JPH08102283A - Quadrupole mass filter - Google Patents

Abstract

PURPOSE: To enable the fine adjustment of the error of assembling by providing a voltage generating circuit per each electrode bar in a quadrupole filter, and changing U/V ratio, high frequency and phase or the like per each electrode bar. CONSTITUTION: DC/AC overlap voltage of the direct current component U and the alternating current component V.cos (ωt+θ) is separately applied to electrode bars 11-14, which are respectively connected to each voltage generating circuit 15-18. These voltage generating circuits 15-18 are connected to one quadrupole control unit 19, and the quadrupole control unit 19 gives the separate control signal related with the direct current component intensity U, the alternating current component wave high value V, the frequency ω and the phase θto each voltage generating circuit 15-18. With this quadrupole filter, the fine adjustment, for example, for changing the only phase of the alternating current component 23 to be applied to a second electrode bar B1 in relation to the alternating current component 22 to be applied to a first electrode bar A11 is possible by appropriately changing the parameter to be given to each voltage generating circuit 15-18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quadrupole mass filter provided in a quadrupole mass spectrometer used for analyzing chemicals, foods, environmental substances and the like.

[0002]

2. Description of the Related Art As shown in FIG. 3, a quadrupole mass filter is composed of four electrode rods 11, 12, 13, 14 arranged rotationally symmetrically about the z-axis and parallel to each other. A quadrupole 10 is provided. In the quadrupole 10, two electrode rods 12 and 14 arranged in the x-axis direction form a pair, and y
The two electrode rods 11 and 13 arranged in the axial direction are regarded as another pair, and these two electrode pairs (12, 14), (11, 1
During 3), the superimposed voltage of the DC voltage U and the high frequency voltage V · cos (ω · t) is applied. When various ions are made incident from one end of the z-axis which is the central axis of the quadrupole 10, the ions are generally caused by an oscillating electric field formed by this voltage.
Divergence out of 0. However, DC voltage U and AC voltage V
Is in a predetermined relationship determined by the mass / charge number (m / z) of ions, only ions having that mass / charge number can oscillate stably and be emitted from the other end of the z-axis. it can. Therefore, by disposing an ion detector at the exit of the quadrupole 10 and appropriately setting the applied voltage to the quadrupole 10, it is possible to configure a mass filter that allows only ions of the target mass to pass. it can. Regions of U and V where ions can pass through the quadrupole 10 are substantially triangular as shown in FIG. 4, and m / z = M1, M2, M
Since the stable region moves as shown in the figure as it changes to 3, it is possible to scan the ions passing through the mass filter by changing U and V as shown by the line L.

FIG. 3A shows each electrode rod 11 of the quadrupole 10.
Specific examples of a DC / AC superposed voltage generation circuit for signals # 14 to # 14 are shown below. In this example, the circuit (DC) 3 that generates the DC voltage U
1 and a circuit (H that generates high frequency voltage V · cos (ω · t))
In addition to F) 32, a perturbation voltage application circuit 33 for additionally applying an AC voltage (perturbation voltage) Va of a small amplitude having a frequency different from that of the HF 32 is provided. By applying this perturbation voltage, the effect of improving the resolution of mass spectrometry can be obtained (for details, see Japanese Patent Laid-Open No. 4-218251), but this perturbation voltage application circuit is not essential and is omitted. It is also possible. The circuit of FIG. 3 (a) is simplified and expressed as shown in FIG. 3 (b).

[0004]

It is desirable that the dimensions of the electrode rods 11 to 14 of the quadrupole 10 are exactly the same, and that the positional relationship between them is strictly rotationally symmetric and parallel to each other. Is difficult to make such an assembly. Further, the four electrode rods 11 to 14 are fixed by a pair of ceramic holders.
When the above high frequency (about 1 MHz) is applied to 4, dielectric loss occurs in the ceramic holder and heat is generated. The positional relationship between the electrode rods 11 to 14 also changes when the holder expands or distorts due to this heat.

In such a case, the conventional quadrupole filter mainly adjusts by changing the peak value V of the AC component, but the quadrupole processing error, the assembly error, etc. are not always sufficiently compensated. However, there was a problem that the mass resolution was lowered and the sensitivity was lowered.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a quadrupole filter capable of more freely and sufficiently compensating for assembly errors and the like. To do.

[0007]

SUMMARY OF THE INVENTION The present invention, which has been made to solve the above-mentioned problems, has a structure in which a rotationally symmetric position about a central axis is set to 4
Two electrode rods are arranged parallel to the central axis, and by applying a superimposed voltage of DC voltage and AC voltage between two electrodes facing each other across the central axis and the other two electrodes. A quadrupole mass filter that allows only ions having a predetermined mass to pass is characterized in that a circuit for generating the superimposed voltage is provided for each of the four electrode rods.

