JP3405919B2 - Atmospheric pressure ionization mass spectrometer - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an atmospheric pressure ionization mass spectrometer.

[0002]

2. Description of the Related Art Many chemical substances diffuse into the environment and are likely to have many direct and indirect effects on the ecosystem and human body. Knowing how and how much these chemical substances exist in nature has become a major theme in analytical chemistry and environmental science. In addition, to know the behavior of chemical substances in the living body is an important theme such as medicine and pharmacy.
Chemical substances existing in the natural world and the human body generally do not exist purely, but exist in very small amounts in many chemical substances. For the analysis of these chemical substances, it is required that the analysis device and the analysis method have high sensitivity. In addition, high selectivity for selectively detecting a specific component to be analyzed from the interfering substances is also required. A liquid chromatograph directly coupled mass spectrometer (LC / MS), which is a combination of a liquid chromatograph (LC) and a mass spectrometer (MS), has been developed to detect a trace amount of a target substance in a mixture with high sensitivity. . LC is an extremely excellent device as a means for separating a specific compound from a mixture in a solution state.
However, this device and method have very poor ability (qualitative and identification ability) to determine what the compound is.
On the other hand, MS has extremely high qualitative and identification ability for a pure compound, but is ineffective for a mixture. Therefore, LC / MS, which uses MS as a detector for LC, was developed as an effective means of analyzing mixtures.

FIG. 14 shows a known LC / MS configuration. The sample solution separated into each component by the liquid chromatograph 1 is guided to the atmospheric pressure ion source 3 through the connecting tube 2. The ion source 3 is controlled by an ion source power source 4 through a signal line 5a. The ion source 3 produces ions derived from sample molecules. Subsequently, the generated ions are transferred to the mass spectrometric section 6
And mass spectrometric analysis. The mass spectrometer 6 is a vacuum system 7
Is evacuated by. The mass-analyzed ions are detected by the detector 8. The detected signal is sent to the data processor 9 via the signal line 5b and gives analysis data such as a mass spectrum and a chromatogram.

As described above, the principle of LC / MS is extremely simple, but in reality, it has many problems. LC
Is a device that handles large amounts of water and organic solvents (such as methanol) under atmospheric pressure (1 ml to 2 ml per minute), whereas MS is a device that handles ions under high vacuum. Therefore, it has been difficult for many years to directly connect the two. Many researchers and manufacturers have made attempts to overcome many problems and develop a high-performance LC / MS, and various methods for overcoming many problems have been proposed. Among them, the method currently widely used is a spray ionization method in which a solution is sprayed at atmospheric pressure and ionized.

As an example, Analytical Chemistry, 5
9, 2642 (1987), there is an electrospray ionization method. FIG. 15 is a schematic diagram of a known LC / MS equipped with an electrospray ion source. The sample solution eluted from the liquid chromatograph 1 is introduced into the spraying capillary 11 having an inner diameter of about 0.1 mm through the connecting tube 2 and the connector 10. A high DC voltage of several kV is applied between the capillary 11 and the counter electrode 12. As a result of the high electric field generated as a result, fine droplets having a charge are ejected into the atmosphere from the tip of the spray capillary in a cone shape. That is, the electrospray phenomenon occurs. In this electrospray method, it is often performed that nitrogen gas or the like is ejected as the atomization auxiliary gas 25 from the gas ejection port 13 along a pipe coaxial with the atomization capillary. This promotes spraying, atomization of droplets, and drying of charged droplets. While countering the flow of the counter gas 35 ejected from the counter gas ejection port 14 provided at the center of the counter electrode 12, the ions and charged droplets proceed along the high electric field, during which further drying of droplets is promoted,
Ions are released into the atmosphere. The ions thus generated are introduced into the vacuum through the sampling pores 15, enter the high-vacuum mass analysis region 6, and are subjected to mass analysis.

In addition to LC / MS, a plasma mass spectrometer is an apparatus for introducing ions generated under atmospheric pressure into a high vacuum mass spectrometer to perform mass spectrometry. Ions generated in plasma generated by high frequency or microwave under atmospheric pressure are taken into a mass analysis region through a multistage differential evacuation system for mass analysis.

[0007]

When the ions are taken into the vacuum from the atmospheric pressure, not only the ions pass through the ion sampling pores 15, but also neutral gas molecules, neutral droplets, and charged droplets. And so on. That is, in the gas that passes through the ion sampling pores 15, there are many fine droplets that cannot be vaporized by the spray auxiliary gas 25, the counter gas 35, and the like. These are taken into the vacuum from the ion sampling pores 15 together with the ions. Regardless of the presence or absence of electric charges, the liquid droplets collide with the accelerated ions in a vacuum to cause the disappearance of the ions (electric charges), the scattering of the ions, and the like, which causes disturbance of the detection signal, that is, noise. Also, the mass of a drop does not give the correct mass in a mass spectrometer because the mass of the drop constantly changes as it evaporates in a vacuum. This also causes random noise on the mass spectrum and chromatogram.

