JP7109026B2 - ion analyzer - Google Patents

Description

The present invention relates to an ion analyzer.

In order to identify a polymer compound or analyze its structure, ions derived from a polymer compound (precursor ion) are dissociated one or more times to generate product ions (also called fragment ions), which are then converted into Mass spectrometry, which separates and detects according to mass-to-charge ratio, is widely used. Collision-induced dissociation (CID) is known as a representative method for dissociating ions in mass spectrometry, in which ions are collided with inert gas molecules such as nitrogen gas. In the CID method, ions are dissociated by collision energy with inert molecules, so various ions can be dissociated, but the selectivity of the ion dissociation position is low. Therefore, the CID method is unsuitable when it is necessary to dissociate ions at specific sites for structural analysis. For example, when analyzing peptides, etc., it is desired to specifically dissociate at the binding position of amino acids, which is difficult with the CID method.

Ion dissociation methods that specifically dissociate peptides at amino acid binding sites have traditionally been the electron transfer dissociation (ETD) method, in which precursor ions are bombarded with negative ions, and the electron capture method, in which precursor ions are bombarded with electrons. Dissociation (ECD: Electron Capture Dissociation) method is used. These are called unpaired electron-induced dissociation methods, which dissociate the N-Cα bond of the peptide main chain to generate c/z series product ions.

In the ETD method and ECD method, if the precursor ion is a positive ion, the valence of the ion decreases during dissociation. That is, neutral molecules are produced when monovalent positive ions are dissociated. Therefore, only positive ions with a valence of 2 or more can be analyzed. Therefore, the ETD method and ECD method are not suitable for combination with the MALDI method, which generates many monovalent positive ions.

The present inventors have proposed a hydrogen attachment/abstraction dissociation (HAD) method that causes unpaired electron-induced dissociation by irradiating hydrogen radicals to peptide-derived precursor ions (Patent Reference 1). Since the HAD method dissociates without changing the valence of the precursor ion, it is suitable for combination with the MALDI method. The HAD method can also generate c/z series product ions.

The present inventors have also proposed to specifically dissociate peptide-derived precursor ions at amino acid binding sites by using hydroxyl radicals, oxygen radicals, or nitrogen radicals (Patent Document 2). When precursor ions derived from these peptides are irradiated with radicals, a/x series product ions and b/y series product ions are generated.

WO2015/133259 WO2018/186286

Yuji Shimabukuro, Hidenori Takahashi, Shinichi Iwamoto, Koichi Tanaka, Motoi Wada, "Tandem Mass Spectrometry of Peptide Ions by Microwave Excited Hydrogen and Water Plasmas", Analytical Chemistry 2018, 90 (12) pp. 7239-7245 U. Fantz and D. Wunderlich, "A novel diagnostic technique for H-(D-) densities in negative hydrogen ion sources", New J. Phys., 8, 301 (2006).

The reaction efficiency between precursor ions and radicals varies depending on the energy possessed by the radicals. The energy possessed by radicals is mainly kinetic energy possessed by the radicals, and can be represented by the radical temperature. A sufficient reaction does not occur even if precursor ions are irradiated with radicals having a low radical temperature. The present inventors have reported in Non-Patent Document 1 that hydrogen radicals generated by an electron cyclotron resonance (ECR)-inductively coupled plasma (ICP) source are irradiated to peptide-derived precursor ions. They reported that sufficient dissociation did not occur, and considered that the cause was that the radical temperature of the radical irradiated to the peptide was not sufficient to dissociate the precursor ion derived from the peptide.

Here, the case of performing mass spectrometry on product ions generated by irradiating radicals to dissociate precursor ions was explained as an example, but the same problem as described above applies to the case of separating and measuring product ions according to their ion mobility. was there.

The problem to be solved by the present invention is to provide an ion analyzer capable of irradiating precursor ions derived from a sample component with radicals at a temperature sufficient to dissociate the precursor ions.

The present invention, which has been made to solve the above problems, is an ion analyzer for analyzing product ions generated by irradiating precursor ions derived from a sample component with radicals,
a reaction chamber into which the precursor ion is introduced;
a radical generation chamber;
a raw material gas supply source for supplying raw material gas to the radical generation chamber;
a first power supply unit that supplies high-frequency power of a first frequency for generating radicals and charged particles from the raw material gas in the radical generation chamber;
a radical transport path for transporting the radicals to the reaction chamber;
a second power supply unit that supplies high-frequency power having a second frequency lower than the first frequency for exciting the charged particles in the radical generation chamber and/or the radical transport path;
a control unit that operates a second power supply unit at the same time as the first power supply unit or with a delay of a predetermined time from the first power supply unit;
a separation detection unit that separates and detects product ions generated in the reaction chamber according to at least one of mass-to-charge ratio and ion mobility.

