JP7028109B2 - Mass spectrometer - Google Patents

Description

The present invention relates to a mass spectrometer.

A mass spectrometer using a multipole rod electrode (multipole ion guide) in which a plurality of rod electrodes are arranged surrounding a central axis is widely used. For example, in the case of a linear ion trap using a quadrupole rod, there are four X-rod electrode pairs arranged in the ± X direction and a Y-rod electrode pair arranged in the ± Y direction with the central axis as the origin. It is equipped with a rod electrode. Then, in order to trap the ions, RF voltages for trapping having different phases of 180 degrees are applied to the X-rod electrode pair and the Y-rod electrode pair.

In the linear ion trap, not only the ion trap but also the ion of m / z (mass-to-charge ratio) in a specific range is left in the ion trap, and the other m / z ions are excluded from the ion trap. There is also a ration. In addition, by applying kinetic energy only to ions in a specific range of m / z, they collide with other molecules and are fragmented.
In order to isolate or fragment m / z ions in a specific range, an AC voltage for ion excitation is further applied to one of the X-rod electrode pair and the Y-rod electrode pair.

As described above, in the linear ion trap, it is necessary to superimpose two kinds of voltages on the electrodes. Such a power source is disclosed in, for example, Figure 2 of Non-Patent Document 1. In the linear ion trap disclosed in Non-Patent Document 1, the RF voltage for the trap is directly applied to the X rod electrode pair from the RF power supply (MAIN RF DRIVE). On the other hand, the RF voltage for the trap is applied to the Y rod electrode pair from the RF power supply via the secondary side of the transformer on which the AC voltage is superimposed. An AUX DRIVE is connected to the primary side of the transformer, and the AC voltage generated by the AUX DRIVE is superimposed on the RF voltage for the trap by the transformer and input to the Y rod electrode pair.

J.M.Campbell et al., "A New Linear Ion Trap Tome-of-flight System with Tandem Mass Spectrometry Capabilities", Rapid Commun. Mass Spectrom., Vol.12, pp.1463-1474 (1998)

In the linear ion trap disclosed in Non-Patent Document 1, an RF voltage and an AC voltage are superimposed using a transformer. Since the transformer has a capacitance, the capacitance between the Y-rod electrode pair and the ground to which the RF voltage is supplied through the transformer is the X-rod electrode pair and the ground to which the RF voltage is directly supplied from the RF power supply. Compared to the capacitance between. This difference in capacitance causes a difference in the potential (absolute value of the potential) between the X-rod electrode pair and the Y-rod electrode pair when an AC voltage is applied.

If the absolute values of the potentials applied to the X-rod electrode pair and the Y-rod electrode pair are equal, no electric field is generated on the central axis of the linear ion trap. However, if there is a difference in the potential (absolute value of the potential) between the X-rod electrode pair and the Y-rod electrode pair due to the above-mentioned difference in capacitance, it fluctuates on the central axis according to the change in the AC voltage. An AC electric field is generated. Then, this AC electric field forms a so-called pseudo-potential that is proportional to the square of the electric field.
Since this pseudo-potential acts as a barrier to ions incident on the linear ion trap from the outside, it becomes difficult for the ions to be introduced into the linear ion trap, which causes a decrease in the detection sensitivity of the mass spectrometer.

The mass analyzer according to the preferred embodiment of the present invention is connected to a multi-pole ion guide including a first electrode pair and a second electrode pair arranged symmetrically with respect to the central axis, and the first electrode pair. , A first transmission unit that transmits the RF voltage applied to the first electrode pair, and a second transmission unit that is connected to the second electrode pair and transmits the RF voltage applied to the second electrode pair. The first transmission unit includes a capacitor that reduces the difference between the capacitance of the first transmission unit and the capacitance of the second transmission unit.
In a more preferred embodiment, the capacitor is a variable capacitor.
In a more preferred embodiment, the second transmission unit has a voltage superimposition circuit that superimposes an AC voltage on the RF voltage, and the capacitance of the capacitor of the first transmission unit is the voltage superimposition circuit. Approximately equal to capacitance.
In a more preferred embodiment, the voltage superimposing circuit is an isolation transformer.
In a more preferred embodiment, it has a variable capacitor that adjusts the capacitance between the first transmission and the second transmission.
In a more preferred embodiment, the multipole ion guide constitutes a linear ion trap.
In a more preferred embodiment, the multipole ion guide constitutes a multipole mass filter.
In a further preferred embodiment, another mass spectrometer is provided after the multipole ion guide.

