USE OF AN IONIZATION DEVICE, DEVICE AND METHOD FOR IONIZING A GASEOUS SUBSTANCE, AND DEVICE AND METHOD FOR ANALYZING A GASEOUS IONIZED SUBSTANCE

Description

[0001] The invention relates to the technical field of the ionization of a gaseous substance, in particular the ionization or ionization of a gaseous substance in preparation for its analysis.

[0002] WO 2009 / 102766 describes a plasma probe that ionizes a discharge gas through a dielectric barrier discharge. To ionize a sample, the plasma probe is directed at the sample to ionize it. The ionized sample can be analyzed in a mass analysis unit located near the sample. This type of ionization results in repulsion of charged particles and collisions with gas molecules, which can cause a discharge. This leads to a significant loss of ions before they reach the analysis and thus reduced sensitivity.

[0003] US 2013 / 0161507 A1 discloses a mass spectrometer in which the dielectric barrier discharge technique is used to ionize an analyte. Specifically, the publication addresses achieving a low voltage for the discharge between two electrodes (see p. 1,

[0009] ). A sample 101 to be analyzed is introduced into a sample vessel 106 and, through a pressure gradient under vacuum, is transported into a discharge region 114, where ionization takes place. The pressure in the discharge region is between 2 Torr and 300 Torr (between 266 Pa and 39900 Pa), with a distance between the electrodes 112 and 113 between 1 mm and 100 mm (see p. 2,

[0035] ). The vacuum in the discharge region 114 is necessary to achieve a low discharge voltage. In addition, a light irradiation unit 116 is applied, which irradiates an area and generates a discharge.Such a device (under vacuum) is structurally complex and the necessity of introducing a sample into the sample vessel is only applicable for certain analyses.

[0004] US 2012 / 292501 A1 describes another mass spectrometer with different electrode arrangements for dielectric barrier discharge.

[0005] The invention is before the Task to provide a device through which a discharge gas and a sample substance can be ionized in the flow and the sample substance is essentially not destroyed (fragmented), can be used under ambient conditions to avoid high constructional and equipment expenditure and ensures high sensitivity in the event of a possible analysis of an ionized substance.

[0006] The object is achieved by using an ionization device (claim 1), an ionization device (claim 14) which can be used in an ionization process (claim 9).

[0007] The ionization device comprises at least two electrodes separated by a dielectric element. The dielectric element is shaped like a hollow body, allowing a discharge gas and a sample substance to flow through the element. A first electrode is arranged outside the dielectric element. The first electrode can be designed as a ring or a hollow cylinder and can be pushed or applied over the dielectric element. The second electrode is arranged inside the dielectric element. Applying a sufficiently high alternating voltage to one or both of the electrodes results in a dielectric barrier discharge in a dielectric discharge region of the ionization device. The ionization of gaseous substances takes place in and / or downstream of the dielectric discharge region.

[0008] Surprisingly, it has been shown that the ionization efficiency depends to a considerable extent on the arrangement of the electrodes relative to each other, which, with an advantageous arrangement, can significantly increase the sensitivity of a possible subsequent analysis. For high ionization efficiency, the distance between the associated ends of the electrodes is between -5 mm and 5 mm (a detailed representation of the distance can be found in the Figures 1a to 1c ).

[0009] A small distance between the electrodes perpendicular to the flow direction is also advantageous, but can be designed differently depending on the impact on the dielectric discharge, which can occur between at least two electrodes. Equally surprising is the highly efficient ionization of gaseous substances at a pressure of over 40 kPa in the discharge area. The negative pressure can be provided by a vacuum unit arranged at the outlet of the ionization device.

[0010] The desired and achieved result of the invention is the flow-through ionization of a sample substance for analysis. This process uses so-called "soft" ionization, which largely does not destroy or fragment molecules, but rather leads to quasi-molecular ions through protonation and charge transfer reactions. Especially in combination with (high-resolution) mass spectrometry, this allows for direct identification of the substance via its elemental composition. The inventive design of the ionization device and the ionization process achieves very high sensitivity in the low femto- to attogram range during subsequent analysis.

[0011] The invention provides a highly efficient ionization device (with associated method) that, in combination with mass spectrometry or ion mobility spectrometry, provides a highly sensitive "electronic nose" (in one analytical method) that allows direct chemical analysis of molecules in the gas phase. Possible applications include, in addition to classic combinations with chromatographic methods (GC, HPLC, nano-LC), direct screening analyses, e.g., direct pesticide analysis on fruit or vegetable surfaces. The technology can be used in the military or in civil defense to detect toxic compounds or warfare agents. Very high sensitivity is particularly necessary for chemical warfare agents, as even the smallest concentrations can lead to life-threatening poisoning. Another related area of application is forensics or security checks (narcotics or explosives wipe tests).A combination with sample pre-enrichment systems such as SPME is also possible. The method can be used for medical point-of-care diagnostics (e.g., biomarker analysis in breath or in combination with SPME for hazardous and prohibited substances in blood, urine, etc.).

