阅读说明：本技术 飞行时间质谱分析装置和记录介质 (Time-of-flight mass spectrometer and recording medium ) 是由 出水秀明 于 2019-08-08 设计创作，主要内容包括：提供一种飞行时间质谱分析装置和记录介质。在高分辨率化、高精度化的飞行时间质谱分析装置中，有可能由于空间电荷效应导致测量精度下降。飞行时间质谱分析装置具备飞行管(14)、与飞行管(14)连接的离子导入部(1)、检测在飞行管(14)内飞行的离子的离子检测器(20)以及控制离子导入部(1)和飞行管(14)的控制部(30)，其中，控制部(30)在重复进行的多次测量中依次变更由离子导入部(1)导入到飞行管(14)的离子的累积状态。(Provided are a time-of-flight mass spectrometry apparatus and a recording medium. In a time-of-flight mass spectrometer with high resolution and high accuracy, there is a possibility that the measurement accuracy is lowered due to a space charge effect. A time-of-flight mass spectrometer is provided with a flight tube (14), an ion introduction unit (1) connected to the flight tube (14), an ion detector (20) that detects ions flying within the flight tube (14), and a control unit (30) that controls the ion introduction unit (1) and the flight tube (14), wherein the control unit (30) sequentially changes the accumulation state of ions introduced into the flight tube (14) by the ion introduction unit (1) during a plurality of repeated measurements.)

1. A time-of-flight mass spectrometry device is provided with:

a flight tube;

an ion introduction unit connected to the flight tube;

an ion detector for detecting ions flying within the flight tube; and

a control unit for controlling the ion introduction unit and the flight tube,

wherein the control unit sequentially changes the accumulation state of the ions introduced into the flight tube by the ion introduction unit in a plurality of repeated measurements.

2. The time-of-flight mass spectrometry apparatus of claim 1,

the ion introduction part has an ion trap.

3. The time-of-flight mass spectrometry apparatus of claim 2,

the change of the accumulation state is performed by changing an accumulation time of accumulation in the ion trap.

4. The time-of-flight mass spectrometry apparatus of any one of claims 1 to 3,

the control portion decides an optimum accumulation state from a plurality of the accumulation states based on the results of the plurality of measurements.

5. The time-of-flight mass spectrometry apparatus of claim 4,

the control unit sets the optimal accumulation state more than other accumulation states when changing the accumulation state after determining the optimal accumulation state.

6. The time-of-flight mass spectrometry apparatus of claim 4 or 5,

the control unit determines the optimal accumulation state based on a peak intensity of at least one ion detection result of the results of the plurality of measurements.

7. The time-of-flight mass spectrometry apparatus of claim 4 or 5,

the control unit determines the optimal accumulation state based on a time width of at least one ion detection result of the results of the plurality of measurements.

8. The time-of-flight mass spectrometry apparatus of claim 4 or 5,

the control portion decides the optimal accumulation state based on an integrated value of the ion detection amount in each result of the plurality of measurements.

9. The time-of-flight mass spectrometry apparatus of claim 4 or 5,

a second ion detector for detecting the amount of ions introduced into the flight tube, in addition to the ion detector,

the control portion determines the optimal accumulation state based on an integrated value of an ion detection amount of the second ion detector in each of the plurality of measurements.

10. The time-of-flight mass spectrometry apparatus of any one of claims 4 to 9,

the control unit displays the result measured in the optimal accumulation state on a display unit.

11. The time-of-flight mass spectrometry apparatus of claim 6 or 7,

the control unit excludes at least a part of the measurement results except for the ion detection results used for determining the optimal accumulation state, and displays the excluded measurement results on a display unit or collects the measurement results in a measurement result database.

12. A recording medium storing a program for controlling a time-of-flight mass spectrometry apparatus,

the program causes a data processing apparatus including a computer to perform control as follows: the accumulation state of ions introduced from the ion introduction part into the flight tube is sequentially changed in a plurality of repeated measurements.

