JPH09251079A - Ion detecting system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To analyze the main component and the trace amount of component by one time sample introduction. SOLUTION: When necessary conditions such as the element to be analyzed and analyzing method are set from an input unit 21, a controller 19 connects switches 6, 12, 13 as indicated by solid lines when the element set with the analysis by a pulse detection type is analyzed. When a counted value is stored in a register 11, it is fetched and processed. The switches 6, 12, 13 are connected as indicated by broken lines when the element set by the analysis by an analog detection type is analyzed, data is fetched from an A/D converter 18 and processed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion detection system, and more particularly to an ion detection system capable of performing ion detection by an analog detection method and ion detection by a pulse detection method.

[0002]

2. Description of the Related Art As a method for detecting ions in a mass spectrometer, a pulse detection method is used.
Two methods of analog detection are known. Since the pulse detection method has a detection limit of about 10 ⁷ cps (count per second), the detection of ion current beyond this is performed by the analog detection method.

Therefore, in order to obtain a wide dynamic range in ion detection, it is desirable to have both a detection system by the pulse detection system and a detection system by the analog detection system so that either one can be selected. I can say.

On the other hand, Japanese Patent Laid-Open Nos. 6-181046 and 6-181047 disclose ion detection systems having a detection system based on a pulse detection method and a detection system based on an analog detection method. .

However, Japanese Laid-Open Patent Publication No. 6-181046,
In the one disclosed in Japanese Patent Application Laid-Open No. 6-181047, a preamplifier for an ion detection method and a preamplifier for an analog detection method are connected to one ion multiplier (hereinafter referred to as IMP). Therefore, there is a problem that the configuration of the preamplifier is very difficult.

First, since the required frequency band is different between the preamplifier for the ion detection method and the preamplifier for the analog detection method, it is impossible to connect these two preamplifiers to one IMP in the first place. Is.

Further, a preamplifier for the ion detection system and a preamplifier for the analog detection system are combined into one I.
When connected to MP, the stray capacitance increases, which causes a problem that the frequency band of the preamplifier for the ion detection system shifts to the lower side.

As described above, it is actually very difficult to connect the preamplifier for the ion detection system and the preamplifier for the analog detection system to one IMP.

The present invention solves the above-mentioned problems, and makes it possible to select the ion detection by the pulse detection method and the ion detection by the analog detection method, and avoid the above-mentioned problems concerning the preamplifier. It is an object of the present invention to provide an ion detection system capable of

It is another object of the present invention to provide an ion detection system capable of detecting a main component and an extremely small amount of components by introducing the sample once.

[0011]

In order to achieve the above-mentioned object, an ion detection system according to claim 1 has a first ion multiplier, a second ion multiplier and a first ion multiplier. Signal processing system that performs signal processing based on the analog detection method based on the output of the second ion processing system, and second signal processing system that performs signal processing based on the pulse detection method based on the output of the second ion multiplier And when ion detection based on analog detection is set, power is supplied to the first ion multiplier, and when ion detection based on pulse detection is set to second
And a power supply circuit for supplying power to the ion multiplier.

In the ion detection system according to the second aspect of the present invention, the first ion multiplier, the second ion multiplier, and the signal processing based on the output of the first ion multiplier based on the analog detection method. First to do
Second signal processing system, and second signal processing based on the pulse detection method based on the output of the second ion multiplier
Of the signal processing system and the first ion multiplier when the ion detection based on the analog detection is set, and the second ion multiplier when the ion detection based on the pulse detection is set. Power supply circuit that supplies power to the user interface, a user interface that sets whether to perform ion detection by analog detection or pulse detection for each element to be detected, and the element for which ion detection by analog detection is set For the element for which the detection result is output based on the output signal from the first signal processing system in the format corresponding to the analog detection, and the element for which the ion detection by the pulse detection is set is output from the second signal processing system. And a control unit that outputs a detection result in a format corresponding to pulse detection based on the output signal.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. In the following description, the ion detection system according to the present invention is applied to a high frequency inductively coupled plasma mass spectrometer (hereinafter referred to as ICPMS),
Therefore, the case of performing elemental analysis will be described.

FIG. 1 is a diagram showing an example of arrangement of two IMPs and conversion dynodes (hereinafter referred to as CDs) housed in a vacuum housing in an ion detection system according to the present invention, and FIG. 2 is an ion according to the present invention. It is a block diagram showing an embodiment of a circuit configuration of a detection system, in the figure,
1 is a vacuum housing, 2 is a collector slit, 3 is C
D, 4 is IMP, 5 is IMP, 6 is a switch, 7 is a power supply circuit, 8 is a preamplifier, 9 is a waveform shaping circuit, 10 is a counter, 11 is a register, 12 and 13 are switches, 14 is a power supply circuit, and 15 is D / A converter, 16 is a preamplifier, 1
7 is a main amplifier, 18 is an A / D converter, 19 is a control device, 20 is a monitor, and 21 is an input device.

The vacuum housing 1 contains a collector slit 2, a CD 3 and two IMPs 4 and 5. IMP4 is for performing ion detection by a pulse detection method, and IMP5 is for performing ion detection by an analog detection method.

