JP2010146876A - Multiply-bent type quadrupole time-of-flight mass spectrometer - Google Patents

Abstract

The present invention relates to a multi-bending quadrupole time-of-flight mass spectrometer, which can improve the resolution while taking advantage of the small size of the quadrupole type, and reduces the data acquisition time per measurement to several millimeters. It is an object of the present invention to provide a multi-bending quadrupole time-of-flight mass spectrometer that can be shortened to seconds or less.
A structure in which an electrode member is in contact with a quadrupole of a set of four electrodes bent in an arc shape and a quadrupole of a set of four linear electrodes so that the optical axes on ion optics are substantially coincident with each other at a connection portion. Thus, the quadrupole shape is integrated or connected, and the quadrupole portion functions as an ion guide so that the flight time of flying ions can be measured.
[Selection] Figure 2

Description

  The present invention relates to a multi-bending quadrupole time-of-flight mass spectrometer, and more specifically, a multi-bending quadrupole time-of-flight mass spectrometer that can function as a time-of-flight mass spectrometer and a mass filter. Relates to the device.

  A mass spectrometer (quadrupole mass spectrometer: QMS) composed of quadrupoles is often used as a small general-purpose machine, and can be used to set a continuous sweep or jump of a quadrupole field that is a mass spectrometer. In this method, ions having different masses are selected and detected (called a mass filter).

  As a conventional quadrupole mass spectrometer, a quadrupole mass spectrometer comprising an ion source and a detector that detects ions that have passed through the quadrupole filter, the ion of the ions that pass through the quadrupole filter is described. A technique for changing the DC voltage applied between the ion source and the quadrupole filter according to the scanning speed when scanning the applied voltage to the quadrupole filter so that the mass number changes sequentially. It is known (see, for example, Patent Document 1).

In addition, in a time-of-flight mass spectrometer, an apparatus is known in which a flight tube is made of a first metal, and a wall portion that constitutes at least one end of the flight tube has a fitting structure capable of sliding (for example, Patent Document 2).
JP 2002-25498 A (paragraphs 0012 to 0014, FIGS. 1 to 2) JP 2008-135192 A (paragraphs 0026 to 0030, FIG. 4)

  The quadrupole mass spectrometer is generally not so high that the mass resolution divides one mass difference, but is used in a range that is small, inexpensive, and easy to use. In applications that require high mass resolution, other high-performance mass spectrometers such as double-focusing mass spectrometers are used. In addition, the time required for separating different masses and detecting different ions requires about 100 milliseconds at the fastest in acquiring data for one measurement by controlling the sweep or jumping of the analysis field. .

  The present invention has been made in view of such problems, and the resolution can be improved while taking advantage of the small size of the quadrupole type, and the data acquisition time for one measurement is several milliseconds or less. It is an object of the present invention to provide a device that can be shortened to an improved sampling simultaneity.

  (1) In the first aspect of the invention, the quadrupole of the quadruple electrode bent in a circular arc shape and the quadrupole of the quadruple linear electrode set substantially coincide with each other in the optical axis on the ion optics. In this way, the electrode members are in contact with each other and have a quadrupole outer shape that is integrated or connected, and the quadrupole portion functions as an ion guide so that the time of flight of flying ions can be measured. It is characterized by having a configuration.

  (2) The invention according to claim 2 is characterized in that the quadrupole of a set of four arcs and the quadrupole of a set of four linear electrodes arranged in four directions obliquely 45 degrees from the central axis are ions. The structure is such that the electrode members are in contact with each other so that the optical axes on the optics are almost coincident with each other at the connection part, and the quadrupole part functions as an ion guide. The flight time of the flying ions can be measured.

  (3) The invention according to claim 3 is connected by arbitrarily changing the number of combinations of quadrupoles of four electrodes bent in an arc shape and the quadrupole of four sets of linear electrodes, and the connecting direction, It is characterized in that the time of flight of ions is measured by connecting at least two sets of linear quadrupole parts.