The high-frequency power of the first frequency may be supplied by applying a high-frequency voltage to electrodes provided in the radical generation chamber, or a high-frequency power may be supplied to a coil wound around the outer peripheral surface of a member constituting the radical generation chamber. You may perform by sending an electric current. The high-frequency power of the second frequency may be similarly supplied by applying a high-frequency voltage to the electrodes provided in the radical generation chamber and/or the radical transport path, or alternatively, the radical generation chamber and/or the radical transport path. may be performed by passing a high-frequency current through a coil wound around the outer peripheral surface of a member that constitutes .

In the ion analyzer according to the present invention, first, a source gas is supplied to the radical generation chamber, and high-frequency power of a first frequency is supplied to generate radicals from the source gas. At this time, not only radicals but also charged particles (ions and electrons) are generated from the source gas. In the ion analyzer according to the present invention, in addition to this, the ions are excited by supplying the high-frequency power of the second frequency to increase the kinetic energy. By coupling electrons to ions with increased kinetic energy in this way, radicals with high kinetic energy (radicals with high radical temperature) are generated. Ion excitation can be performed in the radical generation chamber and/or the radical transport channel. When ions are to be excited in the radical generation chamber, the second power supply section should be operated simultaneously with or slightly later than the first power supply section. In addition, when ions are excited in the radical transport path, the first electric power supply unit is delayed by a predetermined time, specifically at the timing when the charged particles generated in the radical generation chamber reach the radical transport path. 2 power supply units should be operated. As a result, precursor ions derived from the sample component can be irradiated with radicals at a temperature sufficient to dissociate the precursor ions.

1 is a schematic configuration diagram of an ion trap-time-of-flight mass spectrometer that is an embodiment of an ion analyzer according to the present invention; FIG. FIG. 2 is a structural diagram of radicals of a radical source and its surroundings in the mass spectrometer of the present embodiment. The emission spectrum of hydrogen radicals generated using the mass spectrometer of this example and the emission spectrum of a comparative example. Mass spectra obtained by irradiating fullerene ions with hydrogen radicals generated using the mass spectrometer of this example and mass spectra of a comparative example.

An embodiment of an ion analyzer according to the present invention will be described below with reference to the drawings. The ion analyzer of this embodiment is an ion trap-time-of-flight (IT-TOF) mass spectrometer.

FIG. 1 shows a schematic configuration of an ion trap-time-of-flight mass spectrometer (hereinafter also simply referred to as “mass spectrometer”) of this embodiment. The mass spectrometer of this embodiment comprises an ion source 1 for ionizing components in a sample and trapping ions generated by the ion source 1 by the action of a high-frequency electric field inside a vacuum chamber (not shown) maintained in a vacuum atmosphere. a time-of-flight mass separator 3 for separating ions emitted from the ion trap 2 according to their mass-to-charge ratio; and an ion detector 4 for detecting the separated ions. The ion trap mass spectrometer of this embodiment further includes a radical generation/irradiation unit 5 for generating radicals from the raw material gas and irradiating the ions trapped in the ion trap 2, an inert gas supply unit 6, a trap A voltage generation unit 7 and a control/processing unit 8 are provided. A control/processing unit 8 controls the operation of each unit described above.

As the ion source 1 of the mass spectrometer of this embodiment, an ion source of a type suitable for ionizing sample components, such as an ESI source or a MALDI ion source, is used. The ion trap 2 of this embodiment comprises a ring-shaped ring electrode 21 and a pair of end cap electrodes (an entrance side end cap electrode 22 and an exit side end cap electrode 24) arranged to face each other with the ring electrode 21 interposed therebetween. is a three-dimensional ion trap containing A radical particle inlet 26 and a radical particle outlet 27 are formed in the ring electrode 21, an ion introduction hole 23 is formed in the inlet side end cap electrode 22, and an ion emission hole 25 is formed in the outlet side end cap electrode 24, respectively. there is The trap voltage generator 7 applies a high-frequency voltage and a DC voltage to each of the ring electrode 21, the entrance-side endcap electrode 22, and the exit-side endcap electrode 24 at predetermined timings according to instructions from the control/processing unit 8. Either one of or a voltage obtained by combining them is applied.

The radical generation/irradiation unit 5 includes a radical source 54 in which a radical generation chamber 51 is formed, a vacuum pump (vacuum exhaust unit) 57 that exhausts the radical generation chamber 51, and a gas that serves as a raw material for radicals (raw material gas). and a high-frequency power supply unit 53 . The high-frequency power supply unit 53 includes a first high-frequency power supply 531 that supplies high-frequency power of a first frequency, and a second high-frequency power supply 532 that supplies high-frequency power of a second frequency (see FIG. 2). A valve 56 for adjusting the flow rate of the source gas is provided in the flow path from the source gas supply source 52 to the radical generation chamber 51 .