According to the present invention, the efficiency of ion incident on a linear ion trap (multipolar ion guide) is improved, thereby improving the detection sensitivity of the mass spectrometer.

1A and 1B are views showing the mass spectrometer of the first embodiment, FIG. 1A shows the whole configuration thereof, and FIG. 1B shows the rod electrode and the details of the power supply for supplying voltage to the rod electrode. .. FIG. 2 is a diagram showing a modified example of a power supply circuit that supplies voltage to a rod electrode. FIG. 3 is a diagram showing a mass spectrometer of the second embodiment.

(First Embodiment of Mass Spectrometer)
1A and 1B are views showing the configuration of the mass spectrometer 100 according to the first embodiment of the present invention, FIG. 1A shows the overall configuration thereof, and FIG. 1B shows the multipole rod electrode 6 and the multipole rod. It is a figure which shows the detail of the power source 10 which supplies a voltage to an electrode 6. In the mass spectrometer 100, an ionization chamber 2, an ion optical system 3, an ion optical system 4, a multi-pole rod electrode (multi-pole ion guide) 6, and an ion detector 8 are located inside the vacuum vessel 1 along the central axis AX. It is provided. The inside of the substantially sealed vacuum container 1 is exhausted by the vacuum pumps 9a, 9b, 9c.
The direction of the Z axis shown in FIG. 1A is a direction that coincides with the direction of the central axis AX of the multipole rod electrode 6.

The ionization chamber 2 is a device for ionizing a gas sample or a liquid sample supplied from the outside. The ionization chamber 2 ionizes the sample by, for example, electron ionization, chemical ionization, atmospheric pressure chemical ionization, and electrospray ionization.
The ions generated in the ionization chamber 2 are drawn out from the ionization chamber 2 and introduced into the ion optical system 4 through the ion optical system 3. The ion optical system 4 surrounds the central axis AX and is provided with, for example, four rod electrodes at positions separated by predetermined distances in the ± X direction and the ± Y direction in FIG. 1, respectively. A high frequency voltage is applied to the ion optical system 4 from a power supply circuit (not shown).

The ions that have passed through the ion optical system 4 pass through the incident side end electrode 5 in which the ion transmission hole is formed in the vicinity of the central axis AX, and are introduced into the multi-pole rod electrode (multi-pole ion guide) 6. To. Similar to the ion optical system 4, the multi-pole rod electrode 6 also surrounds the central axis AX, and for example, the four rod electrodes 6a are located at positions separated by predetermined distances in the ± X direction and the ± Y direction in FIG. It is equipped with ~ 6d.
Hereinafter, in the first embodiment, the multipole rod electrode (multipole ion guide) 6 will be described as an example of a linear ion trap 6.

In the vicinity of the injection side (right side in the figure) of the linear ion trap 6, an injection side end electrode 7 having an ion transmission hole formed in the vicinity of the central axis AX is provided. A predetermined voltage is applied to the incident side end electrode 5 and the emission side end electrode 7 from a power source (not shown). Further, a predetermined voltage is applied from the power supply circuit 10 to the rod electrodes 6a to 6d constituting the linear ion trap 6.

By setting the potentials of the rod electrodes 6a to 6d lower than the potentials of the incident side end electrodes 5 and the ejection side end electrodes 7 and applying a predetermined RF voltage to the rod electrodes 6a to 6d, the linear ion trap 6 is provided. The incident ions can be confined in the linear ion trap 6. Further, by lowering the potential of the injection side end electrode 7 to be lower than the potential of the rod electrodes 6a to 6d at a predetermined time, the ions trapped in the linear ion trap 6 are transferred to the ion transmission hole of the injection side end electrode 7. It can be transferred to the ion detector 8 through.

