Mass spectrometry device, voltage generation circuit, and method for controlling mass spectrometry device

Abstract

A mass spectrometry device (10) comprises: an ion generation mechanism; an ion trap mechanism (140); a detector (150); and a voltage generation circuit (180). The ion trap mechanism captures ions in an internal space surrounded by a plurality of electrodes. The detector detects ions that have been discharged from the ion trap mechanism. The plurality of electrodes include: first electrodes (141) that generate an electric field for capturing ions; and second electrodes (142, 144) that, while the ions are being captured, generate an electric field for discharging specific ions from the ion trap mechanism. The voltage generation circuit includes: voltage sources (181, 182); switches (SW1, SW2); and resistance circuits (RC1, RC2). The voltage source (182) supplies a lower voltage than the voltage source (181). The switches (SW1, SW2) selectively supply the voltages from the voltage sources (181, 182) to the first electrode. The resistance circuits (RC1, RC2) are respectively connected to control terminals of the switches (SW1, SW2). Each of the resistance circuits has a variable resistance value.

Description

Mass spectrometer, voltage generating circuit, and method for controlling a mass spectrometer

[0001] The present disclosure relates to a mass spectrometer, a voltage generation circuit used therein, and a method for controlling a mass spectrometer.

[0002] Ion trap mass analyzers using digital ion traps are known, as disclosed in U.S. Pat. No. 6,900,433 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2022-52108 (Patent Document 2). In such ion trap mass analyzers, a square-wave high voltage having a predetermined frequency corresponding to the mass range of the ions to be trapped is applied to a ring electrode as a trapping high voltage, thereby confining the ions to be analyzed within the electric field generated by the ring electrode. Subsequently, for example, a square-wave low voltage obtained by dividing the square-wave high voltage applied to the ring electrode by a predetermined frequency division ratio is applied to the end cap electrodes, and the frequencies of the square-wave high voltage and the square-wave low voltage are simultaneously scanned. Through this operation, the trapped ions are resonantly excited in order of their mass-to-charge ratio (hereinafter also referred to as "m / z") and ejected from the ion exit aperture. The ejected ions are then detected by a detector. A mass spectrum can be obtained based on the detected ion intensities.

[0003] US Patent No. 6,900,433 JP 2022-52108 A

[0004] In the ion trap mass spectrometer described above, it is assumed that the square wave voltage applied to the electrodes of the ion trap mechanism is an ideal square wave. However, in the power supply circuit that generates the applied voltage, the applied voltage actually deviates from the ideal square wave due to variations in the characteristics of individual electronic elements that make up the circuit (machine differences), an unavoidable finite rise time, and / or aging. Therefore, a mass spectrum obtained using such an applied voltage may differ from a mass spectrum obtained using an ideal waveform.

[0005] Generally, the acquired mass spectrum is calibrated using a mass calibration curve (function) obtained by measuring a standard sample composed of specific known samples with the instrument. The mass calibration curve is calculated, for example, by linear approximation so that the measured values ​​of two specific samples in the standard sample match the theoretical values.

[0006] However, as mentioned above, if the waveform of the voltage applied to the power supply circuit deviates from the ideal waveform, the mass calibration curve obtained from the standard sample itself may be inaccurate, which may increase the error in the measured mass of the sample to be analyzed, resulting in a decrease in measurement accuracy.

[0007] The present disclosure has been made to solve such problems, and its purpose is to improve the measurement accuracy in an ion trap mass spectrometer.

[0008] A mass spectrometer according to one aspect of the present disclosure relates to an ion trap mass spectrometer. The mass spectrometer includes an ion generation mechanism, an ion trap mechanism, a detector, a voltage generation circuit, and a control device that controls the voltage generation circuit. The ion generation mechanism supplies ions in a pulsed manner. The ion trap mechanism is configured with multiple electrodes and is configured to trap ions in an internal space surrounded by the multiple electrodes by an electric field formed in the internal space. The detector detects ions ejected from the ion trap mechanism. The voltage generation circuit applies a voltage to the multiple electrodes. The multiple electrodes include a first electrode and a second electrode. A square-wave high-frequency voltage is applied to the first electrode from the voltage generation circuit. The voltage generation circuit includes a first voltage source and a second voltage source, a first switch and a second switch, and a first resistor circuit and a second resistor circuit. The second voltage source has a lower voltage than the first voltage source. The first switch selectively supplies the voltage from the first voltage source to the first electrode. The second switch selectively supplies a voltage from the second voltage source to the first electrode. The first resistor circuit is connected to a control terminal of the first switch and has a variable resistance value. The second resistor circuit is connected to a control terminal of the second switch and has a variable resistance value.

[0009] A voltage generation circuit according to another aspect of the present disclosure is used in an ion trap mass spectrometer. The mass spectrometer includes an ion generation mechanism that supplies ions in a pulsed manner, an ion trap mechanism, and a detector. The ion trap mechanism is composed of multiple electrodes and is configured to trap ions in the internal space by an electric field formed in the internal space surrounded by the multiple electrodes. The detector detects ions ejected from the ion trap mechanism. The multiple electrodes include a first electrode and a second electrode. A square-wave radio frequency voltage is applied to the first electrode from the voltage generation circuit. The voltage generation circuit includes first and second voltage sources, first and second switches, and first and second resistor circuits. The second voltage source has a voltage lower than that of the first voltage source. The first switch selectively supplies the voltage from the first voltage source to the first electrode. The second switch selectively supplies the voltage from the second voltage source to the first electrode. The first resistor circuit is connected to a control terminal of the first switch and is configured to have a variable resistance value. The second resistor circuit is connected to the control terminal of the second switch and has a variable resistance value.

[0010] A method according to yet another aspect of the present disclosure relates to a method for controlling an ion trap mass spectrometer. The mass spectrometer includes an ion trap mechanism and a voltage generation circuit. The ion trap mechanism is configured with a plurality of electrodes and is configured to trap ions in the internal space by an electric field formed in the internal space surrounded by the plurality of electrodes. The voltage generation circuit applies a voltage to the plurality of electrodes. The plurality of electrodes include a first electrode and a second electrode, and a square-wave high-frequency voltage is applied to the first electrode from the voltage generation circuit. The voltage generation circuit includes a first voltage source and a second voltage source, a first switch and a second switch, and a first resistance circuit and a second resistance circuit. The second voltage source has a voltage lower than that of the first voltage source. The first switch selectively supplies a voltage from the first voltage source to the first electrode. The second switch selectively supplies a voltage from the second voltage source to the first electrode. The first resistance circuit is connected to a control terminal of the first switch. The second resistance circuit is connected to a control terminal of the second switch. The method includes the steps of: i) measuring mass accuracy using a standard sample; ii) determining whether the mass accuracy of the measured standard sample is within a standard range; and iii) if the mass accuracy of the standard sample is not within the standard range, adjusting the resistance value of at least one of the first resistor circuit and the second resistor circuit so that the mass accuracy is within the standard range.

[0011] In a mass spectrometer according to the present disclosure, a voltage generation circuit that supplies voltage to a first electrode (ring electrode) included in an ion trap mechanism includes two switches, each of whose control terminals is provided with a resistor circuit capable of variably setting its resistance value. This configuration allows the voltages supplied to the ring electrode from the two voltage sources to be individually adjusted, thereby enabling the voltage supplied to the ring electrode to approach an ideal square wave voltage. This reduces variations in the mass calibration curve that may arise due to differences in electronic components, such as switches, that make up the voltage generation circuit. Therefore, measurement accuracy can be improved in an ion trap mass spectrometer.

[0012] FIG. 1 is an overall block diagram of a mass spectrometer equipped with a voltage generation circuit according to a first embodiment. FIG. 2 is a diagram for explaining the configuration of the voltage generation circuit of FIG. 1. FIG. 3 is a diagram for explaining changes in the calibration curve of a standard sample when the gate voltage of each switch is changed. FIG. 4 is a flowchart for explaining a method for correcting a resistance circuit in a voltage generation circuit. FIG. 5 is a diagram for explaining the configuration of a voltage generation circuit according to a second embodiment. FIG. 6 is a diagram showing each resistance circuit of FIG. 5. FIG. 7 is a diagram showing a resistance circuit of a first modification. FIG. 8 is a diagram showing a resistance circuit of a second modification. FIG. 9 is a diagram for explaining the configuration of a voltage generation circuit according to a third embodiment. FIG. 10 is a diagram for explaining the configuration of a voltage generation circuit of a third modification. FIG. 11 is a diagram for explaining an ion trap mechanism of a mass spectrometer according to a fourth embodiment.