  (4) In the invention according to claim 4, the quadrupoles of the four electrode sets bent in an arc shape and the quadrupoles of the four linear electrode sets substantially coincide with each other in the optical axis on the ion optics. In this configuration, the quadrupole part of the quadrupole electrode set is connected in an arc shape by switching the electric system circuit. It is possible to apply a voltage different from the part, and it can be used as a mass filter, so that the entire quadrupole part can function as an ion guide and the time of flight of ions can be measured and mass analysis can be performed as a mass filter Any mode of the state is switched as necessary.

(5) The invention according to claim 5 is characterized in that the radius of rotation of the optical axis of the arcuate electrode assembly portion is within 10 times the diameter of the electrode.
(6) The invention described in claim 6 is characterized in that the electrode is rod-shaped or pipe-shaped.

(1) According to the first aspect of the present invention, the quadrupole portion can function as an ion guide so that the time of flight can be measured.
(2) According to the invention of claim 2, the quadrupole portion can be an ion guide arranged in four directions obliquely 45 degrees from the central axis, and the neutral particle component is attached to the electrode surface. Contamination can be reduced.

(3) According to the invention described in claim 3, the time of flight of ions can be measured with a high resolution by connecting two or more linear quadrupole portions.
(4) According to the invention described in claim 4, the apparatus can be used as a mass filter or a time-of-flight mass spectrometer.

(5) According to the invention described in claim 5, it is possible to provide a mass spectrometer suitable for miniaturization by making the radius of rotation of the optical axis of the arcuate electrode portion within 10 times the diameter of the electrode. .
(6) According to the invention described in claim 6, a multi-bending quadrupole time-of-flight mass spectrometer is provided regardless of whether the electrodes are rod-shaped or pipe-shaped. Can do.

(Embodiment 1)
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing an outline of the apparatus configuration of the present invention. 1 is an ion supply unit that relays ions from an ion source or outside the system, 2 is an ion reservoir or ion packetization unit that temporarily accumulates ions and ejects them in a pulsed manner, or pulsed ions are turned on and off. 3 is a mass spectrometric field for mass-dispersing ions, and 4 is an ion detector for finally detecting ions. For example, a power supply control system, an evacuation system, a data processing system, and the like other than the characteristic features of the present invention are omitted.

  In the apparatus configured as described above, the ions emitted from the ion supply unit 1 are stored in the ion reservoir or the ion packet unit 2, and the ions are temporarily accumulated and ejected in pulses. The mass analysis field 3 disperses the emitted ions for each mass. The ions dispersed in mass reach the ion detector 4 and the mass is detected.

  FIG. 2 is a diagram showing a configuration example of multiple bending. This figure shows the arrangement and configuration of the quadrupole as a basic ion optical system constituting the mass spectrometric field 3 in FIG. 1 in a three-dimensional view as a whole, and is modeled for calculating the ion orbit. It is a figure of what was used. For the simulation model, the insulating material that supports the electrodes is not shown here, but these electrodes are held by an insulating support and stored in a vacuum chamber maintained by an evacuation apparatus.

  The electrode is a linear quadrupole part (hereinafter referred to as a linear quadrupole) 6 as a linear quadrupole, and a bar electrode constituent quadrupole bent into an arc as an arcuate quadrupole. 2 (hereinafter referred to as an arc-shaped quadrupole) 7 is connected to the external structure as shown in FIG. FIG. 2 is a diagram illustrating a configuration example of a multi-fold bent quadrupole. As shown in the figure, the three-dimensional zigzag bending is performed, and the long optical axis is folded short.

  8 is an ion inlet side slit, and 9 is an ion outlet side slit. The ion inlet side slit 8 and the ion outlet side slit 9 are electrodes having pores that serve as ion inlets and outlets in this system. A DC voltage and a high-frequency voltage are supplied to the quadrupole of the linear quadrupole 6 and the arc-shaped quadrupole 7, and a power supply and a control system for that purpose are not shown, but are included as a configuration.

FIG. 3 shows a basic example of the electrode voltage supply of the quadrupole part. FIG. 3 is a diagram showing a cross section of a quadrupole electrode and a basic wiring example. Symbols in the expression in the figure indicate Vo as the high-frequency amplitude voltage value, ω as the angular frequency, t as time, θ as the phase, and U1 as the DC voltage value (for setting the shaft voltage). In FIG. 3, K1 to K4 are electrodes. Vo · cos (ωt + θ) + U1 is applied to the electrodes K1 and K4, and −Vo · cos (ωt + θ) + U1 is applied to the electrodes K2 and K3.

