JP4790507B2 - Product ion spectrum creating method and apparatus - Google Patents

Description

  The present invention relates to a product ion preparation method and apparatus used in the fields of quantitative analysis, qualitative analysis of trace compounds, and structural analysis of sample ions.

(Time-of-flight mass spectrometer)
In a time-of-flight mass spectrometer (TOFMS), ions are accelerated with a constant pulse voltage Va. At this time, the ion velocity v from the energy conservation law ^{mv 2/2 = qeVa (1} )
v = √ (2qeVa / m) (2)
It is expressed. Where m is the mass of the ion, q is the charge of the ion, and e is the elementary charge. A detector placed after a certain distance L arrives at a flight time T. T is expressed by the following equation.

T = L / v = L√ (m / 2qeVa) (3)
Since the flight time differs depending on the mass of ions from the equation (3), the mass can be analyzed.

  FIG. 4 is an explanatory diagram of a linear TOFMS. Reference numeral 1 denotes a pulse ion source, and a pulse voltage generator 2 is provided therein. Here, when ions generated from the pulse ion source 1 are accelerated in a pulse manner by the pulse voltage generator 2, each ion flies through the space and reaches the detector 3. In this case, since ions having a small mass have a higher speed, they arrive at the detector 3 from ions having a small mass.

  In the case of linear TOFMS, the ion optical system is designed so that the space in the ion source and the spread of kinetic energy converge on the detection surface in time. Several ion acceleration methods have been proposed as methods for realizing such time convergence (see, for example, Non-Patent Documents 1 to 4).

The mass resolution of TOFMS is T, where the total flight time is T and the peak width is ΔT.
Mass resolution = T / 2ΔT (4)
Defined by In the linear TOFMS, T is limited because it leads to an increase in the size of the apparatus, and ΔT is also deteriorated by extending the execution flight distance, so that high mass resolution cannot be obtained.

  In order to make up for the shortcomings of such a linear TOFMS, a reflective TOFMS that extends the flight distance by placing a reflected electric field between the ion source and the detector, that is, can increase T, is also widely used. Yes.

FIG. 5 is an explanatory diagram of a reflective TOFMS. The ions in the pulse ion source 1 are accelerated in a pulse manner by the pulse voltage generator 2. The accelerated ions are reflected by the reflected electric field of the reflectron 4 and arrive at the detector 3 from ions having a small mass. In this case, the total flight time T is increased by the distance until the ions incident on the reflected electric field are reflected, and the mass resolution is improved.
(Helix orbital TOFMS)
The mass resolution of the TOFMS time-of-flight mass is defined by equation (4). That is, mass resolution can be improved if the total flight time T can be extended while the peak width ΔT is kept constant. However, in the conventional linear and reflective TOFMS, extending the total flight time T, that is, extending the total flight time directly leads to an increase in the size of the apparatus. A multi-turn type time-of-flight mass spectrometer (see Non-Patent Document 5) is a device that has been developed to avoid an increase in size of the device and to achieve high mass resolution.

  This device can extend the total flight time T by using four toroidal electric fields in which a Mazda plate is combined with a cylindrical electric field, and by making multiple rounds of eight-shaped circular orbits. Since this apparatus employs an ion optical system that can completely satisfy the space convergence condition and the time convergence condition for each round, the time spread (ΔT) by extending the flight distance and the space of the ion beam. Is prevented.

  However, the problem of “overtaking” exists in TOFMS that makes multiple rounds of closed orbits. This occurs because light ions (high flight speed) overtake heavy ions (low flight speed) because they make multiple rounds of closed orbit. For this reason, the basic concept of TOFMS that arrives in order from light ions to the detection surface is not valid.

A helical trajectory TOFMS has been devised to solve this problem. The helical trajectory type TOFMS is characterized in that the start point and the end point of the closed trajectory are shifted in the direction perpendicular to the closed trajectory. In order to realize this, there are a method in which ions are incident obliquely from the beginning (see, for example, Patent Document 1), and a method in which a start point and an end point of a closed orbit are shifted in the vertical direction using a deflector (see, for example, Patent Document 2). ).
(MALDI method and delayed withdrawal method)
In the MALDI (Matrix Assisted Laser Desorption Ionization) method, a sample is mixed and melted in a matrix (liquid, crystalline compound, metal powder, etc.) having an absorption band at the laser light wavelength to be used, and the sample is irradiated with a laser. This is a method of vaporizing or ionizing. In ionization with a laser typified by the MALDI method, the initial energy distribution at the time of ion generation is large, and the delayed extraction method is used in most cases in order to converge this time. This is a method in which a pulse voltage is applied with a delay of about several hundred ns from laser irradiation.