[0013] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0014] 1 is an overall block diagram of a mass spectrometer 10 equipped with a voltage generation circuit 180 according to embodiment 1. The mass spectrometer 10 is a matrix-assisted laser desorption / ionization digital ion trap mass spectrometer (MALDI-DITMS), which is an example of an ion trap type mass spectrometer.

[0015] Referring to FIG. 1, the mass spectrometer 10 includes a measurement unit 100, a vacuum pump 160, a laser irradiation unit 170, a voltage generation circuit 180, a gas supply unit 185, a control device 200, an operation unit 190, and a display unit 195.

[0016] The measurement unit 100 has a box-shaped chamber 105 configured so that the interior can be evacuated to a vacuum by a vacuum pump 160. Inside the chamber 105, a sample stage 110, an extraction electrode 120, a quadrupole deflector 130, an ion trap mechanism 140, and a detector 150 are arranged.

[0017] A driving device (not shown) is attached to the sample stage 110. This driving device can move the sample stage 110 on the XY plane along the main surface of the sample stage 110. A sample plate 115 is placed on the sample stage 110. A sample SP to be analyzed, prepared by mixing a matrix, is placed on the sample plate 115, and laser light from a laser irradiation unit 170 (described below) is irradiated onto the sample SP. The laser light enters the chamber 105 through a window 107 on the top surface of the chamber 105 and is irradiated onto the sample SP approximately perpendicularly from the positive direction of the Z axis in the figure. This vaporizes and ionizes the sample components in the sample SP. In the case of a MALDI digital ion trap mass spectrometer, positively charged ions (positive ions) and / or negatively charged ions (negative ions) are generated depending on the type of matrix and additives used. Of the generated ions, there are two operating modes: one in which positive ions are the subject of analysis (positive ion mode), and one in which negative ions are the subject of analysis (negative mode). The following explanation will be given using the positive ion mode as an example.

[0018] The generated ions are extracted from the vicinity of the sample plate 115 in the positive direction of the Z axis by an electric field generated by the potential difference between the sample stage 110 and the extraction electrode 120 and guided to the deflector 130. For example, a voltage of +10 V is applied to the sample stage 110, and a voltage of −6 kV is applied to the extraction electrode 120. The deflector 130 includes four cylindrical electrodes extending in the Y axis direction. The four electrodes are arranged at the four corners of a substantially square when viewed from above in the Y axis direction. Voltages are applied to the individual electrodes of the deflector 130 so that a deflection electric field is generated by the four electrodes. A voltage of −6 kV, for example, is applied to each electrode of the deflector 130. This deflection electric field bends the trajectory of the ions that have passed through the extraction electrode 120 in the X axis direction. The deflected ions are introduced into the ion trap mechanism 140.

[0019] The ion trap mechanism 140 includes a ring electrode 141 having an inner surface shaped like a hyperboloid of one leaf of revolution, and a pair of end cap electrodes 142 and 144 arranged opposite each other across the ring electrode 141. Each of the end cap electrodes 142 and 144 has an inner surface shaped like a hyperboloid of two leafs of revolution. By applying a predetermined voltage from a voltage generation circuit 180 to the ring electrode 141 and the end cap electrodes 142 and 144, ions can be trapped in an internal space 146 surrounded by these electrodes, or ions can be ejected from the internal space 146.

[0020] An entrance hole 143 is formed in the center of the end cap electrode 142, and ions deflected by the deflector 130 pass through the entrance hole 143 and enter the internal space 146. At this time, to introduce positive ions into the internal space 146, for example, a voltage of −10 V is applied to the entrance end cap electrode 143 and a voltage of +10 V is applied to the exit end cap electrode 144. After ions generated by laser irradiation of the sample reach the internal space 146 of the ion trap, i.e., after a predetermined time has elapsed since the timing of laser irradiation, the end cap electrode 142 is set to ground potential or a predetermined bias voltage, and a square-wave high voltage is applied to the ring electrode 141 from the voltage generation circuit 180, thereby forming a trapping electric field (pseudopotential) for trapping ions in the internal space 146. The ions introduced into the internal space 146 are trapped in the internal space 146 by this trapping electric field.

[0021] By adjusting the frequency and / or duty ratio of the square-wave voltage applied to the ring electrode 141, ions having a mass-to-charge ratio within a specific range are selected as precursor ions, and ions having a mass-to-charge ratio outside that range are ejected from the exit aperture 145. Ions having a mass-to-charge ratio within a specific range may also be selected as precursor ions by applying a predetermined voltage to the endcap electrode 142 in addition to the ring electrode 141. In the case of MS analysis, ions generated by laser irradiation of a sample are trapped in the ion trap. A square-wave high voltage is applied to the ring electrode 141, and a square-wave low voltage, which is obtained by dividing the square-wave high voltage applied to the ring electrode 141 by a predetermined frequency division ratio, is applied to the endcap electrodes 142 and 144. The frequencies of the square-wave high voltage and the square-wave low voltage are simultaneously scanned, so that the ions are ejected from the exit aperture 145 in order of their mass-to-charge ratio.

[0022] MS / MS analysis of precursor ions selected in the internal space 146 by collision-induced dissociation (CID) is performed as follows. First, while the precursor ions are selected and trapped in the internal space 146, an inert gas, such as argon (Ar), is introduced into the internal space 146 from the gas supply unit 185 as a collision gas. An excitation voltage having a frequency equal to the secular frequency determined by the mass-to-charge ratio of the precursor ions is then applied to the endcap electrodes 142 and 144. As a result, the precursor ions oscillate and collide with the collision gas, thereby dissociating the precursor ions and generating various product ions. The frequencies of the square-wave high voltage and square-wave low voltage applied to the ring electrode 141 and the endcap electrodes 142 and 144 are then simultaneously scanned, and the generated product ions are ejected from the exit aperture 145 in order of their mass-to-charge ratio.

[0023] The detector 150 detects the ions ejected from the ion trap mechanism 140 and outputs a detection signal corresponding to the amount of detected ions to the control device 200 .

[0024] The laser irradiation unit 170 is controlled by the control device 200 to irradiate the sample SP in the chamber 105 with a pulsed laser, thereby ionizing the specimen components in the sample SP.

[0025] The voltage generation circuit 180 is controlled by the control device 200 and generates voltages to be applied to the ring electrode 141 and the endcap electrodes 142, 144 included in the ion trap mechanism 140. At each stage of analysis, the voltage generation circuit 180 adjusts the voltages to be applied to the ring electrode 141 and the endcap electrodes 142, 144 to trap ions in the ion trap mechanism 140, select precursor ions, generate product ions, and eject ions in order of mass-to-charge ratio.

[0026] The gas supply unit 185 supplies helium (He), nitrogen (N ２ The gas supply unit 185 includes a storage unit for storing an inert gas such as hydrogen (H2O) or argon (Ar), and a flow rate regulator for adjusting the flow rate of the gas. The gas supply unit 185 supplies an appropriate gas to the internal space 146 of the ion trap mechanism 140 to cool the ions in the internal space 146 and dissociate precursor ions to generate product ions.

[0027] The control device 200 is, for example, a general-purpose personal computer (PC) or a server device, and controls the entire mass spectrometer 10, and processes the detection signals of ions detected by the detector 150 to generate a mass spectrum. The control device 200 includes a CPU (Central Processing Unit) 210, a memory 220, and an interface (I / F) 230. The CPU 210, the memory 220, and the interface 230 are connected to one another by a common communication bus 240, and are configured to be able to send and receive information among them.

[0028] The CPU 210 is configured to execute predetermined arithmetic processing described in a program. The memory 220 includes a read-only memory (ROM) and a random access memory (RAM). The ROM stores the program executed by the CPU 210. The RAM temporarily stores data generated by the execution of the program in the CPU 210 and data input via the interface 230. The RAM also functions as temporary data memory used as a working area. The memory 220 may also include a large-capacity storage device such as a hard disc drive (HDD), an optical drive, or a solid state drive (SSD).

[0029] The interface 230 transmits and receives signals between the control device 200 and external devices. The interface 230 may include a wireless communication unit (not shown) that transmits and receives signals via wireless communication.

[0030] An operation unit 190 and a display unit 195 are connected to the control device 200. The operation unit 190 includes, for example, a keyboard, a mouse, a touch panel, etc., and is configured to allow the user to input setting values, etc. The display unit 195 includes, for example, a liquid crystal display (LCD) panel or an organic electroluminescence (EL) panel, etc., and displays device setting information, operation information, and analysis results such as mass spectra to the user. The display unit 195 may also include a printing device such as a printer.