13. The recording medium of claim 12,

causing the data processing apparatus to decide an optimum accumulation state from a plurality of the accumulation states based on results of the plurality of measurements.

Technical Field

The present invention relates to a time-of-flight mass spectrometry apparatus and a program.

Background

In a time-of-flight mass spectrometer (hereinafter, sometimes referred to as a TOFMS), ions to be analyzed are introduced into a flight space formed in a flight tube and are flown in the flight space by giving a fixed kinetic energy to the ions. Then, the time required for each ion to fly a fixed distance is measured, and the mass-to-charge ratio (m/z) of each ion is calculated based on the time of flight.

In addition, the following method is also proposed in a time-of-flight mass spectrometer (see patent document 1): the ions to be analyzed are accumulated in the ion trap before being introduced into the flight tube, so that the number of the ions to be analyzed is increased, thereby improving the measurement accuracy.

Disclosure of Invention

Problems to be solved by the invention

Since the analysis target of the time-of-flight mass spectrometer is an ion having an electric charge, when the number of ions introduced into the device increases, the measurement accuracy may be degraded due to a so-called space charge effect. The effect of space charge effects is not a problematic level at the currently required measurement accuracy. However, in order to realize a mass spectrometer with higher accuracy and higher resolution in the future, it is necessary to increase the number of ions and the flight distance in the flight tube, and as a result, the following problems occur: the influence of the space charge effect increases, and the space charge effect cannot be ignored.

Means for solving the problems

A time-of-flight mass spectrometer according to a preferred embodiment of the present invention includes: a flight tube; an ion introduction unit connected to the flight tube; an ion detector for detecting ions flying within the flight tube; and a control unit configured to control the ion introduction unit and the flight tube, wherein the control unit sequentially changes an accumulation state of the ions introduced into the flight tube by the ion introduction unit in a plurality of repeated measurements.

In a more preferred aspect, the ion introducing unit includes an ion trap.

In a more preferred aspect, the change of the accumulation state is performed by changing an accumulation time of accumulation in the ion trap.

In a more preferred aspect, the control unit determines an optimal accumulation state from among the plurality of accumulation states based on the results of the plurality of measurements.

In a more preferable aspect, the control unit sets the optimal accumulation state more than other accumulation states when changing the accumulation state after determining the optimal accumulation state.

In a more preferred aspect, the control unit determines the optimal accumulation state based on a peak intensity of at least one ion detection result of the results of the plurality of measurements.

In a more preferred aspect, the control unit determines the optimal accumulation state based on a time width of at least one ion detection result of the results of the plurality of measurements.

In a more preferable mode, the control portion determines the optimal accumulation state based on an integrated value of ion detection amounts in respective results of the plurality of measurements.

In a more preferred aspect, the ion detector is provided with a second ion detector for detecting an amount of ions introduced into the flight tube, and the control unit determines the optimal accumulation state based on an integrated value of an ion detection amount of the second ion detector in each of the plurality of measurements.

In a more preferable mode, the control unit displays a result measured in the optimal accumulation state on a display unit.

In a more preferred aspect, the control unit excludes at least a part of the measurement results other than the ion detection results used for determining the optimal accumulation state, and displays the excluded measurement results on a display unit or collects the measurement results in a measurement result database.

A program according to a preferred embodiment of the present invention is a program for controlling a time-of-flight mass spectrometer, the program causing a data processing apparatus including a computer to perform the following control: the accumulation state of ions introduced from the ion introduction part into the flight tube is sequentially changed in a plurality of repeated measurements.

A more preferable mode of the program causes the data processing apparatus to decide an optimum accumulation state from a plurality of the accumulation states based on the results of the plurality of measurements.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, a high-precision and high-resolution time-of-flight mass spectrometer can be realized with reduced adverse effects due to space charge effects.