In this embodiment, the radical generation/irradiation unit 5 generates hydrogen radicals. For example, hydrogen gas, water vapor (water), or ammonia gas can be used as the raw material gas for generating hydrogen radicals. When hydrogen gas is used as the raw material gas, hydrogen radicals with high purity can be generated. Moreover, when water vapor is used as the raw material gas, its handling is safe and simple. Furthermore, when ammonia gas is used as the raw material gas, hydrogen molecules can be separated from the ammonia molecules, and many hydrogen radicals can be generated from the hydrogen molecules.

The configuration of the radical source 54 and its surroundings will be described with reference to the cross-sectional view of FIG. The radical source 54 has a tubular body 541 made of a dielectric such as alumina (for example, aluminum oxide, quartz, aluminum nitride), and the inner space thereof serves as the radical generation chamber 51 . The tubular body 541 is fixed by a plunger 545 while being inserted inside a hollow cylindrical magnet 544 . A first spiral antenna 542 (broken line in FIG. 2) is wound around the outer periphery of a portion of the tubular body 541 located inside the magnet 544 . Of the tubular body 541, the region inside the portion where the first spiral antenna 542 is wound corresponds to the radical generation chamber in the present invention, and the region on the tip side (left side in FIG. 2) than it corresponds to the region in the present invention. Corresponds to the radical transport pathway. The first spiral antenna 542 of this embodiment is a conductive coil (made of tungsten, for example) wound 15 times. A second spiral antenna 543 (broken line in FIG. 2) is wound around the outer periphery of the tubular body 541 toward the distal end (left side in FIG. 2) of the first spiral antenna 542 . The second spiral antenna 543 of this embodiment is a conductive coil (made of, for example, tungsten) wound around 20 times. The material and number of turns of the first spiral antenna 542 and the second spiral antenna 543 are examples, and can be changed as appropriate.

In addition, the radical source 54 is provided with a high-frequency power input section 546 . Two systems of high-frequency power are supplied to the high-frequency power supply unit 546 from the high-frequency power supply unit 53 (the first high-frequency power supply 531 and the second high-frequency power supply 532). The high-frequency power of the first frequency supplied from the first high-frequency power supply 531 is supplied to the first spiral antenna 542 , and the high-frequency power of the second frequency supplied from the second high-frequency power supply 532 is supplied to the second spiral antenna 543 .

Furthermore, the radical source 54 has a flange 547 for fixing the tip portion of the radical source 54 inserted into the intermediate vacuum chamber 59 . A hollow cylindrical magnet 548 having the same diameter as the magnet 544 and forming a pair with the magnet 544 is housed inside the flange 547 . The magnets 544 and 548 are not essential, but they generate a magnetic field inside the tubular body 541 (radical generation chamber 51), and their action facilitates the generation and maintenance of plasma.

After being evacuated by a vacuum pump 57, the radical generation chamber 51 is supplied with a predetermined amount of raw material gas. The supply amount of the raw material gas is such that the pressure in the radical generation chamber 51 becomes 0.01 to 1 Pa, for example. On the other hand, the inside of the ion trap 2 is usually maintained at an ultra-high vacuum of about 10 ^-3 Pa. The intermediate vacuum chamber 59 is maintained at the intermediate pressure. A skimmer 55 is provided between the intermediate vacuum chamber 59 and the ion trap 2 to maintain the pressure difference between them. A deflection section 58 is provided between the exit end of the radical source 54 and the skimmer 55 in the intermediate vacuum chamber 59 . The deflection unit 58 of this embodiment has two plate electrodes arranged opposite to each other, and a positive voltage is applied to one plate electrode and a negative voltage is applied to the other plate electrode from a power source (not shown). As a result, charged particles emitted from the radical source 54 are deflected by the action of the electric field formed in the deflection section 58 . Note that the deflecting unit may have any structure as long as it deflects charged particles, and may have an appropriate configuration such as forming a magnetic field instead of an electric field.

The inert gas supply unit 6 supplies one or more types of inert gas (nitrogen gas, helium gas, argon gas, etc.) into the ion trap 2 . These inert gases are used to cool the ions introduced into the ion trap 2 and to collide with the ions introduced into the ion trap 2 to dissociate the ions.