[0012] The possibility of flow-through ionization generally simplifies sampling during analysis ("sucking in" analogous to the human nose), which is important for rapid analytical applications or screening analyses, for example, in industrial process control. Furthermore, the previously existing problem of effectively transferring charged particles from atmospheric pressure into a vacuum (analysis) is solved. Due to the mutual repulsion of the charged particles, large portions of the ions formed are lost unused in currently used atmospheric pressure ionization processes (e.g., ESI, HESI, APCI, DART, DESI, LTP). By forming the ions directly in or at the inlet, an effective transfer of the charged particles for analysis is ensured, thus ensuring high sensitivity.

[0013] Chemical analyses usually require both qualitative and quantitative analysis. Due to the problem of an "open" connection between the ionization and the analyzer, as is the case with existing methods, quantification can easily be disrupted by external influences (drafts, diffusion of contaminants, etc.). This leads to the problem of false or inaccurate analysis results. Flow-through ionization closes the connection between the ionization and the analyzer, thus solving the described quantification problem.

[0014] Existing plasma-based ionization processes at near-atmospheric pressure do not allow the analyte to be introduced into the discharge gas, as the analyte is destroyed in the discharge. This problem is solved by creating an extremely "soft" plasma with little or no fragmentation.

[0015] The degree of fragmentation that occurs, like the efficiency, depends in part on the composition of the surrounding atmosphere (humidity, etc.). Thus, the appropriate selection of additive compounds (dopants) or gas compositions can reduce or increase ionization efficiency and / or fragmentation. The latter is particularly useful for portable applications, since portable systems usually cannot generate the characteristic fragments used to identify substances themselves.

[0016] Furthermore, the invention allows for the miniaturization of analytical devices and can be combined with portable systems, which significantly increases their sensitivity. Battery operation is also possible. No operating materials (other than electrical energy) are required, and analyses can be performed in less than 100 ms. Furthermore, the miniaturization and design of the invention allow for combination with other existing ionization methods (e.g., ESI, APCI, etc.), which enables the simultaneous detection of different analytes, such as the parallel ionization of highly polar and nonpolar substances.

[0017] A further development of the ionization device includes the introduction of so-called "dopant" substances (such as in chemical ionization) before or after the ionization device for the purpose of increasing selectivity or sensitivity.

[0018] The ionization device enables efficient ionization in the dielectric barrier discharge region to be carried out even at a pressure greater than 60 kPa, preferably greater than 80 kPa, and particularly preferably at substantially atmospheric pressure.

[0019] The distance between the associated ends of the first and second electrodes is preferably between -3 mm and 3 mm, more preferably between -1 mm and 1 mm, particularly preferably between -0.2 mm and 0.2 mm and most preferably between -0.05 mm and 0.05 mm for a particularly high efficiency of ionization by a dielectric barrier discharge.

[0020] The second electrode, which is arranged at least partially inside the dielectric element, can have a hollow cylindrical shape or be designed as a hollow body with a non-circular base area. Suitable basic shapes for a hollow body additionally include a triangular, rectangular, or oval basic shape. The second electrode can also be designed as a wire arranged concentrically or eccentrically to the dielectric element. A small distance between the second electrode perpendicular to the flow direction of the gaseous substances and the dielectric element is advantageous. In particular, the distance is less than 0.5 mm and preferably less than 0.1 mm. Particularly good ionization results are achieved when the second electrode rests against the inner side of the dielectric element.

[0021] The first electrode can be at a distance from the dielectric element perpendicular to the flow direction of the gaseous substances, wherein this distance is preferably less than 5 mm. In particular, the second electrode is located on the outside of the dielectric element. The best ionization results are achieved when the first electrode is applied as a layer to the outside of the dielectric element. This avoids parasitic discharges of the first electrode, which can also occur at a (very) small distance (e.g. gas inclusions) between the first electrode and the dielectric element. The first electrode can be applied as a layer using a drying or hardening liquid or suspension, for example a metallic lacquer. The layer can also be applied to the outside of the dielectric element by a transition from a gas phase to the solid phase.For example, sputtering, CVD or PVD, or other layer deposition techniques can be used.

