JPH06150878A - Chemical ionization apparatus - Google Patents

Abstract

PURPOSE:To surely reproduce the condition of an ion source box and give excellent reproduction of mass spectrometry. CONSTITUTION:A monitor electrode 20 is installed in a thermoelectron radiating hole 13 in an ion source box 11. An electrometer 21 to detect the potential is also installed. A part of thermoelectrons comes into collision directly with the monitor electrode 20 and give potential to it and since potential is provided also to a reaction gas, which is converted into plasma, the potential of the monitor electrode 20 reflects the ionizing condition of the ion source box 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chemical ionizer used in a mass spectrometer or the like.

[0002]

2. Description of the Related Art An outline of a chemical ionizer is shown in FIGS.
Will be described. Container 11 called an ion source box
A reaction gas such as ammonia is introduced into the inside of the reactor from the reaction gas pipe 14, and the thermoelectrons generated by the filament 12 are irradiated from the thermoelectron irradiation holes 13 to ionize the reaction gas. The sample gas is put into the ionized reaction gas through the sample tube 15 to ionize the sample gas. The ionized sample gas is electrically repelled by the repeller electrode 18 provided on one side wall, and is emitted toward the mass spectrometer from the ion outlet 16 provided on the opposite side wall.

[0003]

Ion source box 11
The state (temperature and pressure) of the reaction gas inside the chamber has a great influence on the mass pattern (mass distribution) of the sample gas. That is, when the temperature or pressure of the reaction gas is different, the way the molecules of the organic sample are cut is different, and the mass pattern of the sample gas emitted from the ion outlet 16 is different. Conventionally, the flow rate of the reaction gas introduced from the reaction gas pipe 14 is only controlled by the opening degree of the valve, and the state of the reaction gas in the ion source box 11 is actually unknown. Therefore, even if the measurement is temporarily stopped, the introduction of the reaction gas is stopped, and the valve is opened again to make the state inside the ion source box 11 the same as before, it is difficult to exactly reproduce the same state as before. Therefore, there was a problem in the reproducibility of mass spectrometry.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a chemical ionization apparatus capable of reliably reproducing the state in the ion source box. Especially.

[0005]

A chemical ionization apparatus according to the present invention made to solve the above-mentioned problems comprises: a) a monitor electrode placed in an ion source box; and b) detecting the potential of the monitor electrode. And means for doing so.

[0006]

[Function] The thermoelectrons generated by the filament enter the ion source box through the thermoelectron irradiation holes, and part of the reaction gas in the ion source box is plasmatized (ionized), but the rest collides with the reaction gas. Instead, it collides with the monitor electrode and gives a negative potential to the monitor electrode. On the other hand, the reactive gas turned into plasma also gives a potential to the monitor electrode. Since the potential applied to the monitor electrode by these reflects the state of ionization in the ion source box, conversely,
By monitoring the potential of the monitor, the state of the reaction gas in the ion source box can be monitored and controlled.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. In the chemical ionization apparatus of this embodiment, as shown in FIG. 1, the thermoelectron irradiation hole 1 inside the ion source box 11 is used.
A monitor electrode 20 is provided at a position opposed to 3.
An electrometer 21 that displays the potential of the monitor electrode 20 is provided outside the ion source box.

Also in the chemical ionization apparatus of this embodiment,
Similar to the conventional apparatus, a reaction gas such as ammonia or isobutane is introduced from the reaction gas pipe 14 provided on the side wall, and the reaction gas is ionized by irradiating thermoelectrons from the thermoelectron irradiation holes 13. Then, the sample gas is put into the ion source box 11 through the sample tube 15, and the sample gas is ionized by the reaction gas ions. The ionized sample gas is emitted from the ion source box 11 by the repeller electrode 18 and sent to the mass spectrometer.

During the ionization of the reaction gas in this way, the operator adjusts the flow rate of the reaction gas supplied from the reaction gas pipe 14 to the ion source box 11 so that the value of the electrometer 21 becomes constant. The electrometer 21 indicates the potential of the monitor electrode 20. The monitor electrode 20 includes thermoelectrons generated by the filament 12 that do not collide with reaction gas molecules (primary electrons), and Electrons emitted from reaction gas molecules (some of which include sample gas molecules) turned into plasma by thermal electrons collide with each other, and these give an electric potential to the monitor electrode 20. Therefore, when the measurement is temporarily stopped to stop the reaction gas and then the introduction of the reaction gas is restarted, or when the measurement is performed under a condition where the ambient temperature changes, the monitor electrode 20 By adjusting the flow rate of the reaction gas so that the electric potential becomes constant, the state inside the ion source box 11 can be kept constant.

The reaction gas flow rate may be automatically controlled using a microcomputer and an electronic control valve.

[0011]

In the chemical ionization apparatus according to the present invention, since the state inside the ion source box can be monitored, the state can be controlled to be constant. Therefore, it is possible to prevent a change in the mass pattern at the time of ionization of the sample, and to improve the reproducibility of mass spectrometry. This improvement in the reproducibility of the ionized state is achieved by interrupting the measurement and stopping the reaction gas, then restarting the introduction of the reaction gas, or when performing measurement under conditions where the ambient temperature changes. It is especially effective in such cases.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a chemical ionization apparatus that is an embodiment of the present invention.

FIG. 2 is a perspective view of a chemical ionization device.

FIG. 3 is a cross-sectional view of a conventional chemical ionization device.

[Explanation of symbols]

11 ... Ion source box 12 ... Filament 13 ... Thermoelectron irradiation hole 14 ... Reaction gas tube 15 ... Sample tube 16 ... Ion outlet 18 ... Repeller electrode 20 ... Monitor electrode 21 ... Electrometer

Claims (1)

[Claims] 1. A chemical ionization apparatus comprising: a) a monitor electrode placed in an ion source box; and b) means for detecting the potential of the monitor electrode.