FIG. 1B is a diagram showing details of a power supply circuit 10 that supplies a voltage to the four rod electrodes 6a to 6d constituting the linear ion trap 6. In the following, of the four rod electrodes 6a to 6d, the pair of the rod electrode 6c arranged on the + X side and the rod electrode 6d arranged on the −X side with respect to the central axis AX is the X rod electrode pair (6c). , 6d). Further, the pair of the rod electrode 6a arranged on the + Y side and the rod electrode 6b arranged on the −Y side with respect to the central axis AX is called a Y rod electrode pair (6a, 6b).

In the present specification, the RF voltage means an AC voltage having a frequency f of about 0.3 to 10 MHz.
Generally, in the linear ion trap 6, an RF voltage having the same absolute value and a reverse sign is applied to the X rod electrode pair (6c, 6d) and the Y rod electrode pair (6a, 6b). If the maximum value of the RF voltage is Q, the RF voltage can be expressed as Qcosωt. Here, ω is an angular frequency (ω = 2πf).

As an example, an RF voltage Qcosωt is applied to the X rod electrode pair (6c, 6d), and an RF voltage −Qcosωt is applied to the Y rod electrode pair (6a, 6b). As a result, ions of m / z (mass-to-charge ratio) in a predetermined range can be confined in the linear ion trap 6 without being dispersed in the XY directions.
Further, in order to isolate or fragment a specific range of m / z ions, one of the X-rod electrode pair (6c, 6d) or the Y-rod electrode pair (6a, 6b) is added to the above RF voltage. Then, the AC voltage for ion isolation is superimposed and applied. The frequency of the AC voltage for ion excitation is, for example, less than half the frequency of the RF voltage described above.
Therefore, the power supply circuit 10 is configured to apply the above-mentioned voltage to the four rod electrodes 6a to 6d.

The RF power supply circuit 11 has a resonance circuit transformer 12, and an AC voltage having a predetermined frequency f is input from the RF power supply 16 to the primary side coil 13 of the resonance circuit transformer 12. The resonance circuit transformer 12 is provided with the secondary side coil 14a and the secondary side coil 14b side by side. The RF voltage is derived from the RF power supply 16 by an LC resonant circuit formed by the inductance of the secondary coil 14a and the secondary coil 14b and the capacitance connected to the high voltage ends 14ae and 14be of the secondary coil. It is generated by amplifying the voltage of the input frequency f. Here, the above-mentioned capacitance refers to the capacitance of the X-rod electrode pair (6c, 6d) and the Y-rod electrode pair (6a, 6b), various capacitances appearing in the conductors 22a to 22c, 23a to 23c, and a capacitor. 24, the capacitance of the isolation transformer 18.

As a result, RF voltages having a phase difference of 180 degrees are generated at the high voltage ends 14ae and 14be of the secondary coil. The RF voltage generated at the high voltage end 14be is applied to the X rod electrode pair (6c, 6d), and the RF voltage generated at the high voltage end 14ae is applied to the Y rod electrode pair (6a, 6b).
Further, a DC voltage P is applied to one end of the secondary coil 14a and 14b from the DC power supply 15 with reference to the ground, and is applied to the X rod electrode pair (6c, 6d) and the Y rod electrode pair (6a, 6b). In addition to the RF voltage, a voltage on which a DC voltage P is superimposed is applied. In the following embodiments, a case where the DC voltage P is 0 V (GND potential) will be described for ease of understanding.

The high voltage side end 14be of the secondary side coil 14b is connected to the intermediate point 20c of the secondary side coil 20a and the secondary side coil 20b of the isolation transformer 18 constituting the voltage superimposition circuit 17 via the lead wire 23a. .. An AC voltage having a frequency of half or less of the RF voltage and a voltage fluctuating around the ground potential of an angular frequency ρ is applied to the primary side coil 19 of the isolation transformer 18 from the AC power supply 21. Therefore, only the RF voltage generated at the high voltage end 14ae is applied to the Y rod electrode pair (6a, 6b), while the rod electrode 6d and the rod electrode 6c constituting the X rod electrode pair (6c, 6d) are applied. In addition to the RF voltage generated at the high voltage end 14be, a voltage on which an AC voltage having a phase difference of 180 ° is superimposed is applied.

