Quality analysis equipment

Abstract

This mass spectrometer comprises a mass filter, a detection unit, a cancellation circuit, and a power source device. The mass filter selects ions having a mass-to-charge ratio corresponding to an applied AC voltage. The detection unit has a plurality of rectification parts, each of which includes a rectification element, and which are connected in parallel, and the detection unit detects the AC voltage applied in the mass filter as a detection voltage. The cancellation circuit cancels AC voltage offset originating from leakage current from the rectification elements. On the basis of the detection voltage, the power source device applies the AC voltage for which the offset was canceled by the cancellation circuit to the mass filter.

Description

[Technical field]

[0001] The present invention relates to a mass spectrometer. [Background technology]

[0002] Mass spectrometers are known as analytical devices that analyze the masses of components contained in a sample. For example, in a quadrupole mass spectrometer described in Patent Document 1, various ions generated from a sample by an ion source are introduced into a quadrupole filter. A radio frequency voltage and a direct current voltage are applied to four rod electrodes of the quadrupole filter by a quadrupole power supply unit. Only ions having a specific mass-to-charge ratio selectively pass through the quadrupole filter and are detected by a detector. The mass-to-charge ratio of the ions passing through the quadrupole filter depends on the radio frequency voltage and the direct current voltage applied to each rod electrode.

[0003] In the quadrupole power supply unit, the radio frequency voltage applied to each rod electrode is converted to a detection current through a capacitor and flows to a rectifier element in the detection unit. The detection current is converted to a DC voltage by flowing through a resistor, and the difference between the converted voltage and a target voltage is fed back. The target voltage is set corresponding to an arbitrary mass-to-charge ratio. Therefore, by sweeping the target voltage, the radio frequency voltage applied to each rod electrode can be swept to scan the mass-to-charge ratio of ions passing through the quadrupole filter.

[0004] When a relatively large detection current flows through the rectifier element, the detection voltage is converted to a voltage smaller than the voltage that should be converted due to leakage current in the rectifier element, and the voltage output from the feedback circuit is greater than the target voltage. In this case, in a range where the mass is large, the difference between the output voltage and the target voltage increases, causing a mass deviation. Therefore, in Patent Document 1, an auxiliary detection unit having detection characteristics substantially identical to those of the detection unit is provided. The amount of nonlinearity error of the auxiliary detection unit with respect to the target voltage is calculated, and the detection voltage by the detection unit is corrected according to the amount of nonlinearity error. [Patent Document 1] JP 2002-33075 A Summary of the Invention [Problem to be solved by the invention]

[0005] If the linearity of the leakage current in the rectifying element is poor, the peaks in the mass spectrum may not be properly separated in the large mass range, and therefore it is not possible to properly prevent mass shifts due to the nonlinear characteristics of the rectifying element.

[0006] An object of the present invention is to provide a mass spectrometer capable of preventing deviations in mass due to the nonlinearity of a rectifying element. [Means for solving the problem]

[0007] One aspect of the present invention comprises a mass filter which selects ions having a mass-to-charge ratio corresponding to an applied AC voltage, a detection unit having a plurality of rectifiers each including a rectifier element and connected in parallel, which detects the AC voltage applied to the mass filter as a detection voltage, a cancellation circuit which cancels an offset in the AC voltage caused by leakage current of the rectifier element, and a power supply device which applies to the mass filter an AC voltage whose offset has been cancelled by the cancellation circuit based on the detection voltage. Each of the plurality of rectifying units includes a first rectifying element, a second rectifying element, a third rectifying element, and a fourth rectifying element, and includes a first node, a second node, a third node, and a fourth node. In each of the plurality of rectifying units, a cathode and an anode of the first rectifying element are connected to the first node and the third node, respectively, a cathode and an anode of the second rectifying element are connected to the second node and the third node, respectively, a cathode and an anode of the third rectifying element are connected to the fourth node and the first node, respectively, and a cathode and an anode of the fourth rectifying element are connected to the fourth node and the first node, respectively. and an anode are connected to the fourth node and the second node, respectively, the first nodes of the plurality of rectifier units are connected to each other and used for input of an AC voltage applied to the mass filter, the second nodes of the plurality of rectifier units are connected to each other and used for input of an AC voltage applied to the mass filter, the third nodes of the plurality of rectifier units are connected to each other, and the fourth nodes of the plurality of rectifier units are connected to each other, one of the third node and the fourth node is maintained at ground potential, and the other of the third node and the fourth node is used for output of a detected AC voltage. The present invention relates to a mass spectrometer. Effect of the Invention

