WO2014050836A1 - 質量分析装置および質量分離装置 - Google Patents
質量分析装置および質量分離装置 Download PDFInfo
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- WO2014050836A1 WO2014050836A1 PCT/JP2013/075780 JP2013075780W WO2014050836A1 WO 2014050836 A1 WO2014050836 A1 WO 2014050836A1 JP 2013075780 W JP2013075780 W JP 2013075780W WO 2014050836 A1 WO2014050836 A1 WO 2014050836A1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J49/00—Particle spectrometers or separator tubes
- H01J49/26—Mass spectrometers or separator tubes
- H01J49/34—Dynamic spectrometers
- H01J49/40—Time-of-flight spectrometers
- H01J49/401—Time-of-flight spectrometers characterised by orthogonal acceleration, e.g. focusing or selecting the ions, pusher electrode
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/62—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J49/00—Particle spectrometers or separator tubes
- H01J49/004—Combinations of spectrometers, tandem spectrometers, e.g. MS/MS, MSn
- H01J49/0086—Accelerator mass spectrometers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J49/00—Particle spectrometers or separator tubes
- H01J49/02—Details
- H01J49/06—Electron- or ion-optical arrangements
- H01J49/061—Ion deflecting means, e.g. ion gates
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J49/00—Particle spectrometers or separator tubes
- H01J49/02—Details
- H01J49/06—Electron- or ion-optical arrangements
- H01J49/067—Ion lenses, apertures, skimmers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J49/00—Particle spectrometers or separator tubes
- H01J49/26—Mass spectrometers or separator tubes
- H01J49/34—Dynamic spectrometers
- H01J49/40—Time-of-flight spectrometers
- H01J49/408—Time-of-flight spectrometers with multiple changes of direction, e.g. by using electric or magnetic sectors, closed-loop time-of-flight
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J49/00—Particle spectrometers or separator tubes
- H01J49/26—Mass spectrometers or separator tubes
- H01J49/34—Dynamic spectrometers
- H01J49/42—Stability-of-path spectrometers, e.g. monopole, quadrupole, multipole, farvitrons
- H01J49/4205—Device types
- H01J49/421—Mass filters, i.e. deviating unwanted ions without trapping
Definitions
- the present invention relates to a mass spectrometer and mass separator for mass-separating ions using a one-dimensional high-frequency electric field.
- mass spectrometry the sample substance to be analyzed is ionized by an appropriate method, the generated ions are separated based on the difference in mass-to-charge ratio, and the composition of the sample substance is detected or quantified for each mass-to-charge ratio. It is an analytical method to obtain knowledge about structure and structure.
- mass-to-charge ratio is defined as “an ion mass m divided by an atomic mass constant (a mass of 1/12 of the mass of one 12 C atom) to obtain a dimensionless precise mass, Furthermore this will be used to define the non-number of dimensions "obtained by dividing the charge number z i ion.
- the mass spectrometer is composed of an ion source, an ion introduction unit, a mass analysis unit, an ion detection unit, and the like, and at least the mass analysis unit and ion passages before and after the mass analysis unit are under high vacuum.
- mass analyzer ionic species having different mass-to-charge ratios are separated according to the difference in ion motion in a vacuum.
- general-purpose mass spectrometers currently on the market, one of the following three types of mass spectrometers is used (see Non-Patent Documents 1 to 4).
- a group of a plurality of ions treated as one unit in each part of the mass spectrometer is referred to as an “ion group” in order to distinguish it from a single ion or a simple plurality of ions.
- the motion state that each ion of the ion source takes before being extracted by the acceleration voltage U is referred to as an initial state.
- the elementary quantity of electricity is represented by the symbol e, and the physical quantity is represented in SI units unless otherwise specified.
- TOF Mass Spectrometer ⁇ Time of Flight (TOF) Mass Spectrometer>
- ions of are pulsed manner extracted from the ion source at a predetermined acceleration voltage U, it is introduced to the free flight space length L F in the absence of an electric field or a magnetic field.
- the ion group is extracted from the ion source with a predetermined acceleration voltage U and given kinetic energy z i eU.
- the ion group is introduced into a sector magnetic field having a uniform magnetic flux density B so as to be orthogonal to the magnetic field.
- the ions in the magnetic field continue to be deflected in the flight direction by the Lorentz force and fly in a circular arc perpendicular to the magnetic field.
- quadrupole mass spectrometer In the quadrupole mass spectrometer, a quadrupole electric field is formed in an elongated space surrounded by four rod-shaped electrodes having the same shape, and this space is used as a passage for ions.
- the ion group is introduced along the center line from one end in the length direction, and flies inertially toward the other end while oscillating by the force received from the electric field.
- only ion species having a specific mass-to-charge ratio are adapted to the electric field, and can fly to the end in the passage while performing a stable oscillating motion.
- Other ions become too large in amplitude and are removed either by colliding with the rod-shaped electrodes or by jumping out of the passage from the gap between the rod-shaped electrodes.
- mass spectrometers equipped with a linear quadrupole or three-dimensional quadrupole ion trap mass spectrometer or a Fourier transform ion cyclotron resonance mass spectrometer are also commercially available.
- these ion trap mass spectrometers require ion introduction, retention, and discharge operations to perform one analysis, which makes the operation complicated. Also, the analysis operation becomes intermittent, and is not suitable for at least high-speed real-time measurement. Therefore, these mass spectrometers are mainly used for applications where the ion trap function is effective.
- the ion group of the ion source is extracted at a predetermined acceleration voltage U and given the same kinetic energy z i eU. Then, based on the difference in velocity or momentum in the extraction direction as a result, ion species having different mass-to-charge ratios are separated. In this case, kinetic energy of each ion in the initial state when not negligible compared to the z i eU is mass resolution by the variation is limited. For this reason, it is necessary to increase the acceleration voltage U in order to reduce the influence relatively and realize high mass resolution. As a result, the flight distance of ions becomes long and the apparatus becomes large.
- ions with a large mass-to-charge ratio are difficult to realize a stable vibration state and have a low transmittance.
- it is necessary to increase the voltage applied to the rod-shaped electrode but there are technical limitations such as withstand voltage and power. If the frequency of the high-frequency voltage is lowered, ions with a large mass-to-charge ratio can be measured without changing the high-frequency voltage, but in this case, the ions with a small mass pass through the mass analyzer without sufficiently vibrating. Occurs. For this reason, the upper limit of the mass-to-charge ratio that can be analyzed is limited to about 2000 to 4000.
- the existing mass spectrometer has insufficient performance for repeatedly measuring the amount of ions of a plurality of ion species having different mass-to-charge ratios in a short time. Next, this point will be described.
- the quadrupole mass analyzer and the sector magnetic mass analyzer can continuously measure the amount of ions in real time.
- a quadrupole mass spectrometer cannot detect a plurality of ion species having different mass-to-charge ratios.
- the sector magnetic mass analyzer can simultaneously detect a plurality of ion species by using a focal plane detector, but its mass-to-charge ratio range is narrow.
- the selection (switching) scanning requires about 1 ms for each ion species.
- the mass scanning of the sector magnetic mass analyzer is slower. The amount of ions of a plurality of ion species cannot be measured and compared within a time shorter than these scanning times.
- the ionization conditions in the ion source such as the pressure of the sample gas and the energy injected for ionization
- the ion amount of the ion species to be analyzed and the ions of the ion species used as the internal standard Even if the amount is measured by mass scanning and the variation of the ionization condition is corrected based on the internal standard, the variation occurring within the scanning time is not corrected, and the accuracy of quantification tends to be impaired.
- the composition of the sample changes within the scanning time, it is impossible to correctly grasp the relationship between the ion amounts among a plurality of ion species.
- GC-MS gas chromatograph mass spectrometer
- LC-MS liquid chromatograph mass spectrometer
- the TOF type mass spectrometer in principle, a complete mass spectrum can be obtained by introducing a single pulsed ion group. Therefore, the ion amount can be calibrated based on the internal standard, and the relationship of the ion amount among a plurality of ion species can be correctly grasped.
- it takes 100 ⁇ s at the shortest to complete the flight of one ion usually several ms to several tens of ms, it is not possible to track system changes at shorter time intervals. .
- the present invention has been made in view of such circumstances, and its purpose is that the design and performance of the apparatus are rarely limited by problems caused by the operating principle, and the mass that can be handled in principle. It is an object of the present invention to provide a mass spectrometer and a mass separator capable of repeatedly analyzing or taking out a plurality of ion species having different charge-to-charge ranges and different mass-to-charge ratios in a short time.
- An ion source comprising means for ionizing a sample, and means for introducing a pulsed ion group into the mass spectrometer with a predetermined acceleration voltage;
- An ion introduction section comprising means for converging the flight direction of the ion group and / or means for selecting and taking out the ion group flying in a predetermined direction;
- a separation space in which the introduced ion group flies and a one-dimensional high-frequency electric field that acts in a direction intersecting the incident direction of the ion group at a predetermined angle (hereinafter referred to as y direction) are formed in the separation space.
- a mass analyzing unit that causes ionic species having different mass-to-charge ratios to fly different flight paths by the action of the one-dimensional high-frequency electric field; At least an ion detector provided with means for detecting ions flying at a predetermined y-direction position on the exit surface at the end of the separation space, and the ion group is a pulse synchronized with the phase of the one-dimensional high-frequency electric field.
- the ion species to be measured introduced into the separation space and having a predetermined mass-to-charge ratio is emitted from the separation space after receiving the action of the one-dimensional high-frequency electric field for n periods or a period substantially equivalent to the period,
- the present invention relates to a mass spectrometer that is detected separately from other ion species based on the y-direction flying position on the exit surface (where n is a natural number).
- the present invention also provides: An ion source comprising means for ionizing a sample, and means for introducing a pulsed ion group into the mass spectrometer with a predetermined acceleration voltage; An ion introduction section comprising means for converging the flight direction of the ion group and / or means for selecting and taking out the ion group flying in a predetermined direction; A separation space in which the introduced ion group flies and a one-dimensional high-frequency electric field that acts in a direction intersecting the incident direction of the ion group at a predetermined angle (hereinafter referred to as y direction) are formed in the separation space.
- An ion source comprising means for ionizing a sample, and means for introducing a pulsed ion group into the mass spectrometer with a predetermined acceleration voltage
- An ion introduction section comprising means for converging the flight direction of the ion group and / or means for selecting and taking out the ion group flying in a predetermined
- a mass analyzing unit that causes ionic species having different mass-to-charge ratios to fly different flight paths by the action of the one-dimensional high-frequency electric field
- an ion selection unit that includes means for extracting ions flying to a predetermined y-direction position on the exit surface at the end of the separation space, and the ion group is a pulse synchronized with the phase of the one-dimensional high-frequency electric field.
- a selected ion species introduced into the separation space and having a predetermined mass-to-charge ratio is emitted from the separation space after receiving the action of the one-dimensional high-frequency electric field for a period or a period substantially regarded as equivalent thereto, and the emission
- the present invention relates to a mass separator that is taken out from other ion species based on the y-direction flying position on the surface.
- the high-frequency electric field has an arbitrary waveform, but is an alternating electric field in which the impulse received by the ions from the electric field during one period is 0, and the period is 2 ms or less.
- the ion species to be measured or the ion species to be selected does not simply mean an ion species to be detected or selected, but in relation to the essence of the present invention, the action of the one-dimensional high-frequency electric field is performed for one period. Alternatively, it refers to an ion species that is emitted from the separation space in a period that is substantially equivalent to that and is detected or selected. Further, “substantially” means that a slight increase / decrease or error in a range that does not change the essence of the present invention is allowed according to the required apparatus performance such as mass resolution.
- the ion group is introduced from the ion source into the separation space at the predetermined acceleration voltage. Thereafter, each ion flies with inertia in the incident direction and is displaced in the y direction by a force received from the one-dimensional high-frequency electric field acting in a direction intersecting the incident direction (y direction).
- This displacement is different from the constant acceleration motion in the electrostatic field, and the displacement is inversely proportional to the mass-to-charge ratio of the ions.
- the displacement also changes depending on the phase of the electric field when the one-dimensional high-frequency electric field starts to act on the ions, but the displacement becomes constant if the phase is fixed.
- the ion detector detects ions flying at a predetermined y-direction position on the exit surface.
- the y-direction flying position on the exit surface corresponds to the amount of displacement generated while ions fly in the separation space.
- the mass separation in the mass spectrometer is performed based on the difference in mass-to-charge ratio itself due to the displacement caused by the action of the one-dimensional high-frequency electric field.
- the movement of ions in the extraction direction is not involved in this displacement. Therefore, the mass separation in the mass analyzing unit is hardly affected by the influence of the variation in the initial state before the ion group is extracted.
- the kinetic energy accelerating voltage the group of ions drawn by U has a pull-out direction, while the standard z i eU, distributed in the vicinity with a spread corresponding to the variation in the initial state. Therefore, the velocity of ions in the extraction direction is (2z i eU / m) 1/2 as a standard, but spreads in the vicinity thereof.
- the time until the ions reach the end of the separation space is widened. If the amount of displacement of ions on the exit surface is widened due to the spread of the staying time, the mass resolution is limited due to variations in the initial state.
- the present inventor believes that the impulse that the ion receives from the high-frequency electric field becomes zero in one period, and therefore the change rate of the displacement amount becomes zero when the action of the one-dimensional high-frequency electric field is received for n periods. Based on this, it was found that the above problems could be solved, and the present invention was completed. That is, in the mass spectrometer according to the present invention, when the ion species to be measured is incident on the separation space and then receives the action of the one-dimensional high-frequency electric field for n periods or a period substantially equivalent thereto. The light is emitted from the separation space, or after being subjected to the action of the one-dimensional high-frequency electric field for n periods, and then emitted from the separation space during a rest period in which the electric field strength is zero.
- the light is emitted from the separation space, or after being subjected to the action of the one-dimensional high-frequency electric field for n periods, and then emitted from the separation space during a rest period in which the electric field
- the displacement amount of the ion species to be measured on the emission surface is not affected by the spread of the staying time.
- the mass spectrometer of the present invention is less affected by variations in the initial state, and the ion species to be measured is mass-separated with a higher mass resolution than in other cases. As a result, it is not necessary to increase the acceleration voltage in order to realize high mass resolution, and the apparatus is rarely increased in size.
- the mass separation of the mass spectrometer of the present invention is not based on the condition that the ions stably perform periodic motion such as vibration and rotation. Therefore, performance and functions are not limited by conditions and operations for realizing a stable state. Specifically, in principle, there is no limit to the range of mass-to-charge ratios that can be measured.
- the ion species to be measured finishes flying in the separation space for n periods and is distinguished from other ions by the difference in displacement, so that one ion species is changed to another ion species. The switching of the ion species to be measured is completed in about n cycles of the high-frequency electric field. Therefore, high-speed selective scanning is possible.
- FIG. 4 is a graph showing the relationship between the position of ions in the z direction and the displacement amount y at the time from the start of the sine wave high frequency electric field to the remainder of one period (11 ⁇ s) in the mass spectrometer.
