Chemistry: analytical and immunological testing – Including sample preparation
Patent
1987-08-20
1989-09-19
Richman, Barry S.
Chemistry: analytical and immunological testing
Including sample preparation
422 99, 422101, 422 63, 118309, G01N 100
Patent
active
048681288
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a process for dry dispersal of particles, and an instrument for dry dispersal of particles for producing on specimen slides a random, homogeneous fine distribution (a dispersal) of dry, fine, grainy bulk materials whose particle size distributions can be analyzed, for example, by means of automatic image analysis.
It is known that particles whose particle size distribution is to be determined by optical means through automatic image analysis must be dispersed perfectly in order to avoid so-called agglomerates (clotting-together of individual particles). Such agglomerations give rise to assessment errors and incorrect measurements. Likewise, two particles touching by chance on the specimen slide likewise simulate a (single) particle which is too large. In order to avoid these errors, it was hitherto necessary to apply the particles in highly dilute form - i.e. with a relatively large separation between the individual particles - to the specimen slide. However, the number of particles covered per image field is then impermissibly small or the evaluation times are too long. Fine powders cannot be formed on the specimen slide without agglomeration using conventional methods. The object of the present invention is therefore to provide a process and an instrument with which it becomes possible to disperse, in optimum fashion, fine, dry, grainy bulk goods (powders, dusts) and to apply them in the densest possible form onto a specimen slide, without the particles touching one another, so that such substances become more accessible for particle size determination by means of automatic image analysis.
BRIEF DESCRIPTION OF THE DRAWING
The drawing shows schematically an illustrative embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
An enclosed space, designated as a turbulence chamber 4, in the form of a longitudinally prismatic hollow element contains, in the region of its top plate 10, a connector with a connecting line to a vacuum pump 9. When this vacuum pump is operated, a certain partial vacuum can be produced and maintained in the turbulence chamber 4. A distributor tube 7, which is connected, at its externally facing end region, directly to an accelerator tube 5, which has a shut-off valve 11, projects into the turbulence chamber 4. At the distal end of the accelerator tube 5 is located a trough-like or dish-like sample container 1 for the powder-like sample substance 2. The base plate 8 of the turbulence chamber 4 can be removed and has a circumambient vacuum-tight flange. On the base plate 8 is located at least one specimen slide 3. In the case represented, the cross-section of the turbulence chamber 4 and the cross-section of the distributor tube 7 is rectangular. However, other cross-section geometries are also possible. It is likewise possible for the distributor tube to have a cross-section which varies along its entire length. The axis of the distributor tube 7 can also be inclined to the axis of the vertical turbulence chamber 4; it is also possible for the part of the distributor tube 7 projecting into the turbulence chamber 4 to be variable in respect to its length.
According to a particularly expedient embodiment, a baffle 6, which can have a variable inclined position with respect to the vertical axis of the distributor tube 7 and the horizontal axis of the accelerator tube 5, is located in the end region of the distributor tube 7 leading to the outside.
The course of the process according to the invention is as follows: the sample container 1 is charged with a metered amount of a powder-like sample substance 2. The shut-off valve 11 is closed; with the pump valve 12 open, the vacuum pump 9 has produced a partial vacuum in the turbulence chamber 4, and this is maintained by closing the pump valve 12. If the shut-off valve 11 is now opened, a stream of air is drawn through the accelerator tube and then through the distributor tube. The stream of air carries the powder-like sample substance 2 along at a high speed, s
REFERENCES:
patent: 2209614 (1940-07-01), Rowley
patent: 2862889 (1958-12-01), Mitchell
patent: 3362405 (1968-01-01), Hazel
patent: 3472202 (1969-10-01), Webb
patent: 3587523 (1971-06-01), Tudor et al.
The Leitz Autoscope P-the new problem solution for automatic particle analysis; Scientific and Technical Information, Achema 1985, Special Issue, pp. 22-25.
Bohnaus Ulrich
Fath Rolf
Peschke Walter
Sommer Karl
Ernst Leitz Wetzlar GmbH
Richman Barry S.
Wallen T. J.
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