JPH0624115B2 - Double focusing mass spectrometer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a double-focusing mass spectrometer having an ion source and a collision activation chamber and having a daughter ion detection function.

[Conventional technology]

FIG. 4 shows the structure of a double-focusing mass spectrometer having a daughter ion detection function. In the double-focusing mass spectrometer shown in FIG. 4, the ions generated by the ion source 31 and accelerated to the kinetic energy E ₀ are incident on the collision activation chamber 32. Gas molecules are introduced into the collision activation chamber 32,
Ions are activated by colliding with gas molecules. Some of the activated ions are cleaved in the first field, for example, a free space up to an electric field in FIG. 4, that is, a space without an electromagnetic field to generate daughter ions. This daughter ion has a different mass and energy than the original ion (parent ion). In order to detect the daughter ions thus generated, it is necessary to satisfy a certain relationship between the ion acceleration voltage V _a , the electric field strength E, and the magnetic field strength B. These values (V _a , E, B)
A method of sweeping while satisfying a certain relationship between is known as a link sweep method.

[Problems to be solved by the invention]

By the way, in FIG. 4, if the mass of the daughter ion generated in free space is m and the energy is E _m , this ion can pass through each field of the double-focusing mass spectrometer in order to detect this daughter ion. You can set it to a value. In this way, the double focusing condition is satisfied, so that the daughter ions form a sharp image on the collector slit 36.

However, strictly speaking, there is a problem that the daughter ions do not form a sharp image on the collector slit 36. The reason is,
This is because a slight shift occurs between the parent ion's orbit and the daughter ion's orbit when the ion is cleaved, and the daughter ion's orbit deviates from the original orbit that should satisfy the double focusing condition.

In other words, in the conventional device, as shown in FIG. 5, since the cleavage of the parent ion into the daughter ion occurs in the free space between the source slit 33 and the first field, here the electric field 34, the orbit of the daughter ion is generated. Shift, the image is spread on the collector slit 36, and as a result, the mass resolution of the daughter ions is limited.

The present invention solves the above problems, and an object of the present invention is to provide a double-focusing mass spectrometer capable of eliminating the deviation of the daughter ion trajectories and improving the mass resolution.

[Means for solving problems]

Therefore, the double-focusing mass spectrometer of the present invention is a double-focusing mass spectrometer having an ion source and a collision activation chamber, and a parent ion and a daughter ion are provided between the collision activation chamber and the source slit. It is characterized in that a filter for separation is arranged according to the difference in physical characteristics, and the filter and the double focusing mass spectrometer are interlocked and controlled so that the same daughter ion can pass through.

[Action]

In the double-focusing mass spectrometer of the present invention, a filter for separating parent ions and daughter ions according to their physical characteristics such as energy and momentum is arranged between the collision activation chamber and the source slit, and Since the filter and the double-focusing mass spectrometer are interlocked with each other so that the same daughter ions can pass therethrough, the orbital deviation of the daughter ions is eliminated. That is, if all the cleavages occur between the collision activation chamber 32 and the source slit 33 and do not occur between the source slit 32 and the first field, the orbits of the daughter ions satisfy the original double focusing condition. There is no deviation from the filled orbit, and the daughter ions form a sharp image. The double-focusing mass spectrometer of the present invention is based on this principle.

〔Example〕

 Hereinafter, embodiments will be described with reference to the drawings.

FIG. 1 is a diagram showing the configuration of one embodiment of a double-focusing mass spectrometer according to the present invention, and FIG. 2 is a view for explaining another embodiment of the double-focusing mass spectrometer according to the present invention. .

The double-focusing mass spectrometer according to the present invention is to provide a filter electric field between the collision activation chamber 2 and the source slit 6 so as to pass only ions having a specific energy as shown in FIG.

The operation will be described next. First, the mass of the parent ion is M
_0, the energy E _0, a daughter ion mass m, the energy E _m. Here, when detecting daughter ions, the filter electric field 3 and the electric field 7 of the double-focusing mass spectrometer are set so that ions of energy E _m can pass through. The magnetic field 8 is also set so that the daughter ions can pass through.

In the double-focusing mass spectrometer with each field set in this way, when the ions generated and accelerated by the ion source 1 enter the collision activation chamber 2 and collide with gas molecules to be activated,
Some of the activated ions cleave and generate daughter ions in the free space A between the collision activation chamber 2 and the filter electric field 3. The daughter ions pass through the filter electric field 3, the source slit 6, the free space B, the electric field 7 and the magnetic field 8 of the double-focusing mass spectrometer along the trajectory 5 of the daughter ion, and form an image on the collector slit 9. On the other hand, the parent ion that has passed through the free space A cannot pass through the filter electric field 3 as shown by the trajectory 4 of the parent ion, and does not reach the free space B of the double focusing mass spectrometer. Therefore, since the daughter ions are not generated in the free space B, the deviation of the orbits of the daughter ions as generated by the conventional method is eliminated. Therefore, a sharp image of the daughter ions can be obtained on the collector slit 9 in the apparatus according to the present invention.

As is clear from this operating principle, the filter electric fields 3 and 2
The electric field 7 of the double-focusing mass spectrometer needs to be linked so as to pass ions having the same energy.