  FIG. 6 is an explanatory diagram of the MALDI method and the delay extraction method. In the figure, 10 is a sample plate, and 11 is a sample fixed to the sample plate 10. 14 is an intermediate electrode for accelerating ions, and 15 is a base electrode. Reference numeral 12 denotes a lens 1 for focusing the laser beam, reference numeral 13 denotes a mirror 1 for reflecting the laser beam, and reference numeral 16 denotes an analyzer for detecting ions arriving from an ion source. 17 is a mirror 2 that reflects an image from the ion source, 18 is a lens 2 that focuses the image reflected from the mirror 2, and 19 is a CCD camera that observes the image of the sample 11 that enters through the lens 2. It is. The operation of the apparatus configured as described above will be described as follows.

  On the sample plate 10, the sample 11 obtained by mixing and dissolving the sample in a matrix (liquid, crystalline compound, metal powder, etc.) is fixed. The mirror 2, the lens 2, and the CCD camera 19 are arranged so that the state of the sample 11 can be observed. The sample 11 is irradiated with laser light by the lens 1 and the mirror 1 to vaporize or ionize the sample 11. The generated ions are accelerated by a voltage applied to an acceleration electrode (not shown) and introduced into the TOFMS.

Next, a time-of-flight measurement sequence in the delay extraction method will be described. First, the potential of the acceleration electrode and the sample plate 10 is set to the same potential Vs. Next, after receiving a signal from the laser notifying laser oscillation, the voltage of the accelerating electrode is changed at a high speed after several hundred ns, and a potential gradient is created between the sample plate 10 and the accelerating electrode for acceleration. This potential gradient is a gradient between the potentials Vs and V1. The start time of time-of-flight measurement is synchronized with the rise time of the pulse voltage generator.
(Vertical acceleration method)
Since the MALDI method generates ions in a pulsed manner, it is highly compatible with TOFMS. However, there are many ionization methods for mass spectrometry such as El, Cl, ESl, and APCl that generate ions continuously. Orthogonal acceleration (vertical acceleration method) was developed to combine these ionization methods with TOFMS.

FIG. 7 is an explanatory diagram of a vertical acceleration type TOFMS. The ion beam generated from the ion source 20 that continuously generates ions is transported to the vertical acceleration unit 22 with a kinetic energy of several tens of eV. In the vertical acceleration unit 22, a pulse voltage of about 10 kV is applied by the pulse voltage source 21, and ions are accelerated in the direction perpendicular to the transport direction from the ion source 20 and input to the reflected electric field 24. Lead to detector 23. Since the arrival time from the pulse voltage application start time to the detector 23 differs depending on the mass of ions, mass separation is performed.
(MS / MS measurement and TOF / TOF equipment)
In general mass spectrometry, a mass spectrum obtained by mass-separating ions generated by an ion source using a mass spectrometer is measured. At this time, the only information obtained is the mass. Hereinafter, this measurement is called MS measurement with respect to MS / MS measurement. On the other hand, there is MS / MS measurement in which specific ions (precursor ions) generated by an ion source are spontaneously or forcibly cleaved and the generated product ions are observed. In this measurement, the mass information of the precursor ions and the mass information of the product ions generated by a plurality of paths can be obtained, so that the structure information of the precursor ions can be obtained.

  FIG. 8 is an explanatory diagram of MS / MS measurement. The precursor ions are cleaved to obtain product ions. Then, mass analysis is performed on all the obtained product ions. As a result, structural analysis of the precursor ion can be performed. An MS / MS apparatus in which two TOFMSs are connected in series is generally called a TOF / TOF apparatus, and is mainly used in an apparatus employing a MALDI ion source.

  The TOF / TOF apparatus is composed of a linear TOFMS and a reflective TOFMS. FIG. 9 is a diagram showing a configuration example of an MS / MS apparatus in which TOFMSs are connected in series. 30 is a first TOFMS and 31 is a second TOFMS. In the first TOFMS 30, 32 is an ion source, which generates precursor ions. Reference numeral 33 denotes an ion gate provided for selecting a precursor ion. A time convergence point of the first TOFMS 30 is disposed in the vicinity of the ion gate 33. Reference numeral 34 denotes a collision chamber in which precursor ions are input to collide. The ions collided in the collision chamber 34 enter the second TOFMS 31 and are reflected by the reflection field, and then detected by the detector 36.

The precursor ions are forcibly cleaved in the collision chamber 34 disposed before the reflection field of the first TOFMS 30 or the first TOFMS 31 when they are spontaneously cleaved. The kinetic energy of the cleavage product ion is distributed in proportion to the mass of the product ion,
Up = Ui × m / M (5)
It is expressed. Here, Up is the kinetic energy of the product ion, Ui is the kinetic energy of the precursor ion, m is the mass of the product ion, and M is the mass of the precursor ion. In the second TOFMS 31 including the reflection field, since the flight time varies depending on the mass and kinetic energy, the product ion can be subjected to mass analysis.
Rev. Sci. Instrum, 26, 1150 (1955) Rapid Commun. Mass Spectram, 8, 865 (1994) Rapid Commun. Mass Spectram, 3, 155 (1989) So.Phys.JETP, 3745 (1973) J. Mass Spectram. Soc. Jpn, 51, 2 (2003) 349-353 JP 2000-243345 A (paragraphs 0010 to 0016, FIG. 1) JP 2003-86129 A (paragraphs 0010 to 0022, FIG. 1)

