JP2000285848A - Time-of-flight mass spectrometer - Google Patents

Abstract

[PROBLEMS] To provide a time-of-flight mass spectrometer capable of obtaining a high-resolution mass spectrum without increasing the size of the device. A decelerating electric field and then an accelerating electric field are provided on an orbit where ions fly, so that the ions decelerate and then accelerate without changing the flight direction of the ions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a time-of-flight mass spectrometer, and more particularly to a time-of-flight mass spectrometer capable of improving the resolution of a mass spectrum.

[0002]

2. Description of the Related Art A mass spectrometer is a device that causes ions generated from a sample to fly in a vacuum, separates ions having different masses during the flight, and records them as a spectrum.
The mass spectrometer includes a magnetic field type mass spectrometer that disperses ions using a sector magnetic field, and a quadrupole mass spectrometer (QMS) that selects (filters) ions by mass using a quadrupole electrode. ), A time-of-flight mass spectrometer (TOFMS) that separates ions by utilizing the difference in the flight time of ions depending on the mass, and the like are known.

[0003] Of these mass spectrometers, the magnetic field type mass spectrometer and the QMS are suitable for an ion source of a type that continuously generates ions, whereas the TOFMS generates ions in a pulsed manner. Compatible with all types of ion sources. Therefore, if a continuous ion source is to be used for TOFMS, it is necessary to devise how to use the ion source. Vertical acceleration time-of-flight mass spectrometer (OA-TOF)
MS (orthogonal acceleration TOFMS) is an example of TOFMS designed so that pulsed ions can be ejected from a continuous ion source.

FIG. 1 shows the configuration of a typical OA-TOFMS. OA-TOFMS is an electron impact (EI) ion source, a chemical ionization (CI) ion source, and a field desorption (FD).
A continuous ion source 1 such as an ion source, an electrospray (ESI) ion source, or a fast atom bombardment (FAB) ion source; an intermediate chamber 3 in which an ion guide 2 is placed; a condenser lens 4; It comprises a measuring chamber 9 in which components constituting an ion optical system such as an acceleration lens 6, a reflectron 7, and an ion detector 8 are placed.

In such a configuration, ions generated from the sample in the ion source 1 are guided to a high vacuum measurement chamber 9 by the ion guide 2 placed in the intermediate chamber 3. An orifice 10 is provided in a partition separating the intermediate chamber 3 and the measurement chamber 9, and ions guided from the ion guide 2 are shaped into an ion beam having a constant diameter by the orifice 10, and the measurement chamber 9 is introduced.

At the entrance of the measuring chamber 9, a condenser lens 4 is provided. The ion beam that has entered the measurement chamber 9 is converged by the condenser lens 4 and is placed in an elongated space along the gap between the extrusion electrode 5 and the acceleration lens 6.
And enters the acceleration lens 6 in parallel. The ion beam having a certain length moving near the pushing electrode 5 and the acceleration lens 6 is applied to the pushing electrode 5 and the acceleration lens 6.
By applying a pulsed acceleration voltage to the ion beam, it is accelerated in a pulsed manner in a direction perpendicular to the direction of the axis of entry of the ion beam, becomes an ion pulse, and is provided at a position facing the push-out electrode 5 and the acceleration lens 6. And start flying toward the reflectron 7.

The ions accelerated in the vertical direction enter the measuring chamber 9
Because the velocity at the time of introduction and the velocity provided by the push-out electrode 5 and the acceleration lens 6 in the direction perpendicular thereto are added, so that the airplane flies not vertically but slightly obliquely. Then, the light is reflected by the reflectron 7 and reaches the ion detector 8.

In the process of accelerating ions, the lighter the ions, the faster the speed becomes, and the heavier the ions, the slower the speed becomes.
The difference in ion mass appears as a difference in arrival time until reaching the ion detector 8, and the difference in ion mass can be separated as a difference in ion flight time.

As described above, the ion beam generated from the continuous ion source 1 is applied to the pushing electrode 5 and the acceleration lens 6.
By accelerating in a pulsed manner, a continuous ion source can be applied to TOFMS having compatibility with an ion source generated in a pulsed manner.

[0010]

In such a configuration, in TOFMS, a mass difference between ions appears as a difference in flight time of ions when flying in a predetermined space, so that a high resolution of a mass spectrum is obtained. The easiest way to get it was to have a long free flight space for ions.

In order to increase the free flight space of ions, there is a problem that the size of the apparatus must be increased.

An object of the present invention is to provide a TOFMS capable of obtaining a high-resolution mass spectrum without increasing the size of the apparatus in view of the above points.

[0013]

In order to achieve this object, the TOFMS according to the present invention provides a deceleration electric field and then an acceleration electric field on the orbit where the ions fly, so that the ions can be applied without changing the flight direction of the ions. It is characterized in that deceleration and then acceleration are performed.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows OA- according to the present invention.
1 illustrates an embodiment of TOFMS. In this embodiment, an electron impact (EI) ion source, a chemical ionization (CI)
A continuous ion source 1 such as an ion source, a field desorption (FD) ion source, an electrospray (ESI) ion source, a fast atom bombardment (FAB) ion source, and an intermediate chamber 3 in which an ion guide 2 is placed; It comprises a condensing lens 4, an extrusion electrode 5, an acceleration lens 6, a reflectron 7, and a measurement chamber 9 in which components constituting an ion optical system such as an ion detector 8 are placed.

In such a configuration, ions generated from the sample in the ion source 1 are guided to a high vacuum measurement chamber 9 by the ion guide 2 placed in the intermediate chamber 3. An orifice 10 is provided in a partition separating the intermediate chamber 3 and the measurement chamber 9, and ions guided from the ion guide 2 are shaped into an ion beam having a constant diameter by the orifice 10, and the measurement chamber 9 is introduced.

