JPS5824377Y2 - ion source device - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to an ion source device in a mass spectrometer.

Ionization methods for a sample in mass spectrometry include electron impact ionization (EI) and chemical ionization (CI), and the structure of the ion source device differs depending on the ionization method.

Therefore, with one ion source device, E
An ion source device that can be used as an ion source device for either I or CI is desired.

The present invention provides an ion source device for both EI and CI as described above.

The chemical ionization method (CI) uses a reactive gas to first ionize the reactive gas and then bond it to the sample molecules to ionize the sample molecules.The pressure of the reactive gas in the ionization box is around 1 torr. The pressure is significantly higher than that of the mass spectrometer space outside the ionization box, and the ionization box needs to maintain the inside of the box at around 1 torr compared to the high vacuum outside. It is desirable that the opening be as narrow as possible.

On the other hand, in the case of EI, the pressure difference between the inside and outside of the ionization box is extremely small, so there is no requirement to make the openings of each part particularly narrow.

Conventionally, an ion source device as shown in FIG. 1 has been used to make the two types of ion source devices having the above-mentioned differences compatible.

In the figure, 1 is the ionization box, 2 is the filament of the electron source, 3 is the filament shield electrode, and 4 is the electron incidence hole for the ionization box 1. It has a sliding structure so that the size can be changed, and when used for CI. is the smaller hole 4'
Use.

A trap electrode 5 is inserted into the ionization box 1 with an insulating material 6 interposed between it and the ionization box 1.

When the trap electrode 5 is used for EI, it controls the ionizing electron current by controlling the trap current.

When used for CI, the pressure inside the box 1 is high and electrons cannot reach the trap electrode 5, so control is performed by the electron current flowing into the ionization box 1, and the trap electrode 5 is not necessary. Since it is troublesome to put on and take off, the structure is fixed as shown in the figure.

Reference numeral 7 denotes an ion injection hole, which also has a sliding structure and can be changed in size, and the smaller hole 7' is used for CI.

8 is an ion focusing lens, and 9 is a sample introduction hole.

The structure shown in FIG. 1 has the following problems.

That is, as a result of the introduction of the sample and reaction gas into the ionization box 1, these contaminate the insulator 6 between the trap electrode 5 and the box 1, interfering with mass spectrometry, and also accelerating the deterioration of the insulation and causing ionization. Its lifespan as a source is short.

The present invention aims to solve the above-mentioned problems in the conventional example shown in FIG.

The ion source device of the present invention has a trap electrode that fits into the opening of the ionization box and is movable. When used for EI, the trap electrode is removed from the opening of the ionization box to cut off contact between the two, and when used for CI. When used, the opening of the ionization box is closed with a trap electrode.

The present invention will be explained below with reference to Examples.

FIG. 2 shows an embodiment of the present invention.

Components corresponding to those in FIG. 1 are given the same numbers and their explanations will be omitted.

An outwardly tapered opening 10 is bored at a position facing the electron incidence hole 4 of the ionization box 1, and a trap electrode 5 having a shape that fits this opening is arranged outside the box 1, and the trap electrode 5 is connected to the arrow mark. It can be moved in the direction.

The figure shows a state where the switch has been made for EI, and the trap electrode 5 has retreated and is separated from the ionization box 1. Even without an insulator, the trap electrode 5 is electrically separated from the ionization box 1. voltage can be applied independently to each.

11 is a device for moving the trap electrode 5 forward and backward in the direction of the arrow;
The switch 12 is opened and closed in conjunction with the advance and retreat of the electrode, and the EI
When in use, the switch is closed and the voltage of the power source E is applied to the trap electrode 5.

13 is an ammeter that displays the trap current.

E' is a power supply that provides a potential difference between the filament 2 and the ionization box 1, 14 is an ammeter that indicates the ionization box current, and 15 is a filament power supply. Adjust 15.

When the ionization apparatus shown in FIG. 2 is used for CI, the electron entrance hole is changed to the smaller side 4', and the ion exit hole is changed to the smaller side 7', and the trap electrode 5 is moved forward and fitted into the opening 10.

This closes the opening 10 of the ionization box 1, making it possible to maintain a high pressure inside.

At the same time, the switch 12 is opened and the trap electrode 5 becomes at the same potential as the ionization box 1.

As mentioned above, a trap electrode is not required in the case of CI, so there is no problem in this state.

The current in the filament 2 is adjusted so that the reading on the meter 14 is appropriate.

FIG. 3 shows another embodiment of the present invention, in which a trap electrode 5 is located inside the ionization box 1 and is pulled outward to close the opening 10 when used for CI.

Other parts are the same as in FIG. 2, and corresponding parts are indicated with the same reference numerals.

The embodiment shown in FIG. 4 is further provided with a repeller electrode 16, which moves back and forth in the same way as the trap electrode 5 to close the opening 17 during CI.

The ion source device of the present invention has the above-mentioned configuration and there is no insulating material interposed between the trap electrode and the ionization box, so there is no possibility of contamination by insulating material samples or reaction gases, insulation deterioration, etc. as mentioned at the beginning. No problem, and EI,
When switching the CI, it is also easy to maintain the pressure inside the ionization box in the CI.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing the main points of a conventional ion source device;
3 and 4 are sectional views showing the main points of different embodiments of the present invention, respectively. 1... Ionization box, 2... Filament, 5... Trap electrode, 10... Opening that is closed by the trap electrode.

Claims (1)

[Scope of utility model registration request] It has two types of large and small electron entrance holes and two large and small ion exit holes, and when using it for EI, the larger hole is selected, and the C
In an ionization box in which the electron entrance hole and ion exit hole can be switched so that the smaller hole is selected when used for I, an opening into which the trap electrode looks is provided in the ionization box, and A trap electrode is provided in conjunction with switching between EI and CI so that it can move forward and backward, and is separated from this opening when used for EI, and closed when used for CI, and this trap electrode is connected to a switch. connect to the trap electrode power supply through the
An ion source device that is linked to switching between