JP2021114438A - Mass spectrometer - Google Patents

Abstract

To provide a method for predicting a filament lifetime of an ion source of a mass spectrometer.SOLUTION: A gas chromatograph mass spectrometer 1 includes a gas chromatograph unit 10, a mass spectrometer 20 that analyzes the mass of molecules that have passed through the gas chromatograph unit 10, and a control device 31 that controls the gas chromatograph unit 10 and the mass spectrometer 20. The mass spectrometer 20 includes a filament 212. The control device 31 includes a current monitoring unit 311 that monitors a current flowing through the filament 212, and a warning processing unit 312 that notifies a warning when a current value detected by the current monitoring unit 311 is lower than a determination value.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a mass spectrometer.

In the chromatographic mass spectrometer, the components of the sample are temporally separated by the column of the chromatograph unit and introduced into the mass spectrometer, and the sample is ionized by the mass spectrometer, and then the mass spectrum is sequentially acquired. One of the methods for ionizing a sample in the mass spectrometer is an electron ionization (EI) method. In the electron ionization method, generally, thermoelectrons are generated by heating a filament, and the thermoelectrons are accelerated by an acceleration voltage and then collided with a molecule of a sample to ionize the molecule. Japanese Unexamined Patent Publication No. 2018-32481 discloses an example of such a mass spectrometer.

JP-A-2018-32481

As described above, filaments are used in the mass spectrometer. Here, in order to emit electrons from the filament, it is necessary to pass a certain current or more through the filament. When an electric current is repeatedly passed through the filament in order to emit electrons from the filament, the filament itself gradually deteriorates. Therefore, the filament eventually reaches the end of its life and breaks.

If the filament breaks during mass spectrometry, the analysis is interrupted. Therefore, in the conventional chromatograph mass spectrometer, the same analysis is performed again when the filament is broken. However, if the analysis takes time, it is a burden for the user to repeat the same analysis again. In addition, since the sample for analysis is required again, it is difficult to obtain the result when the sample is limited. Therefore, it is desirable to predict filament life and replace filaments before filament breakage occurs during analysis.

An object of the present invention is to provide a mass spectrometer capable of predicting filament life.

A first aspect of the present invention relates to a gas chromatograph mass spectrometer. The gas chromatograph mass spectrometer includes a gas chromatograph unit, a mass spectrometer that performs mass spectrometry of molecules that have passed through the gas chromatograph unit, and a control device that controls the gas chromatograph unit and the mass spectrometer. The mass spectrometer comprises a filament. The control device includes a current monitoring unit that monitors the current flowing through the filament, and a warning processing unit that notifies a warning when the current value detected by the current detection unit is lower than the determination value.

In the mass spectrometer of the present disclosure, since the user can know that the life of the filament of the mass spectrometer is approaching, it is possible to eliminate waste such as the filament being cut during the analysis and the analysis being performed again.

It is a figure which shows the whole structure of a gas chromatograph mass spectrometer. It is a figure which shows the structure of the ion source 21 in Embodiment 1. FIG. It is a flowchart for demonstrating the filament life determination process which a control device executes. It is a figure which shows the structure of the ion source 21A used in Embodiment 2. It is a circuit diagram which shows the structure of the AC power supply circuit 213A and the current detection unit 218A.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are designated by the same reference numerals, and the description thereof will not be repeated.

[Embodiment 1]
FIG. 1 is a diagram showing the overall configuration of a gas chromatograph mass spectrometer. The gas chromatograph mass spectrometer 1 shown in FIG. 1 includes a gas chromatograph unit 10 and a mass spectrometer 20. The gas chromatograph unit 10 includes an injector 11 for introducing a sample and a column 12 for separating the components of the sample introduced by the injector 11.

The mass spectrometer 20 is determined by an ion source 21 that ionizes the molecules of the sample that has passed through the column 12, an ion lens 22 that converges the ions ionized by the ion source 21, and the applied voltage by controlling the applied voltage. It includes a quadrupole filter 23 that allows only ions having a mass-charge ratio to pass through, and a detector 24 that detects ions that have passed through the quadrupole filter 23. The entire mass spectrometer 20 is housed in a vacuum vessel 25, and the inside of the vacuum vessel 25 is kept in a vacuum by a vacuum pump 26.

