JPS5812983B2 - sekisouchi - Google Patents

Description

[Detailed description of the invention] The present invention relates to a mass spectrometer.

One of the methods for analyzing extremely small amounts (ppm-ppb order) of impurities contained in atmospheric pressure (a pressure of several Torr to several atmospheres) is to analyze a gas using corona discharge or radioisotope at atmospheric pressure. A method is used in which molecules such as organic substances with low ionization potential are selectively ionized and analyzed using a mass spectrometer by ionizing them and efficiently performing ion-molecule reactions under this pressure.

Hereinafter, for the purpose of simplifying the explanation, analysis of impurities contained in Tituso gas at 1 atm will be explained as an example.

The analyzer consists of an ionization chamber 2, an ion-molecule reaction section 3, and mass spectrometers 6 and 7, as shown in FIG.

The titanium gas containing trace impurities enters the ionization chamber through the sample introduction port 1.

Nisso ions ionized in the ionization chamber 2 by corona discharge or radioisotope by the needle electrode 5 cause an ionic molecular reaction with water contained in the nitrogen at several ppm to generate H20+ ions.

This H20+ further gives H+ to organic substances with low ionization potential contained in trace amounts and ionizes them.

The ions thus generated are introduced into the mass spectrometers 6 and 7 through the pinhole 4 by differential pumping and are separated and analyzed.

This method has the characteristic that even I)I)b order organic substances contained in Chituso gas can be easily detected.

In the conventional device, after sufficient ion-molecule reaction is carried out in 1 atm, 10 μm diameter is immediately released from any pinball.
-'Torr analyzer, or once the pressure is reduced to 10-3 to 10-' Torr, then 10
A method was used in which ions were drawn into the -5 to 10-6 Torr ion analyzer.

In this method, the pressure in the region where the ion-molecule reaction occurs is high (1 atm), so ions originating from organic substances with a low ionization potential, which are the final products of the ion-molecule reaction, are stably generated, but the ionization potential is relatively high. The problem was that it was difficult to detect ions caused by organic matter.

The mass spectrum obtained here consists of ions having a mass of (M+1) and M, where the mass of the organic substance is M, and ions of decomposition products of the substance.

When analyzing trace impurities contained in the atmosphere or Tituso gas, if there is only one type of impurity, it is easy to analyze, but if there are many types, it is difficult to determine whether the obtained ion is the parent ion or whether it is a decomposition product. In many cases, it was difficult to distinguish between the two, and it was difficult to determine the spectral attribution.

The purpose of the present invention is to overcome this difficulty and provide a mass spectrometer that can observe even objects with a high ionization potential and that can observe spectra with various reaction times of ion-molecule reactions to facilitate determination of spectrum attribution. It is something to do.

In order to achieve the above object, the present invention creates a pressure between the ionization chamber and the mass spectrometer that can sufficiently change the ion-molecule reaction rate by changing the length or the strength of the electric field applied there. The ion and molecule reaction area is provided.

When passing through this region, ions cause an ion-molecule reaction and enter the ion-molecule reaction region, but by changing the electric field applied to this region or changing its length, the reaction time of the ion-molecule reaction can be changed. can be controlled.

Furthermore, when controlling the reaction time by changing the strength of the electric field, it is possible to change the voltage applied to this region stepwise, sample the ions that reacted at each reaction time, and record them simultaneously with a multi-pen recorder. I'm trying to make it possible.

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

For simplicity, analysis of impurities in nitrogen will be explained as an example.

FIG. 2 shows an ionization mass spectrometer according to the invention.

In the figure, 2 is an ionization section under atmospheric pressure, for example, where N2+ ions and N+ ions are mainly generated.

Some ionic-molecule reactions also occur here.

Ions that have passed through the pores 4 enter an ion-molecule reaction region at a pressure of, for example, several Torr.

The length of the ion molecule reaction region 3 can be changed as necessary using, for example, a bellows 21 for varying the region.

A suitable potential gradient is applied between electrodes 9 and 8 to cause ions to drift toward electrode 8.

The drift time changes depending on the electric field strength or the length of the ion-molecule reaction region.

When changing the length of the ion molecule reaction region 3, the sample gas inlet 1, the corona discharge needle electrode 5, and the porous electrode 9 are moved together by the variable region bellows 21 and the like.

If the drift time is short, N2+4 on is observed, but if the drift time is increased to cause an ion-molecule reaction, N2+4 is observed.
Impurities with low ionization potential (0
, , CO2, NO, and organic substances) are ionized and observed.

When some impurities coexist, the mass spectrum changes depending on the drift time.

When the drift time is short, ions of substances with relatively high ionization potential and decomposition products are observed.

