JPH0679021B2 - Diffusion collector - Google Patents

Description

FIELD OF THE INVENTION The present invention relates to the fact that the substance to be detected is collected in a sorption layer arranged in an open casing on at least one side, in front of which a high value equal to at least 3 is reached. The present invention relates to a diffusing collector having a structure provided with a relaxation section having a S / width ratio.

2. Description of the Related Art In order to monitor the concentration of harmful substances in a workplace or the like, there is known a diffusion collection device of a type in which mass evaluation or measurement color evaluation of a substance to be detected is performed at the end of a measurement step. In this case, the substance to be detected diffuses from the stationary or moved ambient atmosphere to the sorption layer through a relaxation section that tries to eliminate the direct action of the air flow on the surface of the sorption layer. This results in the deposition or reaction of the substance which forms the basis of the subsequent chemo-analytical quality measurement or optical substance measurement, for example by color change.

In the case of a plate-type diffusion collector, a decrease in discoloration occurs at the center of the plate during the collection stage from a stationary ambient atmosphere, because the sorption layer relaxes the substance to be detected very rapidly. This is because the substance to be detected which has been removed from the substrate and consequently diffuses aside through the edge of the casing opening is selected for the detection layer, especially in the edge region. In contrast, the depleted central region is poorly replenished.

The known diffusion collection device is described in West German Patent Application Publication No. 3445638.
, West German Patent No. 3012380 and West German Utility Model No. 851
No. 0497.

FIG. 3 of Canadian Patent No. 1157355 shows a diffusing collector having a ring-shaped diffusing layer. In this case, the substance to be detected flows radially outward from the empty central space covered by the membrane, resulting in an expanding ring-shaped discoloration zone, where the discoloration limit diameter acts. It increases with time.

In the case of all diffusive collectors of this kind, a certain proportion of the height / width of the relaxation zone is kept if one wishes to avoid the undesired direct action of the flow of the substance to be detected on the surface of the sorption layer. Have to be drunk. In this regard, several authors (eg Sheldon R. Coleman Am.Ind.Hyg.Assoc.I.44
(9) See page 632), a ratio of the height / width of the relaxation section that is larger than 3 is proposed. Maintaining such a ratio results in an undesirably high overall height in the case of the known cylindrical construction of the diffusion collector without the covering. In order to keep the height / width ratio of the above values for a conventional plate construction with a diameter of about 4 cm, a cylinder height of 12 cm would have to be chosen. Such a diffusion collector is poorly operated during actual use.

The problem to be solved by the invention is to provide a diffusive collection device which, despite its small overall height, at the same time allows an advantageous dimensioning of the relaxation zone and thus also an actual plate-like configuration. Start from. The invention also aims at obtaining a simple and compact overall structure of the diffusion collector and a short response time.

Means for Solving the Problems The problem is solved in that the casing and the relief section are groove-shaped with a center line bent or folded in at least one direction.

Such a groove-like configuration makes it possible to maintain an advantageous value for the height / width ratio of the relaxation zone, but this does not mean that an unfavorable overall height is tolerated.

Further, the surface area of the sorption layer is arranged so that a large amount of the sorption layer that can be covered by the diffusing substance to be detected is divided along the edge region so that it can be always used. No discoloration reduction zone occurs in the central region of the sorption layer.

The construction and the geometrical arrangement of the relaxation zone and the casing can be done in different ways. It may be advantageous to construct the grooved casing and the relief section in a closed cross-section, for example as an annulus or an ellipse. In this case, it is also advantageous if several grooved casing parts with closed cross-section are arranged concentrically.

Furthermore, the grooved casing is preferably constructed of straight sections, the central line forming a zigzag shape for each of these sections. Another particularly advantageous embodiment of the grooved casing exhibits a centerline spiral pattern.

In both embodiments, it is advantageous to provide a sufficient distance between the groove-forming parts along the opposite wall parts.

In this case, a coverless sorption layer can be used very advantageously. By sorption layer is meant any of the various known absorption layers, for example activated carbon, on which the analyte can be deposited by adsorption or absorption with the aid of diffusion and adhesion. It may be advantageous to use activated carbon and similar surface-active substances which have a pumping action on the harmful substances to be detected.

According to an advantageous dimensioning, in the case of an annular construction of a grooved casing having an outer diameter of less than 100 mm, it is possible for the difference between this outer diameter and the inner diameter of the grooved casing to be between 5 and 40 mm. .

