Mass analysis device and mass analysis method

Abstract

In a mass spectrometer, due to the accumulation of inclusions inside the frame, the withstand voltage is reduced, and discharge occurs in the ion source, etc., which sometimes makes it impossible to perform normal measurements. The results of abnormal measurements based on discharge cannot be distinguished from measurement abnormalities caused by blockage of the tube between the pre-processing unit and the needle, so it takes time to determine the abnormal location, which reduces the maintainability. As a means for this, a return current detection unit connected in series between the ion source power supply that applies voltage to the needle and the frame and a return current detection unit connected in series between the opposing electrode power supply that applies voltage to the opposing electrode and the frame are provided. The occurrence of discharge and the location where the discharge occurs are detected by comparing the current measured by the return current detection unit with a predetermined threshold value.

Description

Technical Field

[0001] The present invention relates to a mass spectrometer and a mass spectrometry method, and in particular to a mass spectrometer comprising a needle, an opposing electrode opposed to the needle, an ion source power supply for applying voltage to the needle, and an opposing electrode power supply for applying voltage to the opposing electrode, and a mass spectrometry method using the mass spectrometer. Background Art

[0002] As a component constituting a mass spectrometer, for example, an ion source is known that vaporizes a sample to be analyzed injected from a pre-processing unit and applies a high electric field to the vaporized sample to ionize the vaporized sample.

[0003] Patent document 1 (International Publication No. 03 / 065406) ​​describes the following: In a mass spectrometer, when a sample to be analyzed is injected from a chromatograph serving as a pre-processing unit into an ion source, a current value of ions having a specific mass is measured, and when the current value is lower than a threshold value, it is determined that nozzle clogging has occurred, and the operator is notified of the occurrence of measurement abnormality in the device.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 03 / 065406 Summary of the invention

[0007] Problems to be solved by the invention

[0008] As a cause of measurement abnormalities that occur with high frequency in the measurement of the mass spectrometer, in addition to the blockage (noise blockage) in the tube leading from the pre-treatment unit to the needle, there is also discharge in the ion source. Generally, an upper limit is set for the voltage that can be applied to the ion source. In a normal mass spectrometer, discharge will not occur as long as it is used below this voltage. However, when the sample of the analysis object is ionized using the ion source, the unionized sample accumulates inside the ion source as inclusions, so the withstand voltage inside the ion source is reduced and discharge may occur. As a result, normal measurement cannot be performed. At this time, it is impossible to distinguish the results of abnormal measurement based on discharge from abnormalities such as blockage of the tube of the pre-treatment unit, so there is a problem that it takes time to determine the abnormal part and eliminate the cause of the abnormality. This leads to a decrease in the maintainability of the mass spectrometer and a waste of samples.

[0009] Other issues and novel features will become apparent from the present specification and accompanying drawings.

[0010] Means for solving problems

[0011] The outline of a typical embodiment among the embodiments disclosed in the present application will be briefly described as follows.

[0012] As one embodiment, a mass spectrometer is provided with return current detection units connected in series between an ion source power supply and a frame, and between an opposing electrode power supply and a frame, and detects the occurrence of discharge and the location of discharge by comparing the current measured by these return current detection units with a threshold value.

[0013] Effects of the Invention

[0014] According to a representative embodiment, the performance of a mass spectrometer can be improved. In particular, it is easy to identify the discharge occurrence site when an abnormal discharge occurs during measurement, thereby reducing sample waste, selecting / obtaining effective measurement data, and improving the maintainability of the mass spectrometer. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the mass spectrometer according to the first embodiment.

[0016] Figure 2 This is a connection diagram of a circuit for detecting a discharge current of an ion source constituting the mass spectrometer according to the first embodiment.

[0017] Figure 3 It is a graph showing the characteristics of discharge voltage and current of the mass spectrometer according to the second embodiment.

[0018] Figure 4 This is a signal diagram showing the setting of a threshold value for determining abnormal discharge in the mass spectrometer according to the second embodiment.

[0019] Figure 5 This is a signal diagram showing the setting of a threshold value for determining abnormal discharge in the mass spectrometer according to the second embodiment.

[0020] Figure 6 This is a signal diagram showing the return current waveform of the ion source power supply during the measurement of positive and negative ions.

[0021] Figure 7 This is a signal diagram for explaining a method of shielding an inrush current during positive-negative switching measurement in the mass spectrometer of the third embodiment.

[0022] Figure 8 This is a connection diagram showing the paths of the respective rush currents of the ion source power supply and the counter electrode power supply constituting the mass spectrometer of the fourth embodiment.

[0023] Fig. 9 This is a connection diagram showing the respective paths of the discharge current and the surge current of the counter electrode power supply constituting the mass spectrometer of the fourth embodiment.

[0024] Fig.10 It is a signal diagram showing the return current waveform of the ion source power supply of the mass spectrometer according to the fourth embodiment.

[0025] Fig.11 This is a signal diagram showing a return current waveform of a counter electrode power supply of a mass spectrometer according to a fourth embodiment.

[0026] Fig.12 This is the operation flow of the mass spectrometer according to the first embodiment.

[0027] Fig.13 This is a schematic diagram showing a user interface screen of the mass spectrometer according to the first embodiment.

[0028] Fig.14 This is a schematic diagram of a mass spectrometer according to a fifth embodiment.

[0029] Fig.15 It is a schematic diagram showing a mass spectrometer of a comparative example. DETAILED DESCRIPTION

[0030] Hereinafter, the embodiments of the present invention will be described in detail based on the accompanying drawings. In addition, in all the drawings used to illustrate the embodiments, the same reference numerals are used for components having the same functions, and their repeated descriptions are omitted. In addition, in the embodiments, the description of the same or identical parts is not repeated in principle except when particularly necessary.

[0031] (Implementation Method 1)

[0032] The following describes a method for detecting measurement abnormalities, the presence or absence of discharge, and the location where discharge occurs based on the detection results of the current detected by the return current detection unit when measuring a sample of the analysis object and the amount of ions measured by the mass spectrometer, using a mass spectrometer equipped with an ion source power supply having a return current detection unit and an opposing electrode power supply.