These noises are the direct causes of deterioration of LC / MS performance. Further, the entry of the liquid droplets contaminates the mass spectrometer and the detector and hinders stable measurement. A simple way to remove the droplets is to thoroughly heat and vaporize the mist. However, bio-related substances such as sugar and protein, antibiotics,
Many LC / MS substances to be analyzed such as pesticides are easily thermally decomposed by heating, which makes accurate mass spectrometry impossible. Therefore, extreme heating should be avoided.

Therefore, a method has been proposed in which a means for separating droplets and ions taken into a high vacuum is provided in the preceding stage of the mass spectrometer (Japanese Patent Laid-Open No. 7-85834, USP 5,48).
1, 107). The outline is shown in FIG. The sample solution is atomized by being atomized by the atmospheric pressure ion source 3. The generated ions pass through the ion sampling pore 15a and the exhaust system 7
It is introduced into the intermediate pressure portion 33 exhausted by a. The ions are further introduced into the high-vacuum mass spectrometric section 34 exhausted by the vacuum system 7b through the fine holes 15b. The ions are converged by the Einzel lens 20 and enter the deflector 21. The ions are deflected here, enter the entrance hole 19 of the mass analysis unit 6, are mass analyzed by the mass analysis unit 6, and are detected by the detector 8
Detected in. On the other hand, the fine neutral droplets are deflected by the deflector 21.
At the same time, it does not deflect and goes straight, collides with the outer tube 35 of the mass spectrometric section 6, and does not enter the mass spectrometric section 6.

The deflector 21 utilizing the electric field not only deflects the ions, but also selects the kinetic energy of the ions. Ions with uniform energy can be sent to the mass spectrometer 6 to obtain good resolution.

Although this method is excellent in removing neutral droplets, it has the following problems.

(1) Ions of high solid angle cannot be focused.

First, the ions introduced from the ion sampling pore 15b are generally converged by the Einzel lens 20. The Einzel lens is generally composed of three electrodes as shown in FIG. The ions emitted from the object point 52 are accelerated by the ion acceleration electric field between the object point 52 and the first electrode 53, and enter the hole 56 provided at the center of the first electrode. A lens-shaped electric field is formed in the vicinity of the central hole 57 of the central electrode 54 by the lens voltage supplied from the Einzel power source 51 and applied between the central electrode 54 and the front and rear electrodes. The ions are converged by this lens-shaped electric field and are emitted to the outside from the hole 58 at the center of the third electrode 55. Finally, it converges to a convergence point 59 on the extension of the central axis of the lens. If the entrance hole 19 of the mass spectrometric section 6 is placed at this convergence point, the ions are introduced into the mass spectrometric section 6.
The Einzel lens is often used because it has an extremely simple structure and can focus ions and electrons.

Ions that have entered the high vacuum region 34 from the ion sampling pore 15b rapidly diffuse together with gas molecules at the outlet of the ion sampling pore 15b. The Einzel lens cannot make a lens having a large diameter because of its structure. Even if ions near the central axis can be focused, diffused ions cannot be focused. Therefore, the ions entering at a high solid angle cannot be converged, and the sensitivity is greatly impaired. For highly sensitive measurement, the diffused ions must be efficiently converged and sent to the next mass spectrometric section.

(2) Kinetic energy spreads when the ions are accelerated.

In order to efficiently send the ions generated under the atmospheric pressure and introduced from the ion sampling pores 15a to the mass spectrometric section 6, the accelerating convergence of the ions by using the ion accelerating electrode, the Einzel lens or the like is at an intermediate pressure. This is performed in the former part of the unit 33 and the mass spectrometric unit 6. However, in the case of accelerating the ions in the intermediate pressure portion 33 where the vacuum is bad or the incident portion of the mass spectrometric portion 6, frequent collisions between the neutral residual gas molecules and the ions are caused. Due to this collision, the ions are diffused or a part of the kinetic energy of the ions is lost, resulting in the spread of the kinetic energy of the ions. In order to reduce the spread of the kinetic energy of the ions, the acceleration of the ions is kept as low as possible in the high pressure region (about 1000 Pa to about 1 Pa) such as the intermediate pressure portion 33, and the mass of the high vacuum (about 10 ⁻³ Pa) is set. A method of accelerating at once after entering the analysis unit 6 is used. However, since the ion accelerating electrode, the electrode of the Einzel lens 20, the deflector 21 and the like are arranged in the vicinity of the ion sampling pore 15b, these become a large resistance to vacuum exhaust.
Therefore, the vacuum in the vicinity of these electrodes becomes worse, and the scattering of ions and the spread of kinetic energy due to frequent collisions with neutral molecules during ion acceleration are unavoidable.

(3) The deflector may diffuse ions having kinetic energy spread.

The deflector 21 not only deflects ions but also serves as an energy selector. Therefore, ions having the same energy converge to one point even if they have different masses. On the contrary, the ions with different energies converge to another place and the pores 1
I can't go through 9. Therefore, if the deflector 21 deflects ions having a wide kinetic energy, there will be a large number of ions that do not converge at the mass analysis unit inlet hole 19. That is, many ions that cannot pass through the mass spectrometric unit entrance hole 19 are lost, resulting in a decrease in sensitivity.