Since isotopes are present in carbon, oxygen, nitrogen, hydrogen, etc. constituting the sample ions, a plurality of types of sample ion masses exist depending on the combination. A group of peaks of the same molecule appearing in the mass spectrum but having different masses is generally called an “isotope peak”. FIG. 10 is an explanatory diagram of an isotope peak. The horizontal axis is m / z, and the vertical axis is the peak intensity normalized by 100. The figure shows an example of protonated ions of Angiotesinl (C ₆₂ H ₉₀ N ₁₇ O ₁₄ ).

From the figure, it can be seen that several ions exist at intervals of 1 unit (unit is a mass unit in which the mass of ¹² C is defined as 12 units). Among them, a peak having the smallest mass, that is, a peak composed of only a single isotope such as ¹² C, ¹⁶ O, ¹⁴ N, and ¹ H is called a “monoisotopic ion”.

  Now, when a linear (linear) TOFMS is adopted as the first TOFMS as in the prior art, the flight distance can only be about 100 mm. At such a flight distance, the flight time difference between the isotope peaks is 10 ns or less, and considering the switching speed of the ion gate, it is impossible to achieve high selectivity, and a plurality of isotope ions are allowed to pass through. become. However, selecting a plurality of isotope ions presents a major problem. This will be described below.

  If the second TOFMS including the reflected electric field is a system that completely satisfies energy convergence (a system in which the flight time does not change due to the kinetic energy of the product ions), the time to pass through the first TOFMS is the flight time of the second TOFMS to the mass of the precursor ion. Is a value depending on the mass of the product ion. Here, for the sake of simplicity, let us consider a case where a certain monovalent precursor ion is cleaved into a monovalent charged product ion having two isotopes and neutral particles.

  FIG. 11 is a diagram showing isotope peaks of product ions, and FIG. 12 is a diagram showing isotope peaks of neutral particles. FIG. 11 shows the mass and intensity ratio of product ions, and FIG. 12 shows the mass and intensity ratio of neutral particles.

  Before the cleavage, the product ions and neutral particles were bound, so there are 16 combinations of precursor ions, but the mass is 7 (M, M + 1, M + 2, M + 3, M + 4, M + 5, M + 6: where M = m + n) (see FIG. 13). FIG. 13 is a diagram showing the intensity ratio of each combination of precursor ions and the isotope peak ratio of the precursor ions. For each precursor ion mass (M, M + 1, M + 2, M + 3, M + 4, M + 5, M + 6), the combination of product ions and neutral particles, the time of flight of the first TOFMS, The time of flight of the second TOFMS, the intensity ratio of each combination, and the isotope peak of the precursor ion are shown.

The arrival time of each cleavage path to the detector is the sum of the flight time of the precursor ion of mass X in the first TOFMS as T1 _{, X} and the flight time of the product ion of mass Y in the second TOFMS as T2 _{, Y.} In addition, the intensity ratio is represented by multiplication of the intensity ratio between the product ion and neutral particles in each case. Now for the sake of simplicity
R _m : R _{m + 1} : R _{m + 2} : R _{m + 3} = R _n : R _{n + 1} : R _{n + 2} : R _{n + 3}
When 0.4 = 0.3: 0.2: 0.1, the intensity ratio of each combination and the isotope peak ratio of the precursor ion are as shown in FIG. When FIG. 13 is viewed from the viewpoint of product ions, it is as shown in FIG. The product ion spectrum near the mass m is as shown in FIG.

  FIG. 14 shows combinations of product ions with respect to mass, intensity ratios, and isotope ratios of product ions. In FIG. 15, ΔT1 is the difference in flight time between the isotope peaks of the precursor ions in the first TOFMS, and ΔT2 is the difference in flight time between the isotope ions of the product ions in the second TOFMS. The time-of-flight differences between the isotopes are considered to be almost the same.

  As shown in the figure, since the masses of the precursor ions are different, the flight time between product ions (for example, 1), 2), 4), and 7)) having the same mass is shifted. Actually, since the peak has a width, the peak 2) becomes a base of the peak 1) or the baseline rises between the peaks 1) and 3). Either way, high mass accuracy of product ions cannot be obtained.

  One effective method for solving this problem is to select only the precursor ion monoisotopic ion. When a monoisotopic ion is selected as the precursor ion, the only ions that can be cleaved from it are monoisotopic ions, and the influence of isotope peaks can be eliminated, interpretation can be simplified, and mass accuracy can be improved.

  Since the helical trajectory TOFMS has time and space convergence for each round, an intermediate convergence point is created once in the trajectory of the spiral trajectory TOFMS in both cases of the MALDI method and the vertical acceleration method. The distance is less than or equal to the distance to the intermediate convergence point in the case of linear TOFMS. Like the delay time of the MALDI method, the factor that influences the time convergence at the intermediate convergence point derived from the ion source is Less than the same level.