[0008] According to the present invention, it is possible to prevent the mass deviation caused by the nonlinearity of the rectifying element. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing the configuration of a mass spectrometer according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing the configuration of the power supply device of FIG. [Diagram 3] FIG. 3 is a diagram showing the configuration of the detection unit of FIG. [Figure 4]FIG. 4 is a diagram showing the configuration of the cancellation circuit of FIG. [Diagram 5] FIG. 5 is a diagram showing the configuration of a detection unit in the reference embodiment. [Figure 6] FIG. 6 is a diagram showing a mass spectrum in Comparative Example 1. [Figure 7] FIG. 7 is a diagram showing a mass spectrum in Example 1. [Figure 8] FIG. 8 is a diagram showing a mass spectrum in Example 2. [Figure 9] FIG. 9 is a diagram showing a mass spectrum in Example 3. [Figure 10] FIG. 10 shows mass spectra in Comparative Example 2 and Example 4. [Figure 11] FIG. 11 shows mass spectra in Comparative Example 3 and Example 5. [Figure 12] FIG. 12 shows mass spectra in Comparative Example 4 and Example 6. [Figure 13] FIG. 13 shows mass spectra in Reference Examples 1 and 2. [Figure 14] FIG. 14 is a diagram showing the configuration of a power supply device in a modified example. [Figure 15] FIG. 15 is a diagram showing the configuration of the cancellation circuit of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] (1) Mass spectrometer configuration A mass spectrometer according to an embodiment of the present invention will be described in detail below with reference to the drawings. Fig. 1 is a diagram showing the configuration of a mass spectrometer according to an embodiment of the present invention. As shown in Fig. 1, a mass spectrometer 200 includes a power supply unit 100, an ion source 110, an ion transport unit 120, a quadrupole mass filter 130, an ion detector 140, and a processing unit 150.

[0011] The ion source 110 includes, for example, a light source in the ultraviolet region, and generates ions of various components contained in the sample by irradiating the sample to be analyzed with pulsed light. The ion transport section 120 includes, for example, an ion lens, and focuses the ions generated by the ion source 110 and introduces them into the quadrupole mass filter 130 along an ion optical axis 201 shown by a dotted line.

[0012] The quadrupole mass filter 130 includes four rod electrodes 131 to 134. The rod electrodes 131 to 134 are arranged parallel to each other so as to be inscribed in an imaginary cylinder centered on the ion optical axis 201. Therefore, the rod electrodes 131 and 133 face each other with the ion optical axis 201 in between. The rod electrodes 132 and 134 face each other with the ion optical axis 201 in between.

[0013] The power supply unit 100 applies a sum voltage (U+Vcosωt) of a DC voltage U and a radio frequency voltage Vcosωt to the rod electrodes 131, 133. The power supply unit 100 also applies a sum voltage (-U-Vcosωt) of a DC voltage -U and a radio frequency voltage -Vcosωt to the rod electrodes 132, 134. As a result, of the ions introduced into the quadrupole mass filter 130, only ions having a specific mass-to-charge ratio determined by the DC voltage U and the amplitude V of the radio frequency voltage pass through the quadrupole mass filter 130. The configuration of the power supply unit 100 will be described later.

[0014] The ion detector 140 includes, for example, a secondary electron multiplier. The ion detector 140 detects the ions that have passed through the quadrupole mass filter 130, and outputs a detection signal indicating the amount of ions detected to the processing device 150.

[0015] The processing device 150 includes, for example, a CPU (Central Processing Unit) and is realized by an information processing device such as a personal computer. The processing device 150 controls the operations of the power supply device 100, the ion transport unit 120, the quadrupole mass filter 130, and the ion detector 140. The processing device 150 also processes the detection signal output by the ion detector 140 to generate a mass spectrum indicating the relationship between the mass-to-charge ratio of the ions and the amount of detection.

[0016] (2) Power supply configuration Fig. 2 is a diagram showing the configuration of the power supply device 100 in Fig. 1. As shown in Fig. 2, the power supply device 100 includes a detection unit 10, a voltage control unit 20, a high frequency voltage generating unit 30, a DC voltage generating unit 40, and an adder unit 50. The voltage control unit 20, the high frequency voltage generating unit 30, and the DC voltage generating unit 40 are formed of circuit elements such as electric resistors, coils, capacitors, operational amplifiers, or logic circuits. The adder unit 50 is formed of a transformer.