Next, the analysis operation of the mass spectrometer of this embodiment will be described by taking the case of analyzing a peptide mixture as an example. Before starting the analysis, the ion source 1 (except for the atmospheric pressure ion source), the ion trap 2, the vacuum chamber housing the time-of-flight mass separation unit 3, the intermediate vacuum chamber 59, and the radical generation chamber 51 are each evacuated. It is evacuated to a predetermined degree of vacuum by a pump (only the vacuum pump 57 is shown, the others are not shown).

Subsequently, the ion source 1 ionizes the sample component (peptide mixture). Ions generated by the ion source 1 are emitted from the ion source 1 in packets and introduced into the ion trap 2 through an ion introduction hole 23 formed in an entrance-side end cap electrode 22 . Ions derived from sample components introduced into the ion trap 2 are trapped by a high-frequency electric field formed inside the ion trap 2 by a voltage applied from the trap voltage generator 7 to the ring electrode 21 . After that, a predetermined voltage is applied from the trapping voltage generator 7 to the ring electrode 21, etc., thereby reducing the mass-to-charge of ions other than ions having a specific mass-to-charge ratio (or a mass-to-charge ratio within a specific mass-to-charge ratio range). Ions are excited and ejected from the ion trap 2 . Thereby, precursor ions having a specific mass-to-charge ratio (or a mass-to-charge ratio within a specific range of mass-to-charge ratios) are selectively trapped within the ion trap 2 .

Subsequently, the valve 62 of the inert gas supply unit 6 is opened to introduce an inert gas such as helium gas into the ion trap 2 from the inert gas supply source 61 . This cools the precursor ions and converges them near the center of the ion trap 2 .

In parallel with the ionization of the sample components and their trapping in the ion trap 2, radicals are generated as follows.

First, the valve 56 is opened to supply the raw material gas from the raw material gas supply source 52 to the inside of the tubular body 541 (radical generation chamber 51). Also, high-frequency power of the first frequency is supplied from the first high-frequency power supply 531 to the first spiral antenna 542 through the high-frequency power supply unit 546 . The first frequency in this embodiment is 2.45 GHz (microwave). By supplying high-frequency power of the first frequency to the first spiral antenna 542, vacuum discharge is generated inside the tubular body 541 (radical generation chamber 51), and radicals and charged particles (ions and electrons) are generated from the source gas. be done. The generated radicals and charged particles are drawn toward the intermediate vacuum chamber 59 by the pressure difference between the radical generation chamber 51 and the intermediate vacuum chamber 59 and move.

Simultaneously with the supply of the high frequency power of the first frequency to the first spiral antenna 542 or with a slight delay, the high frequency power of the second frequency is supplied from the second high frequency power supply 532 to the second spiral antenna 543 . The second frequency in this embodiment is 13.56 MHz (radio waves). The control/processing unit 8 controls the timing of the supply of the high frequency power of the first frequency from the first high frequency power supply 531 and the supply of the high frequency power of the second frequency from the second high frequency power supply 532 .

By supplying the high-frequency power of the second frequency to the second spiral antenna 543 , an electric field having a predetermined potential difference and oscillating at a frequency of 13.56 MHz is formed inside the tubular body 541 , toward the intermediate vacuum chamber 59 . The moving ions are excited and their kinetic energy is increased. Ions with increased kinetic energy combine with electrons to generate radicals with high kinetic energy (radical temperature is high). Also, ions with increased kinetic energy collide with radicals generated by vacuum discharge, and part of the kinetic energy of the ions is transferred to the radicals, which can also raise the temperature of the radicals. Thus, hot radicals are generated. Hot radicals leave the exit end of the radical source 54 and pass through the skimmer 55 to be irradiated into the ion trap 2 .

As described above, not only radicals but also charged particles (ions and electrons) are generated in the radical generation chamber 51 . Some of the ions are radicalized by bonding with electrons, but the remaining ions and electrons are emitted from the radical source 54 together with the radicals. When the charged particles emitted from the radical source 54 reach the deflection section 58 , they are deflected by the action of the electric field formed in the deflection section 58 . On the other hand, since the radicals are neutral particles, they pass through the skimmer 55 without being deflected by the deflector 58 and are irradiated into the ion trap 2 . This prevents ions and electrons from irradiating precursor ions trapped in the ion trap 2 and causing undesired reactions and dissociation.

The opening degree of the valve 56 in the radical generation/irradiation unit 5 is maintained at a constant state, and ions are irradiated with a predetermined flow rate of radicals. Also, the irradiation time of radicals to precursor ions is set appropriately. Depending on the irradiation time, the valve 56 is opened or closed, or the supply of power of the first frequency is started/stopped. The degree of opening of the valve 56 and the irradiation time of radicals can be determined in advance based on the results of preliminary experiments and the like. Radical irradiation causes unpaired electron-induced dissociation of precursor ions to generate peptide-derived product ions. Various product ions generated are trapped in the ion trap 2 and cooled by inert gas such as nitrogen gas supplied from the inert gas supply unit 6 . After that, a DC voltage is applied from the trapping voltage generator 7 to the entrance-side end cap electrode 22 and the exit-side end cap electrode 24 at a predetermined timing. receive acceleration energy and are ejected all at once through the ion ejection aperture 25 . The product ions generated here can include both fragment ions and adduct ions.

