Ion mobility spectrometer and method for analyzing a sample by ion mobility spectrometry

Abstract

The present invention relates to an ion mobility spectrometer, which at least has a first drift chamber and a first switchable ion gate for controllably transferring ions into the first drift chamber, wherein: the first ion gate is designed as a field-switching ion gate having at least a first counter electrode and a first injection electrode; wherein, a first ionization chamber is formed between the first counter electrode and the first injection electrode, and ions to be analyzed by ion mobility spectrometry can be fed from an ionization source into the first ionization chamber. The present invention also relates to an ion mobility spectrometer, which at least has a first drift chamber and a first switchable ion gate for controllably transferring ions into the first drift chamber, as well as a second drift chamber separated from the first drift chamber and a second switchable ion gate for controllably transferring ions into the second drift chamber. The present invention also relates to a method for analyzing a sample by ion mobility spectrometry using an ion mobility spectrometer, such as an ion mobility spectrometer of the aforementioned type, wherein, by means of an ionization source, ions to be analyzed are generated from the sample and provided in the ionization chamber of the ion mobility spectrometer.

Description

Field of the Invention

[0001] The present invention generally relates to the field of ion mobility spectrometers and methods for analyzing samples by ion mobility spectrometry. In this context, the abbreviation IMS is used both for the measurement method "ion mobility spectrometry" and for the measuring device "ion mobility spectrometer".

[0002] The invention relates to an ion mobility spectrometer which at least comprises a first drift chamber and a first switchable ion gate for controllably transferring ions into the first drift chamber, wherein the first ion gate is embodied as a field-switching ion gate which at least comprises a first counter electrode and a first injection electrode, and wherein a first ionization chamber is formed between the first counter electrode and the first injection electrode, and the ionization chamber ions to be analyzed by ion mobility spectrometry can be fed from an ionization source into the first ionization chamber.

[0003] The invention also relates to an ion mobility spectrometer which at least comprises a first drift chamber and a first switchable ion gate for controllably transferring ions into the first drift chamber, as well as a second drift chamber separate from the first drift chamber and a second switchable ion gate for controllably transferring ions into the second drift chamber.

[0004] The invention also relates to a method for analyzing a sample by ion mobility spectrometry by means of an ion mobility spectrometer, such as an ion mobility spectrometer of the type described above, wherein, by means of an ionization source, the ions to be analyzed are generated from the sample and provided in the ionization chamber of the ion mobility spectrometer. Background Art

[0005] Devices and methods for ion mobility spectrometry are known, for example, from DE 10 2015 112 869 A1 or EP 2 428 797 A1. Summary of the Invention

[0006] The present invention is based on the object of improving such ion mobility spectrometers and methods for ion mobility spectrometry with respect to their practical usability.

[0007] This object is achieved by means of an ion mobility spectrometer, which at least comprises a first drift chamber and a first switchable ion gate for controllably transferring ions into the first drift chamber, wherein the first ion gate is embodied as a field-switching ion gate which at least comprises a first counter electrode and a first injection electrode, wherein a first ionization chamber is formed between the first counter electrode and the first injection electrode, and the ionization chamber ions to be analyzed by ion mobility spectrometry can be fed from an ionization source into the first ionization chamber, and wherein at least one first additional electrode is arranged between the first ion gate and the first drift chamber, and the ions to be transferred into the first drift chamber by means of the first ion gate can additionally be influenced by the first additional electrode. By virtue of the additionally present first additional electrode (which does not originally exist in an ion mobility spectrometer with a field-switching ion gate), it is possible to implement a plurality of extended functions of the ion mobility spectrometer, and the plurality of extended functions enable the resolution and sensitivity of the ion mobility spectrometer to be improved. By generating a corresponding potential gradient between the electrodes, the first additional electrode can be capable of implementing, for example, also the dual field-switching method, the extended field-switching method and combinations thereof, which are referred to as the extended dual field-switching method. The cost for implementing such an ion mobility spectrometer is relatively low, especially since a field-switching ion gate can be used. Therefore, the ion mobility spectrometer can be implemented in a particularly compact and cost-effective manner in terms of its structure.

[0008] The field-switching ion gate comprises a counter electrode and an injection electrode. When using a field-switching ion gate, ionization, i.e., providing ions from a sample, is achieved in a space without or with almost no electric field, which space is also referred to as an ionization chamber. The ionization chamber is located between the counter electrode and the injection electrode, and as viewed from the ionization chamber, the drift chamber of the ion mobility spectrometer is located behind the injection electrode. By means of a corresponding potential switching of the electrodes of the field-switching ion gate, the ions provided as an ion packet in the ionization chamber can be transferred into the drift chamber, where they are guided by the electric field generated there along the ionization chamber as far as an ion detector, at which the collision ions are detected. An ion mobility spectrometer of this design can be implemented in a particularly compact and cost-effective manner in terms of its structure, since in this case, for example, an additional reaction chamber as known from DE 10 2015 112 869A1 does not need to be arranged upstream of the drift chamber. Therefore, the ion mobility spectrometer can be embodied such that an electric field is generated in the ionization chamber only by the electrodes of the field-switching ion gate, so that no additional field generating means for generating an electric field in the ionization chamber are required.

[0009] The present invention is based on the principle of field switching for feeding ions from a corresponding ionization chamber into a corresponding drift chamber of an ion mobility spectrometer. The term "field switching" or "field switching ion gate" includes the following functions: providing ions to be analyzed in an ionization space without an electric field or at least with almost no electric field, i.e., ionization of analyte molecules, so that during this ionization stage, due to the absence of an electric field, the provided ions have not moved in any direction. If an analysis step is then intended, the electrodes of the field switching ion gate are switched accordingly, i.e., at least one electrode is switched, thus causing the ions to move in the direction of the drift chamber.

[0010] Therefore, in the case of a field switching ion gate, at least during the ionization stage, the ionization chamber is substantially free of an electric field. To achieve this state of no electric field in the ionization chamber, the same electric potential can exist between the counter electrode and the injection electrode of the field switching ion gate. A small potential difference can also be applied between the counter electrode and the injection electrode to compensate for the field penetration from the drift chamber. However, in this case, the potential difference between the counter electrode and the injection electrode does not exactly create an electric field in the ionization chamber, but cancels the field penetration of the drift chamber, and thus compensates for the state of the ionization chamber in the direction of the no-electric-field state.

[0011] The ion mobility spectrometer can include a first additional electrode or a plurality of first additional electrodes. Due to the presence of the plurality of first additional electrodes, the described advantageous method steps can also be carried out in various ways. For example, in this case, the compression of the ion packet by dual field switching can be carried out as multi-field switching.

[0012] According to an advantageous refinement of the invention, the first additional electrode is arranged at the end of the first drift chamber facing the first ion gate. In this way, the ion mobility spectrometer can be further optimized in terms of structural dimensions. In addition, the first additional electrode can perform its desired function, such as being used to particularly effectively shield the electric field in the drift chamber.

[0013] According to an advantageous refinement of the invention, the distance between the first additional electrode and the first injection electrode is less than the distance between the first counter electrode and the first injection electrode. By this method, the structural dimensions of the ion mobility spectrometer and the effectiveness of the first additional electrode can also be further improved. Therefore, for example, the ion packet can be particularly effectively compressed in the second compression step described below.