An LC / MS has been proposed which improves the S / N ratio without using a deflector (Japanese Laid-Open Patent Publication No. 7-130325). This LC / MS is shown in FIG. This is the pores 15a, 15b for sampling the ions generated under the atmospheric pressure in the ion source 3 into the high-vacuum mass spectrometric section.
An ion transfer system having a function of removing neutral particles and a mass spectrometric section 6 are coaxially arranged. The ion transfer system includes two Einzel lenses 101 and 102 and a screen electrode 45, and the first Einzel lens 10
Ions incident on 1 are diffused by a lens having a concave lens action. Neutral particles and light go straight, and screen electrode 4
Clash with 5. The ions go around the screen electrode 45, enter the second Einzel lens 102, and are converged by the convex lens action of this lens. This ion transfer mechanism can prevent light and neutral particles from entering the mass spectrometric section 6. In addition, 8 is a detector.

Since this method uses an Einzel lens for the lens, ions with a high solid angle cannot be efficiently transferred. Further, the problem of spread of kinetic energy of ions due to deterioration of vacuum cannot be overcome.

In the case of the plasma MS, as in the case of the LC / MS, neutral particles and light are introduced into the mass spectrometric section and the detector, which causes noise. A method of preferentially introducing ions without introducing neutral particles or light into the mass spectrometric section is disclosed in JP-A-2-24.
8854 and JP-A-3-194843.

FIG. 19 shows a plasma mass spectrometer described in JP-A-2-248854. Ions generated in plasma under atmospheric pressure in the plasma torch ion source 32 are provided with pores 15a provided in the center of the two-stage skimmer.
Sampling in vacuum via 15b. Ions are intended to be converged by the Einzel lens 103 and then deflected toward the entrance pore 19 of the mass spectrometric section 6 by the parallel plate or the quadrupole deflector 104. This method has the above-mentioned three drawbacks, and the focusing and deflecting system becomes complicated and expensive. Also, it becomes difficult to make adjustments to obtain the best point. In addition, 8 is a detector.

FIG. 20 shows a plasma mass spectrometer described in JP-A-3-194843. This is substantially the same as FIG. 19 except that one Einzel lens 106 is used for ion focusing. Since the Einzel lens is used, the drawbacks of the above (1) and (2) are directly applicable. In addition, since there is a high possibility that the ions in the central portion will be blocked together with light and neutral particles, a decrease in sensitivity cannot be denied.

An object of the present invention is to reduce the spread of kinetic energy of ions due to deterioration of vacuum and to effectively converge ions with a high solid angle to perform mass spectrometry with a high S / N ratio. It is to provide a barometric pressure ionization mass spectrometer.

Another object of the present invention is to provide an atmospheric pressure ionization mass spectrometer suitable for effectively separating neutral molecules from ions.

Yet another object of the present invention is to provide an atmospheric pressure ionization mass spectrometer suitable for facilitating the kinetic energy selection of ions to be focused.

[0027]

SUMMARY OF THE INVENTION According to one aspect of the present invention, an atmospheric pressure ionization source that ionizes a sample under atmospheric pressure to generate the ion and an ion sampling probe for the generated ion are provided. In an atmospheric pressure ionization mass spectrometer equipped with a mass spectrometric unit that is introduced through a hole to perform mass spectrometric analysis, the first and second electrode systems arranged between the ion sampling pore and the mass spectrometric unit are provided. Prepare,
The first electrode system has a plurality of hemispherical grid electrodes that pass the ions from the sampling pores, and the second electrode system directs the ions from the first electrode system to the mass spectrometric section. Having a plurality of hemispherical grid electrodes,
The plurality of grid electrodes of the first electrode system are recessed on the sampling pore side, the plurality of grid electrodes of the second electrode system are recessed on the opposite side of the sampling pore, Thereby, the ions from the second electrode system are converged to the converging position.

According to another aspect of the present invention, an atmospheric pressure ionized ion source for ionizing a sample under atmospheric pressure to generate the ion and an ion sampling pore for sampling the generated ion are provided. In an atmospheric pressure ionization mass spectrometer equipped with a member and a mass spectrometric section for introducing the sampled ions into the mass spectrometric section through the inlet hole thereof for mass spectrometric analysis, the ion sampling pores and the mass spectrometric analysis First placed between and
And a second electrode system, wherein the first electrode system has a plurality of hemispherical grid electrodes that allow ions from the sampling pores to pass therethrough and are recessed toward the sampling pores. The electrode system of (1) has a plurality of hemispherical grid electrodes that are recessed on the side opposite to the sampling pores through the ions from the first electrode system toward the mass spectrometric section. The axis and the axis of the first electrode system coincide with each other, the axis of the second electrode system coincides with the axis of the entrance hole of the mass spectrometric section, and the axis of the ion sampling pore and the entrance of the mass spectrometric section Characterized by the intersecting axes of the holes.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION Journal of Physics E: Scientif
ic Instruments, Vol. 5 (1972) pp. 484-487, discloses an electrode system used in an electronic energy analyzer by Staib. FIG. 21 shows the electrode system. The electrons generated by the electron source 66 fly and reach the hemispherical mesh-shaped grid electrode 41. The electrons that have passed through the grid electrode 41 are decelerated by the deceleration electric field applied between the grid electrode 41 and the grid electrode 42. If the kinetic energy of the electron is smaller than the deceleration electric field, the electron is pushed back. The electrons that exceed the deceleration electric field continue to fly even after being decelerated, pass through the grid electrode 42, and enter the electric fieldless space 49. The electrons further pass through the grid electrode 43, are accelerated by the accelerating electric field applied between the grid electrode 43 and the grid electrode 44, and are converged in the pores 65 on the extension of the central axis of the electrodes. When the energy of the electron is small, the electron is in front of the central axis, and when the energy is large, the central axis 17
Converge towards the back of. The detector 64 is placed behind the pore 65 to detect electrons. 66 is a screen electrode that shields electrons passing near the central axis 17. The energy of electrons is measured by controlling the deceleration electric field and the acceleration electric field.