[0017] A control voltage and a correction voltage are applied to the voltage control section 20 by the processing device 150 in Fig. 1, and a detection voltage is fed back from the detection unit 10. The control voltage is a voltage for controlling the radio frequency voltage applied to the quadrupole mass filter 130 so that the radio frequency voltage coincides with an arbitrary target voltage. The correction voltage is a voltage for correcting the mass resolution of the mass-to-charge ratio. The detection voltage fed back by the detection unit 10 will be described later.

[0018] The voltage control unit 20 includes a cancellation circuit 60. The cancellation circuit 60 adds a cancellation voltage to the control voltage to cancel the difference (hereinafter referred to as offset) between the high frequency voltage and the target voltage caused by the leakage current of the rectifier elements D1 to D4. Details of the cancellation circuit 60 will be described later. Furthermore, the voltage control unit 20 generates two systems of voltages by appropriately executing various processes such as comparison, modulation, amplification, and addition on the control voltage, the correction voltage, and the detection voltage, and provides them to the high frequency voltage generating unit 30 and the DC voltage generating unit 40, respectively.

[0019] The high frequency voltage generating unit 30 generates high frequency voltages ±Vcosωt whose phases differ by 180° from each other, based on the voltage provided by the voltage control unit 20. The DC voltage generating unit 40 generates DC voltages ±U whose polarities are opposite to each other, based on the voltage provided by the voltage control unit 20.

[0020] The adder 50 includes a transformer, and generates voltages U+Vcosωt and -U-Vcosωt by adding together the high frequency voltage generated by the high frequency voltage generating unit 30 and the DC voltage generated by the DC voltage generating unit 40. The adder 50 also applies the generated voltage U+Vcosωt from one output terminal of the secondary coil to the rod electrodes 131, 133 of the quadrupole mass filter 130. The adder 50 applies the generated voltage -U-Vcosωt from the other output terminal of the secondary coil to the rod electrodes 132, 134 of the quadrupole mass filter 130.

[0021] (3) Detector unit The detection unit 10 is connected between the output terminals of the secondary coil of the adder 50, and converts the high frequency voltage output from the adder 50 into a detection voltage. Fig. 3 is a diagram showing the configuration of the detection unit 10 in Fig. 2. As shown in Fig. 3, the detection unit 10 includes a plurality of rectifiers 11, detection capacitors 12 and 13, a detection resistor 14, and a smoothing capacitor 15.

[0022] Each rectifier 11 includes four rectifier elements D1 to D4. Each rectifier element D1 to D4 is, for example, a high-speed diode or a Schottky barrier diode. The cathode and anode of the rectifier element D1 are connected to nodes N1 and N3, respectively. The cathode and anode of the rectifier element D2 are connected to nodes N2 and N3, respectively. The cathode and anode of the rectifier element D3 are connected to nodes N4 and N1, respectively. The cathode and anode of the rectifier element D4 are connected to nodes N4 and N2, respectively.

[0023] The multiple rectification units 11 are connected in parallel. Specifically, nodes N1 of the multiple rectification units 11 are connected to each other, and nodes N2 of the multiple rectification units 11 are connected to each other. Furthermore, nodes N3 of the multiple rectification units 11 are connected to each other, and nodes N4 of the multiple rectification units 11 are connected to each other. The node N3 of the multiple rectification units 11 is connected to a ground terminal. The number of rectification units 11 provided in the detection unit 10 is not particularly limited as long as it is two or more.

[0024] The detection capacitors 12 and 13 are, for example, ceramic capacitors. The detection capacitor 12 is connected between one output terminal of the adder unit 50 (FIG. 2) that outputs a voltage U+Vcosωt and a node N1 of the multiple rectifier units 11. The detection capacitor 13 is connected between the other output terminal of the adder unit 50 that outputs a voltage -U-Vcosωt and a node N2 of the multiple rectifier units 11. The detection resistor 14 and the smoothing capacitor 15 are connected in parallel with each other and are connected between a node N4 of the multiple rectifier units 11 and a ground terminal.

[0025] According to the above configuration, the high frequency voltage at the output terminal of the adder 50 is converted into a detection current by the detection capacitor 12 or the detection capacitor 13, and is rectified by flowing through the multiple rectifiers 11. The rectified current is converted into a detection voltage by flowing through the detection resistor 14, and is fed back to the voltage control unit 20 in FIG.

[0026] (4) Cancellation voltage application section Fig. 4 is a diagram showing the configuration of the cancellation circuit 60 of Fig. 2. As shown in Fig. 4, the cancellation circuit 60 includes resistive elements 61-65, a reference power supply 66, and an operational amplifier 67. The resistive elements 61-65 have resistance values ​​R1-R5, respectively. The reference power supply 66 is a DC power supply that generates a reference voltage Vr.

