Patent Application
20230136178
The present invention relates to a mass spectrometer.
A mass spectrometer is a device ionizing a sample and analyzing ions according to a mass-to-charge ratio. In general, a mass spectrometer includes an ion source ionizing a sample, a mass spectrometry unit separating the ions according to a mass-to-charge ratio, and a detection unit detecting a quantity of the ions having passed through the mass spectrometry unit.
As a technology on an ion guide separating ions and an air flow, there is the description of U.S. Pat. No. 8,581,182 (Patent Literature 1). In this gazette, there is described an ion guide separating ions and an air flow by that the ions are transferred from the first ion guide to the second ion guide by overriding a pseudopotential barrier between the first ion guide and the second ion guide by DC potential.
Also, there is the pamphlet of WO 2016/135810 (Patent Literature 2). In this gazette, there is described an ion guide in which two rod electrode sets forms a single multipole ion guide in a region where the two rod electrode sets overlap with each other in the longitudinal direction, ions are transferred to the first rod electrode set to the second rod electrode set by a DC potential difference between the first rod electrode set and the second rod electrode set in the overlapping region, and thereby ions and an air flow are separated from each other.
[Patent Literature 1] Description of U.S. Pat. No. 8,581,182
[Patent Literature 2] Pamphlet of WO 2016/135810
However, according to the prior arts, there was a problem that there was a limit in ion permeation efficiency.
As one of concrete configuration examples in prior arts, in Patent Literature 1, there is described an example of an aspect where an exhaust port is disposed on the center axis of the first ion guide, and an air flow having passed through the first ion guide is discharged. However, since the position of the exhaust port is limited, the diameter of the exhaust port is limited. When the diameter of the exhaust port is small, the discharge efficiency lowers, and the degree of vacuum of a space where the ion guide is disposed lowers. When the degree of vacuum is low, the mean free path of ions becomes small, and the ion permeation efficiency lowers.
Further, although another concrete configuration example in prior arts is described in Patent Literature 2, there is no description on control of an air flow after ions and the air flow are separated from each other in Patent Literature 2. According to the configuration of Patent Literature 2, there is a problem that a turbulent flow occurs by collision of an air flow on a wall surface of the vacuum chamber where the ion guide is disposed, ions and the sir flow are mixed, and thereby the ion permeation efficiency lowers.
The present invention has been achieved to solve such problem, and there is provided a mass spectrometer for higher ion permeation efficiency.
In an example of a mass spectrometer according to the present invention, an air flow including ions is separated into an air flow and an ion flow by an ion guide in the first vacuum chamber, and the first vacuum chamber includes a straightening member reducing mixing of the air flow and the ion flow having been separated from each other.
The present specification includes the content of disclosure of Japanese Patent Application No. 2020-038168 that becomes a basis of priority of the present application.
According to a mass spectrometer according to the present invention, the ion permeation efficiency is improved.
Embodiments of the present invention will be hereinafter explained using the drawings.
In the present example, a comparatively simple embodiment will be explained.
In the ion source 101, a measurement sample is ionized by a method such as an electrospray ionization method, an atmospheric pressure chemical ionization method, an atmospheric pressure photoionization method, and a matrix-assisted laser desorption ionization method.
The ions generated in the ion source 101 enter the first vacuum chamber 107 through the pore 102. However, the concrete construction of the pore 102 can be designed optionally, may be one where a small hole is bored in a thin wall surface, and may be one like a fine tube where a small hole is bored in a thick wall surface for example.
It is also possible that an electrode and a vacuum chamber where ions pass though are provided before the first vacuum chamber 107.
Neutral molecules, the air, minute water drops and the like also enter the first vacuum chamber 107 the first vacuum chamber 107 through the pore 102 along with the ions. For the purpose of discrimination. A flow of ions reaching the pore 104 is defined to be an ion flow 703, and a flow of other than that is defined to be an air flow 704. In the air flow 704, not only the neutral molecules, the air, and the minute water drops described above but also a part of ions which cannot reach the pore 104 are included.
