Time-of-flight mass spectrometer and analysis method

Abstract

The present invention relates to a time-of-flight mass spectrometer comprising: electrodes to which a high DC voltage is applied in order to form a flight space for ions; and a high-voltage power supply device for applying the high voltage to the electrodes. The high-voltage power supply device includes a high-voltage generating circuit for generating the high voltage; and a voltage control circuit selectively set to a first mode and a second mode, wherein the first mode controls the high-voltage generating circuit so that the high voltage has a first convergence response and a first stability, and the second mode controls the high-voltage generating circuit so that the high voltage has a second convergence response that is lower than the first convergence response and a second stability that is higher than the first stability.

Description

Technical Field

[0001] The present invention relates to a time-of-flight mass spectrometer including a high-voltage power supply device and an analysis method. Background Art

[0002] A time-of-flight mass spectrometer (TOFMS) has a flight tube. To propel ionized components in a sample through the tube, a stable high voltage is applied to the tube via a high-voltage power supply (e.g., Patent Document 1). Furthermore, the polarity of the applied voltage can be switched depending on the polarity of the ions being analyzed.

[0003] The high-voltage power supply device described in Patent Document 1 includes a voltage generator, an auxiliary voltage generator, and a capacitor. While the voltage generator applies a negative voltage to the flight tube, the auxiliary voltage generator charges the capacitor to a positive potential with a high current. When the polarity of the applied voltage switches from negative to positive, the flight tube is disconnected from the voltage generator, and a high current is supplied from the capacitor to the flight tube. This rapidly charges the electrostatic capacitance of the flight tube to a positive potential. The flight tube is then disconnected from the capacitor and connected to the voltage generator, which generates a positive voltage. This results in a stable positive voltage being applied to the flight tube. This shortens the rise time of the voltage applied to the flight tube.

[0004] Prior art literature

[0005] Patent Document 1: International Publication No. 2018 / 066064 Summary of the Invention

[0006] Technical problem to be solved by the invention

[0007] However, depending on the analysis object or purpose, higher resolution analysis results are sometimes required. In such cases, it is desirable to further improve the stability of the voltage applied to the flight tube or other electrodes. On the other hand, depending on the analysis object or purpose, it is sometimes desirable to switch the voltage applied to the flight tube or other electrodes quickly. Hereinafter, the performance of the voltage converging to the desired value within a short period of time during voltage switching is referred to as convergence responsiveness. On the other hand, the performance of minimal voltage fluctuation is referred to as stability.

[0008] Convergence responsiveness and stability in a high-voltage power supply device are in a trade-off relationship. Therefore, if convergence responsiveness increases, stability decreases, and if stability increases, convergence responsiveness decreases.

[0009] An object of the present invention is to provide a time-of-flight mass spectrometer and an analysis method including a high voltage power supply device capable of generating a high voltage with improved convergence responsiveness or a high voltage with improved stability according to an analysis object or analysis purpose.

[0010] Solutions for solving the above technical problems

[0011] A time-of-flight mass spectrometer of one embodiment of the present invention comprises: an electrode, to which a high DC voltage is applied in order to form a flight space for ions; a high-voltage power supply device, which applies the high voltage to the electrode, and the high-voltage power supply device includes: a high-voltage generating circuit, which generates the high voltage; a voltage control circuit, which is selectively set to a first mode and a second mode, wherein the first mode controls the high-voltage generating circuit so that the high voltage has a first convergence responsiveness and a first stability, and the second mode controls the high-voltage generating circuit so that the high voltage has a second convergence responsiveness lower than the first convergence responsiveness and a second stability higher than the first stability.

[0012] According to another embodiment of the present invention, an analysis method is an analysis method using a time-of-flight mass spectrometer equipped with a high-voltage power supply device, wherein the high-voltage power supply device applies a high voltage to an electrode in order to form a flight space for ions, and comprises: a step of selectively setting the high-voltage power supply device to a first mode and a second mode, wherein the first mode controls the high-voltage power supply device so that the high voltage has a first convergence responsiveness and a first stability, and the second mode controls the high-voltage power supply device so that the high voltage has a second convergence responsiveness lower than the first convergence responsiveness and a second stability higher than the first stability; and a step of performing mass analysis on an analysis object using the time-of-flight mass spectrometer in the set first mode or second mode.

[0013] Effects of the Invention

[0014] According to the present invention, a time-of-flight mass spectrometer and an analysis method can be provided, which include a high voltage power supply device that can generate a high voltage with improved convergence responsiveness or a high voltage with improved stability according to the analysis object or analysis purpose. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a diagram showing the configuration of a time-of-flight mass spectrometer according to one embodiment of the present invention.

[0016] Figure 2 This is a circuit diagram showing the configuration of a positive voltage generating section of a high voltage power supply device.

[0017] Figure 3This is a waveform diagram showing the case where the high voltage can be switched from negative to positive.

[0018] Figure 4 This is a waveform diagram showing a temporal change in the high voltage when the high voltage can be repeatedly switched between positive and negative in the convergence responsiveness priority mode.

[0019] Figure 5 3 is a waveform diagram showing a temporal change in the high voltage when the high voltage can be switched from negative to positive in the stability priority mode.

[0020] Figure 6 This is a block diagram showing the functional configuration of a switching control unit in a high-voltage power supply device.

[0021] Figure 7 This is a flowchart showing an example of the mode setting operation of the switching control unit.

[0022] Figure 8 : is a circuit diagram showing another example of the configuration of the voltage control circuit.

[0023] Figure 9 : is a circuit diagram showing another example of the configuration of the voltage control circuit. DETAILED DESCRIPTION

[0024] Hereinafter, a time-of-flight mass spectrometer and an analysis method according to embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0025] (1) Configuration of a time-of-flight mass spectrometer

[0026] Figure 1 This figure shows the configuration of a time-of-flight mass spectrometer according to one embodiment of the present invention. The time-of-flight mass spectrometer 1 includes a mass spectrometer 2, a high-voltage power supply 3, a display 4, and an operating unit 5. The high-voltage power supply 3 of this embodiment can selectively operate in a convergence-response-priority mode or a stability-priority mode. Details of the convergence-response-priority and stability-priority modes will be described later.

