JP2001028253A - Vertical acceleration time-of-flight mass spectrometer - Google Patents

Abstract

(57) Abstract: There is provided an OA-TOFMS that can use a thin electrostatic sector electric field even when an ion pulse is obliquely incident on a TOF spectroscopic section. An ion reservoir for introducing ions from an external ion source, an ion accelerating unit for extracting ions from the ion reservoir in a pulsed manner and accelerating the ions, and detecting an ion to which an accelerated ion pulse enters after flying a predetermined distance A time-of-flight spectrometer that measures the time required for the ion pulse extracted from the ion reservoir to reach the ion detector, and a vertical electrostatic sector electric field installed inside the time-of-flight spectrometer. In an accelerated time-of-flight mass spectrometer, when ions extracted from the ion reservoir pass through the electrostatic sector electric field, the ions move on a plane orthogonal to the rotation axis of the electrostatic sector electric field, The electrostatic sector electric field was arranged obliquely with respect to the ion accelerator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a vertical acceleration time-of-flight mass spectrometer (OA-TOFMS; Orthogonal Acc.
OA-TOF that can reduce the thickness of an electrostatic sector electric field installed inside a time-of-flight spectrometer
Regarding MS.

[0002]

2. Description of the Related Art In OA-TOFMS, an ion beam from an ion source that continuously generates ions is introduced into an ion reservoir, and the ion beam is accelerated in a pulsed manner in a direction intersecting with the ion beam introduction direction. This is a device for measuring the time until the detected ion pulse is detected by the ion detector and performing mass spectrometry.

FIG. 1 shows an electrostatic sector electric field type OA-TOF.
FIG. 3 is a schematic view of the configuration of the MS as viewed from the X-axis direction. In the figure, 1 is an electron impact (EI) for continuously generating positive ions,
Chemical ionization (CI), fast atom bombardment (FAB), electrospray (ESI), inductively coupled plasma (IC)
P) or an external ion source.

[0004] ion beam emitted from an external ion source 1 in the Y-axis direction is a converging lens 2 positive potential V _F is applied is converged in the Z-axis direction, the ion reservoir having an effective length of y ₀ 3 is introduced. Push-out near ion reservoir 3
A plate 4 is provided, and an ion extraction grid 5 having a ground potential and an exit grid 6 to which a negative potential V ₂ is applied are provided at a position facing the push-out plate 4. An electric field for pushing out ions is formed in a direction (Z-axis direction) crossing the introduction direction (Y-axis direction).

[0005] Push-out plate 4 and the ion extraction grid 5 is not face apart 2S ₀ together, the ion beam from an external ion source 1, Push-out plate 4
Is introduced into the ion reservoir 3 which is a space between the ion extraction grid 5 and the ion extraction grid 5. Further, the ion extraction grid 5 and the exit grid 6 face each other with a distance D therebetween.

When a positive voltage (amplitude V _P ) push-out pulse voltage 7 is applied to the push-out plate 4, the push-out
An electric field gradient is instantaneously formed in the so-called ion accelerating section 8 between the plate 4, the ion extraction grid 5, and the exit grid 6, and the ions in the ion reservoir 3 are simultaneously accelerated in the Z-axis direction to be ion pulses as ion pulses. Discharged from
After passing through the first electrostatic sector electric field 9 and the second electrostatic sector electric field 10 having a thickness T provided at opposing positions,
It reaches the ion detector 11 composed of a micro channel plate (MCP) or the like.

[0007] The flight direction of the ion pulse is as follows.
Strictly speaking, when ions are introduced into the ion reservoir 3, they have a predetermined velocity in the Y-axis direction, and therefore, between the push-out plate 4, the ion extraction grid 5, and the exit grid 6, that is, Even if the ions are accelerated in the Z-axis direction by the electric field generated in the ion acceleration section 8, the final flight direction of the ions is in an oblique direction shifted from the Z-axis direction by a certain angle θ in the Y-axis direction.

By the way, when receiving the above acceleration, the ions contain Pu.
Since a constant energy corresponding to the potential difference between the sh-out plate 4 and the outlet grid 6 is given equally, at the end of acceleration, ions with smaller mass have a higher velocity and ions with larger mass have a lower velocity. As a result of such a speed difference, T formed by two electrostatic sector electric fields
While the ions fly through the OF spectroscopic unit 12, the ions are dispersed in mass, and the ions arrive at the ion detector 11 in order from the lightest ion, and the mass spectrum is measured.

FIG. 2 shows the electrostatic sector electric field type OA-T.
It is the schematic diagram which looked at the structure of OFMS toward the Z-axis direction. Ions that have entered the ion reservoir 3 from the ion source (not shown) in the Y-axis direction (the direction perpendicular to the plane of FIG. 2) are pushed by the push-out pulse 7 applied to the push-out plate 4. Discharged from reservoir 3 in the Z-axis direction,
It is accelerated by the electric field gradient formed from the ion extraction grid 5 to the exit grid 6, and reaches the ion detector 11 via the first electrostatic sector electric field 9 and the second electrostatic sector electric field 10.