In this way, product ions having constant acceleration energy are introduced into the flight space of the time-of-flight mass separator 3 , separated according to the mass-to-charge ratio while flying in the flight space, and enter the ion detector 4 . The ion detector 4 sequentially detects ions and outputs detection signals to the control/processing unit 8 . The control/processing unit 8 creates, for example, a time-of-flight spectrum in which the time at which ions are ejected from the ion trap 2 is zero. Then, a product ion spectrum is created by converting the time-of-flight into a mass-to-charge ratio using mass calibration information prepared in advance. The control/processing unit 8 performs predetermined data processing based on the information (mass information) obtained from this mass spectrum to identify the sample component (peptide mixture). Among the product ions, the partial structure of the peptide can be determined from the mass-to-charge ratio of the fragment ions. In this example, since hydrogen radicals are irradiated, the N-Cα bond of the peptide main chain can be dissociated to selectively generate c/z series product ions.

In the conventional ion analyzer, even if precursor ions trapped in the ion trap 2 are irradiated with radicals generated by inductively coupled vacuum discharge in the radical generation/irradiation unit 5, a sufficient dissociation reaction occurs because the radical temperature is low. could not be generated. When radicals are generated by capacitively coupled vacuum discharge, it is possible to generate higher temperature radicals than by inductively coupled vacuum discharge. The radical temperature will drop due to adhesion.

On the other hand, in the mass spectrometer of the above-described embodiment, ions generated together with radicals in the radical generation chamber 51 are excited to increase their kinetic energy, and coupled with electrons to generate high-temperature radicals. In the above embodiment, ions are excited at a position near the radical generation chamber 51. However, if the transport path from the radical generation chamber 51 to the ion trap 2 is long, a position near the ion trap 2 or at a position near the ion trap 2 may be used to generate radicals. It can be configured to excite ions in all or part of the transport path from the chamber 51 to the ion trap 2 to generate high-temperature radicals. Therefore, there is no need to shorten the radical transport path, and the degree of freedom in arranging the radical source 54 can be increased.

Next, a description will be given of the results of measurements for confirming the effect of raising the temperature of radicals by supplying two systems of high-frequency power to the radical source 54 of the ion analyzer of the above embodiment.

In this measurement, a transparent window is provided on the wall surface of the intermediate vacuum chamber 59, hydrogen gas of 0.1 Pa is supplied to the radical generation chamber 51, and high frequency power of the first frequency (2.45 GHz, 10 W ) and the high-frequency power of the second frequency (13.56 MHz, 100 W) were both supplied, and the emission spectrum of hydrogen radicals was measured. For comparison, the emission spectrum was also measured in the case of supplying only the high-frequency power (2.45 GHz, 10 W) of the first frequency (comparative example) as in the conventional case.

FIG. 3 shows the measurement results. Three peaks were confirmed in the emission spectrum of this example, and two peaks were confirmed in the emission spectrum of the comparative example. These peaks are the Balmer alpha line (656.28 nm), the Balmer beta line (486.13 nm), and the Balmer gamma (434.05 nm) in order from the long wavelength side. Balmer gamma (434.05 nm) was confirmed only in the emission spectrum of this example. The intensity of each peak reflects the amount of hydrogen radicals having internal energy equal to or higher than the energy corresponding to the light of each wavelength. The distribution of the magnitude of the internal energy of hydrogen radicals depends on the radical temperature, and the higher the radical temperature, the shorter the Balmer line appears. Since the peak of Balmer gamma (434.05 nm) is confirmed only in the emission spectrum of this example, it can be seen that hydrogen radicals of higher temperature were generated in this example than in the comparative example.

Moreover, the radical temperature can be estimated from the ratio of the intensity of the Balmer α-ray and the intensity of the Balmer β-ray. In this example, the ratio (Balmer α-ray intensity/Balmer β-ray intensity) is about 4.08 times, while in the comparative example, this ratio is about 6.36 times. Since the higher the ratio, the lower the temperature (for example, Non-Patent Document 2), it can be seen that in this example, the radicals were generated at a higher temperature than in the conventional example (comparative example). Also, from the comparison of peak intensities, it can be seen that the amount of generated radicals has also increased compared to the conventional case.