Here, the path between the high voltage end 14be of the secondary side coil 14b and the X rod electrode pair (6c, 6d), that is, the conductor 23a, the voltage superimposing circuit 17, and the conductors 23b, 23c are referred to as an X side transmission unit. If the path between the high voltage end 14ae of the secondary side coil 14a and the Y rod electrode pair (6a, 6b), that is, the conducting wires 22a to 22c is called the Y side transmitting portion, the capacitor 24 connected to the conducting wire 22 In the absence of, since the capacitance derived from the insulating transformer 18 exists in the X-side transmission section, the capacitance of the X-side transmission section becomes larger than the capacitance of the Y-side transmission section.

Therefore, in the mass spectrometer 100 of the first embodiment, at least one of the Y-side transmission portions (conductors 22a to 22c) connecting the high-voltage end 14ae of the secondary-side coil 14a and the Y-rod electrode pair (6a, 6b). A capacitor 24 that forms a capacitance with the ground is added to the portion. The capacitor 24 reduces the difference between the capacitance between the Y-side transmission section (conductors 22a to 22c) and the ground and the capacitance between the X-side transmission section (voltage superimposition circuit 17, conductors 23a to 23c) and the ground. Will be done.
This makes it possible to reduce the magnitude of the AC electric field generated on the central axis AX when the RF voltage is applied. That is, the value of the pseudo potential can be reduced, and the efficiency of introducing ions into the linear ion trap 6 can be improved.

Here, the capacitance Cy of the Y rod electrode pair (6a, 6b) and the Y side transmission unit (conductor wires 22a to 22c), and the X rod electrode pair (6c, 6d) and the X side transmission unit (voltage superimposition circuit 17, The problem that occurs when the capacitance Cx of the conductors 23a to 23c) is different will be described.
As described above, RF voltages having a phase difference of 180 ° are generated at the high voltage ends 14ae and 14be of the secondary coil. Here, let V be the potential difference between the two RF voltages.

The X-side transmission section and the Y-side transmission section are arranged in series with the X-rod electrode pair (6c, 6d) and the Y-rod electrode pair (6a, 6b) interposed therebetween. Therefore, the sum of the impedances of both acts as a load of the RF power supply circuit 11. Therefore, the current I determined by the equation (1) flows from the RF power supply circuit 11.
V = I ・ (1 / jωCx + 1 / jωCy) ・ ・ ・ (1)
Here, j is an imaginary unit, 1 / jωCx is the impedance due to the capacitance Cx, and 1 / jωCy is the impedance due to the capacitance Cy.

The potential difference Vx applied to the X rod electrode pair (6c, 6d) having the capacitance Cx and the X side transmission unit (voltage superimposition circuit 17, conductors 23a to 23c) is
Vx = I · (1 / jωCx) = V · Cy / (Cx + Cy) ... (2)
Will be.
On the other hand, the potential difference Vy applied to the Y rod electrode pair (6a, 6b) having the capacitance Cy and the Y side transmission portion (conductor wires 22a to 22c) is.
Vy = I · (1 / jωCy) = V · Cx / (Cx + Cy) ... (3)
Will be.

Therefore, when the capacitance Cx and the capacitance Cy are different, the potential difference Vx and the potential difference Vy are not equal. In this case, even if the RF power supply circuit 11 generates a symmetrical potential of -1 / 2V in the output unit 14ae and 1 / 2V in the output unit 14be, the X rod electrode pair (6c, 6d) and the Y rod electrode pair (6a). , 6b) will not be symmetrical. Since the potential difference V is an RF voltage as described above, the potential difference Vx and the potential difference Vy are also RF voltages, that is, they vibrate at a high frequency with time.
As a result, an electric field that vibrates at a high frequency in accordance with the vibration of the potential difference Vx and the potential difference Vy is generated on the central axis AX located at the center of the rod electrodes 6a to 6d. Then, this high-frequency electric field forms a pseudo-potential proportional to the square of the electric field, and forms a barrier against ions entering the linear ion trap 6 from the outside.

In the first embodiment, as described above, the capacitor 24 is added to at least a part of the Y-side transmission unit (conductor wires 22a to 22c). As a result, the capacitance Cy of the Y-rod electrode pair (6a, 6b) and the Y-side transmission section (conductors 22a to 22c), and the X-rod electrode pair (6c, 6d) and the X-side transmission section (voltage superimposition circuit 17, The difference between the conductor wires 23a to 23c) and the capacitance Cx is reduced.
As a result, the size of the AC electric field formed on the central axis AX can be reduced, and the efficiency of introducing ions into the linear ion trap (multipole ion guide) 6 can be improved.

