Electron-capture detector and measuring system

Abstract

The invention relates to an electron-capture detector comprising a detector main part in which a reaction chamber for capturing free electrons is located. The invention also relates to a measuring system, in particular a gas chromatograph, comprising such an electron-capture detector.

Description

[0001] Applicant:

[0002] Gottfried Wilhelm Leibniz University Hannover Corporation under public law Weifengarten 1 30167 Hannover

[0003] Electron capture detector and measurement system

[0004] The invention relates to an electron capture detector comprising a detector body in which a reaction chamber for capturing free electrons is arranged. The invention also relates to a measuring system, in particular a gas chromatograph, with such an electron capture detector.

[0005] Electron capture detectors can be used in various measurement systems. One advantageous application is gas chromatography. Gas chromatography is one of the most widely used analytical methods in chemistry. It involves separating a mixture of substances into its components using a gas chromatography (GC) column, so that these components can be quantified separately in a downstream detector. The characteristic residence time or retention time through the GC column enables the substance to be identified. Electron capture detectors (ECDs) are the preferred GC detectors for analyzing complex trace gas mixtures of electron-affine substances using gas chromatography. ECDs are characterized by fast response, high linearity, and high sensitivity.This makes GC-ECDs particularly suitable for the analysis of pesticides and other environmental pollutants, such as ozone-depleting chlorofluorocarbons (CFCs), so that GC-ECDs are used as a standard method in many laboratories.

[0006] The measurement effect of an ECD is fundamentally based on the electron capture of free electrons in a reaction chamber by an electron-affine substance. The reduction in the initially constant number of free electrons is a measure of the concentration of the electron-affine substance. The generation of free electrons can occur either through the ionization of the neutral carrier gas or a dopant, or through the direct escape of electrons from metals (photoelectric effect) or discrete electron sources. The detection of electrons is achieved by a static or time-varying electric field between two electrodes. The electric field strength and its temporal occurrence must be selected, if necessary in combination with the gas flow velocity, so that only the highly mobile electrons reach the detector electrode, while the less mobile, negative ions do not.A current measuring amplifier connected to the detector electrode records the amount of incident electrons.

[0007] The invention is based on the object of further improving such an electron capture detector.

[0008] This problem is solved by an electron capture detector of the type mentioned above, in which the detector body is constructed predominantly or entirely from one or more electrical circuit boards (also known as printed circuit boards / PCBs). Such a detector body made of one or more circuit boards can be manufactured easily and cost-effectively, particularly using the methods of circuit board manufacturing that are already common today. This allows the electron capture detector to be further miniaturized. The mechanical structure of the detector body can be made very stable using the circuit board construction, so that the electron capture detector can be used without any problems in typical applications.

[0009] In addition, the electron capture detector according to the invention, also referred to as a printed circuit board ECD, can be further improved in terms of functionality and measurement quality. For example, existing metallic conductor layers on the electrical circuit boards can be used for signal transmission from the detector to an evaluation circuit. This ensures very short signal paths and comprehensive shielding by surrounding metallized conductor layers within the circuit board, allowing the electron capture detector to be operated with improved measurement quality and, in particular, with very low interference.

[0010] If the detector body of the electron capture detector is constructed from a single electrical circuit board, the reaction chamber can be designed as a cavity inside the circuit board. This allows for significant miniaturization of the electron capture detector. The cavity can be created during circuit board production. If the detector body is constructed from multiple electrical circuit boards, it is advantageous to connect them together in a sealing manner in order to provide a reaction chamber that is hermetically sealed from the external environment. The multiple circuit boards can, in principle, be connected to one another in any desired manner, e.g., by using six circuit boards that are connected to one another at their narrow sides, thus forming a cuboid.

[0011] The detector body can be constructed entirely of circuit boards. It is also possible to construct the detector body partly from circuit boards and partly from other components.

[0012] The invention described here, hereinafter also referred to as printed circuit board ECD, makes it possible to manufacture electron capture detectors based on printed circuit boards. Printed circuit boards can be obtained inexpensively, with a wide range of materials and short production times from a large number of manufacturers, allowing for high flexibility in structural and functional design. Printed circuit boards are well suited for the construction of analytical instruments. High-temperature requirements can also be met with modern printed circuit board materials, such as special ceramics or ceramic composites, while retaining the extensive design options available to the printed circuit board manufacturers. Furthermore, the required electronic circuits can be implemented directly on the ECD's printed circuit boards.According to current technology, the components of an ECD are manufactured using conventional manufacturing processes, such as injection molding or machining, which is costly and time-consuming. The printed circuit board ECD, on the other hand, offers a time- and cost-saving manufacturing option thanks to a large market of printed circuit board manufacturers.

