Mass Spectrometer and Mass Spectrometry Method

Abstract

Precursor cations are reacted with ammonium molecules or ammonia radicals to generate product ions, the product ions are separated and detected on the basis of mass-to-charge ratio, and on the basis of the difference between the detected mass-to-charge ratio of the product ions and the mass-to-charge ratio of the precursor ions, it is estimated whether or not aldehyde groups are contained in the molecular structure of the precursor ions. Further, this mass spectrometry device (1) is provided with: a reaction chamber (132) where precursor ions are introduced, an ammonia supply unit (5) which supplies ammonia molecules or ammonia radicals to the reaction chamber, and separation detection units (142, 143, 144, 145) which, on the basis of the mass-to-charge ratio, separate and detect the product ions generated from the precursor ions by reaction with the ammonia molecules or ammonia radicals.

Description

Technical Field

[0001] The present invention relates to a mass spectrometer and a mass spectrometry method.

Background Art

[0002] In order to identify a high molecular compound in a sample or analyze its structure, ions having a specific mass-to-charge ratio are selected as precursor ions from ions derived from sample components, and the precursor ions are dissociated to generate various product ions, and these precursor ions are separated and detected according to the mass-to-charge ratio. A mass spectrometry method is widely used. As such a mass spectrometry method, the collision induced dissociation (CID) method is the most common. In the collision induced dissociation method, precursor ions accelerated by applying energy (collision energy) are repeatedly collided with an inert gas (collision gas) such as argon to accumulate energy in the precursor ions and dissociate them.

[0003] Many high molecular compounds are organic substances having a hydrocarbon chain as a main skeleton. In order to know the characteristics of such high molecular compounds, it is effective to obtain information such as the presence or absence of an unsaturated bond of a carbon atom and the presence or absence of a characteristic functional group.

[0004] However, in an energy accumulation type ion dissociation method such as the collision induced dissociation method, since the energy accumulated in the precursor ions is dispersed throughout the molecule, the selectivity of the position where the precursor ions are dissociated is low, and it is difficult to dissociate the precursor ions at the position of the unsaturated bond of the carbon atom or a specific functional group. In addition, the mode of cleavage of the precursor ions changes depending on measurement conditions such as the magnitude of the collision energy and the gas pressure of the collision gas. Therefore, it is difficult to obtain information on the unsaturated bond of the carbon atom or a specific functional group by the collision induced dissociation method.

[0005] Therefore, recently, a radical attachment dissociation method has been proposed in which radicals are attached to precursor ions derived from sample components to dissociate the precursor ions at the unsaturated bonds of carbon atoms or the positions of specific functional groups. For example, Patent Documents 1 and 2 describe that precursor ions are selectively dissociated at the positions of peptide bonds by attaching hydrogen radicals or the like to the precursor ions. Further, Patent Documents 3 and 4 describe that precursor ions are selectively dissociated at the positions of unsaturated bonds contained in hydrocarbon chains by attaching oxygen radicals or the like to the precursor ions.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Non-Patent Documents

[0007]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] As described above, while it has been proposed to selectively dissociate precursor ions at specific sites using the radical attachment dissociation method, no effective method has yet been proposed for the aldehyde group, which is one of the typical functional groups in organic compounds, and there is a need for a technique to obtain information about the aldehyde group as well.

[0009] The problem to be solved by the present invention is to provide a technique capable of obtaining information on carbon-oxygen double bonds contained in the molecular structure of sample components.

Means for Solving the Problems

[0010] The mass spectrometry method according to the present invention, which has been made to solve the above problems, reacts a precursor ion with an ammonia molecule or an ammonia radical to generate a product ion, separates and detects the product ion according to the mass-to-charge ratio, and estimates whether an aldehyde group is included in the molecular structure of the precursor ion based on the difference between the mass-to-charge ratio of the detected product ion and the mass-to-charge ratio of the precursor ion. That's what it is.

[0011] Another aspect of the present invention, which has been made to solve the above problems, is an apparatus for generating a product ion from a precursor ion and performing mass spectrometry, comprising: a reaction chamber into which the precursor ion is introduced; an ammonia supply unit that supplies an ammonia molecule or an ammonia radical to the reaction chamber; and a separation and detection unit that separates and detects a product ion generated from the precursor ion by reaction with the ammonia molecule or the ammonia radical according to the mass-to-charge ratio. It is provided with.