The gas chromatograph mass spectrometer 1 further includes a control device 31 for controlling the operation of each unit, an input unit 32 for inputting various analysis conditions by the user, and a display unit 33 for displaying various information. The control device 31, the input unit 32, and the display unit 33 are embodied by the hardware and software of the personal computer (PC) 30.

FIG. 2 is a diagram showing the configuration of the ion source 21 in the first embodiment. The ion source 21 of FIG. 1 has an ionization chamber 211 as shown in FIG. The wall of the ionization chamber 211 is made of a conductive material and is grounded. In the ionization chamber 211, a sample molecule introduction port (not shown) for introducing the sample molecule that has passed through the column 12, an ion outlet 222 for drawing out the ionized ion of the sample molecule, and heat for introducing thermions. An electron introduction port 223 and a thermionic outlet 224 for transmitting thermoelectrons are provided. The ion lens 22 shown in FIG. 1 is provided outside the ion outlet 222, and electrons in the ionization chamber 211 are drawn out to the ion lens 22 side by the potential difference between the ion lens 22 and the ionization chamber 211.

Further, the ion source 21 includes a filament 212 for generating thermions, which is arranged outside the thermionic introduction port 223. A DC power supply circuit 213 and a current detection unit 218 for measuring the current flowing through the DC power supply circuit 213 are connected to the filament 212. The DC power supply circuit 213 is a filament power supply in which the voltage applied to the filament 212 is variable. The voltage of the DC power supply circuit 213 is controlled by the control device 31. Between the filament 212 and the wall (that is, ground) of the ionization chamber 211, a bias power supply circuit 214 that imparts a potential difference with the filament 212 side negative and heat that detects the current corresponding to thermions emitted from the filament 212. An electronic ammeter 219 is connected in series. The bias power supply circuit 214 generates a potential difference for accelerating thermions.

The ion source 21 further includes a thermionic collector 215 arranged outside the thermionic outlet 224. The thermionic collector 215 collects thermionic electrons generated by the filament 212 and passed through the ionization chamber 211. A collector power supply 216 that imparts a positive potential difference on the thermoelectron collector 215 side between the thermoelectron collector 215 and the wall (ground) of the ionization chamber 211, and thermoelectrons flowing between the filament 212 and the thermionic collector 215. A thermionic current meter 217 for measuring the value of the current is connected. In FIG. 2, the thermionic ammeters 217 and 219 are provided for observing thermionic electrons, but only one of the thermionic ammeters 217 and 219 may be provided.

The control device 31 has a function of performing various processes of the gas chromatograph mass spectrometer 1, but here, the current monitoring unit 311 and the warning, which are configured to issue a warning when the life of the filament 212 is approaching. The processing unit 312 will be described. The current monitoring unit 311 receives a signal indicating a current value, which is an output value from the current detection unit 218. The warning processing unit 312 determines whether or not the value of the thermionic current detected by the current monitoring unit 311 is smaller than the determination value. When the value of the thermionic current detected by the current monitoring unit 311 becomes smaller than the determination value, the warning processing unit 312 transmits a signal for displaying a warning to the display unit 33.

There is a correlation between the magnitude of the filament current and the deterioration of the filament 212. As the filament 212 deteriorates, the resistance value of the filament 212 increases, and the filament current decreases in order to keep the electrons emitted from the filament 212 constant.

Therefore, in the present embodiment, the deterioration of the filament 212 is determined by monitoring the filament current at regular time intervals by the current monitoring unit 311 that monitors the filament current.

The method of determining deterioration is, for example, that the filament current in a new state of the filament is stored in a memory or the like, and when the filament current drops to a certain ratio (for example, about 70%), it is time for the user to replace it. Notify.

