Mass spectrometer and method for correcting mass spectrometer

Abstract

A mass spectrometer (100) is provided with: an ion source (101) that ionizes a sample; a detection unit (105) that has a photomultiplier tube (105a) and analyzes the mass of the sample ionized by the ion source (101); a vacuum chamber (102) that connects the ion source (101) and the detection unit (105); a vacuum gauge (106) that measures the degree of vacuum inside the vacuum chamber (102); and a data analysis unit (112) and an analysis control unit (113) that corrects the setting of the photomultiplier tube (105a) using the electrons radiated from the vacuum gauge (106).

Description

Technical Field

[0001] The present invention relates to a mass spectrometer and a calibration method for a mass spectrometer. Background Art

[0002] Patent document 1 describes a mass analyzer comprising: a gas injection port suitable for supplying a sample gas to be ionized to an ionization region of the mass analyzer; a calibration unit suitable for supplying a calibration gas to be ionized to the ionization region; and an ionization unit suitable for ionizing the sample gas and / or calibration gas in the ionization region, wherein the calibration unit includes at least one evaporation source for generating the calibration gas by evaporating a raw material substance.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application No. 2022-553543 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] The mass spectrometer includes an ion source that ionizes compounds in a sample, a mass spectrometry unit such as a mass filter that separates ions from the compounds according to their mass-to-charge ratio (m / z), and a detector that detects the separated ions.

[0008] Patent document 1 describes a mass spectrometer having a vacuum chamber connecting an ion source and a mass spectrometer, wherein an ionization-type vacuum gauge for measuring the vacuum degree inside the vacuum chamber is provided, the vacuum gauge is operated at a timing when no measurement is performed in the mass spectrometer, and a detector of the mass spectrometer is calibrated using a calibration gas.

[0009] Thus, calibration of a detector in a mass spectrometer requires ionizing a sample and introducing it. However, since ionizing a sample is necessary for calibrating a detector, a technique that can perform calibration more efficiently is desired.

[0010] The present invention provides a mass spectrometer and a method for calibrating a mass spectrometer that can be calibrated more easily than before.

[0011] Means for solving problems

[0012] The present invention includes multiple means for solving the above-mentioned problems. For example, it comprises: an ion source that ionizes a sample; a mass analysis unit that has a photomultiplier tube and analyzes the mass of the sample ionized by the ion source; a vacuum chamber that connects the ion source and the mass analysis unit; a vacuum gauge that measures the vacuum level inside the vacuum chamber; and a calibration unit that uses electrons emitted from the vacuum gauge to calibrate the settings of the photomultiplier tube.

[0013] Effects of the Invention

[0014] According to the present invention, correction can be performed more easily than before. Other problems, structures, and effects than those described above will become clear from the following description of the embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a diagram showing the overall structure of a mass spectrometer.

[0016] Figure 2 This is a flow chart of the voltage adjustment of the photomultiplier tube.

[0017] Figure 3 This is a timing diagram for the voltage adjustment setting of the photomultiplier tube.

[0018] Figure 4 This is the timing diagram of the voltage adjustment of the photomultiplier tube.

[0019] Figure 5 This is a diagram showing an example of a display on a software GUI screen for adjusting the voltage of a photomultiplier tube. DETAILED DESCRIPTION

[0020] use Figures 1 to 5 In the drawings used in this specification, identical or corresponding components are denoted by identical or similar reference numerals, and overlapping descriptions of these components may be omitted.

[0021] First, use Figure 1 The overall structure of the mass spectrometer will be described. Figure 1 It is a diagram showing the overall structure of a mass spectrometer.

[0022] Figure 1 The mass spectrometer 100 shown includes an ion source 101 , a vacuum chamber 102 having an ion transport unit 103 , a mass separation unit 104 , and a detection unit 105 , a vacuum gauge 106 , an A / D converter 111 , a data analyzer 112 , an analysis control unit 113 , a display device 114 , and the like.

[0023] The ion source 101 is a part that ionizes a sample.

[0024] The vacuum chamber 102 is evacuated by a pump to transport the sample ionized by the ion source 101 to the detection unit 105 . An ion transport unit 103 , a mass separation unit 104 , a detection unit 105 , and a vacuum gauge 106 are arranged therein.

[0025] The ion transport unit 103 is a portion that transports ions ionized by the ion source 101 and introduced into the vacuum chamber 102 toward the mass separation unit 104 and the detection unit 105 on the subsequent side.

[0026] The mass separation unit 104 is a device such as a mass filter that separates compounds in the ionized sample according to their mass-to-charge ratio (m / z).