Advantages of the Invention

[0012] In the present invention, a precursor ion derived from a sample component is reacted with an ammonia molecule (NH 3 ) or an ammonia radical (NH radical or NH 2React with (radicals) to generate product ions, separate and detect the generated product ions according to the mass-to-charge ratio. Then, based on the difference between the mass-to-charge ratio of the product ions and the mass-to-charge ratio of the precursor ions, estimate whether the molecular structure of the precursor ions contains an aldehyde group. The analyst may perform the estimation of the presence or absence of the aldehyde group himself / herself. The present invention is based on the finding that when a precursor ion having an aldehyde group is reacted with an ammonia molecule or an ammonia radical, they selectively act on the aldehyde group to change the carbon atom-oxygen atom double bond to a single bond, and an adduct ion is generated in which hydrogen is bonded to the carbon atom side and an amino group is bonded to the oxygen side. When a precursor ion having an aldehyde group is reacted with an ammonia molecule or an ammonia radical radical, a product ion (adduct ion) with a mass increase of 17 Da per aldehyde group is generated. Therefore, based on the difference between the mass-to-charge ratio of the product ions generated from the precursor ions and the mass-to-charge ratio of the precursor ions, it is possible to estimate whether the molecular structure of the precursor ions contains an aldehyde group.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0014] Examples of the mass spectrometer and mass spectrometry method according to the present invention will be described below with reference to the drawings.

[0015] FIG. 1 shows a schematic configuration of a mass spectrometer 1 of this embodiment. This mass spectrometer 1 is roughly composed of a mass spectrometer main body and a control / processing unit 6.

[0016] The mass spectrometer main body includes an ionization chamber 10 at approximately atmospheric pressure and a vacuum chamber. Inside the vacuum chamber, a first intermediate vacuum chamber 11, a second intermediate vacuum chamber 12, a third intermediate vacuum chamber 13, and an analysis chamber 14 are provided in this order from the side of the ionization chamber 10, and it has a configuration of a multi-stage differential pumping system in which the degree of vacuum increases in this order.

[0017] An electrospray ionization probe (ESI probe) 101 for charging and spraying a liquid sample is installed in the ionization chamber 10. The liquid sample may be directly injected into the ESI probe 101, or a sample component separated from other components contained in the liquid sample by a column of a liquid chromatograph may be introduced.

[0018] The ionization chamber 10 and the first intermediate vacuum chamber 11 communicate through a small-diameter heated capillary 102. The first intermediate vacuum chamber 11 is composed of a plurality of ring-shaped electrodes with different diameters, and an ion lens 111 for focusing ions is arranged near the ion optical axis C which is the central axis of the ion flight path.

[0019] The first intermediate vacuum chamber 11 and the second intermediate vacuum chamber 12 are separated by a skimmer 112 having a small hole at the top. The second intermediate vacuum chamber 12 is composed of a plurality of rod electrodes arranged so as to surround the ion optical axis C, and an ion guide 121 for focusing ions is arranged near the ion optical axis C.

[0020] The third intermediate vacuum chamber 13 is provided therein with a quadrupole mass filter 131 that separates ions according to the mass-to-charge ratio, a collision cell 132 having a multipole ion guide 133 therein, and an ion guide 134 for transporting the ions emitted from the collision cell 132. The ion guide 134 is composed of a plurality of ring-shaped electrodes having the same diameter.

[0021] A collision gas supply unit 4 is connected to the collision cell 132. The collision gas supply unit 4 has a collision gas source 41, a gas introduction flow path 42 for introducing the gas from the collision gas source 41 into the collision cell 132, and a valve 43 for opening and closing the gas introduction flow path 42. As the collision gas, an inert gas such as nitrogen gas or argon gas is used.

[0022] Also, a radical supply unit 5 is connected to the collision cell 132. The radical supply unit 5 has the same configuration as that described in Patent Document 5 and Non-Patent Document 1. As shown in FIGS. 1 and 2, the radical supply unit 5 includes a radical source 54 in which a radical generation chamber 51 is formed inside, a vacuum pump (not shown) for evacuating the radical generation chamber 51, a source gas supply source 52 for supplying a gas (source gas) serving as a raw material for radicals, and a high-frequency power supply unit 53. 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.