  Furthermore, since the state at the intermediate convergence point can be maintained even if the number of laps is increased at the intermediate convergence point, the flight distance of the first TOFMS can be increased by about 50 to 100 times while maintaining the time convergence. That is, the time-of-flight difference between the isotope ions of the precursor ions can be increased by about 50 to 100 times, and one isotope ion can be selected.

  However, as the mass of the precursor ion increases, the ratio of monoisotopic ions to the total isotope ions decreases. Therefore, in the case of ions having a large mass, there is a problem that the sensitivity of product ions is deteriorated.

  The present invention has been made in view of such problems. By adopting a time-of-flight mass spectrometer in the first TOFMS, each isotope peak is selected by an ion gate and MS / MS measurement is performed. Can reconstruct MS / MS spectra with selected major isotope peaks and create one product ion spectrum, reducing mass accuracy compared to selecting only monoisotopic ions It is an object of the present invention to provide a product ion spectrum creation method and apparatus capable of obtaining a sensitive spectrum without any problems.

(1) The invention according to claim 1 is directed to an ion source for ionizing a sample, an acceleration means for accelerating ions in a pulsed manner, a time-of-flight mass spectrometer, and an ion for selecting an ion having a specific mass. Tandem mass consisting of a gate, means for cleaving selected ions, a reflective time-of-flight mass spectrometer including a reflected electric field, and a detector that detects ions that have passed through the reflective time-of-flight mass spectrometer Using the analyzer, the following operations are performed.
1) One isotope ion of the precursor ion is selected by the ion gate.
2) The selected precursor ion is cleaved to obtain a product ion spectrum.
3) The above 1) and 2) are repeated to cleave a plurality of isotope ions of the precursor ion to obtain a product ion spectrum.
4) The spectrum acquired in 3) is changed to the time-of-flight axis of the reflection type time-of-flight mass spectrometer, and the product ion spectrum is synthesized.
5) Change the time-of-flight axis of the synthesized product ion spectrum to the mass axis.

(2) The invention described in claim 2 is directed to an ion source for ionizing a sample, a transport means for transporting ions, an acceleration means for accelerating ions in a direction perpendicular to the transport direction, and a time of flight. -Type mass spectrometer, ion gate for selecting ions having a specific mass, means for cleaving selected ions, reflection-type time-of-flight mass spectrometer including a reflected electric field, and reflection-type time-of-flight mass spectrometer The following operation is performed using a tandem mass spectrometer that includes a detector that detects ions that have passed through.
1) One isotope ion of the precursor ion is selected by the ion gate.
2) The selected precursor ion is cleaved to obtain a product ion spectrum.
3) The above 1) and 2) are repeated to cleave a plurality of isotope ions of the precursor ion to obtain a product ion spectrum.
4) The spectrum acquired in 3) is changed to the time-of-flight axis of the reflection type time-of-flight mass spectrometer, and the product ion spectrum is synthesized.
5) Change the time-of-flight axis of the synthesized product ion spectrum to the mass axis.

  (3) The invention according to claim 3, wherein in the method for creating a product ion spectrum, synthesis is performed after applying an arbitrary constant so that the isotope ratio of the precursor ion in the product ion spectrum matches the calculated value. Features.

  (4) In the invention according to claim 4, the time-of-flight mass spectrometer of the tandem mass spectrometer is configured by using a time-of-flight mass spectrometer configured by a plurality of fan electric fields and making multiple rounds of the same orbit. Features.

  (5) The invention according to claim 5 uses a time-of-flight mass spectrometer configured by a plurality of sector electric fields and flying ions in a spiral trajectory for the time-of-flight mass spectrometer of the tandem mass spectrometer. It is characterized by.

  (6) In the invention according to claim 6, when the first time-of-flight mass spectrometer is a spiral orbit type time-of-flight mass spectrometer, the incident angle of ions to the spiral orbit type time-of-flight mass spectrometer is adjusted. Therefore, a means for deflecting ions is provided between the means for accelerating ions in a pulse manner and the spiral orbital time-of-flight mass spectrometer.

(7) The invention according to claim 7 is characterized in that the ionization method in the ion source is a MALDI method.
(8) The invention according to claim 8 is characterized in that a delayed extraction method is used as means for accelerating ions.

(9) The invention according to claim 9 is characterized in that another detector that is movable between the ion trajectory and the ion trajectory is provided between the time-of-flight mass spectrometer and the reflected electric field. .
(10) The invention according to claim 10 is characterized in that the means for cleaving is a CID method performed by filling the collision chamber with gas.