[0033] <Structure of this embodiment>

[0034] Figure 1 A schematic diagram showing a mass spectrometer according to the present embodiment. Figure 1 1 is a diagram for explaining a unit for detecting a discharge current of an ion source in a mass spectrometer. The mass spectrometer includes a frame (device frame) 1 which is a container having conductivity and functions as a ground (frame ground). In addition, the mass spectrometer includes an ion source 10, a collection unit 11, a separation unit 12, a detector 13, an ion detector 7, and a control unit 2.

[0035] The ion source 10, the collecting section 11, the separating section 12 and the detector 13 are arranged in the frame 1. The ion source 10 is a part that ionizes the sample of the analysis object injected from the pre-processing section 4. The ionized sample 9 generated by the ion source 10 is collected by the collecting section 11. That is, the collecting section 11 is a part that collects the ionized sample by applying a voltage to the electrode 9a provided in the collecting section 11. The separating section 12 is a part that filters the ionized sample 9 collected by the collecting section 11 according to the mass-to-charge ratio, so that only the ionized sample 9 of the detection object passes. This filtering is performed by applying a voltage to the electrode 9b provided in the separating section 12. The detector 13 is a device that outputs an electrical signal corresponding to the amount of the ionized sample 9 passing through the separating section 12. The ion detector 7 is a device that obtains the amount of ions based on the electrical signal output from the detector 13. The control section 2 is a device that displays the detection result of the ion amount on a display (display section). The pre-processing section 4 is a device that sends a sample (inspection object) such as human blood or urine into a mass spectrometer.

[0036] The detector 13 comprises: a conversion dynode (electrode) 9c, which collides with the ionized sample 9 passing through the separation section 12 to release the electron 5 from the ionized sample 9; and an ion-to-electric conversion section 6, which outputs an electrical signal corresponding to the amount of the electron 5 to the ion detector 7 when the electron 5 is incident.

[0037] The ion source 10 includes: a needle 3 that ionizes a sample of an analysis object injected from a pretreatment unit 4; an ion source power supply 20 that applies a voltage to the needle 3 for ionizing the sample; an opposing electrode 19 that generates an electric field for introducing the ionized sample to a collection unit 11; and an opposing electrode power supply 21 that applies a voltage to the opposing electrode 19. The needle 3 and the opposing electrode 19 are disposed in a frame 1 separately from each other. The pretreatment unit 4 is connected to the needle 3 via a tube. In addition, the opposing electrode 19 is an electrode that is opposed to the needle 3. Regarding the opposing electrode 19, it is described here as "opposing", but it is not necessary for the surface of the needle 3 to be opposite to the surface of the opposing electrode 19 in a state parallel to each other, and it is not necessary for the opposing electrode 19 to be composed of a plurality of electrodes, and the surfaces of these electrodes to be opposite to each other in a state parallel to each other.

[0038] The ion source power supply 20 and the opposing electrode power supply 21 have a first terminal, a second terminal and a third terminal, respectively. The first terminal (output terminal) of the ion source power supply 20 is electrically connected to the needle 3. The second terminal (ground wire) of the ion source power supply 20 is electrically connected to the frame 1. The third terminal of the ion source power supply 20 is electrically connected to the control unit 2. The first terminal (output terminal) of the opposing electrode power supply 21 is electrically connected to the opposing electrode 19. The second terminal (ground wire) of the opposing electrode power supply 21 is electrically connected to the frame 1. The third terminal of the opposing electrode power supply 21 is electrically connected to the control unit 2. However, in the ion source power supply 20, the third terminal is electrically insulated from the first terminal and the second terminal. Similarly, in the opposing electrode power supply 21, the third terminal is electrically insulated from the first terminal and the second terminal.

[0039] The ion source power supply 20 has a return current detector (ammeter) 1a capable of detecting output current based on the return current returned via the frame 1. The counter electrode power supply 21 has a return current detector (ammeter) 1b capable of detecting output current based on the return current returned via the frame 1.

[0040] The return current detection part 1a is connected in series between the ion source power supply 20 and the frame 1. That is, the second terminal of the ion source power supply 20 is electrically connected to the return current detection part 1a, and the return current detection part 1a is electrically connected to the frame 1. In other words, the ion source power supply 20 is electrically connected to the frame 1 via the return current detection part 1a. Similarly, the return current detection part 1b is connected in series between the opposing electrode power supply 21 and the frame 1. That is, the second terminal of the opposing electrode power supply 21 is electrically connected to the return current detection part 1b, and the return current detection part 1b is electrically connected to the frame 1. In other words, the opposing electrode power supply 21 is electrically connected to the frame 1 via the return current detection part 1b.

[0041] The return current detection units 1a and 1b have means for detecting the amount of current passing therethrough and transmitting the detected amount of current to the control unit 2. For example, the return current detection units have a current detection accuracy of about nA to several tens of nA and can detect a current in the range of about several tens of μA.

[0042] The unit that sends the current detected by the return current detection units 1a and 1b is electrically insulated from the control unit 2 as the sending destination. In other words, the return current detection units 1a and 1b, the ion source power supply 20, and the opposing electrode power supply 21 are insulated from the control unit 2. In addition, a part of the path for sending the above-mentioned current from the return current detection units 1a and 1b to the control unit 2 is insulated. This is because if the return current detection units 1a and 1b, the ion source power supply 20, and the opposing electrode power supply 21 are connected to the control unit 2, it is difficult to accurately detect the current in the return current detection units 1a and 1b. By insulating as described above, the current detection accuracy in the return current detection units 1a and 1b can be improved. As a unit that sends the current from the ion source power supply 20 and the opposing electrode power supply 21 to the control unit 2 in an electrically insulated state, for example, optical communication can be used, and the optical communication uses a photodiode used in vehicle-mounted communication.

[0043] The control unit 2 has a function of displaying the detection result of the ion amount sent from the ion detector 7 to the operator (device operator). In addition, the control unit 2 has the following functions: receiving the current amount sent from the return current detection unit 1a, 1b, comparing the current amount with the preset threshold value T1, T2 to determine whether the current amount is normal or abnormal, and displaying the judgment result. In addition, the control unit 2 has a function of controlling the overall measurement of mass analysis. In addition, as Figure 1 As shown, the control unit 2 may have a function of displaying the amount of current (current signals A, B) sent from the return current detection units 1a, 1b. The operator operates the mass spectrometer through the control unit 2. Figure 1 The horizontal axis of the signal graph showing the detection result of the ion amount and the current signal A and B respectively represents time and the vertical axis represents the current amount. The control unit 2 is constituted by, for example, a personal computer and a display.