[0023] In FIG. 2, the radical source 54 is shown in a cross-sectional view. 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 internal space thereof becomes the radical generation chamber 51. The tubular body 541 is fixed by a plunger 545 in a state of being inserted inside a hollow cylindrical magnet 544. A spiral antenna 542 (broken line in FIG. 2) is wound around the outer periphery of the portion of the tubular body 541 located inside the magnet 544.

[0024] In addition, the radical source 54 is provided with a high-frequency power input unit 546. The high-frequency power input unit 546 is supplied with high-frequency power from the high-frequency power supply unit 53. Further, the radical source 54 includes a flange 547 for fixing the tip portion of the radical source 54. Inside the flange 547, a hollow cylindrical magnet 548 having the same diameter as the magnet 544, which forms a pair with the magnet 544, is accommodated. The magnets 544 and 548 generate a magnetic field inside the tubular body 541 (radical generation chamber 51), and the action thereof facilitates the generation and maintenance of plasma.

[0025] As the source gas, a gas capable of generating ammonia radicals (NH radicals or NH 2 radicals) is used. As such a source gas, for example, a mixed gas of nitrogen gas and water vapor can be used. In this case, nitrogen radicals are generated from nitrogen gas, hydrogen radicals are generated from water vapor, and they combine to generate ammonia radicals. In addition, amino radicals can be directly generated using ammonia gas. Alternatively, various gases (including mixed gases) can be used, such as generating nitrogen radicals using air as the source gas or generating hydrogen radicals using hydrogen gas as the source.

[0026] At the outlet end of the radical source 54, a transport pipe 58 for transporting the radicals generated in the radical generation chamber 51 to the collision cell 132 is connected. The transport pipe 58 is an insulating pipe, and for example, a quartz glass pipe or a borosilicate glass pipe can be used.

[0027] As shown in FIG. 3, in the transport pipe 58, a plurality of head portions 581 are provided in the portion disposed along the wall surface of the collision cell 132. Each head portion 581 is provided with an inclined conical inlet, and the radicals are introduced in a direction intersecting the central axis (ion optical axis C) of the flight direction of the ions. Thereby, the radicals can be uniformly supplied inside the collision cell 132.

[0028] The mass spectrometer 1 of this embodiment includes a radical supply unit 5 as an ammonia supply unit, and is configured to supply ammonia radicals from the radical supply unit 5 into the collision cell 132. However, it may be configured to supply ammonia molecules into the collision cell 132 instead of ammonia radicals. In that case, a raw material gas source 52 may be used as the ammonia supply unit, and the raw material gas source 52 may be directly connected to the collision cell 132. As the raw material gas for generating ammonia molecules, for example, ammonia gas or ammonia water vapor can be used.

[0029] The analysis chamber 14 includes an ion transport electrode 141 for transporting ions incident from the third intermediate vacuum chamber 13 to the orthogonal acceleration unit, an orthogonal acceleration electrode 142 composed of a pair of extrusion electrodes 1421 and pull-in electrodes 1422 arranged opposite to each other across the incident optical axis (orthogonal acceleration region) of the ions, an acceleration electrode 143 for accelerating the ions sent out to the flight space by the orthogonal acceleration electrode 142, a reflectron electrode 144 for forming a folded trajectory of the ions in the flight space, an ion detector 145, and a flight tube 146 that defines the outer edge of the flight space.

[0030] The control and processing unit 6 controls the operations of each unit and has a function of storing and analyzing the data obtained by the ion detector 145. In addition to the storage unit 61, the control and processing unit 6 includes a measurement control unit 62 and an aldehyde group estimation unit 63 as functional blocks. The storage unit 61 stores a method file describing the measurement conditions when performing the measurement described later, and information for converting the flight time of ions into the mass-to-charge ratio of the ions. The entity of the control and processing unit 6 is a general personal computer to which an input unit 7 and a display unit 8 are connected, and the above functional blocks are realized by executing a mass spectrometry program installed in advance by a processor.

[0031] Next, as an example of the mass spectrometry method according to the present invention, the analysis procedure using the mass spectrometer 1 of this embodiment will be described. The processing related to a series of measurements described below is executed by the measurement control unit 62 controlling each part of the mass spectrometer. In this example, first, MS measurement is performed to determine the mass-to-charge ratio of the precursor ion, and then ammonia radical is attached to the precursor ion to generate product ions, and MS / MS measurement for measuring the mass-to-charge ratio thereof is performed.

