Response of commercial chemiluminescent nitric oxide-nitrogen dioxide analyzers to other nitrogen-containing compounds

Abstract

Commercial chemiluminescent oxides of nitrogen analyzers employing carbon or molybdenum converters are nonspecific for determination of nitrogen dioxide (NO/sub 2/). The instruments not only measure NO/sub 2/, but also simultaneously respond nearly quantitatively to peroxyacetyl nitrate (PAN), and a variety of other organic nitrates and nitrites. Furthermore, they respond nonquantitatively to compounds such as nitroethane and nitric acid. The implications of these observations are not serious for most ambient air analyses where the concentrations of the interfering nitrogenous compounds are low relative to NO/sub 2/ levels. However, for highly quantitative ambient air or smog chamber measurements under circumstances where relatively low concentrations of NO/sub 2/ occur simultaneously with high concentrations of PAN and other nitrogen-containing compounds, corrections for interference by these compounds can be significant. In the absence of such corrections, the NO/sub x/ mode of commercial chemiluminescent analyzers must be viewed to the good approximation as measuring total gas phase ''oxides of nitrogen,'' not simply the sum of NO and NO/sub 2/.