In the first vacuum chamber 107, there is disposed the ion guide 103 having a function of separating the ion flow 703 and the air flow 704 from each other. Also, the first vacuum chamber 107 includes the current plate 113. Actions of a mechanism and the current plate 113 will be described below, the mechanism being for separating the ion flow 703 and the air flow 704 from each other. The ion flow 703 separated from the air flow 704 by the ion guide 103 reaches the pore 104, and enters the second vacuum chamber 108.
The ion flow 703 having reached the pore 104 enters the second vacuum chamber 108. The second vacuum chamber 108 includes the mass spectrometry unit 105. In the mass spectrometry unit 105, the ions are separated according to the mass-to-charge ratio by an electrical and/or magnetic action. For example, there are a magnetic field type where the trajectory of the ion is bent by a magnetic field, a quadrupole type where ions are separated by applying a radio frequency voltage (RF voltage) or a direct current voltage (DC voltage) to an electrode whose section is a bipolar plane, a flying time type where ions are detected by difference of the flying time, and so on.
The ions having been analyzed by the mass spectrometry unit 105 are detected by the detector 106. In the detector 106, the ions are detected by converting an ion signal into an electric signal utilizing a photoelectron multiplier tube and an electron multiplier tube for example.
Thus, the mass spectrometer causes the ions generated by the ion source 101 to pass through the first vacuum chamber 107 and the second vacuum chamber 108, and transfers the same toward the detector 106.
The air in the first vacuum chamber 107 is discharged by the vacuum pump 109, and the air in the second vacuum chamber 108 is discharged by the vacuum pump 110. Although the first vacuum chamber 107 and the second vacuum chamber 108 communicate with each other by the pore 104, since the diameter of the pore 104 is limited, the first vacuum chamber 107 and the second vacuum chamber 108 are different from each other in terms of the pressure inside the chamber.
The first vacuum chamber 107 is close to the ion source 101 which is under the atmospheric pressure, and the pressure within the first vacuum chamber 107 is higher than the pressure within the second vacuum chamber 108. The vacuum pump 109 and the vacuum pump 110 may be of the same type. Also, the vacuum pump 109 and the vacuum pump 110 may be a single pump respectively, and may be a system obtained by combining plural kinds of pumps such as combined usage of a turbo-molecular pump and a dry pump for example.
The first vacuum chamber 107 and the vacuum pump 109 are connected to each other by the exhaust port 111, and the second vacuum chamber 108 and the vacuum pump 110 are connected to each other by the exhaust port 112. With respect to the exhaust port 111 and the exhaust port 112, as the diameter is larger, as there are less number of curves, and as the length to the vacuum pump 109 or the vacuum pump 110 is shorter, the exhaust efficiency is higher, and the pressure of the first vacuum chamber 107 and the second vacuum chamber 108 becomes lower. When the pressure of the first vacuum chamber 107 and the second vacuum chamber 108 is low, since the mean free path of ions becomes large, the permeation efficiency of the ion flow 703 becomes high.
A schematic drawing of the ion guide 103 is shown in
Although a configuration example of the ion guide 103 will be hereinafter explained, the configuration of the ion guide 103 is not limited to it and can be designed or changed optionally based on a known technology. For example, a part of the configurations described in Patent Literature 1 or 2 may be applied. Also, with respect to a portion where description is omitted on the detail of the ion guide 103, description on Patent Literature 1 or 2 or other known technologies can be incorporated herein.
As the two electrode sets, in the X-axis direction, a first electrode set 201 is disposed on a side the ion flow 703 and the air flow 704 enter, and a second electrode set 202 is disposed on a side the ion flow 703 exits.
In
In
The ion guide 103 shown in
In an example of
Also, the configuration of the rod electrode in the ion guide is not limited to it but can be designed optionally, and can be formed of even number of piece of the rod electrodes in each of the regions 1 to 3.
To the first electrode set 201 and the second electrode set 202, an RF voltage and an offset DC voltage are applied, and thereby the ion flow 703 and the air flow 704 are separated from each other.
Signs “+” and “−” shown in
In an example of
In the ion guide 103 having the configuration of
In the region 1, when ions within a specific mass-to-charge ratio range enter a portion where the first electrode set 201 is disposed, the ions are converged and proceed toward the center of the first electrode set 201. The mass-to-charge ratio range where convergence takes place is determined depending on the frequency and the amplitude of the RF voltage to be applied. Therefore, it is required to adjust the frequency and the amplitude of the RF voltage by the mass-to-charge ratio of the ions which are intended to reach the pore 104.
