Optics: measuring and testing – By dispersed light spectroscopy – With sample excitation
Patent
1996-01-29
1997-12-16
Evans, F. L.
Optics: measuring and testing
By dispersed light spectroscopy
With sample excitation
G01N 2167
Patent
active
056991550
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an emission spectral analysis method and an instrument therefor adapted to perform measurement of the kinds and contents of the respective elements contained in an analytical sample.
BACKGROUND ART
In general, according to the emission spectral analysis using a spark discharge or an arc discharge, the spark discharge or the arc discharge is conducted between a sample and a counter electrode so that a part of the sample is vaporized by the discharge energy to excite the vaporized atoms and ions. A transition of these atoms and ions into a lower energy level causes emanation of peculiar spectral lines each having an intensity according to the density of the associated element.
At the place where the spectral lines emanated, there is provided a state of a continuous spectral line in which peculiar spectral lines on the respective elements and scattered light are mixed. The continuous spectral line is introduced into a spectroscope to be spectroscopically dispersed by a diffraction grating installed in the spectroscope, so that peculiar spectral lines on the elements of interest in measurement are detected, respectively. A kind of each of the elements contained in a sample is determined on the basis of the wavelength position thus obtained, whereas a content of each of the elements is determined on the basis of intensity of the spectral line.
Usually, such a detection is performed by detectors (photomultipliers) each of which is disposed on an optimum basis to meet the wavelength of the corresponding spectral line for each element in the spectroscope. Finally, intensity of the detected spectral line, or quantity is subjected to a photometric processing in the form of emission intensity, so that arithmetic on the respective element contents are performed by a computer.
Such an emission spectral analysis instrument comprises: a counter electrode for causing an arc discharge or a spark discharge; an emission stand for holding a sample at a position where the sample is located over said counter electrode; a spectroscope for receiving and spectroscopically dispersing spectral lines emanated from the sample held on said emission stand; and photometric equipment adapted to perform measurement of the kinds and contents of the elements contained in the sample on the basis of the wavelength position thus obtained by the spectroscope and intensity of the spectral lines.
The emission stand is provided with a sample holding member for holding the sample at a position where the sample is located over a tip of the counter electrode. A discharge is performed 1-1000 times/sec. between the surface of the sample and the counter electrode so that atoms and ions, as conversion of the constituent elements of the sample, are excited. A transition of these atoms and ions into a lower energy level causes emanation of peculiar spectral lines each corresponding to the associated element. After spectroscopically dispersing through the spectroscope, kinds and contents of the elements contained in the sample are measured on the basis of the wavelength and intensity of the spectral lines.
According to a discharge type of emission spectral analyzer on the market, since the spectral lines having not more than 200 nm of wavelength are absorbed into air and thus cannot be measured, an atmosphere of inert gas, usually, Ar, He and the like, is provided in the space between an emission unit in which a sample is accommodated and a spectroscope, whereas a vacuum state is provided, usually using a vacuum pump, for the inside of the spectroscope.
The emission stand for setting samples is made of metal having a thickness of 2 mm-3 mm or ceramics in order to provide a suitable strength for holding the samples and the counter electrode for discharge. It happens that this thickness occupies over half of a distance 3 mm-6 mm between the electrode and the sample. Further, there exists vapor emanated from the sample due to a spark discharge. Consequently, an effective portion available for an analysis is m
REFERENCES:
patent: 4289402 (1981-09-01), Teubner
patent: 4544270 (1985-10-01), Berstermann et al.
patent: 4571074 (1986-02-01), Thevenon
Evans F. L.
Kawasaki Steel Corporation
Shimadzu Corporation
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