[0022] The first and second electrodes are made of a conductive material (for electrical current). Specifically, they are made of a metal, preferably silver or gold, containing a silver or gold component (also in the form of a layer), or a metallic alloy.

[0023] The dielectric element may be made of a plastic (e.g. PMMA or PP) or preferably of quartz glass or another dielectric material.

[0024] The ionization device has an inlet and an outlet. A discharge gas and a sample substance can enter the ionization device through the inlet, be at least partially ionized inside, and exit at least partially ionized through the outlet. The area of the inlet through which the discharge gas and sample substance can flow is preferably larger than the area through which the outlet can flow; specifically, a flow restriction is arranged at the outlet of the device.

[0025] Flow through the ionization device is preferably induced by a pressure gradient. The pressure is preferably greater at the inlet of the device than at the outlet; specifically, the pressure at the outlet of the device is lower than atmospheric pressure, and the pressure outside the inlet is atmospheric pressure.

[0026] By arranging an analysis unit next to the ionization device, an analysis device can be formed. The ionization device is preferably connected directly (optionally via a short intermediate element) to the analysis unit. The analysis unit is preferably a unit that can perform analysis based on molecular charge, for example, a mass spectrometer, ion mobility spectrometer, or comparable devices.

[0027] Preferably, in addition to an ionization device according to the invention, at least one further ionizing device can be arranged in the analysis device, for example a device for carrying out electron impact ionization, electrospray ionization or the like.

[0028] For a particularly simple analysis device, the inlet of the ionization device is open to the environment, and the discharge gas is the atmosphere surrounding the inlet, specifically air. Other discharge gases can also be used, for example, nitrogen, oxygen, methane, carbon dioxide, carbon monoxide, at least one noble gas, or mixtures thereof.

[0029] In preferred embodiments, the ionization device or the analysis device can be miniaturized to allow portability (e.g., "handheld" devices).

[0030] The ionization device can be used in a process by which a discharge gas and a sample substance are ionized, especially in a flow-through process. First, the discharge gas and the sample substance are introduced into the ionization device through the inlet of the ionization device. A voltage is applied between the first and second electrodes such that a dielectric barrier discharge is caused in a dielectric barrier discharge region, and the discharge gas and / or the sample substance are ionized in and / or downstream of the discharge region.

[0031] To generate the dielectric barrier discharge, a voltage of up to 20 kV can be used, preferably no more than 10 kV and especially no more than 5 kV. Particularly good ionization results are achieved at a voltage between 1 kV and 3 kV.

[0032] The dielectric barrier discharge can be achieved by unipolar voltage pulses (or high-voltage pulses) to minimize the effects of a displacement current and thus, for example, suppress unwanted fragmentation reactions. The pulses preferably have a duration of 1 µs and especially a duration of no more than 500 ns. Best results are achieved with a pulse duration between 100 ns and 350 ns. In this case, the pulses preferably have a frequency of no more than 1 MHz, especially no more than 100 kHz, and most preferably no more than 25 kHz. The most energy-efficient ionization results are achieved at a frequency between 1 kHz and 15 kHz.

[0033] The voltage between the first and second electrodes can be applied by a sinusoidal voltage, wherein the sinusoidal voltage of one of the first and second electrodes is preferably shifted by half a period compared to the other of the first and second electrodes.

[0034] An analysis device can be used in a method wherein a discharge gas and a sample substance are introduced into the inlet of an ionization device. A voltage is applied to the first and / or second electrode such that a dielectric barrier discharge is caused in a dielectric barrier discharge region. In and / or after the dielectric barrier discharge region, the sample substance and / or the discharge gas is at least partially ionized and subsequently analyzed.

[0035] A voltage of up to 20 kV can be used in the analysis process, preferably no more than 10 kV and especially no more than 5 kV. Particularly good ionization results are achieved at a voltage between 1 kV and 3 kV.

[0036] The dielectric barrier discharge in the analysis process can be achieved using unipolar voltage pulses (or high-voltage pulses) to minimize the effects of displacement current. The pulses preferably have a duration of 1 µs and, in particular, a maximum of 500 ns. Best results are achieved with pulse durations between 100 ns and 350 ns.

[0037] The pulses preferably have a frequency of no more than 1 MHz, specifically no more than 100 kHz, and particularly preferably no more than 25 kHz. The most energy-efficient ionization results are achieved at a frequency between 1 kHz and 15 kHz. The voltage between the first and second electrodes can be applied as a sinusoidal voltage, wherein the sinusoidal voltage of one of the first and second electrodes is preferably shifted by half a period compared to the other of the first and second electrodes.

