JPH03145051A - High frequency inductive coupling plasma mass analyzing meter - Google Patents

Abstract

PURPOSE:To eliminate the necessity of over sampling or an equalization circuit for measuring an analog mode by measuring the output of a dual mode secondary electronic doubling tube by both of a pulse count mode and an analog mode, and counting the output of a V/F converter with a counter for an analog mode. CONSTITUTION:The output of a dual mode secondary electronic doubling tube 21, which is the detector of a mass analyzing meter, is measured by both of a pulse count mode and an analog mode, a V/F converter 31 is provided to a signal treating part 20 of the analog mode, and the output of the V/F converter 31 is counted with an analog mode counter 32 acting in the same gate timing as the gate timing of a pulse counting counter 28. Consequently the concept of an integral time same as the pulse count mode can be introduced into the analog mode too. This eliminates the necessity of over sampling or an equalization circuit for measuring an analog mode.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention supplies high-frequency energy to a high-frequency induction coil to form a high-frequency magnetic field to generate high-frequency inductively coupled plasma, and uses the plasma to excite a sample. The present invention relates to a high-frequency inductively coupled plasma mass spectrometer that analyzes an element to be measured in the sample by generating ions through a nozzle and a skimmer, and guiding the ions to a mass spectrometer for detection through an interface consisting of a nozzle and a skimmer.

<Prior Art> FIG. 3 is an explanatory diagram of a general configuration of an analyzer using high-frequency inductively coupled plasma. In this figure, argon gas is supplied to the outer chamber 1b and the outermost chamber IC of the plasma torch 1 from an argon gas supply source 3 via a gas regulator 2.
A solid sample in the sample introducing device 4 is vaporized by a laser beam irradiated from a laser light source 5 and then carried into the inner chamber 1a by argon gas as a carrier gas. If the sample is a liquid, the sample introduction device 24 and laser light source 5 shown in FIG. 3 are removed, and a nebulizer is installed to atomize the liquid sample to be introduced and supply it to the inner chamber 1a of the plasma torch 1. Also, the sample is more likely to be a liquid than a solid.

On the other hand, a high-frequency current is passed through a high-frequency induction coil 6 wound around the plasma torch 1 by a high-frequency power supply 10, and a high-frequency magnetic field (not shown) is formed around the coil 6. When electrons or ions are implanted in argon gas near the magnetic field, high frequency inductively coupled plasma 7 is instantaneously generated by the action of the high frequency magnetic field.

In addition, the inside of the forechamber body 11 sandwiched between the nozzle 8 and the skimmer 9 is pumped by a vacuum pump 12, for example.
It is attracted to o r r. Furthermore, ion lenses 14a and 14b are provided inside the center chamber 13, and the inside of the center chamber 13 is
The oil is sucked to, for example, 10-' Torr by the oil diffusion pump 15, and then passed through a mass filter (for example, a quadrupole mass filter).
The interior of the rear chamber 17 housing the oil pump 16 is suctioned to, for example, 10'''' Torr by the second oil diffusion pump 18.

In this state, the sample vaporized as described above is introduced into the high-frequency inductively coupled plasma, and ionization and light emission are performed. The ions in the plasma 7 are transferred to the nozzle 8. skimmer 9
．． and the ion lens 1 via the extraction electrode 9-.
4a and 14b (or a doublet quadrupole lens), and is then guided to the secondary electron multiplier tube 19 through the mass filter 16 and detected. This detection signal is sent to the signal processing section 20. By being sent out and subjected to calculation and processing, the analysis value of the element to be measured in the sample is determined.

On the other hand, high-frequency inductively coupled plasma mass spectrometers have a very wide dynamic range of signal intensity (e.g. over l〇-).
Therefore, when a single secondary electron multiplier tube has a strong signal, it is used in analog mode, and when it is weak, it is switched to pulse count mode to detect ions. In this case, in pulse count mode, the concept of integration time for counting pulses is important; the longer the integration time, the higher the S/N ratio.
The ratio was starting to improve. That is, FIG. 4 is a block circuit diagram showing a specific configuration of the signal processing section 20,
When the intensity of the ions incident on the dual mode secondary electron multiplier 21 (corresponding to the secondary electron multiplier 19 in FIG. 3) is strong, the analog output of the dual mode secondary electron multiplier 21 is After being amplified by the current/voltage conversion amplifier 22, it is sampled and held for a certain period of time in the sample hold circuit 23, and then A/D converted by the A/D converter 24, and then sent to the central processing unit f (CPU) 30. In addition, when the intensity of ions incident on the dual mode secondary electron multiplier tube 21 is weak, the pulse output of the dual mode secondary electron multiplier tube 21 is amplified by the pulse amplifier 26 for pulse counting. After that, the waveform is shaped by a waveform shaping discriminator 27, and then counted by a counter 28, and the counter output signal is sent to a central processing unit (CPU).
30 for arithmetic processing. The sample hold circuit 23 and the A/D converter 24 are controlled by a sampling timing generation circuit 25 that receives commands from the CPU 30, and the timing of the counter 28 is adjusted by a counter gate timing generation circuit 29 that receives commands from the CPU 30. It has become.