[0027] The mass spectrometry unit 2 includes an ionization chamber 20 , a first intermediate chamber 21 , a second intermediate chamber 22 , a third intermediate chamber 23 , and an analysis chamber 24 .

[0028] The ionization chamber 20 includes an ESI probe (electrospray ionization probe) 201 and a capillary 202. The ESI probe 201 ionizes components of the liquid sample within the ionization chamber 20 by imparting an electric charge to the liquid sample while spraying the sample. Ions within the ionization chamber 20 are introduced into the first intermediate chamber 21 via the capillary 202.

[0029] The first intermediate chamber 21 includes a first ion guide 211. The first ion guide 211 converges the ions introduced into the first intermediate chamber 21 and guides them toward the second intermediate chamber 22. The second intermediate chamber 22 includes a second ion guide 221. The second ion guide 221 further converges the ions introduced into the second intermediate chamber 22 and guides them toward the third intermediate chamber 23.

[0030] The third intermediate chamber 23 includes a quadrupole mass filter 231, a collision cell 232, and an ion guide 234. The collision cell 232 includes a multipole ion guide 233. The quadrupole mass filter 231 separates ions introduced into the third intermediate chamber 23 based on their mass-to-charge ratio and introduces the separated ions into the collision cell 232. A collision gas is supplied to the collision cell 232 as needed. Ions emitted from the collision cell 232 by the multipole ion guide 233 are introduced into the analysis chamber 24 via the ion guide 234.

[0031] The analysis chamber 24 includes an ion transport electrode 241, an orthogonal accelerating electrode 242, an accelerating electrode 243, a reflecting electrode 244, a detector 245, a flight tube 246, and a backing plate 247. The orthogonal accelerating electrode 242 is composed of an electrode 242A and an electrode 242B. The reflecting electrode 244 is composed of an electrode 244A and an electrode 244B.

[0032] Ions introduced into the analysis chamber 24 are directed between electrodes 242A and 242B of the orthogonal accelerating electrode 242 via the ion transport electrode 241. Here, the ions' travel direction is bent at a substantially right angle by the orthogonal accelerating electrode 242. The accelerating electrode 243 accelerates the ions and directs them into the flight tube 246. The ions within the flight tube 246 travel within the flight space at a velocity corresponding to their mass-to-charge ratio.

[0033] Ions flying in the flight space are gradually decelerated by the reflector electrode 244 and the spacer 247 and return in a parabolic shape. As a result, the ions arrive at the detector 245 in ascending order of mass-to-charge ratio. The detector 245 is, for example, a secondary electron multiplier tube.

[0034] The detector 245 detects the ions that have passed through the flight tube 246. Based on the output signal of the detector 245, the flight time of each ion is converted into a mass-to-charge ratio (m / z) using the following formula (1) to generate a mass spectrum. Here, t is the flight time, L is the flight distance, and N is the mass spectrum. A is Avogadro's constant, e is the elementary charge, V is the voltage applied to the flight tube 246 by the high voltage power supply device 3, and m / z is the mass-to-charge ratio.

[0035] [Number 1]

[0036]

[0037] As shown in equation (1), the ion flight time t varies depending on the voltage applied to the flight tube 246. Therefore, if the voltage applied to the flight tube 246 is not stable, the flight time t fluctuates, and a high-resolution mass spectrum cannot be obtained. Therefore, in the case of mass analysis requiring high resolution, a highly stable voltage must be applied to the flight tube 246.

[0038] The high-voltage power supply device 3 includes a switching control unit 30, a positive voltage generator 31, a negative voltage generator 32, a positive voltage selection switch 33, and a negative voltage selection switch 34. The switching control unit 30 is implemented, for example, by a CPU (central processing unit), RAM (random access memory), ROM (read-only memory), and a storage device. The display unit 4 and the operating unit 5 are connected to the switching control unit 30.

[0039] The display unit 4 includes a liquid crystal display or an organic EL (electroluminescence) display. The display unit 4 displays various information and images. The operation unit 5 includes a keyboard and a pointing device. The operation unit 5 is used to perform operations such as selection and designation.

[0040] Alternatively, the display unit 4 and the operating unit 5 may be configured as a touch panel display. In this case, the operating unit 5 is displayed as an image on the display unit 4. The user can perform operations such as selection and designation by touching a predetermined portion of the image displayed on the display unit 4.

[0041] The positive voltage generator 31 generates a positive high voltage VP from an output node NP. The negative voltage generator 32 generates a negative high voltage VN from an output node NN. The output node NP of the positive voltage generator 31 is connected to the output node Nout via a positive voltage selection switch 33. The output node NN of the negative voltage generator 32 is connected to the output node Nout via a negative voltage selection switch 34. The positive voltage selection switch 33 and the negative voltage selection switch 34 can be implemented using switching elements such as bipolar transistors, field-effect transistors, or mechanical switches. In this embodiment, the output node Nout is connected to the flight tube 246. The flight tube 246 functions as an electrode.

[0042] The switching control unit 30 supplies a mode setting signal MS to the positive voltage generating unit 31 and the negative voltage generating unit 32 based on the operation of the operating unit 5. The switching control unit 30 also supplies a positive voltage selection signal SP to the positive voltage selection switch 33 and a negative voltage selection signal SN to the negative voltage selection switch 34.

[0043] When the mode setting signal MS is in the first state (for example, a logic high level), the positive voltage generating unit 31 and the negative voltage generating unit 32 are set to a convergence responsiveness priority mode. When the mode setting signal MS is in the second state (for example, a logic low level), the positive voltage generating unit 31 and the negative voltage generating unit 32 are set to a stability priority mode.

[0044] The positive voltage selection signal SP and the negative voltage selection signal SN change to opposite states. When the positive voltage selection signal SP is in the on state (e.g., a logic high level), the negative voltage selection signal SN is in the off state (e.g., a logic low level). Conversely, when the positive voltage selection signal SP is in the off state (e.g., a logic low level), the negative voltage selection signal SN is in the on state (e.g., a logic high level).