[0013] According to an advantageous embodiment of the invention, the detector body is formed predominantly or entirely by a plurality of electrical circuit boards that are stacked on top of one another, wherein the reaction space is formed by at least one recess created in one or more circuit boards. The electrical circuit boards are thus not connected to one another by their narrow sides, but by their surface sides, which, in the usual use of a circuit board, serve for applying electronic components. For example, the circuit boards stacked in a stack can be arranged parallel to one another. This creates an electron capture detector that is particularly easy to assemble and is characterized by a robust design. For example, the detector body can be formed from three electrical circuit boards stacked on top of one another.

[0014] According to an advantageous embodiment of the invention, the detector body has a supply opening and a discharge opening, wherein the supply opening and / or discharge opening is formed by at least one through-opening in at least one circuit board of the detector body. The reaction chamber can be connected to the external environment through the supply opening. The reaction chamber can be connected to the external environment through the discharge opening. In this way, the supply lines required for an electron capture detector can be advantageously integrated into the circuit board design of the detector body. A carrier gas containing the substance to be analyzed and, if appropriate, further neutral gas, if appropriate enriched with a dopant, can be supplied to the reaction chamber through one or more supply openings.The substances and gases present in the reaction chamber can be discharged to the outside through the discharge opening.

[0015] According to an advantageous embodiment of the invention, one, several, or all circuit boards of the detector body are designed as high-temperature circuit boards, in particular as circuit boards with circuit board materials such as ceramics or ceramic composites. This further improves the application possibilities of the electron capture detector in many areas of chemical analysis technology, in particular gas chromatography. In this way, such high-temperature requirements can be easily met with modern circuit board materials, while retaining the extensive design options in circuit board production. For example, the detector body can be designed for an operating temperature of up to 300 °C or up to 400 °C.

[0016] According to an advantageous embodiment of the invention, the surface of one, several or all circuit boards of the detector body is completely or partially covered with, for example, an insulating protective layer. This can, for example, insulate the circuit boards from one another. In addition, disruptive effects such as the photoelectric effect can be avoided or at least reduced by such a protective layer. Advantageously, the surface of one, several or all circuit boards of the detector body can be partially or completely covered with a protective layer, such as a varnish, for example the so-called solder mask. Furthermore, coating with functional materials such as metals and / or polymers and / or oxides, which contribute to the function of the ECD, is also conceivable.

[0017] According to an advantageous embodiment of the invention, a desired internal geometry of the reaction chamber is formed at least in part by appropriate structuring of the circuit boards of the detector body. For example, the circuit boards can have continuous millings and / or deep millings in any combination and overlap to form the corresponding internal geometry of the reaction chamber.

[0018] According to an advantageous embodiment of the invention, several or all circuit boards of the detector body are arranged parallel to one another. This allows for a compact and robust construction of the detector body made of circuit boards.

[0019] According to an advantageous embodiment of the invention, one, several, or all circuit boards of the detector body are designed as single-layer or multi-layer circuit boards coated with metallic conductor layers. Such metallic conductor layers can, for example, minimize external interference, since the reaction chamber is shielded from the environment, thereby improving the EMC compatibility of the electron capture detector. Furthermore, the metallic conductor layers, particularly when structured into conductor tracks, can be used for further functional improvements of the electron capture detector, e.g., for the application of electronic components (e.g., soldering) and / or to form the electrodes typically used for an electron capture detector.

