# US 2004/0108197 A1 · Solid-state light source photolytic nitrogen dioxide converter

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- Number: US 2004/0108197 A1
- Document ID: US20040108197A1
- Status: Published application
- Kind: A1
- Application number: 10/313,827
- Filed: 2002-12-06
- Published: 2004-06-10
- Earliest claimed: 2002-12-06
- Assignees: Sonoma Technology
- Inventors: Martin Buhr
- Web page: https://patentgrep.com/patent/US20040108197A1

## CPC

- G01N 21/05: Flow-through cuvettes (G01N21/09 takes precedence; handling fluid samples G01N1/10)
- G01N 21/631: {using photolysis and investigating photolysed fragments}
- G01N 31/005: {investigating the presence of an element by oxidation (G01N31/12 takes precedence)}
- G01N 33/0037: {NOx}
- G01N 2021/0325: {Cells for testing reactions, e.g. containing reagents}
- Y02A 50/20: Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- Y02A: TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE

## Abstract

A solid-state light source photolytic NO2 converter including a reaction chamber made of a reflective material with diffuse reflective properties, whereby the reaction chamber includes a low volume gas cell wherein the gas sample residence time is less than 5 seconds is provided. The NO2 in the air sample is exposed to ultraviolet radiation at wavelengths less than 420 nm, whereby the NO2 is converted to NO. The NO is subsequently measured using an NO analyzer. The solid-state light source includes diode lasers and LED's that emit UV wavelength in the range of 350-420 nm. The use of a narrow wavelength range afforded by the solid-state light source results in an interference-free conversion of NO2 to NO at high efficiency.

## Claims

### Claim 1

A photolytic NO2 converter for converting NO2 present in a gas sample into NO, comprising:
a body including a reaction chamber located substantially within said body, said reaction chamber possessing at least one aperture;
a reaction chamber inlet in communication with said reaction chamber for transporting a gas sample into said reaction chamber;
a reaction chamber outlet in communication with said reaction chamber for transmitting a processed gas sample out of said reaction chamber; and
at least one solid-state light source, located substantially adjacent to said at least one aperture to enable UV wavelength radiation to pass from said at least one solid-state light source into said reaction chamber through said at least one aperture, for converting NO2 present in a gas sample transported into said reaction chamber by said reaction chamber inlet into NO in a processed gas sample for transportation out of said reaction chamber by said reaction chamber outlet.

### Claim 2 (depends on 1)

The photolytic NO2 converter as in claim 1, further comprising:
NO detector means, in communication with said reaction chamber outlet, for generating a signal indicative of a concentration of NO in said processed gas sample.

### Claim 3 (depends on 1)

The photolytic NO2 converter as in claim 1, further comprising:
at least one heat sink mounted to said body and located substantially near said at least one solid-state light source.

### Claim 4 (depends on 1)

The photolytic NO2 converter as in claim 1, further comprising:
at least one thermoelectric cooling device mounted to said body and located substantially near said at least one solid-state light source.

### Claim 5 (depends on 1)

The photolytic NO2 converter as in claim 1, wherein said reaction chamber comprises a reflective material.

### Claim 6 (depends on 5)

The photolytic NO2 converter as in claim 5, wherein said reflective material possesses diffuse reflective properties.

### Claim 7 (depends on 5)

The photolytic NO2 converter as in claim 5, wherein said reflective material possesses specular reflective properties.

### Claim 8 (depends on 6)

The photolytic NO2 converter as in claim 6, wherein said reflective material is selected from the group consisting of Teflon™-based materials and Barium Sulfate.

### Claim 9 (depends on 7)

The photolytic NO2 converter as in claim 7, wherein said reflective material is selected from the group consisting of aluminum and silver.

### Claim 10 (depends on 1)

The photolytic NO2 converter as in claim 1, wherein said solid-state light source is UV wavelength light emitting diodes (LED's).

### Claim 11 (depends on 1)

The photolytic NO2 converter as in claim 1, wherein said solid-state light source is a UV wavelength diode laser.

### Claim 12 (depends on 10, 11)

The photolytic NO2 converter according to claims 10 or 11, in which said UV wavelength is between 350 and 420 nm.

### Claim 13 (depends on 1)

The photolytic NO2 converter as in claim 1, further comprising:
a means for controllably introducing the gas sample to the reaction chamber, said reaction chamber, and said means for controllably introducing said gas sample from the reaction chamber, each comprises a volume which minimizes a residence time of the gas sample in said photolytic NO2 converter.

