JPH07282772A - Fourier transform mass spectrometer - Google Patents

Abstract

(57) [Abstract] [Purpose] A novel Fourier transform that can set the orbital radius of the cyclic ion current to a large value and can properly maintain the resonance signal waveform, and can be suitably applied to high-mass range substances. Obtain a conversion mass spectrometer. [Structure] A high-vacuum analyzer 10, an ion source 12 arranged outside the analyzer, and an ion acceleration / focusing system 14 provided between them. In the ion accelerating / focusing system 14, the ions from the ion source 12 are accelerated by the accelerating electric field section 24 and introduced into the magnetic field B, thereby forming a noncoherent annular ion current 18 due to circular motion. A part of the circular orbit of the non-coherent annular ion current is excised by an alternating electric field of the cyclotron resonance frequency ω _c of the ion to make the ion coherent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Fourier transform mass spectrometer for quantitatively analyzing various samples, for example, biopolymer components such as proteins and peptides from their ions.

[0002]

2. Description of the Related Art Generally, ions of various sample components are forced to perform a circular motion in a static magnetic field in a high vacuum analyzer, that is, an annular ion beam (current) is formed, and this annular ion current is passed through a signal transmitter. A so-called Fourier transform mass spectrometer is known which is configured to quantify the mass of the ion, that is, the sample component by exciting the ion cyclotron resonance and Fourier transforming the resonance signal.

In the Fourier transform, excitation and coherence of cyclotron motion of ions are simultaneously performed by a signal oscillator, and the signal receiver detects a resonance frequency by the coherent annular ion current. Has been done.

Therefore, according to this type of mass spectrometer,
By ionizing various samples, these components can be analyzed relatively easily.

[0005]

However, the above-mentioned conventional Fourier transform mass spectrometer has the following basic drawbacks.

That is, in the conventional Fourier transform mass spectrometer (hereinafter referred to as a conventional device), ionization excitation and coherentization of the sample component are performed at the same place in a high vacuum cell placed in a resonance magnetic field. But in this case
First, in conclusion, this conventional device can be suitably applied to low-mass range substances such as gas and volatile liquids, but to high-mass range substances such as biopolymers such as proteins and peptides. Was originally maladaptive.

That is, the Fourier transform in this type of device is such that the Fourier transform means such as a signal transmitter and a receiver are appropriately arranged and function with respect to the coherent annular ion current formed in the resonance magnetic field. However, in the case of high mass region material ions, when the resonance frequency is low and the orbital radius of the annular ion current is small, and especially when the ion density is high, it is affected by space charge. Since the resonance signal waveform is broken, the arrangement of the Fourier transform means is restricted, and the function (signal sensitivity, etc.) is unavoidably deteriorated.

Therefore, an object of the present invention is to set a large orbital radius of a cyclic ion current and to appropriately maintain a resonance signal waveform so that the present invention can be suitably applied to a high mass region material. Another object is to provide a Fourier transform mass spectrometer.

[0009]

In order to achieve the above object, a Fourier transform mass spectrometer according to the present invention excites an ion cyclotron resonance on an ion forcibly moving in a static magnetic field in a high vacuum analyzer. In the Fourier transform mass spectrometer for quantifying the mass of the ions by Fourier transforming the resonance signal, an ion source is provided outside the high vacuum analyzer, and the ions generated from the ion source are subjected to ion acceleration / It is characterized in that the injection is carried out on the ion circular orbit of the forced motion in the high vacuum analyzer via a focusing system.

In the above Fourier transform mass spectrometer, the ion accelerating / focusing system is an acceleration electric field section for deriving and accelerating ions from the ion source toward an ion circular orbit in the analyzer, and an acceleration electric field section for accelerating the ions. A proportional deflection electric field unit that advances the path of the ions in a changing magnetic field up to the circular orbit,
A curved deflection electric field part that puts the path of the ions passing through this proportional deflection electric field part on a circular orbit, and a correction deflection electric field part that further corrects the path of the ions passing through this curved deflection electric field part from the deviation on the circular orbit. It is possible that the acceleration voltage and the proportional, bending, and correction deflection voltages in each of the electric field portions are connected and swept.

In the ion accelerating / focusing system, the ions from the ion source are accelerated by the accelerating electric field section and introduced into the magnetic field, thereby forming a noncoherent annular ion current due to the circular motion. A portion of the circular orbit of the circular ion current can be cut by an alternating electric field at the cyclotron resonance frequency of the ion to make the ion coherent.

[0012]

According to the Fourier transform mass spectrometer of the present invention,
A circular ion current in the resonant magnetic field of the high vacuum analyzer causes an ion beam from an ion source located outside the analyzer to
It is formed by sufficiently accelerating and converging via an ion accelerating / focusing system and then injecting it into a resonance magnetic field. Therefore, even in the case of a substance having a high mass region, the circular ion current can form a sufficiently large orbital radius and can converge the beam thickness sufficiently thin. That is, the Fourier transform means can be properly arranged with respect to the annular ion current in the resonance magnetic field, and the function thereof is not impaired.