[0044] The threshold value to be compared with the current amount sent from the return current detection unit is set based on the current amount flowing when the ion source 10 is discharged. For example, the ion source 10 is discharged in advance, and the current amount flowing when the discharge starts is stored in the control unit 2 as a threshold value. In addition, when it is desired to detect an abnormality before starting the discharge, a value slightly lower than the current amount at the start of the discharge can also be stored as a threshold value. In addition, the threshold value T1 to be compared with the current amount sent from the return current detection unit 1a and the threshold value T2 to be compared with the current amount sent from the return current detection unit 1b can also be different values.

[0045] Next, use Figure 2 The types of discharge of the ion source 10 and the path of the discharge current will be described.

[0046] Figure 2The wiring diagram of the circuit for detecting the discharge current in the ion source 10 constituting the mass spectrometer of the present embodiment is shown. When the mass spectrometer operates normally, no discharge occurs in the ion source 10. However, due to the accumulation of inclusions in the mass spectrometer, etc., abnormal discharge may occur in the mass spectrometer. Figure 2 In FIG. 1 , a path along which a current due to abnormal discharge flows is indicated by a dotted line.

[0047] There are two types of discharges generated in the ion source 10, namely, discharge 2b from the needle 3 to the opposing electrode 19 and discharge 2a from the needle 3 to a portion other than the opposing electrode 19 that is electrically connected to the frame 1. The abnormal discharge current (discharge current) 3b that flows due to the discharge 2b passes through the opposing electrode 19 and the opposing electrode power supply 21 in sequence, passes through the return current detection portion 1b, and after passing through the return current detection portion 1a, returns to the ion source power supply 20 that is a current output source. The abnormal discharge current (discharge current) 3a that flows due to the discharge 2a passes through the frame 1 and the return current detection portion 1a, and then returns to the ion source power supply 20 that is a current output source.

[0048] Therefore, the return current detection unit 1a detects the currents 3a and 3b of both discharges 2a and 2b, and the return current detection unit 1b detects only the current 3b of the discharge 2b. Thus, firstly, the return current detection unit 1a can be used to detect whether the ion source 10 has abnormal discharge. In addition, based on the measurement result of the return current detection unit 1b, it can be determined in which path the current flowing due to abnormal discharge flows, the path of the current 3a or the path of the current 3b. That is, it is possible to determine whether the ion source 10 has discharge and the location where the discharge occurs.

[0049] At this time, the control unit 2 sets the absolute value of the current measured by the return current detection unit 1a to the threshold value T1 (see Figure 1 ) and the absolute value of the current measured by the return current detection unit 1b is less than the threshold value T2 (refer to Figure 1 ), the control unit 2 determines that discharge 2a has occurred. In addition, when the absolute value of the current measured by the return current detection unit 1a is greater than the threshold value T1, and the absolute value of the current measured by the return current detection unit 1b is greater than the threshold value T2, the control unit 2 determines that discharge 2b has occurred. In this way, the control unit determines whether discharge 2a exists between the needle 3 and the components of the ion source other than the opposing electrode 19, and whether discharge 2b exists between the needle 3 and the opposing electrode 19, based on the currents respectively measured by the return current detection units 1a and 1b.

[0050] Figure 1The figure shows together a current signal A indicating the amount of current sent by the return current detection unit 1a, a current signal B indicating the amount of current sent by the return current detection unit 1b, and a detection result of the amount of ions sent by the ion detector 7. The three waveforms are divided into a normal waveform region 1N where no abnormal discharge occurs in the ion source 10, a discharge waveform region 2X where discharge 2b occurs, and a discharge waveform region 1X where discharge 2a occurs.

[0051] The operator of the device only monitors the detection result of the ion quantity during the measurement, and can obtain the normal ion quantity result when no abnormal discharge occurs in the ion source 10. In the case where discharge occurs in the ion source 10 and the current amount of the return current detection unit 1a exceeds the threshold value T1, the control unit 2 notifies the operator of the occurrence of abnormal discharge as an error or warning through display, lighting or sound, and also displays the discharge occurrence location based on the magnitude relationship between the current amount of the return current detection unit 1b and the threshold value T2. For example, when a current such as the waveform area 1X is detected, it can be determined that the discharge occurs on the path of the discharge 2a between the needle 3 and the frame 1. In addition, when a current such as the waveform area 2X is detected, it can be determined that the discharge occurs on the path of the discharge 2b between the needle 3 and the opposing electrode 19.

[0052] The operator of the device can interrupt the measurement and eliminate the cause of the discharge by cleaning the discharge generating part (ion source 10) determined as described above based on the displayed information. The interruption of the measurement (stopping of the mass analysis process) can be performed by the operator of the device, or it can be performed automatically by the control unit 2 at the time when an abnormal current such as the waveform area 1X or 2X is detected.

[0053] Fig.12 The operation flow of the mass spectrometer of the present embodiment is shown. This operation flow is an example in which the discharge detection step of the present embodiment described above is added to the general mass spectrometry operation flow.

[0054] First, in the device startup process of step S1, the operation of the mass spectrometer is set based on mass spectrometry start information input from the operator via the control unit 2. The start information includes, for example, the mass spectrometry operation mode, voltages of various mounted power supplies, and measurement end conditions (e.g., measurement time).

[0055] The waiting for the start of measurement in step S2 is a process performed while waiting until the operator inputs a measurement start instruction via the control unit 2. This process is, for example, the reading of periodic device status information.

[0056] Step S3 is a step for determining whether a measurement start instruction has been input. When the operator inputs a measurement start instruction via the control unit 2, the process proceeds to step S4. When no measurement start instruction has been input, the process proceeds to step S2.

[0057] In the ion amount data acquisition in step S4 , a process is performed to take the detection data of the ion amount transmitted from the ion detector 7 into the control unit 2 .

[0058] In the mass analysis process of step S5, the ion quantity data acquired in step S4 is subjected to calculation processing based on information such as the operation mode set in step S1. The operation mode is, for example, a scan mode of mass analysis or a SIM (Selected Ion Monitoring) mode.

[0059] The mass analysis result display in step S6 is a process of displaying the calculation processing result in step S5 on the screen of the control unit 2. The displayed result is, for example, a mass spectrum or a chromatogram.