[0032] When the user instructs the start of analysis by a predetermined input operation, the liquid sample is introduced from an injector (not shown) in which the liquid sample has been set in advance into the electrospray ionization probe 101 and ionized.

[0033] Ions generated from the sample are drawn into the first intermediate vacuum chamber 11 through the heated capillary 102 due to the pressure difference between the ionization chamber 10 and the first intermediate vacuum chamber 11. In the first intermediate vacuum chamber 11, the ions are focused near the ion optical axis C by the ion lens 111.

[0034] The ions focused in the first intermediate vacuum chamber 11 then enter the second intermediate vacuum chamber 12, are focused near the ion optical axis C again by the ion guide 121, and then enter the third intermediate vacuum chamber 13.

[0035] In the MS measurement, all the ions are allowed to pass through as they are without operating the quadrupole mass filter 131 and the collision cell 132 in the third intermediate vacuum chamber 13. The ions that have passed through the collision cell 132 are focused near the ion optical axis C by the ion guide 134 and then enter the analysis chamber 14.

[0036] The ions that enter the analysis chamber 14 are transported to the orthogonal acceleration electrode 142 by the ion transport electrode 141. A voltage is applied to the orthogonal acceleration electrode 142 at a predetermined period, and the traveling direction of the ions is deflected in a direction substantially orthogonal to the previous traveling direction. The ions whose flight direction has been deflected are accelerated by the acceleration electrode 143 and sent out into the flight space. The ions created in the flight space fly along a predetermined flight path defined by the reflectron electrode 144 and the flight tube 146 at a time corresponding to the mass-to-charge ratio of each ion, and enter the ion detector 145. The ion detector 145 outputs a signal with a magnitude corresponding to the incident amount of ions each time an ion is incident. The output signal from the ion detector 145 is sequentially stored in the storage unit 61. In the storage unit 61, measurement data with the flight time of the ions and the detection intensity of the ions as axes is stored.

[0037] When the measurement is completed, the measurement control unit 62 reads out the measurement data stored in the storage unit 61 and the information for converting the flight time of the ions into the mass-to-charge ratio of the ions, and converts it into mass spectrum data with the mass-to-charge ratio of the ions and the detection intensity of the ions as axes.

[0038] Subsequently, the measurement control unit 62 identifies the peak with the highest intensity in the mass spectrum data and acquires its mass-to-charge ratio. In the electrospray ionization probe 101 used in this embodiment, usually, the proton-added ions in which protons are added to the sample molecules are generated the most. Therefore, in this embodiment, the proton-added ions are identified as the precursor ions corresponding to the peak with the highest intensity.

[0039] After determining the mass-to-charge ratio of the precursor ion, the measurement control unit 62 then performs MS / MS measurement. First, the inside of the radical generation chamber 51 is evacuated to a predetermined degree of vacuum by a vacuum pump, and a source gas (a mixed gas of nitrogen gas and water vapor in this embodiment) is introduced into the radical generation chamber 51 from the source gas supply source 52. Subsequently, a high-frequency voltage is supplied from the high-frequency power supply unit 53 to the spiral antenna 542, and plasma is generated in the radical generation chamber 51. As a result, nitrogen radicals and hydrogen radicals are generated from the source gas supplied to the radical generation chamber 51. These radicals combine to form ammonia radicals inside the radical generation chamber 51 or during transportation from the radical generation chamber 51 to the collision cell 132.

[0040] As described above, in this embodiment, ammonia radicals are generated and attached to the precursor ion, but ammonia molecules may be attached to the precursor ion instead of ammonia radicals. In that case, instead of the above-described steps related to the generation of ammonia radicals, ammonia molecules are supplied from the source gas supply source 52 into the collision cell 132.

[0041] After generating radicals in the radical supply unit 5 (or in parallel with the generation of radicals), a liquid sample is introduced from an injector in which the liquid sample has been set in advance into the electrospray ionization probe 101 and ionized.

[0042] Ions generated from the sample are focused near the ion optical axis C while passing through the first intermediate vacuum chamber 11 and the second intermediate vacuum chamber 12 and enter the third intermediate vacuum chamber 13, similar to during MS measurement.