<Problems to be Solved by the Invention> However, in the above conventional example, when measuring ions in analog mode, - the A/D converter in the membrane is
When used as the converter 24, the A/D converter is difficult to familiarize with the concept of integration time, so it has the disadvantage that measurement takes a long time and data must be manipulated by sampling several times.

The present invention has been made in view of this situation, and its object is to introduce the concept of integration time similar to the pulse count mode to the analog mode, and to provide oversampling and averaging circuits for measuring the analog mode. An object of the present invention is to provide a high-frequency inductively coupled plasma mass spectrometer that does not require a high-frequency inductively coupled plasma mass spectrometer.

Means for Solving the Problems> The present invention supplies high frequency energy to a high frequency induction coil to form a high frequency magnetic field to generate high frequency inductively coupled plasma, and uses the plasma to excite a sample to generate ions. , in a high-frequency inductively coupled plasma mass spectrometer that analyzes the analyte element in the sample by guiding the ions to the mass spectrometer through an interface consisting of a nozzle hiskimmer and detecting them. The output of a certain dual-mode secondary electron multiplier tube is measured in both pulse count mode and analog mode, and a V/F converter is provided in the signal processing section of the analog mode, and the output of the V/F converter is pulse counted. This problem is solved by counting with an analog mode counter that operates at the same gate timing as the analog mode counter.

Similarly, the present invention supplies high-frequency energy to a high-frequency induction coil to form a high-frequency magnetic field to generate high-frequency inductively coupled plasma, excites a sample using the plasma to generate ions, and generates ions. In a high-frequency inductively coupled plasma mass spectrometer that analyzes the analyte element in the sample by guiding it to the mass spectrometer for detection through an interface consisting of a nozzle and a skimmer, the dual-mode dual-mode detector of the mass spectrometer is used. The output of the electron multiplier tube is measured in both pulse counting mode and analog mode, and a V/F converter is provided in the signal processing section of the analog mode, and the output of the V/F converter is pulse counted via a multiplexer. The above-mentioned problem is solved by counting with a counter.

Function> The present invention functions as follows. That is, the output of a dual-mode secondary electron multiplier tube, which is a detector of a mass spectrometer, is measured in both a pulse count mode and an analog mode, and a V/F converter is installed in the signal processing section of the analog mode, and the V/F converter is installed in the analog mode signal processing section. /
The basic method is to count the output of the F converter with an analog mode counter that operates at the same gate timing as the pulse counting counter, or to count the output of the V/F converter with a pulse counting counter via a multiplexer. Therefore, the concept of integration time similar to the pulse count mode can be introduced to the analog mode, and there is no need for oversampling or averaging circuits for measuring the analog mode.

<Example> Hereinafter, the present invention will be described in detail using the drawings. 1st
The figure is a block explanatory diagram showing the main parts of an embodiment of the present invention,
In the figure, the same symbols as in FIG. 3 are used with the same meaning, and repeated explanation will be omitted here.

Further, 31 is a V/F converter that converts voltage into frequency;
2 is an analog counter, and 33 is a gate time generation circuit that controls the analog counter 32 and the analog mode counter 28 in response to instructions from the CPU 30. In the embodiment of the present invention having a block circuit with such a main part configuration, the current (analog) output of the dual mode secondary electron intensifier tube 21 is amplified by the current/voltage amplifier 22 and then sent to the V/F transformer. V/F conversion is performed at 31, and then
The analog counter 32 counts, and the output signal of the counter is processed by the CPtJ 30. Further, the pulse output of the dual mode secondary electron multiplier 21 is amplified by a pulse amplifier 26 for pulse counting, then waveform-shaped by a waveform shaping discriminator 27, and then,
The analog mode counter 28 counts and the output signal of the counter is processed by the CPU 30. Note that the analog counter 32 and the analog mode counter 28 are CP
It is controlled by the gate time generation circuit 33 which receives the command from U30.

In this way, when measuring the output of the dual mode secondary electron multiplier 21 in both the pulse count mode and the analog mode, the V/F converter 31 is provided in the analog mode signal processing section. Since the output is counted by the counter 32 which operates at the same gate timing as the gate timing of the pulse counting counter 28, the concept of integration time similar to the pulse counting mode can be introduced to the analog mode. This is a high-frequency inductively coupled plasma mass spectrometer that does not require oversampling or averaging circuits.