In the region 2, there is no barrier of the pseudopotential between the first electrode set 201 and the second electrode set 202. That is to say, the ion guide 103 forms a single ion guide in the region 2. Therefore, the ions can go back and forth freely between the first electrode set 201 and the second electrode set 202. Also, since it is not required to impart the ions with strong energy to override a potential barrier, the quantity of ions passing through the center axis of the second electrode set 202 and flying out to the opposite side can be reduced.
In the region 3, similarly to the region 1, when ions within a specific mass-to-charge ratio range enter a portion where the second electrode set 202 is disposed, the ions proceed while being converged toward the center of the second electrode set 202.
Also, to the first electrode set 201 and the second electrode set 202, an offset DC voltage of electric potential different from each other is applied. At this time, when the positive ions are intended to pass to the pore 104, a voltage lower than that of the second electrode set 202 is applied to the second electrode set 202, whereas when the negative ions are intended to pass to the pore 104, a voltage higher than that of the second electrode set 202 is applied to the second electrode set 202.
Further, from now on, although there is a case of giving explanation where the magnitude relation ship of the electric potential is limited to a case of separating the positive ions, the explanation is applicable to a case of separating the negative ions if the magnitude relation ship of the electric potential is reversed.
When the off set DC voltage applied to each electrode is changed and the DC potential gradient is changed, the permeation efficiency of the ion flow 703 changes. This occurs by a cause that, for example, when the DC potential gradient is large, the kinetic energy of the ions becomes large, and the convergence efficiency of the ion flow 703 drops in the second electrode set 202. Therefore, in a similar manner to the RF voltage, it is required to adjust the DC potential gradient according to the mass-to-charge ratio of the ions which are intended to permeate through to the pore 104.
When an ion incidence point of the first electrode set 201 is located within a range of several millimeters from the pore 102, the convergence efficiency of the ion becomes high which is preferable. Here, “ion incidence point” means for example the center of the first electrode set 201 at the incident side end in the X-axis direction of the first electrode set 201. The distance (distance in the three-dimensional space) of the ion incidence point from the pore 102 can be made 5 mm, 1 cm, 2 cm, and the like for example.
Also, it is preferable when the center of the second electrode set 202 is disposed at a position getting into alignment (so as to be generally coaxial for example) with the pore 104 at least at an exit side end in the X-axis direction of the second electrode set 202. Also, when an ion exit point of the second electrode set 202 is located within a range of several millimeters from the pore 104, the convergence efficiency of the ion becomes high which is preferable. Here, “ion exit point” means for example the center of the second electrode set 202 at the exit side end in the X-axis direction of the second electrode set 202. The distance (distance in the three-dimensional space) of the ion exit point from the pore 104 can be made 5 mm, 1 cm, 2 cm, and the like for example.
Here, as a comparative example for explaining an action of the present invention, movement of the ion flow 703 and the air flow 704 within the first vacuum chamber 107 when the ion guide 103 of
Since there is a pressure difference before and after the pore 102, a barrel shock 701 and a Mach disk 702 are formed. By this impact, immediately after passing through the pore 102, the ion flow 703 and the air flow 704 proceed within the first vacuum chamber 107 with a diameter generally the same as that of the Mach disk 702. The diameter of the Mach disk 702 is determined depending on the diameter of the pore 102 and the pressure before and after the pore 102.
The ion flow 703 having diffused at the time of entering the pore 102 is converged to the center of the first electrode set 201 by the action of the RF voltage described above, and proceeds within the first electrode set 201. When the ion flow 703 reaches the region 2, the ion flow 703 moves from the vicinity of the center of the first electrode set 201 to the center of the second electrode set 202 by the action of the offset DC voltage described above, and proceeds straight toward the pore 104 near the center of the second electrode set 202.