In the present invention, the concept of this electrode system is LC / M.
Applied to atmospheric pressure ionization mass spectrometers such as S and plasma MS, and used for accelerating, focusing and deflecting ions and separating neutral particles and light, to solve the problems of the known technology mentioned above. Is what you are trying to do.

First Embodiment FIG. 1 shows an embodiment of an atmospheric pressure ionization mass spectrometer according to the present invention.

The sample solution separated by a means for separating a mixture such as a liquid chromatograph is introduced into the ion source 3. Ions originating from sample molecules are generated in the ion source 3 under atmospheric pressure, and the ion sampling pores 15
a and 15b, and the sampled ions are introduced into the high vacuum region 34. Intermediate pressure portion 33 between the ion sampling pores 15a and 15b
Is evacuated by the vacuum evacuation system 7a. When the ions are introduced into the intermediate pressure region 33 of the vacuum, the ions are rapidly cooled by adiabatic expansion. As a result, polar molecules such as solvent water and alcohol adhere to the ions and generate so-called cluster ions. Cluster ions consist of many molecules such as water attached to the ions, and their mass is very different from that of bare ions. Correct mass analysis cannot be performed by mass analysis of this cluster as it is. In order to prevent generation of cluster ions, ion sampling pores 15a, 1
Although the vicinity of 5b is heated to about 100 ° C., this cannot prevent the generation of cluster ions.

FIG. 2 shows an ion acceleration and focusing section. Further, FIG. 3 schematically shows the accelerated and converged states of ions. Ions introduced from the ion sampling pores 15b to the high vacuum region 34, which is evacuated to a high vacuum by the vacuum exhaust system 7b, have a hemispherical shape of four electrodes.
Grid electrodes 41, 42, 43, 4 with one mesh structure
At 4, the vehicle is decelerated, accelerated, and converged. The grid electrode 41 and the grid electrode 42 form a first electrode system. The common center of these electrodes is located in the ion sampling pore 15b. The radii of the two grid electrodes are different, and the radius of the grid electrode 41 is smaller than the radius of the grid electrode 42. The second electrode system is composed of a grid electrode 43 and a grid electrode 44. The common center of these electrodes is located in the pore 21 on the opposite side (on the side of the mass spectrometric section) of the ion sampling pore 15b. The radius of the grid electrode 43 is larger than the radius of the grid electrode 44. Ion sampling pore 15b, grid electrodes 41, 42, 43,
Center of 44, pore 21 and entrance hole 1 of mass spectrometric section 6
9 are arranged on the same shaft 17.

Ions are accelerated by the ion acceleration potential applied between the electrode 41 and the ion sampling pore 15b (partition wall 16). Ions are ion sampling pores 1
It flies radially from 5b toward the grid electrode 41, passes through the surface of the grid electrode 41, and reaches the space between the grid electrode 41 and the grid electrode 42. The ions are decelerated here by the ion deceleration electric field applied between the grid electrode 41 and the outer grid electrode 42. Due to the deceleration due to the electric field opposite to the flight direction of the ions, the deceleration electric field pushes back the ions having small kinetic energy. Ions exceeding the deceleration electric field continue to fly without changing their direction even when decelerated. That is, the lower limit of the kinetic energy (ie,
Ions below the deceleration potential can be cut off and cut off. If the deceleration potential can be changed and adjusted from the outside,
The optimum cutoff value can be searched for while observing the actual mass spectrum.

The grid electrode 42 and the grid electrode 43 are set to the same potential, so that there is no electric field. Two electrodes 42,
If a ring-shaped shield electrode 46 that connects 43 is provided, a region 49 surrounded by these electrodes becomes a non-electric field region. Ions having a slight excess of kinetic energy fly in the field-free region 49 without changing the direction, and the grid electrode 43
Is reached (points 37a, 37b, 38a, 38b). Here, the ions are accelerated toward the center 21 of the electrode by the ion acceleration electric field applied to the grid electrode 43 and the grid electrode 44. Ions having no excess kinetic energy are focused on the center 21 of the grid electrodes 43 and 44. Ions having a slight excess of kinetic energy gradually converge from the smaller ion energy to the larger ion energy as the distance from the central axis of the electrode increases. Now, when the plate-shaped electrode 20 is placed at the center 21 of the grid electrode, as shown in FIG. 3B, the ions with small kinetic energy in the vicinity of the center and the ions with large energy sequentially reach the larger radius in concentric circles. Then, those ions are focused on the positions of 21 and 21a, respectively. Therefore, ions having excess kinetic energy are blocked by the electrode 20.