As the capacitor 24 added to the Y-side transmission unit (conductor wires 22a to 22c), for example, a capacitor having excellent withstand voltage resistance and high frequency characteristics such as a ceramic capacitor can be used. Further, as shown in FIG. 1 (b), a variable capacitor having a variable capacitance may be used. In that case, even if the capacitance of the transmission unit (lead wire 22a to 2c, voltage superimposition circuit 17, and lead wire 23a to 23c) changes due to changes in temperature and humidity or changes over time, the change is compensated for and static electricity. There is a merit that the electric capacity can be adjusted.
The capacitor 24 is not limited to a capacitor as a so-called electronic component. For example, a plate-shaped electrode is connected to a part of the Y-side transmission portion (conductor wires 22a to 22c), and the plate-shaped electrode is arranged so as to face the outer wall or inner wall of the vacuum vessel 1 maintained at the ground potential. It may be configured to generate a capacitance.

(Modification example of power supply circuit)
FIG. 2 is a diagram showing a modified example of the power supply circuit 10a that supplies an RF voltage to the multipole rod electrode 9.
Since the configuration of the power supply circuit 10a of the modified example is almost the same as the configuration of the power supply circuit 10 in the above-described first embodiment, the same parts are designated by the same reference numerals and the description thereof will be omitted.

In the power supply circuit 10a of the modified example, in addition to the power supply circuit 10 described above, the resonance circuit transformer 12 is located between the conductors 22a to 22c constituting the Y-side transmission unit and the conductor wires 23a to 23c constituting the X-side transmission unit. A variable capacitor 25 for adjusting the resonance condition of the above is provided.
In the power supply circuit 10a of this modification, the resonance conditions of the RF power supply circuit 11 and the conductors 22a to 22c, 23a to 23c, etc. are changed by changing the capacitance of the variable capacitor 25, and the RF power supply circuit 11 is predetermined. RF of frequency f in the range of can be generated.

In the above first embodiment and the modified example, the multipole rod electrode 6 is a quadrupole having four rod electrodes, but the number of the multipole rod electrodes 6 is limited to four. Instead, it may be eight. In that case, the power supply circuits 10 and 10a are also configured to supply a large number of predetermined voltages according to the number of the multipole rod electrodes 6.
In the above first embodiment and the modified example, one transmission unit applies a voltage from the RF power supply 11 to two rod electrodes (X rod electrode pair (6c, 6d), Y rod electrode pair 6a, 6b), respectively. Although it is assumed that the rod electrodes are supplied, the number of rod electrodes to which one transmission unit supplies voltage is not limited to two, and may be any number. For example, in the case of an octupole rod electrode composed of eight rod electrodes, voltage may be supplied to the four rod electrodes from one transmission unit.

In the above first embodiment and modification, the voltage superimposition circuit 17 is composed of an isolation transformer 18, but the voltage superimposition circuit 17 is a circuit capable of superimposing an AC voltage on an RF voltage. Other circuits may be used. For example, a circuit using a power semiconductor element can also be used.

In the above first embodiment and the modified example, the multipole rod electrode (multipole ion guide) 6 constitutes a linear ion trap, but the present invention is not limited to this, and a multipole mass filter may be configured. good. In this case, the incident side end electrode 5 and the ejection side end electrode 7 are not essential and can be appropriately removed.