[0027] The detection unit 105 is a part that analyzes the mass of the sample by detecting only ions separated into predetermined masses in the mass separation unit 104 , and includes conversion dynodes (CD1 , CD2 ), a scintillator, a photomultiplier tube 105 a , and the like.

[0028] The vacuum gauge 106 is an ionization type vacuum gauge for measuring the vacuum degree inside the vacuum chamber 102 , and an example thereof may be a cold cathode ionization vacuum gauge (cold cathode measurement instrument).

[0029] The analysis control unit 113 is electrically connected to various mechanisms within the mass spectrometer 100 and controls their operations. In this embodiment, the electrons emitted from the vacuum gauge 106 are used to calibrate the settings of the photomultiplier tube 105 a .

[0030] The analysis control unit 113 can be composed of, for example, a computer having a display device 114 composed of a liquid crystal display, a memory composed of a hard disk memory or an external memory, an A / D conversion unit 111 that converts the detection signal from analog to digital, an interface, an input device such as a keyboard for inputting operation instructions, a data analysis unit 112, etc. It can also be composed of one computer and another computer, without any special limitation.

[0031] The data analysis unit 112 sends instructions to the analysis control unit 113 and other units to control the operation of each mechanism. Furthermore, the data analysis unit 112 receives A / D-converted data (photometric values) from the detection unit 105 via the A / D conversion unit 111. The data analysis unit 112 performs computations using the received data (photometric values). In other words, the data analysis unit 112 can control the various mechanisms of the detection unit 105 via the analysis control unit 113 and perform computations on the data.

[0032] Analysis control unit 113 controls the operation of each device based on various programs stored in the storage device. The control processing performed by analysis control unit 113 can be integrated into a single program, divided into multiple programs, or a combination thereof. Furthermore, a program may be partially or entirely implemented using dedicated hardware or modularized.

[0033] The display device 114 is a user interface such as a touch panel display, and receives information output to the user and various inputs from the user. In this embodiment, it displays a screen for setting conditions when performing calibration. The details will be described later.

[0034] The driving voltage of the photomultiplier tube 105a mounted in the detection unit 105 (hereinafter referred to as PMT voltage) and the offset voltage of the signal input to the A / D conversion unit 111 (hereinafter referred to as base voltage) can be adjusted by changing the settings of the A / D conversion unit 111 from the detection unit 105.

[0035] The optimal base voltage and PMT voltage for the mass spectrometer 100 and its photomultiplier tube 105a differ, requiring optimization during setup and component replacement after assembly. Therefore, parameter adjustment of the A / D converter 111 is primarily performed during assembly. Furthermore, this adjustment is also necessary in the event of a malfunction during actual use, such as after component replacement due to a malfunction of the A / D converter 111 or the photomultiplier tube 105a.

[0036] In the mass spectrometer 100 , PMT voltage adjustment has conventionally been performed by introducing a sample consisting mainly of positive ions. However, this requires time and effort to introduce the sample. Therefore, in this embodiment, the PMT voltage adjustment conventionally performed with ions is assumed to be performed using electrons.

[0037] Next, use Figures 2 to 5 An example of the flow of adjusting the PMT voltage and the operation of the device will be described. Figure 2 Flowchart showing PMT voltage adjustment. Figure 3 This is the timing diagram for voltage adjustment setting. Figure 4 This is the timing diagram of voltage adjustment. Figure 5 This is a diagram showing a display example of a software GUI screen for voltage adjustment.

[0038] First, use Figure 2 In this embodiment, the data analysis unit 112 and the analysis control unit 113 perform calibration at a timing when the analysis by the detection unit 105 is not being performed. However, the timing of voltage adjustment is not limited to this timing.

[0039] First, when the PMT voltage adjustment process is started (S101), the analysis control unit 113 executes the PMT voltage adjustment setting (S102). The PMT voltage adjustment setting is a pre-action of the PMT voltage adjustment, and is an action of turning on various power supplies. For example, it can be recognized that the user selects / presses the Figure 5 The voltage adjustment setting button 114a1 in the PMT voltage adjustment setting screen 114a displayed on the display device 114 is executed.

[0040] Next, the analysis control unit 113 performs the adjustment of the PMT voltage (S103). Figure 5 The operation is executed when the PMT voltage adjustment button 114a2 is clicked on the PMT voltage adjustment setting screen 114a displayed on the display device 114 shown.