When a quadrupole mass spectrometer is used as the mass spectrometer, if ions having a kinetic energy spread of 1 eV or more are introduced into the mass spectrometer, the resolution of the mass spectrum deteriorates. In the case of the present invention, the diameter of the hole may be set so that ions having an energy spread of 1 eV or more cannot pass through the entrance hole 19 of the mass spectrometric section 6.

The inlet hole 19 of the mass spectrometric section 6 may be directly used as an energy limiting slit without providing the energy limiting pore 21. Alternatively, the acceleration voltage of the grid electrodes 43, 44 may be adjusted so that only ions having an excessive kinetic energy of 1 eV or less can pass through the entrance hole 19 of the mass spectrometric section 6. That is, ions having a large excess energy can be cut by adjusting the diameter of the entrance hole 19 of the mass spectrometric section or the acceleration voltage. As a result, high resolution can be obtained in mass spectrometry.

The specific voltage application to the grid electrode depends on the structure of the device and the mass spectrometer. When a quadrupole mass spectrometer or an ion trap mass spectrometer is used for the mass spectrometer, the acceleration voltage can be set to several tens V or less. In the case of a magnetic field type mass spectrometer, high voltage acceleration of several kV is required. When measuring positive ions with a quadrupole mass spectrometer, the acceleration voltage applied to the ion sampling pore 15a (partition wall 16) is about + 30V. + For the grid electrode 41
10V, +29 to +30 for grid electrodes 42 and 43
V, grid electrode 44, mantle 3 with inlet hole 19
About + 10V is applied to 5. These voltages are the power supply 7
It is given from 0 and can be changed arbitrarily (power source 70
Are omitted in figures other than FIG. 1 in order to avoid complication of the figure).

The ion transfer system from the ion sampling pores 15b to the shield cylinder 35 efficiently converges ions having a narrow kinetic energy width and a high solid angle, and introduces them into the mass spectrometric section 6. The ions are now mass analyzed and the mass analyzed ions are detected by the detector 8.

If a screen electrode 45 for blocking neutral particles is provided at the center of the four electrodes, the neutral particles go straight and collide with the screen electrode 45. The neutral particle beam 23 having a solid angle larger than that of the screen electrode 45 does not reach the entrance hole 19 of the mass spectrometric section. The screen electrode 45 can be placed between the ion sampling pore 15b and the entrance hole 19 of the mass spectrometric section 9 and anywhere on the central axis 17.
However, the electrodes 42, 4 where the ion beam becomes the thickest
It's easy to put in between three.

The advantage of this lens system is that the ions can be efficiently converged even if the ion source is large and the ion emission angle (solid angle) is large. Also,
Neutral particles can be prevented from entering the mass spectrometer section 6 by the screen electrode 45. Also, unlike the deflector,
Ions having different energies are arranged on the central axis 17, and the selection can be easily adjusted by the diameter of the hole of the entrance of the mass analysis unit, the installation position, and the applied voltage of the grid electrode, and the optimum energy accepted by the mass analysis unit. Can be easily adjusted.

The grid electrodes 41, 42, 43, 44 have hemispherical grid portions having a mesh structure. The edges and the like may be metal plates for easy assembly. Unlike ordinary Einzel lenses, this lens system has good air permeability and can reduce exhaust resistance. Therefore, the efficiency of vacuum exhaust around the lens system is improved,
A high degree of vacuum can be obtained. Therefore, the chance of ion scattering due to collision with neutral particles of ions under low vacuum can be reduced, and the spread of kinetic energy can be reduced.

The shielding screen may not be provided as an electrode separate from the four grid electrodes, but may be provided in a screen shape on one of the four grid electrodes. The grid electrode is
A thin metal plate can be manufactured by etching or the like.
At this time, if the central portion of one grid electrode is not etched, the shield screen can be easily manufactured.

In this embodiment, the shield electrode 46 has the same potential as the grid electrodes 42 and 43, but a potential may be applied to push back the ions toward the central axis to reduce the spread of the ion beam as much as possible. it can.

Second Embodiment In the first embodiment, the ion sampling pore 15 is used.
b, the central axes of the grid electrodes 41 and 42 (first electrode system), the central axes of the grid electrodes 43 and 44 (second electrode system), and the mass spectrometer inlet hole 19 are aligned on the same axis 17. . The neutral particles exiting the ion sampling pores 15b go straight without being deflected by the grid electrode. A screen electrode 45 is provided at the center of the electrode so that it does not enter the mass analysis unit inlet hole 19. The screen electrode 45 can efficiently remove neutral particles, but on the other hand, it also blocks the ions that go straight along with the neutral particles. The density of the ions ejected from the ion sampling pores 15b is highest in the central portion. By shutting off the central ions,
Sensitive analysis is compromised.

The second embodiment is of a type in which all ions pass through the lens system and neutral particles do not enter the mass spectrometric section. FIG. 4 shows a second embodiment according to the present invention, and FIG. 5 shows a lens system for ion acceleration, focusing and deflection.

