Abstract: The present invention relates to an apparatus and method for determining the concentration of nitric oxide (NO) in a gas mixture such as air. The gas sample containing NO is mixed with a gas containing ozone (O3), and the change in the ozone concentration is measured after a sufficient time is allowed for the reaction between NO and O3 to take place and destroy a measurable quantity of O3. In the disclosed embodiment, the concentration of ozone is measured using the technique of UV absorption. In this case, the invention has the advantage over other instruments for measuring NO of having absolute calibration based on the known extinction coefficient for ozone at ultraviolet wavelengths. The invention discloses both static and dynamic flow systems, and the NO concentration measurements may be made over a wide pressure range.

Abstract: The present invention relates to an apparatus and method for determining the concentration of nitric oxide (NO) in a gas mixture such as air. The gas sample containing NO is mixed with a gas containing ozone (O3), and the change in the ozone concentration is measured after a sufficient time is allowed for the reaction between NO and O3 to take place and destroy a measurable quantity of O3. In the preferred embodiment, the concentration of ozone is measured using the technique of UV absorption. In this case, the invention has the advantage over other instruments for measuring NO of having absolute calibration based on the known extinction coefficient for ozone at ultraviolet wavelengths. The invention discloses both static and dynamic flow systems, and the NO concentration measurements may be made over a wide pressure range.

Abstract: The concentration of nitric oxide in a gas is determined by oxidizing NO to NO2 and then measuring the concentration of NO2 in the gas, which is proportional to the concentration of NO. Preferably, gaseous NO2 molecules diffuse through a plurality of capillary membrane fibers and undergo a chemiluminescent reaction with a reagent flowing within; the light from the reaction is measured to determine NO2 concentration. In another aspect of a preferred embodiment, gas is passed through a scrubber before the concentration of NO2 is measured, in order to substantially remove carbon dioxide and ambient NO2 from the gas without substantially affecting the concentration of nitric oxide therein.

Abstract: A detector for detecting and measuring nitric oxide. Gas-permeable capillary membrane fibers transport a reagent solution through a plenum containing gases to be measured. Nitric oxide molecules penetrate the walls of the fibers and undergo a chemiluminescent reaction within. The fibers and the plenum are translucent, allowing photons emitted by the chemiluminescent reaction to escape and be detected by a photodetector. The reagent is buffered at an alkaline pH and mixed with the enzyme carbonic anhydrase to minimize the measurement errors caused by the presence of carbon dioxide in the gas to be measured.