Chemical apparatus and process disinfecting – deodorizing – preser – Analyzer – structured indicator – or manipulative laboratory... – Means for analyzing liquid or solid sample
Reexamination Certificate
1999-02-01
2001-11-27
Warden, Jill (Department: 1743)
Chemical apparatus and process disinfecting, deodorizing, preser
Analyzer, structured indicator, or manipulative laboratory...
Means for analyzing liquid or solid sample
C422S082050, C436S139000, C436S164000, C436S172000
Reexamination Certificate
active
06322751
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a chemical sensor (“optrode”) for the quantitative measurement of selected volatile organic and inorganic molecules in atmospheres. This is a refinement of the optrode design of Milanovich et al. The optrode has been modified in several important ways to allow for ease of manufacture and greater sensitivity.
The simplified design and operation of the optrode coupled with chemical specificity and low limits of detection makes the invention an attractive alternative to other forms of chemical analysis. The optrode has been shown to attain the precision and accuracy of gas chromatography with photoionization or Hall detectors for selected organic molecules, such as trichloroethene and chloroform. However, the optrode attains this performance without the need for preconcentration (such as purge and trap) or Hall detectors for selected organic molecules, such as thichloroethene and chloroform. However, the optrode attains this performance without the need for preconcentration (such as purge and trap) or separation (chromatography) steps. The optrode has been found to have a limit of detection of 1 part per billion of trichloroethene in water with 1,2-dichloroethene and tetrachloroethene present. Because of these performance factors and the ease of use of the optrode, there are many applications in environmental, health & safety, medical and process control fields for such a chemical sensor.
One of the important applications of the optrode is the creation of “real-time” sampling/analytical units for the monitoring of trichloroethene in ground water. The cost savings to the government and industry in avoiding the cost of manually sampling the sells, disposal of the purge water and the cost of the analytical laboratory over the lifetime of a ground-water restoration project can be significant.
Current optrode technology is divided into two primary types of designs. The most prevalent type of design in the literature is fabricating the optrode body from some type of inert material, and providing a port or area in the wall to be fitted with a permeable material. The species of interest, i.e. trichloroethene, passes through the permeable membrane and reacts with the reagent contained within the body of the sensor. Examples of the first type of optrode are Klainer et al., U.S. Pat. No. 5,116,759, and Miller et al., U.S. Pat. No. 4,666,674. The second type of optrode uses a permeable tube which serves as the body of the optrode. This type of sensor was developed by Milanovich it al. at Lawrence-Livermore National Laboratory, Livermore, Calif. The original design was disclosed in a series of papers. The design was very difficult to manufacture and suffered from several material compatibility problems. The reagents used in the design attacked the seals and other components reducing the life of the optrode.
This invention relates to a simplified design of the optrode which increases the life of the device while providing lower noise and resolution of other associated problems.
SUMMARY OF THE INVENTION
This invention is directed to the elimination of seals and dead space in the fabrication of the sensor first proposed by Milanovich et al. The seals were eliminated to reduce material compatibility problems and the dead space was eliminated to reduce probability of bubble formation. The reduction of the material compatibility problems increases the life of the optrode and significantly decreases the noise observed when analyzing very low concentrations of analytes. In particular it was found that various types of epoxy resins and stainless steel tubes were reacting with some reagents. Dead spaces were found to aid in the formation or entrapment of bubbles. When the air bubbles interfere with the light path, the optrode performance is degraded.
The best solution found for the elimination of the above factors while providing for ease of manufacture was to provide for the optic fiber to be centered inside and slightly projecting from the end of a small gauge fluorocarbon tube. The permeable fluorocarbon optrode body is then fitted over the outside diameter of the tube. The opposite side of the small gauge tube is either fitted into an inert block which allows for the independent introduction of the reagent from the side of the block, or the reagent enters the small gauge tube at the same point as the fiber optic. The sealing of the fiber optic with the fluorocarbon tube is accomplished with heat shrink fluorocarbon tubing.
REFERENCES:
patent: 4544231 (1985-10-01), Peterson
patent: 4666672 (1987-05-01), Miller et al.
patent: 4786171 (1988-11-01), LeFebre et al.
patent: 4892383 (1990-01-01), Klainer et al.
patent: 5107133 (1992-04-01), Klainer et al.
patent: 5116759 (1992-05-01), Klainer et al.
Handy Dwayne K
Warden Jill
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