[0041] At this time, in this embodiment, it is preferable to perform calibration using electrons emitted from the vacuum gauge 106 , and therefore the data analysis unit 112 and the analysis control unit 113 preferably set the detection unit 105 during calibration to a setting for measuring negative ions.

[0042] Specifically, when the PMT voltage adjustment button 114a2 is pressed, the analysis control unit 113 controls the detection unit 105. Figure 3 The sequence of the timing diagram shown specifies switching the dynode (CD1, CD2), scintillator, and PMT voltages.

[0043] For example, various parameters of the adjustment software include the following: "target value", "allowable error (allowable value)", "Acoff (step value of software adjustment)", "maximum number of trials (repetition upper limit)", etc.

[0044] like Figure 3 As shown, when the user presses the PMT voltage adjustment button 114a2, the analysis control unit 113 sets the voltage of the conversion dynode, scintillator, and photomultiplier tube 105a to a specified voltage to satisfy the measurement conditions, turning each electrode "ON" to introduce electrons into the detection unit 105. Next, the vacuum gauge 106 is turned on to start electron emission.

[0045] Therefore, if Figure 4 As shown in FIG. 1 , the analysis control unit 113 instructs the detection unit 105 to start measurement.

[0046] After reading the software action parameters set on the screen sent from the analysis control unit 113, the detection unit 105 repeatedly performs the measurement processing flow, average area value calculation, and target value comparison actions until the target value of the set parameters is reached within ± the allowable error, or the number of repetitions = the maximum number of trials.

[0047] The emitted electrons pass through the conversion dynodes (CD1, CD2) and the scintillator, according to the parameters set for negative ion detection in the detection unit 105, and are detected as counts (analog data) in the photomultiplier tube 105a. The detected data is converted from analog to digital data by the A / D converter 111 and then read into the data analysis unit 112. A pulse width histogram is created, and the average pulse area is calculated and compared with the target value for determination.

[0048] Here, the average area value can be calculated using the following formula (1).

[0049] Average value of ion amount map = Σ(frequency × pulse area) / number of pulses…(1)

[0050] In addition, the average value of the obtained ion quantity diagram is compared with the target value. In the target value comparison, if the calculation result obtained by the average value calculation meets the target value ± allowable error (target value - allowable error ≤ average value ≤ target value + allowable error), the repeated action is stopped and "OK" is displayed in the PMT voltage adjustment setting screen 114a.

[0051] In contrast, even if the maximum number of trials set by the software action parameter maximum trial number setting button 114a4 is reached, if the target value ± allowable error (target value - allowable error ≤ average value ≤ target value + allowable error) is not met, the repeated action is stopped and "Error" is displayed in the PMT voltage adjustment setting screen 114a.

[0052] Then, if Figures 2 to 4 As shown, the analysis control unit 113 requires the user to determine whether there is no problem in the determination of the PMT voltage (S104). Figure 5 The display device 114 shown displays the measurement results and / or judgment results, and can request a judgment from the user.

[0053] For example, when the repetitive operation is completed under the above-mentioned conditions, the pass / fail determination result is output to the display device 114. The following is divided into cases of determination results.

[0054] "OK": Validate the post-adjustment processing button 114a3, display the adjusted PMT voltage on the display device 114, and update Figure 5 The PMT voltage in the voltage state box in the PMT voltage button 114a8 is displayed, and the analysis control unit 113 designates the detection unit 105 (S106 described later).

[0055] "Error": The post-adjustment processing button 114a3 remains in an inoperable state, and a notification "Please perform PMT voltage adjustment again" is given (S105 described later).

[0056] If it is determined in S104 that there is a problem, the process proceeds to S105 , and the analysis control unit 113 adjusts the software operating parameters (PMT voltage) based on the input by the user ( S105 ).

[0057] For example, it is possible to Figure 5 The settings of the conversion dynode (CD1, CD2) voltage, scintillator voltage, and PMT voltage are changed by pressing the CD1 voltage button 114a5, CD2 voltage button 114a6, scintillator voltage button 114a7, and PMT voltage button 114a8 on the PMT voltage adjustment setting screen 114a displayed on the display device 114. The setting values ​​are changed based on the input values. The process then returns to step S103.

[0058] On the other hand, when it is determined in S104 that there is no problem, the process proceeds to S106 , and the analysis control unit 113 executes the PMT voltage post-adjustment process ( S106 ).

[0059] For example, it is possible to recognize that the user selects / presses Figure 5 The process is executed by clicking the post-adjustment processing button 114a3 in the PMT voltage adjustment setting screen 114a displayed on the display device 114 shown.