Next, measurement results confirming an increase in the amount of radicals produced by supplying two systems of high-frequency power to the radical source 54 of the ion analyzer of the above embodiment will be described.

In this measurement, hydrogen radicals generated by supplying both high-frequency power of the first frequency (2.45 GHz, 10 W) and high-frequency power of the second frequency (13.56 MHz, 100 W) were irradiated to precursor ions derived from fullerenes, A spectrum of the product ions produced (product ion spectrum) was measured. Also, for comparison, a mass spectrum was measured by irradiating hydrogen radicals by supplying only the high-frequency power of the first frequency (2.45 GHz, 10 W) (comparative example). Furthermore, for reference, the mass spectrum of fullerene ions was measured without supplying high-frequency power (reference example).

FIG. 4 shows the measurement results. The upper stage is the mass spectrum of the reference example, the middle stage is the mass spectrum of the comparative example, and the lower stage is the mass spectrum of the present example. The upper reference example is a mass spectrum of fullerene ions themselves generated by the ion source 1 without supplying high-frequency power. The radical addition reaction of fullerenes is an exothermic reaction. In other words, the energy threshold of the radical addition reaction is 0, and all the radicals irradiated to the precursor ions derived from fullerenes adhere. can be estimated.

In the mass spectrum of the comparative example, the center of gravity of the spectrum is shifted by about +7 to the high mass-to-charge ratio side compared to the mass spectrum of the reference example. On the other hand, in the mass spectrum of this example, the center of gravity of the spectrum is shifted by about +27 to the higher mass-to-charge ratio side compared to the mass spectrum of the reference example. Thus, it can be seen that the use of the ion analyzer of this example not only increased the radical temperature, but also significantly increased the amount of generated radicals.

The embodiment described above is an example, and can be appropriately modified in accordance with the gist of the present invention.

The numerical values of 2.45 GHz as the first frequency and 13.56 MHz as the second frequency in the present embodiment are merely specific examples set in consideration of restrictions by the Radio Law, etc., and can be changed as appropriate. The first frequency may be any frequency that can cause vacuum discharge in the radical generation chamber, preferably a frequency higher than 100 MHz, and more preferably a frequency higher than 1 GHz. On the other hand, the second frequency may be any frequency that can excite ions, and may be an appropriate frequency of 100 MHz or less, for example. Considering only the excitation of ions, a low frequency is more advantageous, but the wavelength becomes longer at a lower frequency, and it becomes necessary to secure a large space in order to generate a sufficient potential difference to excite the ions. the size of the device increases. Considering this point, the second frequency is preferably 400 kHz or higher, and more preferably 2 MHz or higher. Further, in the above-described embodiment, power of two different frequencies is supplied, but power of three or more different frequencies may be supplied. For example, as will be described later, oxygen ions, nitrogen ions, and hydroxy ions are generated when air is used as the source gas. In such a case, a plurality of types of ions can be excited by combining powers of different frequencies according to the mass-to-charge ratio of the ions.

In the above embodiment, high-frequency power of the first frequency is supplied to the first spiral antenna 542 wound around the outer periphery of the radical generation chamber 51, and the second spiral antenna wound further downstream (on the ion trap 2 side). 543 is configured to supply high-frequency power of the second frequency, but one spiral antenna that is common to both the first spiral antenna 542 and the second spiral antenna 543 is used, and the spiral antenna is supplied with the high-frequency power of the first frequency. High-temperature radicals can also be generated in the same manner as described above by supplying superimposed power and high-frequency power of the second frequency.

In the above embodiment, the radical source 54 configured to generate hydrogen radicals by inductively coupled vacuum discharge was used in the radical generation/irradiation unit 5. However, the radical source configured as proposed by the present inventor in Patent Document 2 is used. It is also possible to employ a configuration in which radicals are generated by capacitively coupled vacuum discharge. In this case as well, the same effect as in the above embodiment can be obtained by supplying the high frequency power of the first frequency and the high frequency power of the second frequency.

In the above embodiment, the case of generating hydrogen radicals has been described as an example, but the mechanism of generating high-temperature radicals is the same for other kinds of radicals. Accordingly, the same configuration as described above can be employed when generating and irradiating other types of radicals such as hydroxyl radicals, oxygen radicals, nitrogen radicals, and the like. Hydroxyl radicals, oxygen radicals, and hydrogen radicals can be generated by using water vapor as the source gas. By using air as the raw material gas, it is possible to mainly generate oxygen radicals and nitrogen radicals. Furthermore, oxygen radicals can be generated by using oxygen gas as the raw material gas. In addition, nitrogen radicals can be generated by using nitrogen gas as the raw material gas. As in the above example, by irradiating the peptide-derived precursor ions with hydrogen radicals, c/z series product ions can be generated. Product ions of a/x series and b/y series can be generated by irradiating ions.