On the other hand, since a substance such as the neutral molecule hardly receiving an electrical action gets mixed much into the air flow 704, the air flow 704 passes the vicinity of the first electrode set 201 with a diameter generally the same as that of the Mach disk 702. However, different from the ion flow 703, the air flow 704 hardly moves toward the second electrode set 202. By such mechanism, the ion flow 703 and the air flow 704 are separated from each other in the ion guide 103.
In the comparative example of
An example of an aspect of the current plate 113 according to the example 1 of the present invention and the situation of the movement of the ion flow 703 and the air flow 704 when the current plate 113 is utilized are shown in
Although the shape of the current plate 113 is optional, it is a rectangular parallelepiped according to the present example, and is of a plate-like shape where the length in the X-axis direction (thickness) is small and the area of the X-Y plane is large. With such shape, manufacturing is easy. The thickness of the current plate 113 can be made 3 mm for example. The length in the X-axis direction of the current plate 113 can be made for example a length from a point where the ion flow 703 and the air flow 704 are separated from each other in the region 2 to the pore 104. The point where the ion flow 703 and the air flow 704 are separated from each other in the region 2 can be decided for example by a person with an ordinary skill in the art by an experiment and the like.
As another example, the length in the X-axis direction of the current plate 113 can be made such length that the current plate 113 does not cover the region 2 but covers only the region 3. Also, the entirety of the current plate 113 does not have to be of a flat surface shape, and a part or the entirety of the current plate 113 may be curved.
Also, in an example of
Although the length in the Y-axis direction of the current plate 113 can be designed appropriately by a person with an ordinary skill in the art, it is the same or generally the same as the diameter of the quadrupole of the second electrode set 202 in the example of
In order to prevent electric discharge from each electrode of the ion guide 103, it is preferable that the current plate 113 is configured of an insulating material. For example, a resin material such as PEEK and a ceramic material such as alumina can be used.
At least a part of the current plate 113 is disposed between the center axis of the first electrode set 201 and the center axis of the second electrode set 202 in the Z-coordinate (so as to become parallel to each center axis for example). Thus, the ion flow 703 and the air flow 704 can be separated from each other efficiently.
In the current plate 113, a plane having the largest area may be disposed to become parallel to the X-Y plane. The position of the current plate 113 in the Z-axis direction is preferable to be close to the second electrode set 202 in terms that the separation efficiency of the ion flow 703 and the air flow 704 becomes higher, and the current plate 113 may be configured to be in contact with the second electrode set 202 as shown in
In the X-axis direction, the current plate 113 can be disposed at various positions according to the length of the current plate 113. For example, in the example of
In the Y-axis direction, the current plate 113 is disposed to become symmetric with respect to a position Y1 in the Y-axis direction in an example of
The current plate 113 reduces mixing of the air flow 704 and the ion flow 703 having been separated. For example, when the current plate 113 is disposed as
Further, when the exhaust port 111 is disposed to be on the first electrode set 201 side with respect to the second electrode set 202 in a position in the Z-axis direction, the air flow 704 can be removed more efficiently, and an effect secured becomes large. However, the position of the exhaust port 111 is not required to be disposed strictly, and therefore can be designed freely.
As described above, according to the present example, the configuration of each rod and the current plate 113 is comparatively simple, therefore manufacturing for example is easy, however, modifications as respective examples described below are also possible.
In the present example, an example of the current plate 113 with an aspect different from Example 1 will be explained.
The shape and the raw material of the current plate 113 can be made to be similar to those of Example 1. In the example of
The position in the Z-axis direction of the incident side end (namely an end becoming the region 1 side in the X-axis direction) of the current plate 113 is located between the center axis of the first electrode set 201 and the center axis of the second electrode set 202, and the position in the Z-axis direction of the exit side end (namely an end becoming the pore 104 side in the X-axis direction) of the current plate 113 is located on the Z-axis minus side, namely the exhaust port 111 side of the incident side end. Therefore, in the example of
With such inclined layout, the air flow 704 collides on the current plate 113. Since the air flow 704 after collision proceeds toward the exhaust port 111 in
In the present example, an example of the current plate 113 with an aspect different from Example 1 and Example 2 will be explained.
