# US 6,328,932 B1 · Devices and methods for the detection of basic gases

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- Number: US 6,328,932 B1
- Document ID: US6328932B1
- Status: Granted
- Kind: B1
- Application number: 08/853,380
- Filed: 1997-05-08
- Granted: 2001-12-11
- Earliest claimed: 1997-05-08
- Assignees: Eltron Research, Inc.
- Inventors: Michael T. Carter; Michael Schwartz
- Web page: https://patentgrep.com/patent/US6328932B1

## CPC

- G01N 21/7703: {using reagent-clad optical fibres or optical waveguides (using measurement of total internal reflection or attenuated total reflection G01N21/552; optical fibres or waveguides per se G02B)}
- G01N 21/78: producing a change of colour
- Y10T 436/173845: Amine and quaternary ammonium
- Y10T 436/174614: Tertiary amine
- 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)
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

This invention provides a fiber optic sensor and sensor devices for the reversible detection of basic gas analytes, including hydrazine, alkyl hydrazines, amines, ammonia, and related chemical species. The optical fiber sensor is formed in an optical fiber which conventionally comprises an optical fiber core and a cladding layer. Transducer molecules are immobilized in contact with an exposed surface of the fiber core to allow interaction of the immobilized species with analytes in the environment around the sensor. Preferred transducer molecules for detection of basic gases, particularly hydrazine and hydrazine derivatives, are xanthene dyes and triphenylmethane dyes, including malachite green and crystal violet. The sensors of this invention can be employed in a variety of device configurations including single-site sensors and multiple-site sensor networks.

## Claims

### Claim 1

A fiber optic sensor for detection of basic gases which comprises an optical fiber having a cladding and a fiber optic core and a layer comprising a dye in contact with an outer surface of said fiber optic core wherein said dye undergoes a color change on interaction with a basic gas, wherein said dye is selected from the group consisting of tripenylmethane dyes, xanthene dyes and combinations thereof and wherein said layer comprises said dye immobilized in a polymer.

### Claim 2 (depends on 1)

The fiber optic sensor of claim 1 wherein said polymer is poly(vinylchloride).

### Claim 3 (depends on 2)

The fiber optic sensor of claim 2 wherein said polymer layer further comprises a plasticizer.

### Claim 4 (depends on 3)

The fiber optic sensor of claim 3 wherein said plasticizer is a dialkyl sebacate plasticizer.

### Claim 5 (depends on 4)

The fiber optic sensor of claim 4 wherein said plasticizer is bis-(2-ethylhexyl) sebacate.

### Claim 6 (depends on 1)

The fiber optic sensor of claim 1 wherein said dye is a triphenylmethane dye.

### Claim 7 (depends on 6)

The fiber optic sensor of claim 6 wherein said dye is malachite green.

### Claim 8 (depends on 6)

The fiber optic sensor of claim 6 wherein said dye is crystal violet.

### Claim 9 (depends on 1)

A fiber optic sensor network for detection of basic gases which comprises:
a. a plurality of optical fiber sensors of claim 1,
b. a light source optically coupled to said sensors which provides at least one wavelength of light at which said color change can be monitored;
c. a light detector optically coupled to said sensor for measuring optical changes in light exiting said sensor; and
(d) means for correlating the detected optical change to the presence of basic gas.

### Claim 10 (depends on 9)

The fiber optic sensor network of claim 9 wherein in each of said sensors said optical fiber has an entrance end and a distal end which is reflective and said light source and said detector are both optically coupled to the entrance ends of each said optical fibers.

### Claim 11 (depends on 9)

The fiber optic sensor network of claim 9 wherein said optical sensors are positioned at different distances from said detector.

### Claim 12 (depends on 11)

The fiber optic sensor network of claim 11 wherein said light source is pulsed and said light detector can monitor light intensity as a function of delay time for reflection of said pulsed light back from each of said sensors.

### Claim 13 (depends on 9)

A fiber optic sensor network of claim 9 wherein the length of optical fiber between at least two sensors is greater than the physical distance between said sensors.

### Claim 14 (depends on 1)

The fiber optic sensor of claim 1 wherein a portion of said cladding is removed and said layer is in contact with said exposed outer surface of said optical fiber core.

### Claim 15 (depends on 1)

The fiber optic sensor of claim 1 wherein said optical fiber has an entrance end and a distal end which is reflective such that light entering said entrance end is reflected of said distal end an exits the sensor through said entrance end.

### Claim 16 (depends on 15)

The fiber optic sensor of claim 15 wherein said optical fiber has an entrance end and an exit end such that light entering said entrance end exits said sensor at said exit end.

### Claim 17 (depends on 1)

The fiber optic sensor of claim 1 wherein said dye is a triphenylmethane dye.

### Claim 18 (depends on 17)

The fiber optic sensor of claim 17 wherein said dye is a dye of formula:
where the M and M′ groups can be H or an N(R)2 group and the R groups, which can be the same or different groups at different sites, can be H, an alkyl group, an aryl group or alkylaryl groups and X is an anion.

### Claim 19 (depends on 18)

The fiber optic sensor of claim 18 wherein M is H, M is N(R)2 and each R group is selected, independently of other R groups, from H or small alkyl groups having from 1-6 carbon atoms.