[0014] According to an advantageous refinement of the invention, the first additional electrode is embodied in a non-switchable potential manner. Thus, the structure of the circuit hardware required for the operation of the ion mobility spectrometer is kept simple, and the shielding effect is improved. For example, the ion mobility spectrometer can be embodied in a manner that realizes potential switching only at the first injection electrode.

[0015] The object mentioned in the introduction is additionally achieved by means of an ion mobility spectrometer which at least comprises a first drift chamber and a first switchable ion gate for controllably transferring ions into the first drift chamber, as well as a second drift chamber separate from the first drift chamber and a second switchable ion gate for controllably transferring ions into the second drift chamber, wherein the first ion gate and / or the second ion gate are embodied as field-switching ion gates. In this way, for example, due to the fact that the part comprising the first drift chamber is configured for analyzing positive ions and the part comprising the second drift chamber is configured for analyzing negative ions, an ion mobility spectrometer with bipolarity can be achieved. The implementation of such an ion mobility spectrometer with one or two ion gates as field-switching ion gates enables a particularly compact structure to be achieved during measurement, while having ultra-high resolution and extremely high sensitivity.

[0016] According to an advantageous refinement of the invention, the first ion gate at least comprises a first counter electrode and a first injection electrode, wherein a first ionization chamber is formed between the first counter electrode and the first injection electrode, and ions to be analyzed by ion mobility spectrometry can be fed from an ionization source into the ionization chamber. Thus, in this case, the first ion gate is configured as a field-switching ion gate. Here, similar to the previous description, the first injection electrode can be arranged closer to the first drift chamber than the first counter electrode.

[0017] According to an advantageous refinement of the invention, the second ion gate at least comprises a second counter electrode and a second injection electrode, wherein a second ionization chamber is formed between the second counter electrode and the second injection electrode, and ions to be analyzed by ion mobility spectrometry can be fed from an ionization source into the ionization chamber. In this case, the second ion gate is configured as a field-switching ion gate. Here, the second injection electrode can be arranged closer to the second drift chamber than the second counter electrode.

[0018] At the end of the first drift chamber remote from the first injection electrode, the ion mobility spectrometer can comprise a first detector for detecting a first ion species, for example positive ions. At the end of the second drift chamber remote from the second injection electrode, the ion mobility spectrometer can comprise a second detector for detecting a second ion species, for example negative ions.

[0019] The first ionization chamber formed between the first counter electrode and the first injection electrode can be connected to the second ionization chamber formed between the second counter electrode and the second injection electrode or can be realized as a common ionization chamber. Independently of this, but also in combination with these features, the ion mobility spectrometer can be embodied by means of a common ionization source which provides ions of both polarities in the respective ionization chamber or the common ionization chamber.

[0020] According to an advantageous refinement of the invention, the first ion gate and the second ion gate are formed by an arrangement of at least a first multifunctional electrode and a second multifunctional electrode, wherein the first multifunctional electrode is arranged upstream of the first drift chamber and the second multifunctional electrode is arranged upstream of the second drift chamber, wherein the first multifunctional electrode forms the injection electrode of the first ion gate and the second multifunctional electrode forms the counter electrode of the first ion gate, and the second multifunctional electrode forms the injection electrode of the second ion gate and the first multifunctional electrode forms the counter electrode of the second ion gate. Thus, a particularly simple structure of the ion gate can be achieved. Then a common ionization chamber including a first ionization chamber and a second ionization chamber can be formed between the multifunctional electrodes.

[0021] In the embodiment with multifunctional electrodes described above, a pure counter electrode that only performs the function of the counter electrode can be dispensed with. Thus, a simpler structure of the ion mobility spectrometer with two ion gates can be achieved, which requires fewer electrodes. A common ionization chamber that achieves a higher positive and negative ion yield is additionally advantageous. In order to perform the methods of extended field switching and extended dual field switching also described below, it is advantageous to provide two first additional electrodes and two second additional electrodes in different cases. In this case, the additional electrode located closest to the respective drift chamber can be held at a fixed potential; the other additional electrodes closer to the multifunctional electrode arrangement can be switched to different potentials.

[0022] The ion mobility spectrometer can be implemented in such a way that the first drift chamber and the second drift chamber are arranged one after another on the same or at least substantially parallel axes. This achieves a relatively long structural length and a small diameter of the ion mobility spectrometer.

[0023] According to an advantageous refinement of the invention, the first drift chamber and the second drift chamber are arranged substantially parallel to each other and close to each other. Thus, the structural size of the ion mobility spectrometer can be further reduced. Specifically, compared to the embodiment described above, the structural length is substantially halved. In the case of this design, the arrangement of the electrodes of the respective ion gate can be interchanged, i.e., in this case, the first counter electrode can be arranged closer to the first drift chamber than the first injection electrode, and the second counter electrode can be arranged closer to the second drift chamber than the second injection electrode.

[0024] According to an advantageous refinement of the invention, the first counter electrode and the second counter electrode are short-circuited with one another or are embodied as a common counter electrode. Thus, the construction of the ion mobility spectrometer can be further optimized both with regard to the structural dimensions and with regard to the components required. In addition, the electrical construction can be further simplified. This embodiment is suitable, for example, for an ion mobility spectrometer in which the first drift chamber and the second drift chamber are arranged one behind the other on the same or at least substantially parallel axes. Alternatively, it can also be provided that the first injection electrode and the second injection electrode are short-circuited with one another or are embodied as a common injection electrode. This is advantageous, for example, if the first drift chamber and the second drift chamber are arranged substantially parallel and close to one another.

[0025] According to an advantageous refinement of the invention:

[0026] a) At least one first additional electrode is arranged between the first ion gate and the first drift chamber, and ions to be transferred into the first drift chamber by means of the first ion gate can additionally be influenced by the first additional electrode,

[0027] and / or

[0028] b) At least one second additional electrode is arranged between the second ion gate and the second drift chamber, and ions to be transferred into the second drift chamber by means of the second ion gate can additionally be influenced by the second additional electrode.

[0029] Thus, there can be one or more first additional electrodes and / or one or more second additional electrodes. The number of first additional electrodes and second additional electrodes present can be different, i.e., the ion mobility spectrometer can also be embodied asymmetrically with regard to the equipment of a single IMS tube with additional electrodes.

[0030] According to an advantageous refinement of the invention, the first additional electrode and / or the second additional electrode are embodied in a potential-switchable manner. This is particularly advantageous if extended field switching is intended. Thus, if the detector potential or gradient in the drift chamber is adapted to the case of extended field switching, the potential of the corresponding additional electrode can be adapted.

[0031] According to an advantageous refinement of the invention, the ion mobility spectrometer includes an X-ray ionization source, an ultraviolet (UV) ionization source, a corona ionization source, a plasma ionization source, a dielectric barrier discharge source, and / or an electron emitter as an ionization source. In this way, in particular in association with the field-switching ion gate, the above-mentioned high sensitivity and resolution can be further increased.

[0032] The ionization source can be arranged, for example, laterally next to the corresponding ionization chamber. In this case, it is advantageous to use an ionization source with a large penetration depth or at least a large aperture angle. It is also possible to combine the ionization source with the counter electrode (first counter electrode and / or second counter electrode), for example by integrating the ionization source structure into the counter electrode or in an embodiment as the counter electrode of the ionization source.

[0033] The ionization source may be a non-radioactive ionization source or a radioactive ionization source. For example, the counter electrode may be coated with a radioactive material.