  (11) The invention according to claim 11 is directed to an ion source for ionizing a sample, an acceleration means for accelerating ions in a pulsed manner, a time-of-flight mass spectrometer, and an ion for selecting an ion having a specific mass. Tandem mass consisting of a gate, means for cleaving selected ions, a reflective time-of-flight mass spectrometer including a reflected electric field, and a detector that detects ions that have passed through the reflective time-of-flight mass spectrometer In a product ion spectrum generator using an analyzer, one isotope ion of a precursor ion is selected by an ion gate, the selected precursor ion is cleaved, a product ion spectrum is acquired, and a plurality of isotope ions of the precursor ion are obtained. The product ion spectrum, and the obtained spectrum is reflected time-of-flight mass spectrometer Change flight time axis, to synthesize the product ion spectrum, characterized by being configured to change the flight time axis of the synthesized product ion spectrum the mass axis.

  (12) The invention according to claim 12 is directed to an ion source for ionizing a sample, transport means for transporting ions, acceleration means for accelerating ions in a direction perpendicular to the transport direction, and time of flight. -Type mass spectrometer, ion gate for selecting ions having a specific mass, means for cleaving selected ions, reflection-type time-of-flight mass spectrometer including a reflected electric field, and reflection-type time-of-flight mass spectrometer In a product ion spectrum generator using a tandem mass spectrometer that consists of a detector that detects ions that pass through the ion, one isotope ion of the precursor ion is selected by the ion gate, and the selected precursor ion is cleaved. Product ion spectrum, cleave multiple isotope ions of precursor ion, and product ion spectrum It was configured to change the acquired spectrum to the time-of-flight axis of the reflection type time-of-flight mass spectrometer, synthesize the product ion spectrum, and change the time-of-flight axis of the synthesized product ion spectrum to the mass axis. It is characterized by that.

  (1) According to the invention described in claim 1, when a pulse ion source is used as an ion source, an isotope peak is selected by an ion gate by adopting a time-of-flight mass spectrometer in the first TOFMS. MS / MS measurement can be performed. In addition, by reconstructing the MS / MS spectrum with the main isotope peaks selected and creating one product ion spectrum, the mass accuracy is not reduced compared to the case of selecting only monoisotopic ions. A sensitive spectrum can be obtained.

  (2) According to the invention described in claim 2, when an ion source that continuously generates ions is used as the ion source, by adopting a time-of-flight mass spectrometer in the first TOFMS, Isotope peaks can be selected and MS / MS measurements can be made. In addition, by reconstructing the MS / MS spectrum with the main isotope peaks selected and creating one product ion spectrum, the mass accuracy is not reduced compared to the case of selecting only monoisotopic ions. A sensitive spectrum can be obtained.

  (3) According to the invention described in claim 3, mass accuracy is lowered by multiplying an arbitrary constant so that the isotope ratio of the precursor ion in the product ion spectrum matches the calculated value, and then synthesizing. And a sensitive spectrum can be obtained.

  (4) According to the invention described in claim 4, by using a multi-turn type time-of-flight mass spectrometer for the first TOFMS, the time of flight can be extended and the selectivity of the precursor ion can be improved.

  (5) According to the invention described in claim 5, by using a spiral orbit type time-of-flight mass spectrometer for the first TOFMS, the time of flight can be extended and the selectivity of the precursor ion can be improved.

  (6) According to the invention described in claim 6, when the first TOFMS is a spiral orbit type time-of-flight mass spectrometer, the means for deflecting ions is provided, and the incident angle of the ions is adjusted to the angle of the spiral orbit. Can be incident.

(7) According to the invention described in claim 7, the MALDI method can be used as the ionization method in the ion source.
(8) According to the invention described in claim 8, the time convergence of ions can be improved by using the delayed extraction method as means for accelerating ions.

  (9) According to the ninth aspect of the invention, by providing another detector between the time-of-flight mass spectrometer and the reflected electric field, ion detection (MS measurement) during flight can be performed. .

(10) According to the invention of the tenth aspect, the collision chamber can be filled with gas to be cleaved.
(11) According to the invention of claim 11, when a MALDI ion source is used as an ion source, an isotope peak is selected by an ion gate by adopting a time-of-flight mass spectrometer in the first TOFMS. MS / MS measurement can be performed. In addition, by reconstructing the MS / MS spectrum with the main isotope peaks selected and creating one product ion spectrum, the mass accuracy is not reduced compared to the case of selecting only monoisotopic ions. A sensitive spectrum can be obtained.

  (12) According to the invention described in claim 12, when an ion source that continuously generates ions is used as the ion source, by adopting a time-of-flight mass spectrometer in the first TOFMS, Isotope peaks can be selected and MS / MS measurements can be made. In addition, by reconstructing the MS / MS spectrum with the main isotope peaks selected and creating one product ion spectrum, the mass accuracy is not reduced compared to the case of selecting only monoisotopic ions. A sensitive spectrum can be obtained.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(Embodiment 1)
FIG. 1 is a block diagram showing a first embodiment of the present invention. (A) is the figure which looked at the apparatus in the Z direction, (b) is the figure which looked at the arrow direction in (a). Dashed arrows are ion trajectories. In the figure, 50 is a first TOFMS, and 60 is a second TOFMS connected to the first TOFMS 50. A spiral orbit type TOFMS is used as the first TOFMS, and a reflective type TOFMS is used as the second TOFMS.