[0027] The resistor element 61 is connected between the positive electrode of the reference power supply 66 and a node N5. The resistor element 62 is connected between the node N5 and a ground terminal. The resistor element 63 is connected between the node N5 and an inverting input terminal of an operational amplifier 67. The resistor element 64 is connected between an input terminal of a control voltage and an inverting input terminal of the operational amplifier 67. The resistor element 65 is connected between the inverting input terminal and an output terminal of the operational amplifier 67. The negative electrode of the reference power supply 66 and the non-inverting input terminal of the operational amplifier 67 are connected to a ground terminal.

[0028] According to this configuration, reference voltage Vr generated in reference power supply 66 is divided according to the ratio of resistance value R1 to resistance value R2, and applied to node N5 as a cancellation voltage. In addition, the cancellation voltage and the control voltage are added by operational amplifier 67. Therefore, operational amplifier 67 is an example of an adder that adds the control voltage and the cancellation voltage and outputs the result.

[0029] The ratio of the cancellation voltage to the control voltage in the voltage output by operational amplifier 67 is equal to the ratio of the reciprocal of resistance value R3 to the reciprocal of resistance value R4. The resistance values ​​R1 to R5 and reference voltage Vr are predetermined so that the cancellation voltage can cancel the offset of the high frequency voltage.

[0030] For example, assume that the deviation of the actual measured value from the theoretical value of any mass-to-charge ratio is 1 (u). Also assume that the mass-to-charge ratio is 2000 when the control voltage is 9.16V. In this case, the resistance values ​​R1 to R5 and the reference voltage Vr are determined so that a cancellation voltage of about 9.16V / 2000=4.58mV is added to the control voltage. As an example, when R1=100kΩ, R2=3.3kΩ, R3=100kΩ, R4=1kΩ, R5=1kΩ, and Vr=-15V, the cancellation voltage is 4.79mV. This cancellation voltage can cancel the offset of the high frequency voltage.

[0031] (5) Comparative Examples and Examples (a) Detection unit Fig. 5 is a diagram showing the configuration of a detection unit in a reference embodiment. As shown in Fig. 5, a detection unit 10a in the reference embodiment has a similar configuration to the detection unit 10 in Fig. 3, except that it includes one rectification unit 11 instead of multiple rectification units 11. In Comparative Example 1, a mass spectrum was measured using the detection unit 10a in the reference embodiment in Fig. 5.

[0032] In Example 1, the mass spectrum was measured using a detection unit 10 including two rectification sections 11 connected in parallel. In Example 2, the mass spectrum was measured using a detection unit 10 including three rectification sections 11 connected in parallel. In Example 3, the mass spectrum was measured using a detection unit 10 including four rectification sections 11 connected in parallel. Note that in Comparative Example 1 and Examples 1 to 3, rectification elements D1 to D4 with relatively poor linearity were used. Here, poor linearity means that when a detection current of a predetermined value or more flows through the rectification elements D1 to D4, the leakage current flowing through the rectification elements D1 to D4 increases rapidly.

[0033] Fig. 6 is a diagram showing a mass spectrum in Comparative Example 1. Fig. 7 is a diagram showing a mass spectrum in Example 1. Fig. 8 is a diagram showing a mass spectrum in Example 2. Fig. 9 is a diagram showing a mass spectrum in Example 3.

[0034] In each of the mass spectra in Figures 6 to 9, peaks in the vicinity of multiple specific mass-to-charge ratios are displayed in an enlarged manner. The magnification ratios of the multiple peaks are different. The deviation between the peak position corresponding to the dotted line in the mass spectrum in each frame and the center position of the horizontal axis of the frame indicates the offset of the radio frequency voltage. Note that the scale intervals of the horizontal axis in each of the mass spectra in Figures 6 to 9 are 0.5 (u). In Figures 10 to 13 described below, the scale intervals of the horizontal axis are 1 (u).

[0035] As shown in Fig. 6, in Comparative Example 1, the width of the peak increases in the range where the mass-to-charge ratio is greater than 1004.60. Moreover, in the range where the mass-to-charge ratio is greater than 1601.15, the peaks are not separated from the other peaks. As shown in Fig. 7, in Example 1, the width of the peak increases near the mass-to-charge ratio of 1893.40, but the peaks are separated from the other peaks. As shown in Figs. 8 and 9, in Examples 2 and 3, the width of the peaks does not increase overall, and the peaks are separated from the other peaks.

