Rapid Continuous Determination of Nitric Oxide Concentration in Exhaust Gases

Abstract

The rapid determination of nitric oxide levels in exhaust gases is required both for laboratory studies of the exhaust emission characteristics of combustion engines and for routine inspection of motor vehicle exhaust. A continuous sampling, continuous analysis method for measuring nitric oxide has been demonstrated. Rapid oxidation of nitric oxide to nitrogen dioxide is obtained through ozonization. Nitrogen dioxide concentrations are determined by means of an ultraviolet absorption technique. Nitric oxide concentrations between 100 and 5000 ppm have been measured and response time of about 20 seconds obtained. The presence of unburned hydrocarbons in the exhaust sample has an adverse effect on the results of this technique which requires either the removal of hydrocarbons or adjustment of ozone concentration.