  Although not described in detail, the ion detection unit 4 in FIG. 1 converts ions into an electrical signal, the observed value of the amount of ions reached, and the time from the time when the ions are ejected from the ion reservoir or ion packetization unit 2 to the time when the detection unit arrives. It also has a function to measure. The operation of the apparatus configured as described above will be described as follows.

In the example shown in FIG. 2, the high-frequency voltage Vrf (= ± Vo · cos (ωt + θ)) and the DC voltage Vdc (= U1) are superimposed on the linear quadrupole 6 and the arc-shaped quadrupole 7. The inlet voltage Vdc_in and the outlet voltage Vdc_out are also applied to the ion inlet side slit 8 and the ion outlet side slit 9, respectively.

  When ions are introduced into the quadrupole field system from the pores of the ion entrance slit 8 under these conditions, the ions travel while vibrating in the radial direction (perpendicular to the optical axis) at a high frequency voltage. Then, it reaches the ion exit side slit 9 and proceeds out of this system. Ions are ejected as a packet (a lump of time in a short time), and the elapsed flight time from the ejection time until the ions are detected as a signal is measured.

  When ions are ejected in packets, the same kinetic energy is imparted to almost all ions, so the elapsed flight time from ejection to detection becomes the time required depending on the mass, so it is used as a mass spectrometer. be able to. Since it is easier to obtain a time difference due to a mass difference when the ion flight time is lengthened, it is advantageous to increase the flight time, that is, to increase the number of repetitions of bonding. However, even if the distance is increased, the system has time aberration, so the length is limited.

  This is because when the amount of aberration is enlarged, when the difference due to the difference in mass cannot be distinguished from the difference due to the aberration, further mass separation cannot be performed. In addition, if a cluster of ions diffuses due to aberrations, it reaches a time when detecting a signal, and thus a sensitivity limit is involved. FIG. 4 is a simulation of the ion trajectory flight trajectory when the quadrupole analysis field is a linear quadrupole 6 and the arc quadrupole 7 is made to function as an ion guide to be a time-of-flight type. It is. In other words, FIG.

  FIG. 5 is a diagram showing an example in which the flight time of ions is recorded. The figure shows a measurement record of the time of flight when ions of different masses were ejected at the same time. In the figure, the numerical value following the TOF notation represents the flight time, and the mass after the mass represents the mass. It can be confirmed that the difference in the mass caused a difference in the flight time.

According to the first embodiment, the quadrupole part can function as an ion guide so that the flight time can be measured. In addition, by connecting two or more linear quadrupole parts, the time of flight of ions can be measured with high resolution.
(Embodiment 2)
Here, the modification about the bending direction etc. of the arc-shaped quadrupole of a quadrupole connection part is shown. The example shown in FIG. 2 is a case where it is bent three-dimensionally or three-dimensionally so as to show the basic part of bending shown in FIG. FIG. 6 is a diagram showing a three-dimensional bending type and a track superposition diagram. The orbit is shown by a thin solid line. The example shown in FIG. 7 is bent in the same plane. That is, FIG. 7 is a diagram showing a plane bending type and a track superposition diagram. The orbit is shown by a thin solid line.

  When the bending directions are combined in this way, the shape can be changed as necessary. Although not illustrated here, it is possible to adopt a helical structure incorporating a structure such as a lap or spiral on the same plane and an element whose angle is slightly shifted in a direction perpendicular to the spiral direction. Although the partial rotation angles of the arc-shaped quadrupoles in the examples taken up are the same and the connection example in which the direction of the ion travel changes by 180 degrees is shown, the angle of 180 degrees is not necessarily required. If necessary, ions may be guided and deflected at an angle that can maintain a ratio relationship between the electrode diameter and the inscribed diameter in a cross section perpendicular to the optical axis.

  As shown in Fig. 8, the degree of bending at the arc-shaped quadrupole part can guide ions even with a small turning radius. Can be changed. In this case, a mass spectrometer suitable for miniaturization can be provided such that the radius of rotation of the optical axis of the arcuate electrode portion is within 10 times the diameter of the electrode. The operation of the apparatus configured as described above will be described as follows.