[0038] An ionization device can be used for flow-through ionization of a discharge gas and a sample substance. A discharge gas, such as air or another atmosphere surrounding the inlet of the ionization device, can be continuously introduced into the device. A sample can be introduced into the device discontinuously or continuously with the discharge gas. Ionization takes place in a flow-through process inside the ionization device. Specifically, connecting an analysis unit to the ionization device ensures that the ionized sample substance to be analyzed enters the analysis unit without interacting with discharge gas that has not flowed through the ionization device, as would occur, for example, with plasma jets.

[0039] In a further embodiment, an ionization device may have a sample inlet located downstream of the discharge region. The sample inlet may, for example, be configured as a T-piece.

[0040] In such an embodiment, a discharge gas can be introduced through an inlet of an ionization device, the ionization device as described above or below, and ionized in the discharge region. In addition to the discharge gas, a dopant can be present in the discharge region, which, like the discharge gas, can be introduced via the inlet of the ionization device or via another inlet (dopant inlet) into the ionization device. This ionizes the discharge gas and / or the dopant in the ionization device. The sample introduced downstream of the discharge region reacts, specifically through a charge transfer reaction, with the ionized discharge gas and / or dopant, thereby ionizing the sample. During ionization, an absolute pressure of more than 60 kPa preferably prevails in the ionization device.

[0041] An ionization device described above or below can be used such that a discharge gas and / or dopant is present in the discharge region during ionization, whereby the discharge gas and / or dopant are ionized. During ionization, an absolute pressure of over 60 kPa prevails in the ionization device. The ionized discharge gas and / or dopant can leave the ionization device in ionized form and impinge on a sample outside the ionization device, causing a reaction, specifically a charge transfer reaction, between the ionized discharge gas and / or dopant and the sample. This allows a sample to be ionized.

[0042] In a further embodiment, an ion mass filter can be connected to an ionization device, as described above or below. An ion mass filter isolates or selects a specific ion or ions based on their mass or mass-to-charge ratio. An example of an ion mass filter is a quadrupole. The ion mass filter can be arranged between the discharge region of an ionization device and the sample inlet of the ionization device, if the ionization device has a sample inlet.

[0043] The ion mass filter can also be arranged between the discharge region of an ionization device and the output or outlet of the ionization device. By using an ion mass filter, specific ions of the discharge gas and / or dopant can be selected that are brought into contact with a sample, which can result in an improvement in selectivity and / or sensitivity during analysis of the ionized sample.

[0044] The ionization devices described can be used in the analysis devices, ionization methods or analysis methods described above or below.

[0045] The embodiments of the invention are illustrated by way of example and not in a manner that transfers or reads limitations from the figures into the claims. Figure 1 shows an embodiment of an ionization device 100 in a section through the longitudinal axis in the flow direction R. Figure 1a shows an embodiment of an ionization device 100 in a section through the longitudinal axis in the flow direction R with a positive value of the distance D. Figure 1b shows an embodiment of an ionization device 100 in a section through the longitudinal axis in the flow direction R with a negative value of the distance D. Figure 1c shows an embodiment of an ionization device 100 in a section through the longitudinal axis in the flow direction R with a value of the distance D equal to zero. Figure 2 shows an embodiment of an ionization device 100 in a section through the longitudinal axis in the flow direction R with a section perpendicular to the flow direction AA. Figure 3 shows an embodiment of an ionization device 100 in a section through the longitudinal axis in the flow direction R with a flow restriction 20.Figure 4 shows an embodiment of an ionization device 100 in a section through the longitudinal axis in the flow direction R with a flow restriction and an inlet or outlet A30. Figure 5 shows an embodiment of an ionization device 100 in a section AA of the embodiment of the . Figure 2perpendicular to the flow direction R. Figure 6 shows an embodiment of an ionization device 100 in a section perpendicular to the flow direction R. Figure 7 shows an embodiment of an ionization device 100 in a section perpendicular to the flow direction R. Figure 8 shows an embodiment of an ionization device 100 in a section perpendicular to the flow direction R. Figure 9 shows an embodiment of an ionization device 100 in a section perpendicular to the flow direction R. Figure 10 shows an embodiment of an ionization device 100 in a section perpendicular to the flow direction R. Figure 11 shows an embodiment of an analysis device 200 in a section through the longitudinal axis in the flow direction R with an ionization device 100 and an analysis unit 30.