- 4 is a graph showing the relationship between the position of ions in the z direction and the displacement y at a time from the start of the action of a rectangular high-frequency electric field having a rest period to the remainder of one cycle in the mass spectrometer.
- FIG. 6 is a graph (A) showing the flight path of each ion species in the mass spectrometer and a graph (B) showing the change when scanned by the first mass scanning method.
- FIG. 4 is a graph (A) showing an example of a rectangular high-frequency electric field used in the mass spectrometer, and a plan view (B) showing the position of ion species flying on the exit surface. It is a graph which shows the modification of the rectangular wave high frequency electric field used in a mass spectrometer similarly.
- the ion group is introduced into the separation space when the strength of the one-dimensional high-frequency electric field is zero, and the ion species to be measured has a strength of the one-dimensional high-frequency electric field substantially after one cycle. It is preferable to exit from the separation space at a time of 0 (where z i is the number of charges of the ion species, and m, e, U, L, and T are ions expressed in SI units, respectively.
- the length of the section that receives the action of. is a condition for the ions having the standard kinetic energy z i eU in the extraction direction among the ions of the ion species to be measured to pass through the effective length of the separation space in one period. Other ions pass through the effective length before and after. If the time of incidence of the ion group is limited as described above, there is an advantage that the amount of displacement during one period is maximized and the ion species to be measured is hardly affected by the edge field (fringe field).
- the one-dimensional high-frequency electric field has a rest period before and after one period in which the electric field strength is 0, and the ion species to be measured has the following relationship: T + T P ⁇ T L ⁇ T + T P + T 0
- the ion group is introduced into the separation space in the rest period before the one cycle, and the ion species to be measured is emitted from the separation space in the rest period after the one cycle.
- T L , T P , and T 0 are respectively expressed in SI units, and the time required for the ions of the ion species to be measured to pass through the effective length of the separation space is introduced by the ion group.
- the mass spectrometer using the one-dimensional high-frequency electric field having the rest period a plurality of the mass analyzers are continuously arranged, and the ion group is first mass-separated by the first-stage mass analyzer and separated. A part of the ion species is detected by the ion detector, and the rest is introduced into the subsequent mass analyzer, further mass separated, and detected by the ion detector disposed behind it. It is good. In this case, the remaining ion species to be measured move between the mass analyzers to the subsequent side during the rest period.
- the mass spectrometer using the one-dimensional high-frequency electric field having the rest period is arranged to be combined with the time-of-flight mass spectrometer so that the separation space forms a part of the flight space of the time-of-flight mass spectrometer.
- the ion group is first introduced into the separation space and mass-separated by the mass analyzer, and a part of the separated ion species to be measured is detected by the ion detector, but the rest is the flight space. It is preferable that the mass spectrometer is continuously analyzed by the time-of-flight mass spectrometer.
- the mass spectrometer of the present invention is The mass analyzer has a period substantially the same as that of the one-dimensional high-frequency electric field (hereinafter referred to as a y-direction high-frequency electric field), a phase is substantially (1/4) different from the period, and an acting direction is the ion group.
- the ion detector includes means for detecting ions flying to a predetermined position in the x direction on the exit surface;
- the ion group is introduced into the separation space at or just before the rise of the y-direction high-frequency electric field, and the n is 1.
- An ion group different from this is introduced into the separation space in a pulsed manner immediately before or immediately before the rising of the x-direction high-frequency electric field, and the ion species to be measured having a predetermined mass-to-charge ratio in the ion group is
- An x-direction high-frequency electric field is applied for one period or a period that is substantially equivalent to the period, and is emitted from the separation space, and is detected separately from other ion species based on the x-direction flying position on the emission surface.
- a mass spectrometer Preferably a mass spectrometer.
- the waveform of the one-dimensional high-frequency electric field is a rectangular wave, sine wave (or cosine wave), step wave, trapezoidal wave, triangular wave, sawtooth wave, or a waveform obtained by modifying a part thereof, or a plurality of these waveforms are synthesized. It is good to have a waveform.
- mass scanning by fixing the period of the one-dimensional high-frequency electric field and changing the acceleration voltage.
- the ion detector includes an ion detector that detects an ion species having a mass to charge ratio larger than that of the ion species to be measured together with the ion species to be measured or separately from the ion species to be measured. Good.
- FIG. 1 is a schematic diagram showing a configuration of a mass spectrometer 10 based on the first embodiment.
- the mass spectrometer 10 includes an ion source 1, an ion introduction unit 2, a mass analysis unit 3, an ion detection unit 4, and the like, and at least the mass analysis unit 3 and the ion passages around it are under high vacuum.
- the ion source 1 includes means for ionizing a sample and means for introducing a pulsed ion group into the mass analysis unit with a predetermined acceleration voltage.
- the ionization method is not particularly limited, and various methods are appropriately used depending on the purpose of mass spectrometry, the properties of the sample, and the like. Specifically, electron ionization, chemical ionization, field ionization or field desorption ionization, fast atom bombardment ionization, matrix-assisted laser desorption ionization, electrospray ionization, and the like are used as ionization methods.
- the ion source 1 may be a collision chamber that generates fragment ions from parent ions by collision-induced dissociation or the like.
- the mass analysis unit 3 is, for example, a final mass analysis unit in a tandem mass spectrometer.
- the pulsing method may be a method in which the sample is ionized in a pulsed manner, or a method in which the sample is ionized continuously while an ion group is extracted in a pulsed manner.
- the ion group is introduced into the mass analyzer 3 as a pulse synchronized with the phase of the one-dimensional high-frequency electric field.
- the ion introducing unit 2 is a means for converging the flight direction of the ion group (electrostatic lens 17 or the like) and / or a means for selecting and taking out the ion group flying in a predetermined direction (a shield having a pore such as a slit). And the like, and adapted to the characteristics of the ion source 1 and the mass analysis unit 3.
- the mass spectrometric unit 3 includes a separation space 5 for flying the introduced ion group and means for forming a one-dimensional high-frequency electric field in the separation space 5.
- the one-dimensional high-frequency electric field acts in a direction (y direction to be described later) intersecting the incident direction of the ion group, displaces each ion in the y direction, and causes the ion species having different mass-to-charge ratios to fly different flight paths.
- the ion detector 4 is disposed between the ion detector and the exit surface 9 and the ion detector, and selectively or semi-selectively passes a shield member (such as a slit) that passes ions flying in a predetermined y-direction position. And a signal processing unit for amplifying and storing a signal from the ion detector.
- the ion detection unit 4 detects the ion species to be measured by distinguishing from other ion species based on the y-direction flying position on the emission surface 9. This y-direction flying position corresponds to the amount of displacement that occurs while ions fly through the separation space 5.
- the feature of the mass spectrometer 10 is that it has a mass analyzer 3 as a mass analyzer and has an ion source 1, an ion introduction unit 2, and an ion detector 4 that are suitable for the mass analyzer 3. This will be described in more detail below.
- FIG. 2 is a perspective view (A) showing the structure of the mass analyzer 3 and a schematic view (B) showing a cross-sectional shape of the mass analyzer 3 cut along a plane orthogonal to the length direction.
- the separation space 5 has a rectangular parallelepiped shape, and two electrodes 6 and 7 are arranged on the upper and lower sides thereof.
- the main surfaces 6a and 7a on the separation space 5 side of both electrodes are flat and arranged in parallel to each other.
- the electrodes 6 and 7 are rectangular plate electrodes having the same length and the same width, and are arranged so that the positions of both ends are aligned in the length direction and the width direction. .
- the two end faces 8 and 9 in the length direction of the separation space 5 are used for ion incidence and emission, respectively.
- the entrance surface 8 and the exit surface 9 are virtual boundary surfaces between the separation space 5 in which the one-dimensional high-frequency electric field is formed and the external space in which the one-dimensional high-frequency electric field is not formed.
- the boundary between the separation space 5 and the external space is not a plane but a boundary region, and an edge field (fringe field) is formed in the boundary region.
- the ion species to be measured has little or no influence of the edge field by appropriately selecting the phase of the one-dimensional high-frequency electric field when introducing the ion group into the separation space 5. It can be made not to receive.
- the plane including the end surface of the electrodes 6 and 7 on the ion source 1 side is the incident surface 8, and the ion detection of the electrodes 6 and 7 is performed.
- a plane including the end surface on the part 4 side is the emission surface 9.
- an orthogonal coordinate system representing the position of ions in the separation space 5 is determined as follows. That is, on a plane that bisects the separation space 5 to the left and right, a straight line parallel to the main surface 7a of the electrode 7 is taken in the vicinity thereof, and this is defined as the z axis.
- the intersection of the z axis and the incident surface 8 is the origin O (0, 0, 0)
- the y axis is taken from the origin O in a direction perpendicular to the principal surfaces of both electrodes, and in the direction perpendicular to the y axis and the z axis. Take the x-axis.
- the exit surface 9 is an xy plane at the end of the separation space 5.
- a straight line indicating the incident direction of the ion group is referred to as a reference line 11.
- the ion group is introduced into the separation space 5 perpendicular to the incident surface 8 at the origin O.
- the reference line 11 coincides with the z axis.
- the effective length L of the separation space 5 is the length of the section in which the ion group is subjected to the action of the one-dimensional high-frequency electric field, that is, the length of the reference line 11 from the incident position to the exit surface 9. As shown in FIG. 1, it is effective when the position of the end of the ion introduction portion 2 coincides with the position of the incident surface 8 in the length direction or is closer to the ion source 1 than that at normal incidence.
- the length L is the length from the incident surface 8 to the exit surface 9 (length of the separation space 5) Lz .
- the effective length L is from the end of the ion introduction part 2 to the exit surface 9. Is the length.
- the high-frequency electric field is an AC electric field in which the impulse that ions receive from the electric field during one period is 0, and the period is 2 ms or less.
- the waveform is arbitrary, a rectangular wave high frequency electric field is most preferable.
- the following (1) to (3) can be cited as advantages of using the rectangular wave high-frequency electric field.
- the high frequency power source can be manufactured.
- the output voltage of the DC stabilized power supply can be applied between the electrodes with almost the same magnitude.
- FIG. 3A is a graph showing a normal rectangular wave high-frequency electric field without a rest period.
- the intensity of the rectangular wave high-frequency electric field is E
- the period is T
- the origin of the time axis is taken at the rise of the electric field
- the time is represented by t
- the phase of the rectangular high-frequency electric field at the time of ion incidence is represented by the time Ti at the time of incidence measured from the rise of the electric field.
- the incident direction of the ion group only needs to intersect the direction of the electric field, and does not necessarily need to be orthogonal to the xy plane.
- the position of each ion in the y direction is the same as in the case of normal incidence, it is not necessary to pay special attention to the oblique displacement with respect to the displacement in the y direction.
- Equation (8) shows that the magnitude of Y varies depending on the phase Ti of the rectangular high-frequency electric field at the time of ion incidence.
- a constant displacement Y can be obtained.
- This displacement amount Y is inversely proportional to the mass-to-charge ratio.
- FIG. 3B is a graph showing the relationship between the elapsed time t ⁇ t 0 and the ion displacement y at the time from the incident to the remainder of one cycle (11 ⁇ s).
- the period T of the rectangular high-frequency electric field is 10 ⁇ s
- the intensity E is 2546 Vm ⁇ 1. Went about.
- the numerical integration of the equations of motion described later was all performed by the same Runge-Kutta method.
- FIG. 3B shows an example in which the phase Ti of the rectangular high-frequency electric field at the time of ion incidence is variously changed.
- Ti was set to ⁇ T / 8, 0, T / 8, and T / 4 (y value when Ti is 3T / 8 ⁇ Ti ⁇ 7T / 8 is different from Ti by half period ⁇ T / 8 ⁇ Ti)
- ⁇ It is a value obtained by reversing the sign of the y value in the case of 3T / 8. Since the substantial contents are the same, the illustration is omitted in these cases.
- Y is 0 when Ti is T / 4 or 3T / 4. This is because the displacement in the positive direction and the displacement in the negative direction due to the action of the rectangular wave high-frequency electric field just cancel each other after one cycle. This relationship is used in the mass spectrometer 40 described later in the fourth embodiment.
- each ion introduced into the separation space 5 is displaced in the y direction by the force received from the one-dimensional high-frequency electric field.
- the displacement velocity v y is inversely proportional to the mass-to-charge ratio of the ions.
- the displacement of ions in an alternating electric field is different from the constant acceleration motion in an electrostatic field.
- ion species having different mass-to-charge ratios fly on different flight paths and are spatially separated (see FIG. 6 described later).
- This mass separation is performed based on the difference in mass to charge ratio itself due to the above displacement.
- the movement of ions in the extraction direction (z direction) is not involved in this displacement. Therefore, unlike mass separation in a sector magnetic field type mass analysis unit or a TOF type mass analysis unit, the ion group is hardly affected by variations in the initial state in principle.
- the first method is a method in which the ion species to be measured is emitted from the separation space 5 at the time when the action of the one-dimensional high-frequency electric field is received for one period or a period substantially regarded as equivalent thereto.
- the second method is a method of providing a rest period before and after one cycle in which the electric field strength is zero.
- the first method will be described by taking the case where the one-dimensional high-frequency electric field is a sine wave high-frequency electric field as an example
- the second method will be described by taking the case where the one-dimensional high-frequency electric field is a rectangular wave high-frequency electric field as an example.
- the phase of the sinusoidal high-frequency electric field at the time of ion incidence is most preferably 0 or ⁇ . Since both are substantially the same except that the y value is reversed, only the case where the phase is 0 will be described below.
- expression (11) Y z i eE S T 2 / 2 ⁇ m ⁇ (12) It becomes.
- FIG. 4 is a graph showing the relationship between the position of ions in the z direction and the amount of displacement y at the time from the start of the sine wave high-frequency electric field to the remainder of one period (11 ⁇ s). This figure is a graph showing the result of numerical calculation that the first method can suppress a decrease in mass resolution due to the spread of stay time.
- FIG. 4 (A) when the same ion as in the example shown in FIG. 3 (B) is a monovalent mass 100u, 10 [mu] s period T of the sine-wave high-frequency electric field, 4000Vm -1 their strength E S, And the result obtained by numerically integrating the above equation of motion is shown for an example in which the acceleration voltage U is 100V.
- a curve A 0 (thick line) indicates a flight path in which a monovalent ion 100 a having a mass of 100 u flies in the z direction with standard kinetic energy z i eU.
- Curves A ⁇ 10 and A +10 show the flight paths in which ion A flies in the z direction with 10% less kinetic energy and 10% greater kinetic energy than the standard, respectively.
- a flight path B 0 thin line in which a monovalent ion B (mass 103u) whose mass is 3% larger than that of the ion A flies in the z direction with standard kinetic energy is calculated in the same manner. The results are also shown.
