Chemical apparatus and process disinfecting – deodorizing – preser – Analyzer – structured indicator – or manipulative laboratory... – Means for analyzing liquid or solid sample
Reexamination Certificate
1997-05-08
2001-12-11
Warden, Jill (Department: 1743)
Chemical apparatus and process disinfecting, deodorizing, preser
Analyzer, structured indicator, or manipulative laboratory...
Means for analyzing liquid or solid sample
C422S086000, C422S091000, C422S082050, C422S082090, C436S111000, C436S112000, C436S164000
Reexamination Certificate
active
06328932
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the reversible detection and measurement of trace amounts of basic gases, and particularly to the detection of hydrazine and alkyl hydrazines. More specifically the invention relates to a fiber optic sensor comprising dyes which change color and/or bleach on interaction with a basic gas.
BACKGROUND OF THE INVENTION
Several types of gas sensors, including electrochemical, surface acoustic wave (SAW), thermal conductivity and fiber optic sensors, are known in the art. As a class, fiber optic sensors have significant potential advantage over other sensing techniques. Their small size (3-1000 &mgr;M) permits in-situ sensing; long-term stability can likely be achieved using silica or plastic fibers; remote sensing using a fiber optic network in which a fiber carries the signal to a central detector is possible; manufacturing and maintenance costs are low when standard optoelectronic components are utilized; the sensors, themselves, are non-electrical devices which may alleviate safety concerns; the sensors can be incorporated into a multi-site network; and the sensors are versatile, since the optical sensing method can use absorption (including reflectance and scattering), emission, or refractive index changes for detection; and it is possible in these optical methods to use different light frequencies.
SUMMARY OF THE INVENTION
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. The transducer molecule undergoes a change in optical response, e.g., a color change, a change in fluorescence or a change in another measurable optical response, on interaction with the analyte. An optical property of light input into the optical fiber is affected by the change in optical response of the immobilized transducer molecules interacting with the analyte. The change in the optical property of light is detected and measured to detect the presence of the analyte and to measure the amount of analyte present in the environment of the sensor.
The transducer molecule is preferably a dye which undergoes a color change on interaction with the analyte. The dye is preferably selected from the group consisting of triphenylmethane dyes and xanthene dyes or combinations thereof, particularly those dyes which undergo a reversible color change, including bleaching, on interaction with the analyte. The transducer molecule is present, immobilized in contact with the optical fiber core, in an amount sufficient to allow detection of the analyte by the sensor.
Preferred transducer molecules for detection of basic gases, particularly hydrazine and hydrazine derivatives, are triphenylmethane dyes, with malachite green and crystal violet being more preferred.
In specific embodiments, the transducer molecule is a dye immobilized in a polymer layer in contact with the fiber core. A preferred polymer is poly(vinylchloride). The polymer layer is preferably a thin layer, several &mgr;m up to about 10 &mgr;m thick. The polymer material is preferably plasticized (i.e., the layer contains a plasticizer) and the preferred plasticizer for poly(vinylchloride) is a dialkyl sebacate plasticizer and more preferably the plasticizer for poly(vinylchloride) is bis-(2-ethylhexyl)sebacate.
The fiber optic sensor of this invention can be configured in several different modes.
The sensor, in any sensing mode or configuration, is optically coupled to a light source (signal light source) which provides input light having at least one wavelength (or band of wavelengths) at which a change in optical response due to the interaction of the analyte with the transducer molecule can be monitored (herein the signal wavelength). The sensor is also optically coupled to a detector, e.g., a photodetector, to allow measurement of optical changes, e.g., light intensity, or fluorescence intensity, of light exiting the sensor.
In any sensing mode or configuration, the sensor can be provided with a reference system to compensate for variations in optical response unrelated to the presence of analyte, e.g., light source and detector variation. The sensor can be equipped with a reference light source optically coupled to the sensor to provide a second wavelength of light (or band of wavelengths) that is substantially unaffected by the interaction of the transducer with the analyte. A single light source providing light at both the reference and signal wavelengths can also be used. Light exiting the sensor at the signal wavelength and at reference wavelength are independently detected for comparison. A single detector can be used to measure both the reference and signal wavelength. The sensor is optionally equipped with a second reference detector provided to detect light at the reference wavelength.
The sensors of this invention can be employed in a variety of device configurations including single-site sensors and multiple-site sensor networks. In the multi-site device mode, several sensors, typically spatially separated, can be monitored for the presence of a basic gas to determine its concentration.
The invention also provides a method for detection of basic gases, including hydrazine and hydrazine derivatives, using the sensors and sensor devices and networks of this invention. The devices of this invention, particularly those using triphenylmethane dyes as the transducers molecules, are useful for the detection of hydrazines and alkyl hydrazines in the presence of potentially interfering species, such as ammonia.
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Venkata
Carter Michael T.
Schwartz Michael
Eltron Research, Inc.
Greenlee Winner and Sullivan P.C.
Handy Dwayne K
Warden Jill
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