[0046] Figure 1shows an embodiment of an ionization device 100 with a first electrode 1, which rests on the outer side 2a of a dielectric element 2. A second electrode 3 is arranged partially inside the dielectric element 2 and rests on the inner side 2b of the dielectric element. In this embodiment, the first and second electrodes 1, 3 and the dielectric element 2 are designed as cylindrical hollow bodies with open end faces. The outer diameter and the wall thickness of the first electrode 1 are selected such that the first electrode 1 rests on the dielectric element 2 and the outer diameter of the second electrode 3 is reduced compared to the first electrode 1 by essentially twice the wall thickness of the first electrode 1 and twice the wall thickness of the dielectric element 2.A discharge gas G or a sample substance S (or a mixture of the discharge gas G and a sample substance S) can flow through the ionization device 100 in a flow direction R. The discharge gas G and / or sample substance S can enter the ionization device 100 through the inlet E of the ionization device 100, which is open to the surrounding atmosphere. In this embodiment, the inlet E is formed by the open and permeable end face (opposite the flow direction R) of the second electrode 3 as a surface with the inner diameter of the second electrode. In other embodiments, the second electrode 3 can be arranged entirely inside the dielectric element 2, so that the inlet E of the ionization device 100 is formed by the open end face of the dielectric element 2, which lies opposite the flow direction R.An outlet A of the ionization device 100 is formed by the end face of the dielectric element 2 located in the flow direction R. The flow-through area of the outlet A is determined by the inner diameter of the dielectric element 2. The first and second electrodes 1, 3 are arranged relative to one another such that they are essentially spaced apart in the flow direction R. The distance between the electrodes 1, 3 perpendicular to the flow direction R results from the wall thickness of the dielectric element 2 located between the electrodes 1, 3.

[0047] At the outlet A of the ionization device 100, a vacuum unit 10 is arranged, in which a pressure below atmospheric pressure prevails, causing a flow in the ionization device 100 and controlling the pressure in the ionization device 100 (by controlling the pressure in the vacuum unit 10). A vacuum unit 10 can be arranged in all embodiments of the ionization device 100.

[0048] When a voltage, especially an alternating voltage, is applied to one or both of the electrodes 1, 3, a dielectric barrier discharge can form in a dielectric barrier discharge region 110 in order to ionize a discharge gas G or the sample substance S. The dielectric barrier discharge region 110 is in Figure 1 only shown schematically and indicates that the formation of a reactive species by the dielectric barrier discharge takes place primarily in the area between the electrodes 1, 3.

[0049] In another embodiment, the first and / or second electrode 1, 3 may be located in the dielectric element 2 such that the electrodes 1, 3 are insulated from each other.

[0050] The distance D between the associated ends of the electrodes 1, 3 is best determined in the Figures 1a , 1b and 1c visible.

[0051] In Figure 1a the distance D has a positive value (e.g. 1 mm) and results as the distance in or against the flow direction R between the two ends of the electrodes 1, 3. The first end in the flow direction R is assigned to the first electrode 1 and the last end in the flow direction R is assigned to the second electrode 3. With positive values of the distance D, the electrodes 1, 3 do not overlap in or against the flow direction R.

[0052] Figure 1bshows a distance D between the associated ends of the first and second electrodes 1, 3 in or against the flow direction R with a negative value (for example, -1 mm). If the electrodes 1, 3 overlap in or against the flow direction R, the first end of the first electrode 1 in the flow direction R is assigned to the last end of the second electrode 3 in the flow direction R. If the electrodes 1, 3 overlap, negative values of the distance D result.

[0053] In Figure 1c the distance D between the ends of electrodes 1, 3 is zero. The first end in the flow direction R is assigned to the first electrode 1, and the last end in the flow direction R is assigned to the second electrode 3. It will be apparent to a person skilled in the art that such a limiting case should only occur within the measurement accuracy of a distance measurement.

[0054] An arrangement of the electrodes 1, 3 as in Figure 1cdelivers the best ionization results. As the distance D between the associated ends of electrodes 1, 3 increases, the ionization efficiency decreases. The decrease in efficiency with increasing negative values of the distance D is less pronounced than the decrease in efficiency with increasing positive values of the distance D.

[0055] Figure 2 shows an embodiment of an ionization device 100 with overlapping electrodes 1, 3. The distance D has a negative value. To clarify the cross section, a section AA perpendicular to the flow direction is introduced (see Figure 5 ).