[0036] From the comparison results between Comparative Example 1 and Examples 1 to 3, it was confirmed that even when the linearity of the rectifying elements D1 to D4 is relatively poor, it is possible to separate each peak from the other peaks even in a relatively large range of mass-to-charge ratios by connecting multiple rectifying units 11 in parallel. On the other hand, it was confirmed that the offset of the high frequency voltage increases as the number of rectifying units 11 connected in parallel increases.

[0037] (b) Cancellation circuit In Comparative Examples 2 to 4, the voltage control unit 20 was not provided with a cancellation circuit 60, and mass spectra were measured using the detection unit 10 similar to those in Examples 1 to 3. In Examples 4 to 6, the voltage control unit 20 was provided with a cancellation circuit 60, and mass spectra were measured using the detection unit 10 similar to those in Examples 1 to 3. In Comparative Examples 2 to 4 and Examples 4 to 6, rectifier elements D1 to D4 with relatively good linearity were used. Good linearity here means that the magnitude of the leakage current flowing through the rectifier elements D1 to D4 is approximately constant, regardless of the magnitude of the detection current flowing through the rectifier elements D1 to D4.

[0038] Fig. 10 shows mass spectra in Comparative Example 2 and Example 4. Fig. 11 shows mass spectra in Comparative Example 3 and Example 5. Fig. 12 shows mass spectra in Comparative Example 4 and Example 6.

[0039] As shown in the upper part of Fig. 10, in Comparative Example 2, the peak position of the mass-to-charge ratio of 1004.6 indicated by the dotted line is shifted from the center position of the horizontal axis of the frame to the low mass side (left side) by about 1.3 (u). Therefore, the deviation between the measured value and the theoretical value of the mass-to-charge ratio in the vicinity of the mass-to-charge ratio of 1004.6 is about 1.3 (u). In contrast, as shown in the lower part of Fig. 10, in Example 4, the offset of the radio frequency voltage corresponding to the deviation of the mass-to-charge ratio of about 1.3 (u) is cancelled out, so that the peak of the mass-to-charge ratio of 1004.6 indicated by the dotted line is located near the center of the horizontal axis of the frame.

[0040] Similarly, as shown in the upper part of Fig. 11, in Comparative Example 3, the deviation between the measured value and the theoretical value of the mass-to-charge ratio in the vicinity of 1004.6 is about 1.7 (u). In contrast, as shown in the lower part of Fig. 11, in Example 5, the offset of the radio frequency voltage corresponding to the deviation in the mass-to-charge ratio of about 1.7 (u) is cancelled out, so that the peak of the mass-to-charge ratio of 1004.6 shown by the dotted line is located near the center of the horizontal axis of the frame.

[0041] As shown in the upper part of Fig. 12, in Comparative Example 4, the deviation between the measured value and the theoretical value of the mass-to-charge ratio in the vicinity of 1004.6 is approximately 2.1 (u). In contrast, as shown in the lower part of Fig. 12, in Example 6, the offset of the radio frequency voltage corresponding to the deviation in the mass-to-charge ratio of approximately 2.1 (u) is cancelled out, so that the peak at the mass-to-charge ratio of 1004.6 shown by the dotted line is located near the center of the horizontal axis of the frame.

[0042] It was confirmed from the comparison results of Comparative Examples 2 to 4 that the offset of the high frequency voltage increases as the number of rectification units 11 connected in parallel increases. On the other hand, it was confirmed from the comparison results of Comparative Examples 2 to 4 and Examples 4 to 6 that the offset of the high frequency voltage can be canceled out by adding a cancellation voltage to the control voltage.

[0043] (6) Reference example In Reference Example 1, the mass spectrum was measured using the same detection unit 10a as in Comparative Example 1, without providing a cancellation circuit 60 in the voltage control unit 20. In Reference Example 2, the mass spectrum was measured using the same detection unit 10a as in Comparative Example 1, with a cancellation circuit 60 provided in the voltage control unit 20. Here, in Reference Examples 1 and 2, the same rectifying elements D1 to D4 were used as in Comparative Examples 2 to 4 and Examples 4 to 6.

[0044] Fig. 13 shows mass spectra in Reference Examples 1 and 2. As shown in the upper part of Fig. 13, in Reference Example 1, the deviation between the measured value and the theoretical value of the mass-to-charge ratio in the vicinity of a mass-to-charge ratio of 1004.6 is about 1.0 (u). In contrast, as shown in the lower part of Fig. 13, in Reference Example 2, the offset of the radio frequency voltage corresponding to the deviation in the mass-to-charge ratio of about 1.0 (u) is cancelled out, so that the peak at the mass-to-charge ratio of 1004.6 shown by the dotted line is located near the center of the horizontal axis of the frame.