Drawings

Fig. 1 is a diagram showing the configuration of a time-of-flight mass spectrometer according to a first embodiment.

Fig. 2 is a diagram showing an example of the transmission efficiency of the ion transmission optical system measured for each of a plurality of measurements.

Fig. 3 shows an example of the measurement result, fig. 3 (a) shows the measurement result in the case where the transmission efficiency is low, fig. 3 (b) shows the measurement result in the case where the transmission efficiency is medium, and fig. 3 (c) shows the measurement result in the case where the transmission efficiency is high.

Fig. 4 is a diagram showing the structure of an ion introduction unit of a time-of-flight mass spectrometer according to a second embodiment.

Fig. 5 is a diagram showing a modification of the measurement result displayed on the display unit.

Fig. 6 is a graph showing another example of the transmission efficiency of the ion transmission optical system measured for each of the plurality of measurements.

Fig. 7 is a diagram showing an example of a flowchart executed by the software embodiment.

Description of the reference numerals

100: a time-of-flight mass spectrometry device; 1, 1 a: an ion introduction part; 2: an ionization chamber; 3: ESI nebulizers; 4: heating the capillary tube; 5. 7: an ion guide; 6: a separator; 8: a quadrupole mass filter; 9: a collision cell; 10: an electrode; 12: an ion transmission optical system; 13: a vacuum chamber (TOF section); 14: a flight tube; 15: a support member; 16: an orthogonal acceleration electrode; 17: a repulsion electrode; 18: leading out an electrode; 20: an ion detector; 21: a second ion detector; 22: a quadrupole ion trap; FA: a flight space; FP: a flight path; 19: a reflector; 30: a control unit; 31: a CPU; 32: a memory; 33: a hard disk drive; 34: a display unit; 35: and (4) a server.

Detailed Description

(first embodiment of time-of-flight mass spectrometer)

Fig. 1 is a conceptual diagram illustrating the configuration of a time-of-flight mass spectrometer 100 according to the first embodiment. The time-of-flight mass spectrometer 100 includes an ion introduction unit 1, a vacuum chamber 13 connected to the ion introduction unit 1, and a flight tube 14 provided inside the vacuum chamber 13.

An ESI nebulizer 3 as an ion source is provided in an ionization chamber 2 in the ion introduction unit 1, and the ESI nebulizer 3 is used to perform electrospray ionization (ESI). When a sample solution containing a component to be analyzed is supplied to the ESI nebulizer 3, ions derived from the sample in the sample solution are generated by electrostatic nebulization of the sample solution from the ESI nebulizer 3. Further, the ionization method is not limited thereto.

The generated ions pass through the heated capillary 4, are converged by the ion guide 5, and then pass through the separator 6 to reach the ion guide 7 of an octupole rod type. The ions converged by the ion guide 7 are introduced into the quadrupole mass filter 8, and only ions having a specific mass-to-charge ratio corresponding to the voltage applied to the quadrupole mass filter 8 pass through the quadrupole mass filter 8. This ion is called a precursor ion. Precursor ions are introduced into a collision cell 9 provided with a multipole rod-type ion guide 10, and the precursor ions are fragmented by collision with CID gas supplied from the outside, thereby generating various product ions.

The product ions generated in the collision cell 9 are guided by the ion transmission optical system 12 and introduced into the vacuum chamber 13 connected to the ion introduction unit 1.

Although not shown, a vacuum pump is connected to the ion introduction unit 1 and the vacuum chamber 13, and the inside of the ion introduction unit 1 and the vacuum chamber 13 is maintained in a reduced pressure state.

Inside the vacuum chamber 13, a support member 15 having insulation properties and high vibration absorption performance is provided. At least a part of the outer surface of the substantially square-cylindrical or substantially cylindrical flight tube 14 is supported by the support member 15, and is supported by the vacuum chamber 13 via the support member 15.