[0060] The device status reading in step S7 is a process of reading device status information that can determine whether the state of the mass spectrometer is normal or abnormal from various sensors, detectors, etc. mounted on the mass spectrometer. Here, the current amount obtained by the return current detection unit of this embodiment is sent to the control unit 2. In addition, other device status information is, for example, error / warning information of various power supplies or vacuum pump units, or temperature information of heaters, etc.

[0061] Step S8 is an error / warning determination of the device status information. If there is an error or warning in the device status information read in step S7, the process proceeds to step S9. If there is no error or warning, the process proceeds to step S12.

[0062] Step S9 is to determine whether there is discharge. Based on the result of comparing the absolute value of the current amount sent from the return current detection unit of this embodiment included in the device status information read in step S7 with the threshold value, if the control unit 2 determines that discharge has occurred, the process moves to step S10. If the control unit 2 determines that no discharge has occurred, the process moves to step S11.

[0063] The discharge response process of step S10 is a process performed when a discharge occurs in the ion source 10. For example, in order to notify the operator of a warning of the occurrence of a discharge from the control unit 2, to quickly stop the measurement operation of the mass spectrometer, to set the condition information of the end of the measurement to a true value, or to determine the discharge location based on the current amount sent by the return current detection unit 1b and notify the operator, etc.

[0064] The other abnormality processing in step S11 is processing for abnormal conditions other than discharge, for example, warning notification corresponding to operation errors of various power supplies or vacuum pumps, or setting a true value for a measurement end condition.

[0065] Step S12 is a determination of the end of the measurement operation. When a measurement end instruction is input by the operator, when the measurement time ends, or when the measurement end condition is set to a true value in step S10 or S11, the measurement operation of the mass spectrometer ends.

[0066] Fig.13 1 is a schematic diagram showing an example of a user interface screen of the mass spectrometer according to the present embodiment. The user interface screen 100 is displayed on the display of the control unit 2 and is composed of an operation area 110 and a display area 111 .

[0067] The operation area 110 has an apparatus start button 101 for starting the apparatus and a setting button 102 for inputting the start information of the mass analysis. The operator executes step S1 by pressing the apparatus start button 101 and the setting button 102. In addition, the operation area 110 has a measurement start button 103 and a measurement end button 104. The operator executes step S3 by pressing the measurement start button 103 and executes step S12 by pressing the measurement end button 104.

[0068] The display area 111 includes a measurement result area 105 and an apparatus status display area 106 . The measurement result area 105 displays the detection result of the ion amount as the execution result of step S6 , and the apparatus status display area 106 displays the execution result of step S7 .

[0069] The device status display area 106 has a device status result 107 that displays the comprehensive result of monitoring the device status. Regarding the display content of the device status result 107, for example, if there is even one error or warning in the device status reading result executed in step S7, it is displayed as abnormal, and if there is no error or warning, it is displayed as normal.

[0070] In addition, the device status display area 106 has a detailed status result 109. The detailed status result 109, for example, displays the device status reading result executed in step S7 separately. The displayed result is, for example, the presence or absence of abnormalities in the discharge, temperature, vacuum degree, etc. of the ion source 10. The detailed status result 109 may usually not be displayed on the user interface screen 100, but may be displayed in another screen according to the operator's instructions so that the operator can confirm as needed. When the control unit 2 detects discharge 2a or 2b (see Figure 1 ) occurs, the control unit 2 displays the location where the discharge occurred in the device status display area 106.

[0071] <Effects of the present embodiment>

[0072] Here, in order to illustrate the effect of this embodiment, a mass spectrometer of a comparative example is shown. Fig.15 . Fig.15 The structure of the mass spectrometer of the comparative example shown is Figure 1 The mass spectrometer shown is different in that no ammeter is provided between the second terminal of each of the ion source power supply 20 and the counter electrode power supply 21 and the frame 1, and the ion source power supply 20 and the counter electrode power supply 21 do not have a third terminal. Since the ammeter is not provided, the current amount of the abnormal current is not sent to the control unit 2.

[0073] In the mass spectrometer, it is believed that inclusions (garbage) accumulate inside due to continued use. A normal mass spectrometer without accumulation of inclusions has a voltage resistance performance that does not cause discharge in the ion source. However, when the accumulation of inclusions progresses, discharge will be caused, for example, between the needle and the frame, or between the needle and the opposing electrode. If such a discharge occurs, the efficiency of ionization of the sample, which is the original function of the needle, is reduced, and it is difficult to perform mass analysis normally.

[0074] During the measurement, the operator of the mass spectrometer of the comparative example only monitors the detection result of the ion amount. When an abnormal discharge occurs, it is considered that an abnormality such as a decrease in the ion amount as the detection result is confirmed. In this case, the operator interrupts the measurement to eliminate the cause of the discharge. However, since the discharge site cannot be immediately determined, there is a problem that it takes time to check each part inside the mass spectrometer.

[0075] In addition, as one of the causes of the abnormality of the monitored detection result, i.e., the decrease in the amount of ions, the discharge in the mass spectrometer can be considered, but in addition, other causes other than the discharge, such as the blockage in the tube between the pre-processing unit and the needle, can also be considered. In the mass spectrometer of the comparative example, since only the detection result of the amount of ions is monitored to determine whether there is an abnormality, it is impossible to determine whether the abnormal cause is caused by the discharge or other causes such as the blockage in the tube. Therefore, there is a problem that it takes time to check whether the abnormal cause is other than the discharge.

[0076] Furthermore, when measurement abnormality due to discharge occurs, the operator may fail to notice the abnormality and acquire invalid ion amount measurement data.

[0077] In addition, since it takes time from the time when abnormal discharge occurs to the time when the abnormality is recognized and the measurement is interrupted, there is a problem of wasting samples during this period. For example, in the case where the sample is human blood, the amount of sample prepared in advance is small, and in such a case, it is particularly necessary to minimize the waste of samples.

[0078] In contrast, in this embodiment, if Figure 1 As shown, a return current detection unit 1a for detecting the current 3a flowing through the frame 1 due to abnormal discharge, and a return current detection unit 1b for detecting the current 3b flowing through the frame 1 due to abnormal discharge are provided. Thus, the occurrence of abnormal discharge can be detected instantly. In addition, since the return current detection units 1a and 1b are respectively provided in the ion source power supply 20 and the opposing electrode power supply 21, it is possible to determine the discharge occurrence location in the ion source 10. In addition, it is known that the cause of the abnormality in the detection result of the ion quantity is not the blockage of the tube, etc. but the discharge, so the process of checking whether the abnormal cause is a cause other than the discharge can be omitted. Thus, the process of checking various parts inside and outside the mass spectrometer in order to determine the discharge occurrence location can be omitted, so that the mass analysis using the mass spectrometer can be performed in a short time and at a low cost. Therefore, the performance of the mass spectrometer can be improved.

