Radiant energy – Invisible radiant energy responsive electric signalling – Infrared responsive
Patent
1991-10-07
1994-06-28
Fields, Carolyn E.
Radiant energy
Invisible radiant energy responsive electric signalling
Infrared responsive
25033901, G01N 2101, G01N 2147
Patent
active
053249496
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method of carrying out analyses of materials by the NIR-principle or corresponding principles of analysis.
BACKGROUND OF THE INVENTION
NIR stands for Near Infrared Reflection and designates a method of analysis, in which the contents of various components of materials, e.g., water and protein, can be determined by a quite brief infrared irradiation of a sample portion of a few grams of the material. NIR analysis devices for general laboratory applications, e.g., in feedstuff factories or mixing establishments, have already been developed.
In the use of such devices, a homogenized sample of a few cubic centimeters is placed in a particular test cup, which is then mounted against a quartz disc on an analyzer head of the device, from which the surface of the sample is irradiated; the reflected rays are picked up by a particular detector which supplies electrical signals representative of the various components of the material. Before the next analysis, the equipment must be cleaned carefully, usually by washing with an organic solvent, as remnants of the material sample in the test cup or on the quartz disc may cause the next analysis to be inaccurate.
SUMMARY OF THE INVENTION
Said method is very advantageous compared to conventional methods, but like conventional methods, said method has hitherto not been suited for a still more advantageous application, i.e., in connection with automatic on-line sample analysis and automatic process control. The present invention aims at providing a method and an apparatus for carrying out the method, which makes such an application possible, whereby it will be possible to perform analyses in rapid succession in a fully automatic manner.
According to the present invention, use of the small test cup is abandoned and instead a considerably larger test chamber is used in front of the analyzer head, it being recognized that in the desired manner of operation, it will be unrealistic to perform washings with organic solvents or other clean-up procedures between the analyses. Instead, an aim of use of a larger chamber is to make remnants from a preceding sample so proportionally insignificant that the inaccuracy caused thereby can be kept within practically acceptable limits.
It must be possible to introduce the material into the test chamber and to discharge the material from the test chamber in such a manner that successive samples can be analyzed with a reasonably high frequency in order that the least possible remnant of each sample is left in the test chamber. Particularly in the case of non-homogeneous solid substances, a suitable homogenization must be provided, that is, in such a manner that a successively used homogenizer ahead of the test chamber does not retain essential remnants of the treated material, which, could cause a considerable pollution of the subsequent sample portion or portions. In connection with the present invention, it has been realized that under these circumstances it will hardly be possible to operate with a real homogenization or fine grinding of the material, but also that the problem can be solved in another way which is discussed herein.
The radiation used in the analysis is reflected mainly from the surface of the sample material, but the rays have a certain depth of penetration into the material so that the area essential to the analysis will be the surface layer bearing against the quartz disc of the analyzer head, the thickness of said layer being larger or smaller depending upon the nature of the material; however, the thickness of said layer is generally only a few millimeters, which accounts for the fact that it has been possible to use quite small samples. At the same time, however, this also accounts for the fact that use of a relatively large test chamber, in which the thickness or depth of the material sample opposite the analyzer head is considerably increased, ensures that a possible remnant of the preceding sample portion at the rear wall of the test chamber opposite
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patent: 4742228 (1988-05-01), Bischoff
patent: 4991949 (1991-02-01), Moorehead
Fields Carolyn E.
Jesma-Matador A/S
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