The orthogonal acceleration electrode 16 and the ion detector 20 are fixed to the flight tube 14 via support members, not shown. Orthogonal accelerating electrodes 16 are part of flight tube 14. A reflector 19 including a plurality of annular or rectangular annular reflecting electrodes is disposed on the lower side inside the flight tube 14. Thus, a reflection-type flight space FA for folding back ions by a reflection electric field formed by the reflector 19 is provided inside the flight tube 14.

The flight tube 14 is made of metal such as stainless steel, and a predetermined direct current voltage is applied to the flight tube 14. Further, different dc voltages are applied to the plurality of reflecting electrodes constituting the reflector 19 with reference to the voltage applied to the flight tube 14. Thereby, a reflected electric field is formed in the reflector, and the rest of the flying space FA has no electric field and no magnetic field, and is in a high vacuum.

The ions traveling in the + X direction and introduced into the orthogonal acceleration electrode 16 are accelerated in the-Z direction by forming a predetermined electric field between the repeller electrode 17 and the extractor electrode 18 at a predetermined timing, and start flying. The ions emitted from the orthogonal acceleration electrode 16 first fly freely in the flight space FA as indicated by a flight path FP of a broken line, then turn back in the + Z direction due to the reflected electric field formed by the reflectron 19, and fly freely again in the flight space FA to reach the ion detector 20.

The velocity of an ion in flight space depends on the mass-to-charge ratio of the ion. Therefore, the plurality of ions having different mass-to-charge ratios introduced into the flight space FA substantially simultaneously are separated according to the mass-to-charge ratio during flight, and arrive at the ion detector 20 with a time difference. The detection signal of the ion detector 20 is input to the control unit 30, and the flight time of each ion is converted into a mass-to-charge ratio, thereby creating a mass spectrum and performing mass spectrometry.

The control unit 30 includes a CPU 31, a memory 32, and a hard disk drive 33 therein, and the control unit 30 can control each unit of the time-of-flight mass spectrometer 100 by storing a program in the memory 32 or the hard disk drive 33 and causing the CPU 31 to execute the program.

The control unit 30 also gives a command to the orthogonal acceleration electrode 16 to form a predetermined electric field between the repeller electrode 17 and the extraction electrode 18 at a predetermined timing.

The flight path FP of the ions of the flight space FA is preferably longer for higher accuracy or higher resolution mass spectrometry. This is because, by lengthening the flight path FP, the velocity difference depending on the mass-to-charge ratio of the ions becomes a larger time difference and is measured.

However, when the flight path FP is lengthened, the flight time of the ions increases, and therefore the action time of the interaction of the electric field/magnetic field generated from the ions, such as the repulsive force between the ions due to the electric charge, also increases, that is, the influence of the space charge effect becomes large.

Therefore, in the first embodiment, measurement including flight of ions in the flight tube 14 and detection of ions by the ion detector 20 is performed a plurality of times, and the amount of ions introduced from the ion introduction unit 1 into the flight tube 14 is changed for each measurement. Before each measurement, the control unit 30 sends a command to the ion transport optical system 12 to change the voltage applied to each electrode constituting the ion transport optical system 12. Accordingly, since the imaging conditions of the ion transport optical system 12 are changed, the transport efficiency of the ion transport optical system 12, that is, the ratio of ions guided by the orthogonal acceleration electrode 16, which is a part of the flight tube 14, after being emitted from the collision cell 9 is changed. Therefore, the amount of ions introduced from the ion introduction unit 1 into the flight tube 14 (the accumulation state of ions) can be changed for each measurement.

Fig. 2 is a graph showing an example of the transmission efficiency of the ion transmission optical system 12 set for each of a plurality of measurements. The abscissa of the graph represents the number of measurements Fn, and the ordinate of the graph represents the transmission efficiency S of the ion transmission optical system 12.