[0043] In the third intermediate vacuum chamber 13, ions having the mass-to-charge ratio determined based on the above MS measurement are selected as precursor ions by the quadrupole mass filter 131 and introduced into the collision cell 132. As described above, ammonia radicals are introduced into the collision cell 132, and the ammonia radicals adhere to the precursor ions. At this time, the ammonia radicals selectively adhere to the position of the aldehyde group contained in the molecular structure of the precursor ion. As a result, the carbon-oxygen double bond constituting the aldehyde group changes to a single bond, a hydrogen is bonded to the carbon side, and an amino group is bonded to the oxygen side, generating product ions (adduct ions). The product ions generated in the collision cell 132 are focused near the ion optical axis C by the ion guide 134 and then enter the analysis chamber 14.

[0044] In the analysis chamber 14, similar to the MS measurement, the product ions fly through a predetermined flight path defined by the reflector electrode 144 and the flight tube 146 at a time corresponding to the mass-to-charge ratio of each ion and enter the ion detector 145. The ion detector 145 outputs a signal having a magnitude corresponding to the incident amount of ions every time an ion is incident. The output signal from the ion detector 145 is sequentially stored in the storage unit 61. In the storage unit 61, it is stored as measurement data with the flight time of the ions and the detection intensity of the ions as axes.

[0045] When the measurement is completed, the aldehyde group estimation unit 63 reads out the measurement data stored in the storage unit 61 and the information for converting the flight time of the ions into the mass-to-charge ratio of the ions, and converts it into data of a mass spectrum (product ion spectrum) with the mass-to-charge ratio of the ions and the detection intensity of the ions as axes.

[0046] When mass spectrum data is created, the aldehyde group estimation unit 63 extracts information on mass peaks included in the mass spectrum. Subsequently, among the mass peaks having a mass-to-charge ratio greater than that of the precursor ion, those having a difference from the mass of the precursor ion of n times 17 Da (mass-to-charge ratio of 17 in the case of monovalent ions) (mass peaks of adduct ions), where n is a natural number, are extracted. Then, the above-mentioned n of the product ion having the largest mass-to-charge ratio is determined. After determining n, the aldehyde group estimation unit 63 displays on the screen of the display unit 8 the mass peaks of the precursor ion and the mass peaks of the adduct ions with a predetermined mark attached to the product ion spectrum, and the numerical value of the above-mentioned n. On the other hand, when there is no mass peak among the mass peaks having a mass-to-charge ratio greater than that of the precursor ion and having a difference from the mass of the precursor ion of n times 17 Da (mass-to-charge ratio of 17 in the case of monovalent ions), where n is a natural number, it is estimated that the molecular structure of the sample component does not contain an aldehyde group.

[0047] Here, the results of measuring Aldehyde C-10 by the above procedure will be described. The upper part of FIG. 4 shows the molecular structure of the precursor ion generated from Aldehyde C-10, and the lower part shows the molecular structure of the product ion (adduct ion) generated by the attachment of an ammonia radical. FIG. 5 is the product ion spectrum obtained by measurement.

[0048] In the product ion spectrum shown in FIG. 5, the mass peak with a mass-to-charge ratio of 151.1591 is that of the precursor ion (protonated ion). Also, a mass peak appears at a position where the mass-to-charge ratio is 17.0263 greater than that of the precursor ion. This is the mass peak of the adduct ion generated by the reaction of an ammonia radical with the precursor ion. Therefore, from this product ion spectrum, it is estimated that the molecular structure of the sample component (Aldehyde C-10) contains one aldehyde group.

[0049] Conventionally, for the analysis of the molecular structure of precursor ions, a method has been adopted in which the precursor ions are subjected to collision-induced dissociation (CID) to generate product ions, and the obtained product ion spectrum is compared with the product ion spectra recorded in a database, and the sample components are identified based on the degree of coincidence. However, in the CID method, the selectivity of the cleavage position of the precursor ions is low, and even if mass spectrometry is performed under the same measurement conditions as those recorded in the database, it is difficult to obtain the same product ion spectrum. Therefore, for example, when trying to identify a compound by spectrum matching, there are many candidate compounds with similar scores (degree of coincidence of mass spectra), and it has been difficult to identify which of them is the sample component.