[0079] In addition, the control unit 2 or the operator can immediately interrupt the measurement, so the waste of the sample can be suppressed. In particular, if the measurement is terminated by the control unit 2, the waste of the sample can be suppressed to a minimum. Therefore, the performance of the mass spectrometer can be improved.

[0080] According to the above, the occurrence of measurement abnormality caused by discharge can be instantly identified, so the measurement can be interrupted in a short time to reduce the waste of samples. In addition, the measurement data at this time is deleted as invalid data due to abnormality, which can ensure the soundness of the analysis results. In addition, since the discharge location is also known in a short time, the maintainability can be improved.

[0081] The mass spectrometer of this embodiment can Fig.15 The mass spectrometer of the comparative example shown is realized by simply providing an ammeter between the power supply and the frame, and the above-mentioned effect can be obtained by monitoring the amount of current measured by the ammeter.

[0082] (Implementation Method 2)

[0083] In the measurement of the mass spectrometer, the polarity of the voltage applied to the needle and the counter electrode of the ion source is different depending on the type of the analysis object or the analysis method. When the sample of the analysis object is positively ionized, a positive voltage is applied to the needle and the counter electrode, and when the sample is negatively ionized, a negative voltage is applied to the needle and the counter electrode. The following describes a method for setting a threshold value for judging whether there is a discharge matching the polarity of the voltage applied to the needle and the counter electrode in the mass spectrometer described in the above-mentioned embodiment 1.

[0084] Figure 3A graph showing the characteristics of the discharge voltage and current of the mass spectrometer of the present embodiment is shown. In the graph, the horizontal axis is the applied voltage of the needle of the ion source, and the vertical axis is the current detected by the return current detection unit mounted on the ion source power supply. When the needle applied voltage is increased from 0V in the positive polarity direction, the return current also increases, and when the needle applied voltage reaches X1, the return current increases sharply. At this time, the needle applied voltage X1 is a voltage that starts discharging with a positive polarity, and the return current Y1 is a current that starts discharging with a positive polarity. On the other hand, when the needle applied voltage is reduced from 0V in the negative polarity direction, the return current increases in the negative polarity direction, and when the needle applied voltage reaches X2, the return current increases sharply in the negative polarity direction. At this time, the needle applied voltage X2 is a voltage that starts discharging with a negative polarity, and the return current Y2 is a current that starts discharging with a negative polarity.

[0085] Here, the positive polarity needle applied voltage X1 and the negative polarity needle applied voltage X2 are different from each other, and the positive polarity return current Y1 and the negative polarity return current Y2 are different from each other. Therefore, it should be noted that if a threshold is set for the return current to determine whether there is a discharge, the discharge cannot be detected in the following cases.

[0086] Here, as a comparative example, the case where the threshold for judging whether the ion source has discharged or not is the same when measuring positive ions and when measuring negative ions is described. For example, when the return current amount Y1 of the positive polarity is set as the threshold, when the return current amount Y2 of the negative polarity is lower than the return current amount Y1 of the positive polarity, even if negative ionization is performed and measured and discharge occurs, the current amount of the return current detection unit is lower than the threshold, and the discharge cannot be detected. Therefore, the threshold for judging whether the ion source has discharged or not when the sample to be analyzed is positively ionized and measured and the threshold for measuring negative ions need to be set to different values.

[0087] In addition, the absolute values ​​of the positive polarity needle applied voltage X1 and the negative polarity needle applied voltage X2 are different from each other, and the absolute values ​​of the positive polarity return current Y1 and the negative polarity return current Y2 are different from each other. Therefore, if judgment is made only by one absolute value of the return current, there may be a case where discharge cannot be detected.

[0088] Figure 4 and Figure 5 A signal diagram showing the setting of a threshold value for determining abnormal discharge in the mass spectrometer according to the present embodiment is shown. Figure 4 This is a signal diagram when a positive voltage is applied to the needle and the counter electrode. Figure 5 This is a signal diagram when a negative voltage is applied to the needle and the counter electrode. Figure 4 and Figure 5In the signal graphs showing current signals A and B, the horizontal axis represents time and the vertical axis represents current amount.

[0089] exist Figure 4 and Figure 5 In the present invention, as threshold values ​​for judging the presence or absence of discharge, a positive threshold value 30 and a negative threshold value 31 for comparison with the current amount of the return current detection unit 1a of the ion source power supply are described. Figure 4 and Figure 5 In the embodiment, as the thresholds for judging whether there is discharge, a positive threshold 40 and a negative threshold 41 for comparison with the current amount of the return current detection unit 1b of the opposing electrode power supply are described. Here, the absolute values ​​of the threshold 30 and the threshold 31 are set to different values, and the absolute values ​​of the threshold 40 and the threshold 41 are also set to different values.

[0090] <Effects of the present embodiment>

[0091] like Figure 4 As shown in FIG. 1 , when the sample is positively ionized for measurement, threshold values ​​30 and 40 are used as threshold values. Figure 5 As shown, when the sample is negatively ionized for measurement, the threshold values ​​31 and 41 are used as threshold values. Thus, even if the discharge current is different between the positive polarity and the negative polarity, the presence or absence of discharge can be properly determined.

[0092] (Implementation 3)

[0093] In order to shorten the analysis time in a mass spectrometer, there is a method of switching between the measurement by positive ionization and the measurement by negative ionization in a short time (hereinafter referred to as positive-negative switching measurement). Figure 6 as well as Figure 7 A method of determining the presence or absence of discharge of the ion source in the mass spectrometer described in the second embodiment will be described.

[0094] The positive-negative switching measurement (positive-negative ion switching measurement) is achieved by switching the voltage polarity applied to the needle and the opposing electrode of the ion source in a short time. The switching time at this time is, for example, several ms to tens of ms. Here, a parasitic capacitance is physically generated between the needle and the frame of the device and between the opposing electrode and the frame of the device, and the ion source power supply and the opposing electrode power supply charge the parasitic capacitance when applying voltage to the needle and the opposing electrode.