The central axes 47 of the ion sampling pores 15d, the grid electrode 41a and the grid electrode 42a (first electrode system) are aligned with each other. The grid electrode 43a, the grid electrode 44a (second electrode system), and the mass analysis unit inlet hole 19
The central axis 48 of a is also matched. Furthermore, these central axes 4
Arrange so that 7, 48 intersect. In an actual device, the flanges of the partition walls 24 and 16a having the ion sampling pores may be slightly inclined and mounted on the MS vacuum block.

Ions exiting the ion sampling pore 15d through the ion sampling pore 15c are accelerated by the ion acceleration electric field applied between the ion sampling pore 15d and the grid electrode 41a, and pass through the grid electrode 41a. The ions are decelerated by the reverse potential between the grid electrode 41a and the grid electrode 42a. Ions with small excess energy are pushed back here. Other ions continue to fly, pass through the grid electrode 42a, and fly in the electric fieldless space. Ions reaching the points (points 39, 40) on the grid electrode 43a are generated by the grid electrodes 43a and 44a.
It is accelerated by the ion accelerating electric field applied between them, and converges at the center of the grid electrode 43a and the grid electrode 44a, that is, at the entrance hole 19a of the mass spectrometer. Neutral particles are electrodes 41
It goes straight (solid angles 50a, 50b) without being affected by the electric field between a, 42a, 43a, 44a, collides with the outer wall of the outer tube 35 of the mass spectrometric section 6, and does not enter the mass spectrometric section 6.

In this embodiment, the ion sampling pore 1
The ions leaving 5d are efficiently introduced into the mass spectrometric unit,
Enables highly sensitive measurement.

Examples 1 and 2 show examples in which an electrospray ion source is used as the atmospheric pressure ion source for LC / MS. However, the present invention is currently widely used together with electrospray ionization as atmospheric pressure ionization, such as atmospheric pressure chemical ionization (APCI), sonic spray ionization (SSI), and atmospheric pressure spray ionization (ASI).
It is also applicable to PS) and the like.

Third Embodiment FIG. 6 shows a third embodiment according to the present invention. This shows an example using capillary electrophoresis instead of LC as the separation means.

The sample is first introduced into the capillary 27, and the capillary 2 is supplied with a high voltage of several tens of kV which is supplied from the high voltage power source 28 through the buffer solution 29 filled in the beaker 26.
7 is run and separated into each component. The eluted component is sent to the spray capillary of the electrospray ion source 3 after adding an additional liquid (sheath flow). The sample is electrosprayed and ionized. The ions pass through the ion sampling pores 15a and 15b, and the mass spectrometric unit 34
Will be introduced to. Ions are hemispherical grid electrodes 41, 4
Reach the mass spectrometer entrance 19 via 2, 43, 44,
Mass analyzed. Neutral particles are removed by the screen 45.

A combination of this capillary electrophoresis and Example 2 is also possible.

Fourth Embodiment FIG. 7 shows a fourth embodiment according to the present invention. The present invention is L
It can be applied not only to C / MS, but also to a mass spectrometer that ionizes under atmospheric pressure. For example, it can also be applied to a mass spectrometer equipped with a plasma ion source used for the analysis of a very small amount of elements, that is, an inductively coupled plasma (ICP) or a microwave inductive plasma (MIP) ion source. FIG. 7 shows an example thereof.

The sample is supplied from the high frequency power source 31 to the supply line 30.
Then, the high frequency is supplied to the plasma ion source 32. Ions of the sample generated in the high-temperature plasma of several thousands degrees K produced by the high-frequency waves are ion sampling pores 15
It is introduced into the mass spectrometric section 34 through a and 15b. In this case, the ions can be efficiently guided to the mass spectrometric section while blocking the photons emitted from the plasma in addition to blocking the neutral particles.

A combination of the plasma ion source and the second embodiment is also possible.

Fifth Embodiment FIG. 8 shows a fifth embodiment according to the present invention. In the second embodiment, the central axes of the ion sampling pores 15d and the first electrode system (grid electrodes 41, 42) coincide with each other, and
The central axes of the second electrode system (grid electrodes 43 and 44) and the mass analysis unit inlet hole 19 coincide with each other, and these two axes intersect each other.

In the fifth embodiment, the central axes of the first and second electrode systems and the mass spectrometric unit inlet hole 19 coincide with each other, and this central axis intersects with the central axis of the ion sampling pore 15d. Ions generated under atmospheric pressure are introduced into the high vacuum region 34 through the ion sampling pores 15c and 15d.
The ions are accelerated by the acceleration voltage applied between the partition wall 16 and the grid electrode 41, and enter the first electrode system. Ions are deflected and converged by the first and second electrode systems, pass through the mass analysis unit inlet hole 19, and are mass analyzed by the mass analysis unit 6. Neutral particles and light travel straight without being affected by the first and second electrode systems and do not enter the mass spectrometric section 6.

In an actual device, the partition walls 24 and 16a having the ion sampling pores are mounted on the vacuum block of the mass spectrometer so that the flanges of the partition walls are slightly inclined.