[0034] As far as a general explanation is given about the field-switched ion gate and its counter-electrode and injection electrode, this applies both to the first ion gate and to the second ion gate, that is to say to the first and second counter-electrodes as well as to the first and second injection electrodes. The above-described embodiments of the ion mobility spectrometer with a first additional electrode can be advantageously combined in the case of an ion mobility spectrometer with unipolarity (with only one drift chamber) and in the case of the described embodiments with a first drift chamber and a second drift chamber. In the last-mentioned case, the second additional electrode can then be arranged upstream of the second drift chamber.

[0035] The objects mentioned in the foregoing are further achieved by means of a method for analyzing a sample by ion mobility spectrometry by means of an ion mobility spectrometer of the aforementioned type, wherein ions to be analyzed are generated from the sample by means of an ionization source and provided in a first ionization chamber, and the ions generated in the process are guided through a first drift chamber to a first ion detector under the control of a first ion gate, wherein the first ionization chamber is substantially field-free at least in the ion generation period, characterized by one or both of the following features a), b):

[0036] a) before the ion packets are transferred into the first drift chamber, the ion packets provided in the first ionization chamber are compressed for a first time in a first compression step by switching the potential difference between the first injection electrode and the first counter electrode, and after passing the first injection electrode, the ion packets are compressed for a second time in at least a second compression step by switching the potential difference between the first additional electrode and the first injection electrode,

[0037] b) At least during the ion generation period, ions generated in the first ionization chamber are substantially shielded from the electric field portion generated in the first drift chamber by the first additional electrode or at least the additional shielding electrode.

[0038] In this way, an advantageous method of dual-field switching or multi-field switching (feature a)), extended field switching (feature b)), or extended dual-field switching in combination therewith (combination of features a) and b)) can be achieved. By means of these methods, the resolution of the ion mobility spectrometer can be improved without the need for an extended drift chamber (which would otherwise be required). It is also possible to construct a more compact ion mobility spectrometer with comparable resolution, i.e., with a shorter drift chamber.

[0039] Due to ionization by means of an ionization source, the ions to be analyzed are provided in the first ionization chamber. These provided ions are also referred to as ion packets. By means of the switching of an ion gate, i.e., for example, the electrodes of a field-switching ion gate, the ions of the ion packet move in the direction of the drift chamber and are compressed for the first time in the process. In this case, the term "compression" relates to the extent of the ion packet in the desired flight direction, i.e., in the drift direction through the drift chamber. Due to the compression of the ion packet, the ion packet becomes narrower, which results in an enhanced resolution of the ion mobility spectrum. By using a first additional electrode in a second compression step for further (second) compression of the ion packet, the ion packet can be made narrower when transferred into the drift chamber compared to prior art ion mobility spectrometry methods. After the second compression step, one or more other compression steps (multi-field switching) can be carried out to make the ion packet even narrower. However, in many cases, the second compression step will be sufficient for practical applications.

[0040] The first compression step can be achieved by generating an electric field in the ionization chamber by means of an ion gate, i.e., by generating a potential difference between the injection electrode and the counter electrode. The second compression step can be achieved by generating another electric field between the ionization chamber and the drift chamber. For this purpose, for example, a potential difference can be generated between the injection electrode and the additional electrode.

[0041] In the case of an ion mobility spectrometer of the above type, specifically when using a field-switching ion gate, and more specifically when the injection electrode is arranged very close to the drift chamber (which is of course desirable) to achieve small structural dimensions, field penetration from the electric field present in the drift chamber into the ionization chamber may occur. In some cases, ions in the affected area of the field penetration may have entered the drift chamber, which results in a certain transmittance of the ion gate even in the closed state. Therefore, a small leakage current into the drift chamber may occur, which may lead to a significant reduction in the sensitivity and selectivity of the ion mobility spectrometer. To counteract this effect, it is conceivable, for example, to generate a very low electric field in the ionization chamber that is opposite to the field in the drift chamber by applying a so-called blocking voltage to the counter electrode. However, this has the effect of moving the ions in the ionization chamber in the direction of the counter electrode, which does prevent ions from passing through the closed ion gate to a certain extent, but results in ion losses at the counter electrode. This also reduces the sensitivity of the ion mobility spectrometer. In addition, other differentiations of specific ion species may occur. This can be prevented by a shielding achieved by means of an extended field-switching method according to the invention, in particular by shielding the ions generated in the ionization chamber by means of a first additional electrode or at least an additional shielding electrode. As viewed from the ionization chamber, the first additional electrode or the shielding electrode is then arranged behind the first injection electrode. In this way, as long as the ion gate is closed, the ionization chamber can still operate with substantially no electric field. However, since the area of the field penetration is shielded by the ionization chamber, unwanted ions are prevented from passing through the closed ion gate. Therefore, by this method, the sensitivity and selectivity of the ion mobility spectrometer can be increased in a simple manner, and unwanted differentiations of specific ion species can be avoided.

[0042] The object mentioned above is additionally achieved by a method for analyzing a sample by ion mobility spectrometry, in which, by means of an ionization source, the ions to be analyzed are generated from the sample and provided in a first ionization chamber and / or a second ionization chamber, and the positive and negative ions generated in the process are guided through separate drift chambers to separate respective ion detectors under the control of respective first and second ion gates, wherein the first ionization chamber and / or the second ionization chamber is substantially free of an electric field at least during the ion generation period. By this method, the advantages associated with the field-switching ion gate can also be achieved.

[0043] The method described can be used in any embodiment of the ion mobility spectrometer described above.

[0044] According to an advantageous refinement of the invention, the first counter electrode and the second counter electrode have the same potential. Thereby, the circuit structure for driving the ion gate and the structure of the ion gate itself are simplified.

[0045] According to an advantageous refinement of the invention, the opening and closing of the first ion gate and / or the second ion gate is achieved by switching the potential of the injection electrode and / or the counter electrode of the respective ion gate. By this method, the electrical drive of the ion gate is also simplified. Further potential switching at other electrodes or at a plurality of electrodes can be avoided.

[0046] According to an advantageous refinement of the invention, in the first compression step, the potential gradient between the first counter electrode and the first injection electrode is greater than the potential gradient in the drift chamber. Thus, effective compression of the ion packet in the first compression step can be achieved.

[0047] According to an advantageous refinement of the invention, in the second compression step, the potential gradient between the first injection electrode and the first additional electrode is greater than the potential gradient in the drift chamber. Thus, effective compression of the ion packet in the second compression step can be achieved.

[0048] According to an advantageous refinement of the invention, the potential gradient between the first injection electrode and the first additional electrode is greater in the second compression step than in the first compression step. Thus, particularly large compression of the ion packet in the second compression step can be achieved.

[0049] According to an advantageous refinement of the invention, in the first compression step, the potential gradient between the first injection electrode and the first additional electrode is substantially equal to the potential gradient in the drift chamber. In this way, uniform transfer of the ion packet from the ion gate into the drift chamber can be achieved.

[0050] According to an advantageous refinement of the invention, in the first compression step, the potential gradient between the first injection electrode and the first additional electrode is greater than the potential gradient between the first counter electrode and the first injection electrode and greater than the potential gradient in the drift chamber. In this way, ion focusing can be advantageously achieved, which can be used, for example, in extended field switching.

[0051] According to an advantageous refinement of the invention, the potential gradient between the first injection electrode and the electrode for shielding (i.e., the first additional electrode or the shielding electrode) is equal to zero, or at least opposite to the potential gradient in the drift chamber during the ion generation period. By this method, a good shielding effect can be achieved in extended field switching without perceivable ion loss.