[0045] When the positive voltage selection signal SP turns on, the positive voltage selection switch 33 turns on. At this time, the negative voltage selection signal SN turns off, and the negative voltage selection switch 34 turns off. As a result, the positive high voltage VP is output from the output node Nout as the high voltage HV. The high voltage HV is, for example, +5 to +10 kV or -5 to -10 kV.

[0046] When the negative voltage selection signal SN is turned on, the negative voltage selection switch 34 is turned on. At this time, the positive voltage selection signal SP is turned off, and the positive voltage selection switch 33 is turned off. As a result, the negative high voltage VN is output as the high voltage HV from the output node Nout.

[0047] (2) Configuration of the Positive Voltage Generator 31

[0048] Figure 2 It shows Figure 1 The circuit diagram of the positive voltage generating unit 31 of the high voltage power supply device 3 is shown in FIG. Figure 2 As shown, the positive voltage generating unit 31 includes a high voltage generating circuit 311 and a voltage control circuit 312 .

[0049] High-voltage generating circuit 311 includes an inverter circuit 315, a boost transformer 316, and a boost circuit 317. Boost circuit 317 is, for example, a Cockcroft-Walton boost circuit. A positive DC voltage Vp is supplied from a power supply circuit to inverter circuit 315. Inverter circuit 315 converts DC voltage Vp into an AC voltage. Boost transformer 316 boosts the AC voltage output from inverter circuit 315. Boost circuit 317 further boosts the AC voltage boosted by boost transformer 316 and converts it into a DC voltage, outputting a positive DC high voltage VP to output node NP.

[0050] The voltage control circuit 312 includes an operational amplifier OP, switches SW1 and SW2, capacitors C1 and C2, and resistors R1, R2, R11, R12, and R13. Switches SW1 and SW2 may be bipolar transistors, field effect transistors, or mechanical switches.

[0051] Resistor R11 is connected between output node NP and node N1. Resistor R12 is connected between node N1 and node N2 receiving ground potential GND. Resistor R13 is connected between node N1 and node N3. Resistors R11 and R12 divide high voltage VP to generate low voltage VI1 at node N1.

[0052] Node N3 is connected to the inverting input terminal of the operational amplifier OP. Reference voltage generation circuit 318 generates a constant positive reference voltage VR. The reference voltage VR generated by reference voltage generation circuit 318 is supplied to the non-inverting input terminal. Furthermore, the output terminal of the operational amplifier OP is connected to node N4.

[0053] A switch SW1 and a negative feedback circuit 313 are connected in series between nodes N3 and N4. Furthermore, a switch SW2 and a negative feedback circuit 314 are connected in series between nodes N3 and N4. Negative feedback circuit 313 includes a resistor R1 and a capacitor C1 connected in series. Negative feedback circuit 314 includes a resistor R2 and a capacitor C2 connected in series.

[0054] In this embodiment, the capacitance value of capacitor C1 of negative feedback circuit 313 is set to be smaller than the capacitance value of capacitor C2 of negative feedback circuit 314. The resistance value of resistor R1 of negative feedback circuit 313 is set to be larger than the resistance value of resistor R2 of negative feedback circuit 314. Thus, negative feedback circuit 313 and negative feedback circuit 314 have different control circuit constants. In this embodiment, negative feedback circuit 313 has a control circuit constant that prioritizes convergence responsiveness, while negative feedback circuit 314 has a control circuit constant that prioritizes stability.

[0055] The switching control unit 30 supplies the mode setting signal MS as the mode setting signal MS11 to the switch SW1. Furthermore, the switching control unit 30 supplies the mode setting signal MS to the inverter circuit IV. The inverter circuit IV inverts the mode setting signal MS and supplies the inverted signal as the mode setting signal MS12 to the switch SW2. As a result, the mode setting signal MS11 and the mode setting signal MS12 change to opposite states. When the mode setting signal MS11 is in the first state (e.g., a logic high level), the mode setting signal MS12 is in the second state (e.g., a logic low level). Conversely, when the mode setting signal MS11 is in the second state (e.g., a logic low level), the mode setting signal MS12 is in the first state (e.g., a logic high level).

[0056] Thus, when mode setting signal MS is in the first state, switch SW1 is turned on and switch SW2 is turned off. Consequently, negative feedback circuit 313 is connected to node N3, while negative feedback circuit 314 is disconnected from node N3. Conversely, when mode setting signal MS is in the second state, switch SW1 is turned off and switch SW2 is turned on. Consequently, negative feedback circuit 313 is disconnected from node N3, while negative feedback circuit 314 is connected to node N3.

[0057] Operational amplifier OP inverts and amplifies the difference between voltage VI2 at node N3 and reference voltage VR, and supplies the amplified voltage as feedback signal FB to inverter circuit 315. Inverter circuit 315 increases or decreases the output voltage to step-up transformer 316 based on feedback signal FB, so that high voltage VP converges to a constant value. In this case, as will be described later, the change in high voltage VP differs depending on whether negative feedback circuit 313 is connected between nodes N3 and N4 or negative feedback circuit 314 is connected between nodes N3 and N4.

[0058] In this embodiment, the common operational amplifier OP and the negative feedback circuit 313 constitute the first feedback control circuit 321, and the common operational amplifier OP and the negative feedback circuit 314 constitute the second feedback control circuit 322. Figure 1 The convergence responsiveness priority mode or the stability priority mode is selected by operating unit 5, and the mode setting signal MS output from the switching control unit 30 is switched to the first state or the second state. Thus, if the convergence responsiveness priority mode is selected by operating unit 5, switch SW1 is turned on, and if the stability priority mode is selected, switch SW2 is turned on.

[0059] In addition to the following aspects, Figure 1 The negative voltage generating unit 32 is configured as follows Figure 2 The positive voltage generating unit 31 has the same structure as the negative voltage generating unit 32. Figure 1 The node NN outputs a negative DC high voltage VN. In addition, in the negative voltage generating unit 32, the reference voltage generating circuit 318 generates a constant negative reference voltage VR.