There is basically no difference from the first embodiment. The deflection direction and amount when the ions simply travel are different. However, since each ion takes a different trajectory depending on the initial ion condition, the ion flight trajectory that can be taken varies depending on the deflection, the form of connection, the length of the diameter, and the like. Therefore, the results are not exactly the same, but since this is not an important factor, the way of bending the track can be changed according to the manufacturing convenience.
(Embodiment 3)
FIG. 9 is a diagram showing an example of the ion optical system having the most basic structure in the mass spectrometry field of FIG. 1 in the present invention, and is a diagram showing the entire quadrupole optical system. The quadrupole arrangement and configuration are shown in a three-dimensional view as an overall view, and are used by modeling for calculation of ion trajectories with the number of connections in the minimum unit in order to capture features.

  For easy viewing, FIG. 10 shows a projection of the entire quadrupole optical system. FIG. 10 shows a plan view, a front view, and a side view. The same components as those in FIG. 2 are denoted by the same reference numerals. 6 is a linear quadrupole, 7 is an arc-shaped quadrupole, 8 is an ion inlet side slit, and 9 is an ion outlet side slit.

  For the simulation model, as in FIG. 2, the insulating material indicating the electrodes is not shown here, but these electrodes are held by an insulating support and stored in a vacuum region maintained by a vacuum exhaust device. Is done. The electrode has a structure in which a part of the linear quadrupole 6 and a part of the arc-shaped quadrupole including a part of the linear part at both ends are connected with a gap.

  In this example, it is composed of three sets of linear quadrupoles 6 and two sets of arc-shaped quadrupoles 7, and three-dimensional zigzag bending is performed as shown in FIG. It has become. The ion entrance side slit 8 and the ion exit side slit 9 are electrode plates having pores that serve as ion entrances and exits in this system.

  Usually, the quadrupole of the quadrupole mass spectrometer is supplied with a DC voltage and a high-frequency voltage. In this case as well, a power source and a control system therefor are not shown, but are included as a configuration. . As an example of the electrode voltage supply of the quadrupole part, this basic one is shown in FIG. The same components as those in FIG. 3 are denoted by the same reference numerals.

  The electrodes K1 and K4 are commonly connected and supplied with Vo · cos (ωt + θ) + U1 + U2, and the electrodes K2 and K3 are connected together and supplied with −Vo · cos (ωt + θ) + U1−U2. Here, Vo is a high-frequency amplitude voltage value, ω is an angular frequency, t is time, θ is a phase, U1 is a DC voltage value for setting an axial potential, and U2 is a DC voltage value for a mass filter function. If the voltage of U2 is not supplied by cutting the supply circuit or if the value is set to 0, it can be used as an ion guide. Therefore, a configuration or control system capable of switching between the mass filter mode and the ion guide mode is incorporated. The voltage supply to the linear quadrupole 6 is configured to be switched. It should be noted that the ion entrance side slit 8 in the linear quadrupole portion may be used particularly as an ion guide. The operation of the apparatus configured as described above will be described as follows.

In the example shown in FIG. 9, the high frequency voltage Vrf1 (= ± Vo · cos (ωt + θ)) and the DC voltage Vdc1 (= ± U2) are applied to the linear quadrupole 6 and scanned at a constant voltage ratio. It is driven as a (mass analyzer), and a shaft voltage Vdc3 (= U1) for potential adjustment is also superimposed.

  The arc-shaped quadrupole 7 is mainly applied with the shaft voltage Vd2 and the high-frequency voltage Vrf2. Since the high-frequency voltage Vrf1 and the high-frequency voltage Vrf2 are often the same, the high-frequency power supply can be the same, or can be used in different settings, and may be a separate power supply. The inlet voltage Vdc_in and the outlet voltage Vdc_out are also applied to the ion inlet side slit 8 and the ion outlet side slit 9, respectively.

  Under this condition, when ions are introduced from the ion entrance slit 8 into the system, they proceed while vibrating in the radial direction with a high frequency voltage, reach the ion exit slit 9 and proceed to the detector. In the case of the linear quadrupole 6, when the mode is switched and used as a mass filter instead of an ion guide, only ions of a specific mass can be obtained by mass selection according to the conditions set in the quadrupole field. Can pass through the system, and otherwise, the vibration amplitude in the radial direction becomes large and deviates from the optical axis, so that it cannot pass through the system and is eliminated.