[0020] According to an advantageous embodiment of the invention, the electron capture detector has an anode, a cathode, and optionally further auxiliary electrodes, e.g., within the reaction chamber, wherein the anode and / or the cathode and / or optionally further auxiliary electrodes are formed by at least one metallic conductor layer of at least one circuit board of the detector body. This has the advantage that the aforementioned electrodes of the electron capture detector can be realized without additional effort by being produced directly during circuit board manufacture as correspondingly structured conductor layers. This also allows the aforementioned advantages of the inventive electron capture detector in circuit board design, namely short signal paths and a corresponding reduction in interference, to be further optimized.According to an advantageous embodiment of the invention, the electron capture detector has at least one electronic evaluation circuit and / or an electronic control circuit with electronic components that are soldered onto at least one structured conductor layer of at least one circuit board of the detector body. For example, electrical, sensory, and / or mechanical components can be attached to a conductor layer of at least one circuit board of the detector body. In this way, the electron capture detector can be manufactured using the conventional assembly methods of the printed circuit board industry and directly populated with components. For example, some or all of the electronic components can be soldered using the reflow process.

[0021] According to an advantageous embodiment of the invention, one, several, or all circuit boards of the detector body each have at least one through-hole connection through which a conductor layer of a circuit board of the detector body is connected to another conductor layer of the same circuit board or to a conductor layer of another circuit board of the detector body. In this way, internal components of the electron capture detector, e.g., the anode, the cathode, or the detector, can be electrically contacted particularly efficiently and with short signal paths.

[0022] According to an advantageous embodiment of the invention, the walls of the reaction chamber are predominantly or completely metallized, with the metallization being formed at least partially by at least one conductor layer of at least one circuit board of the detector body. This allows the interior walls of the reaction chamber to be made chemically inert in a simple and minimal manner and / or minimizes disruptive interactions between the analyte and the interior.

[0023] According to an advantageous embodiment of the invention, the electron capture detector has at least one capacitor as an electronic component, which is formed by an arrangement of at least two mutually insulated conductor track layers of one or more of the circuit boards of the detector body, forming the capacitance of the capacitor. The capacitor can be used, for example, to implement a circuit with which the electron capture detector is operated in a pulsed manner. By using the conductor track layers to form the capacitor, it does not have to be provided and soldered on as a separate component. The conductor track layers can be designed as full-surface conductor track layers or structured conductor track layers, e.g. in the manner of individual conductor tracks.

[0024] Advantageously, a capacitance-forming arrangement of two insulated conductors and / or conductor layers of the circuit boards can be used as a capacitance for electrical signal transmission. It could also be used as a coupling capacitor to transmit time-varying signals and thus, for example, generate an electric field for manipulating electrons without requiring the use of another discrete component. Advantageously, a resistance or inductance can also be achieved through targeted conductor routing with appropriate conductor parameters.

[0025] According to an advantageous embodiment of the invention, the electron capture detector has at least one detector electrode, which is at least partially formed by at least one conductor layer of at least one circuit board of the detector body. In this way, the detector electrode for receiving the measurement signal of the electron capture detector can also be implemented with little effort, in particular without additional components. The detector electrode can be connected, for example, by means of a through-hole connection to a conductor layer on the outside of the detector body. A measuring amplifier can then be connected to this conductor layer.

[0026] According to an advantageous embodiment of the invention, the electron capture detector has at least one heating element for heating the reaction chamber, which heating element is designed as a resistance heater formed by at least one structured conductor track of at least one conductor track layer of at least one circuit board of the detector body. In this way, a heater for heating the reaction chamber can be integrated into the detector body very efficiently and with little effort. The at least one structured conductor track can, for example, be an inner conductor track layer in a multi-layer circuit board, so that the circuit board can be heated from the inside. Advantageously, the structured conductor track can be formed in a meander shape in order to provide the ohmic resistance required for the heating function through the conductor track in the smallest possible space.

[0027] According to an advantageous embodiment of the invention, the electron capture detector has an electron generation unit for generating free electrons in the reaction chamber. The electron capture detector can be located inside the reaction chamber, outside the reaction chamber, or partially inside and outside the reaction chamber. Depending on its design, the electron generation unit can be configured for the direct generation of electrons. The electron generation unit can also be configured to merely stimulate the generation of electrons, e.g., when they are located in a gas.

[0028] According to an advantageous embodiment of the invention, at least part of the electron generation unit is formed by at least one conductor layer of at least one circuit board of the detector body. This also allows the electron generation unit to be very efficiently integrated into the structure of the detector body in the circuit board design.

[0029] The aforementioned object is also achieved by a measuring system, in particular a gas chromatograph, which has an electron capture detector of the type described above. This also allows the aforementioned advantages to be realized.