Moreover, in the Fourier transform mass spectrometer of the present invention, since the ion source is arranged outside as described above, various ionization methods can be easily applied and the residual gas in the analyzer can be easily removed. The advantage is that the generation of noise due to ionization can be completely eliminated. Further, since the inside of the analyzer can be easily maintained at a sufficiently high degree of vacuum by differential evacuation, collisions of ions can be prevented and the measurement time can be extended.

Further, in the present invention, in the conventional apparatus, the ionization to the cyclotron motion and the coherentization were simultaneously performed by the signal generator, whereas the ions were first accelerated to the magnetic field. Introducing a circular ion orbit to generate a noncoherent annular ion current due to the circular motion of the ion, and a portion of the circular orbit of this noncoherent annular ion current is ablated by the alternating electric field at the cyclotron resonance frequency of the ion Can be easily made coherent.

[0015]

Embodiments of the Fourier transform mass spectrometer according to the present invention will be described below in detail with reference to the accompanying drawings.

Referring to FIG. 1, the Fourier transform mass spectrometer according to the present invention is basically provided with a high vacuum analyzer 10, an ion source 12 arranged outside the analyzer 10, and an ion source 12 provided between them. And an ion accelerating / focusing system 14 that is used.

However, the ions (beams) 16 generated from the ion source 12 are appropriately injected into the analyzer 10 via the ion accelerating / focusing system 14, as will be described later, so that the ions are The beam 16 is the analyzer 10.
In the static magnetic field B inside, a forced circular motion is generated to form an incoherent annular ion current 18. The annular ion current 18 excites the ion cyclotron resonance in the signal transmitter 22. The resonance signal thus obtained is subjected to Fourier transform to quantitatively analyze the mass of the ion 16 or the sample component.

Therefore, the ion acceleration / focusing system 14 described above is used.
First, basically, an acceleration electric field section 24 for accelerating the ions (beams) 16 from the ion source 12 toward an ion circular orbit (annular ion current) 18 in the analyzer 10 and The path of the ion beam 16 accelerated by the accelerating electric field section 24 goes straight in the changing magnetic field up to the circular orbit 18, and the path of the ion beam 16 that has passed through the proportional deflection electric field section 26 passes through the circular orbit 18 The curved deflection electric field part 28 to be placed on the curved deflection electric field part 2
The circular orbit 18 of the ion beam 16 passing through
It is composed of a correction deflection electric field section 30 that corrects from the above deviation. Here, it is obvious that the acceleration electric field section 24 is configured as a normal structure to which the acceleration voltage Va is applied.

Therefore, in the ion accelerating / focusing system 14 thus constructed, the ions from the ion source 12 are accelerated by the accelerating electric field section 24 as shown in FIGS. 2 (a) and 2 (b). This is introduced into the magnetic field B, thereby forming an incoherent annular ion current 18 due to circular motion, and a part of the circular orbit of this incoherent annular ion current 18 is generated in the signal oscillator 22 by the cyclotron resonance frequency ω of the ion. Ions can be made coherent by cutting with an alternating electric field of _c . The resonance frequency ω _{c of the} coherent annular ion current 18 is measured by the signal receiver 20.

However, in the present invention, the other electric field portions except the acceleration electric field portion 24, that is, the proportional deflection electric field portion 26, the curved deflection electric field portion 28, and the correction deflection electric field portion 30.
Has a specific structure as described above. Therefore, these structures will be described with reference to FIGS. 3 and 4.

That is, generally, in FIG. 4, the ion beam 16 having a velocity v, a mass m, and an electric charge e generally travels straight in the electric field B in which the voltage Vd is applied in the gap d. On the street.

[0022]

[Equation 1]

[0023] (where, Va is the acceleration voltage, r _m is orbital radius of the annular ion current, B is the intensity of the magnetic field.) From these conditional expressions, straight to the conditions of conclusively the ion beam by: Represented.

[0024]

[Equation 2]

That is, each of the electric field portions 26, 2 of the present invention.
8, 30 are the voltages (declination voltages) Vd1, Vd2, V
The shape of d3 and the gaps d1, d2, d3 (not shown) are set so that the following expression is satisfied.

[0026]

[Equation 3]

That is, the proportional deflection electric field section 26 is formed such that its electrode plate is tapered toward the traveling direction of the ion beam 16, and the curved deflection electric field section 28 and the correction deflection electric field section 30 are enlarged and shown. (A) of FIG.
As is apparent from (b) and (c), a predetermined distance d is provided on the opposing surfaces of the pair of parallel resistance flat plates 32, 32 with the resistance film 33 interposed therebetween.
It is composed of a large number of linear electrodes 34 which are spaced apart from each other and arranged in parallel. With these configurations, the electric field portions 24, 26, 28, 30 have their respective applied voltages Va, V.
By connecting and sweeping d1, Vd2, and Vd3, respectively, the ion beam 16 from the ion source 12 is circularly orbitally (annular ion current) 18 on the orbital radius r _m set by the equations (3) and (4). On top, it can be matched exactly.