In the above embodiment, an ion trap-time-of-flight mass spectrometer equipped with a three-dimensional ion trap is used. It can also be configured to irradiate radicals at . Further, in the above embodiments and modified examples, the time-of-flight mass separator is of the linear type, but a time-of-flight mass separator such as a reflectron type or a multi-turn type may be used. In addition to the time-of-flight mass separator, it is also possible to use other types of mass separators, such as those that perform mass separation using the ion separation function of the ion trap 2 itself, or an orbitrap.

In the above embodiments, a mass spectrometer that separates and detects ions according to their mass-to-charge ratio has been described. The same radical generation/irradiation unit 5 as in the above embodiment can also be used in an apparatus that separates ions according to both mobilities.

[Aspect]
It will be appreciated by those skilled in the art that the multiple exemplary embodiments described above are specific examples of the following aspects.

(First aspect)
A first aspect of the present invention is an ion analyzer for analyzing product ions generated by irradiating precursor ions derived from a sample component with radicals,
a reaction chamber into which the precursor ion is introduced;
a radical generation chamber;
a raw material gas supply source for supplying raw material gas to the radical generation chamber;
a first power supply unit that supplies high-frequency power of a first frequency for generating radicals and charged particles from the raw material gas in the radical generation chamber;
a radical transport path for transporting the radicals to the reaction chamber;
a second power supply unit that supplies high-frequency power having a second frequency lower than the first frequency for exciting the charged particles in the radical generation chamber and/or the radical transport path;
a control unit that operates a second power supply unit at the same time as the first power supply unit or with a delay of a predetermined time from the first power supply unit;
a separation detection unit that separates and detects product ions generated in the reaction chamber according to at least one of mass-to-charge ratio and ion mobility.

The high-frequency power of the first frequency may be supplied by applying a high-frequency voltage to electrodes provided in the radical generation chamber, or a high-frequency power may be supplied to a coil wound around the outer peripheral surface of a member constituting the radical generation chamber. You may perform by supplying an electric current. The high-frequency power of the second frequency may be similarly supplied by applying a high-frequency voltage to the electrodes provided in the radical generation chamber and/or the radical transport path, or alternatively, the radical generation chamber and/or the radical transport path. may be performed by supplying a high-frequency current to a coil wound around the outer peripheral surface of a member that constitutes .

In the ion analyzer of the first aspect, first, a source gas is supplied to the radical generation chamber, and a high-frequency voltage of a first frequency is applied to generate radicals from the source gas. At this time, not only radicals but also charged particles (ions and electrons) are generated from the source gas. In the ion analyzer according to the present invention, the ions are excited by supplying the high-frequency power of the second frequency to increase the kinetic energy. By coupling electrons to the ions whose kinetic energy has been raised in this way, radicals with high kinetic energy (radicals with high radical temperature) are generated. Ion excitation can be performed in the radical generation chamber and/or the radical transport channel. When ions are to be excited in the radical generation chamber, the second power supply section should be operated simultaneously with or slightly later than the first power supply section. Further, when ions are excited in the radical transport path, the charged particles generated in the radical generation chamber by the first power supply section after a predetermined time delay from the first power supply section are transferred to the radical transport path. The second power supply unit may be operated at the timing of arrival. As a result, precursor ions derived from the sample component can be irradiated with radicals at a temperature sufficient to dissociate the precursor ions.

(Second aspect)
The ion analyzer of the second aspect of the present invention is the ion analyzer of the first aspect,
moreover,
A vacuum evacuation unit for evacuating the radical generation chamber,
A vacuum discharge is generated in the radical generation chamber by supplying the high-frequency power of the first frequency.

The ion analyzer of the second aspect generates radicals and charged particles by vacuum discharge. Under vacuum (low pressure), the amount of neutral particles (atoms and molecules) in the radical generation chamber is small, so the ions whose kinetic energy has been increased by excitation collide with these neutral particles, resulting in a decrease in energy. can be prevented, and high-temperature radicals can be efficiently generated. In addition, it is possible to suppress the recombination of the generated radicals with the neutral particles and disappear, thereby increasing the utilization efficiency of the radicals.

(Third aspect)
An ion analyzer according to a third aspect of the present invention is the ion analyzer according to the second aspect,
The vacuum discharge is of the inductive coupling type.

In the ion analyzer of the third aspect, radicals and charged particles are generated by inductively coupled vacuum discharge. In the inductively coupled discharge system, the antenna for power supply can be installed outside the vacuum system, so it is possible to prevent the contamination of metal impurities originating from the electrodes and to greatly extend the life of the antenna. Furthermore, the density of electrons is higher than that of the capacitive coupling type, and thus the density of generated radicals is also higher.