[0056] To the outlet A of an ionization device 100 is Figure 3 a flow restriction 20 is arranged. An example of an embodiment of the ionization device of the Figure 2shown, wherein a flow restriction 20 can be arranged on any other embodiment of the ionization device 100. In Figure 3The flow restrictor 20 is designed as a reducing piece that can be applied to the ionization device 100, thereby reducing the flow-through area of the outlet A of the ionization device. Flow through the ionization device can be caused by a pressure gradient, for which purpose a vacuum (for example, by a vacuum unit 10) is or will be applied to the outlet A of the ionization device; atmospheric pressure preferably prevails outside the inlet. By reducing the cross-sectional area at the outlet A, the flow through the ionization device 100 can be easily regulated at a predetermined pressure gradient (for example, by a specific vacuum at the outlet A20 of the flow restrictor 20).When using a flow restriction 20 and a predetermined vacuum at the outlet A20 of the flow restriction 20, the pressure gradient in the ionization device 100 is low compared to a pressure gradient without a flow restriction 20. Depending on the specific dimensions of the flow restriction 20 and the ionization device 100, the pressure in the dielectric barrier discharge region 110 is considerably higher than the pressure at the outlet A20 of the flow restriction 20 and only slightly lower than atmospheric pressure, which preferably prevails outside the inlet E. Those skilled in the art will understand that the specific pressure conditions result from the design of the respective components, material-specific properties, and the physical conditions (temperature, ambient pressure, etc.). The absolute pressure in the dielectric barrier discharge region 110 is greater than 60 kPa.Preferably, the flow through the ionization device 100 is between 0.01 L / min and 10 L / min, and more preferably between 0.1 L / min and 1.5 L / min.

[0057] In addition to a flow restriction 20, flow regulation by cross-sectional constriction can also be achieved by other structural or control-related measures (e.g., by a controllable cross-sectional change through a valve or a variable vacuum). For example, a constriction of the outlet A of the ionization device 100 by a non-constant cross-section of the dielectric element 2 can be advantageous. However, other suitable measures for regulating the pressure in the ionization device 100 and / or the flow through the ionization device are possible.

[0058] In Figure 4A further embodiment of an ionization device 100 with an inlet or outlet A30 is shown. The inlet or outlet A30 can be combined with all other embodiments of an ionization device 100 according to the invention (with or without flow restriction 20). The inlet or outlet A30 is designed such that, in the flow direction R, an additional substance can be introduced into the ionization device 100 downstream of or upstream of the dielectric barrier discharge region 110, or a portion of the flowing discharge gas G and the sample substance S can be discharged.

[0059] Figure 5 shows a section AA perpendicular to the flow direction R through the part of the embodiment of an ionization device 100 of Figure 2in which the electrodes 1, 3 overlap. Therein, the first electrode 1, the dielectric element 2, and the second electrode 3 have a circular cross-section. The first electrode 1 lies against the outer side 2a of the dielectric element 2, and the second electrode 3 lies against the inner side 2b of the dielectric element 2. In another embodiment, the second electrode 3 does not lie against the inner side 2b of the dielectric element 2 and can be flowed through and around by a discharge gas G and sample substance S flowing through the ionization device 100.

[0060] In Figure 6The second electrode 3 is designed as a wire or elongated body arranged in the central region (surface perpendicular to the flow direction R) of an ionization device 100. The inner side 2b of the dielectric element 2 can be contacted by a discharge gas G and sample substance S flowing through the ionization device 100. The first electrode 1 rests on the outer side 2a of the dielectric element 2.

[0061] In Figure 7 The second electrode 3 is designed as a wire or elongated body. The dielectric element 2 rests against the second electrode 3 with its inner side 2b. A discharge gas G and a sample substance S can flow through the annular gap formed between the dielectric element 2 and the first electrode 1.

[0062] In addition to the Figure 6 The embodiment shown is in the Figure 8In the illustrated embodiment of the ionization device 100, a body K is arranged around the first electrode 1. The second electrode 3 is designed as a wire or elongated body and does not contact the inner side 2b of the dielectric element 2. The first electrode 1 rests against the outer side 2a of the dielectric element 2. The body K surrounds the first electrode 1 such that a discharge gas G and sample substance S flowing through the ionization device 100 can be divided into two flowing portions. A first portion can flow through an annular gap formed between the body K and the first electrode 1, and a second portion can flow through an annular gap formed between the second electrode 3 and the dielectric element 2. The discharge gas G and the sample substance S are preferably only or largely ionizable in the annular gap between the second electrode 3 and the dielectric element 2.The dielectric barrier discharge region 110 preferably extends largely only into the annular gap between the second electrode 3 and the dielectric element 2. The flow of the discharge gas G and the sample substance S that can be divided in this embodiment can preferably be divided into the first and second portions after the inlet E into the ionization device and can be combined before (in each case in the flow direction R) the outlet A of the ionization device 100.Such a configuration makes it possible to ionize only a specific portion (depending on the specific dimensions of the components of this embodiment of the ionization device 100) of the discharge gas G and the sample substance S, which also reduces slight fragmentation of ionized substances, since the portion of the substances that does not flow through the dielectric barrier discharge region comes into contact with the portion of the substances that has flowed through the dielectric barrier discharge region when mixed and can be ionized, for example, by charge transfer reactions.