When the drift time is increased to advance the ion-molecule reaction, these ions decrease and ions with low ionization potential and Clask ions become predominant.

By investigating the various stages of ion-molecule reactions in this way, we can obtain a great deal of information about the impurities contained in Tituso gas.

Note that the pressure in the ion-molecule reaction region is particularly limited to o. i
˜number+Torr is preferable.

To measure ion spectra with different reaction times, it is necessary to change the length of the ion molecule reaction region or change the applied potential gradient. In systems that change over time, even if ion spectra with different reaction times are measured,
Comparisons become meaningless.

In such cases, it would be very convenient if spectra at various stages of ion-molecule reactions could be simultaneously recorded and compared.

For this purpose, a method of changing the potential gradient is effective.

FIG. 3 shows an embodiment made to make these things possible.

The voltage applied to the electrode 9 is changed stepwise so that ions at various ion-molecule reaction stages enter the mass spectrometer in sequence.

A plurality of sampling gates 11 are provided in the detection section,
Ion signals are selected and sampled according to each reaction stage and recorded on a multi-pen recorder 13.

The output of the reference repetition pulse generator 15 is inputted to the sampling gate 11, and the output of the sampling pulse circuit 14 which generates sampling pulses is inputted to the sampling gate 11.

Further, the reference repetitive pulse generator 1 is installed on the electrode 9 with pores.
5 is input, and the output of a stepped pulse generator 16 that generates stepped pulses is applied.

FIG. 4 shows the pulses applied to the porous electrode 9 and the pulses applied to the sampling gate 11.

The repetition period (T) of the sampling pulse is 2 (1
-100 msec.

When measuring three reaction stages, the sampling pulse width was set to (T/3-1) msec.

A sampling pulse is generated by delaying the pulse applied to the electrode 9 by 1 msec to reduce errors in ion signal measurement due to delay in response of the amplifier.

(When detecting ions by pulse measurement, etc., there is no need to delay.

) FIG. 5 (This is an example using the ionizing radio intosoap 20.)

This embodiment can also be applied to conventional chemical ionization, and ions at various reaction stages can be measured.

As explained above, according to the present invention, spectra at various stages of ion-molecule reactions can be measured, resulting in a much larger amount of information compared to conventional devices.

As a result, analysis of impurities in gas has become much easier.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a conventional ionization mass spectrometer, in which ions are introduced directly from atmospheric pressure into a pressure section of 10-5 Torr. FIG. 2 is a diagram showing a mass spectrometer according to the present invention, in which there is a zero point between the ionization section and the mass spectrometry section. I Torr ~ Number + To
It has an ion-molecule reaction region with a pressure of rr. FIG. 3 is a diagram showing a pulse circuit and a detection circuit for measuring ion spectra at various ion-molecule reaction stages by varying the voltage applied to the ion-molecule reaction section of the present invention, and FIG. 4 shows the pulse applied to the electrode 9. FIG. 3 is a diagram showing an example of a sampling pulse. FIG. 5 is an example diagram in which a radioisotope such as N I6 3 is used as the ionization method. In the figure, 1: sample gas inlet, 2: ionization section, 3
; ion molecule reaction section, 4; pore for differential pumping, 5: needle electrode for corona discharge, 6; quadrupole column, 7; secondary voltage multiplier, 8
; Electrode with pores, 9; Electrode with pores, 10; Buffer amplifier, 11; Sample and hold circuit, 12; Buffer amplifier, 13; Multi-pen recorder, 14; Sampling pulse circuit, 15; Reference repeated pulse generation vessel, 1
6; Stepped pulse generator, 17: Stepped pulse, 18;
Sampling pulse, 19; Sampling time, 20;
Radioisotope, 21; bellows for changing reaction area.

Claims (1)

[Scope of Claims] 1. In a mass spectrometer having at least an ionization section and a mass spectrometry section, an ion molecule reaction region is provided between the ionization section and the mass spectrometry section, and the ion molecule reaction region A mass spectrometer with pressure that can change the reaction rate of molecules. 2. The mass spectrometer according to claim 1, wherein the boundary of the ion molecule reaction region is constituted by two electrodes with pores installed between the ionization section and the mass spectrometry section, and A mass spectrometer equipped with means for changing the strength of the electric field between two electrodes. 3. The mass spectrometer according to claim 1, wherein the boundary of the ion-molecule reaction region is constituted by two electrodes with pores installed between the ionization section and the mass spectrometry section, and A mass spectrometer comprising means for changing the distance between the two electrodes. 4. The mass spectrometer according to claim 2, including means for changing the electric field strength stepwise, and sampling a spectrum corresponding to each electric field strength output from the mass spectrometer. and means for recording said sampled output.