[0052] According to an advantageous refinement of the invention, when switching to the first compression step, the switching of the potential gradient between the first injection electrode and the first additional electrode is later than the switching of the potential gradient between the first counter electrode and the first injection electrode. In this way, unwanted fast ions can be eliminated.

[0053] According to an advantageous refinement of the invention, when leaving the first compression step, i.e. when changing to the second compression step for example, the potential gradient between the first counter electrode and the first injection electrode switches earlier than the potential gradient between the first injection electrode and the first additional electrode. In this way, unwanted slow ions can be eliminated.

[0054] In this case, the potential gradient is understood to mean the gradient of the potential in the direction of the longitudinal axis of the drift chamber or in the desired drift direction of the ions in the drift chamber.

[0055] In the case of an ion mobility spectrometer having a second drift chamber, for example in the bipolar case, the features mentioned above with respect to the first ion gate, the first counter electrode, the first injection electrode, the first additional electrode and the first drift chamber can also be used as advantageous refinements of the corresponding components of the second ion gate, i.e. the second counter electrode, the second injection electrode and the second additional electrode and / or the second drift chamber. Description of the Drawings

[0056] The invention will now be explained in more detail on the basis of exemplary embodiments with the aid of the drawings.

[0057] In the drawings:

[0058] Figure 1 An ion mobility spectrometer having two drift chambers is shown;

[0059] Figure 2 Another embodiment of an ion mobility spectrometer having two drift chambers is shown;

[0060] Figure 3 An ion mobility spectrometer having one drift chamber is shown;

[0061] Figure 4 Shows an exemplary potential distribution diagram in an ion mobility spectrometer during dual field switching according to Figure 3 ;

[0062] Figure 5 Shows an exemplary potential distribution diagram in an ion mobility spectrometer during extended field switching according to Figure 3 ;

[0063] Figure 6 Shows an exemplary potential distribution diagram in an ion mobility spectrometer during extended dual field switching according to Figure 3 ;

[0064] Figure 7 Another embodiment of an ion spectrometer having two drift chambers is shown;

[0065] Figure 8 Another embodiment of an ion mobility spectrometer having two drift chambers is shown; Figure 9Illustrates an exemplary potential distribution diagram in an ion mobility spectrometer during normal field or dual-field switching according to Figure 8 ;

[0066] Figure 10 Illustrates an embodiment of an ion mobility spectrometer having two drift chambers and two multifunctional electrodes;

[0067] Figure 11 , Figure 12 Illustrates an exemplary potential distribution diagram in an ion mobility spectrometer according to Figure 10 ;

[0068] Figure 13 Illustrates an ion mobility spectrometer having two drift chambers;

[0069] Figure 14 , Figure 15 Illustrates an exemplary potential distribution diagram in an ion mobility spectrometer during extended field switching according to Figure 13 ; Figure 16 Illustrates an ion mobility spectrometer having two drift chambers in one embodiment;

[0070] Figure 17 Illustrates an exemplary potential distribution diagram in an ion mobility spectrometer according to Figure 16 ;

[0071] Figure 18 Illustrates an ion mobility spectrometer having two drift chambers arranged in parallel; Figures 19 to 22 Illustrates an exemplary potential distribution diagram in an ion mobility spectrometer according to Figure 18 ;

[0072] Figure 23 Illustrates another embodiment of an ion mobility spectrometer having two drift chambers arranged in parallel; Figures 24 to 27 Illustrates an exemplary potential distribution diagram in an ion mobility spectrometer according to Figure 23 ;

[0073] Figure 28 Illustrates another embodiment of an ion mobility spectrometer having two drift chambers arranged in parallel; and Figures 29 to 32 Illustrates an exemplary potential distribution diagram in an ion mobility spectrometer according to Figure 28 . Detailed Description

[0074] Figure 1An ion mobility spectrometer 1, 2 is shown having a substantially coaxial arrangement of two IMS tubes 1, 2. The IMS tube 1 includes a first ion gate 10, which includes a first counter electrode 11 and a first injection electrode 12. A first ionization chamber 13 is formed between the first injection electrode 12 and the first counter electrode 11. Behind the first injection electrode 12, a first drift chamber 14 is adjacent to the first ionization chamber 13 and terminates at a first ion detector 16. In the region of the first drift chamber 14, there is a first field generating means 15, for example in the form of an annular electrode surrounding the first drift chamber 14. The first field generating means 15 can generate an electric field in the first drift chamber 14 that exerts a desired drift effect on the ions to be examined, such that the ions are transported from the first ion gate 10 to the first ion detector 16. The drift gas can flow through the first drift chamber 14, for example, in a direction opposite to the drift direction of the ions. For this purpose, the first IMS tube 1 includes a first drift gas inlet connection 17 and a first drift gas outlet connection 18. The drift gas can be introduced into the IMS tube 1 at the first drift gas inlet connection 17. The drift gas can be discharged from the IMS tube 1 at the first drift gas outlet connection 18.

[0075] The ion mobility spectrometer or the first IMS tube 1 and the second IMS tube 2 can include additional connections for introducing and discharging the sample gas. These connections can be arranged, for example, in the region of the first ionization chamber 13 and / or the second ionization chamber 23.

[0076] The second IMS tube 2 is constructed in a similar manner to the first IMS tube 1, but is arranged symmetrically with respect to its mirror image. The second IMS tube 2 includes a second ion gate 20 having a second counter electrode 21 and a second injection electrode 22, where a second ionization chamber 23 is formed between the second injection electrode 22 and the second counter electrode 21. The other components of the second IMS tube 2 are a second drift chamber 24, a second field generating means 25, a second ion detector 26, a second drift gas inlet connection 27, and a second drift gas outlet connection 28. The corresponding elements of the second IMS tube 2 have the same functions as those described above for the components of the first IMS tube 1. For example, the first IMS tube 1 can be used to analyze positive ions, and the second IMS tube 2 is used to analyze negative ions.

[0077] In this case, the first counter electrode 11 and the second counter electrode 21 can also be embodied as a common counter electrode or electrically interconnected counter electrodes.

[0078] The ion mobility spectrometer further includes an ionization source 3 that provides ions in the first ionization chamber 13 and the second ionization chamber 23. The first ion gate 10 and the second ion gate 20 are each implemented as field-switching ion gates.

[0079] Figure 2Shows an advantageous embodiment of an ion mobility spectrometer, which also includes a first IMS tube 1 and a second IMS tube 2, and the rest includes the components already referred to Figure 1 in the description. Contrary to the Figure 1 embodiment, in Figure 2 , the IMS tubes 1, 2 are arranged close to each other substantially in parallel, thus resulting in a shorter structural length of the arrangement. In this case, a common ionization chamber made of the first ionization chamber 13 and the second ionization chamber 23 may be formed, and the common ionization chamber is supplied with ions by a common ionization source 3 as in the Figure 1 embodiment.