  FIG. 12 shows the simulation model and the ion trajectory superimposed. The ion trajectory is shown by a thin solid line. In order to make the operation easy to see, only the ion trajectory is taken out and shown in FIGS. FIG. 13 shows a simulation in which the initial incident conditions of ions having the same mass are changed, and FIG. 14 shows a simulation in which the initial conditions are changed including ions having different masses.

  In FIG. 13, even if the first straight part of the area that becomes the part of the linear quadrupole functioning as a mass filter can pass through, the mass filter of the subsequent straight part, in this case, the straight line that passes for the third time. It can be seen that the vibration amplitude is too large even in the region of and collides with the electrode surface in the middle of the system. In other words, it shows that the conditions for mass selection are becoming stricter.

  FIG. 14 shows a case where ions having a mass that does not match the conditions that allow passage are also ejected. Accordingly, it can be seen that not only the first linear region but also the second and third linear regions pass, the vibration amplitude becomes large on the way and the electrode surface collides and cannot pass. Again, this example shows that the conditions for mass selection are becoming stricter.

  The mass resolution of the quadrupole mass spectrometer is partly dependent on the frequency of the ions, so the frequency of the applied high-frequency voltage is increased or the linear quadrupole is lengthened. However, in practice, when the frequency is increased, the applied high-frequency voltage must be increased accordingly, and when the quadrupole is lengthened, if it is simply stretched linearly, the entire device becomes longer. Because it becomes, it is not practical.

  However, according to the present invention, the linear quadrupole 6 can be convoluted even if the length of the linear quadrupole 6 is lengthened. Therefore, the disadvantage that the apparatus becomes extremely long is reduced, and the mass resolution is improved. Therefore, if the number of times of folding is increased and the structure is expanded to the structure shown in FIG. 2 of Embodiment 1, the flight distance can be increased without increasing the size of the apparatus.

According to the third embodiment, the apparatus can be used both as a mass filter and as a time-of-flight mass spectrometer. Further, although the quadrupole electrode has a rod shape, it may have a hollow pipe shape, and the electrode cross-sectional shape is not necessarily circular. That is, it is sufficient if a quadrupole field can be formed, and it can be transformed into a hyperbola, a square, and the like.
(Fourth embodiment)
The fourth embodiment has the same external configuration as that shown in FIGS. The difference is the wiring of FIG. 15 with respect to FIG. In FIG. 15, SW is a switch for switching a voltage applied to the electrodes K1 to K4. + U2 is applied to one contact of the switch SW, and -U2 is applied to the other contact. It operates as a mass filter when the contact of the switch SW is closed, and operates as an ion guide when the contact of the switch SW is open. FIG. 11 shows a case where the filter is operated as a mass filter.
(Fifth embodiment)
In the arc-shaped quadrupole part of the ion guide function, when the rod-shaped electrode is arranged in four directions at an angle of 45 degrees, the orbit of the neutral particle passes through the gap of the electrode at the part where the orbit is bent. Adhesion / contamination to the electrode surface due to neutral particle components is reduced. Neutral particles that are not subjected to the deflection action in the electric field are separated from ions whose orbits are bent, so that unnecessary collision can be prevented and the noise can be reduced as a cause of noise to the detector. In addition, when arranged in the usual four directions of up, down, left, and right, three types of electrode rods are required as the basic shape in the bent portion of the arc-shaped quadrupole electrode rod. It can be composed of two types, an inner side and an outer side whose direction rotates.

The effects of the present invention described above are listed as follows.
1. Rather than connecting linearly by connecting a plurality of linear quadrupole mass filters or ion guides in an alternating manner, with the arc-shaped quadrupole part of the ion guide function in between. A small mass spectrometer that does not become too long linearly can be manufactured, and even a device that combines the functional parts of an ion guide and a linear quadrupole mass filter can be miniaturized.
2. By connecting multiple linear quadrupole mass filters, the length of the ion trajectory flying in the interior can be increased accordingly, and the greater the number of vibrations, the greater the mass resolution, thus improving the performance of the device. it can.
3. By connecting multiple linear quadrupoles, the length of the ion trajectory flying inside it can be increased accordingly, and when used in ion guide mode, the detector of ions flying in the quadrupole field can be used. Can be used as a time-of-flight mass spectrometer, and can be used in a composite type that operates as a mass filter by switching modes.
4). Since the rotation angle of the arcuate quadrupole portion used for the multi-stage connection of the linear quadrupole can be changed and set, the degree of freedom of the convolution can be provided, which is convenient from the viewpoint of manufacturing the device.