The cross-sectional shape of the current plate 113 can be designed optionally as long as it is a closed figure and is for example a circle (in this case, the current plate 113 is of a cylindrical shape), an ellipse, or a polygon, and at least the diameter of a hollow portion of the tube only has to be larger than the diameter of the second electrode set 202.
This current plate 113 having the tubular shape can be disposed to cover the second electrode set 202 in a region after the ion flow 703 and the air flow 704 have been separated from each other. This current plate 113 having the tubular shape may be in contact with the pore 104, and may be in contact with the second electrode set 202.
Thus, when the current plate 113 having a tubular shape is used, since the region 3 of the second electrode set 202 is protected by 360 degrees in the Y-Z plane, mixing of the turbulent flow generated by the air flow 704 and the ion flow 703 can be reduced further.
In the present example, an example of the current plate 113 with an aspect different from Example 1, Example 2, and Example 3 will be explained.
Although the disposal position is similar to that of the current plate 113 of
In Example 4, it is possible that both ends of the current plate 113 extend to the side of the ion flow 703 instead of the air flow 704 in a cross section (for example a cross section shown in
According to the present example, the degree of mixing of the ion flow 703 and the air flow 704 is lower compared to Example 1 and Example 2, and is higher compared to Example 3. Further, although the degree of mixing becomes higher compared to Example 3, the consumption amount of the raw material for manufacturing the current plate 113 is less. Therefore, a balance of the manufacturing cost of the apparatus and the effect secured can be selected.
In the present example, an example of using the ion guide 103 with an aspect different from Example 1 will be explained.
The present example is different from Example 1 in terms that the cross section of a part of these rod electrodes is a semicircle. The electrode of the semicircle is the two rods 201a and 201d close to the second electrode set 202 with respect to the first electrode set 201, and the two rods 202b and 202c close to the first electrode set 201 with respect to the second electrode set 202. The cross section of the rod other than them has a circular shape.
In the region 2, the rods 201d and 202c are adjacent to each other, and are arranged to configure a cross-sectional view approximating a semicircle. In a similar manner, the rods 201a and 202b are adjacent to each other, and are arranged to configure a cross-sectional view approximating a semicircle. The distance between the rods 201d and 202c can be made within a range of 0.1 mm to 2 mm, or approximately 0.1 mm to 2 mm. The same is applicable also to the distance between the rods 201a and 202b.
With such disposal, a rod set including the rods 201d and 202c can be regarded to be one rod electrode in the region 2. The same is applicable also to a rod set including the rods 201a and 202b.
Therefore, in the region 2, the ion guide 103 is configured of a hexapole by six electrodes in total of the rod 201b, the rod 201c, the rod 202a, the rod 202b, a rod set including the rods 201d and 202c, and a rod set including the rods 201a and 202b.
In the example of
In a similar manner to Example 1, with respect to the number of piece of the rod electrode in the first electrode set 201, the number of piece of the rod electrode in the second electrode set 202, and the number of piece of the rod electrode in an electrode formed by combination of the first electrode set 201 and the second electrode set 202 in the region 2, the number of piece is no object as long as it is a multipole formed of only the rod electrodes of even number of piece.
Although the RF voltage and the DC voltage applied to the electrode are similar to those of Example 1, since each of the rods 201d and 202c is regarded to be one pole in the region 2, the RF voltage with the same phase, the same frequency, and the same amplitude is applied to these rods. However, with respect to the DC voltage, it is not required to be equalized in these rods. The same is applicable also to the rods 201a and 202b.
The principle in separating the ion flow 703 and the air flow 704 from each other by the ion guide 103 is similar to that of Example 1.
In the present example, an example of using the ion guide 103 with an aspect different from Example 1 and Example 5 will be explained.
In the region 2, four pieces in total of the rods 201a, 201h, 202d, and 202e are bent in the Y-axis direction so as to spread generally symmetrically with respect to a position Y1 in the Y-axis direction. The cross-sectional view of the region 2 in the present example has a shape like an ellipse generally having a “constriction”. The rods other than them namely the rods 201b to 201g, 202a to 202c, and 202f to 202h are formed into a linear shape for example.