[0060] (3) Convergence responsiveness priority mode and stability priority mode

[0061] Figure 3 1 is a waveform diagram when the high voltage HV at the output node Nout switches from negative to positive. Figure 3The horizontal axis represents time, and the vertical axis represents high voltage HV. The dotted line shows waveform WR, which illustrates the change in high voltage HV in the convergence responsiveness priority mode. The solid line shows waveform WS, which illustrates the change in high voltage HV in the stability priority mode. Part B shows an enlarged view of part A of waveforms WR and WS.

[0062] The waveform WR rises faster in the convergence-responsiveness priority mode than in the stability-priority mode. Therefore, in the convergence-responsiveness priority mode, the waveform WR of the high voltage HV substantially converges to the target value Va at time t1. Therefore, in the convergence-responsiveness priority mode, analysis can be started at time t1.

[0063] On the other hand, in the stability priority mode, the waveform WS of the high voltage HV substantially converges to the target value Va at time point t2 later than time point t1. Therefore, according to the stability priority mode, analysis can be started at time point t2.

[0064] Thus, in the convergence responsiveness priority mode, the high voltage HV converges substantially to the target value Va in a shorter time than in the stability priority mode. Therefore, the convergence responsiveness of the high voltage HV is higher in the convergence responsiveness priority mode than in the stability priority mode.

[0065] As shown in part B, the fluctuation (ringing) of waveform WS after time t2 in the stability priority mode is smaller than the fluctuation of waveform WR after time t1 in the convergence responsiveness priority mode. Therefore, the stability of high voltage HV is higher in the stability priority mode than in the convergence responsiveness priority mode.

[0066] Figure 4 : is a waveform diagram showing a temporal change of the high voltage HV when the high voltage HV is repeatedly switched between positive and negative in the convergence responsiveness priority mode. Figure 4 In FIG, the solid arrow shows the analyzable period TA. Figure 4 As shown, in the convergence responsiveness priority mode, the high voltage HV can be repeatedly switched between the positive target value +Va and the negative target value -Va in a short time.

[0067] When the user analyzes both positive ions and negative ions, the polarity of the high voltage HV can be repeatedly switched. In this case, the convergence response priority mode enables analysis of positive ions and negative ions in a short time.

[0068] Figure 5 : is a waveform diagram showing the temporal change of the high voltage HV when the high voltage HV is switched from negative to positive in the stability priority mode. Figure 5 In FIG, the solid arrow shows the analyzable period TA. Figure 5As shown, in the stability priority mode, it takes longer for the high voltage HV to substantially converge to the target value Va than in the convergence responsiveness priority mode, but after the high voltage HV converges to the target value Va, the stability of the high voltage HV is higher.

[0069] When the user analyzes either positive ions or negative ions, the polarity of the high voltage HV cannot be repeatedly switched. In this case, the stability priority mode can provide analysis results with high resolution.

[0070] (4) Functional Configuration of Switching Control Unit 30

[0071] Figure 6 This is a block diagram illustrating the functional configuration of the switching control unit 30 in the high-voltage power supply device 3. The switching control unit 30 includes a mode setting unit 301 and a voltage polarity switching unit 302. The functions of the mode setting unit 301 and the voltage polarity switching unit 302 are implemented, for example, by a CPU (not shown) executing a control program, a computer program stored on a storage medium (recording medium) in a storage device. Some or all of the components of the switching control unit 30 may be implemented as hardware, such as electronic circuits.

[0072] The user selects either the convergence-response-priority mode or the stability-priority mode using the operating unit 5. The mode setting unit 301 switches the state of the mode setting signal MS provided to the positive voltage generating unit 31 and the negative voltage generating unit 32 based on the convergence-response-priority mode or the stability-priority mode selected using the operating unit 5.

[0073] When the user selects the convergence responsiveness priority mode, the mode setting signal MS is in the first state. Consequently, the positive voltage generator 31 and the negative voltage generator 32 are set to the convergence responsiveness priority mode. When the user selects the stability priority mode, the mode setting signal MS is in the second state. Consequently, the positive voltage generator 31 and the negative voltage generator 32 are set to the stability priority mode.

[0074] The user selects positive, negative, or a positive-negative switching polarity as the polarity of the high voltage HV using the operating unit 5. The voltage polarity switching unit 302 switches the states of the positive voltage selection signal SP that can be supplied to the positive voltage selection switch 33 and the negative voltage selection signal SN that can be supplied to the negative voltage selection switch 34 based on the polarity of the high voltage HV selected using the operating unit 5.

[0075] When positive is selected as the polarity of the high voltage HV, the positive voltage selection signal SP is turned on and the negative voltage selection signal SN is turned off. This causes the high voltage HV to become positive. When negative is selected as the polarity of the high voltage HV, the positive voltage selection signal SP is turned off and the negative voltage selection signal SN is turned on. This causes the high voltage HV to become negative. When positive-negative switching is selected as the polarity of the high voltage HV, the high voltage HV is repeatedly switched between positive and negative within a certain period.

[0076] Information on the convergence response priority mode or the stability priority mode selected using the operation unit 5 and the polarity of the high voltage HV is displayed on the display unit 4 .

[0077] (5) Mode setting action

[0078] Figure 7 This is a flowchart illustrating an example of the mode setting operation of the switching control unit 30. The mode setting operation of the switching control unit 30 is performed, for example, by the CPU executing a control program stored in a storage device on RAM. Furthermore, in this example, in the convergence responsiveness priority mode, the polarity of the high voltage HV can be switched between positive and negative.

[0079] The mode setting unit 301 determines whether the stability priority mode is selected via the operating unit 5 (step S1). If the stability priority mode is selected, the mode setting unit 301 sets the mode setting signal MS to the second state, turning on the switches SW2 in the positive voltage generating unit 31 and the negative voltage generating unit 32 (step S2). As a result, the voltage control circuit 312 is set to the stability priority mode.

[0080] Next, the voltage polarity switching unit 302 determines whether the polarity of the high voltage HV is selected as positive via the operating unit 5 (step S3). If positive is selected as the polarity of the high voltage HV, the voltage polarity switching unit 302 turns on the positive voltage selection switch 33 by turning on the positive voltage selection signal SP (step S4). At this time, the negative voltage selection signal SN turns off, and the negative voltage selection switch 34 is opened. As a result, the polarity of the high voltage HV becomes positive. The user performs quality analysis on the analysis object in the stability priority mode.