For example, 33 μg / (ppm ・
If a collection rate of h) is required, a 12.8 cm surface cross section of the sorption layer is required for a diffusion collector. The outer diameter of the diffusion collector, which should be configured as a plate, is 51 mm and the inner diameter is
If the distance is 31 mm, the space between the chamber walls of the grooved casing is 10 mm.
Becomes This spacing determines the height of the diffusing collector. As mentioned above, the value of the ratio of height / width of the relaxation section is required to be 3: 1. The height is thus 30 mm, which results in a plate-like arrangement with advantageous service properties as a whole.

EXAMPLES The present invention will be described in detail with reference to the drawings illustrating examples.

In the case of the embodiment according to FIGS. 1 and 2, a diffusing collector having a plastic casing 1 is shown, the casing of which comprises a cylindrical outer wall 2 and likewise a cylindrical inner wall 3. Have been identified. The bottom part 4 is integrally molded with the walls 2, 3 mentioned above and optionally has fixing elements known per se, such as clips, for attaching the diffusing and collecting device to clothes. An uncovered sorption layer 5 of activated carbon is provided as a bottom layer in a grooved casing formed between the outer wall 2 and the inner wall 3 and is then analyzed by a laboratory method. The evenly bent centerline is denoted by M.

A relaxation zone S is formed in the upper part of the sorption layer 5 of the grooved casing, and the value of the height H / width B is equal to the advantageous value 3 already detailed.

FIG. 3 shows an embodiment which is constructed in the same way as in FIGS. 1 and 2, but in this case a diffusing collector having the angular shape of the grooved casing 1 is formed. The center line M ₁ also forms a rectangle.

FIG. 4 shows a zigzag configuration of the grooved casing 1. In this case, the center line M ₂ also has a zigzag shape.

FIG. 5 shows a spiral configuration of the grooved casing 1, which likewise has a spiral centerline M ₃ .

A diffusion collector of this kind can be used by being filled with activated carbon in order to measure, for example, acetone, benzene, and xylol (ortho) components in the air.

In some cases, the bottom surface of the bottom 4 of the grooved casing 1 is advantageously perforated, so that before the subsequent chemical analysis of the sorption layer it is possible to supply water vapor for discharging the components deposited by deposition. it can.

Even though the embodiment having an exposed sorbent layer on the surface is the preferred configuration, it may be advantageous for certain applications to cover the surface with a membrane or other protective film permeable to the substance to be detected. Will. The use of an uncovered sorption layer has the advantage of avoiding the disadvantages caused by the membrane, such as temperature dependence, longer response times, etc.

[Brief description of drawings]

1 is a longitudinal cross-sectional view of a diffusing collector having a ring-shaped casing, FIG. 2 is a top view of the device shown in FIG. 1, and FIG. 3 is a top view of another structure having an angled casing. The figure shows a top view of an embodiment with a zigzag casing, fifth
The figure is a top view of an embodiment with a spiral casing: 1 ... Casing, 5 ... Sorption layer, S ... Relaxation section

Claims (8)

[Claims] 1. A relaxation zone, in which the substance to be detected is collected in a sorption layer arranged in an open casing on at least one side and in front of said layer having a height / width ratio equal to at least a value of 3. In the diffusing and collecting device having the structure described above, the casing (1) and the relaxation section (S) are bent or folded in at least one direction to form a center line (M, M ₁ , M ₂ ,
The diffusion collecting device is characterized in that it is formed in a groove shape by M ₃ ). 2. Device according to claim 1, wherein the grooved casing (1) and the relaxation section (S) have a closed cross-section. 3. The device as claimed in claim 2, wherein the grooved casing (1) and the relaxation zone (S) are annular. 4. Device according to claim 2, wherein several grooved casing parts (1) having a closed cross-section are arranged concentrically. 5. A device according to claim 1, wherein the grooved casing comprises a straight section. 6. The apparatus of claim 1 wherein the grooved casing has a centerline curvature varying portion. 7. The device according to claim 1, wherein an uncovered sorption layer is arranged in the grooved casing. 8. The device according to claim 3, wherein the difference between the outer diameter and the inner diameter of the groove-shaped casing (1) is 5 to 40 mm when the outer diameter is less than 100 mm.