[0031] The above explanation shows an example of the voltages applied to each component in the positive ion mode. However, in the negative ion mode, the following voltages are applied to each component so that negative ions generated from the sample are introduced into the internal space: A voltage of −10 V is applied to the sample stage 110, and a voltage of +6 kV is applied to the deflector 130. Furthermore, when introducing ions into the ion trap, a voltage of +10 V is applied to the entrance end cap electrode 143, and a voltage of −10 V is applied to the exit end cap electrode 144. Furthermore, when trapping ions, selecting precursor ions, and ejecting ions, voltages of opposite polarity to those applied in the positive ion mode are applied to the ring electrode 141 as a square-wave high voltage and to the end cap electrode 142 as a square-wave low voltage.

[0032] (Configuration of Voltage Generator Circuit) Next, details of the voltage generator circuit 180 for generating a rectangular wave high voltage will be described using Figure 2. Figure 2 is a diagram for explaining a more detailed configuration of the voltage generator circuit 180 of Figure 1. The voltage generator circuit 180 includes input terminals T1 and T2, an output terminal T3, a high-voltage side power supply 181, a low-voltage side power supply 182, and a switch circuit 183. The switch circuit 183 also includes resistor circuits RC1 and RC2, switches SW1 and SW2, and buffers BF1 and BF2.

[0033] The switches SW1 and SW2 are semiconductor switches such as metal-oxide-semiconductor field effect transistors (MOSFETs) or insulated gate bipolar transistors (IGBTs). In the following description, the switches SW1 and SW2 are described as N-channel MOSFETs.

[0034] The drain electrode of switch SW1 is connected to the high-voltage power supply 181, and the source electrode is connected to the drain electrode of switch SW2. The source electrode of switch SW2 is connected to the low-voltage power supply 182. A connection node ND1 between the source electrode of switch SW1 and the drain electrode of switch SW2 is connected to output terminal T3. Output terminal T3 is connected to ring electrode 141 of ion trap mechanism 140.

[0035] The high-voltage power supply 181 is a voltage source capable of supplying a predetermined positive DC voltage V1. The low-voltage power supply 182 is a voltage source capable of supplying a predetermined DC voltage V2 that is lower than that of the high-voltage power supply 181 (V1>V2). The DC voltage V2 may be a positive voltage or a negative voltage as long as it is lower than the DC voltage V1. As an example, the DC voltage V2 may be set to V2=-V1, which has the opposite polarity to the DC voltage V1 but has the same absolute value.

[0036] As will be described later, switches SW1 and SW2 operate in a complementary manner. Therefore, when switch SW1 is conductive, i.e., when switch SW2 is non-conductive, DC voltage V1 from high-voltage power supply 181 is supplied to ring electrode 141 via output terminal T3. Conversely, when switch SW1 is non-conductive, i.e., when switch SW2 is conductive, DC voltage V2 from low-voltage power supply 182 is supplied to ring electrode 141 via output terminal T3.

[0037] One end of a resistor circuit RC1 is connected to the gate terminal, which is the control terminal of the switch SW1. The other end of the resistor circuit RC1 is connected to the input terminal T1 via a buffer BF1. Similarly, one end of a resistor circuit RC2 is connected to the gate terminal, which is the control terminal of the switch SW2. The other end of the resistor circuit RC2 is connected to the input terminal T2 via a buffer BF2. Each of the resistor circuits RC1 and RC2 is, for example, a semi-fixed resistor, and is configured so that its resistance value can be manually set variably. The buffers BF1 and BF2 are, for example, amplifiers with a gain of 1, and are used to remove noise from the input signal and adjust impedance.

[0038] Control signals Pcon and Ncon are supplied to input terminals T1 and T2, respectively, from the control device 200. The control signals Pcon and Ncon are rectangular wave signals with mutually inverted phases. That is, when the control signal Pcon is Hi, the control signal Ncon becomes Lo, and when the control signal Pcon is Lo, the control signal Ncon becomes Hi. The duty and frequency of the control signals Pcon and Ncon are controlled by the control device 200.

[0039] When control signals Pcon and Ncon are supplied from the control device 200 to the voltage generating circuit 180 configured in this manner, a rectangular wave voltage Vout having voltage V1 as the maximum voltage and voltage V2 as the minimum voltage is supplied to the ring electrode 141.

[0040] In the ion trap mass spectrometer described above, the gate resistance of the switch in the voltage generation circuit is typically set to a predetermined fixed resistance before shipping. However, the inventors have discovered that the square wave voltage applied to the electrodes of the ion trap mechanism deviates from the ideal square wave due to differences in the characteristics of the switches used, unavoidable finite rise times, variations in the resistance values ​​of the connecting wiring, and / or changes in characteristics due to aging. When a mass spectrum is acquired using such a square wave voltage, the resulting mass spectrum differs from that obtained using a square wave voltage with an ideal waveform, which can affect the analysis results.

[0041] Typically, acquired mass spectra are calibrated using a mass calibration curve obtained by measuring a standard sample composed of specific known samples with the instrument. The mass calibration curve is calculated, for example, by linear approximation so that the measured values ​​of two specific samples in the standard sample match the theoretical values. However, as mentioned above, if the waveform of the voltage applied to the power supply circuit deviates from the ideal waveform, the mass calibration curve obtained from the standard sample itself may be inaccurate. This can result in larger errors in the measured mass, resulting in a decrease in measurement accuracy.

[0042] Therefore, in the mass spectrometer 10 of the first embodiment, in the voltage generation circuit 180 that generates the voltage supplied to the electrodes of the ion trap mechanism 140, resistor circuits RC1 and RC2 with adjustable resistance values ​​are provided at the gate terminals of the switches SW1 and SW2 that generate the voltage supplied to the ring electrode 141. By adjusting the resistance values ​​of these resistor circuits RC1 and RC2, deviations in the square wave voltage caused by differences between the switches SW1 and SW2 can be reduced, and an appropriate mass calibration curve can be obtained for each device. Therefore, it is possible to improve the measurement accuracy in the ion trap mass spectrometer.

[0043] (Method of correcting the resistance circuit) Fig. 3 is a diagram illustrating the change in the calibration curve of the standard sample when the resistance values ​​of the resistance circuits RC1 and RC2 are changed to change the gate voltage of each switch. In each graph in Fig. 3, the horizontal axis represents the mass-to-charge ratio (m / z), and the vertical axis represents the error between the mass obtained from the measured mass spectrum and the actual mass.

[0044] In the example of Figure 3, mass spectra were measured for standard samples composed of seven types of known samples, and mass calibration curves were shown in which the mass errors of the sample with the smallest mass (m / z = 1046.54) and the sample with the second largest mass (m / z = 2465.20) were set to 0 ppm.

[0045] Line LN11 in the middle diagram (B) is a mass calibration curve when the resistance values ​​R1 and R2 of the resistor circuits RC1 and RC2 are respectively set to α [Ω]. Line LN10 in the upper diagram (A) is a mass calibration curve when the resistance value of the resistor circuit RC1 is reduced from the state of diagram (B) to β [Ω]. Line LN12 in the lower diagram (C) is a mass calibration curve when the resistance value of the resistor circuit RC2 is reduced from the state of diagram (B) to β [Ω].

[0046] In the example of Figure 3, when (R1, R2) = (α, α) as shown in the middle row (B), the mass error is generally flat. When (R1, R2) = (β, α) as shown in the top row (A), where the resistance value of resistor circuit RC1 is made smaller than the resistance value of resistor circuit RC2, the mass error tends to be generally downward convex. On the other hand, when (R1, R2) = (α, β) as shown in the bottom row (C), where the resistance value of resistor circuit RC2 is made smaller than the resistance value of resistor circuit RC1, the mass error tends to be generally upward convex.

[0047] Therefore, in the case of the example mass spectrometer used in Figure 3, if the obtained mass calibration curve is downwardly convex as shown in the upper row (A), it can be made to approach a mass calibration curve like the middle row (B) by adjusting the resistance value of resistor circuit RC1 to be larger or the resistance value of resistor circuit RC2 to be smaller. On the other hand, if the obtained mass calibration curve is upwardly convex as shown in the lower row (C), it can be made to approach a mass calibration curve like the middle row (B) by adjusting the resistance value of resistor circuit RC2 to be larger or the resistance value of resistor circuit RC1 to be smaller. Note that the change in the mass calibration curve shown in Figure 3 is just one example, and in other voltage generation circuits, changing the resistance values ​​may result in different characteristic changes in the mass calibration curve.