[0080] In the embodiment according to Figure 2 , the first ion gate 10 and the second ion gate 20 may each be constructed in the same manner as in the Figure 1 embodiment, that is, such that the corresponding injection electrode is arranged closer to the drift chamber facing the ion gate than the corresponding counter electrode. Figure 2 Shows a modified arrangement in this regard, in which the positions of the injection electrodes and the counter electrodes of the corresponding ion gates 10, 20 are interchanged. Obviously, the first injection electrode 12 is further away from the first drift chamber 14, and the first counter electrode 11 is arranged closer to the first drift chamber 14. In a similar manner, the second injection electrode 22 is further away from the second drift chamber 24, and the second counter electrode 21 is closer to the second drift chamber 24. This enables the first counter electrode 11 and the second counter electrode 21 to be implemented as a common counter electrode or at least as electrically interconnected counter electrodes. This simplifies the construction of the ion mobility spectrometer and the circuit construction required for the electrical operation of the ion mobility spectrometer.

[0081] Figure 3 Shows an ion mobility spectrometer having only one IMS tube 1. The ion mobility spectrometer has a construction equivalent to that of the first IMS tube 1 in the Figure 1 embodiment. Specifically, the components of the first ion gate 10 include a first counter electrode 11 and a first injection electrode 12, a first ionization chamber 13 is formed between the first counter electrode 11 and the first injection electrode 12, and a first drift chamber 14 is adjacent to the first ion gate 10. A first field generating device 15 is arranged in the region of the first drift chamber. A first ion detector 16 is arranged at the end of the first drift chamber 14. In addition, there are a first drift gas inlet connection 17 and a first drift gas outlet connection 18.

[0082] As an additional element, according to Figure 3The ion mobility spectrometer includes an additional electrode 19, which is arranged behind the first injection electrode 12 when viewed from the first counter electrode 11, for example, at the beginning of the first drift chamber 14. The first additional electrode 19 can be implemented as, for example, a ring electrode or a grid, similarly to the first injection electrode 12 or the first counter electrode 11. By applying a suitable potential to the first additional electrode 19 and by switching at least one other potential of the first ion gate 10, for example, the potential at the first injection electrode 12, methods for dual-field switching, for extended field switching, and for extended dual-field switching can be realized. The following will be described with reference to Figures 4 to 6 the timing diagrams in

[0083] Figures 4 to 6 shows the potential difference U with respect to the longitudinal extent s of the IMS tube 1. The potential difference U is the corresponding potential difference with respect to the first ion detector 16. The positions of the first counter electrode 11, the first injection electrode 12, the first additional electrode 19, and the first ion detector 16 are represented by vertical lines. In Figures 4 to 6 all examples, it is assumed that there is a linear potential distribution in the first drift chamber 14 with a relatively low potential gradient D and thus a relatively low field strength of the electric field.

[0084] Figure 4 shows an example of dual-field switching. In this case, the potential of the first injection electrode 12 is switched back and forth between two values. The solid line A represents the potential distribution when there is no electric field in the first ionization chamber 13, because no potential difference is generated between the first counter electrode 11 and the first injection electrode 12. In this stage, the ions to be analyzed can be generated by means of the ionization source 3 and provided into the first ionization chamber 13. Therefore, the first ion gate 10 is closed in this state.

[0085] If a sufficient number of ions to be analyzed have accumulated in the first ionization chamber 13, the potential at the first injection electrode 12 is switched so that the potential distribution represented by the dashed line B is established. Then, due to the descending potential distribution, the ion packet located in the first ionization chamber 13 moves from the first ionization chamber 13 in the direction towards the first drift chamber 14. In this case, the first compression of the ion packet is achieved. After a certain period of time, when it can be assumed that the ion packet has passed through the first injection electrode 12 but has not passed through the first additional electrode 19, the potential at the first injection electrode 12 is switched back to the value that first occurred, so that the potential distribution represented by the solid line A appears again. In this state, as described above, the field strength in the first ionization chamber is substantially equal to zero. Then there is a relatively steep potential gradient, and thus a relatively strong electric field, in the space between the first injection electrode 12 and the first additional electrode 19, which results in the second compression of the ion packet located in this gap. The ion packet that has now been compressed for the second time is then transferred to the first drift chamber 14.

[0086] It is also apparent that it may be advantageous to define a second potential value which is applied to the first injection electrode 12 and which results in a potential distribution according to dashed line B such that, in this operating phase, the potential gradient between the first injection electrode 12 and the first additional electrode 19 is at least substantially equal to the potential gradient D in the first drift chamber 14. In this way, it is ensured that the ion packet is uniformly transferred from the gap between the first injection electrode 12 and the first additional electrode 19 into the first drift chamber 14. Figure 4

[0087] Figure 5 An example of extended field switching is shown. Here, the potential of the first injection electrode 12 also switches back and forth between two different values. First, it should be assumed that the potential value which results in the potential distribution represented by solid line A is applied to the first injection electrode 12. In this state, the first ion gate 10 is in the closed state, i.e., the first ionization chamber 13 is substantially free of an electric field. In addition, the potential at the first injection electrode 12 is selected such that the potential is also constant in the gap between the first injection electrode 12 and the first additional electrode 19 and thus this space is also substantially free of an electric field. In this way, it is possible to prevent the electric field caused by the potential gradient D in the first drift chamber 14 from penetrating into the first ionization chamber 13.

[0088] Then the potential at the first injection electrode 12 is switched to a different value such that the potential distribution represented by dashed line B is established. In this case, the potential gradient between the first counter electrode 11 and the first injection electrode 12 corresponds, for example, to the potential distribution represented by dashed line B in Figure 4 ; likewise, the potential distribution between the first injection electrode 12 and the first additional electrode 19 can correspond to the potential distribution represented by dashed line B in reference to Figure 4 . Thus, in this state, the first ion gate switches to transmission such that the ion packet moves from the first ionization chamber 13 into the first drift chamber 14.

[0089] Figure 6 An exemplary potential distribution in the case of extended dual field switching is shown and thus a combination of the methods described above with reference to Figure 4 and Figure 5 . In this case, the potential at the first injection electrode 12 switches between three different values. It should be assumed that the sequence starts with the potential distribution according to solid line A. In this state, the first ion gate 10 is closed, or in other words, this state corresponds to the state described above with reference to Figure 5 according to solid line A therein. The first ionization chamber 13 as well as the gap between the first injection electrode 12 and the first additional electrode 19 are substantially free of an electric field. Thus, the first additional electrode 19 can perform its function of shielding against field penetration from the first drift chamber 14.

[0090] Then, the potential at the first injection electrode 12 is switched so that a potential distribution indicated by the dashed line B is generated. In this state, the first ion gate 10 is opened. The ion packets that have accumulated in the first ionization chamber 13 move in the direction toward the first drift chamber 14 and are compressed for the first time in the process. This corresponds to the above reference Figure 4 and Figure 5 The same sequence is produced in the case of the potential distribution according to the dashed line B in the illustrated example.

[0091] The potential of the first injection electrode 12 is then switched again, so that the potential distribution represented by the dotted line C is generated. In this state, the first ion gate 10 is closed again. Therefore, the first ionization chamber 13 is essentially free of an electric field. However, in contrast to the potential distribution represented by the solid line A, this field-free state of the first ionization chamber 13 is obtained at a higher potential value. Therefore, in the gap between the first injection electrode 12 and the first additional electrode 19, there is a relatively strong electric field, i.e., a significant potential gradient, so that the ions located in the gap are compressed a second time before being transferred to the first drift chamber 14. In this case, the potential distribution according to the dotted line C may correspond, for example, to the potential distribution according to Figure 4 The solid line A is the potential distribution.

[0092] The potential at the first injection electrode 12 is then switched again to the value mentioned first, so that the potential according to Figure 6 The solid line A is the potential distribution.

