Radiant energy – Luminophor irradiation – With ultraviolet source
Reexamination Certificate
2002-01-30
2003-10-14
Gutierrez, Diego (Department: 2875)
Radiant energy
Luminophor irradiation
With ultraviolet source
C250S458100
Reexamination Certificate
active
06633043
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to spectroscopy. More particularly, the present invention relates to the spectral characterization of crude oil using time-resolved laser-induced fluorescence spectroscopy.
2. Description of the Related Art
Characterization of petroleum oil is customarily made using a number of analytical methods that investigate its physical and chemical properties(See Ali. “Full Range Crudes, Analytical Methodology of.” in Encyclopedia of Analytical Chemistry. R. A. Meyers (Ed.) pp. 6709-6726. John Wiley & Sons Ltd, Chichester, 2000)). These methods, which have been standardized comprehensively by ASTM, aim at identifying a number of characteristics such as density, thermal stability, heavy-metal contents, types and quantities of the hydrocarbon groups, types and quantities of the aliphatic and aromatic compounds, etc., which collectively can provide complete sets of data useful in characterizing the petroleum oil. However, because all of these analytical methods require sample preparation, they cannot be used in situations where instant and/or remote characterization is needed. In such cases the laser-induced fluorescence methods would be more suitable. These latter methods give information about the oils by investigating their broad emission spectra when they are excited at specific wavelengths.
The resulting broad emission spectra are due to hundreds of different compounds comprising the oils, which fluoresce with effective lifetimes ranging from a few picoseconds to a few tens of nanoseconds. To get laser-induced fluorescence spectra that are as useful as possible in the characterization process, the excitation wavelength should be in the UV region so that the produced spectra will include contributions from the light aromatic compounds, which usually provide important features along the short wavelength end of the spectra.
The usefulness of these laser-induced fluorescence methods as characterization methods depends largely on the type of the technique employed. There are several of these techniques whose characterization abilities range from merely detecting the presence of oil, as a pollutant for example, to actually distinguishing the different types of oils from each other(See Eastwood. Modern Fluorescence Spectroscopy, V 4 Wehry, Plenum and references therein (1981)). The simplest of these methods is an approved method by both the American Society of testing and materials (ASTM) (See ASTM Book of Standards (1978), p. 720, D3650-78) and the US Coast Guard(See Oil Spill Identification System, Chemistry Branch, U.S. Coast Guard R&D Center, Report No. DOT-CG-D-52-77 (June 1977)3, and it relies on recording the wavelength-resolved fluorescence spectra while exciting the oil with a single UV radiation at 254 nm.
This method can, in principle, be applied in remote sensing, but the information derived from it will allow the distinguishing between only the broad classes of oils, e.g., between light refined oil, crude oil, and heavy residual oil, and not between different grades of oils belonging to the same broad class, e.g., between Light crude oil and Medium crude oil. To do so other fluorescence techniques such as the synchronous scan fluorescence spectroscopy, contour(total luminescence) spectroscopy, or time-resolved fluorescence spectroscopy should be employed.
The synchronous scan fluorescence spectroscopy technique produces spectra resulting from scanning both the excitation wavelength and the detection wavelength with a fixed wavelength separation. By using this technique(See Lloyd. “The nature and evidential value of the luminescence of automobile engine oils and related materials. Part I. Synchronous excitation of fluorescence emission.” Journal of Forensic Science Society, vol. 11, pp. 83-94 (1971); Lloyd. “The nature and evidential value of the luminescence of automobile engine oils and related materials. Part III. Separated Luminescence.” Journal of Forensic Science Society. Vol. 11, pp. 235-253 (1971); Lloyd. “The nature and evidential value of the luminescence of automobile engine oils and related materials. Part II. Aggregate Luminescence.” Journal of Forensic Science Society. Vol. 11, pp. 153-170 (1971); Lloyd “Partly Quenched, Synchronously Excited Fluorescence Emission Spectra in the Characterization of Complex Mixtures.” Analyst vol. 99, pp. 729-738 (1974); and Vo-Dinh, et al. “Polynuclear Aromatic Hydrocarbons”, 3
rd
International Symposium of Chemical Biology—Carcinogens and Mutagens, p. 111 (1978)) it is possible to distinguish oils belonging to the same broad class from each other, e.g., Light crude oil from Heavy crude oil, but the distinguishing ability is still not adequate enough to discriminate between crude oils of closer grades, such as Medium crude oil and Heavy crude oil(See Shen, et al. “Identification of spilled crude oils from similar Origins.” Arabian Journal of Science and Engineering, vol. 10, p. 63 (1984)). In addition, this technique cannot be practically used in remote sensing since it is not easy to tune a high-intensity laser over a wide range of excitation wavelengths.