FIG. 3 is a flowchart for explaining the filament life determination process executed by the control device. First, in step S1, the control device 31 monitors the output of the current detection unit 218 and measures the current. Then, in step S2, the time after the filament 212 is replaced is confirmed, and it is determined whether or not the filament 212 has just been replaced. For example, when the filament 212 is replaced, the timer for measuring the elapsed time is initialized, and when a current is passed through the filament 212, the control device 31 is configured so that the time is counted by the timer. There is.

If the filament 212 has just been replaced in step S2, in step S3, the control device 31 stores the current value measured in step S1 as a reference value in the memory. On the other hand, if it is not immediately after the filament 212 is replaced in step S2, the process proceeds to step S4.

In step S4, the control device 31 divides the current value measured in step S1 by the reference value stored in step S3 to calculate the current reduction rate, and determines whether or not the value is smaller than the determination value. to decide. For example, the determination value is 70% or the like.

When the rate of decrease in current is equal to or greater than the determination value (NO in S4), the control device 31 determines that the filament 212 has not reached the end of its life for a while, and proceeds to step S6 without issuing a warning.

If the rate of decrease in current is smaller than the determination value (YES in S4), the control device 31 determines that the filament 212 is about to reach the end of its life, displays a warning in step S5, and then proceeds to step S6. The warning is not limited to the display of an image or the like, and may be a warning sound such as a warning lamp or a buzzer.

As described above, the mass spectrometer 20 according to the first embodiment outputs a warning to the user before the filament 212 reaches the end of its life and expires. This allows the user to replace the filament 212 before the sample undergoes limited mass spectrometry or time-consuming mass spectrometry, thus avoiding the need for reanalysis. ..

The first embodiment described above will be summarized. The gas chromatograph mass spectrometer 1 shown in FIG. 1 controls a gas chromatograph unit 10, a mass spectrometer 20 that performs mass spectrometry of molecules that have passed through the gas chromatograph unit 10, a gas chromatograph unit 10 and a mass spectrometer 20. A control device 31 is provided. The mass spectrometer 20 includes a filament 212. The control device 31 includes a current monitoring unit 311 that monitors the current flowing through the filament 212, and a warning processing unit 312 that notifies a warning when the current value detected by the current monitoring unit 311 is lower than the determination value.

As shown in FIG. 2, the mass analyzer 20 applies a direct current between the bias power supply circuit 214 that applies a reference potential to the first end of the filament 212 and the first end of the filament 212 and the second end of the filament 212. The DC power supply circuit 213 to be applied and the current detection unit 218 for detecting the current flowing through the DC power supply circuit 213 are further included. The current detection unit 218 detects the current flowing through the filament 212 by detecting the current flowing through the DC power supply circuit 213.

Since the bias power supply circuit 214 applies a negative high potential (-10 to -250 V) bias potential to the filament, the current detection unit 218 is composed of high withstand voltage electronic components.

According to the gas chromatograph mass spectrometer according to the first embodiment, a warning is notified before the filament 212 expires, so that the user should take measures such as replacing the filament 212 with a new one in advance before the analysis. Can be done. Therefore, waste of time and sample can be eliminated.

[Embodiment 2]
In the ion source 21 shown in FIG. 2 of the first embodiment, the DC power supply circuit 213 is used as the filament power supply. A bias power supply circuit 214 is connected to the DC power supply circuit 213 and is coupled to a negative high potential (-10 to −250 V). Therefore, the current detection unit 218 for measuring the current flowing through the filament 212 needs to be composed of a high withstand voltage electronic component or separately insulated by an insulating circuit. On the other hand, in the second embodiment, the filament power supply is changed to an AC power supply circuit having a built-in isolation transformer so that an ammeter having a low withstand voltage can be used.

FIG. 4 is a diagram showing the configuration of the ion source 21A used in the second embodiment. In the second embodiment, the mass spectrometer 20 includes the ion source 21A shown in FIG. 4 instead of the ion source 21 shown in FIG. In the configuration of the ion source 21 shown in FIG. 2, the ion source 21A includes an AC power supply circuit 213A and a current detection unit 218A instead of the DC power supply circuit 213 and the current detection unit 218. Since the configuration of other parts of the ion source 21A is the same as that of the ion source 21, the description will not be repeated.