[0060] Here, the analysis control unit 113 desirably disables the post-adjustment processing button 114a3 except when the voltage adjustment setting button 114a1 and the PMT voltage adjustment button 114a2 are "OK", that is, when both the PMT voltage adjustment setting and the PMT voltage adjustment are "OK".

[0061] Thereafter, the analysis control unit 113 completes the PMT voltage adjustment ( S107 ).

[0062] Next, the effects of this embodiment will be described.

[0063] The mass spectrometer 100 includes an ion source 101 for ionizing a sample; a detection unit 105 having a photomultiplier tube 105a for analyzing the mass of the sample ionized by the ion source 101; a vacuum chamber 102 for connecting the ion source 101 with the detection unit 105; a vacuum gauge 106 for measuring the vacuum level inside the vacuum chamber 102; and a data analysis unit 112 and an analysis control unit 113 for calibrating the settings of the photomultiplier tube 105a using electrons emitted from the vacuum gauge 106.

[0064] Therefore, the vacuum gauge 106 originally provided in the mass spectrometer 100 can be used, and thus the calibration operation can be performed without separately introducing a sample, thereby making the calibration easier than before.

[0065] Furthermore, since the vacuum gauge 106 is of an ionization type, it can reliably and stably emit stable electrons, and thus the calibration operation can be performed more smoothly.

[0066] Furthermore, the data analysis unit 112 and the analysis control unit 113 can reliably perform the calibration work without being hindered by other work by executing the calibration at a timing when the analysis in the detection unit 105 is not being performed.

[0067] Furthermore, the data analysis unit 112 and the analysis control unit 113 can use the existing settings by setting the detection unit 105 during calibration as the settings for negative ion measurement, thereby facilitating design and the like.

[0068] Furthermore, by further providing the display device 114 that displays a screen for setting conditions when performing calibration, the user can easily execute and grasp changes in setting conditions, the status of calibration, and the like.

[0069] <Other>

[0070] The present invention is not limited to the above-described embodiments, and various modifications and applications are possible. The above-described embodiments are examples described in detail to facilitate understanding of the present invention, and are not necessarily limited to those having all the described configurations.

[0071] Description of Reference Numerals

[0072] 100 mass analysis device

[0073] 101 ion source

[0074] 102 vacuum chamber

[0075] 103 Ion Transport Unit

[0076] 104 mass separation unit

[0077] 105 Inspection Department (Quality Analysis Department)

[0078] 105a photomultiplier tube

[0079] 106 vacuum gauge

[0080] 111A / D conversion unit

[0081] 112 Data Analysis Department (Correction Department)

[0082] 113 Analysis and Control Unit (Calibration Unit)

[0083] 114 display device

[0084] 114a PMT voltage adjustment setting screen

[0085] 114a1 voltage adjustment setting button

[0086] 114a2 PMT voltage adjustment button

[0087] 114a3 Adjust post-processing button

[0088] 114a4 software action parameter maximum trial times setting button

[0089] 114a5 CD1 voltage button

[0090] 114a6 CD2 voltage button

[0091] 114a7 scintillator voltage button

[0092] 114a8 PMT voltage button.

Claims

1. A mass analysis device, characterized in that The mass analysis device comprises: an ion source that ionizes the sample; a mass analysis unit having a photomultiplier tube for analyzing the mass of the sample ionized by the ion source; a vacuum chamber connecting the ion source and the mass analysis unit; a vacuum gauge for measuring the vacuum degree inside the vacuum chamber; as well as A calibration unit calibrates the setting of the photomultiplier tube using the electrons emitted from the vacuum gauge.

2. The mass spectrometer according to claim 1, wherein The vacuum gauge is of ionization type.

3. The mass spectrometer according to claim 1, wherein The calibration unit performs calibration at a timing when the mass spectrometer is not performing analysis.

4. The mass spectrometer according to claim 1, wherein The calibration unit sets the settings of the mass spectrometer during the calibration as settings for negative ion measurement.

5. The mass spectrometer according to claim 1, wherein The mass spectrometer further includes a display device that displays a screen for setting conditions when performing the calibration.

6. A method for calibrating a mass spectrometer, the mass spectrometer comprising: an ion source for ionizing a sample; a mass spectrometer having a photomultiplier tube for analyzing the mass of the sample ionized by the ion source; a vacuum chamber for communicating the ion source with the mass spectrometer; and a vacuum gauge for measuring the vacuum level inside the vacuum chamber. It is characterized in that The electrons emitted from the vacuum gauge are used to calibrate the settings of the photomultiplier tube.

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