(Fourth mode)
An ion analyzer according to a fourth aspect of the present invention is the ion analyzer according to any one of the first to third aspects,
The first frequency is greater than 100MHz and the second frequency is less than or equal to 100MHz.

Depending on the configuration of the radical source, by setting the first frequency to be higher than 100 MHz and the second frequency to be 100 MHz or less, radicals and A charged particle is generated, and high-temperature radicals can be generated by exciting the charged particle by supplying high-frequency power of the second frequency.

(Fifth aspect)
An ion analyzer according to a fifth aspect of the present invention is the ion analyzer according to any one of the first to fourth aspects,
The raw material gas is of a type that generates at least hydrogen radicals when supplied with the high-frequency power of the first frequency.

The ion analyzer of the fifth aspect can be suitably used to dissociate the N-Cα bond of the peptide main chain to generate c/z series product ions. Further, hydrogen ions, which are the source of hydrogen radicals, are the lightest ions and are easily excited, so that the second frequency can be set high and the size of the device can be reduced.

(Sixth aspect)
An ion analyzer according to a sixth aspect of the present invention is the ion analyzer according to the fifth aspect,
The raw material gas is hydrogen gas, water vapor, or ammonia gas.

In the ion analyzer of the sixth aspect, hydrogen radicals with high purity can be generated when the source gas is hydrogen gas. Moreover, when the raw material gas is water vapor, the raw material gas can be handled safely. Furthermore, when the raw material gas is ammonia gas, hydrogen can be released from ammonia molecules to generate many hydrogen radicals.

(Seventh aspect)
An ion analyzer according to a seventh aspect of the present invention is the ion analyzer according to any one of the first to sixth aspects,
A deflection section for deflecting the charged particles is provided between the radical transport path and the reaction chamber.

In the ion analyzer of the seventh aspect, only the radicals can be introduced into the reaction chamber by changing the traveling direction of the charged particles with the deflection section.

DESCRIPTION OF SYMBOLS 1... Ion source 2... Ion trap 21... Ring electrode 22... Entrance side end cap electrode 23... Ion introduction hole 24... Exit side end cap electrode 25... Ion injection hole 26... Radical particle inlet 27... Radical particle outlet 3... Time-of-flight mass separation unit 4 Ion detector 5 Radical generation/irradiation unit 51 Radical generation chamber 52 Source gas supply source 53 High-frequency power supply unit 531 First high-frequency power source 532 Second high-frequency power source 54 Radical Source 541 Tubular body 542 First spiral antenna 543 Second spiral antenna 544, 548 Magnet 545 Plunger 546 High frequency power input unit 547 Flange 55 Skimmer 56 Valve 57 Vacuum pump 58 Deflecting unit 59... Intermediate vacuum chamber 6... Inert gas supply unit 61... Inert gas supply source 62... Valve 7... Trap voltage generation unit 8... Control/processing unit

Claims (7)

An ion analyzer for analyzing product ions generated by irradiating precursor ions derived from sample components with radicals,
a reaction chamber into which the precursor ion is introduced;
a radical generation chamber;
a raw material gas supply source for supplying raw material gas to the radical generation chamber;
a first power supply unit that supplies high-frequency power of a first frequency for generating radicals and charged particles from the raw material gas in the radical generation chamber;
a radical transport path for transporting the radicals to the reaction chamber;
a second power supply unit that supplies high-frequency power having a second frequency lower than the first frequency for exciting the charged particles in the radical generation chamber and/or the radical transport path;
a control unit that operates a second power supply unit at the same time as the first power supply unit or with a delay of a predetermined time from the first power supply unit;
A separation detection unit that separates and detects product ions generated in the reaction chamber according to at least one of mass-to-charge ratio and ion mobility. moreover,
A vacuum evacuation unit for evacuating the radical generation chamber,
2. The ion analyzer according to claim 1, wherein a vacuum discharge is generated in said radical generation chamber by supplying high-frequency power of said first frequency. 3. The ion analyzer of claim 2, wherein said vacuum discharge is of the inductively coupled type. 4. The ion analyzer according to any one of claims 1 to 3, wherein said first frequency is higher than 100MHz and said second frequency is 100MHz or less. 5. The ion analyzer according to any one of claims 1 to 4, wherein said raw material gas is of a type that generates at least hydrogen radicals when supplied with said high-frequency power of said first frequency. 6. The ion analyzer according to claim 5, wherein said raw material gas is hydrogen gas, water vapor, or ammonia gas. 7. The ion analyzer according to any one of claims 1 to 6, further comprising a deflector for deflecting said charged particles between said radical transport path and said reaction chamber.

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