In the embodiments shown in FIGS. 1, 4, 6, 7 and 8, the ions generated in the atmosphere are introduced into the vacuum through the ion sampling pores 15a or 15c provided at the center of the gap. This ion sampling pore may be replaced with a capillary 62 as shown in FIG. 9 (sixth embodiment according to the present invention) and FIG. 10 (seventh embodiment according to the present invention). Ion sampling pores 15b to the high vacuum region 34 may also be provided at the apex of the gap (FIG. 1).
0). Further, as shown in FIG. 9, fine holes 63 may be provided in the flat plate electrode. Furthermore, in order to promote vaporization of droplets, the capillary 62 can be heated to prevent cooling due to adiabatic expansion in vacuum. Further, as shown in FIG. 11 (eighth embodiment according to the present invention), the capillary 62a may be inclined.

In the above embodiment, the first and second electrode systems have the ion sampling pores 15b, 15 in the high vacuum region 34.
It is placed between d or the pore 63 and the mass spectrometric section 6. As shown in FIG. 12 (the ninth embodiment of the present invention), the first,
The second electrode system can also be placed in the intermediate pressure section 33.
In the intermediate pressure region, the ions collide with the residual gas molecules and show diffusion and energy spread. Ions that are widely diffused are also converged by the hemispherical grid electrode, and the ion sampling pores 1
Ions can be efficiently sent to 5b.

FIG. 13 shows a tenth embodiment according to the present invention. This is because the ions introduced into the high vacuum portion 34 from the ion sampling pores 15b are temporarily transferred to the Einzel lens 6
4, and the ions and neutral particles are selected by the first and second electrode systems via the pores 65. According to this, it is possible to prevent the first electrode system and the ion sampling pore 15b from approaching each other and making the assembly difficult. Furthermore, the pores 65 allow the neutral particles to be removed more efficiently.

When a potential for decelerating the ions is applied between the plurality of grid electrodes of the first electrode system, the ions whose kinetic energy is below this potential are pushed back, and the kinetic energy of the ions can be cut off. However, ions having low kinetic energy are less likely to adversely affect resolution and transmittance than ions having excessive energy. If the resolution is compromised to some extent, these ions with small kinetic energy can be sent to the MS. In this case, the potential applied to the grid electrode of the first electrode system may be the same potential instead of the potential for ion deceleration. Also, the second electrode of the first electrode system can be removed. It is also possible to accelerate slightly.

In the embodiment, the number of grid electrodes formed in each of the first and second electrode systems is two, but it is possible to increase the number to three or more. Although the structure of the electrode has been described as a hemispherical shape, the grid surface may be a part of a spherical surface. It should be understood that the term hemispherical is not a term in which its strictness is an issue, and includes a hyperbolic shape having a focus and an elliptical shape.

According to the above-described embodiment, it is possible to effectively converge ions with a high solid angle and reduce mass spread of kinetic energy of ions due to deterioration of vacuum to perform mass spectrometry with a high S / N ratio. it can. In addition, the kinetic energy of ions can be easily selected, and neutral particles and photons are effectively shielded, that is, neutral particles and photons are effectively separated from the ions, and noise due to neutral particles and photons is generated. Can be suppressed.

[0066]

According to the present invention, it is suitable for effectively focusing ions having a high solid angle and performing mass spectrometry with a high S / N ratio while reducing the spread of kinetic energy of ions due to deterioration of vacuum. An atmospheric pressure ionization mass spectrometer is provided.

The present invention also provides an atmospheric pressure ionization mass spectrometer suitable for effectively separating neutral molecules from ions.

The present invention further provides an atmospheric pressure ionization mass spectrometer suitable for facilitating the selection of kinetic energy of ions to be focused.

[Brief description of drawings]

FIG. 1 is a first atmospheric pressure ionization mass spectrometer according to the present invention.
2 is a conceptual diagram of the overall configuration of the embodiment of FIG.

FIG. 2 is a three-dimensional schematic view of the ion focusing system of the first embodiment according to the present invention.

3A and 3B are diagrams for explaining an ion focusing system of a first embodiment according to the present invention, FIG. 3A is an ion optical system diagram thereof, and FIG. 3B is a diagram showing a focused state of ions on an electrode 20. .

FIG. 4 is a second atmospheric pressure ionization mass spectrometer according to the present invention.
2 is a conceptual diagram of the overall configuration of the embodiment of FIG.

FIG. 5 is a schematic ion optical system diagram of an ion focusing system according to a second embodiment of the present invention.

FIG. 6 is a third atmospheric pressure ionization mass spectrometer according to the present invention.
2 is a conceptual diagram of the overall configuration of the embodiment of FIG.

FIG. 7 is a fourth atmospheric pressure ionization mass spectrometer according to the present invention.
2 is a conceptual diagram of the overall configuration of the embodiment of FIG.

FIG. 8 is a fifth example of an atmospheric pressure ionization mass spectrometer according to the present invention.
2 is a conceptual diagram of the overall configuration of the embodiment of FIG.

FIG. 9 is a sixth example of the atmospheric pressure ionization mass spectrometer according to the present invention.
2 is a conceptual diagram of the overall configuration of the embodiment of FIG.

FIG. 10 is an overall configuration conceptual diagram of an atmospheric pressure ionization mass spectrometer according to a seventh embodiment of the present invention.