[0063] An embodiment of the ionization device 100 in Figure 9comprises a first electrode 1, a dielectric element 2, and a second electrode 3, each of which has a rectangular basic shape. The second electrode 3 is surrounded by the sides of the dielectric element 2 (inner side 2b) and can be flowed through and around by a discharge gas G and a sample substance S. The first electrode 1 lies against the outer side 2a of the dielectric element 2.

[0064] The first electrode 1, the dielectric element 2 and the second electrode 3 of the Figure 10 The embodiment of the ionization device 100 shown has a triangular basic shape and is otherwise analogous to the embodiment of the Figure 9 For basic geometric shapes with more than one side (e.g. triangles, other polygonal shapes, or other basic shapes), inner sides are grouped together as an inner side and outer sides as an outer side.

[0065] In other embodiments, various polygonal, elliptical and other basic shapes may be advantageous.

[0066] All cross sections of the Figures 5 to 10 may be cross-sections of the various embodiments of the ionization device 100 disclosed herein.

[0067] One in Figure 11The analysis device 200 shown comprises any embodiment of the ionization device 100, which is connected to an analysis unit 30. The connection between the ionization device 100 and the analysis unit 30 can be configured in various ways. For example, a direct connection (direct transition from the ionization device 100 to the analysis unit 30) can be configured, or an intermediate or transition piece can be arranged between the ionization device 100 and the analysis unit 30. When a discharge gas G and a sample substance S flow through the ionization device 100, the discharge gas G and the sample substance S are ionizable. If the ionized discharge gas G and the ionized sample substance S reach the analysis unit 30, the ionized sample substance S can be analyzed. In principle, any analysis unit that can analyze a property of a charged sample substance is suitable as the analysis unit 30.For example, an analysis unit 30 can be a mass spectrometer, an ion mobility spectrometer, or another unit known as such. A vacuum unit 10 can also be arranged on an analysis device 200.

Claims

1. Use of an ionizing device (100) for flow-through ionization of a discharge gas (G) and of a sample substance (S) at an absolute pressure of more than 60 kPa in the ionizing device (100), during ionization, the ionizing device (100) comprising an inlet (E), an outlet (A), a first electrode (1), a dielectric element (2) and a second electrode (3), wherein (a) the dielectric element (2) is configured in the shape of a hollow body having an inner side (2b) and an outer side (2a), and the discharge gas (G) and the sample substance (S) flow therethrough in a flow direction (R); (b) the first electrode (1) is arranged outside of the outer side (2a) of the dielectric element (2); (c) the second electrode (3) is arranged, at least section-wise, inside the dielectric element (2), is surrounded by the inner side (2b) of the dielectric element (2) perpendicularly to the flow direction (R), and the discharge gas (G) and the sample substance (S) flow therethrough or therearound; (d) a distance (D) in or contrary to the flow direction (R) between the associated ends of the first and second electrodes (1, 3) lies between -5 mm and 5 mm; (e) a dielectric barrier discharge is established in a dielectric barrier discharge region (110) by applying a voltage between the first and second electrodes (1, 3) so as to ionize the discharge gas (G) or the sample substance (S).

2. Use of the ionizing device (100) according to claim 1, wherein the pressure in the ionizing device (100) is higher than 80 kPa and is preferably essentially atmospheric pressure.

3. Use of the ionizing device (100) according to any one of claims 1 or 2, wherein the distance (D) between the associated ends of the first and second electrodes (1, 3) lies between -3 mm and 3 mm, preferably between -1 mm and 1 mm, more preferably between -0.2 mm and 0.2 mm and most preferably between -0.05 mm and 0.05 mm.

4. Use of the ionizing device (100) according to any one of claims 1 to 3, wherein the second electrode (3) has the shape of a hollow cylinder, the shape of a longitudinally extending hollow body with a triangular, rectangular or oval basic shape, or is a wire.

5. Use of the ionizing device (100) according to any one of claims 1 to 4, wherein the outer side of the second electrode (3) is spaced apart from the inner side (2b) of the dielectric element (2) at a distance of less than 0.5 mm, preferably less than 0.1 mm, and is preferably in contact with the inner side (2b) of the dielectric element (2).

6. Use of the ionizing device (100) according to any one of claims 1 to 5, wherein the first electrode (1) is substantially in contact with the outer side (2a) of the dielectric element (2) and is preferably configured as a layer applied through a drying or curing liquid or suspension or is applied through a transition from a vapor phase into a solid phase.

