JPH02148649A - High frequency inductive coupling plasma mass spectrometer - Google Patents

Abstract

PURPOSE:To change the waiting time according to the change of unstable time of a circuit and eliminate the wasteful waiting time by calculating the optimum value of waiting time from the combination of a determined mass number and a mass number set by a programmable timer, and setting said value in the programmable timer. CONSTITUTION:A pulse signal as (a) is sent from a CPU 21 to a programmable timer 23 for waiting time, where the waiting time is set. When a signal as (b) is sent from the CPU 21 to a D/A converter 22 to set a mass axis in the D/A converter 22, the programmable timer 23 preliminarily set to the optimum waiting time starts to operate. When a waiting time Tw shown in (c) is passed and the operation of the programmable timer 23 is terminated, a counter gate signal as shown in (d) is sent to a pulse counting counter 25 to open the gate. Hence, the waiting time is changed according to the change of unstable time of the circuit, and a wasteful waiting time can be eliminated.

Description

[Detailed Description of the Invention] <Field of Application of Industry-F> The present invention is based on high frequency inductively coupled plasma! Regarding analyzers, especially quality! This invention relates to a high frequency inductively coupled plasma mass spectrometer with improved timing for setting one axis.

<Prior art> A high-frequency inductively coupled plasma mass spectrometer uses high-frequency inductively coupled plasma to excite a sample, guide the generated ions to a mass spectrometer through an interface consisting of a nozzle and a skimmer, and electrically detect them. By precisely measuring the amount of ions, the element to be measured in the sample is analyzed with high precision. FIG. 3 is an explanatory diagram of the configuration of a conventional example of such a high frequency inductively coupled glasma mass spectrometer.

In this figure, argon gas is supplied to the outer chamber 1b and the outermost chamber IC of the plasma torch 1 from the argon gas supply source 3 via the gas regulator 2, and the inner chamber 1a is supplied with sample 4fI4.
The sample inside is atomized by a nebulizer 5 and then transported by an argon gas. Furthermore, 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 forechamber main body 11 sandwiched between the nozzle 8 and the skimmer 9
Inside, for example, 1'T' or
r, is attracted to. Furthermore, ion lenses 14a and 14b are provided in the center chamber 13, and the inside of the center chamber 13 is sucked to, for example, 10-' Torr by the first oil diffusion pump 15, and a mass filter (for example, a quadrupole mass The second oil diffusion pump 1 is located inside the rear chamber 17 that houses the filter) 16.
8, for example, to 10-"f"orr.

When electrons or ions are implanted in the argon gas in the vicinity of the high frequency magnetic field in this state, high frequency induced plasma 7 is instantaneously generated by the action of the high frequency magnetic field. The ions in the plasma 7 pass through the nozzle 8 and the skimmer 9, pass between the ion lenses 14a and 14b (or doublet quadrupole lens), are focused, and then pass through the mass filter 16 to increase secondary electrons. The detection signal is guided to a multiplier tube 19 and detected, and the detection signal is sent to a signal processing section 20 where it is calculated and processed, thereby obtaining an analysis value of the element to be measured in the sample.

On the other hand, so-called mass axis setting, in which the position of the axis of the mass filter 16 is determined and set, is performed using a digital circuit using a computer and a D/A converter. In addition, when detecting ions using the pulse counting method, the mass spectrometer drive circuit is unstable immediately after setting the mass axis, so wait for a certain period of time after setting the mass axis, then open the counter gate and start counting. has started.

<Problems to be Solved by the Invention> However, in the above conventional example, when setting discrete masses for different mass numbers on the mass axis, the instability time is determined by the magnitude of the difference between a predetermined mass and the next mass. Since the waiting time is fixed, although it varies by , we must wait for all masses for the maximum expected instability time.

For this reason, there is a problem in that depending on the combination of masses to be measured, time is wasted, resulting in a longer measurement time. That is, mutually different mass numbers M+,
When setting the mass axis for discrete masses as shown in Figure 4 for M2 and MCI, the actual mass axis setting (i.e., the actual mass axis setting for the mass filter of the high frequency inductively coupled plasma mass spectrometer) is as shown in Figure 5. However, as shown in Fig. 6, the waiting time Tw is fixed (the integral time 'rl is also fixed).
Therefore, the pulse counting counter gate has a waiting time ′ which is the maximum expected unstable time.
It is necessary to wait for all the masses during rw, but for the mass numbers M, , M3, a shorter waiting time should be sufficient.