[0045] From the comparison results between Reference Examples 1 and 2, it was confirmed that even if the number of rectifier units 11 is one, the offset of the high frequency voltage can be cancelled out by adding the cancellation voltage to the control voltage.

[0046] (7) Effects In the mass spectrometer 200 according to this embodiment, ions having a mass-to-charge ratio corresponding to the applied radio frequency voltage are selected by the quadrupole mass filter 130. The radio frequency voltage applied to the quadrupole mass filter 130 is detected as a detection voltage by a detection unit 10 having a plurality of rectifiers 11, each of which includes rectifier elements D1 to D4 and is connected in parallel. The offset of the radio frequency voltage caused by leakage currents of the rectifier elements D1 to D4 is cancelled by a cancellation circuit 60. The radio frequency voltage, the offset of which has been cancelled by the cancellation circuit 60 based on the detection voltage, is applied to the quadrupole mass filter 130 by the power supply device 100.

[0047] According to this mass spectrometer 200, even if the linear operating range of the rectifying elements D1 to D4 of each rectifying section 11 is not so wide, the rectifying sections 11 are electrically connected in parallel, thereby improving the overall linearity of the detection unit 10. This makes it possible to appropriately separate ions according to their mass-to-charge ratios, even in a comparatively large range of mass-to-charge ratios.

[0048] Here, the greater the number of rectifiers 11 connected in parallel, the greater the offset of the radio frequency voltage due to leakage current from the rectifier elements D1 to D4. Even in such a case, the offset of the radio frequency voltage due to the leakage current from the rectifier elements D1 to D4 is canceled by the cancellation circuit 60. As a result, it is possible to prevent deviations in the mass-to-charge ratio due to the nonlinearity of the rectifier elements D1 to D4.

[0049] The offset of the radio frequency voltage is cancelled by adding a predetermined cancellation voltage to a control voltage input to control the radio frequency voltage. Specifically, the cancellation circuit 60 includes an operational amplifier 67 that adds the control voltage and the cancellation voltage and outputs the result. The power supply device 100 also applies a radio frequency voltage to the quadrupole mass filter 130 based on the voltage output by the operational amplifier 67 and the detection voltage. In this case, it is possible to cancel the offset of the radio frequency voltage with a simple configuration and to apply the radio frequency voltage with the offset cancelled to the quadrupole mass filter 130.

[0050] Here, the cancellation voltage is determined in advance so as to cancel the difference between the theoretical value and the measured value at any mass-to-charge ratio of the ions. For example, the cancellation voltage is determined in advance so as to shift the mass-to-charge ratio of the ions selected by the quadrupole mass filter 130 by a fixed value of 0.1 (u) or more and 5 (u) or less. In this case, the cancellation voltage for canceling the offset of the radio frequency voltage can be easily determined.

[0051] (8) Variations In the power supply device 100 of Fig. 2, a cancellation voltage is added to the control voltage, but the embodiment is not limited to this. Fig. 14 is a diagram showing the configuration of the power supply device 100 in a modified example. As shown in Fig. 14, in the modified example, a cancellation voltage is added by a cancellation circuit 70 to the sum voltage of the control voltage and the detection voltage.

[0052] Fig. 15 is a diagram showing the configuration of the cancellation circuit 70 of Fig. 14. As shown in Fig. 15, the cancellation circuit 70 includes resistance elements 71 to 75, a reference power supply 76, an operational amplifier 77, and a resistor 78. ,78and an error amplifier 79. The resistance values ​​of the resistive elements 71 to 75 are R1 to R5, respectively. The reference power supply 76 is a DC power supply that generates a reference voltage Vr.

[0053] The resistor element 71 is connected between the positive electrode of the reference power supply 76 and a node N6. The resistor element 72 is connected between the node N6 and a ground terminal. The resistor element 73 is connected between the node N6 and an inverting input terminal of an error amplifier 79. The resistor element 74 is connected between the output terminal of an operational amplifier 77 and an inverting input terminal of the error amplifier 79. The resistor element 75 is connected between the output terminal of an operational amplifier 78 and an inverting input terminal of the error amplifier 79.

[0054] The negative terminal of the reference power supply 76 is connected to the ground terminal. The input terminal of the operational amplifier 77 is connected to the input terminal of the control voltage. The input terminal of the operational amplifier 78 is connected to the input terminal of the detection voltage. The non-inverting input terminal of the error amplifier 79 is connected to the ground terminal. The amplification factor of the operational amplifiers 77 and 78 is 1.