[0050] On the other hand, when performing the above measurement using the mass spectrometer of this example, since the number of aldehyde groups contained in the compound that is the sample component is specified and the candidate compounds are narrowed down, the sample component can be identified more accurately. In addition, when the precursor ions are reacted with ammonia radicals or ammonia molecules, the selectivity of the dissociation position of the precursor ions is high, and a mass spectrum closer to the mass spectrum recorded in the database is likely to be obtained compared to the CID method, so the identification accuracy of the compound by spectrum matching is improved.

[0051] The above example is just an example and can be appropriately modified in accordance with the gist of the present invention. In the above example, only the measurement of attaching ammonia radicals to obtain a product ion spectrum, which is characteristic of the present invention, was described. However, it is preferable to obtain a product ion spectrum also by the CID method in combination with this measurement, and to identify the sample components from both of these product ion spectra.

[0052] In the above embodiment, a time-of-flight (TOF) type mass separator was used as the subsequent mass filter, but other types of mass separators such as a quadrupole mass filter can also be used. However, by using a TOF type mass separator as in the above embodiment, the precise mass of product ions can be measured, so that adduct ions generated by the attachment of ammonia radicals can be more reliably identified.

[0053] Further, in the above embodiment, the sample components in the liquid sample were ionized by the electrospray ionization probe 101, but other ionization sources such as an atmospheric pressure chemical ionization (APCI) probe may be used. Also, not limited to liquid samples, a configuration can be adopted in which sample components are ionized by an appropriate ionization source for solid samples and gas samples as well.

[0054] Furthermore, in the above embodiment, the configuration was such that precursor ions were introduced into the collision cell 132 to attach ammonia radicals, but the configuration can also be such that precursor ions are introduced into an ion trap.

[0055] [Aspect] Those skilled in the art will understand that the above-described plurality of exemplary embodiments are specific examples of the following aspects.

[0056] (Item 1) A mass spectrometry method according to one aspect is reacting precursor ions with ammonia molecules or ammonia radicals to generate product ions, separating and detecting the product ions according to the mass-to-charge ratio, estimating whether an aldehyde group is included in the molecular structure of the precursor ions based on the difference between the mass-to-charge ratio of the detected product ions and the mass-to-charge ratio of the precursor ions and is as described above.

[0057] (Item 2) A mass spectrometer according to one aspect is An apparatus for generating product ions from precursor ions and performing mass spectrometry, comprising: a reaction chamber into which the precursor ions are introduced; an ammonia supply unit for supplying ammonia molecules or ammonia radicals to the reaction chamber; a separation and detection unit for separating and detecting product ions generated from the precursor ions by reaction with the ammonia molecules or ammonia radicals according to the mass-to-charge ratio; and comprising.

[0058] In the mass spectrometry method according to claim 1 and the mass spectrometry apparatus according to claim 2, precursor ions derived from a sample component are reacted with ammonia molecules (NH 3 ) or ammonia radicals (NH radical or NH 2 radical) to generate product ions, and the generated product ions are separated and detected according to the mass-to-charge ratio. Then, based on the difference between the mass-to-charge ratio of the product ions and the mass-to-charge ratio of the precursor ions, it is estimated whether the molecular structure of the precursor ions contains an aldehyde group. The mass spectrometry method according to claim 1 and the mass spectrometry apparatus according to claim 2 are based on the finding that when precursor ions having an aldehyde group are reacted with ammonia molecules or ammonia radicals, they selectively act on the aldehyde group to change the carbon atom-oxygen atom double bond to a single bond, and an adduct ion in which hydrogen is bonded to the carbon atom side and amino is bonded to the oxygen side is generated. When precursor ions having an aldehyde group are reacted with ammonia molecules or ammonia radicals, product ions having a mass increased by 17 Da per aldehyde group (adduct ions) are generated. Therefore, based on the difference between the mass-to-charge ratio of the product ions generated from the precursor ions and the mass-to-charge ratio of the precursor ions, it is possible to estimate whether the molecular structure of the precursor ions contains an aldehyde group.

[0059] (Item 3) In the mass spectrometry apparatus according to claim 2, further, An aldehyde group estimation unit that estimates whether or not an aldehyde group is included in the molecular structure of the precursor ion based on the difference between the mass-to-charge ratio of the detected product ion and the mass-to-charge ratio of the precursor ion is provided.