[0048] In this way, by measuring in advance the pattern of change characteristics of the mass calibration curve when the resistance value of each resistor circuit is changed in each device, it is possible to correct the resistance value of each resistor circuit and adjust the deviation of the mass calibration curve during regular maintenance, etc.

[0049] 4 is a flowchart illustrating a method for correcting the resistor circuits RC1 and RC2 in the voltage generating circuit 180. In step (hereinafter, step is abbreviated as S) 10, the adjuster measures the mass accuracy (mass error) using a standard sample. Then, in S20, the adjuster determines whether the obtained mass accuracy is within a reference range across the target m / z range. Here, the reference range is, for example, within ±100 ppm.

[0050] If the obtained mass accuracy is within the standard range (YES in S20), adjustment of the mass calibration curve is not necessary, so the adjuster skips the subsequent steps and ends the adjustment work. On the other hand, if the mass accuracy is outside the standard range (NO in S20), adjustment of the mass calibration curve is necessary, so the adjuster determines the correction amount for the resistance values ​​of the resistor circuits RC1 and RC2 in S30 by comparing the obtained mass accuracy with a previously measured measurement pattern. Then, in S40, the adjuster adjusts the resistor circuits RC1 and RC2 to the determined resistance values.

[0051] Thereafter, returning to S10, the adjuster measures the mass accuracy again using the adjusted resistance value and a standard sample, and repeats steps S10 to S40 until the mass accuracy falls within the desired standard range.

[0052] By adjusting the mass calibration curve in this manner, it is possible to reduce mass errors in the mass calibration curve in the target m / z range, thereby reducing the effects of differences in electronic components in the voltage generation circuit and improving the measurement accuracy of the mass spectrometer.

[0053] The "laser irradiation unit 170" in the first embodiment is an example of an "ion generation mechanism" in the present disclosure. The "ring electrode 141" and the "end cap electrodes 142, 144" in the first embodiment correspond to the "first electrode" and the "second electrode," respectively, in the present disclosure. The "high-voltage side power supply 181" and the "low-voltage side power supply 182" in the first embodiment correspond to the "first voltage source" and the "second voltage source," respectively, in the present disclosure. The "switch SW1" and the "switch SW2" in the first embodiment correspond to the "first switch" and the "second switch," respectively, in the present disclosure. The "resistance circuit RC1" and the "resistance circuit RC2" in the first embodiment correspond to the "first resistance circuit" and the "second resistance circuit," respectively, in the present disclosure.

[0054] [Embodiment 2] In the first embodiment, a configuration was described in which mass accuracy is ensured by configuring the semi-fixed resistor placed in the gate resistor in the voltage generation circuit so that it can be adjusted by an adjuster at the time of factory shipment or during maintenance, etc.

[0055] However, in the configuration of the first embodiment, when adjusting a variable resistor, the voltage generation circuit must be opened and an adjuster must directly manipulate the variable resistor on the board, which requires opening the voltage generation circuit every time an adjustment is made, which can increase the number of adjustment steps.

[0056] Therefore, in the second embodiment, a configuration will be described in which the resistance circuit in the voltage generating circuit is configured to be adjustable from outside the voltage generating circuit, thereby reducing the number of adjustment steps.

[0057] 5 is a diagram illustrating the configuration of a voltage generating circuit 180A according to the second embodiment. In voltage generating circuit 180A, switch circuit 183 in voltage generating circuit 180 shown in FIG. 2 is replaced with switch circuit 183A, and input terminals T4 and T5 are further added. In voltage generating circuit 180A, descriptions of elements that overlap with those in voltage generating circuit 180 will not be repeated.

[0058] 5, in switch circuit 183A of voltage generating circuit 180A, resistor circuits RC1A and RC2 of voltage generating circuit 180 are replaced with resistor circuits RC1A and RC2A. Each of resistor circuits RC1A and RC2A is a variable resistor whose resistance value can be variably set by an external control signal. Input terminals T4 and T5 receive control signals SC1 and SC2, respectively, from control device 200. Resistor circuit RC1A can switch its resistance value in multiple stages based on the control signal SC1 received at input terminal T4. Similarly, resistor circuit RC2A can switch its resistance value in multiple stages based on the control signal SC2 received at input terminal T5.

[0059] Fig. 6 is a diagram showing the detailed circuit of each resistor circuit in Fig. 5. In Fig. 6, the detailed circuit of the resistor circuit RC1A will be described as an example, but the resistor circuit RC2A has a similar circuit configuration.

[0060] The resistor circuit RC1A includes resistors R11, R12, and R13 connected in series between the switch SW1 and the buffer BF1, and a bypass circuit BP1. The bypass circuit BP1 includes switches TR1 and TR2, each configured, for example, by a MOSFET. The switch TR1 is connected between a connection node N1 between the resistors R11 and R12 and a connection node N3 between the resistor R13 and the buffer BF1. The switch TR2 is connected between a connection node N2 between the resistors R12 and R13 and the connection node N3.

[0061] The switch TR1 is switched between conductive and non-conductive states in accordance with the gate signal GS1 in the control signal SC1. Similarly, the switch TR2 is switched between conductive and non-conductive states in accordance with the gate signal GS2 in the control signal SC1. By making only the switch TR1 conductive, the resistors R12 and R13 are bypassed, and the control signal Pcon passes only through the resistor R11. By making only the switch TR2 conductive, the resistor R13 is bypassed, and the control signal Pcon passes through the resistors R11 and R12. By making both the switches TR1 and TR2 non-conductive, the control signal Pcon passes through the resistors R11, R12, and R13.

[0062] In this way, by switching switches TR1 and TR2 using control signal SC1, it is possible to selectively bypass some of resistors R11, R12, and R13. This allows the gate resistance of switch SW1 to be switched between three levels based on a signal supplied from outside the voltage generating circuit 180A without opening the voltage generating circuit 180A. This reduces the number of adjustment steps required by the adjustment technician during the adjustment work.

[0063] Note that the control signal SC1 is output from the control device 200 to the voltage generation circuit 180A based on, for example, an input from an adjuster to the operation unit 190. Alternatively, if an automatic calibration sequence function is installed, the control signal SC1 is automatically output from the control device 200 to the voltage generation circuit 180A in accordance with the calibration sequence.

[0064] The "switch TR1" and the "switch TR2" in the second embodiment correspond to the "switching unit" in the present disclosure. The "resistance circuit RC1A" and the "resistance circuit RC2A" in the second embodiment correspond to the "first resistance circuit" and the "second resistance circuit" in the present disclosure, respectively.

[0065] (Modification 1) In Modification 1, a configuration of a resistance circuit that can adjust the gate resistance in multiple stages by operating more switching units using a decoder will be described. Note that, in Modification 1, for ease of explanation, the resistance circuit on the switch SW1 side will also be described as an example.

[0066] 7 is a diagram showing a resistor circuit RC1B of Modification 1. Similar to the resistor circuit RC1A of Embodiment 2, the resistor circuit RC1B includes a plurality of resistors R11 to R19 connected in series between the switch SW1 and the buffer BF1, and a bypass circuit BP2. The bypass circuit BP2 includes switches TR1 to TR8 and a decoder 184.

[0067] The switch TR1 is connected between a connection node N1 between the resistors R11 and R12 and a connection node N9 between the resistor R19 and the buffer BF1. The switch TR2 is connected between a connection node N2 between the resistors R12 and R13 and the connection node N9. The switch TR3 is connected between a connection node N3 between the resistors R13 and R14 and the connection node N9. The switch TR4 is connected between a connection node N4 between the resistors R14 and R15 and the connection node N9. The switch TR5 is connected between a connection node N5 between the resistors R15 and R16 and the connection node N9. The switch TR6 is connected between a connection node N6 between the resistors R16 and R17 and the connection node N9. The switch TR7 is connected between a connection node N7 between the resistors R17 and R18 and the connection node N9. The switch TR8 is connected between a connection node N8 between the resistors R18 and R19 and a connection node N9.

[0068] By switching each of the switches TR1-TR8 between conductive and non-conductive states, the resistors R11-R19 can be selectively bypassed.

[0069] The decoder 184 is an integrated circuit configured to control the switches TR1 to TR8 in response to a control signal SC1 input from the control device 200. The control signal SC1 includes three-bit signals B1 to B3. That is, the decoder 184 can output eight different signals (2 ３ The eight outputs of the decoder 184 are connected to the gate terminals of the switches TR1 to TR8, respectively. Depending on the output of the decoder 184, any one of the switches TR1 to TR8 can be made conductive.