[0030] The measuring system can, for example, have a circuit board on which parts of the electronics of the measuring system are arranged. At least one circuit board of the detector body of the electron capture detector can be formed as part of the circuit board of the measuring system.

[0031] The invention is explained in more detail below using exemplary embodiments and drawings.

[0032] It shows

[0033] Figure 1 shows a first embodiment of an electron capture detector, Figure 2 shows a second embodiment of an electron capture detector, Figure 3 shows a third embodiment of an electron capture detector.

[0034] The drawings show the electron capture detector in a schematic side sectional view.

[0035] Figure 1 shows an embodiment of an electron capture detector having a detector body 1a formed from three printed circuit boards 1 stacked on top of one another. A reaction chamber 4 is formed inside the detector body 1a, which serves to capture electrons during operation of the electron capture detector. The reaction chamber 4 is connected to the environment via a feed opening 3a. The substances to be analyzed can be introduced into the reaction chamber 4 through the feed opening 3a. The reaction chamber 4 is also connected to the environment via a discharge opening 3b. The substances in the reaction chamber 4 can be discharged again via the discharge opening 3b.

[0036] In the area of ​​the reaction chamber 4, the electron capture detector also has an anode 21 and a cathode 20. The anode 21 can also serve as a detector electrode connected to a measuring amplifier. For example, the anode 21 and the cathode 20 can be formed by conductor track layers 2a of the circuit boards 1. The lower circuit board 1 can be designed as a multilayer circuit board, in which conductor track layers are arranged not only on the opposite outer surfaces of the circuit board 1, but also with additional conductor track layers 2a inside.

[0037] Figure 1 shows an embodiment of an electron capture detector in which a graphene oxide semiconductor arrangement (GOS) is formed as the electron generation unit 16.

[0038] Figures 2 and 3 show a structure of an electron capture detector in which an X-ray source is used as the electron generation unit 16. The electron generation unit 16 is structurally integrated into the structure of the detector body 1a and, in particular, the stacked structure of the circuit boards 1, and can be fixed therein, for example, by means of a form fit.

[0039] Advantageously, a printed circuit board ECD, as shown in Figures 1 to 3, consists of one or more printed circuit boards 1, which have none, one, or a plurality of metallized circuit board layers or conductor track layers 2a, 2b, 2c. The printed circuit boards can be arranged either planar on top of one another or positioned at any angle to one another. The printed circuit boards 1 can be rigid and / or flexible. A composite of several materials to form a printed circuit board 1 is also conceivable.

[0040] Advantageously, the circuit boards have through-holes 3, continuous millings 4, and / or one-sided deep millings 5 ​​in any combination and overlap, which can optionally be partially or fully metallized and / or otherwise coated. These recesses can be used to form, among other things, structures for the gas ducts, i.e., the supply opening 3a and / or discharge opening 3b, for reaction chambers 4 for electron generation and / or the electron capture process. These sections in the assembled circuit board ECD are advantageously hermetically sealed from the environment and thus from unwanted contamination. These sections are referred to collectively below under the term "interior space."

[0041] Advantageously, the partially or fully metallized circuit board layers 2a, 2b, 2c can be connected to one another by electrically conductive contacts. These include, in particular, the through-hole platings 6, edge metallizations 7, plug connections, and / or screw connections 8 that are common for circuit boards.

[0042] Advantageously, printed circuit boards 1 and adjacent components can be joined together using adhesives 9 and / or solder joints 10 and / or welded joints and / or plug-in connections. Joining using screws 8 or other mechanical components is also possible, with the use of seals and / or gaskets in deep milled recesses 5 being advantageous. This allows for a hermetic seal against the environment to prevent contaminants from entering the interior. This also enables operation under negative, normal, or positive pressure.

[0043] Advantageously, mechanisms or devices 15, 16, e.g., the aforementioned electron generation unit, for generating free electrons can be mechanically and electrically integrated or connected in the interior space 4 of the printed circuit board ECD. The components 15, 16 required for this can either be fully incorporated into the interior space 4 or be sealingly attached. An example of a possible electron generation unit is the ionization of a gas and / or a gaseous dopant by electromagnetic radiation, such as microwave radiation, UV light, laser radiation, and / or X-rays or radioactive radiation. Further examples include electron generation by means of a plasma discharge, the emission of photoelectrons, and / or the introduction of directly electron-emitting devices, such as field emitters, metal oxide semiconductors, and / or graphene oxide semiconductors.