[0095] Figure 6 A signal diagram showing the return current waveform of the ion source power supply during the measurement of positive and negative ions switching is shown. Figure 6The horizontal axis is time, the vertical axis is the return current, and the time axis is divided into a region representing a measurement (positive) for a measurement performed with positive ionization and a region representing a measurement (negative) for a measurement performed with negative ionization. In addition, a threshold value 30 of positive polarity and a threshold value 31 of negative polarity are also recorded. Here, the solid line portions of the threshold values ​​30 and 31 are regions where the threshold values ​​are valid. For example, in the threshold value 30, the region representing a measurement (positive) for a measurement performed with positive ionization is indicated by a solid line, and the region representing a measurement (negative) is indicated by a dotted line, thereby clearly indicating that the threshold value 30 is valid in the region representing the measurement (positive). Conversely, the threshold value 31 is indicated by a solid line in the region representing the measurement (negative), and by a dotted line in the region representing the measurement (positive). In Figure 6 In FIG. 1 , a signal waveform when the discharge 51 occurs is indicated by a dashed line.

[0096] exist Figure 6 In the measurement (negative) when switching to the measurement (positive), the return current amount increases due to the inrush current 50 used to charge the above-mentioned parasitic capacitance. At this time, the return current amount exceeds the threshold value 30. Similarly, when switching from the measurement (positive) to the measurement (negative), the return current amount also exceeds the threshold value 31 due to the inrush current 50. That is, in the positive-negative switching measurement, the inrush current 50 and the discharge current cannot be distinguished, and the inrush current during the switching action is erroneously detected as discharge.

[0097] As a countermeasure, Figure 7 The method of shielding the inrush current during the positive and negative switching measurement in the mass spectrometer of this embodiment is shown in the signal diagram. Figure 7 In FIG. 5 , a signal waveform when the discharge 51 is generated is indicated by a dot-dash line. The switching between the measurement by positive ionization and the measurement by negative ionization is performed by the control unit 2 of the mass spectrometer (see Figure 1 ) control. Since the control unit 2 knows the timing of the inrush current, it is possible to set a dead time 53 in which the threshold value determination is not performed so as not to detect the discharge when the timing is switched. In addition, the time until the inrush current stabilizes is measured in advance and set in the control unit 2. Figure 7 In the signal diagram, the time period of the dead time 53 is marked with a hatched line.

[0098] That is, here, a fixed time from immediately before the surge current occurs to when the surge current stabilizes, and a time during which the threshold determination is not performed (dead time 53) is set. The fixed time is at least the time from the time point immediately before the surge current occurs, that is, the timing immediately before the measurement by positive ionization and the measurement by negative ionization are switched to the time when the absolute value of the current amount is less than the threshold.

[0099] <Effects of the present embodiment>

[0100] As described above, in the positive-negative switching measurement, when switching between measurement with positive ionization and measurement with negative ionization, a dead time in which discharge is not detected is provided to shield the rush current, thereby suppressing erroneous detection of discharge.

[0101] (Implementation 4)

[0102] In the third embodiment, a dead time is provided at the timing of the occurrence of the surge current so as not to erroneously detect the surge current as the discharge current when the measurement is switched between the measurement performed by positive ionization and the measurement performed by negative ionization in a short period of time. Figure 8 to Figure 11 This indicates that the dead time only requires the amount of current sent by the return current detection unit of the ion source power supply, and does not require the amount of current sent by the return current detection unit of the counter electrode power supply.

[0103] Figure 8 A wiring diagram showing the paths of the respective surge currents of the ion source power supply and the counter electrode power supply constituting the mass spectrometer of the present embodiment is shown. Here, as an example, the operation of changing the voltage of the needle 3 and the counter electrode 19 from negative polarity to positive polarity in order to switch from a measurement performed by negative ionization to a measurement performed by positive ionization is described.

[0104] First, the surge current path of the ion source power supply is described. When the ion source power supply 20 applies voltage to the needle 3, the parasitic capacitance 7a between the needle 3 and the frame 1 is charged. The surge current 8a generated during the charging is output from the ion source power supply 20, and returns to the ion source power supply 20 through the needle 3 and the parasitic capacitance 7a, the frame 1, and the return current detection unit 1a. That is, the surge current 8a is generated by the current 3a (see Figure 2 ) the same path.

[0105] Next, the surge current path of the opposing electrode power supply is described. When the opposing electrode power supply 21 applies a voltage to the opposing electrode 19, the parasitic capacitance 7b between the opposing electrode 19 and the frame 1 is charged. The surge current 8b generated during the charging is output from the opposing electrode power supply 21, and returns to the opposing electrode power supply 21 through the opposing electrode 19, the parasitic capacitance 7b, the frame 1, and the return current detection unit 1b in sequence. That is, the surge current 8b is generated when the current 3b (see Figure 2 ) in the opposite direction through the return current detection unit 1b.

[0106] use Fig. 9 , more specifically describing the directions of the paths of the inrush current 8b and the current 3b. Fig. 9FIG. 1 is a wiring diagram showing the respective paths of the discharge current and the surge current of the counter electrode power supply constituting the mass spectrometer of the present embodiment. Fig. 9 In FIG. 1 , the path of the current 3 b is indicated by a solid line, and the path of the surge current 8 b is indicated by a dotted line.

[0107] The current 3b generated by the discharge 2b overlaps with the counter electrode 19 and is sucked into the first terminal (output terminal) of the counter electrode power supply 21. At this time, the counter electrode power supply 21 outputs a positive voltage while absorbing the current. The current 3b sucked into the counter electrode power supply 21 passes through the return current detection unit 1b and then returns to the ion source power supply 20 (see FIG. 1 ) which is the current supply source of the discharge 2b via the frame 1. Figure 2 On the other hand, since the counter electrode power supply 21 charges the counter electrode 19 to positive polarity, the flow direction of the surge current 8 b becomes the direction of discharge from the first terminal (output terminal) of the counter electrode power supply 21 .

[0108] Based on the above, the inrush current 8b and the current 3b pass through the return current detection unit 1b in opposite directions.

[0109] In addition, the above description is about the following operation: in order to switch from the measurement by negative ionization to the measurement by positive ionization, the voltage of the needle 3 and the counter electrode 19 is changed from negative polarity to positive polarity. In contrast, regarding the operation of changing the switching voltage polarity from positive polarity to negative polarity, the directions of the current flows are only opposite to each other, and similarly, the directions of the rush current 8b and the current 3b passing through the return current detection unit 1b are opposite to each other.