[0070] When switch TR1 is conductive, resistors R12 to R19 are bypassed and the control signal Pcon passes through resistor R11. When switch TR2 is conductive, resistors R13 to R19 are bypassed and the control signal Pcon passes through resistors R11 and R12. When switch TR3 is conductive, resistors R14 to R19 are bypassed and the control signal Pcon passes through resistors R11 to R13. When switch TR4 is conductive, resistors R15 to R19 are bypassed and the control signal Pcon passes through resistors R11 to R14. When switch TR5 is conductive, resistors R16 to R19 are bypassed and the control signal Pcon passes through resistors R11 to R15. When switch TR6 is conductive, resistors R16 to R19 are bypassed and the control signal Pcon passes through resistors R11 to R15. When the switch TR7 is conductive, the resistors R18 and R19 are bypassed and the control signal Pcon passes through the resistors R11 to R17. When the switch TR8 is conductive, the resistor R19 is bypassed and the control signal Pcon passes through the resistors R11 to R18. When all of the switches TR1 to TR8 are non-conductive, the control signal Pcon passes through all of the resistors R11 to R19.

[0071] In this way, by using decoder 184, the gate resistance of switch SW1 can be switched in nine stages by the 3-bit control signal SC1 from control device 200. Therefore, the number of adjustment steps required by an adjustment technician during adjustment work can be reduced.

[0072] A digital potentiometer may be used as the resistor circuit RC1B. The digital potentiometer is a variable resistor IC equipped with a nonvolatile memory, and its resistance value changes based on a control signal SC1 from the control device 200. For example, one example of the potentiometer can set 1 kΩ to 256 positions.

[0073] Each of the "switches TR1" to "switches TR8" in the first modification corresponds to the "switching unit" in the present disclosure.

[0074] (Modification 2) In Modification 2, a configuration will be described in which a variable resistor and an actuator for driving a trimmer of the variable resistor are used as the resistance circuit. In Modification 2, for ease of explanation, the resistance circuit on the switch SW1 side will also be described as an example.

[0075] FIG. 8 is a diagram showing a resistor circuit RC1C of Modification 2. The resistor circuit RC1C includes a resistor R20, which is a semi-fixed resistor, and a motor M10. The motor M10 is, for example, a stepping motor, and is controlled by a control signal SC1 from the control device 200. The control signal SC1 is a pulse signal, and the rotating shaft of the motor M10 rotates in accordance with the number of pulses of the control signal SC1. The rotating shaft of the motor M10 is connected to a trimmer TM1 of the resistor R20. As a result, the gate resistance of the switch SW1 can be changed by rotating the rotating shaft of the motor M10.

[0076] In this way, in the resistor circuit RC1C as well, the gate resistance of the switch SW1 can be switched based on a signal supplied from outside the voltage generating circuit, thereby reducing the number of adjustment steps required by an adjustment technician during adjustment work.

[0077] [Embodiment 3] As described above, in a digital ion trap mass spectrometer, by switching the polarity of the ion trap mechanism, it is possible to perform measurements in two measurement modes: a "positive ion mode" in which positively charged ions are the analysis target, and a "negative ion mode" in which negatively charged ions are the analysis target.

[0078] However, the present inventors have found that a mass calibration curve optimally adjusted in "positive ion mode" is not necessarily optimal in "negative ion mode," and that the mass calibration curves suitable for each mode differ.

[0079] In the third embodiment, a configuration will be described in which a mass spectrometer capable of switching between a "positive ion mode" and a "negative ion mode" can set a mass calibration curve suitable for each mode.

[0080] 9 is a diagram illustrating the configuration of a voltage generating circuit 180B according to embodiment 3. In voltage generating circuit 180B, switch circuit 183A in voltage generating circuit 180A described in embodiment 2 is replaced with switch circuit 183B.

[0081] The switch circuit 183B includes resistor circuits RC1D and RC2D and relays RY1 and RY2 in addition to switches SW1 and SW2 and buffers BF1 and BF2. The resistor circuit RC1D includes resistors R1P and R1N, which are semi-fixed resistors, and the resistor circuit RC2D includes resistors R2P and R2N, which are semi-fixed resistors.

[0082] Each of the relays RY1 and RY2 has one input terminal and two output terminals (first terminal and second terminal), and is configured to be able to output a signal received at the input terminal to either the first terminal or the second terminal.

[0083] An input terminal of relay RY1 is connected to buffer BF1. A first terminal of relay RY1 is connected to the gate terminal of switch SW1 via resistor R1P. A second terminal of relay RY1 is connected to the gate terminal of switch SW1 via resistor R1N. Relay RY1 is controlled by a control signal SC1 received at input terminal T4 from control device 200, and switches between a first path via resistor R1P and a second path via resistor R1N.

[0084] Similarly, the input terminal of relay RY2 is connected to buffer BF2. The first terminal of relay RY2 is connected to the gate terminal of switch SW2 via resistor R2P. The second terminal of relay RY2 is connected to the gate terminal of switch SW2 via resistor R2N. Relay RY2 is controlled by a control signal SC2 received at input terminal T5 from control device 200, and switches between a first path via resistor R2P and a second path via resistor R2N.

[0085] In the third embodiment, the polarity of the control signals supplied from the control device 200 to the input terminals T1 and T2 is switched between the positive mode and the negative mode. That is, in the positive mode, the control signal Pcon is supplied to the input terminal T1, and the control signal Ncon is supplied to the input terminal T2. Conversely, in the negative mode, the control signal Ncon is supplied to the input terminal T1, and the control signal Pcon is supplied to the input terminal T2.

[0086] In the positive mode, the control signals SC1 and SC2 switch both relays RY1 and RY2 to the first path. That is, the resistor R1P in the resistor circuit RC1D and the resistor R2P in the resistor circuit RC2 are selected. On the other hand, in the negative mode, the control signals SC1 and SC2 switch both relays RY1 and RY2 to the second path. That is, the resistor R1N in the resistor circuit RC1D and the resistor R2N in the resistor circuit RC2 are selected.

[0087] Then, by adjusting resistors R1P and R2P to have a mass calibration curve suitable for the positive mode, and adjusting resistors R1N and R2N to have a mass calibration curve suitable for the negative mode, mass accuracy can be ensured in each measurement mode.

[0088] In the switch circuit 183B of the third embodiment, a pre-adjusted semi-fixed resistor is switched by a relay depending on the measurement mode, but a variable resistor such as those shown in FIGS. 6 to 8 may be used, and the resistance value may be changed by a control signal from a control device depending on the measurement mode.

[0089] The "resistor circuit RC1D" and the "resistor circuit RC2D" in the third embodiment correspond to the "first resistor circuit" and the "second resistor circuit" in the present disclosure, respectively. The "resistor R1P," the "resistor R1N," the "resistor R2P," and the "resistor R2N" in the third embodiment correspond to the "first resistor" to the "fourth resistor" in the present disclosure, respectively.

[0090] (Modification 3) In Modification 3, a configuration will be described in which the polarity of the gate signal supplied to each switch is switched in a switch circuit according to the measurement mode.

[0091] 10 is a diagram illustrating the configuration of a voltage generating circuit 180C according to Modification 3. In the voltage generating circuit 180C, the switch circuit 183B of the third embodiment is replaced with a switch circuit 183C, and further, the resistor circuits RC1D and RC2D are replaced with resistor circuits RC1E and RC2E, respectively.

[0092] The resistance circuit RC1E includes resistors R1P and R1N similar to the resistance circuit RC1D of the third embodiment, but differs in that the resistor R1N used in the negative mode is connected to the gate terminal of the switch SW2. The resistance circuit RC2E includes resistors R2P and R2N similar to the resistance circuit RC2D of the third embodiment, but differs in that the resistor R2N used in the negative mode is connected to the gate terminal of the switch SW1.

[0093] With this connection configuration, in the positive mode, the control signal Pcon supplied to the input terminal T1 from the control device 200 is supplied to the gate terminal of the switch SW1 via the resistor R1P, and the control signal Ncon supplied to the input terminal T2 is supplied to the gate terminal of the switch SW2 via the resistor R2P. On the other hand, in the negative mode, the control signal Pcon supplied to the input terminal T1 is supplied to the gate terminal of the switch SW2 via the resistor R1N, and the control signal Ncon supplied to the input terminal T2 is supplied to the gate terminal of the switch SW1 via the resistor R2N. In other words, the measurement mode can be switched simply by switching the relays RY1 and RY2, without switching the polarities of the control signals Pcon and Ncon supplied to the input terminals T1 and T2 from the control device 200 according to the measurement mode.

