organophosphorus pesticides (EPA 8141) Acrylonitrile (EPA 8031) Acetonitrile (EPA 8033) Nitrosamines (EPA 8070) Hydrocarbons, fats, oils, waxes may interfere with organophosphorus pesticides. 

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]. 

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... 

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. 

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