Assuming that the ions flowing from the collector slit 2 are positive ions, when the pulse detection method is selected, the control device 19 causes the switches 6, 12,
13 is connected as shown by the solid line in FIG. As a result, CD3 and IMP5 are set to the ground potential, and a high voltage from the power supply circuit 14 is applied to IMP4.

The high voltage applied to the IMP 4 is supplied as digital data from the control device 19, but when the pulse detection method is selected, the control device 19 preliminarily sets it as a high voltage for ion detection by the pulse detection method. The determined digital data is set in the D / A converter 15.

This digital data is converted into an analog value by the D / A converter 15 and supplied to the power supply circuit 14, a high voltage of this analog value is generated in the power supply circuit 14, and this high voltage is passed through the switch 12. It is applied to IMP4.

As a result, the positive ions flowing from the collector slit 2 go straight as shown by the solid line in FIG.
It is incident on P4, converted into a pulse signal in IMP4, and output.

At this time, the pulse signal output from the IMP 4 is amplified by the preamplifier 8, shaped by the waveform shaping circuit 9, and input to the counter 10. The counter 10 counts the pulse signal during the gate time instructed by the controller 19. The count value of this counter 10 is the register 11
Is temporarily stored in the control unit 19 and is taken into the control device 19 at a predetermined timing. Then, when the control device 19 fetches the count value from the register 11, it clears the contents of the register 11.
The signal processing system from the preamplifier 8 to the register 11 is well known as a signal processing system in the pulse detection system, and therefore detailed description thereof will be omitted.

The above is the case where the pulse detection method is selected. When the analog detection method is selected, the control device 19 connects the switches 6, 12, and 13 as shown by the broken line in FIG. As a result, IMP4 is set to the ground potential, the high voltage from the power supply circuit 7 is supplied to CD3, and I3
A high voltage from the power supply circuit 14 is applied to MP5.

The high voltage applied to the IMP 5 is a high voltage set by the operator as described later.
When the high voltage is set, the controller 19 sets digital data corresponding to the high voltage in the D / A converter 15.

This digital data is converted into an analog value by the D / A converter 15 and supplied to the power supply circuit 14, a high voltage of this analog value is generated in the power supply circuit 14, and this high voltage is passed through the switch 12. It is applied to IMP5.

The power supply circuit 7 generates a predetermined high voltage, for example, a high voltage of about −10 kV, and this high voltage is supplied to the CD 3 via the switch 6.

As a result, the positive ions flowing from the collector slit 2 collide with CD3 as shown by the broken line in FIG. 1, and at this time, the secondary electrons emitted from CD3 are IMP5.
Will be incident on, converted into an electric signal in IMP5, and output.

At this time, the signal output from the IMP 5 is amplified by the preamplifier 16 and the main amplifier 17, respectively,
It is digitized by the A / D converter 18, input to the control device 19, and processed. Since the signal processing system including the preamplifier 16, the main amplifier 17, and the A / D converter 18 is well known as a signal processing system in the analog detection method, detailed description thereof will be omitted.

As described above, the signal processing system for the pulse detection system, the signal processing system for the analog detection system, and the CD
The high voltage power supply system applied to 3, IMP4, and IMP5 has been described. Next, the user interface (hereinafter, referred to as U / I) will be described.

Control device 19, monitor 20, input device 21
Constitutes the U / I in this ion detection system. The input device 21 is composed of a keyboard, a mouse and the like.

When the operator operates the input device 21 to detect ions, the controller 19 causes the monitor 2 to operate.
A screen for setting various conditions for performing elemental analysis is displayed at 0.

FIG. 3 is a diagram showing an example of the screen, and an item 30 for inputting an analysis element, an "analysis method" for setting whether to perform elemental analysis by a pulse detection method or an analog detection method. And an item of "IMP voltage" for selecting a voltage to be applied to the IMP. This "IMP voltage" item can be set only when ions are detected by an analog detection method.

Therefore, the operator inputs the element to be analyzed in the item indicated by 30 in the drawing from the keyboard, and when performing the elemental analysis by the pulse detection method, the display column of "pulse detection" in the item of "analysis method" is selected. Click with the mouse.

When performing elemental analysis by the analog detection method, click the "Analog detection" display field in the "Analysis method" section with the mouse, and select the desired voltage from the "IMP voltage" section. Click the display field with the mouse. Although three types of IMP voltages are displayed in FIG. 3, it goes without saying that more voltages may be displayed. Further, it goes without saying that the operator may input a numerical value from the keyboard for the voltage applied to the IMP 5.

When the operator sets all the elements to be analyzed and their analysis method and / or IMP voltage, the operator clicks the setting button 31 with the mouse. When the setting button 31 is clicked, the control device 19 takes in all the conditions set on the screen shown in FIG. 3 and starts the analysis operation. At this time, it is natural that the sample needs to be set.

First, the control device 19 determines, based on the set elements, in what order the signals corresponding to the set elements are obtained, and first, for the elements of the signals obtained. The switches 6, 12, and 13 are connected so as to correspond to the set detection method.