In the mass spectrometer 20, as shown in FIG. 4, the ion source 21A is located between the bias power supply circuit 214 that gives a reference potential to the first end of the filament 212 and the first end of the filament 212 and the second end of the filament. It further includes an AC power supply circuit 213A to which an AC current is applied. The current detection unit 218A detects the current flowing through the filament 212 by detecting the current flowing through the AC power supply circuit 213A. Since the other configurations of the ion source 21A are the same as those of the ion source 21 of FIG. 2, the description will not be repeated.

FIG. 5 is a circuit diagram showing the configuration of the AC power supply circuit 213A and the current detection unit 218A. As shown in FIG. 5, the AC power supply circuit 213A includes a transformer 243 in which the first end and the second end of the filament 212 are connected to the first end and the second end of the secondary side coil 245, and the secondary side coil, respectively. It includes a current supply circuit 246 that supplies a current to the primary coil 244 of the transformer so that the direction of the magnetic flux passing through the inside of the 245 changes alternately. The current detection unit 218A is configured to detect the current flowing through the current supply circuit 246.

With such a configuration, since the AC power supply circuit 213A is interposed between the current detection unit 218A and the negative high potential of the bias power supply circuit 214, the current detection unit 218A can be composed of electronic components having a low withstand voltage. can.

In the primary coil 244, the intermediate tap TM is connected to the power node VCS. The current supply circuit 246 includes a first switching element 241 connected between the first end T1 of the primary coil 244 and the voltage detection node N1, the second end T2 of the primary coil 244, and the voltage detection node N1. The second switching element 242 connected between the two, the drive circuit 247 that alternately conducts the first switching element 241 and the second switching element 242, and the voltage detection node N1 and the grounding node GND are connected to each other. Includes a current detection resistor 251 and the like. The drive circuit 247 is controlled by the control device 31. The current detection unit 218A includes an A / D converter 254 that detects a potential difference between the voltage detection node N1 and the ground node GND.

With such a configuration, the current detection unit 218A and the negative high potential (-10 to -250V) of the bias power supply circuit 214 are insulated by the transformer 243, so that the current detection unit 218A is an electron with a low withstand voltage. It can be composed of parts.

The warning processing unit 312 receives a signal from the A / D converter 254 that converts the voltage of the voltage detection node N1 into a digital value. The warning processing unit 312 includes a memory 322 (ROM (Read Only Memory) and RAM (Random Access Memory)), a CPU (Central Processing Unit) 321 and an input / output buffer (not shown). The CPU 321 corresponds to a "control unit" that expands and executes a program stored in the ROM in a RAM or the like. The program stored in the ROM is a program in which the processing procedure of the CPU 321 is described. Various tables (maps) used for various operations are also stored in the ROM. The CPU 321 executes various processes in the warning processing unit 312 according to these programs and tables. The processing is not limited to software, but can also be executed by dedicated hardware (electronic circuit).

The memory 322 corresponds to a "storage unit" that stores the current value flowing through the filament 212 as a reference value when the filament 212 is normal. The CPU 321 corresponds to a "determination unit" that determines the deterioration state of the filament 212 by comparing the reference value with the current value flowing through the filament 212 detected by the current detection unit 218A.

The initial current of the new filament 212 may vary from individual to individual. If the value of this initial current is stored in the memory 322 of the warning processing unit 312 and the threshold value for issuing a warning is determined to be 70% of the initial current, even if the initial current of the filament 212 varies. , Life can be estimated for individual filaments.

In the circuit shown in FIG. 5, if the instantaneous value of the current flowing through the filament 212 is Ifil and the average value of the current is Ifilave, Ifilave can be expressed by the following equation (1).
Ifilave = (Ns / Np) x Vcc / Rfil x Duty ... (1)
In the formula (1), Np indicates the number of primary windings of the transformer 243, Ns indicates the number of secondary windings of the transformer 243, Rfil indicates the resistance value of the filament 212, Vcc indicates the power supply voltage, and Duty. Indicates the ON time / (ON time + OFF time) of each of the first switching element 241 and the second switching element 242.