- FIG. 4B shows a point (z ⁇ 138.91 mm, y ⁇ 61.42 mm) after one cycle of the curve A 0 as a reference point, and the z-direction position and the displacement amount y depending on the differences ⁇ z and ⁇ y from the reference point. It is a graph which shows. Note that ⁇ z and ⁇ y are respectively shown to be enlarged two times and twenty times as compared with FIG. Curves A 0 , A ⁇ 10 and A +10 indicate a range in which the time after incidence is 7.8 to 11.3 ⁇ s, and curve B 0 indicates a range in which the time after incidence is 8.3 to 11.9 ⁇ s. ing.
- the z-direction position of the ions is given by (2z i eU / m) 1/2 (t ⁇ t 0 ) as shown in equation (5).
- the z-direction position of the ions at the same time t ⁇ t 0 after the incidence is not the same even for the same ion species, and the z-direction position is the same as the standard position.
- the deviations of the curves A ⁇ 10 and A +10 from the curve A 0 in the z direction show examples of the lower limit and the upper limit of the spread, respectively.
- curves A 0 and A ⁇ 10 indicating the flight path of the ion A are obtained at the time when one cycle has passed after the ions have entered the separation space 5 and in the time domain before and after that. And A +10 all overlap approximately one and completely separate from the curve B 0 which shows the standard flight path of ion B.
- the ion species to be measured is mass-separated with high mass resolution compared to the case where the initial state is less influenced by the variation in the initial state.
- Standard ions are emitted from the separation space 5 after one cycle, and ions of other ion species to be measured are emitted before and after that.
- T L0 T (14) It is.
- ⁇ Second method> In the second method, as shown in FIG. 3C, a rest period in which the electric field strength is zero is provided before and after one cycle of the rectangular wave high-frequency electric field, and the ion group is separated into the separation space 5 during the rest period.
- the ion species to be measured is subjected to the action of the rectangular wave high-frequency electric field for one period, and is then emitted from the separation space 5 during the rest period after one period.
- FIG. 5 is a graph showing the relationship between the position of ions in the z direction and the amount of displacement y at the time from the start of the action of the rectangular wave high-frequency electric field having a rest period to the remainder of one cycle (11 ⁇ s).
- This figure is a graph showing the result of numerical calculation that the second method can completely prevent a decrease in mass resolution due to an increase in residence time.
- FIG. 5 shows that the period T of the rectangular high-frequency electric field is 10 ⁇ s, the intensity E is 2546 Vm ⁇ 1 , and the acceleration voltage U is 100 V when the ions are monovalent and have a mass of 100 u as in the example shown in FIG.
- the result obtained by numerically integrating the equation of motion (6) is shown.
- the description of the curves A 0 , A ⁇ 10 , A +10 , and B 0 is the same as in FIG.
- FIG. 5B similarly to FIG. 4B, a point (z ⁇ 138.91 mm, y ⁇ 61.42 mm) after one cycle of the curve A 0 is used as a reference point, and differences ⁇ z and ⁇ y from the reference point are used.
- Is a graph showing the z-direction position and the displacement amount y, and ⁇ z and ⁇ y are respectively enlarged by 2 times and 20 times compared to FIG.
- Curves A 0 , A ⁇ 10 and A +10 indicate a range in which the time after incidence is 8.2 to 11.3 ⁇ s
- curve B 0 indicates a range in which the time after incidence is 8.6 to 11.3 ⁇ s. ing.
- the other is that even if the time during which the ions A stay in the separation space 5 is wide, it only causes the length of time that the ions A stay in the separation space 5 during the rest period.
- the displacement in the y direction stops when one cycle has elapsed, and the stopped state is maintained during the pause period. Therefore, the length of the stay time in the pause period does not cause the displacement amount to expand in the y direction.
- the ion group is introduced into the separation space 5 during the rest period and the ion species to be measured are emitted from the separation space 5 during the rest period, the ion species to be measured are affected by the edge field. There is no. Further, since the ion species to be measured flies out in parallel with the reference line, the degree of freedom in the z-direction position where the slit and the ion detector are arranged is remarkably increased.
- the first and second methods it is less affected by variations in the initial state, and it is less necessary to increase the acceleration voltage in order to achieve high mass resolution. As a result, the size of the apparatus is hardly increased.
- the curves A 0 , A ⁇ 10 and A +10 do not completely overlap one point, which limits the mass resolution.
- the one-dimensional high-frequency electric field is a rectangular high-frequency electric field
- the first method is not as effective as in the case of a sine-wave high-frequency electric field. This is because, in a rectangular wave high-frequency electric field, the electric field strength instantaneously changes between rising and falling, and there is no time domain in which the electric field strength is near zero.
- the one-dimensional high-frequency electric field is a rectangular wave high-frequency electric field and the second method is used. Even when a one-dimensional high-frequency electric field other than a rectangular wave, for example, a sinusoidal high-frequency electric field is used, the same effect can be obtained by providing a rest period. However, since a circuit for realizing this is complicated, a rectangular wave high-frequency electric field is most preferable as a one-dimensional high-frequency electric field for providing a rest period.
- the time required for the measured ionic species ions pass the effective length L of the separation space 5 T L Distant, of which, T L0 and T L standard ion far.
- T P is the time to the beginning of one period from the time that is introduced ion groups
- T 0 is the length of the rest period after a period. In this paper, the period T does not include the length of the pause period.
- Equation (16) is expressed as T P + T + T E ⁇ T L0 ⁇ T P + T ⁇ T E + T 0 (17) It becomes.
- equation (13) the following equation: T P + T + T E ⁇ L (m / 2z i eU) 1/2 ⁇ T P + T + T 0 ⁇ T E (18) Is obtained.
- T D the duration of the ion lens pulse. If the ionization is pulsed effected, usually, T D is short. If T D is negligibly short in comparison with the T, since no time width T P, T 0 may be longer than 2T E from Equation (16). In contrast, and the like if the ionization is performed continuously, when the ion groups are drawn as the length of the pulse can not be ignored compared to T, the same time width as T D occurs in T P. In this case, T 0 needs to be longer than (T D + 2T E ).
- T D may be of any length. However, the need to increase the L accordingly when T D is longer occurs, the length of T D is practical limit. On the other hand, if T D is short, the amount of ions that can be introduced in a single group of ions pulses decreases. Therefore T D should appropriately determined in consideration of both.
- T P is required to be greater than zero at the end of the group of ions pulses, but not limited other than this. Once you have a T P slightly larger than this, there is an advantage that no inconvenience if it is within range even in this increase occurs is shifted to the time at which the ion groups are introduced. However, T P is the need to occur longer L accordingly large.
- T P and T 0 is the better the length of the minimum necessary. That is, T P and T 0 are T P ⁇ 0 to T D (19) T 0 ⁇ T D + 2T E (20) It should be slightly larger than the right side.
- T P and T 0 are T P ⁇ 0 to T D (19) T 0 ⁇ T D + 2T E (20) It should be slightly larger than the right side.
- the ion having the shortest residence time was introduced from the separation space 5 immediately after the start of the rest period and at the end of the ion group pulse.
- the acceleration voltage U, the period T of the one-dimensional high-frequency electric field, and the equation (18), more specifically, for example, the equation (21) are satisfied with respect to the mass-to-charge ratio of the ion species to be measured.
- the effective length L of the separation space 5 is selected. L satisfying Expression (18) is longer than L satisfying Expression (15) by the amount by which ( TP + T E ) is added to T if U and T are the same. Further, U satisfying Expression (18) is smaller than U satisfying Expression (15) if L and T are the same.
- the ion detector 4 is configured to detect ions flying from the intersection (0, 0) between the reference line 11 and the exit surface 9 to a position separated by a distance C in the y direction on the exit surface (described later). (See also [Ion detection section].)
- the ion species to be measured fly on the exit surface after receiving the action of the one-dimensional high-frequency electric field for one period.
- the high-frequency electric field displaces the ion species to be measured by a distance Y in the y direction during this one period.
- the ion detector 4 can detect the ion species to be measured by distinguishing from other ion species based on the y-direction position of the ions flying on the exit surface.
- the one-dimensional high-frequency electric field is a rectangular wave high-frequency electric field
- the following equation C z i eET 2 / 4m (23) is obtained from the equations (22) and (9). Is obtained.
- the period T and the intensity E of the rectangular wave high-frequency electric field are selected so that the equation (23) is satisfied with respect to the mass-to-charge ratio of the ion species to be measured. If T is the same, E satisfying the equation (23) is proportional to the mass-to-charge ratio of the ion species to be measured.
- Mass scanning In mass scanning, a plurality of ion species having different mass-to-charge ratios are detected in time series as ion species to be measured. In mass scanning, a range of a predetermined mass-to-charge ratio is continuously scanned, and all ion species within the range are detected in the order of the mass-to-charge ratio to obtain a mass spectrum. There is a selection (switching) scan in which several different ion species are switched and successively detected. In selective scanning, the amount of ions of several ion species having a specific mass-to-charge ratio can be repeatedly measured in a short time.
- the formula (16) or (18) with respect to the change in the mass-to-charge ratio of the ion species to be measured at a given L More specifically, for example, the acceleration voltage U or the period T of the rectangular high-frequency electric field is changed so that the formula (21) is satisfied.
- a wider mass-to-charge ratio range can be scanned than when scanning alone.
- the first mass scanning method In the first mass scanning method, the period T is fixed, the acceleration voltage U is changed according to the mass-to-charge ratio of each measured ion species to be scanned, and each measured ion species is sequentially expressed by the formula (16) or (18). To satisfy. More specifically, for example, U is changed in proportion to the mass-to-charge ratio of each ion species to be measured, and scanning is performed so that TL0 of each ion species to be measured sequentially becomes a predetermined constant value. In this way, the equation (21) is initially satisfied, and if there is no significant increase in TE thereafter, each ion species to be measured automatically satisfies the equation (21) even during scanning. The operation of the device is simplified.
- a single ion detector In normal scanning, a single ion detector usually detects a plurality of ion species in time series, so the distance C is constant.
- the intensity E of the rectangular high-frequency electric field is also changed so as to be proportional to the mass-to-charge ratio so that each ion species to be measured sequentially satisfies the equation (23) as the scanning progresses.
- U and E are proportional to the mass-to-charge ratio, so that it is easy to determine the mass-to-charge ratio of the ion species to be measured from the peak position of the mass spectrum. If the range of mass-to-charge ratio to be scanned is wide, and when U and E are partly under or over-exposed when scanning continuously with a single T, the mass-to-charge ratio range is divided into a plurality of regions, A region with a small ratio is scanned with a short T fixed, and a region with a large mass-to-charge ratio is scanned with a long T fixed.
- the ion species to be measured finishes flying in the separation space 5 for one period and is distinguished from other ions by the difference in displacement, so that the ion species to be measured from one ion species to another ion species
- the switching of the measurement ion species is completed in one period of the rectangular wave high-frequency electric field, for example, about 10 ⁇ s. Therefore, the ion amounts of a plurality of ion species can be repeatedly measured in a short time.
- ⁇ Second mass scanning method> U is fixed, T is changed according to the mass-to-charge ratio of each ion species to be scanned, and each ion species satisfying the equation (16) is sequentially detected as the ion species to be measured. . More specifically, for example, T is changed so that the square T 2 of the period is proportional to the mass-to-charge ratio of each ion species to be measured. In this case, since U is fixed, TL0 of each ion species does not change. Then, when T is changed, TL0 satisfying the equation (17) changes for each T, so that each ion species having the corresponding TL0 is a measured ion species satisfying the equation (18). Sequentially detected.
- E is also fixed. If the range of mass-to-charge ratio to be scanned is wide, and if a part of T becomes too small or too large when continuously scanned with a single U and E, the mass-to-charge ratio range is divided into a plurality of regions. A region with a small ratio is scanned with a small U and E fixed, and a region with a large mass-to-charge ratio is scanned with a large U and E fixed. These are the same for both normal scanning and selective scanning.
- T 0 of the pause period it is preferable to change the length T 0 of the pause period in proportion to T for the following reason.
- the effective length L of the separation space 5 it is necessary to extended by time T D, the rate of increase substantially determined by the ratio T D / T of T D with respect to T. Therefore, the most efficient use of the effective length L, as maintain the T D / T in optimum constant value, it is preferable to proportional T D to T.
- T E is considered to be substantially proportional to T L0 and thus T. Therefore, assuming that T 0 satisfies the relationship of equation (20), it is natural to make T 0 proportional to T. In this way, if the equation (21) is satisfied at the beginning, each ion species to be measured automatically satisfies the equation (21) sequentially even during scanning, and the operation of the apparatus is simplified.
- FIG. 6 is a graph (A) showing the flight path of each ion species in the mass spectrometer 10 and a graph (B) showing the change when scanned by the first mass scanning method.
- FIG. 6 shows the result obtained by numerically integrating the equation of motion (6) for an example in which the ion species is monovalent and the masses are 50 u, 100 u, 200 u and 400 u, and the period T of the rectangular wave high frequency electric field is 10 ⁇ s. Show.
- the illustrated flight path is a flight path of ions flying in the z direction with standard kinetic energy z i eU, and is indicated by a thick line while being subjected to the action of a high-frequency electric field, and is indicated by a thin line during a rest period.
- T P and T 0 are the minimum necessary length, and the effective length L of the separation space 5 varies in the initial state so that all the ion species to be measured stay in the separation space 5 for at least one period.
- a length slightly longer than the length 138.9 mm obtained by substituting T, m of the ion species to be measured, and U to be described later into Expression (15) is set.
- FIG. 6A shows the flight path when the acceleration voltage U is 100 V and the intensity E of the rectangular wave high-frequency electric field is 2546 Vm ⁇ 1 .
- an ion species having a mass of 100 u flies as a standard by 138.9 mm in the z direction during one period. Thereafter, the ion species slightly fly in the z direction during the rest period and reach the exit surface 9. That is, an ion species having a mass of 100 u is subjected to the action of a high-frequency electric field for one period, and then is emitted from the separation space 5 as an ion species to be measured during a rest period.
- the displacement amount Y of this ion species is 61.42 mm, which is equal to C.
- an ion species whose mass is less than 100 u, for example 50 u reaches the exit surface 9 earlier than one cycle, and the displacement amount y at that time is larger than C (or the displacement amount y is too large and collides with the electrode. And does not reach the exit surface 9).
- ion species having a mass exceeding 100 u, for example, 200 u or 400 u arrive at the emission surface 9 after receiving the action of the high-frequency electric field for longer than one period, and the displacement y at that time is smaller than C.
- the displacement amount Y after one cycle of the ion species having a mass of 200 u is C / 2. Further, an ion species having a mass of 400 u requires an excess of 20 ⁇ s (two cycles) to pass through the separation space 5, and the displacement amount on the exit surface 9 is C / 2.
- FIG. 6B shows the flight path when U is 200V and E is 5092Vm- 1 .
- the speed in the z direction is 21/2 times for all ion species as compared to the flight path of FIG. 6A (see equation (4)). It quickly reaches the exit surface 9.
- ion species having a mass of 100 u are emitted from the separation space 5 before being subjected to the action of the high-frequency electric field for one period.
