Continuous Mass Spectrometric Determination of Nitric Oxide in Automotive Exhaust

Three techniques for the measurement of the oxides of nitrogen in automotive exhaust were evaluated. These included a “nitrous fume” analyzer, a gaseous NO₂ colorimeter, and a movable mass spectrometer. All data obtained were compared to data from currently accepted wet chemical methods, the phenoldisulfonic acid and the “modified” Saltzman.

Of the techniques evaluated, the mass spectrometer analysis of NO has been found to be the most useful for the study of nitrogen oxides in engine exhaust. The high cost of wet chemical analysis has indicated a need for an improved and continuous analytical method. The mass spectrometer approach measures NO within seconds of its discharge, thus minimizing any reactions prior to measurement.