### Claim 14

A photolytic NO2 converter for converting NO2 present in a gas sample into NO, comprising:
a body including a reaction chamber located substantially within said body, said reaction chamber made of Teflon™-based material and possessing at least one aperture;
a reaction chamber inlet in communication with said reaction chamber for transporting a gas sample into said reaction chamber;
a reaction chamber outlet in communication with said reaction chamber for transmitting a processed gas sample out of said reaction chamber; and
at least one LED capable of producing UV wavelength radiation in the range of 350-420 nm, located substantially adjacent to said at least one aperture to enable UV wavelength radiation to pass from said at least one LED into said reaction chamber through said at least one aperture, for converting NO2 present in a gas sample transported into said reaction chamber by said reaction chamber inlet into NO in a processed gas sample for transportation out of said reaction chamber by said reaction chamber outlet.

### Claim 15

A method for converting NO2 to NO in a gas sample with a photolytic NO2 converter, said NO2 converter comprising a body and a reaction chamber located substantially within said body, said reaction chamber possessing at least one aperture; at least one solid-state light source located substantially adjacent to said at least one aperture for transmitting UV wavelength radiation into said reaction chamber through said at least one aperture; a reaction chamber inlet in communication with said reaction chamber; and a reaction chamber outlet in communication with said reaction chamber, said method comprising:
introducing said gas sample into said reaction chamber via said reaction chamber inlet;
energizing said solid-state light source;
converting NO2 contained in said gas sample to NO to produce a processed gas sample; and
exhausting said processed gas sample out of said reaction chamber via said reaction chamber outlet.

### Claim 16 (depends on 15)

The method for converting NO2 to NO as in claim 15, further comprising:
transporting said processed gas sample to a NO detector that is in communication with said reaction chamber outlet; and
generating a signal indicative of a concentration of NO in said processed gas sample as measured by said NO detector.

### Claim 17 (depends on 16)

The method for converting NO2 to NO as in claim 16, further comprising:
de-energizing said solid-state light source, thereby creating an unprocessed gas sample; and
exhausting said unprocessed gas sample out of said reaction chamber via said reaction chamber outlet.

### Claim 18 (depends on 17)

The method for converting NO2 to NO as in claim 17, further comprising:
transporting said unprocessed gas sample to a NO detector that is in communication with said reaction chamber outlet; and
generating a signal indicative of a concentration of NO in said unprocessed gas sample as measured by said NO detector.

### Claim 19 (depends on 15)

The method for converting NO2 to NO as in claim 15, further comprising:
controllably introducing the gas sample to the reaction chamber, wherein said reaction chamber, and said means for controllably introducing said gas sample from the reaction chamber, each comprises a volume which minimizes a residence time of the gas sample in said photolytic NO2 converter.

### Claim 20

A method for measuring NO2 in a gas sample with a photolytic NO2 converter, said NO2 converter comprising a body and a reaction chamber located substantially within said body, said reaction chamber possessing at least one aperture; at least one solid-state light source located substantially adjacent to said at least one aperture for transmitting UV wavelength radiation into said reaction chamber through said at least one aperture; a reaction chamber inlet in communication with said reaction chamber; and a reaction chamber outlet in communication with said reaction chamber, said method comprising:
introducing said gas sample into said reaction chamber via said reaction chamber inlet;
energizing said solid-state light source;
converting nitrogen dioxide contained in said gas sample to NO to produce a processed gas sample; and
exhausting said processed gas sample out of said reaction chamber via said reaction chamber outlet.

### Claim 21 (depends on 20)

The method for measuring NO2 as in claim 20, further comprising:
transporting said processed gas sample to a NO detector that is in communication with said reaction chamber outlet; and
generating a signal indicative of a concentration of NO in said processed gas sample as measured by said NO detector.

### Claim 22 (depends on 20)

The method for measuring NO2 to NO as in claim 20, further comprising:
de-energizing said solid-state light source, thereby creating an unprocessed gas sample; and
exhausting said unprocessed gas sample out of said reaction chamber via said reaction chamber outlet.

### Claim 23 (depends on 22)

The method for measuring NO2 as in claim 22, further comprising:
transporting said unprocessed gas sample to a NO detector that is in communication with said reaction chamber outlet; and
generating a signal indicative of a concentration of NO in said unprocessed gas sample as measured by said NO detector.

### Claim 24 (depends on 19)

The method for converting NO2 to NO as in claim 19, further comprising:
a means for controllably introducing the gas sample to the reaction chamber, said reaction chamber, and said means for controllably introducing said gas sample from the reaction chamber, each comprises a volume which minimizes a residence time of the gas sample in said photolytic NO2 converter.