- an ion species having a mass of 200 u having a mass of 2 times and a z-direction velocity of (1/2) 1/2 times has been subjected to the action of a high-frequency electric field for one period, and then has a rest period. In the meantime, it is emitted from the separation space 5 as the ion species to be measured.
- E since E is doubled, the amount of displacement Y that occurs during one cycle is doubled (see equation (9)).
- the displacement amount Y of the ion species having a mass of 200 u is equal to C.
- the displacement amount y when the ion species having a mass of 100 u reaches the exit surface 9 is larger than C, and the displacement amount y when the ion species having a mass of 400 u reaches the exit surface 9 is smaller than C. Accordingly, only the ion species to be measured having a mass of 200 u is detected by the ion detector 4.
- the ion source 1 may be a normal ion source or an orthogonal acceleration ion source.
- the ion source 1 is an orthogonal acceleration type ion source, the position of the ions flying on the emission surface 9 extends linearly, but if this direction is taken in the x direction, it is orthogonal without impairing the mass resolution in the y direction.
- An accelerated ion source can be used.
- the orthogonal acceleration type ion source in an ion source in which ionization of a sample is continuously performed with respect to time, a part of an ion group generated during an intermittent extraction period can be used, so that an ion utilization rate is improved.
- the ion utilization rate refers to the ratio of ions detected by the ion detector among the ions of the ion species to be measured generated in the ion source.
- the ion introduction unit 2 includes a converging means such as an electrostatic lens 17.
- a converging means such as an electrostatic lens 17.
- the electrostatic lens 17 is preferably configured such that the convergence of the ion species to be measured is the best in the ion detector 4.
- FIG. 1 shows an example in which the ion introduction part 2 is arranged on the downstream side of the ion source 1, but the arrangement of both is not limited to this.
- the distinction between the ion source 1 and the ion introduction part 2 is conceptual and functional, and is not a division in arrangement. In fact, both are often arranged in one piece. This is the case, for example, when an electrostatic lens is incorporated in an orthogonal acceleration ion source so that the flow of ions before orthogonal extraction is converged.
- FIG. 7A-1 is a schematic diagram showing an example of the ion detector 4.
- the ion detector is provided with an ion detector 13 and a slit 12 disposed between the emission surface 9 and the ion detector 13.
- the slit 12 is an example of a shielding member that selectively allows the ion species to be measured to pass, and the size of the gap between the upper slit 12a and the lower slit 12b can be changed.
- the center of the gap is at a position away from the reference line 11 by C in the y direction.
- the size of the gap is selected according to the required mass resolution or the like, and is, for example, about 0.05 to 0.5 mm.
- the mass spectrometer 10 uses the slit 12 to keep the mass resolution relatively low, and the high sensitivity measurement that gives priority to the transmittance of the ion species to be measured, although the transmittance of the ion species to be measured is low, is high. It is also possible to cope with high-resolution measurement that provides mass resolution.
- the ion detector 13 only needs to be capable of detecting ions flying through the slit 12, and an appropriate one may be selected according to the configuration of the ion detector 4.
- an ion detector having a narrow ion detection region can be used as the ion detector 13.
- a secondary electron multiplier having a small opening, a channel electron multiplier, a Faraday cup, and the like can be used as the ion detector 13.
- the width of the ion detection region needs to correspond to the spread.
- a secondary electron multiplier tube As the ion detector 13, a secondary electron multiplier tube, a channel electron multiplier tube, a microchannel plate, a Faraday cup, and the like having an appropriately sized opening are used. In any case, a post-acceleration detector or a conversion dynode can be used for the purpose of stabilizing the detection sensitivity.
- FIG. 7A-2 is a conceptual diagram of a mass spectrum obtained when scanning is performed by the first mass scanning method using the above-described ion detector.
- the ion species to be measured are scanned in order from the ion species having the smallest mass to charge ratio, and the detected ions corresponding to the abundance of each ion species A quantity peak is observed.
- U and E are proportional to the mass-to-charge ratio, it is easy to determine the mass-to-charge ratio of the ion species to be measured from the peak position of the mass spectrum.
- FIG. 7 (B-1) is a schematic diagram showing another example of the ion detector 4.
- the ion detector is provided with an ion detector 15 and a shielding plate 14 disposed between the emission surface 9 and the ion detector 15.
- the shielding plate 14 is an example of a shielding member that allows the ion species to be measured to be semi-selectively passed.
- An ion species having a mass to charge ratio smaller than that of the ion species to be measured is not allowed to pass, but the ion species to be measured and the mass to charge ratio thereof are less than that. Large ionic species are allowed to pass through.
- FIG. 7 (B-2) is a conceptual diagram of a mass spectrum obtained when mass scanning is performed by the first mass scanning method using this ion detector.
- U and E are small, all ion species emitted from the ion source 1 pass through the shielding plate 14 and are detected by the ion detector 15. Thereafter, when U and E are increased, the ion species having a smaller mass-to-charge ratio are sequentially blocked by the shielding plate 14 and removed from the ion species group detected by the ion detector 15.
- a stepped spectrum shown in FIG. 7B-2 is obtained.
- the position where the detected ion amount sharply decreases in this stepped spectrum is the position where the peak of the detected ion amount is observed in the normal mass spectrum.
- This ion detector has the following characteristics. (1) Since the amount of ions of all ion species emitted from the ion source 1 or the ion species to be measured and the ion species having a mass to charge ratio larger than that is measured, there is no oversight of high mass ions, and mass scanning is performed. The decision to abort is easy and accurate. (2) The ion amount of a predetermined ion species to be measured can be directly read as a difference between the detected ion amounts before and after the detection position of the ion species to be measured. In order to obtain the amount of ions in a normal mass spectrum, it is necessary to calculate the peak area by integrating the peaks of the ion species. This method is simpler and more accurate than this, and can simplify the data processing system. (3) If a normal mass spectrum is required, the stepped spectrum may be differentiated. Spectral differentiation is easier than integration.
- the ion detector 15 only needs to be capable of detecting ions flying through the shielding plate 14, and may select an appropriate one according to the configuration of the ion detector 4. However, in order for the above features to be fully exhibited, it is desirable that the ion detector 15 has a high linearity, that is, a capability of outputting an output signal proportional to the ion amount with respect to a wide range of ion amounts. Further, since the ion flying position is long in a line or in a strip shape, if the ions flying in this region are detected as they are, the ion detector 15 has a secondary electron multiplier having a long ion detection region corresponding to the flying position. , Channel electron multipliers, microchannel plates, and Faraday cups. In addition, if the ions are detected after being converged by an electrostatic field or the like, these detectors having a narrower ion detection region can be used.
- FIG. 7C is a schematic diagram showing still another example of the ion detector 4.
- a shielding plate 14 and an ion detector 16 are added to the slit 12 and the ion detector 13.
- FIG. 7C shows these arrangements in the z direction.
- the slit 12 and the ion detector 13 detect the ion species to be measured corresponding to both high sensitivity measurement and high resolution measurement.
- most of the ion species having a mass to charge ratio larger than that of the ion species to be measured are detected by the ion detector 16.
- the mass spectrum shown in FIG. 7A-2 is obtained from the ion detector 13, and the ion detector 16 from FIG. Almost the same mass spectrum as shown in 2) is obtained.
- this ion detector when this ion detector is used, scanning can be performed while constantly monitoring the total amount of ions emitted from the ion source 1 or the total amount of ion species having a mass to charge ratio larger than that of the ion species to be measured. Therefore, it is easy and accurate to determine whether to stop scanning.
- a highly sensitive ion detector can be used as the ion detector 13
- the ion species to be measured can be measured with high sensitivity.
- the configuration shown in FIG. 7B-1 since the ion detector is only the ion detector 15, high-sensitivity measurement of the ion species to be measured and measurement of the ion amount of many ion species It may be difficult to achieve both.
- the ion detector 16 may be the same as the ion detector 15. However, if it is used as a mere monitor, the ion detector 16 does not need to have as high linearity as the ion detector 15, so the options are wide.
- the anode is patterned on the microchannel plate, the detection surface is divided into a plurality of regions having different positions in the y direction, and each region is measured individually. You can also.
- the amount of ions of an ion species having a mass to charge ratio larger than that of the ion species to be measured can be measured in association with the position in the y direction, and information on not only the abundance of these ions but also the range of the mass to charge ratio can be obtained. Obtainable.
- FIG. 8A is a graph showing an example of a rectangular high-frequency electric field used for simultaneous analysis of ion species to be measured having a monovalent mass of 100 to 400 u.
- the ion group is introduced into the separation space 5 immediately before the high-frequency electric field rises.
- the time of ion incidence may be any time as long as it is in a rest period, but if it is incident immediately before, the effective length L of the separation space 5 can be used most efficiently and the time required for one analysis can be prolonged unnecessarily. Absent. For the same reason, in the rest period after one cycle, the ion species to be measured having a mass of 100 u is emitted from the separation space 5 soon after the start.
- the length T 0 of the rest period is set so that the ion species to be measured having a mass of 400 u is emitted from the separation space 5 by the end of the rest period. Specifically, the time required for the ion species to be measured having a mass of 400 u to pass through the separation space 5 is longer than the time required for the ion species to be measured having a mass of 100 u (more than 10 ⁇ s). In general, when T 0 is set slightly longer than T, ion species having a mass-to-charge ratio of up to 4 times can be analyzed simultaneously.
- FIG. 8B is a graph showing the flight path of each ion species when simultaneously analyzing a plurality of types of ion species to be measured using the rectangular wave high-frequency electric field.
- FIG. 8B shows an equation of motion for an example in which the ion species is monovalent and has a mass of 50 u, 100 u, 200 u, and 400 u, U is 100 V, T is 10 ⁇ s, and the high-frequency electric field strength E is 2546 Vm ⁇ 1. The result obtained by numerical integration of 6) is shown.
- the illustrated flight path is a flight path of ions flying in the z direction with standard kinetic energy z i eU, and is indicated by a thick line while being subjected to the action of a high-frequency electric field, and is indicated by a thin line during a rest period.
- the flight path of ion species having a mass of 100 u or less is the same as the flight path shown in FIG.
- the displacement Y of the ion species to be measured having a mass of 100 u is equal to C.
- the ion species to be measured having a mass of more than 100 u, for example 200 u or 400 u is subjected to the action of a high-frequency electric field for one period after being incident, and is displaced by Y in the y direction during this period. Since the displacement amount Y of each ion species is inversely proportional to the mass-to-charge ratio (see equation (9)), they are C / 2 and C / 4, respectively.
- these ion species to be measured fly over a relatively long distance parallel to the reference line 11 during the rest period, and reach the exit surface 9.
- illustration is omitted, an ion species having a mass of more than 400 u arrives at the emission surface 9 after receiving the action of the high-frequency electric field for longer than one period, and the displacement y at that time is smaller than C / 4.
- Example described above is an example, the upper limit of the ionic species of mass-to-charge ratios simultaneously analyzed by taking long quiescent period T 0, can be increased without limit in principle.
- the lower limit can be made as small as possible by reducing the acceleration voltage U or shortening the period T. Therefore, according to the mass spectrometer 10 described above, in principle, an almost complete mass spectrum can be obtained by introducing a pulsed ion group once, as in the TOF mass spectrometer. This is particularly effective when analyzing a single-shot phenomenon or a phenomenon with a low occurrence frequency, or using a pulsed ionization method such as a matrix-assisted laser desorption ionization method.
- the lower limit and upper limit of the mass-to-charge ratio to be measured can be freely set, it is not necessary to measure an area of an unnecessary mass-to-charge ratio, and the time required for one analysis is rarely prolonged. This is a characteristic that cannot be obtained with a TOF mass spectrometer.
- the relationship between the amount of ions among multiple ion species can be tracked correctly even for systems in which the composition of the sample changes at high speed, providing accurate and abundant information. Obtainable.
- the mass resolution is proportional to the displacement, it decreases in inverse proportion to the mass-to-charge ratio of the ion species to be measured.
- an ion detector that detects multiple types of ion species to be measured simultaneously, an ion detector that has a linear or belt-like ion detection region and can individually measure the amount of ions for each flying position, for example, A focal plane detector (array detector), a microchannel plate, or the like can be used.
- a focal plane detector array detector
- microchannel plate or the like
- the position resolution on the ion detection surface can be improved by arranging the ion detector so that the ion detection surface is inclined with respect to the y-axis.
- ions are detected and amplified by a microchannel plate, and as a result, an electron group emitted from the back surface of the plate is converted into a photon group by a fluorescent plate arranged on the back surface side. It is configured to be detected by a photodiode array or a CCD (Charge-Coupled Device) detector.
- the anode is patterned on the microchannel plate, the detection surface is divided into a plurality of areas according to the distance in the y direction from the reference line 11, and signals are individually received from each area. By taking out, the amount of ions can be individually measured.
- Equation (24) means that if the difference in ⁇ Y cannot be identified, the difference in mass of ⁇ m cannot be identified. Therefore, if ⁇ Y is the position resolution, that is, the minimum distance that can be detected by distinguishing the ions flying next to each other in the ion detector 4, Equation (24) gives the mass resolution of the mass spectrometer 10. It is considered to be a formula.
- the position resolution is determined by the spread of ion groups (ion beam diameter) in the ion detector 4, the gap width of the slit, the structure of the detection surface of the ion detector, and the like.
- the design of the mass spectrometer 10 is preferably performed in the following order, for example.
- the period T of the high frequency electric field is considered.
- T 10 ⁇ s It should be a degree.
- E corresponds to the mass range 1 to 200 u of the ion species to be measured.
- L y is assumed to be 100mm
- V y ⁇ 2.49 ⁇ 497V as the voltage V y of the high-frequency power source is required.
- the mass spectrometer 10 can easily realize a small-sized, lightweight, and inexpensive popular mass spectrometer. Such a mass spectrometer is useful as a gas analyzer, for example.
- the mass spectrometer 10 is also suitable for elementary analysis of high molecular weight substances. For example, when an ion species to be measured having a monovalent mass of 5000 u is analyzed with an acceleration voltage U of 200 V, a high-frequency electric field period T of 50 ⁇ s, and an intensity E of 4970 Vm ⁇ 1 , the displacement amount Y after that period is expressed by the equation From (9) Y ⁇ 60.0mm It becomes.
- the mass resolution is 300 as in the above-described example, and it is determined that the mass of the ion species to be measured is in the range of 5000 u ⁇ 17 u.
- this level of data is sufficient for the purpose of obtaining an approximate degree of polymerization of a high molecular weight substance. It is noteworthy that such useful data can be obtained from the simple mass spectrometer 10 described above.
- the quadrupole mass spectrometer has the disadvantage that the transmittance of ions with a large mass-to-charge ratio is low and ions whose mass-to-charge ratio exceeds the upper limit cannot be detected, and there is an oversight of high-mass ions. There is a concern that it may be.
- the mass spectrometer 10 in principle there is no limit on the range of mass to charge ratio that can be measured.