  As described above, according to the present invention, the resolution can be improved while taking advantage of the small size of the quadrupole type, and the data acquisition time for one measurement can be shortened to several milliseconds or less so that sampling can be performed. A device capable of improving simultaneity can be provided.

It is a figure which shows the apparatus structure outline | summary of this invention. It is a figure which shows the structural example of many times bending quadrupole. It is a figure which shows a quadrupole electrode cross section and the example of basic wiring. It is a figure which shows an ion locus example. It is a figure which shows the example which recorded the flight time of ion. It is a figure which shows a three-dimensional bending type | mold and a track | orbit superimposition figure. It is a figure which shows a plane bending type and an orbital superposition figure. It is a figure which shows an arc-shaped quadrupole part rotation radius and an orbital superposition figure. It is a figure which shows the whole optical system of a quadrupole. It is a figure which shows the projection of the whole optical system of a quadrupole. It is a figure which shows a linear type quadrupole part cross section and a basic wiring example. It is a figure which shows a quadrupole optical system and an ion orbit superimposition figure. It is a figure which shows ion trajectory figure 1. FIG. FIG. 3 is a diagram showing an ion trajectory diagram 2. It is a figure which shows the other example of the basic wiring of a linear quadrupole part cross section.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ion supply part 2 Ion reservoir or ion packetization part 3 Mass spectrometry field 4 Ion detection part 6 Linear type quadrupole 7 Arc type quadrupole 8 Ion entrance side electrode 9 Ion exit side electrode

Claims (6)

Integrated with a structure in which the electrode members are in contact with each other so that the optical axis on the ion optics is almost coincident with the quadrupole of the quadruple electrode set in a circular arc and the quadrupole of the linear electrode set of four. Or a configuration with a quadrupole shape in a connected state,
A multiflex quadrupole time-of-flight mass spectrometer characterized in that the quadrupole part functions as an ion guide and can measure the time of flight of flying ions.   The quadrupoles of four arcuate electrodes arranged in four directions at an angle of 45 degrees from the central axis and the quadrupoles of four linear electrodes are almost coincident with each other in the optical axis on the ion optics. In this structure, the electrode members are in contact with each other and have an integrated or connected quadrupole shape. This quadrupole part functions as an ion guide to measure the flight time of flying ions. A multi-bending type quadrupole time-of-flight mass spectrometer characterized in that it can be configured.   Change the number and combination of the quadrupoles of the quadrupole electrode bent in a circular arc and the quadrupoles of the linear electrode quadruple and the connection direction, and connect at least two linear quadrupole parts. 3. The multiflex quadrupole time-of-flight mass spectrometer according to claim 1, wherein the time of flight of ions is measured with the connection as described above.   In order to insulate the quadrupoles of the quadrupole electrode bent in a circular arc shape and the quadrupoles of the linear electrode quadrupole electrode so that the optical axes on the ion optics are substantially coincident with each other at the connection portion. The quadrupole part of the set of four linear electrodes can be applied with a voltage different from that of the arc-like part by switching the electric circuit. It can be used as a filter, and the mode of either the state where the entire quadrupole part can function as an ion guide and the time of flight of ions can be measured or the state where mass analysis can be performed as a mass filter is required. 4. The multi-bending quadrupole time-of-flight mass spectrometer according to claim 3, wherein switching is performed.   5. The multi-bending quadrupole time-of-flight mass spectrometer according to claim 4, wherein the radius of rotation of the optical axis of the arcuate electrode assembly is within 10 times the diameter of the electrode.   6. The multi-bending quadrupole time-of-flight mass spectrometer according to claim 5, wherein the electrode is rod-shaped or pipe-shaped.

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