(Effects of First Embodiment and Modifications)
(1) In the mass analyzers of the first embodiment and the modifications described above, the first electrode pair (Y rod electrode pair 6a, 6b) arranged symmetrically with respect to the central axis AX, and the second electrode pair A multi-pole ion guide (linear ion trap 6) including (X-rod electrode pairs 6c, 6d) and an RF voltage connected to the first electrode pairs 6a, 6b and applied to the first electrode pairs 6a, 6b. A second transmission unit (lead wires 22a to 22c) to be transmitted and a second transmission unit (leading wires 22a to 22c) connected to the second electrode pairs 6c and 6d to transmit the RF voltage applied to the second electrode pairs 6c and 6d. The voltage superimposing circuit 17 and the conducting wires 23a to 23c) are provided, and the first transmitting portion (leading wires 22a to 22c) includes the capacitance of the first transmitting portion (leading wires 22a to 22c) and the second transmission portion (leading wires 22a to 22c). It has a capacitor 24 that reduces the difference between the voltage superimposition circuit 17 and the electrostatic capacity of the conducting wires 23a to 23c).
With this configuration, it is possible to reduce the magnitude of the AC electric field generated on the central axis AX of the multipole ion guide 6 when the RF voltage is applied, and it is possible to reduce the value of the pseudo potential. As a result, the efficiency of introducing ions into the multipole ion guide (linear ion trap) 6 can be improved, and the detection sensitivity of the mass spectrometer is improved.
(2) By using the capacitor 24 as a variable capacitor, even when the capacitance of the transmission unit (conductor wires 22a to 2c, voltage superimposition circuit 17, conductor wires 23a to 23c) changes due to changes in temperature and humidity or changes over time. , The change can be compensated and the capacitance can be adjusted.
(3) The other transmission unit (voltage superimposition circuit 17, lead wires 23a to 23c) has a voltage superimposition circuit 17 that superimposes an AC voltage on the RF voltage, and the capacitor of the first transmission unit (lead wires 22a to 22c). By making the capacitance of 24 substantially equal to the capacitance of the voltage superimposition circuit 17, the capacitance added by the voltage superimposition circuit 17 can be easily compensated by the capacitor 24.
(4) By using the voltage superimposition circuit 17 as an isolation transformer 18, it is possible to efficiently superimpose the AC voltage on the RF voltage.
(5) The RF power supply circuit 11 and the conducting wire 22a are provided with the variable capacitor 25 for adjusting the capacitance between the first transmitting portion (conductor wires 22a to 22c) and the second transmitting portion (conductor wires 23a to 23c). The resonance conditions of the circuit including ~ 22c and 23a to 23c can be changed, and the RF voltage having a frequency f in a predetermined range can be supplied to the multipolar ion guide 6.
(6) By using the multi-pole ion guide 6 as an electrode constituting the linear ion trap, a mass spectrometer with improved ion introduction efficiency into the linear ion trap can be realized.
(7) By using the multipole ion guide 6 as an electrode constituting the quadrupole mass filter, a mass spectrometer with improved ion introduction efficiency into the quadrupole mass filter can be realized.

(Second Embodiment of Mass Spectrometer)
FIG. 3 is a diagram showing the configuration of the mass spectrometer 100a according to the second embodiment of the present invention. Since most of the configurations of the mass spectrometer 100a of the second embodiment are common to the configurations of the mass spectrometer 100 of the first embodiment described above, the same parts are designated by the same reference numerals and the description thereof will be omitted. ..

The mass spectrometer 100a of the second embodiment has another mass spectrometer 30 after the multi-pole rod electrode 6 of the mass spectrometer 100 of the first embodiment described above. Specifically, another mass spectrometric unit 30 is a time-of-flight mass spectrometric unit 30 having a flight tube 27 and an orthogonal acceleration electrode 28, and the ions ejected from the multipole rod electrode 6 are sent to the ion optical system 26. It is guided and incident on the orthogonal acceleration electrode 28. Then, it is accelerated by the orthogonal acceleration electrode 28 and flies in the flight space FA in the flight tube 27 along the flight path FP. During flight in the flight space FA, ions are reflected by the reflector 29 and detected by the ion detector 8.

Since the velocity of the ions flying in the flight path FP has a correlation with the m / z of the ions, the amount corresponding to the m / z of the ions can be measured by measuring the flight time of the ions. As a result, the time-of-flight mass spectrometry unit 30 can perform mass spectrometry.
Also in the second embodiment, by using the multi-pole ion guide (multi-pole rod electrode) 6 as the linear ion trap 6, a large number of ions accumulated in the linear ion trap 6 are analyzed by the time-of-flight mass spectrometer 30. By doing so, mass spectrometry with good S / N can be performed. Further, the ion fragmented in the linear ion trap 6 can be analyzed by the time-of-flight mass spectrometer 30.