Further, when the instantaneous value of the current flowing through the current detection resistor 251 is indicated by Ir and the average value is indicated by Irave, Irave can be expressed by the following equation (2). Here, since the exciting current flowing through the transformer 243 is sufficiently smaller than that of Irave, it is ignored.
Irave = (Ns / Np) × Ifilave… (2)
From the above, the average value Ifilave of the current value flowing through the filament 212 can be easily obtained by measuring the average value Irave of the current value flowing through the current detection resistor 251 and back-calculating this.

According to the gas chromatograph mass spectrometer shown in the second embodiment, deterioration of the filament can be determined by monitoring the filament current as in the first embodiment. Also, before the filament breaks, tell the user that it is about to break and have it replaced to prevent the filament from breaking during analysis.

Further, according to the gas chromatograph mass spectrometer shown in the second embodiment, an ammeter having a low withstand voltage can be used for measuring the current of the filament 212.

[Aspect]
It will be understood by those skilled in the art that the above-described exemplary embodiments are specific examples of the following embodiments.

(1) The first aspect of the present disclosure relates to a gas chromatograph mass spectrometer. The gas chromatograph mass spectrometer includes a gas chromatograph unit, a mass spectrometer that performs mass spectrometry of molecules that have passed through the gas chromatograph unit, and a control device that controls the gas chromatograph unit and the mass spectrometer. The mass spectrometer comprises a filament. The control device includes a current monitoring unit that monitors the current flowing through the filament, and a warning processing unit that notifies a warning when the current value detected by the current monitoring unit is lower than the determination value.

According to the gas chromatograph mass spectrometer of the first item, since the warning is notified before the filament expires, the user can take measures such as replacing the filament in advance before the analysis. Therefore, waste of time and sample can be eliminated.

(Item 2) In the gas chromatograph mass spectrometer according to the first item, the mass spectrometer includes a bias power supply circuit that applies a reference current to the first end of the filament, and the first end of the filament and the second end of the filament. Further includes a DC power supply circuit for applying a DC current between the two, and a current detection unit. The current detection unit detects the current flowing through the filament by detecting the current flowing through the DC power supply circuit.

(Item 3) In the gas chromatograph mass spectrometer according to item 2, the current detection unit is composed of high withstand voltage electronic components.

According to the gas chromatograph mass spectrometers of the second and third terms, time and sample waste can be eliminated in the configuration using the conventional DC power supply circuit.

(Item 4) In the gas chromatograph mass spectrometer according to the first item, the mass spectrometer includes a bias power supply circuit that applies a reference current to the first end of the filament, and the first end of the filament and the second end of the filament. Further includes an AC power supply circuit for applying an AC current between the two, and a current detection unit. The current detection unit detects the current flowing through the filament by detecting the current flowing through the AC power supply circuit.

(Clause 5) In the gas chromatograph mass analyzer according to the fourth item, in the AC power supply circuit, the first end and the second end of the filament are connected to the first end and the second end of the secondary coil, respectively. It includes a transformer and a current supply circuit that supplies current to the primary coil of the transformer so that the direction of the magnetic flux passing through the inside of the secondary coil changes alternately. The current detection unit is configured to detect the current flowing through the current supply circuit.

(Section 6) In the gas chromatograph mass spectrometer according to the fifth item, the intermediate tap of the primary side coil is connected to the power supply node. The current supply circuit has a first switching element connected between the first end of the primary coil and the voltage detection node, and a second switching element connected between the second end of the primary coil and the voltage detection node. It includes a two-switching element, a drive circuit that alternately conducts a first switching element and a second switching element, and a resistance element connected between a voltage detection node and a grounding node. The current detection unit includes an A / D converter that detects a potential difference between the voltage detection node and the ground node.

According to the gas chromatograph mass spectrometer of the fourth to sixth paragraphs, since the AC power supply circuit is interposed between the current detection unit and the negative high potential of the bias power supply circuit, the current detection unit is an electronic component having a low withstand voltage. Can be configured with.