[0044] Advantageously, electrical, sensory and / or mechanical components 11a, 11b, 11c can be attached to a printed circuit board ECD. In particular, electrical circuits can advantageously be implemented on one or more printed circuit boards 1 and there on one or more conductive track layers, as with conventional electronic circuit boards. In principle, this means that all of the electronics required for the operation of the ECD and its electron sources can be implemented directly on it, whereby sensitive and potentially interference-prone signal paths, such as those of the detector current, advantageously remain short. The resulting small size also predestines the printed circuit board ECD for possible handheld applications. The printed circuit board or the assembly of printed circuit boards that make up the printed circuit board ECD can, if necessary,be directly part or section of a larger circuit board, which, for example, includes the control system for the gas chromatograph. Connectors 11d for connecting external signals can also be attached directly to the circuit boards.

[0045] Advantageously, conductor tracks 2b, preferably in a meander shape, and / or heating elements attached to the circuit board ECD as components 11a, 11b, 11c can be heated by an electric current, thereby achieving direct heating that is beneficial for the operation of the ECD. One advantage of multilayer circuit boards is the arrangement of the heating conductor tracks 2b directly beneath / at the sections where heating is necessary. These can be located one or more layers of the heating conductor tracks 2b at a distance from the reaction chamber 4 so as not to influence the processes in the interior of the ECD.

[0046] Advantageously, gas supply or discharge lines in the form of capillaries or tubes 12a, 12b can be glued directly into the supply and / or discharge openings with adhesive 13a, so that the interior space 4 remains hermetically sealed. It is also conceivable to weld or solder metallic capillaries 12b there using a welding or soldering material 13b.

[0047] Advantageously, a structure comprising printed circuit boards 1 allows the complete inclusion and / or connection of components such as electrically conductive grids and / or foils and / or contact pins.

[0048] Advantageously, by appropriately structuring the circuit boards, the ECD reaction chamber geometries known from the literature can be formed, such as a planar plate arrangement, a pin-cup arrangement, a coaxial-cylindrical arrangement, or a half-shell arrangement. The electrodes 20, 21 can advantageously be realized directly through the metallization of the circuit boards 2b, 2c, 7 and / or through the introduction of electrically conductive objects 14, 15, such as a metal wire or grid. Electrically conductive objects are both mechanically fixed and electrically contacted to at least one circuit board.Furthermore, it is conceivable to construct and operate the printed circuit board ECD with more than two electrodes with the same electrical potential or with different electrical potentials to achieve further advantageous distributions of the electric field and thus, for example, to guide the electrons more effectively to the desired electrodes. It is also conceivable to use electrodes under a protective layer or in another layer of the printed circuit board.

[0049] Advantageously, the conductor layer and edge metallization can achieve complete metallization of the interior, possibly with small interruptions for electrical insulation, to make the gas-carrying sections of a printed circuit board (ECD) chemically inert and / or minimize disruptive interactions of the analyte with the interior. Typical advantageous metallizations include chemical gold or silver, which are offered as standard by printed circuit board manufacturers.

[0050] Advantageously, a conical and / or continuous widening of the gas-carrying cross-section takes place from the point of gas introduction to the reaction chamber in order to flow through the reaction chamber at an optimal width with a desired velocity distribution. This allows, for example, interaction with the analyte via free electrons in each section, which is beneficial for ECD performance. Furthermore, this can reduce the residence time of the introduced gas, thereby improving the temporal-dynamic detection characteristics of a printed circuit board ECD. For example, the supply opening and / or discharge opening can have a conical and / or continuous widening of the internal cross-section.

[0051] Furthermore, it is conceivable to advantageously provide additional gas inlets 12b in the circuit boards, for example, to allow the addition of make-up gas or a dopant directly into the circuit board ECD. In addition, additional gas addition in a specific spatial flow distribution that does not mix directly with the analyte is conceivable, so that, for example, the gas flow of the analyte gas from the GC is focused within desired areas. This can be used to reduce contact of the analyte gas with the interior surfaces and thus avoid adverse interactions. In addition, the analyte gas can be focused into areas of high electron density to improve ECD performance.