[0094] By setting resistors R1P and R2P to resistance values ​​suitable for the positive mode and resistors R1N and R2N to resistance values ​​suitable for the negative mode, it is possible to obtain a mass calibration curve suitable for each measurement mode when switching between measurement modes, thereby ensuring mass accuracy in each measurement mode.

[0095] It is also possible to use a variable resistor such as those shown in FIGS. 6 to 8 instead of the semi-fixed resistor in the switch circuit 183C of the third modified example, and to use a relay to switch the switch to be connected depending on the measurement mode, and to change the resistance value of the variable resistor according to a control signal from the control device.

[0096] The "resistance circuit RC1E" and the "resistance circuit RC2E" in Modification 3 correspond to the "first resistance circuit" and the "second resistance circuit" in the present disclosure, respectively.

[0097] [Embodiment 4] In the first embodiment, an example of an ion trap mechanism having a structure including a ring electrode and end cap electrodes each having a hyperboloid of revolution shape has been described, but the ion trap mechanism is not limited to this configuration.

[0098] In the fourth embodiment, an example will be described in which the features of the present disclosure are applied to a mass spectrometer that uses a quadrupole linear ion trap as an ion trap mechanism.

[0099] 11 is a diagram illustrating an ion trap mechanism 340 of a mass spectrometer according to the fourth embodiment. The ion trap mechanism 340 includes two pairs of opposing electrodes, 341A and 341B and 342A and 342B. Each electrode has a cylindrical or semi-cylindrical shape. Electrode 341A faces electrode 341B, and electrode 342A faces electrode 342B. Electrodes 341A and 341B face electrode 342A and 342B. Electrodes 341A and 341B in the ion trap mechanism 340 correspond to the ring electrode 141 in the first embodiment shown in FIG. 1, and electrodes 342A and 342B correspond to the end cap electrodes 143 and 145 in the first embodiment.

[0100] 11, the direction in which each electrode extends is the Z axis, the direction in which electrodes 341A and 341B face each other is the X axis, and the direction in which electrodes 342A and 342B face each other is the Y axis.

[0101] Each electrode is separated into a front section SC1, a center section SC2, and a back section SC3 in the Z-axis direction. The sections are electrically insulated from each other. A slot 350 is formed on the side of electrode 342A, communicating with the space surrounded by the four electrodes.

[0102] 1 are introduced into the ion trap mechanism 340 in the Z-axis direction through an opening 360 on the front section SC1 side. Then, by setting the electrodes 342A and 342B to the ground potential and applying a predetermined square wave voltage to the electrodes 341A and 341B, the introduced ions are trapped in the ion trap mechanism 340. At this time, a predetermined voltage is applied to the front section SC1 and the back section SC3 so as to keep the trapped ions near the center of the central section SC2 in the Z-axis direction.

[0103] Thereafter, an excitation voltage obtained by dividing the square wave voltage applied to electrodes 341A and 341B is applied to electrodes 342A and 342B, whereby ions having a specific mass-to-charge ratio are ejected in the positive direction of the Y axis from slot 350. The ejected ions are detected by detector 150 in FIG.

[0104] Thus, even when a linear ion trap is used as the ion trap mechanism, the square wave voltage applied to the electrodes 341A and 341B may deviate from an ideal square waveform, resulting in a decrease in measurement accuracy. Therefore, even in the configuration of embodiment 4, measurement accuracy can be improved by adjusting the resistance value of the gate resistor in the voltage generation circuit that applies voltage to the electrodes 341A and 341B in accordance with the mass measurement pattern of the standard sample.

[0105] [Notes] It will be understood by those skilled in the art that the exemplary embodiments described above are specific examples of the following aspects.

[0106] (Item 1) A mass spectrometer according to one aspect relates to an ion trap mass spectrometer. The mass spectrometer includes an ion generation mechanism, an ion trap mechanism, a detector, a voltage generation circuit, and a control device that controls the voltage generation circuit. The ion generation mechanism supplies ions in a pulsed manner. The ion trap mechanism is composed of multiple electrodes and is configured to trap ions in an internal space surrounded by the multiple electrodes by an electric field formed in the internal space. The detector detects ions ejected from the ion trap mechanism. The voltage generation circuit applies a voltage to the multiple electrodes. The multiple electrodes include a first electrode and a second electrode. A square-wave high-frequency voltage is applied to the first electrode from the voltage generation circuit. The voltage generation circuit includes a first voltage source and a second voltage source, a first switch and a second switch, and a first resistor circuit and a second resistor circuit. The second voltage source has a lower voltage than the first voltage source. The first switch selectively supplies the voltage from the first voltage source to the first electrode. The second switch selectively supplies a voltage from the second voltage source to the first electrode. The first resistor circuit is connected to a control terminal of the first switch and has a variable resistance value. The second resistor circuit is connected to a control terminal of the second switch and has a variable resistance value.

[0107] According to the mass spectrometer of the first aspect, the voltage supplied to the ring electrode from two voltage sources can be individually adjusted by variable resistance circuits provided at the control terminals of two switches included in a voltage generation circuit that supplies voltage to the first electrode (ring electrode) included in the ion trap mechanism. This allows the square wave voltage supplied to the ring electrode to approach an ideal square wave, thereby reducing variations in the mass calibration curve that can arise due to differences in the electronic components that make up the voltage generation circuit. This therefore improves the measurement accuracy of the ion trap mass spectrometer.

[0108] (Item 2) In the mass spectrometer described in item 1, each of the first switch and the second switch is a field effect transistor (FET) having a gate terminal as a control terminal.

[0109] According to the mass spectrometer according to the second aspect, a general-purpose FET can be used as a switch in the voltage generating circuit, so that the circuit can be realized at a relatively low cost.

[0110] (Item 3) In the mass spectrometer according to item 1 or 2, each of the first resistor circuit and the second resistor circuit is a semi-fixed resistor.

[0111] According to the mass spectrometer of the third aspect, by using a semi-fixed resistor in each resistor circuit, it becomes possible to adjust the resistance value of the gate resistor.

[0112] (4) In the mass spectrometer according to the first or second aspect, each of the first and second resistance circuits includes a plurality of resistors connected in series and a bypass circuit, which is controlled by a control device and is configured to selectively bypass some of the plurality of resistors.

[0113] According to the mass spectrometer of the fourth aspect, the resistance value of each resistance circuit can be adjusted by a control command from the control device, so that the resistance value can be adjusted without opening the voltage generating circuit.

[0114] (Item 5) In the mass spectrometer described in Item 4, the bypass circuit includes a plurality of switching units provided corresponding to the plurality of resistors. Each of the first resistance circuit and the second resistance circuit is configured so that its resistance value changes when the plurality of switching units are individually switched between conductive and non-conductive states.

[0115] According to the mass spectrometer of the fifth aspect, the resistance value of each resistor circuit can be adjusted by individually switching the switching units between conductive and non-conductive states in response to a control command from the control device, thereby making it possible to adjust the resistance value without opening the voltage generating circuit.

[0116] (Item 6) In the mass spectrometer according to item 5, the bypass circuit further includes a decoder configured to control the plurality of switching units according to a signal from the control device.

[0117] According to the mass spectrometer of the sixth aspect, a decoder can be used to control multiple switching units, making it possible to adjust the resistance value using a relatively simple circuit configuration without opening the voltage generating circuit.

[0118] (Item 7) In the mass spectrometer according to item 1 or 2, each of the first resistance circuit and the second resistance circuit is a digital potentiometer.

[0119] According to the mass spectrometer of the seventh aspect, a general-purpose digital potentiometer can be used as the resistance circuit, so that the resistance circuit can be realized at a relatively low cost.

[0120] (Item 8) In the mass spectrometer according to any one of items 1 to 7, the control device supplies square wave signals of opposite polarities to the control terminal of the first switch and the control terminal of the second switch.

[0121] According to the mass spectrometer of the eighth aspect, the voltage supplied to the ring electrode can be generated using square wave signals of opposite polarities from the control device.

[0122] (Item 9) The mass spectrometer described in Item 8 includes a first mode and a second mode as operating modes. The control device (a) in the first mode supplies a square wave signal of a first polarity to the control terminal of the first switch and supplies a square wave signal of a second polarity opposite to the first polarity to the control terminal of the second switch, and (b) in the second mode supplies a square wave signal of the second polarity to the control terminal of the first switch and supplies a square wave signal of the first polarity to the control terminal of the second switch.