The present invention has been made in view of the problems of the conventional example, and its object is to provide a high-frequency inductively coupled plasma mass that changes the waiting time in accordance with changes in the unstable time of the circuit and eliminates unnecessary waiting time. Our goal is to provide analyzers.

Means for Solving the Problems> The present invention provides a high-frequency inductively coupled plasma mass spectrometer in which the waiting time is set to a different value each time the mass axes of the microcomputer, D/A converter, and mass filter are set. A programmable timer for a waiting time to be set, a drive power source for driving a high frequency inductively coupled plasma mass spectrometer, and a counter for a pulse counter are provided, and a set of a predetermined mass number and a mass number set by the programmable timer is provided. The above-mentioned problem is solved by calculating the optimum value of the waiting time from the matching and setting it in the programmable timer.

<Example> Hereinafter, the present invention will be described in detail using the drawings. 1st
The figure is an explanatory diagram of the main part configuration of the embodiment of the present invention, and in the figure, 21
is, for example, a central processing unit of a microcomputer, 22 is a D/A converter, 23 is a programmable timer for waiting time, 24 is a drive power source for driving a high frequency inductively coupled plasma mass spectrometer, and 25 is a counter for a pulse counter. It is. The operation of the embodiment of the present invention, which has such a main configuration, will be explained below using the time chart shown in Figure 2.The overall configuration and operation of the high frequency inductively coupled plasma mass spectrometer will be explained in Figure 3. Since this is the same as the case of the prior art example described above in detail, repeated explanation will be omitted here.

In FIG. 1, a pulse signal as shown in FIG. 2(A) is sent from the CPU 21 to the wait time programmable timer 23, and a wait time is set in the wait time programmable timer 23. Further, a signal as shown in FIG. 2 (b) is sent from the CPU 21 to the D/A converter 22, and the D/A
The mass axis is set in the converter 22. Like this D/A
When the mass axis is set in the converter 22, the waiting time programmable timer 23, which is preset to the optimum waiting time, starts operating. Further, when the waiting time Tw shown in FIG. 2(C) has elapsed and the operation of the waiting time programmable timer 23 is completed, a counter gate signal as shown in FIG. 2(D) is sent to the pulse counting counter 25. counter 25 for pulse counting
The gate opens. Note that the above waiting time 'T' W is set each time before setting the mass axis of the mass filter, and each time the mass axis is set, a different value is waited for as the above waiting time TW. It can be set in the time programmable timer 23. Further, the CPU 21 calculates an optimal waiting time for a predetermined square from a combination of the mass number and the mass number set immediately before, and sets the optimum waiting time in the waiting time programmable timer 23.

<Effects of the Invention> According to the present invention as explained in detail above, CP tJ
21, the optimal waiting time for a predetermined mass number is calculated from the combination of the quality V number and the mass number set immediately before, and is set in the waiting time programmable timer 23. A high-frequency inductively coupled plasma mass spectrometer is realized that eliminates unnecessary waiting time by changing the waiting time according to changes in circuit instability time.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the main part configuration of an embodiment of the present invention, FIG. 2 is an explanatory diagram of the overall configuration of a high frequency inductively coupled plasma mass spectrometer,
FIG. 3 is an explanatory diagram of the peripheral configuration of a high-frequency induction coil, and FIGS. 4 to 6 are diagrams for explaining mass axis settings in a conventional example. 1... Plasma torch, 2... Flow rate control unit, 3... Argon gas supply source, 4...
... Sample tank, 5 ... Nepizer, 6 ...
・High frequency induction coil, 7...High frequency inductively coupled plasma, 8...Nozzle, 9...Skimmer, 11...Fire chamber 13...・
・Center chamber 16... Mass filter, 17... Rear chamber 20... Signal processing section, 21...
... Central processing unit, 22 ... D/A converter, 23 ... Programmable timer, 24 ...
... Drive power supply, 25...Counter for pulse counter Figure 2r2]

Claims (1)

[Claims] The sample is excited using high-frequency inductively coupled plasma, and the generated ions are introduced into a vacuum and guided to a mass spectrometer detector through an ion optical system and a mass filter for detection. An analyzer that analyzes a measured element includes a microcomputer, a D/A converter, a programmable timer for waiting time that sets the waiting time to a different value each time the mass axis of the mass filter is set, and a high-frequency inductive coupling. A driving power source for driving a plasma mass spectrometer;
and a counter for a pulse counter, and the optimum value of the waiting time is calculated from a combination of a predetermined mass number and the mass number set by the programmable timer and set in the programmable timer. Inductively coupled plasma mass spectrometer.