Method and apparatus for nitrogen oxide analysis

Abstract

A method and apparatus for the chemiluminescent determination of NO/NO.sub.x in a sample gas is disclosed in which the NO.sub.x portion of the gas stream is catalytically converted in a preconditioned vitreous carbon bed at a relatively low temperature effective to catalytically convert NO.sub.x to NO and below 200.degree. C. The vitreous carbon is preconditioned by heating at a temperature of between 300.degree. C. and about 500.degree. C. for a sufficient period of time, on the order of two to five hours. The apparatus consists of a converter containing the preconditioned vitreous carbon in communication with a reaction cell consisting of a hollow cylindrical housing having an open end closed by an optical filter. A suitable photodetecter is disposed to detect light emitted through the optical filter. A chemiluminescent reaction between ozone and NO in the sample stream occurs in a reaction chamber defined by the interior of the housing. A reflector element may be disposed in the reaction chamber. The converter and the housing are preferably formed of low cost, easily worked materials, such as stainless steel or aluminum.

Dependencies are inferred from the claim text.