[0110] Fig.10 The return current waveform of the ion source power supply of this embodiment is shown in the signal diagram. Fig.11 2 is a signal diagram showing a return current waveform of the counter electrode power supply of the present embodiment. Fig.10 as well as Fig.11 The waveform shown is a waveform when the voltage of the needle 3 and the counter electrode 19 is changed from negative polarity to positive polarity in order to switch from measurement by negative ionization to measurement by positive ionization. Fig.10 and Fig.11 In FIG. 1 , a signal waveform when the discharge 51 occurs is indicated by a dashed line.

[0111] like Fig.10 As shown in FIG. 1 , the return current waveform of the ion source power supply generates an inrush current 50 at the switching timing from measurement (negative) to measurement (positive). In order to prevent the inrush current 50 from being mistakenly detected as discharge 51, a dead time 53 is provided as described in the above-mentioned embodiment 3. On the other hand, Fig.11As shown in FIG. 1 , in the return current waveform of the counter electrode power supply, a surge current 54 is also generated at the switching timing from measurement (negative) to measurement (positive). However, the flow direction of the surge current 54 is opposite to the flow direction of the surge current 50 and the discharge 51. Therefore, even if the dead time is not provided, in the case of the threshold value 30 when switching to measurement for positive ionization, the surge current 54 will not be erroneously detected as a discharge.

[0112] That is, in the control unit, a dead time 53 is set for detecting discharge not based on the current measured by the return current detection unit 1a when the polarity of the voltage applied from the ion source power supply to the needle is switched. In contrast, in the control unit, a dead time 53 is not set for detecting discharge not based on the current measured by the return current detection unit 1b when the polarity of the voltage applied from the opposing electrode power supply to the opposing electrode is switched. In other words, here, when the polarity of the voltage applied from the ion source power supply to the needle is switched, the discharge is not detected based on the current measured by the return current detection unit 1a during a fixed time from before the switching to after the switching. In contrast, when the polarity of the voltage applied from the opposing electrode power supply to the opposing electrode is switched, the discharge is detected based on the current measured by the return current detection unit 1b continuously before and after the switching action.

[0113] <Effects of the present embodiment>

[0114] In the positive-negative switching measurement, in order to prevent the inrush current generated when switching between the measurement performed by positive ionization and the measurement performed by negative ionization from being mistakenly detected as discharge, it is sufficient to set a dead time for not detecting discharge for the current amount sent by the return current detection unit mounted on the ion source power supply. Thus, it is only the ion source power supply that needs to pre-determine the dead time period, and it is not necessary for the opposing electrode power supply. That is, for the measurement in the opposing electrode power supply, it is not necessary to set the dead time, so the rising adjustment time for discharge detection can be shortened.

[0115] (Implementation method 5)

[0116] In the above-mentioned embodiments 1 to 4, a unit for detecting discharge in an ion source is described. Hereinafter, a method for determining whether discharge occurs in a collection unit, a separation unit, and a detector based on the current amount detected by the return current detection unit and the detection result of the ion amount measured by the mass spectrometer when measuring a sample to be analyzed, is described in which a mass spectrometer is equipped with a collection unit power supply, a separation unit power supply, and a detector power supply having a return current detection unit.

[0117] In order to explain the unit for detecting the discharge current outside the ion source, Fig.14, a schematic diagram of the mass spectrometer of the present embodiment is shown in FIG. The mass spectrometer of the present embodiment has a collector power supply 22, a separator power supply 23, and a detector power supply 24. The collector power supply 22 is a power supply for applying a voltage to the electrode 9a provided in the collector 11. The separator power supply 23 is a power supply for applying a voltage to the electrode 9b provided in the separator 12. The detector power supply 24 is a power supply for applying a voltage to the conversion dynode (electrode) 9c provided in the detector 13.

[0118] The collecting part power supply 22, the separating part power supply 23, and the detector power supply 24 respectively have return current detection parts (ammeters) 1c, 1d, and 1e capable of detecting output currents based on the return currents returned via the frame 1. That is, the collecting part power supply 22 is electrically connected to the frame 1 via the return current detection part 1c, the separating part power supply 23 is electrically connected to the frame 1 via the return current detection part 1d, and the detector power supply 24 is electrically connected to the frame 1 via the return current detection part 1e.

[0119] The collector power supply 22, the separator power supply 23, and the detector power supply 24 respectively have a first terminal, a second terminal, and a third terminal in the same manner as the opposing electrode power supply 21 of the above-mentioned embodiment 1. The first terminal (output terminal) of the collector power supply 22 is electrically connected to the electrode 9a. The second terminal (ground wire) of the collector power supply 22 is electrically connected to the frame 1. The third terminal of the collector power supply 22 is electrically connected to the control unit 2. The first terminal (output terminal) of the separator power supply 23 is electrically connected to the electrode 9b. The second terminal (ground wire) of the separator power supply 23 is electrically connected to the frame 1. The third terminal of the separator power supply 23 is electrically connected to the control unit 2. The first terminal (output terminal) of the detector power supply 24 is electrically connected to the conversion multiplier 9c. The second terminal (ground wire) of the detector power supply 24 is electrically connected to the frame 1. The third terminal of the detector power supply 24 is electrically connected to the control unit 2.

[0120] However, in each of the collector power supply 22, the separator power supply 23, and the detector power supply 24, the third terminal is electrically insulated from the first terminal and the second terminal. That is, the unit that transmits the current detected by the return current detection units (ammeters) 1c, 1d, and 1e is electrically insulated from the control unit 2 as the transmission destination. In other words, the return current detection units 1c, 1d, 1e, the collector power supply 22, the separator power supply 23, and the detector power supply 24 are insulated from the control unit 2.

[0121] In addition, although the collector power supply 22, the separator power supply 23 and the detector power supply 24 are Figure 1Although not shown, it is also provided in the mass spectrometer of the above-mentioned embodiment 1. That is, the mass spectrometer of this embodiment is different from the mass spectrometer of the above-mentioned embodiment 1 in that the collector power supply 22, the separator power supply 23 and the detector power supply 24 have return current detection parts 1c, 1d and 1e respectively.