- the mass resolution may not be sufficient to separate each ionic species for an ionic species with a large mass-to-charge ratio, but even in such cases, the accuracy of the resulting mass-to-charge ratio is high, so what is the ionic species? There is or can be enough.
- the mass spectrometer 10 having the ion detector 15 or 16 shown in FIG. 7B or FIG. 7C the abundance of ion species having a mass to charge ratio larger than that of all ion species or the ion species to be measured is always grasped. Therefore, there is no oversight of high mass ions.
- the mass spectrometer 10 can repeatedly measure the amount of ions of a plurality of ion species having a specific mass-to-charge ratio in a short time by selective scanning. Therefore, even if the ionization conditions in the ion source 1 fluctuate, by calibrating based on the ion amount of the ion species as the internal standard, fluctuations other than fluctuations occurring during a short scanning time are corrected, and the accuracy of quantification is corrected. Is hard to be damaged.
- the relationship of the amount of ions among a plurality of ion species can be correctly traced even for a system in which the composition of the sample changes at a high speed, such as a fast chemical reaction system.
- the period T of the high-frequency electric field is considered.
- T 25 ⁇ s It should be a degree.
- E 414.6 to 20700 Vm ⁇ 1 from the equation (9).
- V y ⁇ 124.4 ⁇ 6219V a voltage V y of the high-frequency power source is required.
- the intensity E of the rectangular wave high-frequency electric field becomes too large or the acceleration voltage U becomes too small.
- the second mass scanning method is preferably used in combination. For example, in the above example, if the strength E of the high-frequency electric field is fixed to 414.6 Vm ⁇ 1 , the acceleration voltage U is fixed to 20 V, and the period T of the high-frequency electric field is changed between 5 and 25 ⁇ s, the mass is 1 per valence. It is possible to scan ⁇ 25u of ion species to be measured.
- the strength E of the high-frequency electric field is fixed to 20700 Vm ⁇ 1
- the acceleration voltage U is fixed to 1000 V
- the period T of the high-frequency electric field is changed between 25 to 50 ⁇ s
- the ions to be measured having a monovalent mass of 1250 to 5000 u Seeds can be scanned.
- a mass-to-charge ratio range of 1 to 5000 can be scanned almost continuously.
- the mass spectrometer 10 According to the mass spectrometer 10 described above, it is possible to easily realize a mass spectrometer having a relatively small size, light weight, and low cost. Furthermore, since the mass spectrometer 10 can simultaneously analyze a plurality of types of ion species to be measured, information on the plurality of types of ion species to be measured can be obtained simultaneously in one analysis and the ion utilization rate is improved.
- This mass spectrometer 10 is particularly suitable as a mass spectrometer constituting a GC-MS apparatus or an LC-MS apparatus.
- the amount of ions of a plurality of types of ion species to be measured can be repeatedly measured in a short time, and a chromatogram can be easily obtained. For this reason, even when a plurality of types of components flow out without being completely separated, the relationship between the components can be correctly grasped.
- an orthogonal acceleration ion source is used as the ion source 1
- the ion utilization rate in the mass spectrometer 10 is maximized, so that a highly sensitive GC-MS device and LC-MS device can be realized.
- the mass separation apparatus of the present invention includes, for example, an ion source 1, an ion introduction unit 2, a mass analysis unit 3, an ion selection unit, and the like.
- the passage is under high vacuum.
- the ion selection unit includes, for example, a shielding member having a pore (slit 12 or the like) as a means for taking out ions flying to a predetermined y-direction position on the emission surface 9 (see FIG. (See FIGS. 2 and 7).
- This mass separator has the same configuration as the mass spectrometer 10 except that the ion detector 4 is replaced with an ion selector.
- This mass separation device is less affected by variations in the initial state before the ion group of the ion source 1 is extracted, and the selected ion species having a predetermined mass-to-charge ratio is high from the ion group. Can be extracted with mass resolution. As a result, it is not necessary to increase the acceleration voltage in order to realize high mass resolution, the flight distance of ions is shortened, and the apparatus becomes smaller and lighter. In principle, there is no limit to the range of mass to charge ratios of selected ion species that can be handled. Furthermore, the selected ion species to be extracted can be switched at high speed.
- This mass separator is useful as a first-stage mass analyzer in a tandem mass spectrometer, a first-stage unit of an ion beam generator, or the like.
- FIG. 9A is a schematic diagram showing the configuration of a mass spectrometer 20A based on the second embodiment.
- the mass spectrometer 20A includes an ion source 1, an ion introduction unit 2, a first stage mass analysis unit 21, an intermediate mass analysis unit 22, a final stage mass analysis unit 23, a first stage ion detection unit 24, a final stage ion detection unit 25, and the like. Is done.
- ion group processing means 26 and 27 are provided between the mass analysis units.
- the ion group processing means 26 and 27 have an electrostatic lens or the like, and are provided for the purpose of improving the convergence of the ion group. Further, it has means for reaccelerating or decelerating the ion group, and is configured to change the velocity of the ion species to be measured incident on the subsequent mass analyzers 22 and 23 to an optimum velocity for each mass analyzer. Also good.
- the first stage mass analysis unit 21 is the same as the mass analysis unit 3 described in the first embodiment, and uses a rectangular wave high frequency electric field having a rest period as a high frequency electric field.
- the mass spectrometer 20 ⁇ / b> A the ion group introduced from the ion source 1 through the ion introduction unit 2 is first mass-separated by the first-stage mass analysis unit 21. Many of the separated ion species to be measured are detected by the first-stage ion detector 24 and simultaneously analyzed as described with reference to FIG.
- the first stage ion detector 24 is the same as the ion detector 4.
- the first-stage ion detector 24 includes an ion detector similar to the ion detector 16 and can measure the ion amount of an ion species having a mass to charge ratio larger than that of the ion species to be measured.
- ion species to be measured that have been mass-separated
- ion species that are required to be separated with particularly high mass resolution are introduced to the subsequent mass analyzers 22 and 23, and further mass-separated, and then the final-stage ion detector 25. Is detected.
- the first-stage ion detector 24 is provided with pores for extracting these ion species to the intermediate mass analyzer 22.
- the intermediate mass analyzer 22 and the final mass analyzer 23 are the same as the first mass analyzer 21. Ion species analyzed by the subsequent mass analyzers 22 and 23 move between the mass analyzers during the rest period of the rectangular wave high-frequency electric field. As a result, a plurality of mass analyzers are connected without reducing the mass resolution, and high mass resolution is achieved by stacking the displacement amounts Y of the mass analyzers.
- the displacement amount Y per stage is smaller than when a high resolution is achieved with a single-stage configuration.
- the distance between the electrodes is reduced, and the mass spectrometer is reduced in size as a whole.
- the intermediate mass analyzer 22 can be omitted or configured by a plurality of mass analyzers depending on the required mass resolution.
- the mass spectrometer 20A it is considered difficult to achieve a mass resolution of about 2500 in the first stage mass analyzer 21 and a mass resolution of about 7500 to 10,000 in the final stage mass analyzer 23.
- the entire length of the mass analyzers 21 to 23 is about 900 to 1000 mm, and the analysis time required for one analysis is about several tens of ⁇ s.
- a predetermined mass-to-charge ratio range can be measured with high mass resolution and a mass spectrum in a wide mass-to-charge ratio range can be efficiently acquired with a relatively small apparatus. it can.
- FIG. 9 (A) shows an example in which ion species having a small mass-to-charge ratio out of the ion species to be measured mass-separated by the first-stage mass analysis unit 21 are extracted to the subsequent mass analysis unit.
- the present invention is not limited to this, and an ion species having an intermediate mass-to-charge ratio can be taken out and further mass separated by a subsequent mass analysis unit. In this way, it is possible to analyze ion species in a predetermined mass-to-charge ratio range with high mass resolution while acquiring both mass spectra of the ion species to be measured on the low mass side and the high and low mass sides.
- ion species having a large mass-to-charge ratio can be taken out and further mass-separated by a subsequent mass analysis unit. In this way, it is possible to improve the mass resolution of the high-mass ion species whose mass resolution is low in a single mass analyzer. Thereby, it is possible to analyze ion species in a wide mass-to-charge ratio range with a high mass resolution with the same degree.
- FIG. 9B is a schematic diagram showing the configuration of another mass spectrometer 20B based on the second embodiment.
- the mass spectrometer 20B includes an ion source 1, an ion introduction unit 2, a first stage mass analysis unit 21, a final stage mass analysis unit 28, a first stage ion detection unit 24, a final stage ion detection unit 25, and the like. Further, an ion group processing means 29 is provided between the mass analyzers as necessary.
- the counter electrode of the final stage mass analyzer 28 is provided along the flight path of the ion species to be measured.
- the distance between the counter electrodes is not so large.
- the final stage mass analyzer 28 is reduced in size with respect to the displacement amount Y, and the high-frequency voltage applied between the counter electrodes is kept small.
- the high-frequency electric field acts in the y direction
- the high-frequency electric field component acting in the -z direction causes displacement in the -z direction. Note that it will be shorter.
- the length direction of the final stage mass analysis unit 28 is arranged to be inclined by 30 ° with respect to the z direction of the first stage mass analysis unit 21, assuming that the strength of the high-frequency electric field is Ed, (3 1/2 / 2)
- the electric field of Ed acts and the electric field of (1/2) Ed acts in the -z direction
- the displacement of (3 1/2 / 3) times the displacement in the y direction is -z direction Arises.
- the flight distance in the z direction is the same as that of the mass spectrometer which is not inclined when the period length is increased by 20 to 30%, for example. become.
- the strength of the high-frequency electric field required to cause a predetermined displacement in the y direction is reduced even with this increase in period.
- the mass analysis unit 3 may be arranged so that the length direction thereof is inclined with respect to the incident direction of the ions so that the ion group is obliquely incident on the separation space 5.
- the mass spectrometer described in claim 5 is combined with the time-of-flight mass spectrometer so that the separation space forms a part of the flight space of the time-of-flight mass spectrometer. An example will be described.
- FIG. 10 is a schematic diagram showing the configuration of the mass spectrometer 30 based on the third embodiment.
- the mass spectrometer 30 includes an ion source 1, an ion introduction unit 2, a mass analysis unit 3, an ion detection unit 4, a TOF unit 31, a reflectron 32, an ion detection unit 34, and the like.
- the ion group processing means 33 may be provided as needed.
- the ion group processing means 33 has an electrostatic lens or the like and is provided to improve the convergence of the ion group. Moreover, it has a means to reaccelerate the ion group, and may be configured to change the speed of the ion species that continues to fly in the TOF unit 31 to an optimum speed.
- a preferable condition when the ion group flies through the mass analysis unit 3 and a preferable condition when the ion group flies through the TOF unit 31 do not always coincide with each other.
- the ion group processing means 33 adjusts such a difference in conditions.
- the feature of the mass spectrometer 30 is that the separation space 5 of the mass analyzer 3 is arranged to share a part of the flight space of the TOF unit 31.
- the ion source 1, the ion introduction unit 2, the mass analysis unit 3, and the ion detection unit 4 constitute the mass spectrometer 10 described in the first embodiment.
- the ion source 1, the ion introduction unit 2, the TOF unit 31, the reflectron 32, the ion group processing means 33, and the ion detection unit 34 constitute a reflectron TOF mass spectrometer. In the mass spectrometer 30, both are united and arranged.
- the ion group is introduced from the ion source 1 into the separation space 5 through the ion introduction unit 2 and is mass-separated by the mass analysis unit 3.
- Many of the separated ion species to be measured are detected by the ion detector 4 and simultaneously analyzed as described with reference to FIG.
- ion species that are particularly required to be separated with high mass resolution continue to fly in the remaining flight space of the TOF unit 31 and are detected by the ion detection unit 34.
- FIG. 10 shows an example in which the flight path of ions in the TOF unit 31 is in the yz plane
- the reflectron 32 may be configured so that the flight path is in the xz plane.
- FIG. 10 shows an example in which an ion species having a small mass-to-charge ratio is extracted from the ion species to be measured and analyzed by a time-of-flight mass spectrometer.
- the present invention is not limited thereto, and an ion species having an intermediate or large mass-to-charge ratio is shown. Can be analyzed with a time-of-flight mass spectrometer. This is as described in the second embodiment.
- a predetermined mass-to-charge ratio range can be measured with high mass resolution, and a mass spectrum in a wide mass-to-charge ratio range can be efficiently acquired.
- the detection sensitivity is less likely to be lowered even when the highest level of mass resolution is achieved.
- the ion detection unit 34 may be replaced with an ion selection unit.
- the ion source 1, the ion introduction unit 2, the mass analysis unit 3, and the ion selection unit constitute the mass separation device of the present invention.
- FIG. 11A is a schematic diagram showing the configuration of the mass spectrometer 40 based on the fourth embodiment.
- the mass spectrometer 40 includes an ion source 1, an ion introduction unit 2, a mass analysis unit 43, an ion detection unit 44, and the like.
- FIG. 11B is a schematic diagram showing a cross-sectional shape of the mass spectrometer 43 cut along a plane orthogonal to the length direction.
- electrodes 46 to 49 similar to the electrodes 6 and 7 shown in FIG. 2 are arranged above and below the separation space 45 so that the main surface is orthogonal to the x-axis or y-axis.
- a high frequency voltage in the y direction is applied between the electrode 46 and the electrode 47
- a high frequency voltage in the x direction is applied between the electrode 48 and the electrode 49
- a high frequency electric field is formed in each of the y direction and the x direction.
- Both the two high-frequency electric fields are formed in the separation space 45, but conceptually function independently. This is possible because when the time of ion incidence is after (1/4) period or (3/4) period of the rise of the one-dimensional high-frequency electric field, the effect of the high-frequency electric field was received for one period. This is because the displacement speed and displacement amount of the ions at the time point become 0 (see Expression (8) and FIG. 3B). Therefore, in the mass spectrometer 40, it is easy to understand when it is considered that two mass analyzers are provided so as to share the separation space 45.
- FIG. 12 (A) is a graph showing an example of a high-frequency electric field used in the mass spectrometer 40.
- This high-frequency electric field is generated when the first ion group and the second ion group are introduced in pulses with different acceleration voltages at intervals of approximately (1/4) period.
- the high-frequency electric field enables analysis of one kind of ion species to be measured and simultaneous analysis of plural kinds of ion species to be measured in the second ion group.
- the mass of the second ion group is separated by the y-direction high frequency electric field.
- the y-direction electric field is essentially the same as the rectangular wave high-frequency electric field shown in FIG. 8 (A), and continues for one period from the rising edge before entering a rest period. The length of the rest period is determined based on the mass-to-charge ratio range of the ion species to be measured to be analyzed simultaneously. However, unlike the electric field shown in FIG. 8 (A), there is a (1/4) period in which the y-direction electric field acts before rising so as not to adversely affect the mass separation of the first ion group. .
- the second ion group is introduced in a pulse manner immediately before the rising of the y-direction high-frequency electric field.
- the mass of the first ion group is separated by the high frequency electric field in the x direction.