[0081] In step S3, if negative is selected as the polarity of high voltage HV, voltage polarity switching unit 302 turns on negative voltage selection signal SN, thereby turning on negative voltage selection switch 34 (step S5). At this point, positive voltage selection signal SP turns off, and positive voltage selection switch 33 is opened. As a result, the polarity of high voltage HV becomes negative. The user performs quality analysis on the analysis object in stability-priority mode.

[0082] When the convergence responsiveness priority mode is selected in step S1, the mode setting unit 301 sets the mode setting signal MS to the first state, turning on the switches SW1 in the positive voltage generating unit 31 and the negative voltage generating unit 32 (step S6). As a result, the voltage control circuit 312 is set to the convergence responsiveness priority mode.

[0083] The voltage polarity switching unit 302 alternately turns on the positive voltage selection signal SP and the negative voltage selection signal SN, thereby alternately turning on the positive voltage selection switch 33 and the negative voltage selection switch 34. This alternately switches the polarity of the high voltage HV between positive and negative (step S7). The user performs quality analysis on the analysis object in the convergence response priority mode.

[0084] Next, the mode setting unit 301 determines whether a command to terminate the mass analysis operation has been received from the operating unit 5 (step S8). If no command to terminate the mass analysis operation has been received, the process returns to step S1. If a command to terminate the mass analysis operation has been received, the mass analysis operation is terminated. Furthermore, in the convergence responsiveness priority mode, the high voltage HV can be set to positive or negative at the user's option.

[0085] (6) Effects of Implementation

[0086] In the time-of-flight mass spectrometer 1 of the present embodiment, the voltage control circuit 312 of the high-voltage power supply device 3 is selectively set to a convergence responsiveness priority mode or a stability priority mode. In the convergence responsiveness priority mode, the high voltage generating circuit 311 is controlled so that the high voltage HV has a higher convergence responsiveness. In this case, the high voltage HV converges to the target value +Va or the target value -Va at a high speed. Thus, even in the case where the value of the high voltage HV applied to the flight tube 246 can be repeatedly switched, analysis can be performed in a short time. In the stability priority mode, the high voltage generating circuit 311 is controlled so that the high voltage HV has a higher stability. In this case, the variation of the high voltage HV that converges to the target value Va is small. Thus, an analysis result with high resolution can be obtained.

[0087] In this way, the user can generate a high voltage HV with improved convergence responsiveness or a high voltage HV with improved stability according to the analysis object or analysis purpose by selecting the convergence responsiveness priority mode or the stability priority mode.

[0088] Furthermore, in the high-voltage power supply device 3, the high voltage HV can be controlled to target values ​​+Va and -Va with high precision by a first feedback control circuit 321 including a negative feedback circuit 313 and a second feedback control circuit 322 including a negative feedback circuit 314. In this case, by setting the magnitude relationship between the capacitance values ​​of capacitors C1 and C2, and the magnitude relationship between the resistance values ​​of resistors R1 and R2, the convergence responsiveness and stability in the convergence responsiveness priority mode can be made different from the convergence responsiveness and stability in the stability priority mode with a simple configuration. Furthermore, since a common operational amplifier OP is used for controlling the high voltage HV in both the convergence responsiveness priority mode and the stability priority mode, the number of components and component costs can be reduced.

[0089] Furthermore, the capacitance value of the capacitor C1 of the negative feedback circuit 313 and the capacitance value of the capacitor C2 of the negative feedback circuit 314 are set separately, and the resistance value of the resistor R1 of the negative feedback circuit 313 and the resistance value of the resistor R2 of the negative feedback circuit 314 are set separately. This makes it possible to easily and variably set the convergence responsiveness and stability of the high voltage HV in the convergence responsiveness priority mode and the stability priority mode.

[0090] (7) Other implementation methods

[0091] (a) In the above embodiment, the high voltage power supply 3 is used to apply the high voltage HV to the flight tube 246, which is one type of electrode. However, the high voltage power supply 3 can also be used to apply high voltage to other electrodes. For example, the high voltage power supply 3 can be used to apply the high voltage to the ion transport electrode 241, the orthogonal accelerating electrode 242, the accelerating electrode 243, the reflecting electrode 244, or the backing plate 247.

[0092] (b) The configuration of the voltage control circuit 312 is not limited to Figure 2 composition. Figure 8 3 is a circuit diagram showing another example of the configuration of the voltage control circuit 312. Figure 8 In the voltage control circuit 312, the negative feedback circuit 314 includes a capacitor C3 in addition to the resistor R2 and the capacitor C2. The capacitor C3 is connected in parallel to the series connection circuit of the resistor R2 and the capacitor C2. Figure 8 The other parts of the voltage control circuit 312 are composed of Figure 2 The voltage control circuit 312 has the same structure. Figure 8 In the voltage control circuit 312, the capacitor C3 removes high-frequency noise of the high voltage HV. Therefore, the negative feedback circuit 314 can further improve the stability of the high voltage HV.

[0093] (c) Figure 93 is a circuit diagram showing another example of the configuration of the voltage control circuit 312. Figure 9 The voltage control circuit 312 and Figure 2 Identical components of voltage control circuit 312 are denoted by the same reference numerals. Voltage control circuit 312 includes resistors R11 and R12, a switching control unit 30, a switch SW, a first feedback control circuit 321, a second feedback control circuit 322, and a reference voltage generation circuit 318. Switch SW has contacts a, b, and c. A mode setting signal MS is provided to switch SW via switching control unit 30. Contact a of switch SW is connected to node N1.

[0094] First feedback control circuit 321 includes an operational amplifier OP1, a resistor R3, and a negative feedback circuit 313. Resistor R3 is connected between contact b of switch SW and node N5. Node N5 is connected to the inverting input terminal of operational amplifier OP1. A reference voltage VR generated by reference voltage generation circuit 318 is supplied to the non-inverting input terminal of operational amplifier OP1. Furthermore, an output terminal of operational amplifier OP1 is connected to node N4. Negative feedback circuit 313 is connected between node N5 and node N4.