[0093] Figure 7 A further embodiment of an ion mobility spectrometer with two drift chambers is shown, which are arranged one behind the other, i.e. as in Figure 1 As in the embodiment of Figure 1 In contrast to the embodiment, Figure 7 The ion migration spectrometer in the embodiment comprises a first additional electrode 19 in the IMS tube 1 and a second additional electrode 29 in the IMS tube 2. Thus, an ion migration spectrometer with two drift chambers can be provided, for example an ion migration spectrometer with bipolarity, which has corresponding functions for performing dual field switching, extended field switching and extended dual field switching. In this case, the potentials at the respective injection electrodes of the first ion gate 10 and the second ion gate 20 will be as described above for a system with only one IMS tube 1. Figure 3 It goes without saying that if it is intended to analyze ions with different polarities in the respective IMS tubes 1 , 2 , the potentials at the first injection electrode 12 and the second injection electrode 22 are switched in an opposite manner.

[0094] Figure 8 Another embodiment of an ion mobility spectrometer is shown, which is similar to Figure 7 Embodiment of. Figure 7Conversely, the first counter electrode 11 and the second counter electrode 21 are omitted. Accordingly, a common ionization chamber made up of the first ionization chamber 13 and the second ionization chamber 23 is also formed. Thus, the structure of the ion mobility spectrometer is simplified. Additionally, ion loss can be further minimized. Nevertheless, all functions of the ion mobility spectrometer can still be achieved, including the above-mentioned extensions to dual-field switching, extended-field switching, and extended dual-field switching.

[0095] Figure 9 Shows the exemplary potential distribution of an ion mobility spectrometer when dual-field switching is implemented according to Figure 8 Similar to the illustration in Figures 4 to 6 The potential difference U with respect to the longitudinal range s of the ion mobility spectrometer is again shown. Additionally, the positions of the first ion detector 16 and the second ion detector 26, the first injection electrode 12 and the second injection electrode 22, and the first additional electrode 19 and the second additional electrode 29 are shown. Here, in different cases, the potential at the first injection electrode 12 and the second injection electrode 22 switches back and forth between two different values. The potential distribution with the solid line A represents the state where the ion gates 10, 20 are closed. In the common ionization chamber, there is thus a space without an electric field, and ions can be provided by the ionization source 3.

[0096] Then, the potential at the first injection electrode 12 and the second injection electrode 22 is switched in the opposite manner, such that the potential distribution represented by the dashed line B is generated. In this way, positive ions and negative ions are separated from each other and are transmitted as corresponding separate ion packets in the direction towards the respective first drift chamber 14 or second drift chamber 24. In this case, the first compression of the corresponding ion packets is achieved.

[0097] Once the corresponding ion packet has passed through the injection electrode 12 or 22 assigned to it respectively, the potential distribution can be switched back to the distribution according to the solid line A. In this state, there is a relatively steep potential gradient in the respective gaps between the first injection electrode 12 / the first additional electrode 19 and the second injection electrode 22 / the second additional electrode 29. Thus, the second compression of the corresponding ion packets is achieved. In this case, the sequence corresponds to the sequence already described with reference to Figure 4 for one IMS tube 1. The sequence of the second IMS tube 2 is the same, but with the opposite polarity.

[0098] In the case where such ion gates include injection electrodes and counter electrodes, in many applications, the injection electrodes are arranged closer to the drift chamber assigned to the ion gate than the counter electrodes. In some applications, for example, in the case of an ion mobility spectrometer with bipolarity, the arrangement can also be reversed, i.e., in such cases, the counter electrodes are arranged closer to the drift chamber assigned to the ion gate than the injection electrodes.

[0099] Even in accordance with Figure 8In an embodiment of the ion mobility spectrometer, there are no first and second counter electrodes as separate components, and the function of the counter electrode still exists in the case of the switching of the potential at the described injection electrode. With respect to the IMS tube 1 to which the first ion gate 10 is assigned, the second injection electrode 22 performs the function of the first counter electrode. In a corresponding manner, for the second IMS tube 2 to which the second ion gate 20 is assigned, the first injection electrode 12 performs the function of the second counter electrode. As is evident, the first injection electrode 12 and the second injection electrode 22 in this embodiment have the functions of the above-mentioned first multi-functional electrode and second multi-functional electrode.

[0100] It is also possible to switch the potential at the respective counter electrode and the respective injection electrode of the ion gate, and to use the arrangement composed of the three electrodes mentioned above, namely the counter electrode, the injection electrode, and the additional electrode, to perform the methods of dual-field switching, extended-field switching, and / or extended dual-field switching.

[0101] Figure 10 An ion mobility spectrometer is shown having two drift chambers 14, 24 arranged in an axially aligned manner, and the spectrometer is much simpler than the embodiment Figure 8 described. According to Figure 10 's embodiment, it again includes two multi-functional electrodes formed by the first injection electrode 12 and the second injection electrode 22. Compared with Figure 8 's embodiment, Figure 10 's embodiment lacks the first additional electrode 19 and the second additional electrode 29. Even with this further simplified embodiment of the dual ion mobility spectrometer, the desired functions in ion analysis can be achieved.

[0102] Figure 11 An embodiment showing the potential distribution in the drift chambers 14, 24 and the common ionization chambers 13, 23 is shown. According to Figure 11 , during the ion generation period, there is a potential distribution substantially the same as that of Figure 8 's embodiment, but there is no potential gradient between the respective injection electrode and the additional electrode, because there is no additional electrode in Figure 10 's embodiment. This is represented by the solid line in Figure 11 . According to the field switching principle, there is a potential gradient A in the common ionization chambers 13, 23, and due to this potential gradient, there is substantially no electric field in the ionization chambers 13, 23. There are drift fields with a potential gradient D in the first drift chamber 14 and the second drift chamber 24. If, after a sufficient number of ions have accumulated in the ionization chambers 13, 23, the field-switching ion gate is then switched so that the ions are transferred to the respective drift chambers 14, 24 (ion injection period), then this is achieved by switching the potential at the injection electrodes 12, 22, as shown by Figure 11The dotted lines therein represent. Then there is a relatively steep potential gradient B in the ionization chambers 13, 23. The potential levels change in the respective drift chambers 14, 24, where the potential gradient E, i.e., the corresponding slope of the potential over the distance s, remains the same and corresponds to the slope of the potential gradient D. This is achieved by switching the potential at the respective detectors 16, 26 to the same amplitude as the potential at the respective injection electrodes 12, 22.

[0103] Compared with Figure 11 in Figure 12 FIG. shows an alternative embodiment of the switching of the potential. During the ion generation period, there is the same state as in Figure 11 i.e., a substantially neutral potential gradient A in the common ionization chambers 13, 23 and the corresponding potential gradients D in the drift chambers 14, 24. During the switching of the field-switching ion gates for transferring the ions to the respective drift chambers 14, 24, the same potential switching at the respective injection electrodes 12, 22 as described according to Figure 11 is achieved, i.e., a potential gradient B is generated in the common ionization chambers 13, 23. However, in contrast to Figure 11 here, the potential at the detectors 16, 26 is not switched. This results in the corresponding potential gradients E in the drift chambers 14, 24 being smaller in magnitude than the potential gradient D, such that compared with the variant in Figure 11 the movement speed of the ions in the respective drift chambers 14, 24 is lower initially, i.e., during the ion injection period. Then it is possible to switch again to a higher potential gradient, for example, the potential gradient D.