(Item 7) In the gas chromatograph mass spectrometer according to any one of items 1 to 6, the warning processing unit stores the current value flowing through the filament as a reference value when the filament is normal. And a determination unit for determining the deterioration state of the filament by comparing the reference value with the current value flowing through the filament.

According to the gas chromatograph mass spectrometer according to the seventh item, the life can be estimated corresponding to each filament even when the initial current of the filament varies.

The configurations described in each embodiment of the present specification may be used in any combination.

The embodiments disclosed this time should be considered to be exemplary in all respects and not restrictive. The scope of the present invention is shown by the scope of claims rather than the description of the embodiment described above, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1 Gas chromatograph mass analyzer, 10 gas chromatograph section, 11 injector, 12 columns, 20 mass analyzer, 21,21A ion source, 22 ion lens, 23 filter, 24 detector, 26 vacuum pump, 31 controller, 32 inputs Unit, 33 Display, 211 Ionization chamber, 212 filament, 213 DC power supply circuit, 213A AC power supply circuit, 214 bias power supply circuit, 215 thermionic collector, 216 collector power supply, 217,219 Thermionic current meter, 218,218A Current detection , 222 ion outlet, 223 thermion inlet, 224 thermion outlet, 241 first switching element, 242 second switching element, 243 transformer, 244 primary side coil, 245 secondary side coil, 246 current supply circuit, 247 drive circuit, 251 current detection resistor, 254 A / D converter, 311 current monitoring unit, 312 warning processing unit, 321 CPU, 322 memory.

Claims (7)

Gas chromatograph section and
A mass spectrometer that analyzes the mass of molecules that have passed through the gas chromatograph section,
The gas chromatograph unit and the control device for controlling the mass spectrometer are provided.
The mass spectrometer includes a filament and
The control device is
A current monitoring unit that monitors the current flowing through the filament,
A gas chromatograph mass spectrometer including a warning processing unit that notifies a warning when the current value monitored by the current monitoring unit is lower than the determination value. The mass spectrometer is
A bias power supply circuit that applies a reference potential to the first end of the filament,
A DC power supply circuit that applies a DC current between the first end of the filament and the second end of the filament.
Including a current detector
The gas chromatograph mass spectrometer according to claim 1, wherein the current detection unit detects a current flowing through the filament by detecting a current flowing through the DC power supply circuit. The gas chromatograph mass spectrometer according to claim 2, wherein the current detection unit is composed of high withstand voltage electronic components. The mass spectrometer is
A bias power supply circuit that applies a reference potential to the first end of the filament,
An AC power supply circuit that applies an AC current between the first end of the filament and the second end of the filament.
Including a current detector
The gas chromatograph mass spectrometer according to claim 1, wherein the current detection unit detects a current flowing through the filament by detecting a current flowing through the AC power supply circuit. The AC power supply circuit
A transformer in which the first and second ends of the filament are connected to the first and second ends of the secondary coil, respectively.
It includes a current supply circuit that supplies a current to the primary coil of the transformer so that the direction of the magnetic flux passing through the inside of the secondary coil changes alternately.
The gas chromatograph mass spectrometer according to claim 4, wherein the current detection unit is configured to detect a current flowing through the current supply circuit. The primary side coil has an intermediate tap connected to the power node.
The current supply circuit
A first switching element connected between the first end of the primary coil and the voltage detection node,
A second switching element connected between the second end of the primary coil and the voltage detection node, and
A drive circuit that alternately conducts the first switching element and the second switching element, and
It includes a resistance element connected between the voltage detection node and the ground node.
The gas chromatograph mass spectrometer according to claim 5, wherein the current detection unit includes an A / D converter that detects a potential difference between the voltage detection node and the grounding node. The warning processing unit
A storage unit that stores the current value flowing through the filament as a reference value when the filament is normal,
The gas chromatograph mass spectrometer according to any one of claims 1 to 6, further comprising a determination unit for determining a deteriorated state of the filament by comparing the reference value with the current value flowing through the filament.

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