Sampling pad

Abstract

A versatile sampling pad (1) for receiving an adsorption granulate (5) for a thermal desorption device has the following features: a) the sampling pad (1) includes an internally arranged receiving disc (10), b) the receiving disc (10) has flow-through recesses (11) which can be filled with the adsorption granules (5), c) A first filter mesh disc (20) is located on the first end face of the receiving disc (10) and a second filter mesh disc (30) is located on the second end face of the receiving disc (10) to fix the adsorption granules (5), d) a first end-hole disk (40) and a second end-hole disk (50) sandwich-like and protectively surround the receiving disk (10) enclosed by the first filter mesh disk (20) and the second filter mesh disk, e) the first end face disk (40) and the second end face disk (50) each have flow-through recesses which, in an assembled position, are aligned with the flow-through recesses (11) of the receiving disk (10), f) the receiving disk (10), the first filter mesh disk (20), the second filter mesh disk (30), the first end-hole disk (40) and the second end-hole disk (50) are connected to each other in an assembled position via a detachable connection.

Description

[0001] The invention relates to a sampling pad for adsorption of volatile substances and subsequent desorption by means of a thermal desorption device.

[0002] The applicant uses a measuring instrument manufactured by Karsa Oy. The instrument is a TARKKA APCI-TOF-MS with an upstream thermal desorption unit. A specific sampling device, also manufactured by Karsa Oy, is available for this instrument. The sampling device is a mesh filter disc. The mesh filter disc is a flexible disc made of stainless steel wire mesh and has an outer diameter of 37 mm. The mesh filter disc is coated with Tenax® TA. The coating was obtained by liquid coating with Tenax® TA dissolved in dichloromethane, followed by evaporation of the solvent. This resulted in a thin Tenax® TA film on the mesh filter disc, which, however, is very thin and unevenly distributed due to this manufacturing method. Tenax® TA is a polymeric adsorption resin used for the adsorption of volatile substances, such as chemical warfare agents and TICs.The flexible mesh filter disc is placed in a filter cassette specially manufactured for the desorption unit to ensure easier handling. The filter cassette with the mesh filter disc inside is used for both sampling and measurement.

[0003] From DE 10 2009 023 636 B3, a sampling cylinder for receiving adsorption granules for a thermal desorption device is known. The sampling cylinder has two outer, protective end plates with a plurality of flow-through openings. The interior of the sampling cylinder receives adsorption material, for example, MIF granules.

[0004] From DE 10 2007 048 185 A1, a device for measuring volatile organic compounds (VOCs) using the enrichment and desorption method is known. A desorption unit comprises a chamber filled with an adsorption material. The adsorption material consists of microinjectable particles (MIPs) with a particle size of 100 to 200 micrometers. A sieve with a mesh size of less than 90 micrometers retains the MIP particles in the desorption unit.

[0005] A sampling pad for gas analysis of ambient air for the presence of radon or thoron is known from CN 2 03 132 886 U. The sampling pad comprises a cylindrical shell that can be filled with adsorption granules. A first filter mesh disc rests against the first end face of the cylindrical shell, and a second filter mesh disc rests against the second end face to fix the adsorption granules. A first retaining ring and a second retaining ring sandwich-like enclose the cylindrical shell enclosed by the first and second filter mesh discs. The cylindrical shell, the first filter mesh disc, the second filter mesh disc, the first retaining ring, and the second retaining ring are connected to each other in an assembled position by a detachable connection.

[0006] US Patent 6,063,041 A discloses a sampling pad for collecting volatile compounds from a perfume composition applied to the skin. The sampling pad for a thermal desorption device comprises a lid that can be filled with adsorption granules. A filter mesh disc is arranged in the lid to fix the adsorption granules. For sampling, the pad is assembled such that the lid is connected to a spacer sleeve, the open end of which is directed towards the skin.

[0007] The invention is based on the objective of creating a sampling device that represents an alternative to the prior art with new fields of application.

[0008] This problem is solved according to the invention by the features in claim 1.

[0009] The advantages of the invention are described below. The sampling pad is reusable. Furthermore, the sampling pad is dimensionally stable. This facilitates handling during sampling. Sampling is also possible in harsh and adverse environments. Sampling can be performed actively or passively.