On the other hand, FIG. 2 is a block explanatory diagram showing the main parts of another embodiment of the present invention. In the figure, the same symbols as in FIGS. is omitted6
ct, 34 is a multiplexer. In another embodiment of the present invention having a block circuit with such a main part configuration, the output of the dual mode secondary electron multiplier 21 is a current
After being amplified by the voltage conversion amplifier 22, the V/F converter 31
V/F conversion is performed. Further, the output of the dual mode secondary electron multiplier 21 is amplified by a pulse amplifier 26 for pulse counting, and then waveform-shaped by a waveform-shaping discriminator 27. The outputs of the V/F converter 31 and the waveform shaping discriminator 27 are sent to a multiplexer 34, and sequentially sent to a counter 28 from the multiplexer. The counter 28 counts the pulses sent out from the multiplexer 34, and the output signal is sent to the central processing unit (C
PtJ) 30 for arithmetic processing. Note that the counter 28 is controlled by the gate time generation circuit 3 which receives the command from the CPU 30.
3 and multiplexer 34 is controlled by CP
It is now directly controlled by the U30 commander.

In this way, when measuring the output of the dual mode secondary electron multiplier 21 in both the pulse count mode and the analog mode, the V/F converter 31 is provided in the analog mode signal processing section. The output of multiplexer 34
Since the counter 28 is used to count through the
This is a high-frequency inductively coupled plasma mass spectrometer that can introduce the same integration time concept to the analog mode as the pulse count mode, and does not require oversampling or averaging circuits for measuring the analog mode.

<Effects of the Invention> According to the present invention as described in detail above, in a high-frequency inductively coupled plasma mass spectrometer, the output of the dual-mode secondary electron multiplier tube, which is the detector of the mass spectrometer, is divided into pulse count mode and analog mode. A V/F converter is installed in the signal processing section of the analog mode, and the V/F
Either count the converter output with an analog mode counter that operates at the same gate timing as the pulse counting counter, or count one output of the V/F converter with a counter that is shared with the pulse counting counter via a multiplexer. I made it count. For this reason, a high-frequency inductively coupled plasma 'jlR analyzer has been realized that can introduce the same integration time concept to the analog mode as the pulse count mode and does not require oversampling or averaging circuits for measuring the analog mode. do.

[Brief explanation of the drawing]

Fig. 1 is a block explanatory diagram showing the main part of an embodiment of the present invention, Fig. 2 is a block explanatory diagram showing the main part of another embodiment of the invention, and Fig. 3 is a general diagram of a high frequency inductively coupled plasma mass spectrometer. FIG. 4 is a block diagram showing the main parts of the conventional example. 1... Plasma torch, 2... Flow rate control unit, 3... Argon gas supply source, 4...
...Sample cell, 6...High frequency induction coil, 7...High frequency inductively coupled plasma, 8...
・Nozzle, 9...Skimmer 16...
Mass filter, 17... Rear chamber, 20
...Signal processing unit, 21...Dual mode secondary electron multiplier 22...Current/voltage conversion amplifier 23...Sample and hold circuit 24...・
... A/D converter 26 ... Pulse counting pulse amplifier 27 ... Waveform shaping discriminator 28.3
2... Counter 30... Central processing unit (CPtJ) 31...
...V/F converter, 33...Gate time generation circuit, 34...
・Multiplexer 1 Figure 2 Generation circuit

Claims (2)

[Claims] (1) Supply high-frequency energy to a high-frequency induction coil to form a high-frequency magnetic field to generate high-frequency inductively coupled plasma, use the plasma to excite the sample to generate ions, and send the ions through an interface consisting of a nozzle and a skimmer. In a high-frequency induction plasma mass spectrometer that analyzes an element to be measured in the sample by guiding it to a mass spectrometer for detection, Measure the output in both pulse count mode and analog mode, and apply V/V to the signal processing section of the analog mode.
A high frequency inductively coupled plasma mass spectrometer, characterized in that an F converter is provided and the output of the V/F converter is counted by an analog mode counter that operates at the same gate timing as a pulse counting counter. (2) Supply high-frequency energy to a high-frequency induction coil to form a high-frequency magnetic field to generate high-frequency inductively coupled plasma, use the plasma to excite the sample to generate ions, and send the ions through an interface consisting of a nozzle and a skimmer. A high-frequency inductively coupled plasma mass spectrometer that analyzes the analyte element in the sample by guiding it to a mass spectrometer for detection, comprising: a dual-mode secondary electron multiplier tube that is a detector of the mass spectrometer; Measure the output in both pulse count mode and analog mode, and apply V/ to the signal processing section of the analog mode.
1. A high frequency inductively coupled plasma mass spectrometer, characterized in that an F converter is provided and the output of the V/F converter is counted by a pulse counting counter via a multiplexer.