At the entrance of the measuring chamber 9, a condenser lens 4 is provided. The ion beam that has entered the measurement chamber 9 is converged by the condenser lens 4 and is placed in an elongated space along the gap between the extrusion electrode 5 and the acceleration lens 6.
And enters the acceleration lens 6 in parallel. The ion beam having a certain length moving near the pushing electrode 5 and the acceleration lens 6 is applied to the pushing electrode 5 and the acceleration lens 6.
By applying a pulsed acceleration voltage to the ion beam, it is accelerated in a pulsed manner in a direction perpendicular to the direction of the axis of entry of the ion beam, becomes an ion pulse, and is provided at a position facing the push-out electrode 5 and the acceleration lens 6. And start flying toward the reflectron 7.

The ions accelerated in the vertical direction are supplied to the measuring chamber 9
Because the velocity at the time of introduction and the velocity provided by the push-out electrode 5 and the acceleration lens 6 in the direction perpendicular thereto are added, so that the airplane flies not vertically but slightly obliquely. Then, the light is reflected by the reflectron 7 and reaches the ion detector 8.

In this embodiment, a deceleration lens 11 and an acceleration lens 12 are provided at a stage subsequent to the reflectron 7, that is, in an ion flight space between the reflectron 7 and the ion detector 8.
Is provided. With this configuration, ions flying in the linear flight space are once decelerated by the deceleration electric field generated by the deceleration lens 11 without changing the flight direction, and then accelerated by the acceleration lens 12. It is accelerated again to the original speed by the electric field. as a result,
The ions are left without any field, and moreover, the flight time can be increased, thus increasing the effective flight time.

FIG. 3 is an arrangement diagram of potentials on the flight trajectory of ions. The vertical axis of the figure represents the potential applied to the ions, and the horizontal axis of the figure represents the flight distance of the ions.

To explain the case where the sample ions are positive ions, an acceleration potential of + several hundred volts is applied to the push-out electrode 5. Further, a downward potential difference is provided from the pushing electrode 5 to the terminal end of the acceleration lens 6.
Accordingly, an electric field gradient is formed in the downward direction from the push-out electrode 5 to the end of the acceleration lens, and the ions are accelerated. At the terminal end of the accelerating lens 6, the potential is −several kilovolts. When the ions leave the accelerating lens 6, the potential flattens at a few kilovolts, so that the ions continue to fly at a constant speed.

When these ions enter the reflectron 7, the electric field of the ascending gradient of the reflectron 7 acts, and the ions slow down the flight speed. When the ions reach + several hundred volts or more, the direction of flight is reversed. It is pushed back out of Ron 7. The ions that exited reflectron 7
The flight continues at the same flight speed as before entering the reflectron 7, but the flight direction is substantially opposite.

Since the deceleration lens 11 and the acceleration lens 12 are provided between the reflectron 7 and the ion detector 8, the potential applied to the ions once rises when passing through the deceleration lens 11, When passing through the acceleration lens 12, the potential drops again to the original potential. The highest potential at this time must not exceed the ground potential because ions must pass from the deceleration lens 11 to the acceleration lens 12. Then, as the ions pass through both lenses, the flight speed of the ions is once reduced and then accelerated again to return to the original speed.

Such a deceleration lens 11 and an acceleration lens 1
By the action of 2, the effective flight distance of the ions is effectively extended, and the resolution of the mass spectrum can be improved without increasing the size of the TOFMS device.

On the other hand, when the sample ions are negative ions, the polarities of the potentials applied to the flight paths of the ions described above are all inverted.

In the present embodiment, the deceleration lens 11 and the acceleration lens 12 are provided after the reflectron 7, that is, between the reflectron 7 and the ion detector 8.
These installation locations are not necessarily limited to the latter stage of the reflectron 7. For example, Reflectron 7
, Ie, between the accelerating lens 6 and the reflectron 7 or the reflectron 7
May be installed in both the former stage and the latter stage.

In this embodiment, the deceleration lens and the acceleration lens are installed side by side. However, it is also possible to install the two lenses separated from each other. However, in that case, the convergence of ions may be deteriorated, and there is a concern that the resolution of the mass spectrum may be reduced, which is not always preferable.

Although the present embodiment deals with the reflectron type OA-TOFMS, the scope of the present invention is not limited to the reflectron type OA-TOFMS, but is applied to the linear type OA-TOFMS. And OA-T
It goes without saying that the present invention can be applied to TOFMS other than OFMS.

[0028]

As described above, the TOFMS of the present invention
According to the method described above, after the flight speed of ions is once decelerated by the deceleration lens and then accelerated to the original speed by the acceleration lens, the effective flight distance of ions increases, and the mass spectrum of the TOFMS can be increased without increasing the size of the TOFMS device. Resolution can be improved.

[Brief description of the drawings]

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

FIG. 2 is a view showing one embodiment of a vertical acceleration time-of-flight mass spectrometer according to the present invention.

FIG. 3 is a diagram showing an embodiment of a potential arrangement on an ion flight trajectory of the vertical acceleration time-of-flight mass spectrometer according to the present invention.

[Explanation of symbols]

1 ... Ion source, 2 ... Ion guide, 3 ... Intermediate chamber, 4 ...
..Condenser lens, 5 ... Extrusion electrode, 6 ... Acceleration lens,
7 ... reflectron, 8 ... ion detector, 9 ... measurement room, 10 ... orifice, 11 ... deceleration lens, 12 ...
Acceleration lens.

Claims (1)

[Claims] A time-of-flight type wherein a decelerating electric field and then an accelerating electric field are provided on an orbit where ions fly, so that the ions decelerate and then accelerate without changing the flight direction of the ions. Mass spectrometer.