As described above, in the present invention, the annular ion current in the resonance magnetic field of the high vacuum analyzer is sufficiently accelerated and converged in the ion beam from the external ion source before being injected into the resonance magnetic field. It is formed by Therefore, even if the ion beam is from a high-mass region material, the annular ion current can form a sufficiently large orbital radius and can also converge the beam thickness sufficiently thin. That is, the Fourier transform means can be properly arranged with respect to the annular ion current in the resonance magnetic field, and the function thereof is not impaired. Therefore, according to the present invention, a relatively simple and inexpensive Fourier transform mass spectrometer of this kind can be suitably used even in the field of high mass range substances which were conventionally not adapted. .

Moreover, in the present invention, since the ion source can be arranged outside as described above, various ionization methods can be easily applied, and noise due to ionization of the residual gas in the analyzer can be achieved. The advantage is that the occurrence can be completely eliminated. In addition, since the inside of the analyzer can be easily maintained at a sufficiently high degree of vacuum by differential evacuation, there are advantages that the collision of ions can be prevented and the measurement time can be extended.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and many design changes can be made without departing from the spirit thereof.

[0031]

As described above, the Fourier transform mass spectrometer according to the present invention excites an ion cyclotron resonance in an ion forcibly circularly moving in a static magnetic field in a high vacuum analyzer, and Fourier transforms the resonance signal. In a Fourier transform mass spectrometer that quantifies the mass of the ions by converting, an ion source is provided outside the high vacuum analyzer, and the ions generated from this ion source are converted into the high vacuum through an ion accelerating focusing system. The annular ion current is configured to be sufficiently accelerated and converged by an ion beam from an external ion source before being injected into the resonance magnetic field by being configured to be injected on the ion circular orbit of the forced motion in the analyzer. As a result, even if the ion beam is from a high mass region material, the annular ion current has a sufficiently large orbital radius. Together may form the beam thickness can also be converged sufficiently thin. That is, the Fourier transform means can be properly arranged with respect to the annular ion current in the resonance magnetic field, and its function is not impaired.

Therefore, according to the present invention, it is possible to construct a Fourier transform mass spectrometer of this kind relatively easily and inexpensively, and it is also suitable for the field of high mass range substances, which was conventionally unsuitable. It is possible to use. Moreover, in the present invention, since the ion source can be arranged outside as described above, various ionization methods can be easily applied and noise generation due to ionization of the residual gas in the analyzer can be completely eliminated. Further, since the inside of the analyzer can be easily maintained at a sufficiently high degree of vacuum by differential evacuation, advantages such as prevention of ion collision and extension of measurement time can be obtained together.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a Fourier transform mass spectrometer according to the present invention.

2A and 2B are diagrams showing ion beam coherence in an analyzer, wherein FIG. 2A is an explanatory diagram showing a ring ion current, and FIG. 2B is an explanatory diagram showing a ring ion current being coherent.

FIG. 3 shows a structure of a parallel resistance flat plate forming a linear multipolar electric field used for the bending and correction deflection electric field section shown in FIG. 1, (a) is a front view of one end of the flat plate, 8A is a side view of the inner surface of the flat plate, and FIG. 14C is a front view of the other end of the flat plate.

4 is an explanatory diagram showing a path of an ion beam in the electric field shown in FIG.

[Explanation of symbols]

 10 high vacuum analyzer 12 ion source 14 ion acceleration / focusing system 16 ion beam 18 annular ion current 20 signal detector 22 signal converter 24 acceleration electric field section 26 proportional deflection electric field section 28 curved deflection electric field section 30 correction deflection electric field section 32 parallel Resistor plate 33 Resistive film 34 Linear electrode

Claims (3)

[Claims] 1. A Fourier transform mass spectrometer for quantifying the mass of an ion by exciting an ion cyclotron resonance in an ion that makes a forced circular motion in a static magnetic field in a high vacuum analyzer and Fourier transforming the resonance signal. An ion source is provided outside the high vacuum analyzer, and ions generated from the ion source are injected into the forced motion ion circular orbit in the high vacuum analyzer via an ion acceleration / focusing system. A Fourier transform mass spectrometer characterized by comprising. 2. The ion accelerating / focusing system includes an accelerating electric field portion for deriving and accelerating ions from an ion source toward an ion circular orbit in an analyzer, and a path of the ions accelerated by the accelerating electric field portion. Proportional deflection electric field part that goes straight in the changing magnetic field up to the orbit, curved deflection electric field part that puts the path of the ion that passed through this proportional deflection electric field part on the circular orbit, and path of the ion that passes through this curved deflection electric field part A correction deflection electric field section for correcting the deviation from the deviation on the circular orbit, and the acceleration voltage and the proportional, bending, and correction deflection voltage in each electric field section are connected and swept. Fourier transform mass spectrometer described. 3. In an ion accelerating / focusing system, ions from an ion source are accelerated by an accelerating electric field section and introduced into a magnetic field, thereby forming a noncoherent annular ion current due to circular motion, and this noncoherent 3. The Fourier transform mass spectrometer according to claim 1, wherein a part of the circular orbit of the annular ion current is cut by an alternating electric field of the cyclotron resonance frequency of the ion to make the ion coherent.