[0122] The control unit 2 has a function of displaying the detection result of the ion amount sent from the ion detector 7 to the operator. In addition, the control unit 2 has the following functions: receiving the current amount sent from the return current detection units 1c, 1d and 1e, judging whether the current amount is normal or abnormal by comparing the current amount with a threshold value, and displaying the judgment result. In addition, the control unit 2 has a function of controlling the overall measurement of mass analysis. The operator operates the mass spectrometer through the control unit 2. In addition, as described above, the current amount sent from the return current detection units 1c, 1d and 1e can be compared with the threshold value to judge whether the current amount is normal or abnormal, and the current amount sent from the return current detection units 1a, 1b can be compared with the threshold value to judge whether there is discharge in the ion source 10.

[0123] <Effects of the present embodiment>

[0124] Since the measurement abnormality caused by the discharge of the collection part, separation part and detector of the mass spectrometer is known instantly, the measurement can be interrupted in a short time to reduce the waste of samples. In addition, the measurement data at this time is deleted as invalid data due to abnormality, which can ensure the soundness of the analysis results. In addition, since the discharge location is also known in a short time, the maintainability can be improved.

[0125] As mentioned above, the invention completed by the present inventors has been specifically described based on the embodiments thereof, but the present invention is not limited to the above-mentioned embodiments, and various modifications can be made without departing from the gist thereof.

[0126] Industrial Applicability

[0127] The present invention can be widely used in mass spectrometry apparatuses and mass spectrometry methods.

[0128] Explanation of symbols

[0129] 1. Framework

[0130] 1a~1e Return current detection unit (ammeter)

[0131] 2. Control Unit

[0132] 3-pin

[0133] 4Pre-processing unit

[0134] 6Ion-to-electric conversion unit

[0135] 7 Ion detector

[0136] 9c conversion dynode

[0137] 11 Collection Department

[0138] 12Separation unit

[0139] 13 Detector

[0140] 19 Opposing Electrode

[0141] 20 ion source power supply

[0142] 21. Power supply for opposing electrodes.

Claims

1. A mass spectrometer for analyzing a sample, characterized in that: The mass analysis device comprises: a frame, which is a container having electrical conductivity; an ion source that ionizes the sample to generate an ionized sample; a detector for detecting the amount of ions by electrons released from the ionized sample; and a control unit that displays the amount of ions measured by the detector, The ion source has: a needle disposed within the frame; an electrode disposed within the frame separately from the needle; a first power source that applies a first voltage to the needle; a second power source that applies a second voltage to the electrode; a first current detection unit connected in series between a ground line of the first power source and the frame; as well as a second current detection unit connected in series between a ground line of the second power source and the frame, The control unit determines whether a first discharge occurs between the needle and a component of the ion source other than the electrode and whether a second discharge occurs between the needle and the electrode based on the current amounts respectively measured by the first current detection unit and the second current detection unit. The control unit performs the following processing: When the absolute value of the first current measured by the first current detection unit is greater than or equal to a first threshold value and the absolute value of the second current measured by the second current detection unit is less than a second threshold value, determining that the first discharge has occurred; as well as When the absolute value of the first current amount is equal to or greater than the first threshold value and the absolute value of the second current amount is equal to or greater than the second threshold value, it is determined that the second discharge has occurred.

2. The mass spectrometer according to claim 1, characterized in that When the occurrence of the first discharge is detected, the location where the first discharge occurs is displayed, and when the occurrence of the second discharge is detected, the location where the second discharge occurs is displayed.

3. The mass spectrometer according to claim 1, characterized in that The control unit performs the following processing: When the polarities of the first voltage and the second voltage are positive, the third threshold is used as the first threshold, and the fourth threshold is used as the second threshold; as well as When the polarities of the first voltage and the second voltage are negative, the fifth threshold is applied as the first threshold, and the sixth threshold is applied as the second threshold.

4. The mass spectrometer according to claim 1, wherein: The control unit displays the presence or absence of discharge detection on the user interface.

5. The mass spectrometer according to claim 4, characterized in that When the first discharge or the second discharge is detected, the control unit displays a discharge occurrence location on the user interface.

6. The mass spectrometer according to claim 1, wherein: When the measurement is performed by switching between positive and negative ions, a dead time is set in the control unit so as not to detect discharge when the power supply voltage is switched.

7. The mass spectrometer according to claim 6, characterized in that The control unit continuously detects discharge based on the second current amount measured by the second current detection unit before and after the operation of switching the polarity of the second voltage.

8. The mass spectrometer according to claim 1, wherein: The electrodes are arranged at the ion source, the collecting part, the separating part or the detector.

9. A mass analysis method for analyzing a sample, characterized in that: The mass analysis method uses a mass analysis device, The mass analysis device has: a frame, which is a container having electrical conductivity; an ion source that ionizes the sample to generate an ionized sample; a detector for detecting the amount of ions by electrons released from the ionized sample; and a control unit that displays the amount of ions measured by the detector, The ion source has: a needle disposed within the frame; an electrode disposed within the frame separately from the needle; a first power source that applies a first voltage to the needle; a second power source that applies a second voltage to the electrode; a first current detection unit connected in series between a ground line of the first power source and the frame; as well as a second current detection unit connected in series between a ground line of the second power source and the frame, The steps performed in the control unit include: (a) starting a mass analysis process using the mass analysis device; as well as (b) after step (a), determining whether a first discharge occurs between the needle and a structure of the ion source other than the electrode and whether a second discharge occurs between the needle and the electrode, respectively, based on a result obtained by comparing the absolute value of the current sent from the first current detection unit and the second current detection unit with a threshold value, The control unit performs the following processing in step (b): When the absolute value of the first current measured by the first current detection unit is greater than or equal to a first threshold value and the absolute value of the second current measured by the second current detection unit is less than a second threshold value, determining that the first discharge has occurred; as well as When the absolute value of the first current amount is equal to or greater than the first threshold value and the absolute value of the second current amount is equal to or greater than the second threshold value, it is determined that the second discharge has occurred.

10. The mass analysis method according to claim 9, characterized in that: As a step executed in the control unit, the following steps are further performed: (c) When the occurrence of the first discharge or the second discharge is detected in the step (b), a location where the first discharge or the second discharge occurs is displayed.

11. The mass analysis method according to claim 9, characterized in that: As a step executed in the control unit, the following steps are further performed: (d) When the occurrence of the first discharge or the second discharge is detected in the step (b), the mass spectrometry process is stopped.

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