JPH04106858A - Quadrupole mass spectrometer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a four-electrode mass spectrometer, and more particularly to a quadrupole mass spectrometer in which deterioration of the detector is prevented.

<Prior Art> A high frequency inductively coupled plasma mass spectrometer is widely known as an analysis device using a quadrupole mass spectrometer. This high-frequency inductively coupled glasma mass spectrometer excites a sample using high-frequency inductively coupled plasma, guides the generated ions to a mass spectrometer through an interface consisting of a nozzle and a skimmer, and electrically detects the ions to measure the amount of ions. It is configured to analyze elements to be measured in a sample with high precision by making precise measurements.

FIG. 5 is an explanatory diagram of the configuration of a conventional example of such a high frequency inductively coupled plasma mass spectrometer. In this figure, argon gas is supplied from an argon gas supply source 3 to the outer tube 1b and the outermost tube IC of the plasma torch 1 via the gas regulator 2, and the sample in the sample tank 4 is supplied to the inner tube 1a through a nebulizer. After being atomized in step 5, it is carried in using argon gas. Further, a high frequency current is passed through a high frequency induction coil 6 wound around the plasma torch 1 by a high frequency power source 10, and a high frequency magnetic field (not shown) is formed around the coil 6. On the other hand, the pressure inside the forechamber 11 sandwiched between the nozzle 8 and the skimmer 9 is reduced to, for example, ITorr by a vacuum pump 12. Also, in the center chamber 13, ion lens systems 14a, 1
4b is provided, and the interior of the center chamber 13 is heated by the first oil diffusion pump 15, for example, at 10-'T.
The pressure inside the rear chamber 17 housing the quadruple post-mass filter 16 is reduced to, for example, 10-'Torr by the second oil diffusion pump 18.

When electrons or ions are planted in the argon gas in the vicinity of the high frequency magnetic field in this state, high frequency inductively coupled plasma 7 is instantaneously generated by the action of the high frequency magnetic field. Ions in the plasma 7 pass through a nozzle 8 and a skimmer 9, and then are focused through ion lens systems 14a and 14b. Here, the ion lens systems 14a and 14b are double quadrupole lenses that block light from the high-frequency inductively coupled plasma 7 and allow only ions to pass through, and the ions that have passed through the ion lens system are mass filter 16
is guided to the secondary electron multiplier tube 19 and detected, and the detection signal is sent to the signal processing section 20 where it is calculated and processed, thereby obtaining the analysis value of the element to be measured in the sample. ing.

By the way, the quadruple post mass filter 16 has two
It is composed of M quadruple rear rods, and one set of opposing rods is applied with an AC voltage with a phase difference of 180 degrees, and the other set of opposing rods is applied with a DC voltage with a different polarity. It has become. In addition, while maintaining a certain ratio of the DC voltage and AC voltage applied to each rod in this way, the DC voltage (LJ
) and alternating current voltage (V) to obtain a mass spectrum.

FIG. 5 is a diagram showing a typical stable region obtained in this way. In the figure, the vertical axis represents the DC voltage (U) applied to the quadruple rear rod, and the horizontal axis represents the DC voltage (U) applied to the quadruple rear rod. It shows the applied alternating current voltage (V).

Moreover, when the value of the DC applied voltage U and the value of the AC applied voltage V are inside the stability region M1 indicated by the approximate triangle 0AuV in FIG. is now reachable.

On the other hand, if there are stable regions M and ~M5 as shown in Fig. 6, the DC applied voltage U and By changing the DC applied voltage U and the AC applied voltage V applied to the quadruple post rod while keeping the ratio of the AC applied voltage V constant, mass spectra m, to m5 as shown in FIG. 7 are obtained. Further, a line m connecting the vertices A, to A5 of the substantially triangular shapes forming these stable regions M1 to M5 is called a scan line.

<Problem to be solved by the invention> However, in FIG. 6, the vertices A2 to A4 of the stable region
When trying to obtain the mass spectra m1 and mass spectrum m5 in Fig. 7 by jumping, the stable region M2 in Fig. 6
In the transient state where M4 is jumped, the ratio of the DC applied voltage U to the AC applied voltage V is not constant, so everything on the scan line in the stable region (the region indicated by the approximate triangle 0AIV1 in FIG. 4) ions reach the detector,
As a result, there was a drawback that the detector deteriorated.

The present invention was made in view of the drawbacks of the conventional example, and its purpose is to provide a quadruple post-mass spectrometer that can prevent deterioration of the detector even when the mass axis is jumped. There is a particular thing.

Means for Solving the Problems> The features of the present invention that solve the above problems are that in a quadruple post mass spectrometer, a central processing unit, a D/A converter for setting the mass axis, first and second delay circuits;
A DC voltage drive circuit that receives the output of the delay circuit and applies a DC voltage to the rod, and an AC voltage drive circuit that receives the output of the second delay circuit and applies an AC voltage to the rod, and has a small mass. When making a jump from a large mass number to a large mass number, the DC voltage drive circuit is activated immediately via the first delay circuit, and when making a jump from a large mass number to a small mass number, the DC voltage drive circuit is activated via the second delay circuit. The object of the present invention is to quickly operate the AC voltage drive circuit.