FIG. 11 is an overall configuration conceptual diagram of an eighth embodiment of an atmospheric pressure ionization mass spectrometer according to the present invention.

FIG. 12 is an overall configuration conceptual diagram of an atmospheric pressure ionization mass spectrometer according to a ninth embodiment of the present invention.

FIG. 13 is an overall configuration conceptual diagram of a tenth embodiment of an atmospheric pressure ionization mass spectrometer according to the present invention.

FIG. 14 is a conceptual diagram of a known liquid chromatograph direct coupling mass spectrometer.

FIG. 15 is a conceptual diagram of a known liquid chromatograph direct-coupled mass spectrometer equipped with an electrospray ion source.

FIG. 16 is a schematic diagram of a conventional mass spectrometer having means for separating liquid and ions.

FIG. 17 is a conceptual diagram of a known eye lens lens.

FIG. 18 is a conceptual diagram of a known liquid chromatograph direct coupling mass spectrometer with an improved S / N ratio without using a deflector.

FIG. 19 is a conceptual diagram of a known plasma mass spectrometer.

FIG. 20 is a conceptual diagram of another known plasma mass spectrometer.

FIG. 21 is a conceptual diagram of a known electrode system used in an electron energy analyzer.

[Explanation of symbols] 1: Liquid chromatograph (LC), 2: Connection tube,
3: Ion source, 4: Ion source power supply, 6: Mass spectrometric section, 7
a, 7b: Vacuum exhaust system, 8: Ion detector, 9: Data processor, 11: Capillary, 12: Counter electrode, 13: Gas jet port, 14: Counter gas jet port, 15, 15a,
15b, 15c, 15d Ion sampling pores, 1
6, 16a: Partition wall, 17: Central axis, 19, 19a: Mass spectrometer inlet hole, 20: Electrode, 21: Pore, 24: Partition wall, 25: Spray auxiliary gas, 26: Beaker, 27: Capillary, 28: Capillary electrophoresis power supply, 29: buffer solution, 30: voltage supply line, 31: plasma ion source power supply, 32: plasma ion source, 33: intermediate pressure part, 3
4: high vacuum part, 35: outer tube, 36: counter gas, 4
1, 41a: first grid electrode, 42, 42a: second
Grid electrodes, 43, 43a: third grid electrode,
44, 44a: fourth grid electrode, 45: screen electrode, 46: shield electrode, 47, 48 central axis, 4
9: Electroless space, 51: Einzel power source, 52: Object point, 53: First electrode, 54: Second electrode, 55: Third
Electrode, 62: ion introduction capillary, 63: ion sampling pore, 64: Einzel lens, 65: limiting pore, 66: screen electrode, 70: power supply.

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01J 49/06 G01N 27/62

Claims (5)

(57) [Claims] 1. An atmospheric pressure ionization ion source for ionizing a sample under atmospheric pressure to generate the ions, and a mass spectrometric section for introducing the generated ions through ion sampling pores for mass analysis. In the atmospheric pressure ionization mass spectrometer, there are provided first and second electrode systems arranged between the ion sampling pores and the mass spectrometric section, and the first electrode system is provided from the sampling pores. A plurality of hemispherical grid electrodes through which ions pass, wherein the second electrode system includes a plurality of hemispherical grid electrodes through which ions from the first electrode system are directed toward the mass spectrometric analysis unit; A plurality of grid electrodes of one electrode system is recessed to the sampling pore side, a plurality of grid electrodes of the second electrode system is recessed to the opposite side to the sampling pores, Atmospheric pressure ionization mass spectrometer, wherein the converging to the convergence position ions from the second electrode system by Les. 2. The atmospheric pressure ionization mass spectrometer according to claim 1, further comprising a screen for shielding neutral particles from the sampling pores. 3. The atmospheric pressure ionization mass spectrometry according to claim 2, wherein the screen is arranged on a central axis between the first electrode system and the second electrode system. Total. 4. An atmospheric pressure ionized ion source for ionizing a sample under atmospheric pressure to generate the ions, a member having ion sampling pores for sampling the generated ions, and a mass of the sampled ions. In an atmospheric pressure ionization mass spectrometer comprising a mass spectrometric section introduced into the spectroscopic section through its inlet hole for mass spectrometric analysis, a first element arranged between the ion sampling pore and the mass spectrometric section. And a second electrode system, wherein the first
Of the electrode system has a plurality of hemispherical grid electrodes that allow ions from the sampling pores to pass therethrough and are recessed toward the sampling pores, and the second electrode system includes a plurality of hemispherical grid electrodes. It has a plurality of hemispherical grid electrodes that are recessed on the side opposite to the sampling pores and through which ions pass, and the axis of the ion sampling pores and the axis of the first electrode system are aligned. The axis of the second electrode system coincides with the axis of the inlet hole of the mass spectrometric section, and the axis of the ion sampling pore and the axis of the inlet hole of the mass spectrometric section intersect. Atmospheric pressure ionization mass spectrometer. 5. The ion according to claim 1, wherein the ions are decelerated between a plurality of grid electrodes of the first electrode system and are accelerated between a plurality of grid electrodes of the second electrode system. An atmospheric pressure ionization mass spectrometer characterized by the above.