For example, now two elements α and β are set,
Assuming that the pulse detection type analysis is set for the element α and the analog detection type analysis is set for the element β, the control device 19 determines which element signal is first obtained. Then, if it is determined that the signal corresponding to the element α is first obtained, since the pulse detection method is set for the element α,
The controller 19 connects the switches 6, 12, and 13 as shown by the solid line in FIG. 2, sets digital data indicating a predetermined voltage to the D / A converter 15, and sets the gate of the counter 10 Set the time. This gate time may be determined in advance for each element to be analyzed.

As a result, the count value is stored in the register 11 as described above. When the control device 19 detects that the count value is stored in the register 11, the control device 19 fetches the count value from the register 11 at a predetermined timing. ,Remember. Then, the contents of the register 11 are cleared. The reason for clearing the contents of the register 11 in this manner is to prepare for the next analysis by the pulse detection method.

As described above, when the signal for one element, in this case, the element α is taken in, the control device 19 corresponds to the detection method set for the element of the signal obtained next, in this case the element β. The switches 6, 12, and 13 are connected as described above. In this case, since the analog detection method is set for the element β, the control device 19 connects the switches 6, 12, and 13 as shown by the broken line in FIG.
Digital data corresponding to the voltage set on the screen shown in FIG. 3 is set to the A converter 15.

As a result, as described above, the control device 19 takes in the digitized data from the A / D converter 18 and stores it.

When the data for the elements set as described above are fetched and stored, the control device 19 processes the respective data, and the elements for which the pulse detection method is set are suitable for the pulse detection method. The processing result is displayed in the format on the monitor 20, and the processing result is displayed on the monitor 20 in the format suitable for the analog detection method for the elements for which the analog detection method is set.

Since the data processing in the pulse detection method and the data processing in the analog detection method are well known, detailed description thereof will be omitted. For example, when the pulse detection method is set, the captured count value and gate The cps value, that is, the count value per second, is calculated from the relationship with time, and the concentration of the element is calculated from the relationship between the cps value and the calibration curve. An analog detection method is set. In this case, the peak portion of the captured data may be integrated and the concentration may be calculated from the integrated value.

The format in which the processing result is displayed on the monitor 20 can be arbitrarily determined. For example, the concentration obtained as a result of the processing may be displayed numerically for each element, or for the element for which the pulse detection method is set, a graph showing the relationship between the cps value and the concentration is displayed, and analog detection is performed. A graph showing the relationship between the integrated value and the concentration may be displayed for the element for which the method is set.

As is clear from the above description, since this ion detection system is provided with two IMPs, IMP4 for ion detection by the pulse detection method and IMP5 for ion detection by the analog detection method.
Since the above-mentioned problem that the stray capacitance increases does not occur in the preamplifiers 8 and 16, the preamplifiers 8 and 16 can be designed optimally for analog detection for pulse detection.

Further, it is possible to set a plurality of elements to be analyzed, and further, it is possible to set whether to perform the analysis by the pulse detection method or the analysis by the analog detection method for each element. It is also possible to detect a trace amount of components.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and various modifications can be made.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of arrangement of two IMPs and conversion dynodes housed in a vacuum housing in an ion detection system according to the present invention.

FIG. 2 is a block diagram showing an embodiment of a circuit configuration of the ion detection system according to the present invention.

FIG. 3 is a diagram showing an example of a screen for setting various conditions for elemental analysis.

[Explanation of symbols]

1 ... Vacuum housing, 2 ... Collector slit, 3 ... C
D, 4 ... IMP, 5 ... IMP, 6 ... Switch, 7 ... Power supply circuit, 8 ... Preamplifier, 9 ... Waveform shaping circuit, 10 ... Counter, 11 ... Register, 12, 13 ... Switch, 14 ...
Power supply circuit, 15 ... D / A converter, 16 ... Preamplifier, 1
7 ... Main amplifier, 18 ... A / D converter, 19 ... Control device, 20 ... Monitor, 21 ... Input device.

Claims (2)

[Claims] 1. A first ion multiplier, a second ion multiplier, and a first signal processing system for performing signal processing based on an output of the first ion multiplier based on an analog detection method. A second signal processing system that performs signal processing based on the pulse detection method based on the output of the second ion multiplier, and a power source for the first ion multiplier when ion detection based on analog detection is set. And a power supply circuit that supplies power to the second ion multiplier when ion detection based on pulse detection is set. 2. A first ion multiplier, a second ion multiplier, and a first signal processing system for performing signal processing based on the output of the first ion multiplier based on an analog detection method. A second signal processing system that performs signal processing based on the pulse detection method based on the output of the second ion multiplier, and a power source for the first ion multiplier when ion detection based on analog detection is set. Is supplied, and if ion detection based on pulse detection is set, the power supply circuit that supplies power to the second ion multiplier and ion detection by analog detection or by pulse detection for each element to be detected The user interface that sets whether to detect ions, and the first signal for the elements for which ion detection by analog detection is set Based on the output signal from the science,
The detection result is output in a format corresponding to analog detection, and for the elements for which ion detection by pulse detection is set, the detection result is output in a format corresponding to pulse detection based on the output signal from the second signal processing system. An ion detection system, comprising: an output control unit.