At this time, the 2 constituting the TOF spectroscopic unit 12
The two electrostatic sector electric fields 9 and 10 have the same optical system dimensions. That is, each sector electric field center rotation radius r _e , inner electrode rotation radius r _a , outer electrode rotation radius r _b , electric field rotation angle φ _e , free space D
₁ , D ₂ , D ₃ and D ₄ are in an equal relationship. Each of these two electrostatic sector electric fields has triple convergence (time, space and energy convergence) independently.

Then, one triple convergence point F ₁ of the first electrostatic sector electric field 9 is made to coincide with the spatial convergence point of the ion accelerating unit 8 and the other triple convergence point F ₁ of the first electrostatic sector electric field 9 is set. ₂ is matched to one triple convergence point of the second electrostatic sector electric field 10. Also, the second electrostatic sector electric field 1
The other triple convergence point F ₃ of 0 is matched with the detection surface of the ion detector 11. By arranging the ion accelerator 8, the electrostatic sector electric fields 9 and 10, and the ion detector 11 in such a positional relationship, a high-resolution TOFMS spectrum can be measured.

[0012]

In such a configuration, a problem when the electrostatic sector electric field is used in the OA-TOFMS is that when ions are pushed out from the ion accelerator 8, a certain angle from the Z-axis direction occurs. Flying in the oblique direction shifted in the Y-axis direction by θ and obliquely incident on the rotation axis of the electrostatic sector electric field, the thickness T of the electrostatic sector electric field in the Y-axis direction is required to correctly bend the flight trajectory of ions. Must be made large, and the size of the electrostatic sector electric field becomes very large.

In view of the above, an object of the present invention is to use an electrostatic sector electric field having a small thickness T even when an ion pulse is incident obliquely with respect to the axial direction (Z-axis direction) of the TOF spectroscopic section 12. To provide an OA-TOFMS capable of performing such operations.

[0014]

In order to achieve this object, a TOFMS according to the present invention comprises an ion reservoir for introducing ions from an external ion source, and an ion acceleration for extracting ions from the ion reservoir in a pulsed manner and accelerating the ions. Unit, an ion detector into which the accelerated ion pulse flies after traveling a predetermined distance, and a time-of-flight spectroscopic unit that measures the time until the ion pulse extracted from the ion reservoir reaches the ion detector, A vertical acceleration time-of-flight mass spectrometer comprising an electrostatic sector electric field installed inside a time-of-flight spectroscopic unit, wherein the ions extracted from the ion reservoir pass through the electrostatic sector electric field, Moves on a plane perpendicular to the rotation axis of the electrostatic sector electric field,
The electrostatic sector electric field is disposed obliquely with respect to the ion acceleration unit.

Further, a plurality of electrostatic sector electric fields are provided so that ions sequentially pass through the time-of-flight spectroscopy unit,
The plurality of electrostatic sector electric fields are arranged so that the rotation axes of the individual electrostatic sector electric fields are parallel to each other.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 shows an embodiment of the electrostatic sector electric field type OA-TOFMS according to the present invention, and is a view in which the arrangement of two electrostatic sector electric fields placed in the TOF spectroscopy unit is developed on a plane. In the drawing, an ion beam emitted from an external ion source (not shown) is converged in the Z-axis direction by a converging lens (not shown) and introduced into the ion reservoir 3 along the central axis of the ion reservoir 3. You.

A push-out plate 4 is provided near the ion reservoir 3.
And a distance 2S from the push-out plate 4 in the Z-axis direction.
₀ Only ion extraction grid 5 at ground potential away, outlet grid 6 to which a negative potential V ₂ is applied at a distance D further from the ion extraction grid 5 is provided. The push-out plate 4, the ion extraction plate 5, and the exit plate 6 cooperate with each other to form an ion acceleration unit 8.

When a positive voltage (amplitude V _P ) push-out pulse voltage 7 is applied to the push-out plate 4, the push-out
An electric field gradient is instantaneously formed in the so-called ion accelerator 8 between the plate 4, the ion extraction grid 5, and the exit grid 6, and the ions in the ion reservoir 3 are simultaneously accelerated in the Z-axis direction and discharged from the ion reservoir 3. After passing through a first electrostatic sector electric field 9 and a second electrostatic sector electric field 10 provided at opposing positions, it reaches an ion detector 11 constituted by a micro channel plate (MCP) or the like. .

In such a configuration, the ion accelerator 8
The ion pulse emitted in the Z-axis direction from to the TOF spectroscopy unit 12 originally has a velocity component in the Y-axis direction when the ions are introduced into the ion reservoir 3, and therefore, is present from the Z-axis direction. The aircraft flies in an oblique direction shifted in the Y axis direction by an angle θ. However, the conventional electrostatic sector electric fields 9 and 10 are:
Since it was installed on the same coordinate system as the casing of the mass spectrometer and the ion accelerator 8, in order to absorb the displacement in the Y-axis direction due to this flight angle θ, the thickness of the electric field was By setting T to be thick, the flight path of the ion pulse incident on the electric field is bent.