[0104] The type of potential switching described above with reference to the embodiment of the ion mobility spectrometer according to Figure 10 can also be advantageously used in the embodiment of the ion mobility spectrometer according to Figure 8 In the embodiment according to Figure 8 in addition to the multifunctional electrodes formed by the injection electrodes 12, 22, there are also additional electrodes 19, 29. This is also considered to be the basis in the embodiment of the ion mobility spectrometer according to Figure 13 which is equivalent to the embodiment of Figure 8 In this ion mobility spectrometer, potential switching can be achieved according to Figure 14 In this case, the potential distribution and the switching between the potential gradients A and B correspond to the embodiment in Figure 11 Similarly, similar to Figure 11 in the respective drift chambers 14, 24, the potential gradient undergoes a parallel displacement between the ion generation period (potential gradient D) and the ion injection period (potential gradient E) (i.e., the period when the ions are transferred to the respective drift chambers 14, 24). In this case, the potential gradients D, E extend parallel to each other, which is achieved by switching the potential at the respective detectors 16, 26.

[0105] Furthermore, during the ion generation period in the respective space between the first injection electrode 12 and the first additional electrode 19 or between the second injection electrode 22 and the second additional electrode 29, a potential gradient is set, which is largely neutral, i.e., substantially corresponding to the potential gradient A, but in this case may have a small slope opposite to the potential gradient D in the respectively assigned drift chambers 14, 24. In this way, the penetration of the electric field from the respective drift chambers 14, 24 into the common ionization chambers 13, 23 can be cancelled by the respective additional electrodes 19, 29.

[0106] The switching of the potential can also be achieved according to Figure 15 and the type of potential switching is substantially corresponding to Figure 12 the embodiments in Figure 12 As in Figure 15 the potential at the detectors 16, 26 is not switched, which results in the potential gradient E being smaller in magnitude than the potential gradient D.

[0107] Figure 16 Fig. shows an embodiment of an ion mobility spectrometer with axially arranged drift chambers 14, 24, in which, in addition to the multi-functional electrodes, namely the first injection electrode 12 and the second injection electrode 22 and the first additional electrode 19 and the second additional electrode 29, there are also corresponding additional first additional electrodes 31 and additional second additional electrodes 32, and the additional electrodes 31, 32 are arranged upstream of the respective additional electrodes 19, 29 in the direction of the respective drift chambers 14, 24.

[0108] Figure 17 Fig. shows Figure 16 the advantageous potential distribution of the ion mobility spectrometer according to

[0109] Figure 18 Fig. shows an ion mobility spectrometer with parallel arranged drift chambers 14, 24, which is substantially corresponding to Figure 2 the embodiments in Figures 19 to 22Shows the advantageous potential distributions during the ion generation period and the ion implantation period. In this case, the upper half of each figure shows the potential distribution in the upper half of the ion mobility spectrometer, and the lower half of the figure shows the potential distribution in the lower half of the ion mobility spectrometer. For further distinction, here, the potential distribution in the upper half of the ion mobility spectrometer is represented by a solid line, and the potential distribution in the lower half is represented by a dotted line. This assignment also applies to Figures 24 to 27 and Figures 29 to 32 .

[0110] Figure 19 Shows the potential distribution during the ion generation period, and Figure 20 shows the associated potential distribution during the ion implantation period. It is assumed here that the two field-switching ion gates use a common injection electrode 12, 22, or these injection electrodes 12, 22 are at the same potential. A common counter electrode 11, 21 is also possible. In this case, Figure 19 and Figure 20 show the advantageous switching cycles during the normal field-switching operation of the ion gates 10, 20. In this case, the potential is switched only at the respective counter electrodes 11, 21.

[0111] In contrast, Figure 21 and Figure 22 show the potential distribution in which the potential is switched at both the injection electrodes 12, 22 and the counter electrodes 11, 21, which results in an intersecting distribution of the potential in the ionization chambers 13, 23 in Figure 22 . In this case, Figure 21 shows again the potential distribution during the ion generation cycle, and Figure 22 shows the potential distribution during the ion implantation cycle.

[0112] According to Figure 21 and Figure 22 The advantages of the embodiments are that there is the same field strength between the respective pair of counter electrodes and injection electrodes, but the potential difference between the counter electrodes 11, 21 is smaller. Therefore, for example, malfunctions can be prevented. In addition, since some potentials can be used diversely, the driving is simplified. As is obvious, if the same potential gradient is ultimately to be obtained in the drift chambers 14, 24, it basically corresponds to Figure 11 , Figure 12 The method according to Figure 21 and Figure 22 The embodiments require potential switching at the respective detectors 16, 26. Alternatively, the potential at the respective detectors can be kept constant, which results in a reduced potential gradient in the respective drift chambers 14, 24.

[0113] Figure 23 Shows to a large extent corresponding to Figure 18the ion mobility spectrometer of the embodiments in. As opposed to Figure 18 In contrast, in Figure 23 the embodiments of, the corresponding first additional electrode 19 and second additional electrode 29 are arranged upstream of the respective drift chambers 14, 24. Thus, in Figure 23 the embodiments of, it is possible to advantageously perform extended field switching in both ion gates.

[0114] Figure 24 and Figure 25 show Figure 23 the possible potential distributions of the embodiments of, wherein according to Figure 24 and Figure 25 the potential distributions are largely corresponding to Figure 19 and Figure 29 the embodiments of. In this case, in the space between the respective injection electrodes and the additional electrodes, a shielding field is generated having an opposite gradient corresponding to the field in the respective drift chamber, in order to cancel the penetration of the field from the drift chamber into the ionization chamber. In this case, Figure 24 shows the potential distribution during the ion generation period, and Figure 25 shows the potential distribution during the ion injection period.

[0115] Figure 26 and Figure 27 show potential distributions comparable to Figure 21 and Figure 22 . As opposed to Figure 21 and Figure 22 , in Figure 26 and Figure 27 , again a corresponding field between the injection electrode and the additional electrode is generated for canceling the field penetration. In this case, Figure 26 shows the potential distribution during the ion generation period, and Figure 27 shows the potential distribution during the ion injection period.

[0116] Figure 28 shows an embodiment of an ion mobility spectrometer largely corresponding to Figure 23 the embodiments in. As opposed to Figure 23 , in Figure 28 the embodiments there are also the already mentioned additional first additional electrode 31 and additional second additional electrode 32. In this case, the additional first additional electrode 31 is arranged upstream of the first additional electrode 19 in the direction of the drift chamber 14, and the additional second additional electrode 32 is arranged upstream of the second additional electrode 29 in the direction of the second drift chamber 24.

[0117] In Figure 28 the embodiments, this configuration of the electrodes enables both extended field switching and dual field switching, i.e., the compression of the ion packet in the second compression step.

[0118] Figure 29 and Figure 30 shows a favorable potential distribution of an ion mobility spectrometer according to Figure 28 which is embodied similar to the switching logic in Figure 19 and Figure 20 . Figure 29 shows the potential distribution in the ion generation period, and Figure 30 shows the potential distribution in the ion injection period.

[0119] Figure 31 and Figure 32 show potential distributions similar to the embodiments in Figure 21 and Figure 22 . Obviously, particularly in the ion generation cycle, a relatively steep potential gradient is generated in the space between the corresponding additional electrode and another additional electrode. Figure 31 shows the potential distribution in the ion generation period, and Figure 32 shows the potential distribution in the ion injection period.