7. Use of the ionizing device (100) according to any one of claims 1 to 6, wherein the flow-through area of the outlet (A) of the ionizing device (100) is smaller than or equal to the area of the inlet (E) of the ionizing device (100), and the outlet (A) of the ionizing device (100) has preferably arranged thereon a flow limitation unit (20).

8. Use of the ionizing device (100) according to any one of claims 1 to 7, wherein a pressure gradient inside the ionizing device (100) causes a flow with the flow direction (R) in the ionizing device (100), preferably through a vacuum at the outlet (A) and an essentially atmospheric pressure directly outside the inlet (E).

9. A method for ionizing a discharge gas (G) and of a sample substance (S), with an ionizing device (100), the ionizing device (100) comprising an inlet (E), an outlet (A), a first electrode (1), a dielectric element (2) and a second electrode (3), wherein (a) the dielectric element (2) is configured in the shape of a hollow body having an inner side (2b) and an outer side (2a), and allows a flow of a discharge gas (G) and of a sample substance (S) therethrough in a flow direction (R); (b) the first electrode (1) is arranged outside of the outer side (2a) of the dielectric element (2); (c) the second electrode (3) is arranged, at least section-wise, inside the dielectric element (2), is surrounded by the inner side (2b) of the dielectric element (2) perpendicularly to the flow direction (R), and allows a flow of the discharge gas (G) and of the sample substance (S) therethrough or therearound; (d) a distance (D) in or contrary to the flow direction (R) between the associated ends of the first and second electrodes (1, 3) lies between -5 mm and 5 mm; (e) a dielectric barrier discharge is establishable in a dielectric barrier discharge region (110) by applying a voltage between the first and second electrodes (1, 3) in order to ionize the discharge gas (G) or the sample substance (S); and (f) the absolute pressure in the ionizing device (100) during an ionization is higher than 60 kPa; the method comprising the following steps: - inserting the discharge gas (G) and the sample substance into the inlet (E) of the ionizing device (100); - applying a voltage to the first and / or second electrodes (1, 3) so as to cause a dielectric barrier discharge between the first and second electrodes (1, 3) in a dielectric barrier discharge region (110); - ionizing the discharge gas (G) and / or the sample substance (S) in and / or after_ the dielectric barrier discharge region (110).

10. The method according to claim 9, wherein the applied voltage is a maximum of 20 kV, preferably a maximum of 10 kV, more preferably a maximum of 5 kV and most preferably between 1 kV and 3 kV.

11. The method according to any one of claims 9 or 10, wherein the dielectric barrier discharge is caused by unipolar high-voltage pulses having preferably a pulse duration of a maximum of 1 µs, particularly preferred of a maximum of 500 ns, and most preferred of a duration of between 100 ns and 350 ns.

12. The method according to claim 11, wherein the high-voltage pulses have a frequency of a maximum of 1 MHz, preferably of a maximum of 100 kHz, more preferably of a maximum of 25 kHz and most preferably a frequency of between 1 kHz and 15 kHz.

13. The method according to any one of claims 9 to 12, wherein the first and second electrodes (1, 3) are supplied with a sine-wave voltage, the sine-wave voltages of one electrode (1, 3) being preferably shifted by half a period relative to the other electrode (1, 3).

14. An ionizing device (100) for flow-through ionization with an inlet (E), an outlet (A), a first electrode (1), a dielectric element (2) and a second electrode (3), wherein (a) the dielectric element (2) is configured in the shape of a hollow body having an inner side (2b) and an outer side (2a), and the discharge gas (G) and the sample substance (S) flow therethrough in a flow direction (R); (b) the first electrode (1) is arranged outside of the outer side (2a) of the dielectric element (2); (c) the second electrode (3) is arranged, at least section-wise, inside the dielectric element (2), is surrounded by the inner side (2b) of the dielectric element (2) perpendicularly to the flow direction (R), and the discharge gas (G) and the sample substance (S) flow therethrough or therearound; (d) a distance (D) in or contrary to the flow direction (R) between the associated ends of the first and second electrodes (1, 3) lies between -5 mm and 5 mm; (e) a dielectric barrier discharge is established in a dielectric barrier discharge region (110) by applying a voltage between the first and second electrodes (1, 3) in order to ionize the discharge gas (G) or the sample substance (S); and (f) the absolute pressure in the ionizing device (100) during an ionization is higher than 60 kPa.

15. The ionizing device (100) according to claim 14, wherein the pressure in the ionizing device (100) is higher than 80 kPa and is preferably essentially atmospheric pressure.