[0055] According to this configuration, reference voltage Vr generated in reference power supply 76 is divided according to the ratio of resistance value R1 to resistance value R2, and the divided voltage is applied to node N6 as a cancellation voltage. In addition, the cancellation voltage, control voltage, and detection voltage are added by error amplifier 79. Therefore, error amplifier 79 is an example of an adder that adds the control voltage, detection voltage, and cancellation voltage and outputs the result.

[0056] The ratio of the cancellation voltage to the control voltage to the detection voltage in the voltage output by the error amplifier 79 is equal to the ratio of the reciprocal of the resistance value R3 to the reciprocal of the resistance value R4 to the reciprocal of the resistance value R5. The resistance values ​​R1 to R5 and the reference voltage Vr are determined in advance so as to cancel the offset of the high frequency voltage.

[0057] As an example, the cancellation voltage is 4.79 mV when R1 = 100 kΩ, R2 = 3.3 kΩ, R3 = 1 MΩ, R4 = 10 kΩ, R5 = 10 kΩ, and Vr = -15 V. This cancellation voltage can cancel the offset of the radio frequency voltage corresponding to a deviation of about 1 (u) of the measured value from the theoretical value of any mass-to-charge ratio.

[0058] Thus, in the modified example, the offset of the radio frequency voltage is cancelled by adding a predetermined cancellation voltage to the sum of the control voltage and the detection voltage input to control the radio frequency voltage. Specifically, the cancellation circuit 70 includes an error amplifier 79 that adds the control voltage, the detection voltage and the cancellation voltage and outputs the result. Furthermore, the power supply device 100 applies the radio frequency voltage to the quadrupole mass filter 130 based on the voltage output by the error amplifier 79. In this case, it is possible to cancel the offset of the radio frequency voltage with a simple configuration and to apply the radio frequency voltage with the offset cancelled to the quadrupole mass filter 130.

[0059] (9) Other embodiments In the above embodiment, the detection unit 10 and the cancellation circuits 60, 70 are provided inside the power supply device 100, but the embodiment is not limited to this. The detection unit 10 may be provided outside the power supply device 100. Similarly, some or all of the cancellation circuits 60, 70 may be provided outside the power supply device 100.

[0060] In the above embodiment, the node N3 of each rectifier 11 is connected to a ground terminal, and the node N4 of each rectifier 11 is connected to the detection resistor 14 and the smoothing capacitor 15, but the embodiment is not limited to this. The node N4 of each rectifier 11 may be connected to a ground terminal, and the node N3 of each rectifier 11 may be connected to the detection resistor 14 and the smoothing capacitor 15.

[0061] Furthermore, in the above embodiment, the rectifier 11 includes four rectifier elements D1 to D4 that configure a full-wave rectifier circuit, but the embodiment is not limited to this. The rectifier 11 may include one rectifier element that configures a half-wave rectifier circuit.

[0062] (10) Description It will be appreciated by those skilled in the art that the above exemplary embodiments are illustrative of the following aspects.

[0063] (Item 1) A mass spectrometer according to one aspect of the present invention comprises: a mass filter for selecting ions having a mass-to-charge ratio corresponding to an applied AC voltage; a detection unit having a plurality of rectification sections each including a rectification element and connected in parallel, which detects an AC voltage applied to the mass filter as a detection voltage; a cancellation circuit for canceling an offset of an AC voltage caused by a leakage current of the rectifier; The power supply may be configured to apply to the mass filter an AC voltage whose offset has been cancelled by the cancellation circuit based on the detection voltage.

[0064] According to this mass spectrometer, even if the linear operating range of the rectifying element of each rectifying section is not so wide, the rectifying sections are electrically connected in parallel, thereby improving the overall linearity of the detection unit, and thus making it possible to appropriately separate ions according to their mass-to-charge ratios even in a relatively large range of mass-to-charge ratios.

[0065] Here, the greater the number of rectifiers connected in parallel, the greater the offset of the AC voltage due to leakage current of the rectifier elements. Even in such a case, the offset of the AC voltage due to leakage current of the rectifier elements is cancelled by the cancellation circuit. As a result, it is possible to prevent deviation of the mass-to-charge ratio due to the nonlinearity of the rectifier elements.

[0066] (Item 2) In the mass spectrometer according to item 1, The cancellation circuit may cancel the offset of the AC voltage by adding a predetermined cancellation voltage to a control voltage that is input to control the AC voltage.

[0067] In this case, the offset of the AC voltage can be cancelled with a simple configuration.