[0060] In the mass spectrometer according to item 3, since the presence or absence of an aldehyde group is estimated by the aldehyde group estimation unit, it is not necessary for the user to analyze the difference between the mass-to-charge ratio of the product ion and the mass-to-charge ratio of the precursor ion by themselves, and information about the presence or absence of an aldehyde group can be obtained easily.

[0061] (Item 4) In the mass spectrometer according to item 3, the aldehyde group estimation unit estimates that one aldehyde group is included for every 17 Da with respect to the difference in the mass-to-charge ratio.

[0062] In the mass spectrometer according to item 4, information not only about the presence or absence of an aldehyde group but also about the number of aldehyde groups can be obtained.

[0063] (Item 5) In the mass spectrometer according to any one of items 2 to 4, the ammonia supply unit includes a radical generation unit that generates ammonia radicals.

[0064] In the mass spectrometer according to item 5, ammonia radicals are generated by the radical generation unit and reacted with the precursor ion. Since radical species are more chemically active than neutral molecules, more precursor ions can react with the ammonia radicals to generate adduct ions than when reacting with ammonia molecules.

[0065] (Item 6) In the mass spectrometer according to any one of item 5, the radical generation unit generates nitrogen radicals and hydrogen radicals or hydrogen atoms.

[0066] (Item 7) In the mass spectrometer according to claim 5 or 6, the radical generation unit generates radicals using nitrogen gas and water vapor as source gases.

[0067] In the mass spectrometer according to claim 6, ammonia radicals are generated from nitrogen radicals and hydrogen radicals or hydrogen atoms. Since these radicals or atoms can be generated from various source gases, the source gas can be selected in consideration of conditions such as gas handling, availability, and price. As a combination of source gases considering these points, for example, a mixed gas of nitrogen gas and water vapor can be used as the source gas as in the mass spectrometer according to claim 7.

Explanation of Symbols

[0068] 1... Mass spectrometer 10... Ionization chamber 101... Electrospray ionization probe 11... First intermediate vacuum chamber 111... Ion lens 12... Second intermediate vacuum chamber 121... Ion guide 13... Third intermediate vacuum chamber 131... Quadrupole mass filter 132... Collision cell 133... Multipole ion guide 134... Ion guide 14... Analysis chamber 141... Ion transport electrode 142... Orthogonal acceleration electrode 143... Acceleration electrode 144... Reflectron electrode 145... Ion detector 146... Flight tube 4... Collision gas supply unit 5... Radical supply unit 51... Radical generation chamber 52... Source gas supply source 53... High-frequency power supply unit 54... Radical source 58…Transport pipe 581…Head part 6…Control and processing unit 61…Memory unit 62…Measurement control unit 63…Aldehyde group estimation unit 7…Input unit 8…Display unit

Claims

1. Reacting a precursor ion with an ammonia molecule or an ammonia radical to generate a product ion, separating and detecting the product ion according to the mass-to-charge ratio, estimating that the molecular structure of the precursor ion contains an aldehyde group based on the detection of a product ion whose mass difference from the precursor ion is an integer multiple of 17 Da A mass spectrometry method.

2. An apparatus for generating a product ion from a precursor ion and performing mass spectrometry, comprising: a reaction chamber into which the precursor ion is introduced; an ammonia supply unit that supplies an ammonia molecule or an ammonia radical to the reaction chamber; a separation and detection unit that separates and detects a product ion generated from the precursor ion by reaction with the ammonia molecule or the ammonia radical according to the mass-to-charge ratio; an aldehyde group estimation unit that estimates that the molecular structure of the precursor ion contains an aldehyde group based on the detection of a product ion whose mass difference from the precursor ion is an integer multiple of 17 Da A mass spectrometer.

3. The mass spectrometer according to claim 2, wherein the aldehyde group estimation unit estimates that one aldehyde group is contained per 17 Da for the mass difference.

4. The mass spectrometer according to claim 2, wherein the ammonia supply unit includes a radical generation unit that generates an ammonia radical.

5. The mass spectrometer according to claim 4, wherein the radical generation unit generates a nitrogen radical and a hydrogen radical or a hydrogen atom.

6. The mass spectrometer according to claim 4, wherein the radical generation unit generates radicals using nitrogen gas and water vapor as source gases.

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