[0010] In active sampling, a defined airflow, generated by a portable pump, is used to pass through the sampling pad containing the adsorption material. In passive sampling, the gas mixture under investigation has free access to the adsorption material. Specifically, a sampling pad for a thermal desorption unit consists of a receiving disc with flow-through recesses, which can be filled with adsorption material. The required amount of adsorption material can be precisely adjusted by weighing the necessary quantity of granules before filling. The first filter screen rests against the first end face of the receiving disc, and the second filter screen rests against the second end face to secure the adsorption granules.To ensure that the adsorption granules remain within the flow-through openings, filter mesh discs are attached to the end faces of the receiving disc. These two filter mesh discs secure the adsorption material and allow the gas mixture under investigation access to the adsorption granules. The first and second end face discs sandwich and protect the receiving disc, which is enclosed by the first and second filter mesh discs. Both end face discs have flow-through openings that, when assembled, align with the openings of the receiving disc. This allows the gas mixture under investigation unobstructed access to the adsorption granules.The sampling disc, the first filter mesh disc, the second filter mesh disc, the first end-hole disc, and the second end-hole disc are connected to each other in an assembled position via a detachable connection. This allows for easy disassembly of the sampling pad, for example, to fill it with a different adsorption material. For repeated gas sampling, the sampling pad can be baked out after measurement without having to disassemble it.

[0011] The first end-hole plate has an outer collar which, in the assembled position, holds the mounting plate (enclosed by the first and second filter mesh plates) and the second end-hole plate. The outer collar serves to center the mounting plate, the first filter mesh plate, the second filter mesh plate, and the second end-hole plate during assembly.

[0012] According to one embodiment of the invention, the first end-hole plate has an outer collar whose inner dimension is designed to form a clamping connection with the outer dimension of the second end-hole plate. This clamping connection has the advantage that the sampling pad can be attached without tools.

[0013] According to a further embodiment of the invention, the first filter mesh disc, the second filter mesh disc, the receiving disc, the first end-hole disc, and the second end-hole disc are each made of stainless steel. Stainless steel exhibits high strength. Furthermore, stainless steel is resistant to weathering and environmental influences. The stainless steel components of the receiving pad are reusable, require minimal cleaning, are resistant to chemicals, and are temperature-resistant. This allows the sampling pad to be used for sampling regardless of weather or location. Furthermore, high temperatures are possible during the subsequent thermal desorption analysis.

[0014] According to a further embodiment of the invention, the first end-hole disk, the second end-hole disk, and the receiving disk are secured against rotation relative to each other in a concentrically assembled position by a positive-locking anti-rotation device. This serves as an assembly aid. Furthermore, it ensures that the arrangement of the aligned flow-through recesses is maintained during the subsequent sampling and analysis.

[0015] According to a further embodiment of the invention, the sampling pad, in its assembled position, has an outer diameter of 36 to 38 mm and a thickness of 1 to 3 mm. This has the advantage that commercially available thermal desorption devices can be used. Furthermore, the use of commercially available active sampling devices that support such a geometry is possible.

[0016] An embodiment of the invention is explained in more detail below with reference to the drawings. These show: Fig. 1 a recording pad in longitudinal section and a perspective addition of half the profile; Fig. 1a an enlarged representation of the in Fig. 1 detail shown aa; Fig. 2 the sampling pad shown in Fig. 1 as an exploded view, derived from a photograph.

[0017] The Fig. 1, the Fig. 1a and the Fig. Figure 2 shows a sampling pad 1 with a captured adsorption granulate 5 for sampling and subsequent thermal desorption in a desorption device, as described above.

[0018] The sampling pad 1 comprises an internally arranged receiving disc 10. The receiving disc 10 has flow-through recesses 11 filled with the adsorption granules 5. The first filter mesh disc 20 rests against the first end face of the receiving disc 10, and a second filter mesh disc 30 rests against the second end face of the receiving disc 10 to fix the adsorption granules 5. The first end-face disc 40 and a second end-face disc 50 sandwich-like and protectively enclose the receiving disc 10, which is enclosed by the first filter mesh disc 20 and the second filter mesh disc. The first end-face disc 40 and the second end-face disc 50 each have flow-through recesses 41 and 51, which, in an assembled position, are aligned with the flow-through recesses 11 of the receiving disc 10.The receiving disc 10, the first filter mesh disc 20, the second filter mesh disc 30, the first end-hole disc 40, and the second end-hole disc 50 are connected to each other in an assembled position by a detachable connection. The first end-hole disc 40 has an outer collar 45 which, in the assembled position, holds the receiving disc 10 (enclosed by the first filter mesh disc 20 and the second filter mesh disc 30) and the second end-hole disc 50. In the assembled position, an outer surface 56 of the second end-hole disc 50 and an inner surface 46 of the outer collar 45 of the first end-hole disc 40 form a clamping connection. The first filter mesh disc 20, the second filter mesh disc 30, the receiving disc 10, the first end-hole disc 40, and the second end-hole disc 50 are each made of stainless steel.The first end face disk 40, the second end face disk 50 and the receiving disk 10 are secured against rotation in the assembled position by a positive locking anti-rotation device (not shown).

