Chemistry: analytical and immunological testing – Nitrogen containing
Reexamination Certificate
1999-05-17
2001-11-13
Warden, Jill (Department: 1743)
Chemistry: analytical and immunological testing
Nitrogen containing
C436S103000, C436S104000, C422S082000
Reexamination Certificate
active
06316268
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to chemical microsensor devices including a layer of a cyclodextrin-derivative and to a process for the detection of trace amounts of selected organic compounds including nitro-containing organic compounds (e.g., explosives) and/or chemical warfare agents. This invention is the result of a contract with the Department of Energy (Contract No. W-7405-ENG-36).
BACKGROUND OF THE INVENTION
The detection of nitro-containing organic compounds is necessary for finding unexploded ordnance or buried land mines or for finding the presence of explosive materials, e.g., hidden within airline luggage. Safety or security concerns over such explosive materials require improved monitoring and/or, analysis for the detection of selected volatile nitro-containing compounds generally present as minor contaminants within common explosive compounds such as trinitrotoluene (TNT). While analytical techniques are available to detect the presence of many substances down to levels as low as parts per billion (ppb) or less, such analytical techniques generally require collecting a sample in the field, taking the sample to a laboratory, and analyzing the sample by, e.g., gas chromatography or mass spectroscopy. Such analysis requires sophisticated equipment that generally requires up to several days to obtain final results and such analysis is not generally suited to field use. Thus, present analytical techniques fail to provide any real-time information about the presence of nitro-containing organic compounds.
Another category of materials sought to be detected on a real-time basis are chemical compounds used in chemical warfare generally referred to as chemical warfare agents (CW agents) such as nerve gas or blister agents. The detection of CW agents to allow for protection of personnel or to allow for detection of suspected production sites is important.
Much prior research has been directed to developing chemical sensors that can give more rapid feedback information. One example is U.S. Pat. No. 5,151,110 wherein a sensor includes a piezoelectric substrate, preferably contained within a surface acoustic wave (SAW) device or a quartz crystal microbalance (QCM) device, and a coating, such as zeolite crystals in an inorganic silica matrix, applied to the substrate to selectively sorb chemical entities of a size less than a predetermined magnitude. While such a chemical sensor is useful, it is limited to materials that physically fit within the particular pore sizes of the zeolite crystals.
U.S. Pat. No. 4,860,573 describes a composite substrate intended for an apparatus for quantitative detection of, e.g., an organic component present in a gas or liquid. Cyclodextrin is described as one material for incorporation as an active site material into the composite substrate. However, there is no teaching or suggestion of multilayers of the active site material, nor is there any teaching or suggestion of using cyclodextrin derivatives or of forming oriented cyclodextrin derivative structures by the controlled assembly of such materials through layer by layer build up or addition.
U.S. Pat. No. 5,418,058, issued to Li et al. on May 23, 1995, describes chemical microsensors for the detection of selected organic compounds such as aromatic compounds, polyaromatic compounds, oxygen-containing organic compounds, and halogenated hydrocarbons. In the formation of the microsensor, a linking molecule of, e.g., bistrichlorosilylhexane, was used to covalently bond the sensing molecule, i.e., the cyclodextrin derivative, to the transducer surface. There is no teaching or suggestion of the detection or nitro-containing organic compounds with the disclosed chemical microsensors, nor any teaching or suggestion of asymmetrical linking agents for covalently bonding the cyclodextrin material to the transducer surface.
It is an object of the present invention to provide a chemical sensor including a cyclodextrin derivative and a method of detecting nitro-containing organic compounds and/or CW agents, preferably in an on-site, real time process.
It is a further object of the invention to provide a chemical microsensor, including a cyclodextrin derivative, having sensitivity to detect low levels of such nitro-containing chemical compounds or CW agents, preferably at a sub-ppb level.
It is a still further object of the invention to provide a reversible chemical microsensor including a cyclodextrin derivative.
Yet another object of the present invention is to provide a chemical microsensor formed through a layer by layer build up process.
Another object of the present invention is to provide a chemical microsensor formed through a layer by layer build up process using an asymmetrical bifunctional linking agent as one layer of the microsensor.
Still another object of the present invention is a chemical microsensor system utilizing a reference sensor substantially identical to a cyclodextrin-derivative containing sensor except for the cyclodextrin-derivative material layer.
Yet another object of the present invention is to form a chemical bond, i.e., a hydrogen bond between the cyclodextrin material and the target compounds.
Yet a further object of the present invention is to provide asymmetrical functionalization on the top rim of a cyclodextrin, e.g., some hydroxyl functionalization plus some methoxy functionalization, leaving at least one functionality with hydrogen bonding potential.
SUMMARY OF THE INVENTION
To achieve the foregoing and other objects, and in accordance with the purposes of the present invention, as embodied and broadly described herein, the present invention provides a chemical microsensor including a substrate including an oxide layer, a linking agent including a linear alkane chain containing from about 8 to about 18 carbon atoms attached to the oxide layer, and, a cyclodextrin-derivative covalently bonded to the linking agent.
The present invention further provides a method of detecting trace amounts of nitro-containing organic species within an environment including placing a selective chemical sensor into an environment, the sensor including a substrate having an oxide surface layer thereon and a selective thin film of a cyclodextrin derivative chemically bound upon the substrate, the film adapted for the chemically bonding of a nitro-containing organic compound therewith, for a sufficient time wherein nitro-containing organic species can form complexes with the cyclodextrin derivative, measuring a change resulting from complexation of nitro-containing chemical species with the cyclodextrin derivative, and correlating the measured change with a quantitative or qualitative output relating to the nitro-containing organic species.
In one embodiment of the invention is provided a chemical microsensor system including a first sensing portion including a first substrate having a surface oxide layer thereon, a linking agent including a linear alkane chain containing from about 8 to about 18 carbon atoms attached to the surface oxide layer of the first substrate, a cyclodextrin-derivative covalently bonded to the lining agent of first substrate, a second sensing portion including a second substrate having a surface oxide layer thereon, the linking agent including a linear alkane chain containing from about 8 to about 18 carbon atoms attached to the surface oxide layer of the second substrate, the first and second sensing portions electronically linked so as to provide measurements of a system wherein the second sensing portion serves as a reference to the first sensing portion.
REFERENCES:
patent: 4860573 (1989-08-01), Barendz et al.
patent: 5151110 (1992-09-01), Bein et al.
patent: 5266271 (1993-11-01), Bankert et al.
patent: 5418058 (1995-05-01), Li et al.
Chemical Abstracts 122:121994, 1994.
Swanson Basil I.
Yang Xiao-Guang
Cole Monique T.
Cottrell Bruce H.
The Regents of the University of California
Warden Jill
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