Radiant energy – Invisible radiant energy responsive electric signalling – Ultraviolet light responsive means
Patent
1996-06-18
1999-01-19
Glick, Edward J.
Radiant energy
Invisible radiant energy responsive electric signalling
Ultraviolet light responsive means
250379, 250382, 250423P, G01N 23227
Patent
active
058616292
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns a method of and a device for the quantitative detection of material in a sample. The material is in the form of submicrometric particles covered by a photoemitting substance.
Such a method and device would be useful in many applications, for detecting how much coal there is in a fuel that is to be burned for example or how much organic material there is in a foodstuff or other sample.
Obtaining surface-specific information about floating particles by measuring photoemission is known from German 3 422 054 C2. The procedure comprises the quantitative detection of substances that evaporate off the particles at a specific temperature. The signal detected in the photoemission section of the apparatus is employed as a measure of how much material has precipitated onto the surface of the aerosol.
One object of the present invention on the other hand is to provide a method that will allow detection of the proportion of the material the sample consists of. Another object of the present invention is a device for carrying out the method.
The first object is attained in accordance with the present invention in that the material in the sample is heated to a photoemitting state and subjected while in that state to photoemission measurement, and the proportion of material in the sample is determined from the signal obtained from that measurement in conjunction with empirical data obtained from a reference sample containing a previously detected quantity of the material or by using data obtained for the material by calibration.
Research (cf. the discussion of the figures hereinafter) has demonstrated that there is a direct relationship between the signal obtained from a photoelectric aerosol sensor and the proportion of material in a sample, assuming that the material is covered with a photoemitting substance.
To convert it into a photoemitting state it can be practical to first treat the material in the sample mechanically, to grind it for example. It may also be useful to dilute the sample before or during the heat treatment that generates the photoemitting state by adding an appropriate form of non-emitting inert solid.
In one alternative of the method an additional support in the form of an inert solid can be added to the sample before or during the heat treatment. The additional support is intended to adsorb the substance that generates the signal and is optionally present in the form of a vapor and to make it accessible to measurement.
It can also be practical to add a carrier, an inert gas for example, to the sample.
If the sample has been properly prepared, the material can be continuously submitted to photoemission measurement and a corresponding continuous result signal obtained.
If the sample contains more than one photoemitting material, some or all of the sample can be converted into different photoemitting states and submitted to photoemission measurement, with empirical data obtained from corresponding reference samples or corresponding data obtained from calibration being taken into consideration during quantitative detection of the materials.
If the material is an organic material and the photoemitting substance that covers the submicrometric particles is a poly-aromatic hydrocarbon, it will be practical to heat the sample to 600 to 1000.degree. C. and preferably to 750 to 850.degree. C. to convert it to a photoemitting state.
The quantitative detection method of the present invention for detecting the proportion of a material in a sample, can be used in various ways. For example, if the measurement is continuous, the empirical signal can be used as a control signal for controlling or regulating a combustion process.
In another approach to applying the method in accordance with the present invention, the result of the detection of the material can be employed to verify the quality of the sample (a foodstuffs sample for example).
An appropriate device for quantitative detection features a photo-detecting sensor that emits an electric empirical signal, a unit upstream of the s
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Weeks et al, "Interaction of TEA CO.sub.2 Laser Radiation with Aerosol Particles", Applied Optics, 15 (11), pp. 2917-2921, Nov. 1976.
Burtscher et al, "Probing Aerosols by Photoelectric Charging", J. Appl. Phys., 53(5), pp. 3787-3791, May 1982.
Hackfort Helmut
Hinzen Georg
Forschungszentrum Julich GmbH
Glick Edward J.
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