[0019] The sampling pad 1, in its assembled position, has an outer diameter of 37 mm and a thickness of 2 mm. This allows the filter cartridge for the thermal desorption unit to be used with the TARKKA-TOF-MS. In addition to the sampling devices supplied by Karsa Oy, other commercially available sampling systems can also be used, such as GSA sampling devices for hazardous substance measurement.

[0020] In active sampling, for example, a precisely defined volumetric flow is passed through a sampling pad coated with adsorption granules for a duration of one minute using a sampling pump. This facilitates the quantitative determination of the total concentration of chemical warfare agents. Active sampling is suitable for measurements following an explosion, for example, when large quantities of hazardous chemicals are released, in order to assess the level of risk.

[0021] Passive sampling, unlike active sampling, is used to assess the risk to a soldier. A possible scenario involves the discovery of a buried grenade from World War II. There is a suspicion of a chemical warfare agent leak. Explosive ordnance disposal (EOD) soldiers each wear a sampling pad in a holder, attached, for example, to the outside of their clothing or equipment, which remains passively exposed to the ambient air throughout the entire operation. After the operation, the samples are analyzed in a laboratory to determine whether the EOD soldiers have been contaminated.

[0022] In contrast to the illustrated embodiment, the following modifications are possible: • In the exemplary embodiment, the receiving disk 10, the first end-hole disk 40, and the second end-hole disk 50 each have seven flow-through recesses 11 in the form of bores. Alternatively, the flow-through recesses 11 could also be milled elongated slots. Likewise, the number of flow-through recesses can differ from the exemplary embodiment. However, there should be at least two to ensure proper function. A maximum of fifteen flow-through recesses is recommended to enable cost-effective manufacturing. • In the exemplary embodiment, the adsorption material is rather fine-grained. However, the properties of the adsorbent can vary, but must not be smaller than the diameter of the openings in the stainless steel mesh, otherwise there is a risk that adsorption material will leak out of the sampling pad. • As long as compatibility with commercially available thermal desorption equipment and sampling devices is ensured, the outer diameter can also be in the range of 36-38 mm and the thickness in the range of 1 to 3 mm. Reference symbol list 1 sampling pad 5 Adsorption granules 10 Recording disc 11 Flow-through recess in receiving disc 20 first filter mesh disc 30 second filter mesh disc 40 first face plate 41 Flow-through recess of the first end face 45 Outer collar 46 inner surface of the collar 50 second face plate 51 Flow-through recess of the second end plate 56 Outer surface of the second end face disk

Claims

[1] Sampling pad (1) for a thermal desorption device, having the following features: a) the sampling pad (1) comprises an internally arranged receiving disc (10), b) the receiving disc (10) has flow-through recesses (11) which can be filled with an adsorption granulate (5), c) a first filter mesh disc (20) is located on the first end face of the receiving disc (10) and a second filter mesh disc (30) is located on the second end face of the receiving disc (10) in order to fix the adsorption granulate (5), d) a first front hole disc (40) and a second front hole disc (50) sandwich and protect the receiving disc (10) encompassed by the first filter mesh disc (20) and the second filter mesh disc (30), e) the first end-hole disc (40) and the second end-hole disc (50) each have flow-through recesses (41, 51) which, in an assembled position, are aligned with the flow-through recesses (11) of the receiving disc (10), f) the receiving disc (10), the first filter mesh disc (20), the second filter mesh disc (30), the first face hole disc (40) and the second face hole disc (50) are connected to one another in an assembled position via a detachable connection, g) the receiving disc (10), the first end-hole disc (40) and the second end-hole disc (50) each have two to seven flow-through recesses (11, 41, 51), h) the first front hole disc (40) has an outer collar (45) which, in the assembled position, holds the receiving disc (10) encompassed by the first filter mesh disc (20) and the second filter mesh disc (30) and the second front hole disc (50). [2] Sampling pad (1) according to claim 1, wherein in the assembled position an outer circumferential surface (56) of the second end-hole disc (50) and an inner circumferential surface (46) of the outer collar (45) of the first end-hole disc (40) form a clamping connection. [3] Sampling pad (1) according to one of claims 1 or 2, wherein the first filter mesh disc (20), the second filter mesh disc (30), the receiving disc (10), the first end hole disc (40) and the second end hole disc (50) are each made of stainless steel. [4] Sampling pad (1) according to one of claims 1 to 3, wherein the first end hole disc (40), the second end hole disc (50) and the receiving disc (10) are secured against rotation relative to one another in the assembled position by means of a positive rotation lock. [5] Sampling pad (1) according to one of claims 1 to 4, wherein the sampling pad (1) in the assembled position has an outer diameter in the range of 36 to 38 mm and a thickness in the range of 1 to 3 mm.

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