[0120] Therefore, based on the steep potential gradient, Figure 29 and Figure 31 also show possible potential distributions in the second compression step during dual-field switching.

[0121] List of reference numerals

[0122] 1, 2 Ion mobility spectrometers (first IMS tube, second IMS tube)

[0123] 3 Ionization source

[0124] 10 First ion gate

[0125] 11 First counter electrode

[0126] 12 First injection electrode

[0127] 13 First ionization chamber

[0128] 14 First drift chamber

[0129] 15 First field generation device

[0130] 16 First ion detector

[0131] 17 First drift gas inlet connector

[0132] 18 First drift gas outlet connector

[0133] 19 First additional electrode

[0134] 20 Second ion gate

[0135] 21 Second counter electrode

[0136] 22 Second injection electrode

[0137] 23 Second ionization chamber

[0138] 24 Second drift chamber

[0139] 25 Second field generation device

[0140] 26 Second ion detector

[0141] 27 Second drift gas inlet connector

[0142] 28 Second drift gas outlet connector

[0143] 29 Second additional electrode

[0144] 31 Additional first additional electrode

[0145] 32 Additional second additional electrode

[0146] A Solid line

[0147] B Dashed line

[0148] C Dotted line

[0149] D Electric potential gradient

[0150] U Electric potential

[0151] s Longitudinal range

Claims

1. A method for analyzing a sample by ion mobility spectrometry using an ion mobility spectrometer, the ion mobility spectrometer comprising at least a first drift chamber (14) and a switchable first ion gate (10) for controllably transferring ions into the first drift chamber (14), wherein the first ion gate (10) is implemented as a field-switching ion gate comprising at least a first counter electrode (11) and a first injection electrode (12), wherein a first ionization chamber (13) is formed between the first counter electrode (11) and the first injection electrode (12), and ions to be analyzed by ion mobility spectrometry can be fed from an ionization source (3) into the first ionization chamber, wherein at least one first additional electrode (19) is arranged between the first ion gate (10) and the first drift chamber (14), and ions transferred into the first drift chamber (14) by means of the first ion gate (10) can additionally be influenced by the first additional electrode, wherein, by means of the ionization source (3), ions to be analyzed are generated from the sample and provided in the first ionization chamber (13), and the ions generated in the process are guided into the first drift chamber (14) under the control of the first ion gate (10), wherein the first ionization chamber (13) has no electric field at least during the ion generation period, characterized by one or both of the following features a), b): a) Before the ion packet is transferred into the first drift chamber (14), by switching the potential difference between the first injection electrode (12) and the first counter electrode (11), the ion packet provided in the first ionization chamber (13) is compressed for the first time in a first compression step, and after passing through the first injection electrode (12), by switching the potential difference between the first additional electrode (19) and the first injection electrode (12), the ion packet is compressed for the second time at least in a second compression step, b) At least during the ion generation period, the ions generated in the first ionization chamber (13) are at least partially shielded from the electric field generated in the first drift chamber (14) by the first additional electrode (19), At least during the ion generation period, the potential gradient between the first injection electrode (12) and the first additional electrode (19) for shielding is equal to zero or opposite to the potential gradient in the first drift chamber (14).

2. The method according to claim 1, wherein The opening and closing of the first ion gate (10) are achieved by switching the potentials of the first injection electrode (12) and / or the first counter electrode (11) of the corresponding ion gate.

3. The method according to claim 1, wherein In the first compression step, the potential gradient between the first counter electrode (11) and the first injection electrode (12) is greater than the potential gradient in the first drift chamber (14).

4. The method according to claim 1, wherein In the second compression step, the potential gradient between the first injection electrode (12) and the first additional electrode (19) is greater than the potential gradient in the first drift chamber (14).

5. The method according to claim 1, characterized in that The potential gradient between the first injection electrode (12) and the first additional electrode (19) is greater in the second compression step than in the first compression step.

6. The method according to claim 1, wherein In the first compression step, the potential gradient between the first injection electrode (12) and the first additional electrode (19) is equal to the potential gradient of the first drift chamber (14).

7. The method according to claim 1, characterized in that, In the first compression step, the potential gradient between the first injection electrode (12) and the first additional electrode (19) is greater than the potential gradient between the first counter electrode (11) and the first injection electrode (12) and greater than the potential gradient of the first drift chamber (14).

8. The method according to claim 1, characterized in that, When switching to the first compression step, the potential gradient between the first injection electrode (12) and the first additional electrode (19) is switched later than the potential gradient between the first counter electrode (11) and the first injection electrode (12).

9. The method according to claim 1, wherein When leaving the first compression step, the potential gradient between the first counter electrode (11) and the first injection electrode (12) is switched earlier than the potential gradient between the first injection electrode (12) and the first additional electrode (19).

10. The method according to claim 1, characterized in that, The ion mobility spectrometer further includes a second drift chamber (24) separate from the first drift chamber (14) and a switchable second ion gate (20) for controllably transferring ions into the second drift chamber (24), wherein the second ion gate (20) is implemented as a field-switching ion gate including at least a second counter electrode (21) and a second injection electrode (22).

11. An ion mobility spectrometer, comprising at least a first drift chamber (14) and a switchable first ion gate (10) for controllably transferring ions into the first drift chamber (14), wherein the first ion gate (10) is implemented as a field-switching ion gate comprising at least a first counter electrode (11) and a first injection electrode (12), wherein a first ionization chamber (13) is formed between the first counter electrode (11) and the first injection electrode (12), and ions to be analyzed by ion mobility spectrometry can be fed from an ionization source (3) into the first ionization chamber, wherein at least one first additional electrode (19) is arranged between the first ion gate (10) and the first drift chamber (14), and ions transferred into the first drift chamber (14) by means of the first ion gate (10) can additionally be influenced by the first additional electrode, characterized in that, The ion mobility spectrometer is configured to perform the method according to any one of claims 1 to 10.

12. The ion mobility spectrometer according to claim 11, wherein The first additional electrode (19) is arranged at an end of the first drift chamber (14) facing the first ion gate (10).

13. The ion mobility spectrometer according to claim 11, wherein, The distance between the first additional electrode (19) and the first injection electrode (12) is less than the distance between the first counter electrode (11) and the first injection electrode (12).

14. The ion mobility spectrometer according to claim 11, wherein, The first additional electrode (19) is implemented in a non-switchable potential manner.

15. The ion mobility spectrometer according to claim 11, wherein, The first additional electrode (19) is implemented in a switchable potential manner.

16. The ion mobility spectrometer according to claim 11, characterized in that, The ion mobility spectrometer at least includes a second drift chamber (24) separate from the first drift chamber (14) and a switchable second ion gate (20) for controllably transferring ions into the second drift chamber (24), wherein the second ion gate (20) is implemented as a field-switching ion gate including at least a second counter electrode (21) and a second injection electrode (22).

17. The ion mobility spectrometer according to claim 16, wherein The ion mobility spectrometer does not include an additional first field generating device (15) for generating an electric field in the first ionization chamber (13) such that an electric field can be generated in the first ionization chamber (13) only by the electrodes of the first ion gate (10).

18. The ion mobility spectrometer according to claim 11, characterized in that, The ion mobility spectrometer includes an X-ray ionization source, a UV ionization source, a corona ionization source, a plasma ionization source, a dielectric barrier discharge source, and / or an electron emitter as an ionization source (3).

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