[0095] Second feedback control circuit 322 includes operational amplifier OP2, resistor R4, and negative feedback circuit 314. Resistor R4 is connected between contact c of switch SW and node N6. Node N6 is connected to the inverting input terminal of operational amplifier OP2. Reference voltage VR generated by reference voltage generation circuit 318 is supplied to the non-inverting input terminal of operational amplifier OP2. Furthermore, the output terminal of operational amplifier OP2 is connected to node N4. Negative feedback circuit 314 is connected between node N6 and node N4.

[0096] In this example, the capacitance value of capacitor C1 of negative feedback circuit 313 is also set to be smaller than the capacitance value of capacitor C2 of negative feedback circuit 314. When mode setting signal MS is in the first state, contact a of switch SW is connected to contact b. Thus, voltage control circuit 312 is set to a mode prioritizing convergence responsiveness. On the other hand, when mode setting signal MS is in the second state, contact a of switch SW is connected to contact c. Thus, voltage control circuit 312 is set to a mode prioritizing stability. Figure 9 The configuration and operation of other parts of the voltage control circuit 312 are similar to those of Figure 2 The structure and operation of the voltage control circuit 312 are the same.

[0097] (d) In the above embodiment, the voltage control circuit 312 is selectively set to the convergence responsiveness priority mode and the stability priority mode. However, the voltage control circuit 312 may be set to a third mode different from the convergence responsiveness priority mode and the stability priority mode. For example, a third feedback control circuit may be further provided in the voltage control circuit 312. The third feedback control circuit may include, for example, a capacitor having a different capacitance value from the capacitor C1 of the first feedback control circuit 321 and the capacitor C2 of the second feedback control circuit 322.

[0098] (e) In the above embodiment, the capacitance value of capacitor C1 of negative feedback circuit 313 is set to be smaller than the capacitance value of capacitor C2 of negative feedback circuit 314, and the resistance value of resistor R1 of negative feedback circuit 313 is set to be larger than the resistance value of resistor R2 of negative feedback circuit 314, but the present invention is not limited to this.

[0099] For example, the capacitance value of the capacitor C1 of the negative feedback circuit 313 can be set to be smaller than the capacitance value of the capacitor C2 of the negative feedback circuit 314, and the resistance value of the resistor R1 of the negative feedback circuit 313 can be set to be equal to the resistance value of the resistor R2 of the negative feedback circuit 314.

[0100] In addition, the capacitance value of the capacitor C1 of the negative feedback circuit 313 can be set to be much smaller than the capacitance value of the capacitor C2 of the negative feedback circuit 314, and the resistance value of the resistor R1 of the negative feedback circuit 313 can be set to be smaller than the resistance value of the resistor R2 of the negative feedback circuit 314.

[0101] In addition, the resistance value of the resistor R1 of the negative feedback circuit 313 can be set to be greater than the resistance value of the resistor R2 of the negative feedback circuit 314, and the capacitance value of the capacitor C1 of the negative feedback circuit 313 can be set to be equal to the capacitance value of the capacitor C2 of the negative feedback circuit 314.

[0102] In addition, the resistance value of the resistor R1 of the negative feedback circuit 313 can be set to be much larger than the resistance value of the resistor R2 of the negative feedback circuit 314, and the capacitance value of the capacitor C1 of the negative feedback circuit 313 can be set to be larger than the capacitance value of the capacitor C2 of the negative feedback circuit 314.

[0103] (8) Correspondence between the constituent elements of the claims and the elements of the embodiments

[0104] The following describes examples of correspondence between the various components of the claims and the various elements of the embodiments. In the above embodiment, flight tube 246 is an example of an electrode, convergence responsiveness priority mode is an example of the first mode, stability priority mode is an example of the second mode, negative feedback circuit 313 is an example of a first negative feedback control circuit, negative feedback circuit 314 is an example of a second negative feedback circuit, positive voltage selection switch 33 and negative voltage selection switch 34 are examples of connection switching units, capacitor C1 is an example of a first capacitance component, capacitor C2 is an example of a second capacitance component, resistor R1 is an example of a first resistance component, and resistor R2 is an example of a second resistance component. Operational amplifier OP is an example of a common operational amplifier, operational amplifier OP1 is an example of a first operational amplifier, and operational amplifier OP2 is an example of a second operational amplifier.

[0105] (9) Plan

[0106] Those skilled in the art will appreciate that the aforementioned exemplary embodiments are specific examples of the following aspects.

[0107] (Item 1) A time-of-flight mass spectrometer according to one embodiment may include:

[0108] Electrodes, to which a high DC voltage is applied in order to create a flight space for ions;

[0109] a high voltage power supply device for applying the high voltage to the electrodes;

[0110] The high voltage power supply device comprises:

[0111] A high voltage generating circuit, generating the high voltage;

[0112] A voltage control circuit is selectively set to a first mode and a second mode, wherein the first mode controls the high voltage generating circuit so that the high voltage has a first convergence responsiveness and a first stability, and the second mode controls the high voltage generating circuit so that the high voltage has a second convergence responsiveness lower than the first convergence responsiveness and a second stability higher than the first stability.

[0113] According to the time-of-flight mass spectrometer described in item 1, the voltage control circuit is selectively set to the first mode or the second mode. In the first mode, the high voltage generating circuit is controlled so that the high voltage has a high convergence responsiveness. In this case, the high voltage converges to the target value at a high speed. Thus, even in the case where the value of the high voltage applied to the electrode can be repeatedly switched, analysis can be performed in a short time. In the second mode, the high voltage generating circuit is controlled so that the high voltage has a high stability. In this case, the variation of the high voltage that converges to the target value is small. Thus, an analysis result with high resolution can be obtained.

[0114] As a result, the user can generate a high voltage with improved stability or a high voltage with improved convergence responsiveness according to the analysis object or analysis purpose by selecting the first mode or the second mode.

[0115] (Item 2) In the time-of-flight mass spectrometer described in Item 1, the voltage control circuit may include:

[0116] a first feedback control circuit for performing feedback control on the high voltage generating circuit so that the value of the high voltage converges to a target voltage value with the first convergence responsiveness and the first stability;

[0117] a second feedback control circuit for performing feedback control on the high voltage generating circuit so that the value of the high voltage converges to the target voltage value with the second convergence responsiveness and the second stability;

[0118] The selection circuit selectively operates the first feedback control circuit in the first mode and selectively operates the second feedback control circuit in the second mode.