The contour (total luminescence) spectroscopy technique(See Hornig, Proceedings, Pattern Recognition Applied to Oil Identification, Coronado, Calif. (1976); Warner et al. “Analysis of Multicomponent Fluorescence Data.” Analytical Chemistry, vol. 49, p. 564-573 (1977); and Giering et al. “Total Luminescence Spectroscopy, A powerful technique for mixture analysis.” American Laboratory, vol. 9 No. 11, pp. 113-123 (1977)) is another technique that can be used for the purpose of crude oil characterization. It produces contour diagrams of oils that are constructed out of many emission spectra each of which is excited at a different wavelength.
This method has a good distinguishing ability between oils belonging to the same broad class, but it is not a method that can be applied practically in remote sensing studies either for the same reason as that mentioned above for the synchronous scan fluorescence technique.
The laser-induced fluorescence technique that promises a good distinguishing ability and, at the same time, a practical remote sensing application is the time-resolved laser-induced fluorescence, technique. The suggestion of this technique as a tool for oil characterization was made as early as 1971 by Fantasia et al(See J. F. Fantasia, T. M. Hard, and H. C. Ingrao. Report No. DOT-TSC-USCG-71-7, Transportation Systems Center, Dept. of Transportation, Cambridge, Mass. (1971) and J. F. Fantasia and H. C. Ingrao. Proc. Of the 9
th
Intern. Symp. On Remote sensing of the environment, Ann Arbor, Mich., Apr. 15-19, 1974, Paper 10700-1-X, 1711-1745)), who recommend the use of lifetime measurements as an additional tool for crude oil characterization.
Immediately thereafter, Measures et al(See Measures et al., “Laser Induced Fluorescent Decay Spectra, A New Form of Environmental Signature.” Optical Engineering, vol. 13 pp. 494-501 (1974) and Measures et al. “Laser Induced Spectral Signatures of Relevance to Environmental Sensing.” Canadian Journal of Remote Sensing, vol. 1, No. 2, pp. 95-102 (1975)) conducted experiments to study the variation of the fluorescence decay time as a function of wavelength across the emission profile for a variety of materials.
They concluded that, in the case of a complex mixture of molecules, this variation could be used to discriminate between very similar substances, i.e., it could be used as a tool for true fingerprinting. Camagni et al(See Camagni et al. “Diagnostics of Oil Pollution by Laser Induced Fluorescence.” IEEE Transactions on Geoscience and Remote Sensing, vol. GE-26, No. 1, pp. 22-26 (1988) and Camagni et al. “Fluorescence Response of Mineral Oils: Spectral Yield vs Absorption and Decay Time.” Applied Optics, vol. 30, No. 1, pp. 26-35 (1991)) did one of the early applications of this technique in remote sensing in the mid 1980's. They used a pulsed laser of 4-ns pulse width to excite the fluorescence spectra of crude oils and then aimed at drawing a r
Hamdan Abdullah M.
Hegazi Ezzat M.
Mastromarino Joseph N.
Courson Tania C.
Gutierrez Diego
Litman Richard C.
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