Alternatively, a multipole ion guide (multipole rod electrode) 6 may be used as a multipole mass filter, and a collision cell (not shown) may be arranged between the multipole mass filter and the time-of-flight mass spectrometer 30. In this case, the precursor ion selected by the multi-pole mass filter composed of the multi-pole rod electrode 6 is cleaved in the collision cell, and various product ions generated by the cleaving are high in the time-of-flight mass spectrometer 30. Mass spectrometry can be performed accurately.
The other mass spectrometric unit 30 is not limited to the time-of-flight mass spectrometric unit 30 described above, and may be another quadrupole mass spectrometric unit 30.

(Effect of the second embodiment)
(8) The mass spectrometer of the second embodiment is, in addition to the mass spectrometer of the first embodiment and the modified example described above, further after the multi-pole ion guide (multi-pole rod electrode) 6. It has a mass spectrometer.
With this configuration, the incident efficiency to the ion trap portion (multipolar ion guide 6) of the ion trap type flight time type mass apparatus can be increased, and the detection sensitivity of the mass spectrometer is improved.
Alternatively, the efficiency of incident on the multipole mass filter (multipole ion guide 6) in the previous stage of the so-called tandem mass spectrometer can be increased, and the detection sensitivity of the mass spectrometer is improved.

Although various embodiments and modifications have been described above, the present invention is not limited to these contents. Moreover, each embodiment may be applied individually or may be used in combination. Other aspects considered within the scope of the technical idea of the present invention are also included within the scope of the present invention.

100, 100a ... Mass spectrometer, 1 ... Vacuum vessel, 2 ... Ionization chamber, 3, 4, 26 ... Ion optical system, 6 ... Linear ion trap (multi-pole ion guide), 6a-6d ... Rod electrode, 5 ... Incident Side end electrode, 7 ... Injection side end electrode, 8 ... Ion detector, 9a-9d ... Vacuum pump, 10 ... Power supply circuit, 11 ... RF power supply circuit, 12 ... Resonance circuit transformer, 15 ... DC power supply, 16 ... RF power supply, 17 ... Voltage superimposition circuit (X side transmission unit), 18 ... Insulated transformer, 21 ... AC power supply, 22a to 22c ... Conduction wire (Y side transmission unit), 23a to 23c ... Conduction wire (X side transmission unit), 24 ... Capacitor, 25 ... Variable condenser, 27 ... Flight tube, 28 ... Orthogonal accelerator, 29 ... Reflector, 30 ... Flight time type mass spectrometer (another mass spectrometer), FA ... Flight space, FP ... Flight path

Claims (8)

A multipole ion guide containing a first pair of electrodes and a second pair of electrodes arranged symmetrically with respect to the central axis.
A first transmission unit connected to the first electrode pair and transmitting an RF voltage applied to the first electrode pair,
It is connected to the second electrode pair and is applied to the second electrode pair to transmit a superposed voltage obtained by superimposing an AC voltage on an RF voltage, and has a voltage superimposing circuit that generates the superposed voltage. With a second transmission
The first transmission unit is a mass spectrometer having a capacitor that reduces the difference between the capacitance of the first transmission unit and the capacitance of the second transmission unit. In the mass spectrometer according to claim 1,
The capacitor is a variable capacitor, a mass spectrometer. In the mass spectrometer according to claim 1 or 2.
A mass spectrometer in which the capacitance of the capacitor included in the first transmission unit is substantially equal to the capacitance of the voltage superimposition circuit. In the mass spectrometer according to any one of claims 1 to 3.
The voltage superimposition circuit is an isolation transformer, a mass spectrometer. In the mass spectrometer according to any one of claims 1 to 4.
Further, a mass spectrometer having a variable capacitor for adjusting the capacitance between the first transmission unit and the second transmission unit. In the mass spectrometer according to any one of claims 1 to 5.
The multipole ion guide is a mass spectrometer that constitutes a linear ion trap. In the mass spectrometer according to any one of claims 1 to 5.
The multipole ion guide is a mass spectrometer that constitutes a multipole mass filter. The mass spectrometer according to any one of claims 1 to 6.
A mass spectrometer having another mass spectrometer after the multipole ion guide.

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