[0008]

[Function] Since a voltage generation circuit is provided for each electrode rod, the ratio of the intensity of the DC component to the intensity of the AC component, the frequency of the AC component, the wave height, etc. can be changed for each electrode, A phase difference can be provided. By appropriately changing many of these parameters, the quadrupole can be adjusted in a wider range than in the past, and the assembling error can be finely and optimally compensated. Further, by detecting passing ions while changing these parameters for each electrode rod, it becomes possible to obtain a wider range of knowledge regarding the components and structure of the sample than in the past.

The quadrupole filter according to the present invention is an MS / M having a quadrupole filter in the front and rear stages in addition to a normal quadrupole mass spectrometer having only one quadrupole filter.
It can also be used in an S mass spectrometer.

[0010]

FIG. 1 shows a quadrupole filter which is an embodiment of the present invention. In this quadrupole filter, one voltage generation circuit A to D (15 to 18) is provided for each of the electrode rods 11 to 14 forming the quadrupole 10. Each of the voltage generating circuits 15 to 18 is the same as that provided in the conventional quadrupole filter. For example, in addition to the one provided with the perturbation circuit as shown in FIG. 3A, it may not be provided with the perturbation circuit as described above.

Each of the voltage generating circuits 15 to 18 independently generates a DC / AC superimposed voltage of a DC component U and an AC component V.cos (ω.t + θ) with respect to the electrode rods 11 to 14 respectively connected thereto. Apply. These voltage generation circuits 15-18 are connected to one quadrupole control unit 19, and the quadrupole control unit 19 separates DC component intensity U and AC component wave for each voltage generation circuit 15-18. The control signals for the high value V, the frequency ω and the phase θ are given.

An ion detector 20 is provided at the exit of the quadrupole 10, and its detection signal is transmitted to the data processing section 21. The data processing unit 21 performs processing such as graph creation and ion estimation based on the ion detection signal and the scanning signal from the quadrupole control unit 19.

In the quadrupole filter of this embodiment, the quadrupole control unit 19 appropriately changes the parameters given to the voltage generation circuits 15 to 18, so that, for example, as shown in FIG. Fine adjustment is possible by changing only the phase θ of the AC component 23 applied to the second electrode rod B (12) with respect to the AC component 22 applied to (11).
In the third row of FIG. 2, only the peak value V is shown, and in the fourth row, the AC components 24 and 25 in which only the frequency ω is changed are shown.
A waveform may be formed by appropriately combining these. By appropriately combining these fine adjustments, the electrode rod 11
The correct mass analysis can be performed by compensating for the dimensional error, the assembly error, the dimensional / arrangement change due to the heat generation of the holder, etc. In addition to this, by recording the state of changes in the detected ion intensity when these values are changed and analyzing the data, it becomes possible to obtain new information regarding the components and structure of the sample.

[0014]

In the conventional quadrupole filter, only one voltage generation circuit is used for four electrode rods, but in the quadrupole filter according to the present invention, voltage generation is performed for each electrode rod. Since a circuit is provided, U / V for each electrode rod
You can change the ratio, high frequency, phase, etc.,
It is possible to make finer adjustments than before with respect to assembly errors and the like. Further, by changing these parameters for each electrode rod, various data that cannot be obtained by conventional mass spectrometry can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a quadrupole filter that is an embodiment of the present invention.

FIG. 2 is a graph showing a waveform of an AC component applied to each quadrupole electrode rod of the example.

FIG. 3 is a circuit diagram (a) showing a specific example of a voltage generation circuit of a conventional quadrupole filter, and a schematic configuration diagram (b) simplified thereof.

FIG. 4 is a quadrupole stable region diagram.

[Explanation of symbols]

 10 ... Quadrupole 11, 12, 13, 14 ... Electrode rod 15, 16, 17, 18 ... Voltage generation circuit 19 ... Quadrupole control unit 20 ... Ion detector 21 ... Data processing unit

Claims (1)

[Claims] 1. An electrode comprising four electrode rods arranged parallel to the central axis at rotationally symmetric positions around the central axis, the two electrodes facing each other across the central axis and the other two electrodes. In a quadrupole mass filter that passes only ions having a predetermined mass by applying a superimposed voltage of a DC voltage and an AC voltage between them, a circuit for generating the superimposed voltage is provided for each of the four electrode rods. A quadrupole mass filter characterized in that