By the way, in general, the energy of daughter ions is distributed over a certain width during cleavage. Therefore, in the case of the configuration shown in FIG. 1, the daughter ion beam spatially spreads on the source slit 6 due to the energy dispersion action of the filter electric field 3. Therefore, when the source slit 6 is thin, only some of the generated daughter ions can pass through the source slit 6. On the other hand, the purpose of the filter electric field 3 is to separate parent ions and daughter ions, so that the energy resolution does not need to be so high. In view of such a situation, the example in which the filter electromagnetic field is of the energy focusing type is shown in FIG. It is the one.

The operation principle of the configuration shown in FIG. 2 will be described. The filter electric field 13 separates a parent ion and a daughter ion by its energy dispersion action. The intermediate slit 16 does not allow parent ions to pass therethrough, but almost allows the spread daughter ion beam to pass therethrough. In order to set in this way, it is necessary that the energy difference ΔE = | E _o −E _m | between the daughter ion and the parent ion is sufficiently larger than the energy spread δE of the daughter ion, and this condition is usually satisfied. Has been done. On the other hand, the filter electric field 17 has an energy dispersion action in the opposite direction to the filter electric field 13, and the source slit 1
8 above, the dispersions of the two cancel each other out so that the energy is converged. By doing this, the source slit 1 can be used even for a daughter ion beam with a wide energy range.
No longer spread on 8.

FIG. 3 shows an MS in which the present invention is applied to a double convergence analyzer in the latter stage.
It is a figure which shows the example of a / MS mass spectrometer. In this case, the portion of the ion source in FIG. 1 or 2 is replaced with the mass spectrometer 21 (MS1). That is, the mass separation meter 21 may be considered as an ion source that generates only ions of a specific mass.

The present invention is not limited to the above embodiment, and various modifications can be made. For example, in the above-mentioned embodiment, the double convergence analyzer is a combination of EB (electric field, magnetic field), but the invention is not limited to this and various combinations of double convergence may be used. However, in any case, it is needless to say that the filter electric field needs to be operated so as to pass ions of the same energy as the double focusing mass spectrometer. Also, the method of activating the parent ion is not limited to collision, but there is also a method such as laser irradiation. Therefore, the collision activation chamber in the configuration of the present invention can be replaced with an activation method device by another method. The collision activation chamber may be used at a potential other than the ground potential for various purposes, and even in this case, the present invention can be applied when the energy of the parent ion and the energy of the daughter ion are different.

If the purpose of the filter electric field is to separate parent and daughter ions, other fields (eg magnetic fields) can be used to achieve the same purpose. When a magnetic field is used, since the magnetic field has a momentum dispersion action, it can be separated by the difference in momentum between the parent ion and the daughter ion. Further, the momentum dispersion can be canceled on the source slit in the same manner as in FIG.

In principle, other general fan-shaped fields (superposed electric and magnetic fields) are also possible. In this case, the separation of the parent ion and the daughter ion is performed by a general amount of dispersion including energy and momentum. Of course, a combination that cancels the dispersion on the source slit is also possible. Whichever field is used, the filter and the double-focusing mass spectrometer must be controlled so that the same daughter ions can pass through. As described above, although there are various possibilities for the filter, a field including a magnetic field is generally difficult to control and requires a large device, so that a filter using an electric field is practically the most suitable.

〔The invention's effect〕

As is apparent from the above description, according to the present invention, a filter is provided between the collision activation chamber and the source slit, which allows only ions satisfying a certain condition to pass, and prevents parent ions from passing when detecting daughter ions. Therefore, the cleavage from the parent ion to the daughter ion does not occur in the free space of the double-focusing mass spectrometer. Therefore, the orbits of the daughter ions do not deviate from the original orbits, and the mass resolution of the daughter ions can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of a double-convergence mass spectrometer according to the present invention, and FIG. 2 is a diagram for explaining another embodiment of the double-convergence mass spectrometer according to the present invention. FIG. 3 is a diagram showing an example of an MS / MS mass spectrometer in which the present invention is applied to a double focusing spectrometer in the latter stage, and FIG. 4 is a diagram showing a configuration of a double focusing mass spectrometer having a daughter ion detection function. , FIG. 5 is a diagram for explaining a case where the orbit of the daughter ions is deviated. 1 ... Ion source, 2 ... Collision activation chamber, 3 ... Filter electric field, 4 ... Parent ion orbit, 5 ... Daughter ion orbit, 6
...... Source slit, 7 ... electric field, 8 ... magnetic field, 9 ...
Collector slit.

Claims (2)

[Claims] 1. A double focusing mass spectrometer having an ion source and a collision activation chamber, wherein a parent ion and a daughter ion are separated between a collision activation chamber and a source slit by the difference in their physical characteristics. A double-focusing mass spectrometer characterized in that a filter for observing the same is arranged, and the filter and the double-focusing mass spectrometer are interlocked and controlled so that the same daughter ions can pass through. 2. The double-focusing mass spectrometer according to claim 1, wherein the filter is arranged to cancel the dispersion of the daughter ions on the source slit.