Reference method for measuring emissions of nitrogen oxides from stationary sources: chapter 4

4 Interferences

• 4.1 Inorganic nitrates, nitrites or organic nitrogen compounds that are easily oxidized to nitrates interfere with the method and give erroneously high results. The presence of certain reducing agents, for example, sulphur dioxide (SO₂) may interfere by consuming part of the hydrogen peroxide in the absorbing solution to leave an inadequate amount for reaction with the oxides of nitrogen. Halides tend to lower the results, but interference from halide ion (and lead) is negligible in the concentration usually encountered in combustion sources.

• 4.2 The role of some of the constituents of combustion effluents as possible interfering substances has not been thoroughly investigated.