- the x-direction electric field has the same period T as the y-direction electric field, and the rising edge precedes the rising edge of the y-direction electric field by (1/4) period.
- the x-direction electric field rises from the rest period, and is combined with one period for mass separation of the first ion group and (1/4) period for not adversely affecting the mass separation of the second ion group. After another (1 + 1/4) cycle, the rest period starts again.
- the first ion group is introduced in a pulse manner immediately before the rising of the high frequency electric field in the x direction.
- FIG. 12B is a plan view showing the positions of ion species flying on the emission surface 50 of the mass analyzer 43.
- air position of the second group of ions, as well as the example shown in FIG. 8 y-direction high-frequency electric field period T is 10 ⁇ s, its strength E is 2546Vm -1, acceleration voltage U is 100V and the separated spaces, The calculation result about the case where the effective length L of 45 is more than 138.91 mm is shown.
- the flying position of the first ion group shows the calculation result when the strength of the high frequency electric field in the x direction is 2E (5092 Vm ⁇ 1 ) and the acceleration voltage U is slightly larger than 200V.
- the ion species to be measured having a monovalent mass of 100 to 400 u in the second ion group is subjected to the action of the electric field in the y direction for one period and displaced by Y in the y direction. After that, it is emitted from the separation space 45 during the rest period and is analyzed simultaneously.
- FIG. 12B the positions on the y axis where these measured ion species fly are shown in increments of 2u (y coordinates were calculated using equation (9)).
- the displacement amount Y of the ion species to be measured having a mass of 100 u is about 61.42 mm.
- the flying position of a monovalent ion species having a mass greater than 400 u is a position below the y-axis.
- the trajectory of a monovalent ion having a mass of 100 u on the xy coordinate during one period from the incidence is indicated by a thin solid line (the x coordinate and the y coordinate are the equations of motion (6
- the equation representing the high-frequency electric field was substituted into the equation of motion similar to that relating to the displacement amount x, and the equation of motion was obtained by numerical integration. Since the electric field also acts in the x direction, the locus in the middle is off the y axis, but the displacement amount x becomes zero after one cycle.
- the other ion species to be measured draw the same locus.
- the incident time of the second ion group is (1/4) cycle after the rising of the x-direction electric field. Further, the displacement speed in the x direction becomes 0 after one cycle, and this state is maintained during the rest period thereafter. Therefore, the x-direction electric field does not hinder mass separation of the ion species to be measured of the second ion group.
- the acceleration voltage U is set slightly larger than 200V.
- a monovalent ion species having a mass of 200 u is emitted from the separation space 45 as the ion species to be measured at the time when it receives the action of the x-direction electric field for one period or when it is considered to be substantially equivalent to that. . Therefore, if an ion detector similar to the above-described ion detector 13 is arranged at the flying position in the x direction, the mass resolution is hardly reduced due to variations in the initial state, and this ion species can be detected. .
- the displacement amount X after one cycle of this ion species is about 61.42 mm.
- the trajectory that the ion species to be measured follows on the xy coordinate during one period from the incidence is indicated by a thin solid line (this is the measurement in the second ion group described above). It was obtained in the same manner as the ion species trajectory.) Since the electric field also acts in the y direction, the midway trajectory deviates from the x axis, but the displacement y becomes zero after one cycle. This is because the incident time of the first ion group is (1/4) period before the rise of the y-direction electric field (corresponding to (3/4) period). Therefore, the y-direction electric field does not hinder the mass separation of the ion species to be measured. For reference, FIG.
- 12B also shows the center position where monovalent ions of mass 204 to 800 u in the first ion group fly in 4 u increments. These ion species are subjected to the action of the electric field in the y direction for the longest (1/4) period longer than one period, so that the flying position deviates from the x-axis.
- the displacement amount X of the ion species to be measured having the mass 200 u in the first ion group is the mass 100 u in the second ion group.
- the displacement amount Y of the ion species to be measured is halved, and the mass resolution is also halved. Therefore, in this example, the strength of the electric field in the x direction is set to twice the strength of the electric field in the y direction. In this way, the displacement amounts of the two ion species to be measured are the same, and both can be measured with the same mass resolution.
- FIG. 13 is a graph showing an example of a high frequency electric field obtained by slightly deforming the rectangular wave high frequency electric field shown in FIG.
- This y-direction electric field has a short rest period at the rise and fall, and the second ion group is introduced during the rest period at the rise. Therefore, the second ion group is not affected by the edge field.
- the length of the period in which the y-direction electric field acts is shortened by the rest period, it is necessary to slightly increase the strength of the y-direction electric field in order to obtain the same amount of displacement.
- the x-direction electric field has a short rest period between one period and the remaining (1/4) period, and the ion species to be measured is emitted during this rest period.
- the first ion group can simultaneously analyze a plurality of types of ion species to be measured.
- the ions to be measured are not affected by the edge field.
- this rest period exists, the displacement amount in the x direction when the ion species to be measured in the second ion group is emitted is not zero. Therefore, it is not preferable that the length of the suspension period is longer than necessary.
- the time during which the ion species to be measured in the first ion group and the second ion group stay in the separation space 45 needs to be a little longer in accordance with the rest period, so the acceleration voltage of each ion group Make it a little smaller.
- the mass-to-charge ratio of the ion species to be measured can be set independently for two pulsed ion groups with a slight time difference, and analysis can be performed with the same mass resolution. This time difference is approximately (1/4) period, and is a short time of about 2.5 ⁇ s.
- the second ion group can simultaneously analyze a plurality of types of ion species to be measured in an arbitrary mass-to-charge ratio range.
- the ion species to be measured that can be analyzed in the first ion group may be limited to one or several species, but the ion species used as the internal standard is the ion species to be measured, and the second ion species is determined based on the amount of ions. This is sufficient when calibrating the ion content of the ion species to be measured in the ion group.
- the mass spectrometer 40 can easily realize excellent quantitativeness.
- the present invention has been described based on the embodiment, but the present invention is not limited to these examples, and it is needless to say that the present invention can be appropriately changed without departing from the gist of the invention.
- the mass spectrometer and the mass separator of the present invention contribute to increasing the usefulness of the mass spectrometer and the mass separator in research and applications such as chemistry, physics, biology, and medicine, and further spreading.
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Abstract
Description
TOF型質量分析部では、イオン群はイオン源から所定の加速電圧Uでパルス的に引き出され、電場や磁場の存在しない長さLFの自由飛行空間に導入される。各イオンがこの空間を通過するのに要する時間TFは、イオンの飛行速度vから次式
TF=LF/v
で与えられるので、TOF型質量分析部は速度分析器として機能する。
扇形磁場型質量分析部では、イオン群はイオン源から所定の加速電圧Uで引き出され、運動エネルギーzieUを付与される。次にイオン群は一様な磁束密度Bをもつ扇形磁場中に、磁場に直交するように導入される。磁場中のイオンはローレンツ力によって飛行方向が偏向され続け、磁場に直交する円弧を描くように飛行する。イオンの飛行速度をvとすると、各イオンが描く円弧の半径Rは次式
R=mv/zieB
で与えられるので、扇形磁場型質量分析部は運動量分析器として機能する。
四重極型質量分析部では、同一形状の4本の棒状電極によって囲まれた細長い空間に四重極電場が形成され、この空間がイオンの通路として用いられる。イオン群は、長さ方向の一方の端部から中心線に沿うように導入され、電場から受ける力によって振動しながら、他方の端部へ向かって慣性飛行する。このとき、特定の質量電荷比をもつイオン種のみが電場に適合し、安定な振動運動を行いながら通路内を端部まで飛行することができる。他のイオンは振幅が大きくなり過ぎ、棒状電極に衝突するか、または棒状電極間のすき間から通路外へ飛び出すかして除かれる。