[0123] According to the mass spectrometer of paragraph 9, the control device can easily switch between two measurement modes, positive mode (first mode) and negative mode (second mode), by inverting the polarity of the control signal supplied to each switch.

[0124] (Item 10) In the mass spectrometer described in Item 9, the first resistance circuit includes a first resistor and a second resistor. The second resistance circuit includes a third resistor and a fourth resistor. In a first mode, (a) the control device supplies a square wave signal of a first polarity to the first resistance circuit and a square wave signal of a second polarity to the second resistance circuit, (b) the square wave signal is supplied to a control terminal of the first switch via the first resistor, and (c) the square wave signal is supplied to a control terminal of the second switch via the third resistor. In a second mode, (d) the control device supplies a square wave signal of a second polarity to the first resistance circuit and a square wave signal of a first polarity to the second resistance circuit, (e) the square wave signal is supplied to a control terminal of the first switch via the second resistor, and (f) the square wave signal is supplied to a control terminal of the second switch via the fourth resistor.

[0125] According to the mass spectrometer of paragraph 10, two measurement modes can be easily switched by switching the polarity of the control signal supplied from the control device, and further, the gate resistance of each switch can be set individually according to each measurement mode. Therefore, even when the measurement mode is switched, the variation in the mass calibration curve for each measurement mode can be reduced, thereby improving measurement accuracy.

[0126] (Item 11) In the mass spectrometer described in Item 9, the first resistive circuit and the second resistive circuit are connected to a control terminal of the first switch and a control terminal of the second switch, respectively. The first resistive circuit includes a first resistor and a second resistor. The second resistive circuit includes a third resistor and a fourth resistor. In the first mode, (a) a square wave signal is supplied to the control terminal of the first switch via the first resistor, and (b) a square wave signal is supplied to the control terminal of the second switch via the third resistor. In the second mode, (c) a square wave signal is supplied to the control terminal of the second switch via the second resistor, and (d) a square wave signal is supplied to the control terminal of the first switch via the fourth resistor.

[0127] The mass spectrometer according to paragraph 11 allows easy switching between two measurement modes without switching the polarity of the control signal supplied from the control device, and further allows the gate resistance of each switch to be set individually according to each measurement mode. Therefore, even when the measurement mode is switched, the variation in the mass calibration curve for each measurement mode can be reduced, thereby improving measurement accuracy.

[0128] (Item 12) A voltage generation circuit according to one aspect is used in an ion trap mass spectrometer. The mass spectrometer includes an ion generation mechanism that supplies ions in a pulsed manner, an ion trap mechanism, and a detector. The ion trap mechanism is composed of multiple electrodes and is configured to trap ions in the internal space surrounded by the multiple electrodes by an electric field formed in the internal space. The detector detects ions ejected from the ion trap mechanism. The multiple electrodes include a first electrode and a second electrode. A rectangular wave radio frequency voltage is applied to the first electrode from the voltage generation circuit. The voltage generation circuit includes a first voltage source and a second voltage source, a first switch and a second switch, and a first resistor circuit and a second resistor circuit. The second voltage source has a voltage lower than that of the first voltage source. The first switch selectively supplies the voltage from the first voltage source to the first electrode. The second switch selectively supplies the voltage from the second voltage source to the first electrode. The first resistor circuit is connected to a control terminal of the first switch and is configured to have a variable resistance value. The second resistor circuit is connected to the control terminal of the second switch and has a variable resistance value.

[0129] According to the voltage generation circuit of paragraph 12, the voltages supplied to the ring electrode from the two voltage sources can be individually adjusted by variable resistance circuits provided at the control terminals of two switches included in the voltage generation circuit that supplies voltage to the first electrode (ring electrode) included in the ion trap mechanism. This allows the square-wave voltage supplied to the ring electrode to approach an ideal square wave, thereby reducing variations in the mass calibration curve that may arise due to differences in the electronic components that make up the voltage generation circuit. This therefore improves the measurement accuracy of the ion trap mass spectrometer.

[0130] (Item 13) In the voltage generating circuit described in item 12, each of the first switch and the second switch is an FET having a gate terminal as a control terminal.

[0131] According to the voltage generating circuit of the thirteenth aspect, general-purpose FETs can be used as switches in the voltage generating circuit, so that the circuit can be realized at relatively low cost.

[0132] (14) In the voltage generating circuit according to the 12th or 13th paragraph, each of the first resistor circuit and the second resistor circuit is a semi-fixed resistor.

[0133] According to the voltage generating circuit of the fourteenth aspect, by using a semi-fixed resistor in each resistor circuit, it becomes possible to adjust the resistance value of the gate resistor.

[0134] (Item 15) In the voltage generating circuit described in items 12 or 13, each of the first resistance circuit and the second resistance circuit includes a plurality of resistors connected in series and a bypass circuit. The bypass circuit is controlled by the control device and is configured to be able to selectively bypass some of the plurality of resistors.

[0135] According to the voltage generating circuit of paragraph 15, the resistance value of each resistor circuit can be adjusted by a control command from the control device, so that the resistance value can be adjusted without opening the voltage generating circuit.

[0136] (Item 16) In the voltage generating circuit described in item 15, the bypass circuit includes a plurality of switching units provided corresponding to the plurality of resistors. Each of the first resistance circuit and the second resistance circuit is configured so that its resistance value changes when the plurality of switching units are individually switched between conductive and non-conductive states.

[0137] According to the voltage generating circuit of paragraph 16, the resistance value of each resistor circuit can be adjusted by individually switching the conduction and non-conduction of the multiple switching units in response to a control command from the control device, thereby making it possible to adjust the resistance value without opening the voltage generating circuit.

[0138] (Item 17) In the voltage generating circuit described in item 16, the bypass circuit further includes a decoder configured to control the plurality of switching units in accordance with a signal from an external control device.

[0139] According to the voltage generating circuit of paragraph 17, a decoder can be used to control a plurality of switching units, so that a relatively simple circuit configuration can be used to adjust the resistance value without opening the voltage generating circuit.

[0140] (Item 18) In the voltage generating circuit described in item 12 or 13, each of the first resistance circuit and the second resistance circuit is a digital potentiometer.

[0141] According to the voltage generating circuit of the eighteenth aspect, a general-purpose digital potentiometer can be used as the resistor circuit, so that the resistor circuit can be realized at a relatively low cost.

[0142] (Item 19) A method according to one aspect relates to a method for controlling an ion trap mass spectrometer. The mass spectrometer includes an ion trap mechanism and a voltage generation circuit. The ion trap mechanism is composed of a plurality of electrodes and is configured to trap ions in the internal space by an electric field formed in the internal space surrounded by the plurality of electrodes. The voltage generation circuit applies a voltage to the plurality of electrodes. The plurality of electrodes include a first electrode and a second electrode. A square-wave high-frequency voltage is applied to the first electrode from the voltage generation circuit. The voltage generation circuit includes a first voltage source and a second voltage source, a first switch and a second switch, and a first resistance circuit and a second resistance circuit. The second voltage source has a lower voltage than the first voltage source. The first switch selectively supplies a voltage from the first voltage source to the first electrode. The second switch selectively supplies a voltage from the second voltage source to the first electrode. The first resistance circuit is connected to a control terminal of the first switch. The second resistance circuit is connected to a control terminal of the second switch. The method includes the steps of: i) measuring mass accuracy using a standard sample; ii) determining whether the mass accuracy of the measured standard sample is within a standard range; and iii) if the mass accuracy of the standard sample is not within the standard range, adjusting the resistance value of at least one of the first resistor circuit and the second resistor circuit so that the mass accuracy is within the standard range.

[0143] (Item 20) The method according to item 19, wherein the adjustment amounts of the resistance values ​​of the first resistor circuit and the second resistor circuit are predetermined according to a pattern of mass accuracy, and the method further includes a step of determining the adjustment amounts of the resistance values ​​of the first resistor circuit and the second resistor circuit based on the measurement pattern of the mass accuracy of the measured standard sample.

[0144] (Item 21) In the mass spectrometer described in item 1, when ions are trapped by the ion trap mechanism, the second electrode is set to ground potential. When a specific ion is ejected from the ion trap mechanism, a voltage of a frequency corresponding to the specific ion is applied to the second electrode from the voltage generation circuit.

[0145] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims.