  Reference numeral 40 denotes a MALDI ion source that generates ions by laser beam irradiation. Reference numeral 41 denotes a deflector for causing the ions generated by the MALDI ion source 40 to be incident on the spiral orbit while being inclined. 42 is a sector electric field 1 for passing ions, 43 is a sector electric field 2 for passing ions passing through the sector electric field 1, 44 is a sector electric field 3 for passing ions passing through the sector electric field 2, and 45 is a sector electric field 3 for passing ions through the sector electric field 3. A sector electric field 4 that allows ions to pass therethrough.

  Reference numeral 46 denotes a detector 1 that detects ions that have passed through the electric sector 45. The detector 1 is configured to be movable in the direction shown in the figure. 46 is an ion gate that receives ions that have passed through the first TOFMS and allows only specific ions to pass through, and 47 is a collision chamber that cleaves the ions that have passed through the ion gate 46. Reference numeral 48 denotes a reflected electric field that reflects incident ions. Reference numeral 49 denotes a detector 2 that detects ions reflected by the reflected electric field 48. The operation of the apparatus configured as described above will be described as follows.

  The sample is ionized by the MALDI ion source 40 and accelerated by a pulse voltage. So far, it is the same as that of the prior art. The angle of the ions emitted from the MALDI ion source 40 is adjusted by the deflector 41 so as to be put on the spiral trajectory. Then, it enters the sector electric field 1. The ions sequentially pass through the sector electric fields 1 to 4 and make one round. At this time, since the position in the Z direction is deviated from the previous round, it moves in the Z direction while repeating the rounds.

  In the case of MS measurement, ions are detected using the detector 1 arranged on the orbit. According to this, ion detection (MS measurement) during flight can be performed. In the case of MS / MS measurement, the detector 1 is removed from the ion trajectory, and the ions are caused to travel straight toward the ion gate 46. When the ion gate voltage is off, ions can pass through the ion gate 46 and cannot pass when it is on.

  The ion gate 46 is turned off only when a precursor ion to be selected from the ions that have finished the last round passes, and an isotope peak having the precursor ion is selected. The selected precursor ions enter the collision chamber 47 and are cleaved by collision with the internal collision gas. Precursor ions that have not been cleaved and product ions that have been cleaved pass through the reflected electric field 48 and are detected by the detector 2. Since the time for turning back the reflected electric field 48 is different from the mass of the precursor ion, the precursor ion and the precursor ion and the product ion of each cleavage path can be subjected to mass analysis.

The above operation is performed for the main isotope ions of the precursor ion. The spectrum of the product ion when the precursor ion of mass X is selected is called PS _X. Similarly, PS _M , PS _{M + 1} , PS _{M + 2} ... Are as shown in FIG. FIG. 2 is a diagram showing a spectrum of product ions. To match the mass axis of the product ion on the spectrum regardless of the mass of the precursor ion, the time of flight T1 _{, X} in the _first TOFMS of the precursor ion is subtracted from the time-of-flight spectrum of each spectrum, and the intensity is calculated. Add them together.

That is, the sequence of the first embodiment will be described as follows.
1) One isotope ion of the precursor ion is selected by the ion gate.
2) The selected precursor ion is cleaved to obtain a product ion spectrum.
3) The above 1) and 2) are repeated to cleave a plurality of isotope ions of the precursor ion to obtain a product ion spectrum.
4) The spectrum acquired in 3) is changed to the time-of-flight axis of the reflection type time-of-flight mass spectrometer, and the product ion spectrum is synthesized.
5) Change the time-of-flight axis of the synthesized product ion spectrum to the mass axis.

According to Embodiment 1 described above, when a MALDI ion source is used as an ion source, an isotope peak is selected by an ion gate by adopting a time-of-flight mass spectrometer in the first TOFMS, MS / MS measurement can be performed. In addition, by reconstructing the MS / MS spectrum with the main isotope peaks selected and creating one product ion spectrum, the mass accuracy is not reduced compared to the case of selecting only monoisotopic ions. A sensitive spectrum can be obtained.
(Embodiment 2)
The configuration of this embodiment is the same as that shown in FIG. The operation of the present embodiment is almost the same as that of Embodiment 1, and the operation during the synthesis of the product ion spectrum is different. Since the synthesis of the product ion spectrum is performed by acquiring a plurality of spectra, there is a possibility that each spectrum has a different intensity. Therefore, at the time of synthesis, an appropriate coefficient is applied to the intensity axis so that the intensity ratio of the precursor ion peak in PS _X matches the isotope ratio of the precursor ion.

