Optics: measuring and testing – By dispersed light spectroscopy – With sample excitation
Patent
1987-12-01
1989-04-25
LaRoche, Eugene R.
Optics: measuring and testing
By dispersed light spectroscopy
With sample excitation
356314, 364498, G01J 330
Patent
active
048242497
DESCRIPTION:
BRIEF SUMMARY
This invention relates to systems for the direct analysis of solid samples by atomic emission spectroscopy.
The use of spectroscopy for the analysis of samples is widely practised using atomic absorption, atomic emission or atomic fluorescence techniques in the spectroscopic analysis of a sample.
The most widely used elemental analysis techniques are atomic emission and atomic absorption and both techniques have well-known advantages and disadvantages. While the atomic absorption technique is relatively inexpensive, using simple instrumentation, performs rapid measurements, can be automated, is accurate and sensitive for many elements, and gives total elemental concentrations, little success has thus far been achieved in multi-elemental analysis, the sample must in most cases be in solution so that the technique is therefore destructive, elemental sensitivities vary from element to element, the technique is subject to sample matrix interference so that samples and standards must be matrix matched for accurate work, if the temperature of the flame is not sufficiently high, molecular spectral interference may occur due to incomplete sample break down, the technique is limited to operation in the visible region which eliminates its application to many electronegative elements and the concentration range covered is small (1 to 2 orders of magnitude) requiring sample dilution which can cause errors.
In the case of the atomic emission technique, the major advantages include: the technique may be is truly multi-elemental and simultaneous in its operation, most elements can be measured using ultra violet-visible optics, a wide range of samples can be handled, concentration ranges of five orders of magnitude can be covered, instrumentation is relatively simple and reliable, the instruments can be automated, analytical sensitivity is high, complete sample break down occurs and interferences are restricted to those caused by spectral resolution limitations, and the technique has sub parts per million sensitivity. On the other hand, the principal disadvantages of the atomic emission technique include the requirement for a thermally and physically stabilised high resolution spectrometer, the requirement for complete sample destruction, the matrix dependence of arc/spark analysis and the inaccuracies introduced thereby, the requirement for complete sample decomposition when using inductively coupled plasma which can be difficult with inert materials, the inability to distinguish between isotopes due to Doppler broadening, and the requirement for a power supply of the order of 10 kW.
The ability to rapidly and inexpensively analyse geological exploration samples is important to mining companies. Similarly, it is most important to mining companies to be able to analyze for isotopic information, particularly in the heavier elements such as lead and uranium. At the present time, the principal technique used is ion mass spectrometry which is time consuming, also involves wet chemistry, and therefore expensive with a maximum throughput of the order of 6 samples per day being common.
It is an object of the present invention to provide a system for the analysis of samples using atomic emission spectroscopy which suffers from fewer of the above described disadvantages, and more specifically, enables rapid and relatively inexpensive isotopic analysis.
Accordingly the present invention provides an analysis system for analysis of samples by atomic emission spectroscopy comprising an atomic spectral lamp adapted to receive a solid sample to be analysed as a cathode of said spectral lamp; means for producing a primary electric discharge by cathodic sputtering from said sample, means for passing an inert gas through said spectral lamp; means for producing a secondary boosted discharge for analytical emission; spectral wave length analysis means arranged to receive and determine intensity of spectral lines emitted from said spectral lamp; and control means including means for controlling cathodic sputtering current used for generating
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Hughes Terry C.
Lucas Michael A.
Chamber Ridge Pty. Ltd.
Ham Seung
Jeffers Albert L.
LaRoche Eugene R.
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