### Claim 20 (depends on 18)

The fiber optic sensor of claim 18 wherein M and M′ are both an N(R)2 group.

### Claim 21 (depends on 18)

The fiber optic sensor of claim 18 wherein each R group, independently of any other R groups, is selected from H or small alkyl groups having from 1-6 carbon atoms.

### Claim 22 (depends on 17)

The fiber optic sensor of claim 17 wherein said dye is selected from the group consisting of crystal violet, malachite green, brilliant green, methyl violet and ethyl violet.

### Claim 23 (depends on 1)

A method for detection of a basic gas analyte which comprises contacting the fiber optic sensor of claim 1 with an environment that may contain said basic gas and thereafter measuring the optical response of the sensor on interaction with said environment.

### Claim 24 (depends on 23)

The method of claim 23 wherein the basic gas is a hydrazine or alkyl hydrazine.

### Claim 25 (depends on 23)

The method of claim 23 wherein the basic gas is ammonia or an amine.

### Claim 26 (depends on 23)

The method of claim 23 wherein the basic gas is selected from the group consisting of hydrazine, monomethylhydrazine and 1,1′-dimethylhydrazine.

### Claim 27 (depends on 23)

The method of claim 23 wherein the basic gas is detected in the presence of ammonia, hydrogen sulfide, SO2 or water.

### Claim 28 (depends on 1)

A fiber optic sensor device for detection of basic gases which comprises:
(a) an optical fiber sensor of claim 1,
(b) a light source optically coupled to said sensor which provides at least one wavelength of light at which said color change can be monitored;
(c) a light detector optically coupled to said sensor for measuring optical changes in light exiting said sensor and
(d) means for correlating the detected optical change to the presence of basic gas.

### Claim 29 (depends on 28)

The fiber optic sensor device as in claim 28 wherein a portion of the cladding of said optical fiber is removed to expose an outer surface of said core.

### Claim 30 (depends on 28)

The fiber optic sensor device of claim 28 wherein said optical fiber has an entrance end and a distal end which is reflective and said light source and said detector are both optically coupled to the entrance end of said optical fiber.

### Claim 31 (depends on 28)

The fiber optic sensor device of claim 28 wherein said optical fiber has an entrance end and an exit end, said light source is optically coupled to said entrance end and said detector is optically coupled to said exit end.

### Claim 32 (depends on 28)

The fiber optic sensor device of claim 28 wherein said light source further provides a second wavelength of light that is substantially unaffected by the color change of said dye and can be used as a reference.

### Claim 33 (depends on 28)

The fiber optic sensor device of claim 28 which comprises two light sources: a signal light source which provides a wavelength of light at which said color change can be monitored and a reference light source which provides a wavelength of light substantially unaffected by the color change of said dye.

### Claim 34 (depends on 28)

The fiber optic sensor device of claim 28 wherein the intensity of said signal light source and said reference light source can be separately controlled.

### Claim 35 (depends on 28)

The fiber optic sensor device of claim 28 wherein said light source can provide light pulses.

### Claim 36 (depends on 28)

The fiber optic sensor device of claim 28 wherein the dye is immobilized in poly(vinylchloride).

### Claim 37 (depends on 36)

The fiber optic sensor device of claim 36 where the poly(vinylchloride) layer comprises a dialkyl sebacate plasticizer.

### Claim 38

A method for detection of a basic gas analyte which comprises the steps of:
(a) contacting a fiber optic sensor with an environment that may contain a basic gas where the sensor comprises an optical fiber having a cladding, a fiber optic core and a layer comprising a triphenylmethane dye or combination of triphenylmethane dyes which undergo a color change on interaction with said basic gas wherein the dye has the formula:
where M and M′ groups are selected from the group consisting of H and N(R)2 groups where the R group, which can be the same or different groups at different sites are selected from the group consisting of H, an alkyl group, an aryl group and an alkyl aryl group and X− is an anion;
(b) measuring the optical response of the sensor on interaction with said environment; and
(c) correlating the optical response to the presence of basic gas in the environment.

### Claim 39 (depends on 38)

The method of claim 38 wherein the basic gas is hydrazine or an alkyl hydrazine.

### Claim 40 (depends on 39)

The method of claim 39 wherein hydrazine or an alkyl hydrazine is detected in the presence of ammonia, hydrogen sulfide, SO2 or water.

### Claim 41 (depends on 38)

The method of claim 38 wherein the basic gas in ammonia or an amine.

### Claim 42

A method for detection of a basic gas analyte which comprises the step of
(a) contacting a fiber optic sensor with an environment that may contain a basic gas where the sensor comprises an optical fiber having a cladding, a fiber optic core and a layer comprising a xanthene dye or combination of xanthene dyes which undergo a color change on interaction with said basic gas wherein the dye has the formula:
where M and each R1-R4, independently of one another, are selected from the group consisting of H, an alkyl group, an alkylaryl group and an aryl group and wherein X− is an anion; and
(b) measuring the optical response of the sensor on interaction with said environment.

### Claim 43 (depends on 42)

The method of claim 42 wherein the basic gas is hydrazine or an alkyl hydrazine.

### Claim 44 (depends on 42)

The method of claim 42 wherein the basic gas is ammonia or an amine.