That is, the sequence of the second embodiment will be described as follows.
1) One isotope ion of the precursor ion is selected by the ion gate.
2) The selected precursor ion is cleaved to obtain a product ion spectrum.
3) The above 1) and 2) are repeated to cleave a plurality of isotope ions of the precursor ion to obtain a product ion spectrum.
4) The spectrum acquired in 3) is changed to the time-of-flight axis of the reflection type time-of-flight mass spectrometer, and the product ion spectrum is synthesized.
5) Change the time-of-flight axis of the synthesized product ion spectrum to the mass axis.
(Embodiment 3)
FIG. 3 is a block diagram showing a third embodiment of the present invention. The same components as those in FIG. 1 are denoted by the same reference numerals. (A) is the figure which looked at the apparatus from the Z direction, (b) is the figure which looked at the arrow direction in (a). In the figure, 70 is an ion source that continuously generates ions, 71 is an ion transport part that transports ions generated by the ion source 70, and 72 is a vertical that accelerates ions that have been transported through the ion transport part 71 in the vertical direction. It is an acceleration part. The ions accelerated by the vertical accelerating unit 72 are deflected by the subsequent deflector 41 in accordance with the helical angle of the helical trajectory type TOFMS and enter the sector electric field 1. Other configurations are the same as those shown in FIG.

That is, the sequence of the third embodiment will be described as follows.
1) One isotope ion of the precursor ion is selected by the ion gate.
2) The selected precursor ion is cleaved to obtain a product ion spectrum.
3) The above 1) and 2) are repeated to cleave a plurality of isotope ions of the precursor ion to obtain a product ion spectrum.
4) The spectrum acquired in 3) is changed to the time-of-flight axis of the reflection type time-of-flight mass spectrometer, and the product ion spectrum is synthesized.
5) Change the time-of-flight axis of the synthesized product ion spectrum to the mass axis.

  According to this embodiment, when an ion source that continuously generates ions is used as the ion source, an isotope peak is obtained at the ion gate by adopting a time-of-flight mass spectrometer in the first TOFMS. You can select and make MS / MS measurements. In addition, by reconstructing the MS / MS spectrum with the main isotope peaks selected and creating one product ion spectrum, the mass accuracy is not reduced compared to the case of selecting only monoisotopic ions. A sensitive spectrum can be obtained.

  According to the present invention, by applying an arbitrary constant so that the isotope ratio of the precursor ion in the product ion spectrum matches the calculated value, and then synthesizing, a spectrum with good sensitivity can be obtained without reducing mass accuracy. Obtainable.

Further, according to the present invention, by using a multi-turn type time-of-flight mass spectrometer for the first TOFMS, the time of flight can be extended and the resolution can be improved.
Further, according to the present invention, by using a spiral orbit type time-of-flight mass spectrometer for the first TOFMS, the time of flight can be extended and the resolution can be improved.

Further, according to the present invention, the MALDI method can be used as an ionization method with an ion source.
Further, according to the present invention, the time convergence of ions can be maintained by using the delayed extraction method as a means for accelerating ions.

  As described above in detail, according to the present invention, the selectivity of precursor ions can be improved as compared with the prior art by using a helical orbital TOFMS for the first TOFMS. As a result, in the TOF / TOF apparatus, the interpretation of the product ion spectrum is simplified and the mass accuracy can be improved.

It is a block diagram which shows the 1st Example of this invention. It is a figure which shows the spectrum of a product ion. It is a block diagram which shows the 3rd Embodiment of this invention. It is explanatory drawing of linear type | mold TOFMS. It is explanatory drawing of reflection type TOFMS. It is explanatory drawing of a MALDI method and a delay extraction method. It is explanatory drawing of vertical acceleration type TOFMS. It is explanatory drawing of MS / MS measurement. It is a figure which shows the structural example of the MS / MS apparatus which connected TOFMS in series. It is explanatory drawing of an isotope peak. It is a figure which shows the isotope peak of product ion. It is a figure which shows the isotope peak of neutral particle. It is a figure which shows the intensity ratio of each combination of precursor ion, and the isotope peak ratio of precursor ion. It is the figure which looked at FIG. 13 from the viewpoint of product ion. It is a figure which shows the product ion spectrum in a TOF / TOF apparatus.

Explanation of symbols

40 MALDI ion source 41 Deflector 42 Fan electric field 1
43 Fan-shaped electric field 2
44 Electric sector 3
45 Fan-shaped electric field 4
46 Detector 1
47 Collision chamber 48 Reflected electric field 49 Detector 2
50 1st TOFMS
60 Second TOFMS

Claims (12)

