Nitric Oxide Detection

• US 20080261322A1
• Filed: 09/04/2006
• Published: 10/23/2008
• Est. Priority Date: 09/06/2005
• Status: Active Grant

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Burdinski, Dirk
• Granted Patent: US 7,687,275 B2
• Time in Patent Office: Days
• US Class Current: 436/116
• CPC Class Codes: G01N 33/0037 NOx
• 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 436/173076 Nitrite or nitrate
• CPC Class Codes: Y10T 436/177692 Oxides of nitrogen
• CPC Class Codes: Y10T 436/20 Oxygen containing
• CPC Class Codes: Y10T 436/204165 Ethanol

Abstract

The present invention relates to a method for amplifying the detected signal in a gas sensor. More specifically, the present invention relates to a method for increasing the concentration of the gas which is being detected in a sample or increasing the concentration of a gas which is directly obtained from the gas in the sample by chemical reaction. The gas which is to be detected is nitric oxide (NO). In particular, the method concerns the selective conversion of NO to NO2 which allows a threefold amplification of the number of analyte molecules in NO trace gas analysis in a single amplification cycle. Subsequent reduction or thermal decomposition of the obtained NO2 can provide NO again, which can again be introduced in a new amplification cycle. Multiple (n) amplification cycles can provide a sensitivity amplification by a factor 3ⁿ. The method can be combined with a multitude of detection methods and tolerates a high humidity. The method is therefore of general use in the analysis of NO from a variety of sources.

Claims

1. A method of determining the concentration of nitric oxide in a gaseous sample, wherein the method comprises the following steps:

a collecting a gaseous sample (6) containing nitric oxide,

b) exposing the sample (6) to a first substrate (12) to which nitric acid is bound in the presence of water to form nitrogen dioxide by reaction with the nitric oxide, and

c) determining (15, 19) the concentration of nitric oxide in the gaseous sample from the nitrogen dioxide produced in step (b).

2. A method according to claim 1, wherein it further comprises:

d) exposing the nitrogen dioxide to a second substrate (17) which is associated with a reducing agent so as to form amplified nitric oxide from any nitrogen dioxide present;

e) determining (19) the concentration of nitric oxide in the gaseous sample from the amplified nitric oxide.

3. A method according to claim 2, wherein it further comprises:

performing in turn one or more sequential exposing steps b) and d) on the gaseous sample resulting in amplified nitric oxide and then measuring the concentration of the resulting amplified nitric oxide if the performing is stopped after performing exposing step d) and measuring the concentration of the resulting nitrogen dioxide if the performing is stopped after performing exposing step b).

4. A method according to claim 1, wherein the first and second substrates are comprised in a same substrate.

5. A method according to claim 1, wherein the concentration of nitric oxide is determined by spectroscopy or gas chromatographic techniques.

6. A method according to claim 1, it further comprises between steps a) and b):

passing the sample through at least one chemical scrubbing unit.

7. A method according to claim 6, wherein the chemical scrubbing unit is an acidic or neutral column.

8. An apparatus for measuring the concentration of nitric oxide in a gaseous sample, the apparatus including the following components arranged in fluid communication:

a first vessel (6) for collecting a gaseous sample containing nitric oxide;

a first reaction chamber (9) in fluid communication (8, 10) with the first vessel containing a first substrate whose surface is able to provide a source of nitric acid and water enabling the formation of nitrogen dioxide after exposition of the sample to the first substrate; and

,

means (15, 19) for determining the concentration of the nitric oxide from the nitrogen dioxide.

9. An apparatus according to claim 8, wherein it further comprises

a second reaction chamber (14) that is in fluid communication with the first reaction chamber and containing a second substrate (17) whose surface includes a reducing agent which forms amplified nitric oxide once in contact with the nitrogen dioxide;

and wherein the determining means (19) further determines the concentration of nitric oxide from the amplified nitric oxide.

10. An apparatus according to claim 8, wherein the first and second substrates are intimately mixed.

11. An apparatus according to claim 8, wherein the first and second substrates are present as separate layers in the first reaction chamber.