試料をイオン化する手段、およびパルス状のイオン群を所定の加速電圧で質量分析部 へ導入する手段を備えるイオン源と、
前記イオン群の飛行方向を収束させる手段、及び/又は所定の方向へ飛行する前記イ オン群を選択して取り出す手段を備えるイオン導入部と、
導入した前記イオン群を飛行させる分離空間、および前記イオン群の入射方向に所定 の角度で交差する方向(以下、y方向と呼ぶ。)に作用する一次元高周波電場を前記分 離空間に形成する手段を備え、前記一次元高周波電場の作用によって、質量電荷比が互 いに異なるイオン種に互いに異なる飛行路を飛行させる前記質量分析部と、
前記分離空間の末端の出射面上の所定のy方向位置に飛来するイオンを検出する手段 を備えるイオン検出部と
を少なくとも有し、前記イオン群は前記一次元高周波電場の位相に同期したパルスとして前記分離空間へ導入され、所定の質量電荷比を有する被測定イオン種が前記一次元高周波電場の作用をn周期間またはそれと実質的に同等とみなされる期間受けて前記分離空間から出射され、前記出射面上でのy方向飛来位置に基づいて他のイオン種と区別して検出される、質量分析装置に係わるものである(ただしnは自然数である。)
試料をイオン化する手段、およびパルス状のイオン群を所定の加速電圧で質量分析部 へ導入する手段を備えるイオン源と、
前記イオン群の飛行方向を収束させる手段、及び/又は所定の方向へ飛行する前記イ オン群を選択して取り出す手段を備えるイオン導入部と、
導入した前記イオン群を飛行させる分離空間、および前記イオン群の入射方向に所定 の角度で交差する方向(以下、y方向と呼ぶ。)に作用する一次元高周波電場を前記分 離空間に形成する手段を備え、前記一次元高周波電場の作用によって、質量電荷比が互 いに異なるイオン種に互いに異なる飛行路を飛行させる前記質量分析部と、
前記分離空間の末端の出射面上の所定のy方向位置に飛来するイオンを取り出す手段 を備えるイオン選択部と
を少なくとも有し、前記イオン群は前記一次元高周波電場の位相に同期したパルスとして前記分離空間へ導入され、所定の質量電荷比を有する被選択イオン種が前記一次元高周波電場の作用を1周期間またはそれと実質的に同等とみなされる期間受けて前記分離空間から出射され、前記出射面上でのy方向飛来位置に基づいて他のイオン種と区別して取り出される、質量分離装置に係わるものである。
T=L(m/2zieU)1/2
を満たし、前記イオン群は前記一次元高周波電場の強さが0である時点において前記分離空間へ導入され、前記被測定イオン種は実質的に1周期後の前記一次元高周波電場の強さが0である時点において前記分離空間から出射されるのがよい(ただし、ziはイオン種の電荷数であり、m、e、U、L、およびTは、それぞれ、SI単位で表されたイオン種の質量、電気素量、前記加速電圧、前記分離空間の有効長、および前記一次元高周波電場の周期である。なお、前記分離空間の有効長とは、前記イオン群が前記一次元高周波電場の作用を受ける区間の長さを言うものとする。)。上式は、被測定イオン種のイオンのうち、引き出し方向に標準の運動エネルギーzieUをもつイオンが前記分離空間の前記有効長を1周期間で通過するための条件である。その他のイオンはその前後に前記有効長を通過する。前記イオン群の入射時を上記のように限定すると、1周期間の変位量が最大になり、かつ前記被測定イオン種が端縁場(フリンジ・フィールド)の影響をほとんど受けない利点がある。
T+TP<TL<T+TP+T0
を満たし、前記イオン群は前記一周期の前の前記休止期間において前記分離空間へ導入され、前記被測定イオン種は前記一周期の後の前記休止期間において前記分離空間から出射されるのがよい(ただし、TL、TP、およびT0は、それぞれSI単位で表された、前記被測定イオン種のイオンが前記分離空間の前記有効長を通過するのに要する時間、前記イオン群が導入される時刻から前記一周期の始まりまでの時間、および前記一周期の後の前記休止期間の長さである。)。この場合、前記被測定イオン種のすべてのイオンが前記一次元高周波電場の作用を等しく前記一周期間受けるので、質量電荷比が同じイオン同士ではこの間の変位量は厳密に等しくなる。加えて、上記の条件を満たす前記被測定イオン種は複数が存在し得るので、前記休止期間の長さに応じた質量電荷比範囲の複数の前記被測定イオン種を同時分析することができる。
前記質量分析部が、前記一次元高周波電場(以下、y方向高周波電場と呼ぶ。)と周期が実質的に同じで位相が実質的に(1/4)周期異なり、作用する方向が前記イオン群の入射方向に所定の角度で交差し、かつy方向と直交する方向(以下、x方向と呼ぶ。)であるx方向高周波電場を前記分離空間に形成する手段を備え、
前記イオン検出部が、前記出射面上の所定のx方向位置に飛来するイオンを検出する手段を備え、
前記イオン群は前記y方向高周波電場の立ち上がり時またはその直前に前記分離空間に導入され、前記nは1であり、
これとは別のイオン群が前記x方向高周波電場の立ち上がり時またはその直前にパルス的に前記分離空間に導入され、このイオン群中の、所定の質量電荷比を有する被測定イオン種は、前記x方向高周波電場の作用を1周期間またはそれと実質的に同等とみなされる期間受けて前記分離空間から出射され、前記出射面上でのx方向飛来位置に基づいて他のイオン種と区別して検出される、質量分析装置であるのがよい。
実施の形態1では、請求項1~3および7~10に記載した、本発明の質量分析装置の例について説明する。なお、説明は主として通常最も好ましい場合、すなわちn=1で、被測定イオン種が一次元高周波電場の作用を1周期間またはそれと実質的に同等とみなされる期間受けた時点において分離空間から出射される場合について行う。説明に必要な場合、一次元高周波電場の例として主として矩形波高周波電場を用いる。また、請求項11に記載した、本発明の質量分離装置についても説明する。
図1は実施の形態1に基づく質量分析装置10の構成を示す概略図である。質量分析装置10はイオン源1、イオン導入部2、質量分析部3、およびイオン検出部4などからなり、少なくとも質量分析部3とその前後のイオンの通路は高真空下にある。
図2は質量分析部3の構造を示す斜視図(A)、および長さ方向に直交する面で質量分析部3を切断した断面形状を示す概略図(B)である。分離空間5は直方体形で、その上下には2つの電極6および7が対向して配置されている。両電極の分離空間5側の主面6aおよび7aは平坦であり、互いに平行に配置されている。典型的には、図2に示したように電極6および7は同じ長さおよび同じ幅を有する長方形の平板電極であり、長さ方向および幅方向において両端の位置が揃うように配置されている。
<一次元高周波電場>
図2(B)に示されているように、電極6および7は高周波電源に電気的に接続され、電極間に高周波電圧Vyが印加される。両電極の主面間の距離をLyとおくと、このときy方向に次式
Ey=-Vy/Ly・・・(1)
で表されるy方向電場Eyが形成される。なお、電極7はイオン導入部2の末端と同電位に保たれているものとする。
(1)直流定電圧電源、その出力電圧を電極6および7に印加するための配線とそれを開 閉するスイッチ回路、およびスイッチ回路を制御するタイマー回路によって、簡易か つ安価に、小型、軽量の高周波電源を作製することができる。
(2)直流安定化電源の出力電圧をほぼそのままの大きさで電極間に印加することができ る。したがって、発振回路などのアナログ回路によって高周波電圧を作り出す高周波 電源に比べて、はるかに効率よく、正確で高い電圧を電極間に印加することができる 。また、矩形波高周波電場では各半周期を通じて電場の強さが一定値(最大値)に保 たれるので、イオンを変位させる効率が最も高い。これらの結果、高周波電圧の大き さの限界によって質量分析装置の性能が制限されることが少ない。
(3)様々な時間間隔をもつ波形を、デジタルタイマー回路によって容易かつ正確に作り 出すことができる。このため電場の強さが0になる休止期間を設けることが容易であ る。また、高周波電場の周期を広い範囲で変化させることができるので、後述する第 2の質量走査方法を好適に利用することができる。
・0≦t<T/2のとき
Ey=E・・・(2)
・T/2≦t<Tのとき
Ey=-E・・・(2)
で表され、その後はこの繰り返しになる。なお、イオン入射時の矩形波高周波電場の位相は、電場の立ち上がり時から測った入射時の時刻Tiで表すものとする。
イオン群は原点Oにおいて分離空間5に導入されるものとし、分離空間5におけるイオンの位置を表す座標を(x,y,z)とする。また、イオンのx、yおよびz方向への速度をそれぞれvx、vyおよびvzとし、入射時の速度をそれぞれvx0、vy0およびvz0とする。イオン群が加速電圧Uによってイオン源1から引き出され、各イオンが運動エネルギーzieUをもつとすると、各イオンの入射時の速度vは次式
v=(2zieU/m)1/2・・・(3)
で与えられる。
vx0=0;vy0=0
vz0=v=(2zieU/m)1/2・・・(4)
である。分離空間5にx方向の電場は存在しないので、x方向における変位はない。また、z方向にも電場が存在しないので、vzはvz0で一定である。したがって、イオン群が分離空間5に入射した時刻をt0とすると、その後、時間t-t0が経過した時刻tにおける各イオン種のz方向位置は、次式
z=(2zieU/m)1/2(t-t0)・・・(5)
で与えられる。式(5)を満たす基準線11上の位置は、仮に一次元高周波電場が作用しないとした場合に各イオン種が占める位置であるので、基準位置と呼ぶことにする。実際にはy方向電場が作用するので、時刻tにおいて各イオン種はそれぞれ基準位置からy方向へ変位し、基準位置において基準線11に直交するy軸上にある。
d2y/dt2=dvy/dt=zieEy/m・・・(6)
で表される。以下、y座標上でのイオンの変位について検討する。
vy0=0
となり、各イオンのy方向位置は垂直入射の場合と同じになるので、y方向変位に関しては斜め入射であることに特別な注意をはらう必要がない。
特徴(I):
イオンが交流電場から受ける力積は1周期間で0になるので、y方向におけるイオンの変位速度vyは、1周期後に初速度にもどる。
vy=vy0・・・(7)
ここではvy0=0である場合を考えているので、
vy=dy/dt=0
となり、y方向におけるイオンの変位は停止する。
一次元高周波電場の作用を1周期間受けた時点でのy方向におけるイオンの変位量をYとおく。一次元高周波電場が矩形波高周波電場である場合、式(2)を式(6)に代入し、vy0=0としてイオン入射後の1周期間において運動方程式(6)を2度積分すると、矩形波高周波電場中でのYを表す式として次式
・0≦Ti≦T/2のとき
Y=zieET(T-4Ti)/4m・・・(8)
・T/2≦Ti≦Tのとき
Y=zieET(4Ti-3T)/4m・・・(8)
が得られる。式(8)には、イオン入射時の矩形波高周波電場の位相TiによってYの大きさが様々に変化することが示されている。これは、見方を変えれば、矩形波高周波電場の位相に同期して一定の位相でイオンが分離空間5に導入されるなら、一定の変位量Yが得られるということでもある。この変位量Yは質量電荷比に反比例する。なお、一次元高周波電場が矩形波高周波電場以外の高周波電場である場合、Yを表す式は変化するが、それ以外の特徴(I)および(II)は同様に成り立つ。
Y=zieET2/4m・・・(9)
となる。
vy=dy/dt=0
となること、そしてその前後にイオンの変位速度vyがきわめて小さい時間領域が存在することが示されている。
上述したように、分離空間5に導入された各イオンは、一次元高周波電場から受ける力によってy方向において変位する。この変位速度vyはイオンの質量電荷比に反比例する。しかも交流電場中でのイオンの変位は静電場中での等加速度運動と異なる。この結果、質量電荷比が互いに異なるイオン種は互いに異なる飛行路を飛行することになり、空間的に分離される(後述する図6参照。)。
一次元高周波電場が次式
Ey=ESsinωt・・・(10)
で表される正弦波高周波電場であるとする。式中、ωは正弦波高周波電場の角周波数である。式(10)を式(6)に代入し、vy0=0としてイオン入射後の1周期間において運動方程式を2度積分すると、正弦波高周波電場中でのYを表す式として次式
Y=(zieEST2/2πm)cosωt0・・・(11)
が得られる。
Ey=ESsinωt0=0
であるので、イオン群は電場の強さが0である時点において分離空間5に導入され、被測定イオン種は1周期後の電場の強さが0である時点およびその前後において分離空間5から出射されるので、被測定イオン種が端縁場の影響を受けることはほとんどない。以上から、イオン入射時の正弦波高周波電場の位相は0またはπであるのが最も好ましい。両者はy値の正負が逆になるだけで実質的な内容は同じであるので、以下、位相が0である場合についてのみ説明する。このとき式(11)は
Y=zieEST2/2πm・・・(12)
となる。
dy/dt=0
であるので、経過時間が様々に異なるイオンAが同一のz方向位置に飛来してきても、経過時間の違いによる変位量yの違いがわずかになり、変位量yがYにほぼ揃うからである。
TL0=L/v=L(m/2zieU)1/2・・・(13)
で与えられる。標準のイオンが1周期後に分離空間5から出射され、その他の被測定イオン種のイオンがその前後に出射される条件は、
TL0=T・・・(14)
である。これを式(13)に代入すると、次式
L(m/2zieU)1/2=T・・・(15)
が得られる。第1の方法では、被測定イオン種の質量電荷比に対して式(15)が満たされるように、加速電圧U、正弦波高周波電場の周期Tおよび分離空間5の有効長Lを選択する。
第2の方法では、図3(C)に示すように、電場の強さが0になる休止期間を矩形波高周波電場の一周期の前後に設け、イオン群は休止期間の間に分離空間5に導入され、被測定イオン種は矩形波高周波電場の作用を1周期間受けたのち、一周期後の休止期間の間に分離空間5から出射されるようにする。この場合、イオン群は矩形波高周波電場の作用をその立ち上がり時から受けるので、被測定イオン種の変位量YはTi=0の場合と同じになり、式(9)で与えられる。
第1および第2の方法によれば、初期状態のばらつきに影響されることが少なく、高い質量分解能を実現するために加速電圧を大きくする必要が小さい。この結果、装置の大型化を招くことが少ない。ただし、図4(B)に示されているように、第1の方法では曲線A0、A-10およびA+10が完全に1点に重なることはなく、これが質量分解能を制限する。また、一次元高周波電場が矩形波高周波電場である場合、正弦波高周波電場の場合ほど第1の方法は効果的ではない。この原因は、矩形波高周波電場では電場の強さが立ち上がりおよび立ち下がりで瞬間的に変化し、電場の強さが0近傍にある時間領域が存在しないことにある。
第1の方法の説明で述べたように、被測定イオン種のイオンが分離空間5の有効長Lを通過するのに要する時間をTLとおき、そのうち、標準のイオンのTLをTL0とおく。休止期間の間に導入されたこれらのイオンが、1周期後の休止期間の間に分離空間5から出射される条件は、図3(C)から次の関係
TP+T<TL<TP+T+T0・・・(16)
が満たされることである。式中、TPはイオン群が導入される時刻から一周期の始まりまでの時間であり、T0は一周期後の休止期間の長さである。なお、本論文では周期Tに休止期間の長さは含めないものとする。
TP+T+TE<TL0<TP+T-TE+T0・・・(17)
となる。上式に式(13)を代入すると、次式
TP+T+TE<L(m/2zieU)1/2<TP+T+T0-TE・・・(18)
が得られる。
TP≒0~TD・・・(19)
T0≒TD+2TE・・・(20)
を満たし、右辺よりわずかに大きいのがよい。このとき、イオン群パルスの先端で導入された被測定イオンのうち、滞在時間が最も短いイオンが休止期間の開始直後に分離空間5から出射される条件と、イオン群パルスの終端で導入された被測定イオンのうち、滞在時間が最も長いイオンが休止期間の終了直前に分離空間5から出射される条件とはほぼ同じになる。この条件は、TL0が
TL0=L(m/2zieU)1/2≒T+TD+TE・・・(21)
を満たし、最右辺の(T+TD+TE)よりわずかに大きいことである。
イオン検出部4は、基準線11と出射面9との交点(0,0)から出射面上でy方向へ距離Cだけ離れた位置に飛来するイオンを検出するように構成される(後述する[イオン検出部]の項も参照。)。一方、被測定イオン種は、一次元高周波電場の作用を1周期間受けたのち、出射面上に飛来する。高周波電場はこの1周期の間に被測定イオン種をy方向へ距離Yだけ変位させる。したがって
C=Y・・・(22)
とすれば、イオン検出部4は、出射面上に飛来するイオンのy方向位置に基づいて他のイオン種と区別して、被測定イオン種を検出することができる。一次元高周波電場が矩形波高周波電場である場合、式(22)と式(9)から次式
C=zieET2/4m・・・(23)
が得られる。質量分析装置10では、被測定イオン種の質量電荷比に対して式(23)が満たされるように、矩形波高周波電場の周期Tおよび強さEを選択する。Tが同じであれば、式(23)を満たすEは被測定イオン種の質量電荷比に比例する。
質量走査では、質量電荷比が異なる複数のイオン種を時系列的に被測定イオン種として検出する。質量走査には、所定の質量電荷比の範囲を連続的に走査して、その範囲内にあるすべてのイオン種を質量電荷比の順に検出して質量スペクトルを得る通常走査と、質量電荷比が異なるいくつかのイオン種を次々に切り換えて選択的に検出する選択(切り換え)走査とがある。選択走査では、特定の質量電荷比を有するいくつかのイオン種のイオン量を、短時間のうちに繰り返し測定することができる。
第1の質量走査方法では、周期Tを固定し、走査する各被測定イオン種の質量電荷比に応じて加速電圧Uを変化させ、各被測定イオン種が順次式(16)または(18)を満たすようにする。より具体的には、例えば各被測定イオン種の質量電荷比に比例するようにUを変化させ、各被測定イオン種のTL0が順次所定の一定値になるように走査する。このようにすると、始め式(21)が満たされており、その後TEの大きな増加がなければ、走査中も各被測定イオン種が順次式(21)を自動的に満たしていくことになり、装置の運用が簡易になる。
第2の質量走査方法では、Uを固定し、走査する各被測定イオン種の質量電荷比に応じてTを変化させ、式(16)を満たす各イオン種を順次被測定イオン種として検出する。より具体的には、例えば周期の二乗T2が各被測定イオン種の質量電荷比に比例するように、Tを変化させる。この場合、Uが固定されているので、各イオン種のTL0は変化しない。その上でTを変えていくと、各Tごとに式(17)を満たすTL0が変化していくので、該当するTL0をもつ各イオン種が式(18)を満たす被測定イオン種として順次検出される。
図6は質量分析装置10における各イオン種の飛行路を示すグラフ(A)、および第1の質量走査方法で走査した場合のその変化を示すグラフ(B)である。図6は、イオン種が1価で質量50u、100u、200uおよび400uであり、矩形波高周波電場の周期Tが10μsである例について、運動方程式(6)を数値積分して得られた結果を示している。図示した飛行路は標準の運動エネルギーzieUでz方向へ飛行するイオンの飛行路であり、高周波電場の作用を受けている間は太線で示し、休止期間の間は細線で示した。ここで、TPおよびT0は必要最小限の長さとし、分離空間5の有効長Lは、被測定イオン種のすべてが分離空間5内に少なくとも1周期間滞在するように、初期状態のばらつきを考慮して、上記T、被測定イオン種のm、および後述のUを式(15)に代入して求まる長さ138.9mmよりやや長い長さとする。イオン検出部4は、基準線11と出射面9との交点(0,0)から出射面9上でy方向へ距離C=61.42mmだけ離れた位置に飛来するイオンを検出するように構成されているものとする。
イオン源1は、通常のイオン源であってもよいし、直交加速型イオン源であってもよい。イオン源1が直交加速型イオン源である場合、出射面9上に飛来するイオンの位置は直線状にのびるが、この方向をx方向にとれば、y方向における質量分解能を損なうことなく、直交加速型イオン源を利用することができる。直交加速型イオン源を用いると、試料のイオン化が時間に関して連続的に行われるイオン源において、断続する引き出し期間の間に生成するイオン群の一部も利用できるので、イオン利用率が向上する。なお、イオン利用率とは、イオン源において生成された被測定イオン種のイオンのうち、イオン検出器で検出されるイオンの割合を言うものとする。