An ion source for ionizing a sample, an acceleration means for accelerating ions in a pulsed manner, a time-of-flight mass spectrometer, an ion gate for selecting ions having a specific mass, and a means for cleaving selected ions Using a tandem mass spectrometer consisting of a reflective time-of-flight mass spectrometer that includes a reflected electric field and a detector that detects ions that have passed through the reflective time-of-flight mass spectrometer, the following operations are performed: A product ion spectrum creating method characterized by:
1) One isotope ion of the precursor ion is selected by the ion gate.
2) The selected precursor ion is cleaved to obtain a product ion spectrum.
3) The above 1) and 2) are repeated to cleave a plurality of isotope ions of the precursor ion to obtain a product ion spectrum.
4) The spectrum acquired in 3) is changed to the time-of-flight axis of the reflection type time-of-flight mass spectrometer, and the product ion spectrum is synthesized.
5) Change the time-of-flight axis of the synthesized product ion spectrum to the mass axis. An ion source for ionizing a sample; a transport means for transporting ions; an acceleration means for accelerating ions in a direction perpendicular to the transport direction; a time-of-flight mass spectrometer; and a specific mass An ion gate for selecting ions; means for cleaving the selected ions; a reflective time-of-flight mass spectrometer including a reflected electric field; and a detector for detecting ions that have passed through the reflective time-of-flight mass spectrometer. A product ion spectrum creation method characterized by using a configured tandem mass spectrometer and performing the following operations.
1) One isotope ion of the precursor ion is selected by the ion gate.
2) The selected precursor ion is cleaved to obtain a product ion spectrum.
3) The above 1) and 2) are repeated to cleave a plurality of isotope ions of the precursor ion to obtain a product ion spectrum.
4) The spectrum acquired in 3) is changed to the time-of-flight axis of the reflection type time-of-flight mass spectrometer, and the product ion spectrum is synthesized.
5) Change the time-of-flight axis of the synthesized product ion spectrum to the mass axis.   3. The product according to claim 1, wherein the product ion spectrum is synthesized by applying an arbitrary constant so that the isotope ratio of the precursor ion in the product ion spectrum matches the calculated value. Ion spectrum creation method.   4. The time-of-flight mass spectrometer, which is composed of a plurality of sector electric fields and makes multiple rounds of the same orbit, is used for the time-of-flight mass spectrometer of the tandem mass spectrometer. Product ion spectrum creation method described in 1.   4. The time-of-flight mass spectrometer, which is composed of a plurality of electric sector fields and causes ions to fly in a spiral orbit, is used as the time-of-flight mass spectrometer of the tandem mass spectrometer. 5. A method for creating a product ion spectrum according to the above.   If the first time-of-flight mass spectrometer is a spiral orbital time-of-flight mass spectrometer, the ions are pulsed to adjust the angle of incidence of the ions on the spiral orbital time-of-flight mass spectrometer. 6. A method for producing a product ion spectrum according to claim 1, wherein means for deflecting ions is provided between the means for measuring and the spiral orbit type time-of-flight mass spectrometer.   7. The method for producing a product ion spectrum according to claim 1, wherein the ionization method at the ion source is a MALDI method.   8. The method of producing a product ion spectrum according to claim 7, wherein a delayed extraction method is used as means for accelerating ions.   The detector according to claim 1, further comprising another detector movable between the ion trajectory and the ion trajectory between the time-of-flight mass spectrometer and the reflected electric field. Product ion spectrum creation method.   The product ion spectrum creation method according to any one of claims 1 to 9, wherein the means for cleaving is a CID method performed by filling a collision chamber with a gas. An ion source for ionizing a sample, an acceleration means for accelerating ions in a pulsed manner, a time-of-flight mass spectrometer, an ion gate for selecting ions having a specific mass, and a means for cleaving selected ions In a product ion spectrum generator using a tandem mass spectrometer composed of a reflective time-of-flight mass spectrometer including a reflected electric field and a detector that detects ions that have passed through the reflective time-of-flight mass spectrometer ,
Select one precursor ion isotope ion in the ion gate, cleave the selected precursor ion, acquire the product ion spectrum, cleave multiple isotope ions of the precursor ion, and acquire the product ion spectrum The spectrum is changed to the time-of-flight axis of the reflection type time-of-flight mass spectrometer, the product ion spectrum is synthesized, and the time-of-flight axis of the synthesized product ion spectrum is changed to the mass axis. A product ion spectrum generator. An ion source for ionizing a sample; a transport means for transporting ions; an acceleration means for accelerating ions in a direction perpendicular to the transport direction; a time-of-flight mass spectrometer; and a specific mass An ion gate for selecting ions; means for cleaving the selected ions; a reflective time-of-flight mass spectrometer including a reflected electric field; and a detector for detecting ions that have passed through the reflective time-of-flight mass spectrometer. In the product ion spectrum creation device using the configured tandem mass spectrometer,
Select one precursor ion isotope ion in the ion gate, cleave the selected precursor ion, acquire the product ion spectrum, cleave multiple isotope ions of the precursor ion, and acquire the product ion spectrum The spectrum is changed to the time-of-flight axis of the reflection type time-of-flight mass spectrometer, the product ion spectrum is synthesized, and the time-of-flight axis of the synthesized product ion spectrum is changed to the mass axis. A product ion spectrum generator.

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