[0146] 10 Mass spectrometer, 100 Measurement unit, 105 Chamber, 107 Window, 110 Sample stage, 115 Sample plate, 120 Extraction electrode, 130 Deflector, 140, 340 Ion trap mechanism, 141 Ring electrode, 142, 144 End cap electrode, 143 Incident hole, 145 Exit hole, 146 Internal space, 150 Detector, 160 Vacuum pump, 170 Laser irradiation unit, 180, 180A to 180C Voltage generation circuit, 181 High voltage side power supply, 182 Low voltage side power supply, 183, 183A to 183C Switch circuit, 184 Decoder, 185 Gas supply unit, 190 Operation unit, 195 Display unit, 200 Control device, 210 CPU, 220 Memory, 230 Interface, 240 Communication bus, 341A, 341B, 342A, 342B electrodes, 350 slot, 360 opening, BF1, BF2 buffer, BP1, BP2 bypass circuit, M10 motor, N1 to N9, ND1 connection node, R1, R1P, R1N, R2, R2P, R2N, R3, R11 to R20 resistors, RC1, RC1A to RC1E, RC2, RC2A, RC2D, RC2E resistance circuit, RY1, RY2 relay, SC1 front section, SC2 center section, SC3 back section, SP sample, SW1, SW2, TR1 to TR8 switches, T1 to T5 terminal, TM1 trimmer.

Claims

1. An ion trap type mass spectrometer comprising: an ion generation mechanism which supplies ions in a pulsed manner; an ion trap mechanism constituted by a plurality of electrodes and configured to trap ions in an internal space surrounded by the plurality of electrodes by an electric field formed in the internal space; a detector which detects ions ejected from the ion trap mechanism; a voltage generation circuit which applies a voltage to the plurality of electrodes; and a control device which controls the voltage generation circuit, wherein the plurality of electrodes include a first electrode and a second electrode, and a rectangular wave high frequency voltage is applied to the first electrode from the voltage generation circuit, and the voltage generation circuit comprises: a first voltage source; 2. The mass spectrometer according to claim 1, wherein each of the first switch and the second switch is a field effect transistor (FET) having a gate terminal as a control terminal.

3. The mass spectrometer according to claim 1 or 2, wherein each of the first resistance circuit and the second resistance circuit is a semi-fixed resistor.

4. A mass spectrometer as described in claim 1 or claim 2, wherein each of the first resistance circuit and the second resistance circuit includes a plurality of resistors connected in series, and a bypass circuit controlled by the control device and configured to selectively bypass some of the plurality of resistors.

5. A mass spectrometer as described in claim 4, wherein the bypass circuit includes a plurality of switching units provided corresponding to the plurality of resistors, and each of the first resistance circuit and the second resistance circuit is configured so that a resistance value changes when the plurality of switching units are individually switched between conductive and non-conductive.

6. The mass spectrometer of claim 5, wherein said bypass circuit further includes a decoder configured to control said plurality of switching elements according to a signal from said control device.

7. The mass spectrometer according to claim 1 or 2, wherein each of the first resistance circuit and the second resistance circuit is a digital potentiometer.

8. The mass spectrometer according to claim 1 or 2, wherein the control device supplies square wave signals of opposite polarities to the control terminal of the first switch and the control terminal of the second switch.

9. The mass spectrometer according to claim 8, wherein the mass spectrometer includes a first mode and a second mode as operating modes, and the control device, in the first mode, supplies a square wave signal of a first polarity to the control terminal of the first switch, and supplies a square wave signal of a second polarity opposite to the first polarity to the control terminal of the second switch, and in the second mode, supplies the square wave signal of the second polarity to the control terminal of the first switch, and supplies the square wave signal of the first polarity to the control terminal of the second switch.

10. The mass spectrometer of claim 9, wherein the first resistance circuit includes a first resistor and a second resistor, the second resistance circuit includes a third resistor and a fourth resistor, and in the first mode, the control device supplies a square wave signal of the first polarity to the first resistance circuit and supplies a square wave signal of the second polarity to the second resistance circuit, a square wave signal is supplied to a control terminal of the first switch via the first resistor, and a square wave signal is supplied to a control terminal of the second switch via the third resistor, and in the second mode, the control device supplies a square wave signal of the second polarity to the first resistance circuit and supplies a square wave signal of the first polarity to the second resistance circuit, a square wave signal is supplied to the control terminal of the first switch via the second resistor, and a square wave signal is supplied to the control terminal of the second switch via the fourth resistor.

11. The mass spectrometer of claim 9, wherein each of the first resistive circuit and the second resistive circuit is connected to a control terminal of the first switch and a control terminal of the second switch, the first resistive circuit includes a first resistor and a second resistor, the second resistive circuit includes a third resistor and a fourth resistor, and in the first mode, a square wave signal is supplied to the control terminal of the first switch via the first resistor, and a square wave signal is supplied to the control terminal of the second switch via the third resistor, and in the second mode, a square wave signal is supplied to the control terminal of the second switch via the second resistor, and a square wave signal is supplied to the control terminal of the first switch via the fourth resistor.

12. A voltage generation circuit used in an ion trap type mass spectrometer, the mass spectrometer including: an ion generation mechanism which supplies ions in a pulsed manner; an ion trap mechanism constituted by a plurality of electrodes and configured to trap ions in an internal space surrounded by the plurality of electrodes by an electric field formed in the internal space; and a detector which detects ions discharged from the ion trap mechanism, the plurality of electrodes including a first electrode and a second electrode, a rectangular wave high frequency voltage is applied to the first electrode from the voltage generation circuit, the voltage generation circuit including: a first voltage source; a second voltage source having a voltage lower than that of the first voltage source; a first switch which selectively supplies a voltage from the first voltage source to the first electrode; a second switch which selectively supplies a voltage from the second voltage source to the first electrode; a first resistor circuit connected to a control terminal of the first switch and configured to have a variable resistance value; and a second resistor circuit connected to a control terminal of the second switch and configured to have a variable resistance value.

13. The voltage generating circuit of claim 12, wherein each of the first switch and the second switch is a FET having a gate terminal as a control terminal.

14. The voltage generating circuit according to claim 12 or 13, wherein each of the first resistance circuit and the second resistance circuit is a semi-fixed resistor.

15. A voltage generating circuit as described in claim 12 or 13, wherein each of the first resistance circuit and the second resistance circuit includes a plurality of resistors connected in series, and a bypass circuit controlled by a control device and configured to selectively bypass a portion of the plurality of resistors.

16. The voltage generating circuit according to claim 15, wherein the bypass circuit includes a plurality of switching sections provided corresponding to the plurality of resistors, and each of the first resistance circuit and the second resistance circuit is configured so that a resistance value thereof changes when the plurality of switching sections are individually switched between conductive and non-conductive states.

17. The voltage generation circuit of claim 16, wherein said bypass circuit further includes a decoder configured to control said plurality of switching units according to a signal from an external control device.

18. The voltage generating circuit according to claim 12 or 13, wherein each of the first resistive circuit and the second resistive circuit is a digital potentiometer.

19. A method for controlling an ion trap type mass spectrometer, the mass spectrometer including: an ion trap mechanism constituted by a plurality of electrodes and configured to trap ions in an internal space surrounded by the plurality of electrodes by an electric field formed in the internal space; and a voltage generation circuit for applying a voltage to the plurality of electrodes, the plurality of electrodes including a first electrode and a second electrode, a rectangular wave high frequency voltage being applied to the first electrode from the voltage generation circuit, the voltage generation circuit including: a first voltage source; a second voltage source having a voltage lower than that of the first voltage source; a first switch for selectively supplying a voltage from the first voltage source to the first electrode; a second switch for selectively supplying a voltage from the second voltage source to the first electrode; a first resistance circuit connected to a control terminal of the first switch; and a second resistance circuit connected to a control terminal of the second switch, the method comprising the steps of: measuring mass accuracy using a standard sample; and determining whether the measured mass accuracy of the standard sample is within a reference range. If the mass accuracy of the standard sample is not within a standard range, adjusting the resistance value of at least one of the first resistance circuit and the second resistance circuit so that the mass accuracy is within a standard range.

20. The method according to claim 19, wherein the adjustment amounts of the resistance values ​​of the first resistor circuit and the second resistor circuit are predetermined according to a mass accuracy pattern, and the method further includes a step of determining the adjustment amounts of the resistance values ​​of the first resistor circuit and the second resistor circuit based on the measurement pattern of the mass accuracy of the measured standard sample.

21. The mass spectrometer according to claim 1, wherein, when an ion is trapped by the ion trap mechanism, the second electrode is set to ground potential, and, when a specific ion is ejected from the ion trap mechanism, a voltage having a frequency corresponding to the specific ion is applied from the voltage generating circuit to the second electrode.

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