With respect to all of the number of piece of the rod electrode in the first electrode set 201, the number of piece of the rod electrode in the second electrode set 202, and the number of piece of the rod electrode in a portion where there exists a “constriction” formed by combination of the first electrode set 201 and the second electrode set 202 in the region 2, the number of piece is no object as long as it is a multipole formed of the rod electrodes of even number of piece.
The voltage applied to each rod can be made similar to that of Example 1 or Example 5. However, in the region 2, since there exists a “constriction” described above, the situation of the pseudopotential is different from that of Example 1 and Example 5. An example of the pseudopotential in the present example is shown in
A portion shown by a broken line in
Ions can override this pseudopotential barrier by enlarging the DC potential difference between the first electrode set 201 and the second electrode set 202. Due to presence of the pseudopotential barrier, the ion flow 703 is converged into the second electrode set 202 more strongly after moving to the second electrode set 202, and therefore efficiency of permeation of the ion flow 703 through the pore 104 becomes high.
In the present example, an example of using the ion guide 103 with an aspect different from Example 1, Example 5, and Example 6 will be explained.
An RF voltage of an opposite phase is applied to electrodes adjacent to each other in the X-axis direction, and an RF voltage of the same phase is applied to rings of the same position in the X-axis direction. The off set DC voltage is similar to that of Examples described above.
The diameter of the ring electrode of the first electrode set 201 and the diameter of the ring electrode of the second electrode set 202 may be same with and different from each other. However, when the diameter of the second electrode set 202 is made smaller than the diameter of the ring electrode of the first electrode set 201, the ion flow 703 is converged more strongly in the region 3, and the efficiency of permeation through the pore 104 becomes high which is preferable.
The shape of the ion guide 103 in the region 2 may be a shape where there exists a constriction between the first electrode set 201 and the second electrode set 202 and a barrier of the pseudopotential is formed as
In the present example, an example of using the ion guide 103 with an aspect different from Example 1, Example 5, Example 6, and Example 7 will be explained.
Also, not only the region 3 but also the region 1 can be omitted further. With such modification, the ion guide 103 can be shortened further compared to the configuration of
By combination of the ion guide 103 of
In the present example, an example of using the ion guide 103 with an aspect different from Example 1, Example 5, Example 6, Example 7, and Example 8 will be explained.
Respective segments are electrically insulated from each other. Respective segments may be insulated by leaving a gap, and may be insulated by filling the gaps between respective segments with an insulating material and connecting the segments with reach other.
Within the same electrode set, the frequency, the amplitude, and the phase of the RF voltage to be applied between the segments are same, but the offset DC voltage to be applied is changed. The offset DC voltage is applied to each rod so as to monotonically change in the X-axis direction and to monotonically change in the Z-axis direction also for example.
For example, by changing the gradient of the DC potential according to the position in the X-axis direction, the DC potential being generated between the first electrode set 201 and the second electrode set 202 in the region 2, the ion flow 703 and the air flow 704 can be separated from each other more efficiently.
Also, in the second electrode set 202, by arranging the DC potential gradient where the DC potential of the segment 1 is made high and the DC potential of the segment 3 is made low, the ion flow 703 can be transferred to the pore 104 more efficiently.
The present invention is not limited to examples described above, and various modifications are included. For example, examples described above were explained in detail for easy understanding of the present invention, and is not to be necessarily limited to one including all configurations having been explained. Also, a part of a configuration of an example can be substituted by a configuration of other examples, and a configuration of an example can be added with a configuration of other examples. Further, with respect to a part of the configuration of each example, it is possible to add other configurations, to be deleted, and to be substituted.
Also, each configuration, function, processing unit, processing means, and the like described above may be achieved by hardware by designing a part or all thereof by an integrated circuit for example. Also, each configuration, function, and the like described above may be achieved by software by that a processor interprets and executes a program achieving each function. Information of a program, a table, a file, and the like achieving each function can be placed in a recording device such as a memory, a hard disk, and an SSD (Solid State Drive) or a recording medium such as an IC card, an SD card, and a DVD.
Also, with respect to a control line and an information line, those considered to be required for explanation are shown, and all control lines and information lines of a product have not necessarily been shown. It is possible to consider that almost all configurations are actually connected with each other.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-038168 | Mar 2020 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/005079 | 2/10/2021 | WO |