Such electrostatic sector electric fields 9 and 10
In the present invention, as shown by the solid line frame, the incident surface of the electrostatic sector electric field is arranged to be exactly perpendicular to the incident direction of the ion pulse. In other words, when the ions extracted from the ion reservoir 3 pass through the electrostatic sector electric fields 9 and 10, they move on a plane orthogonal to the rotation axis 14 of the electrostatic sector electric field. Like moving
This means placing electrostatic sector electric fields 9 and 10.

Thus, the electrostatic sector electric fields 9 and 10
Is arranged obliquely by a predetermined angle θ with respect to the coordinate system of the casing of the mass spectrometer and the ion accelerator 8, but the ion pulse is directed along the direction of the ion path of the electrostatic sector electric field. To be able to enter straight
The problem that the thickness T of the electric field has to be set large because the ion pulse is obliquely incident on the electric field as in the related art is solved, and the use of an electrostatic sector electric field having a small thickness T and a light weight is solved. Will be able to

At this time, the rotation axes 14 of the electrostatic sector electric fields 9 and 10 are in a parallel relationship with each other. FIG.
FIG. 3 is a perspective view illustrating a method of arranging such an electrostatic sector electric field in an easy-to-understand manner.

In general, as the thickness of the electrostatic sector electric field increases and the overall size increases, it becomes more difficult to maintain the uniformity of the electric field intensity. As a result, OA-TOFM
This causes a reduction in the spectral resolution of S. However, as in the present invention, if the central axis of the electrostatic sector electric field is set obliquely at a predetermined angle θ with respect to the axial direction (Z-axis direction) of the TOF spectroscopic unit in accordance with the incident direction of the ion pulse, The thickness T of the electric field does not increase, and the size of the entire electric field can be reduced. As a result, the electric field intensity can be easily maintained uniform, and a decrease in the spectral resolution of OA-TOFMS can be prevented.

In the above embodiment, the number of electrostatic sector electric fields placed in the TOF spectroscopy unit is two. However, the present invention is not limited to this value, and one or three or more static sector electric fields are used. It goes without saying that the present invention can also be applied to a case where the electric sector electric field is installed in the TOF spectroscopy unit.

[0025]

As described above, according to the electrostatic sector electric field type OA-TOFMS of the present invention, the ion pulse extracted from the ion reservoir moves on a plane orthogonal to the rotation axis of the electrostatic sector electric field. As described above, since the electrostatic sector electric field is arranged so as to be inclined by the predetermined angle θ with respect to the ion accelerating unit, the thickness of the electric field does not increase, and the size of the entire electric field can be reduced. As a result, the electric field strength can be easily maintained uniform, and OA-TOFMS
Can be prevented from deteriorating.

[Brief description of the drawings]

FIG. 1 is a diagram showing a conventional vertical acceleration time-of-flight mass spectrometer.

FIG. 2 is a diagram showing a conventional vertical acceleration time-of-flight mass spectrometer.

FIG. 3 is a view showing one embodiment of a vertical acceleration time-of-flight mass spectrometer according to the present invention.

FIG. 4 is a perspective view showing one embodiment of a vertical acceleration time-of-flight mass spectrometer according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... External ion source, 2 ... Converging lens, 3 ... Ion pool, 4 ... Push-out plate, 5 ... Ion extraction grid, 6 ... Exit grid, 7 ... Push-out pulse, 8 ...
・ Ion acceleration part, 9 ・ ・ ・ First electric field of electrostatic sector, 10 ・ ・
A second electrostatic sector electric field, 11 ... an ion detector, 12
... TOF spectroscopy unit, 13 ... rotation axis of conventional electrostatic sector electric field, 14 ... rotation axis of electrostatic sector electric field of the present invention.

Claims (2)

[Claims] 1. An ion reservoir for introducing ions from an external ion source, an ion accelerating section for extracting ions from the ion reservoir in a pulsed manner and accelerating the ions, and ions incident after the accelerated ion pulse flies a predetermined distance. It consists of a detector, a time-of-flight spectrometer that measures the time required for the ion pulse taken out of the ion reservoir to reach the ion detector, and an electrostatic sector electric field installed inside the time-of-flight spectrometer. In the vertical acceleration time-of-flight mass spectrometer, when ions extracted from the ion reservoir pass through the electrostatic sector electric field, the ions move on a plane orthogonal to the rotation axis of the electrostatic sector electric field. A vertical acceleration time-of-flight mass spectrometer, wherein the electrostatic sector electric field is disposed obliquely with respect to the ion acceleration section. 2. A plurality of electrostatic sector electric fields are provided so that ions sequentially pass through said time-of-flight spectroscopy unit. The vertical acceleration time-of-flight mass spectrometer according to claim 1, wherein the mass spectrometer is arranged so as to be parallel.