Nitrogen dioxide oxidation specificity

Commercially produced amines contain Impurities from synthesis, thus rigid specifications are necessary to avoid unwanted Impurities In final products. Modern-day analytical capability permits detection of minute quantities of Impurities In almost any compound. Detection In parts per million Is routine, parts per billion Is commonplace, and parts per trillion Is attainable. The significance of Impurities In products demands careful and realistic Interpretation. Nltrosatlng species, as well as natural amines, are ubiquitous In the environment. For example, Bassow (1976) cites that about 50 ppb of nitrous oxide and nitrogen dioxide are present In the atmosphere of the cities. Microorganisms In soil and natural water convert ammonia to nitrite. With the potential for nitrosamine formation almost ever-present In the envlronmeit, other approaches to prevention should Include the use of appropriate scavengers as additives In raw materials and finished products. 

The major oxidant in smog is ozone, and early research efforts concentrated on the mechanism of its formation. Attention was focused on the nitrogen oxides, specifically nitrogen dioxide, because it was known... 

Kagawa and Toyama in Tokyo followed 20 normal 11-yr-old school children once a week from June to December 1972 with a battery of pulmonary-function tests. Environmental factors studied included oxidant, ozone, hydrocarbon, nitric oxide, nitrogen dioxide, sulfur dioxide, particles, temperature, and relative humidity. Temperature was found to be the most important environmental factor affecting respiratory tests. The observers noted that pulmonary-function tests of the upper airway were more susceptible to increased temperature than those of the lower airway. Although the effect of temperature was the most marked, ozone concentration was significantly associated with airway resistance and specific airway conductance. Increased ozone concentrations usually occur at the same time as increased temperature, so their relative contributions could not be determined. 

Mixtures of nitrogen dioxide and nitric oxide, nitrosonium tetrafluoro-borate and alkyl nitrites have also been used occasionally in specific situations. 

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]. 

Carbohydrates. Mild oxidants such as chlorine, bromine, or iodine readily convert the aldehyde end groups in the wood polysaccharides to aldonic acid end groups. Nitrogen dioxide selectively converts the primary hydroxyl groups on C-6 in cellulose to carboxyl groups (J3). Periodic acid is a specific oxidant for vicinal diols and yields formaldehyde from primary hydroxyl groups and aldehydes from secondary. 

The value of an atmospheric ozone analyzer is determined almost entirely by its specificity toward ozone. Chemical analytical methods are influenced by the presence of such reducing or oxidizing agents as chlorine, sulfur dioxide, nitrogen dioxide, and peroxides, which are all present in polluted atmospheres. 

The problem of identifying and measuring ozone in the complex gaseous-aerosol mixture which is smog is formidable. There are such gases present as nitric oxide, nitrogen dioxide, sulfur dioxide, hydrocarbon vapors from methane up to probably xylene, plus such partial oxidation products as aldehydes, ketones, and acids. The search for a method of high specificity has been an intensive one. 

In all experiments reported here ozone was determined by the alkaline-potassium iodide method of Smith and Diamond (13) as modified by Byers, Saltzman, and Hyslop (2). The total oxides of nitrogen were determined by the phenoldisulfonic acid method nitrogen dioxide by the specific method of Saltzman (11). The accuracy of the ozone method is still under experimental scrutiny. It is possible that some factorial upward revision of the ozone values reported here may have to be made at a future date. A correction factor of approximately 2 appears probable at this date. The method, however, was the best available at the time these experiments were performed. 

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