[0068] (Item 3) In the mass spectrometer according to item 2, the cancellation circuit includes an adder that adds the control voltage and the cancellation voltage and outputs the result; The power supply device may apply an AC voltage to the mass filter based on the voltage output by the adder and the detection voltage.

[0069] In this case, it is possible to cancel the offset of the AC voltage with a simple configuration, and to apply the AC voltage with the offset canceled to the mass filter.

[0070] (Item 4) In the mass spectrometer according to item 1, The cancellation circuit may cancel the offset of the AC voltage by adding a predetermined cancellation voltage to a sum voltage of the detection voltage and a control voltage input for controlling the AC voltage.

[0071] In this case, the offset of the AC voltage can be cancelled with a simple configuration.

[0072] (Item 5) In the mass spectrometer according to item 4, the cancellation circuit includes an adder that adds the control voltage, the detection voltage, and the cancellation voltage and outputs the result; The power supply device may apply an AC voltage to the mass filter based on the voltage output by the adder.

[0073] In this case, it is possible to cancel the offset of the AC voltage with a simple configuration, and to apply the AC voltage with the offset canceled to the mass filter.

[0074] (Item 6) In the mass spectrometer according to any one of items 2 to 5, The counter voltage may be predetermined so as to counteract the difference between a theoretical value and an actual measured value for any mass-to-charge ratio of ions.

[0075] In this case, a cancellation voltage for canceling the offset of the AC voltage can be easily determined.

[0076] (Item 7) In the mass spectrometer according to any one of items 2 to 6, The cancellation voltage may be predetermined to shift the mass to charge ratio of ions selected by the mass filter by a constant value between 0.1 and 5.

[0077] In this case, a cancellation voltage for canceling the offset of the AC voltage can be easily determined.

Claims

1. a mass filter for selecting ions having a mass-to-charge ratio corresponding to an applied AC voltage; a detection unit having a plurality of rectification sections each including a rectification element and connected in parallel, which detects an AC voltage applied to the mass filter as a detection voltage; a cancellation circuit for canceling an offset of an AC voltage caused by a leakage current of the rectifier; a power supply device that applies to the mass filter an AC voltage whose offset has been cancelled by the cancellation circuit based on the detection voltage; each of the plurality of rectification units includes a first rectification element, a second rectification element, a third rectification element, and a fourth rectification element, and includes a first node, a second node, a third node, and a fourth node; In each of the plurality of rectifying units, a cathode and an anode of the first rectifying element are connected to the first node and the third node, respectively; a cathode and an anode of the second rectifying element are connected to the second node and the third node, respectively; a cathode and an anode of the third rectifying element are connected to the fourth node and the first node, respectively; a cathode and an anode of the fourth rectifying element are connected to the fourth node and the second node, respectively; the first nodes of the plurality of rectifiers are connected to each other and are used for inputting an AC voltage to be applied to the mass filter; the second nodes of the plurality of rectifiers are connected to each other and are used as an input of an AC voltage to be applied to the mass filter; the third nodes of the plurality of rectification units are connected to each other, the fourth nodes of the plurality of rectification units are connected to each other, one of the third node and the fourth node is maintained at a ground potential; A mass spectrometer, wherein the other of the third node and the fourth node is used to output a detected AC voltage.

2. 2. The mass spectrometer according to claim 1, wherein the cancellation circuit cancels the offset of the AC voltage by adding a predetermined cancellation voltage to a control voltage that is input to control the AC voltage.

3. the cancellation circuit includes an adder that adds the control voltage and the cancellation voltage and outputs the result; 3. The mass spectrometer according to claim 2, wherein said power supply unit applies an AC voltage to said mass filter based on the voltage output by said adder and said detection voltage.

4. 2. The mass spectrometer according to claim 1, wherein the cancellation circuit cancels the offset of the AC voltage by adding a predetermined cancellation voltage to a sum voltage of the detection voltage and a control voltage input for controlling the AC voltage.

5. the cancellation circuit includes an adder that adds the control voltage, the detection voltage, and the cancellation voltage and outputs the result; The mass spectrometer according to claim 4 , wherein the power supply unit applies an AC voltage to the mass filter based on the voltage output by the adder.

6. 6. The mass spectrometer according to claim 2, wherein the counter voltage is determined in advance so as to counter a difference between a theoretical value and an actually measured value at an arbitrary mass-to-charge ratio of ions.

7. 6. A mass spectrometer according to claim 2, wherein the cancellation voltage is predetermined to shift the mass-to-charge ratio of ions selected by the mass filter by a constant value between 0.1 and 5.

Images