[0119] According to the time-of-flight mass spectrometer described in Item 2, since the first feedback control circuit or the second feedback control circuit selectively operates, the high voltage can be controlled with high precision in the first mode and the second mode.

[0120] (Item 3) In the time-of-flight mass spectrometer described in Item 2, it may be,

[0121] The first feedback control circuit includes a first capacitance component and a first resistance component.

[0122] The second feedback control circuit includes a second capacitance component and a second resistance component.

[0123] The magnitude relationship between the capacitance value of the first capacitance component and the capacitance value of the second capacitance component and the magnitude relationship between the resistance value of the first resistance component and the resistance value of the second resistance component are set so that the first feedback control circuit has the first convergence responsiveness and the first stability and the second feedback control circuit has the second convergence responsiveness and the second stability.

[0124] According to the time-of-flight mass spectrometer described in Item 3, by setting the magnitude relationship between the capacitance value of the first capacitance component and the capacitance value of the second capacitance component and the magnitude relationship between the resistance value of the first resistance component and the resistance value of the second resistance component, the first convergence responsiveness and the first stability in the first mode can be made different from the second convergence responsiveness and the second stability in the second mode with a simple structure.

[0125] (Item 4) In the time-of-flight mass spectrometer described in Item 3, it may be,

[0126] The first feedback control circuit and the second feedback control circuit include a common operational amplifier.

[0127] The first feedback control circuit includes a first negative feedback circuit connected to the operational amplifier.

[0128] The second feedback control circuit includes a second negative feedback circuit connected to the operational amplifier.

[0129] The first negative feedback circuit includes a series connection of the first capacitance component and the first resistance component.

[0130] The second negative feedback circuit includes a series connection of the second capacitance component and the second resistance component.

[0131] According to the time-of-flight mass spectrometer described in Item 4, by setting the capacitance value of the first capacitance component in the first negative feedback circuit and the capacitance value of the second capacitance component in the second negative feedback circuit, the first convergence response and the first stability in the first mode can be easily differentiated from the second convergence response and the second stability in the second mode. Furthermore, since a common operational amplifier is used for high voltage control in the first and second modes, the number of components and component costs can be reduced.

[0132] (Item 5) In the time-of-flight mass spectrometer described in Item 3, it may be,

[0133] The first feedback control circuit includes a first operational amplifier and a first negative feedback circuit connected to the first operational amplifier.

[0134] The second feedback control circuit includes a second operational amplifier and a second negative feedback circuit connected to the second operational amplifier.

[0135] The first negative feedback circuit includes a series connection of the first capacitance component and the first resistance component.

[0136] The second negative feedback circuit includes a series connection of the second capacitance component and the second resistance component.

[0137] According to the time-of-flight mass spectrometer described in Item 5, by setting the capacitance value of the first capacitance component in the first negative feedback circuit and the capacitance value of the second capacitance component in the second negative feedback circuit, the first convergence responsiveness and the first stability in the first mode can be easily made different from the second convergence responsiveness and the second stability in the second mode.

[0138] (Item 6) In the time-of-flight mass spectrometer described in Item 4 or 5, it may be,

[0139] The capacitance value of the first capacitance component is set smaller than the capacitance value of the second capacitance component so that the first feedback control circuit has the first convergence responsiveness and the first stability and the second feedback control circuit has the second convergence responsiveness and the second stability.

[0140] According to the time-of-flight mass spectrometer described in Item 6, by setting the capacitance value of the first capacitance component of the first feedback control circuit and the capacitance value of the second capacitance component of the second feedback control circuit, the convergence responsiveness and stability of the high voltage in the first mode and the second mode can be easily set.

[0141] (Item 7) In the time-of-flight mass spectrometer described in any one of Items 4 to 6, it may be that

[0142] The resistance value of the first resistance component is set to be larger than the resistance value of the second resistance component so that the first feedback control circuit has the first convergence responsiveness and the first stability and the second feedback control circuit has the second convergence responsiveness and the second stability.

[0143] According to the time-of-flight mass spectrometer described in Item 7, by setting the resistance value of the first resistance component of the first feedback control circuit and the resistance value of the second resistance component of the second feedback control circuit, the convergence responsiveness and stability of the high voltage in the first mode and the second mode can be easily set.

[0144] (Item 8) In the time-of-flight mass spectrometer described in any one of Items 1 to 7, it may be that

[0145] The high voltage power supply device comprises:

[0146] a positive voltage generating unit;

[0147] a negative voltage generating unit;

[0148] A connection switching unit selectively electrically connects one of the positive voltage generating unit and the negative voltage generating unit to the electrode,

[0149] The positive voltage generating unit and the negative voltage generating unit each include the high voltage generating circuit and the voltage control circuit.

[0150] The high voltage generating circuit of the positive voltage generating unit generates a positive high voltage as the high voltage,

[0151] The high voltage generating circuit of the negative voltage generating section generates a negative high voltage as the high voltage.

[0152] According to the time-of-flight mass spectrometer described in Item 8, the high-voltage power supply device is capable of selectively applying positive and negative high voltages having a first convergence responsiveness and a first stability to the electrode in the first mode, and is capable of selectively applying positive and negative high voltages having a second convergence responsiveness and a second stability to the electrode in the second mode.

[0153] In this case, when performing analysis while switching the polarity of the high voltage applied to the electrodes between positive and negative, the user can select the first mode or the second mode according to the analysis object or analysis purpose. Furthermore, when performing analysis while maintaining the polarity of the high voltage applied to the electrodes at either positive or negative, the user can select the first mode or the second mode according to the analysis object or analysis purpose.

[0154] (Item 9) The time-of-flight mass spectrometer according to any one of Items 1 to 8 may further include:

[0155] The switching control unit selectively switches the voltage control circuit to either the first mode or the second mode based on a user operation.

[0156] According to the time-of-flight mass spectrometer described in Item 9, the voltage control circuit is set to the first mode or the second mode based on the user's operation.