図7(A-1)はイオン検出部4の例を示す概略図である。このイオン検出部にはイオン検出器13、および出射面9とイオン検出器13との間に配置されたスリット12が設けられている。スリット12は被測定イオン種を選択的に通過させる遮蔽部材の例であり、上側スリット12aと下側スリット12bの間隙の大きさが変更可能である。間隙の中心は基準線11からy方向へCだけ離れた位置にある。間隙の大きさは、要求される質量分解能などに応じて選択されるが、例えば0.05~0.5mm程度である。質量分析装置10は、スリット12を用いることによって、質量分解能を比較的低く抑え、被測定イオン種の透過率を優先する高感度測定にも、被測定イオン種の透過率は低下するものの、高い質量分解能が得られる高分解能測定にも対応することができる。
(1)イオン源1から出射される全イオン種、または被測定イオン種およびそれより質量 電荷比が大きいイオン種のイオン量を測定しているので、高質量イオンの見落としが なく、質量走査を打ち切る判定が容易かつ正確である。
(2)所定の被測定イオン種のイオン量は、その被測定イオン種の検出位置の前後におけ る検出イオン量の差として直読できる。通常の質量スペクトルでこのイオン量を求め るには、そのイオン種のピークを積分してピーク面積を算出する必要がある。本方法 はこれに比べて簡易かつ正確であり、データ処理システムを簡略化できる。
(3)通常の質量スペクトルが必要であれば、階段状のスペクトルを微分すればよい。ス ペクトルの微分は積分に比べて容易である。
式(18)の条件を満たす被測定イオン種は複数種存在し得るので、休止期間を有する矩形波高周波電場を用いる場合、休止期間の長さT0に対応する質量電荷比範囲の複数種の被測定イオン種を同時分析することができる。
イオンの質量の変化m→m+Δm(Δm>0)によって変位量の変化Y→Y-ΔY(ΔY>0)が生じるとすると、式(9)から
Y-ΔY=zieET2/4(m+Δm)
≒Y(1-Δm/m)
であり、次式
Δm/m≒ΔY/Y・・・(24)
が得られる(厳密には、滞在時間の増加によるΔYの減少も生じるが、これは2次以上の微小項になるので、無視できるとした。)。
(1)要求される質量分解能m/Δmと実現可能なイオン検出部4の位置分解能ΔYとか ら、式(24)を用いて、被測定イオン種に生じさせる変位量Yを定める。
(2)変位量Y、被測定イオン種の質量電荷比、および実現可能な高周波電場の強さEか ら、式(9)を用いて高周波電場の周期Tを定める。
(3)周期Tと被測定イオン種の質量電荷比とから、式(18)を用いて分離空間5の有 効長Lおよび加速電圧Uを定める。
要求される質量分解能m/Δmが300であり、位置分解能ΔYが0.2mmであるとする。この場合、式(24)から、おおよそ
Y=60.0mm
であることが必要である。
T=10μs
程度であるのがよい。この場合、被測定イオン種に上記の変位量Yを生じさせるためには、式(9)から
E≒24.9~4970Vm-1
が必要である(上記のEの範囲は、被測定イオン種の質量の範囲1~200uに対応する。以下、同様。)。ここで電極間距離Lyが100mmであるとすると、高周波電源の電圧Vyとして
Vy≒2.49~497V
が必要である。
U=1~200V
程度であるのがよい。Lは式(18)を満たすように選択する。このLは、同じT、m、およびUに対し式(15)を満たすLの長さ139mmより、(TP+TE)の分だけ長くする。
Y≒60.0mm
となる。この場合、質量分解能は先述した例と同じく300になり、被測定イオン種の質量は5000u±17uの範囲にあることが確定する。例えば高分子量物質のおおまかな重合度を求める目的には、この程度のデータで十分である。このような有用なデータが上述した簡易な質量分析装置10から得られることは注目に値する。
要求される質量分解能m/Δmが2500であり、位置分解能ΔYが0.1mmであるとする。この場合、式(24)から、おおよそ
Y=250.0mm
であることが必要である。
T=25μs
程度であるのがよい。この場合、被測定イオン種に上記の変位量Yを生じさせるためには、式(9)から
E≒414.6~20700Vm-1
が必要である。ここで電極間距離Lyが300mmであるとすると、高周波電源の電圧Vyとして
Vy≒124.4~6219V
が必要である。
U=20~1000V
程度であるのがよい。Lは式(18)を満たすように選択する。このLは、同じT、m、およびUに対し式(15)を満たすLの長さ311mmより、(TP+TE)の分だけ長くする。
本発明の質量分離装置は、図示は省略するが、例えば、イオン源1、イオン導入部2、質量分析部3、およびイオン選択部などで構成され、少なくとも質量分析部3とその前後のイオンの通路は高真空下にある。イオン選択部は、出射面9上の所定のy方向位置に飛来するイオンを取り出す手段として、例えば細孔を有する遮蔽部材(スリット12など)などを備える(符号を付した部材については図1、図2および図7参照。)。
実施の形態2では、請求項4に記載した、複数個の質量分析部が連続して配置された質量分析装置の例について説明する。
実施の形態3では、請求項5に記載した、分離空間が飛行時間型質量分析装置の飛行空間の一部をなすように、飛行時間型質量分析装置と合体して配置された質量分析装置の例について説明する。
実施の形態4では、請求項6に記載した質量分析装置の例について説明する。
6、7…電極、6a、7a…電極6および7の、イオンの通路に面した主面、
8…入射面、9…出射面、10…質量分析装置、11…基準線、12a…上側スリット、
12b…下側スリット、13…イオン検出器、14…遮蔽板、
15、16…イオン検出器、17…静電レンズ、20A、20B…質量分析装置、
21…初段質量分析部、22…中間質量分析部、23…終段質量分析部、
24…初段イオン検出部、25…終段イオン検出部、26、27…イオン群加工手段、
28…終段質量分析部、29…イオン群加工手段、30…質量分析装置、
31…TOF部、32…リフレクトロン、33…イオン群加工手段、
34…イオン検出部、40…質量分析装置、43…質量分析部、44…イオン検出部、
45…分離空間、46~49…電極、50…出射面
Claims (11)
- 試料をイオン化する手段、およびパルス状のイオン群を所定の加速電圧で質量分析部 へ導入する手段を備えるイオン源と、
前記イオン群の飛行方向を収束させる手段、及び/又は所定の方向へ飛行する前記イ オン群を選択して取り出す手段を備えるイオン導入部と、
導入した前記イオン群を飛行させる分離空間、および前記イオン群の入射方向に所定 の角度で交差する方向(以下、y方向と呼ぶ。)に作用する一次元高周波電場を前記分 離空間に形成する手段を備え、前記一次元高周波電場の作用によって、質量電荷比が互 いに異なるイオン種に互いに異なる飛行路を飛行させる前記質量分析部と、
前記分離空間の末端の出射面上の所定のy方向位置に飛来するイオンを検出する手段 を備えるイオン検出部と
を少なくとも有し、前記イオン群は前記一次元高周波電場の位相に同期したパルスとして前記分離空間へ導入され、所定の質量電荷比を有する被測定イオン種が前記一次元高周波電場の作用をn周期間またはそれと実質的に同等とみなされる期間受けて前記分離空間から出射され、前記出射面上でのy方向飛来位置に基づいて他のイオン種と区別して検出される、質量分析装置。
(ただし、nは自然数である。) - 前記被測定イオン種は次の関係
T=L(m/2zieU)1/2
を満たし、前記イオン群は前記一次元高周波電場の強さが0である時点において前記分離空間へ導入され、前記被測定イオン種は実質的に1周期後の前記一次元高周波電場の強さが0である時点において前記分離空間から出射される、請求項1に記載した質量分析装置。
(ただし、ziはイオン種の電荷数であり、m、e、U、L、およびTは、それぞれ、SI単位で表されたイオン種の質量、電気素量、前記加速電圧、前記分離空間の有効長、および前記一次元高周波電場の周期である。) - 前記一次元高周波電場は電場の強さが0になる休止期間を一周期の前後に有し、前記被測定イオン種は次の関係
T+TP<TL<T+TP+T0
を満たし、前記イオン群は前記一周期の前の前記休止期間において前記分離空間へ導入され、前記被測定イオン種は前記一周期の後の前記休止期間において前記分離空間から出射される、請求項1に記載した質量分析装置。
(ただし、TL、TP、およびT0は、それぞれSI単位で表された、前記被測定イオン種のイオンが前記分離空間の前記有効長を通過するのに要する時間、前記イオン群が導入される時刻から前記一周期の始まりまでの時間、および前記一周期の後の前記休止期間の長さである。) - 複数個の前記質量分析部が連続して配置され、前記イオン群はまず初段質量分析部で質量分離され、分離された前記被測定イオン種の一部は前記イオン検出部で検出されるが、残りは後続の質量分析部へ導入されてさらに質量分離され、その後方に配置されたイオン検出部で検出される質量分析装置であって、前記残りの被測定イオン種は前記休止期間の間に前記質量分析部間を後続側へ移動する、請求項3に記載した質量分析装置。
- 前記分離空間が飛行時間型質量分析装置の飛行空間の一部をなすように前記飛行時間型質量分析装置と合体して配置され、前記イオン群はまず前記分離空間に導入されて前記質量分析部で質量分離され、分離された前記被測定イオン種の一部は前記イオン検出部で検出されるが、残りは前記飛行空間における飛行を続け、前記飛行時間型質量分析装置で分析される、請求項3に記載した質量分析装置。
- 前記質量分析部が、前記一次元高周波電場(以下、y方向高周波電場と呼ぶ。)と周期が実質的に同じで位相が実質的に(1/4)周期異なり、作用する方向が前記イオン群の入射方向に所定の角度で交差し、かつy方向と直交する方向(以下、x方向と呼ぶ。)であるx方向高周波電場を前記分離空間に形成する手段を備え、
前記イオン検出部が、前記出射面上の所定のx方向位置に飛来するイオンを検出する手段を備え、
前記イオン群は前記y方向高周波電場の立ち上がり時またはその直前に前記分離空間に導入され、前記nは1であり、
これとは別のイオン群が前記x方向高周波電場の立ち上がり時またはその直前にパルス的に前記分離空間に導入され、このイオン群中の、所定の質量電荷比を有する被測定イオン種は、前記x方向高周波電場の作用を1周期間またはそれと実質的に同等とみなされる期間受けて前記分離空間から出射され、前記出射面上でのx方向飛来位置に基づいて他のイオン種と区別して検出される、請求項1に記載した質量分析装置。 - 前記一次元高周波電場の波形が矩形波、正弦波(または余弦波)、階段波、台形波、三角波、のこぎり波、またはこれらの一部を改変した波形、あるいは複数のこれらの波形を合成した波形である、請求項1に記載した質量分析装置。
- 前記一次元高周波電場の周期を固定し、前記加速電圧を変化させて質量走査を行う、請求項1に記載した質量分析装置。
- 前記加速電圧を固定し、前記一次元高周波電場の周期を変化させて質量走査を行う、請求項1に記載した質量分析装置。
- 前記イオン検出部は、前記被測定イオン種とともに、または前記被測定イオン種とは別個に、前記被測定イオン種よりも質量電荷比の大きいイオン種を検出するイオン検出器を有する、請求項1に記載した質量分析装置。
- 試料をイオン化する手段、およびパルス状のイオン群を所定の加速電圧で質量分析部 へ導入する手段を備えるイオン源と、
前記イオン群の飛行方向を収束させる手段、及び/又は所定の方向へ飛行する前記イ オン群を選択して取り出す手段を備えるイオン導入部と、
導入した前記イオン群を飛行させる分離空間、および前記イオン群の入射方向に所定 の角度で交差する方向(以下、y方向と呼ぶ。)に作用する一次元高周波電場を前記分 離空間に形成する手段を備え、前記一次元高周波電場の作用によって、質量電荷比が互 いに異なるイオン種に互いに異なる飛行路を飛行させる前記質量分析部と、
前記分離空間の末端の出射面上の所定のy方向位置に飛来するイオンを取り出す手段 を備えるイオン選択部と
を少なくとも有し、前記イオン群は前記一次元高周波電場の位相に同期したパルスとして前記分離空間へ導入され、所定の質量電荷比を有する被選択イオン種が前記一次元高周波電場の作用を1周期間またはそれと実質的に同等とみなされる期間受けて前記分離空間から出射され、前記出射面上でのy方向飛来位置に基づいて他のイオン種と区別して取り出される、質量分離装置。
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PCT/JP2013/075780 WO2014050836A1 (ja) | 2012-09-25 | 2013-09-24 | 質量分析装置および質量分離装置 |
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US (1) | US9330896B2 (ja) |
EP (1) | EP2924711A4 (ja) |
JP (1) | JP6006322B2 (ja) |
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US9543138B2 (en) * | 2013-08-19 | 2017-01-10 | Virgin Instruments Corporation | Ion optical system for MALDI-TOF mass spectrometer |
GB201519830D0 (en) * | 2015-11-10 | 2015-12-23 | Micromass Ltd | A method of transmitting ions through an aperture |
US10541124B2 (en) | 2016-01-27 | 2020-01-21 | Dh Technologies Development Pte. Ltd. | Ion injection method into side-on FT-ICR mass spectrometers |
CN109001117A (zh) * | 2018-08-09 | 2018-12-14 | 金华职业技术学院 | 一种研究大分子离子光电子谱的方法 |
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JPH02270256A (ja) * | 1989-04-11 | 1990-11-05 | Jeol Ltd | 同時検出型質量分析装置 |
JPH05174783A (ja) * | 1991-12-25 | 1993-07-13 | Shimadzu Corp | 質量分析装置 |
JP2005536021A (ja) * | 2002-08-19 | 2005-11-24 | エムディーエス インコーポレーティッド ドゥーイング ビジネス アズ エムディーエス サイエックス | 空間分散を伴う四重極質量分析装置 |
JP2010108941A (ja) * | 1998-08-05 | 2010-05-13 | National Research Council Canada | 大気圧3次元イオントラッピングのための装置および方法 |
WO2011109311A1 (en) * | 2010-03-02 | 2011-09-09 | Thermo Finnigan Llc | A quadrupole mass spectrometer with enhanced sensitivity and mass resolving power |
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US2659822A (en) * | 1947-04-22 | 1953-11-17 | George H Lee | Mass spectrometer |
US5726448A (en) * | 1996-08-09 | 1998-03-10 | California Institute Of Technology | Rotating field mass and velocity analyzer |
US6794647B2 (en) * | 2003-02-25 | 2004-09-21 | Beckman Coulter, Inc. | Mass analyzer having improved mass filter and ion detection arrangement |
JP5585394B2 (ja) * | 2010-11-05 | 2014-09-10 | 株式会社島津製作所 | 多重周回飛行時間型質量分析装置 |
JP2012216527A (ja) * | 2011-03-29 | 2012-11-08 | Yoshinori Sano | 質量分析装置 |
JP6080706B2 (ja) * | 2013-06-24 | 2017-02-15 | 住友重機械イオンテクノロジー株式会社 | 高周波加速式のイオン加速・輸送装置 |
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2013
- 2013-09-24 EP EP13840677.2A patent/EP2924711A4/en not_active Withdrawn
- 2013-09-24 WO PCT/JP2013/075780 patent/WO2014050836A1/ja active Application Filing
- 2013-09-24 US US14/430,788 patent/US9330896B2/en active Active
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JPH02270256A (ja) * | 1989-04-11 | 1990-11-05 | Jeol Ltd | 同時検出型質量分析装置 |
JPH05174783A (ja) * | 1991-12-25 | 1993-07-13 | Shimadzu Corp | 質量分析装置 |
JP2010108941A (ja) * | 1998-08-05 | 2010-05-13 | National Research Council Canada | 大気圧3次元イオントラッピングのための装置および方法 |
JP2005536021A (ja) * | 2002-08-19 | 2005-11-24 | エムディーエス インコーポレーティッド ドゥーイング ビジネス アズ エムディーエス サイエックス | 空間分散を伴う四重極質量分析装置 |
WO2011109311A1 (en) * | 2010-03-02 | 2011-09-09 | Thermo Finnigan Llc | A quadrupole mass spectrometer with enhanced sensitivity and mass resolving power |
Non-Patent Citations (1)
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Also Published As
Publication number | Publication date |
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WO2014050836A9 (ja) | 2015-05-14 |
US9330896B2 (en) | 2016-05-03 |
JP6006322B2 (ja) | 2016-10-12 |
EP2924711A1 (en) | 2015-09-30 |
EP2924711A4 (en) | 2016-06-29 |
US20150357176A1 (en) | 2015-12-10 |
JPWO2014050836A1 (ja) | 2016-08-22 |
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