<Example> Hereinafter, the present invention will be described in detail using the drawings. 1st
The figure is an explanatory view showing the main parts of the embodiment of the present invention, and in the figure, 21 is a central processing unit (hereinafter referred to as rCPU);
2 is a D/A converter for setting the mass axis; 23a and 23b are first and second delay circuits; 24 is a DC voltage drive circuit; 25
2 is a time chart for explaining the operation of the embodiment of the present invention, and in the figure, (a) is the output voltage of the D/A converter 22 of FIG. 1. (b) indicates the output voltage V of the first delay circuit 23a,
(c) shows the output voltage V of the second delay circuit 23b.

In a solid line example of the present invention having such a main part configuration,
The output of the CPLI 21 is sent to the mass axis setting D/A converter 22 and converted into an analog signal as shown in FIG. 2(A). This analog signal is sent to the first and second delay circuits 23a and 23b, and is shown in (b) and (c) in FIG.
Each signal is converted into an analog signal as shown in the figure below.

That is, at the time t1 for jumping from the stable region M in FIG. 6 to the stable region M5, the rise of the output voltage in FIG. The applied DC voltage U changes rapidly. For this reason, the scan line does not become the straight line m in FIG. 6, but instead becomes a scan line directed upward along the curve m-.

Also, the time 1 for jumping from mass spectrum M5 to mass spectrum M in FIG. In this case, since the output voltage in FIG. 2 (b) falls quickly, the AC applied voltage drive port 111g25 operates quickly, and the AC voltage (2) applied to the rod changes quickly. Therefore, the scan line does not become the straight line m in FIG. 6, but instead becomes a scan line directed downward along the curve IRm-.

By doing this, the stable region M in FIG.
In the case where stability region m and mass spectrum m5 in FIG. 7 are obtained by jumping from 2 to M4, in the transient state where stability regions M2 to M4 are jumped, ions of any mass number are not stable. Area (approximate triangle 0AT in Figure 5)
The scan line does not pass through the region indicated by LVTL). Therefore, unnecessary ions do not pass through the quadruple diameter mass filter, and deterioration of the detector as in the conventional example can be avoided.

It should be noted that the present invention is not limited to the embodiment whose main parts are shown in FIG. A DC voltage setting D/A converter 26 is installed between the voltage drive circuit 24.
At the same time, a D/A converter 27 for DC voltage setting is provided between the CPU 21 and the DC voltage drive circuit 24, and when jumping from a small mass to a large mass, a D/A converter 27 for setting the DC voltage is provided between the CPU 21 and the DC voltage drive circuit 24.
/A converter 26 is set first, and in the opposite case, D/A converter 27 for AC voltage setting is set first. According to such a modified embodiment, the scan line corresponds to the chain double-dashed line m in FIG.
"become that way.

<Effects of the Invention> The present invention as described in detail above provides a four-diameter mass spectrometer that includes a central processing unit, a D/A converter for mass axis setting, first and second delay circuits, A DC voltage drive circuit that receives an output from the first delay circuit and applies a DC voltage to the rod, and an AC voltage drive circuit that receives an output from the second delay circuit and applies an AC voltage to the rod. ,
When jumping from a small mass number to a large mass number, the DC voltage drive circuit is activated immediately via the first delay circuit, and when jumping from a large mass number to a small mass number, the second delay circuit is activated. The AC voltage drive circuit is configured to be activated quickly through the AC voltage drive circuit.

Therefore, a picture electrode mass spectrometer is realized in which deterioration of the detector can be prevented even when the mass axis is jumped.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of the main part of an embodiment of the present invention, Fig. 2 is a time chart, Fig. 3 is an explanatory diagram of the main part of another embodiment of the invention, and Fig. 4 is high-frequency inductively coupled plasma mass spectrometry. FIG. 5 and FIG. 6 are mass spectrum composition curve diagrams, and FIG. 7 is a diagram showing the mass spectrum. 1...Plasma torch, 3...Argon gas supply source, 4...Sample tank, nebulizer, 7...High frequency inductively coupled plasma, 8...・・・
・Nozzle, 9... Clearance ~ 16... Picture electrode mass filter, 19... Secondary electron multiplier,
20...Signal processing unit 21...Central processing unit, 22...D/A converter for mass axis setting, Fig. 1, Fig. 2, 3a, 23b... Delay circuit, 4...DC voltage drive circuit, 5...-...AC voltage drive circuit

Claims (1)

[Claims] In a quadrupole mass spectrometer that applies an alternating current voltage with a phase difference of 180 degrees and a direct current voltage with a different polarity to each of two sets of quadrupole rods constituting a quadrupole mass filter,
a central processing unit, a D/A converter for mass axis setting, and a first
and a second delay circuit; a DC voltage drive circuit that receives the output of the first delay circuit and applies a DC voltage to the rod; and a DC voltage drive circuit that receives the output of the second delay circuit and applies an AC voltage to the rod. and an AC voltage drive circuit, and when jumping from a small mass number to a large mass number, the DC voltage drive circuit is immediately activated via the first delay circuit, and at the same time, the jump is made from a large mass number to a small mass number. A quadrupole mass spectrometer, characterized in that when making a jump, the AC voltage drive circuit is immediately activated via the second delay circuit.