[0052] *****

Claims

Patent claims 1. Electron capture detector comprising a detector body (1a) in which a reaction chamber (4) for capturing free electrons is arranged, characterized in that the detector body (1a) is constructed predominantly or entirely from one or more electrical circuit boards (1).

2. Electron capture detector according to claim 1, characterized in that the detector body (1a) is formed predominantly or completely by a plurality of electrical circuit boards (1) which are stacked on top of one another, wherein the reaction space (4) is formed by at least one recess produced in one or more circuit boards (1).

3. Electron capture detector according to one of the preceding claims, characterized in that the detector body (1a) has a feed opening (3a) and a discharge opening (3b), wherein the feed opening (3a) and / or discharge opening (3b) is formed by at least one through-opening (3) in at least one circuit board (1) of the detector body (1a).

4. Electron capture detector according to one of the preceding claims, characterized in that one, several or all circuit boards (1) of the detector body (1a) are designed as high-temperature circuit boards, in particular as circuit boards (1) with circuit board materials such as ceramics or ceramic composites.

5. Electron capture detector according to one of the preceding claims, characterized in that the surface of one, several or all circuit boards (1) of the detector body (1a) are completely or partially covered with a protective layer.

6. Electron capture detector according to one of the preceding claims, characterized in that a desired internal geometry of the reaction chamber (4) is formed at least in part by appropriate structuring of the circuit boards (1) of the detector body (1a).

7. Electron capture detector according to one of the preceding claims, characterized in that several or all circuit boards (1) of the detector body (1a) are arranged parallel to one another.

8. Electron capture detector according to one of the preceding claims, characterized in that one, several or all circuit boards (1) of the detector body (1a) are designed as single-layer or multi-layer circuit boards (1) coated with metallic conductor track layers (2a).

9. Electron capture detector according to claim 8, characterized in that the electron capture detector has an anode (21) and a cathode (20), wherein the anode (21) and / or the cathode (20) is formed by at least one metallic conductor layer (2a) of at least one circuit board (1) of the detector body (1a).

10. Electron capture detector according to one of claims 8 to 9, characterized in that the electron capture detector has at least one electronic evaluation circuit and / or an electronic control circuit with electronic components (11a) which are soldered onto at least one structured conductor layer (2a) of at least one printed circuit board (1) of the detector body (1a).

11. Electron capture detector according to one of claims 8 to 10, characterized in that one, several or all circuit boards (1) of the detector body (1a) each have at least one through-contact (6) through which a conductor track layer (2a) of a circuit board (1) of the detector body (1a) is connected to another conductor track layer (2a) of the same circuit board (1) or to a conductor track layer (2a) of another circuit board (1) of the detector body (1a).

12. Electron capture detector according to one of claims 8 to 11, characterized in that the walls of the reaction chamber (4) are predominantly or completely metallized, wherein the metallization is formed at least in part by at least one conductor track layer (2a) of at least one circuit board (1) of the detector body (1a).

13. Electron capture detector according to one of claims 8 to 12, characterized in that the electron capture detector has as electronic component (11a) at least one capacitor which is connected by a capacitor which determines the capacitance of the The capacitor-forming arrangement is formed by at least two mutually insulated conductor track layers (2a) of one or more of the circuit boards (1) of the detector body (1a).

14. Electron capture detector according to one of the preceding claims, characterized in that the electron capture detector has at least one detector electrode which is formed at least in part by at least one conductor layer (2a) of at least one circuit board (1) of the detector body (1a).

15. Electron capture detector according to one of the preceding claims, characterized in that the electron capture detector has at least one heating element for heating the reaction chamber (4), which heating element is designed as a resistance heater formed by at least one structured conductor track (2b) of at least one conductor track layer (2a) of at least one circuit board (1) of the detector body (1a).

16. Electron capture detector according to one of the preceding claims, characterized in that the electron capture detector has an electron generation unit (16) for generating free electrons in the reaction space (4).

17. Electron capture detector according to claim 16, characterized in that at least a part of the electron generation unit (16) is formed by at least one conductor layer (2a) of at least one circuit board (1) of the detector body (1a).

18. Measuring system, in particular a gas chromatograph, comprising an electron capture detector according to one of the preceding claims. *****

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