Nitric oxide gas detector

• US 6,635,415 B1
• Filed: 04/19/2000
• Issued: 10/21/2003
• Est. Priority Date: 03/09/1998
• Status: Expired due to Term

• Current Assignee: Ludlum Measurements, Inc.
• Original Assignee: 2B Technologies, Inc.
• Inventors: Birks, John W., Bollinger, Mark J., Robinson, Jill K.
• Primary Examiner(s): Soderquist, Arlen
• Application Number:
  US09/552,285
• Time in Patent Office: 1,280 Days
• Field of Search: 422/81-83, 422/88, 422/82.05, 422/91, 436/106, 436/116, 436/117, 436/118, 436/172, 436/175, 436/177, 436/178, 436/181, 435/4
• US Class Current: 435/4
• CPC Class Codes: G01N 2033/4975 other than oxygen, carbon dioxide or alcohol, e.g. organic vapours
• CPC Class Codes: G01N 21/766 of gases
• CPC Class Codes: G01N 33/0037 for NOx
• CPC Class Codes: G01N 33/497 of gaseous biological material, e.g. breath
• CPC Class Codes: Y02A 50/20 Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
• CPC Class Codes: Y10T 436/17 Nitrogen containing
• CPC Class Codes: Y10T 436/177692 Oxides of nitrogen
• CPC Class Codes: Y10T 436/178459 Only nitrogen dioxide
• CPC Class Codes: Y10T 436/179228 Both nitrogen oxide and dioxide
• CPC Class Codes: Y10T 436/25125 Digestion or removing interfering materials
• CPC Class Codes: Y10T 436/25375 Liberation or purification of sample or separation of material from a sample [e.g., filtering, centrifuging, etc.]
• CPC Class Codes: Y10T 436/255 including use of a solid sorbent, semipermeable membrane, or liquid extraction

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.

Claims

1. A method for measuring the concentration of nitric oxide in exhaled human breath gas, comprising the steps of:

providing a reagent that participates in a chemiluminescent reaction with nitric oxide, said reagent including carbonic anhydrase;

inducing a flow of said reagent within a plurality of translucent capillary membrane fibers composed of material sufficiently thin and porous to allow gaseous nitric oxide molecules to diffuse into the translucent capillary membrane fiber or fibers and sufficiently hydrophobic to prevent the reagent from substantially diffusing out of the translucent capillary membrane fiber or fibers;

passing the gas to be sampled over the surface of the translucent capillary membrane fiber or fibers; and

measuring the amount of light generated by the chemiluminescent reaction between the reagent and the gas which has passed through the walls of the translucent capillary membrane fiber or fibers.