[0157] (Item 10) An analysis method using a time-of-flight mass spectrometer having a high-voltage power supply device for applying a high voltage to electrodes to form a flight space for ions may include:

[0158] The step of selectively setting the high voltage power supply device to a first mode and a second mode, wherein the first mode controls the high voltage power supply device so that the high voltage has a first convergence responsiveness and a first stability, and the second mode controls the high voltage power supply device so that the high voltage has a second convergence responsiveness lower than the first convergence responsiveness and a second stability higher than the first stability;

[0159] A step of performing mass analysis on an analysis object using the time-of-flight mass spectrometer in the set first mode or second mode.

[0160] According to the analysis method described in Item 10, the high-voltage power supply is selectively set to either the first mode or the second mode. In the first mode, the high-voltage power supply is controlled so that the high voltage has a high convergence stability. In this mode, the high voltage converges to the target value at a high speed. This allows analysis to be performed in a short time, even when the value of the high voltage applied to the electrode is repeatedly switched.

[0161] In the second mode, the high-voltage power supply is controlled so that the high voltage has high stability. In this case, the high voltage converges to the target value with little fluctuation, thus achieving high-resolution analysis results.

[0162] As a result, the user can generate a high voltage with improved stability or a high voltage with improved convergence responsiveness according to the analysis object or analysis purpose by selecting the first mode or the second mode.

Claims

1. A time-of-flight mass spectrometer, characterized in that: have: Electrodes to which a high DC voltage is applied in order to form a flight space for ions; a high voltage power supply device for applying the high voltage to the electrodes; The high voltage power supply device comprises: A high voltage generating circuit, generating the high voltage; A voltage control circuit is selectively set to a first mode and a second mode, wherein the first mode controls the high voltage generating circuit so that the high voltage has a first convergence responsiveness and a first stability, and the second mode controls the high voltage generating circuit so that the high voltage has a second convergence responsiveness lower than the first convergence responsiveness and a second stability higher than the first stability. The convergence responsiveness refers to the performance of the voltage converging to a desired value in a short time when the voltage is switched, and the stability refers to the performance of the voltage having a small fluctuation.

2. The time-of-flight mass spectrometer according to claim 1, wherein The voltage control circuit comprises: a first feedback control circuit for performing feedback control on the high voltage generating circuit so that the value of the high voltage converges to a target voltage value with the first convergence responsiveness and the first stability; a second feedback control circuit for performing feedback control on the high voltage generating circuit so that the value of the high voltage converges to the target voltage value with the second convergence responsiveness and the second stability; The selection circuit selectively operates the first feedback control circuit in the first mode and selectively operates the second feedback control circuit in the second mode.

3. The time-of-flight mass spectrometer according to claim 2, wherein The first feedback control circuit includes a first capacitance component and a first resistance component. The second feedback control circuit includes a second capacitance component and a second resistance component. The magnitude relationship between the capacitance value of the first capacitance component and the capacitance value of the second capacitance component and the magnitude relationship between the resistance value of the first resistance component and the resistance value of the second resistance component are set so that the first feedback control circuit has the first convergence responsiveness and the first stability and the second feedback control circuit has the second convergence responsiveness and the second stability.

4. The time-of-flight mass spectrometer according to claim 3, wherein The first feedback control circuit and the second feedback control circuit include a common operational amplifier. The first feedback control circuit includes a first negative feedback circuit connected to the operational amplifier. The second feedback control circuit includes a second negative feedback circuit connected to the operational amplifier. The first negative feedback circuit includes a series connection of the first capacitance component and the first resistance component. The second negative feedback circuit includes a series connection of the second capacitance component and the second resistance component.

5. The time-of-flight mass spectrometer according to claim 3, wherein The first feedback control circuit includes a first operational amplifier and a first negative feedback circuit connected to the first operational amplifier. The second feedback control circuit includes a second operational amplifier and a second negative feedback circuit connected to the second operational amplifier. The first negative feedback circuit includes a series connection of the first capacitance component and the first resistance component. The second negative feedback circuit includes a series connection of the second capacitance component and the second resistance component.

6. The time-of-flight mass spectrometer according to claim 4 or 5, wherein: The capacitance value of the first capacitance component is set smaller than the capacitance value of the second capacitance component so that the first feedback control circuit has the first convergence responsiveness and the first stability and the second feedback control circuit has the second convergence responsiveness and the second stability.

7. The time-of-flight mass spectrometer according to claim 4 or 5, wherein: The resistance value of the first resistance component is set to be larger than the resistance value of the second resistance component so that the first feedback control circuit has the first convergence responsiveness and the first stability and the second feedback control circuit has the second convergence responsiveness and the second stability.

8. The time-of-flight mass spectrometer according to any one of claims 1 to 5, wherein: The high voltage power supply device comprises: a positive voltage generating unit; a negative voltage generating unit; A connection switching unit selectively electrically connects one of the positive voltage generating unit and the negative voltage generating unit to the electrode, The positive voltage generating unit and the negative voltage generating unit each include the high voltage generating circuit and the voltage control circuit. The high voltage generating circuit of the positive voltage generating unit generates a positive high voltage as the high voltage, The high voltage generating circuit of the negative voltage generating section generates a negative high voltage as the high voltage.

9. The time-of-flight mass spectrometer according to any one of claims 1 to 5, wherein: It can also have: The switching control unit selectively switches the voltage control circuit to either the first mode or the second mode based on a user operation.

10. An analysis method using a time-of-flight mass spectrometer equipped with a high-voltage power supply device for applying a high voltage to electrodes to form a flight space for ions, comprising: The step of selectively setting the high voltage power supply device to a first mode and a second mode, wherein the first mode controls the high voltage power supply device so that the high voltage has a first convergence responsiveness and a first stability, and the second mode controls the high voltage power supply device so that the high voltage has a second convergence responsiveness lower than the first convergence responsiveness and a second stability higher than the first stability; a step of performing mass analysis on an analysis object using the time-of-flight mass spectrometer in the set first mode or second mode; The convergence responsiveness refers to the performance of the voltage converging to a desired value in a short time when the voltage is switched, and the stability refers to the performance of the voltage having a small fluctuation.

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