In the example shown in fig. 2, it is assumed that the measurement is performed 9 times F1 to F9. The transmission efficiency S of the ion transport optical system 12 is set to S1 in 3 measurements of F1, F4, and F7, S2 in 3 measurements of F2, F5, and F8, and S3 in 3 measurements of F3, F6, and F9.

Fig. 3 is a graph showing an example of the measurement results, in which fig. 3 (a) shows the measurement results in the case where the transmission efficiency S of the ion transmission optical system 12 is low (S1 shown in fig. 2), fig. 3 (b) shows the measurement results in the case where the transmission efficiency S of the ion transmission optical system 12 is medium (S2 shown in fig. 2), and fig. 3 (c) shows the measurement results in the case where the transmission efficiency S of the ion transmission optical system 12 is high (S3 shown in fig. 2).

The horizontal axis of each graph in fig. 3 (a) to 3 (c) represents the flight time Tf of the ion, and the vertical axis represents the amount of the ion detected by the ion detector 20. In the example of fig. 3, the ions to be measured include three kinds of ions Ia, Ib, and Ic, and the flight time Tf of each ion differs depending on the mass-to-charge ratio of each ion.

In the example of fig. 3, the ion Ia is present in a relatively small amount in the ion to be measured, the ion Ic is present in a relatively large amount in the ion to be measured, and the ion Ib is present in an intermediate amount therebetween.

In the case of the measurement result shown in fig. 3 (a), since the transmission efficiency S of the ion transmission optical system 12 is low, the accumulation state of ions introduced from the ion introduction part 1 into the flight tube 14 at the time of measurement is also low, and thus the total amount of ions detected in one measurement is also small. Under such conditions, the detection result Ia1 of the presence of the ion Ia and the detection result Ib1 of the ion Ib are small in ratio, and it is difficult to determine the correct flight times of the ion Ia and the ion Ib due to the influence of the measurement noise.

On the other hand, the detection result Ic1 in which there is an ion Ic having a large ratio is sufficiently higher than the noise level under such conditions, and the detection result Ic1 is not saturated either, so that the time of flight can be accurately determined, that is, the mass-to-charge ratio can be measured with high accuracy.

At this time, for example, the control unit 30 determines the flight time by calculating the center of gravity for a portion of the detection result Ic1 at a predetermined level or higher.

In the case of the measurement result shown in (b) of fig. 3, since the transmission efficiency S of the ion transmission optical system 12 is moderate, there is a detection result Ia2 smaller than that of the small ion Ia, which is insufficient to determine the correct flight time.

However, the detection result Ib2 of the ion Ib having a moderate presence ratio is not saturated and is sufficiently higher than the noise level. Therefore, the time of flight of the ion Ib can be accurately determined, that is, the mass-to-charge ratio can be measured with high accuracy.

However, in the case of the measurement result shown in fig. 3 (b), the detection result Ic2 in which ions Ic having a larger ratio are present is saturated. Further, since a large number of ions Ic to the extent of saturating the ion detector 20 fly on the flight path FP substantially simultaneously, the detection result Ic2 is strongly influenced by the space charge effect. As a result, even if the mass-to-charge ratio of the ion Ic is measured using the detection result Ic2, it is difficult to perform the measurement with high accuracy.

In the case of the measurement result shown in fig. 3 (c), since the transmission efficiency S of the ion transmission optical system 12 is high, the accumulation state of the ions introduced from the ion introduction part 1 into the flight tube 14 at the time of measurement is also high. Therefore, a sufficient detection result Ia3 can be obtained even for ions Ia having a small presence ratio, the flight time of the ions Ia can be accurately determined, and the mass-to-charge ratio can be measured with high accuracy.

However, the detection result Ib3 of the ion Ib having the moderate presence ratio and the detection result Ic3 of the ion Ic having the high presence ratio were saturated. As in the case described above, the adverse effect of the space charge effect caused by the ions to such an extent that the ion detector 20 is saturated makes it difficult to measure the mass-to-charge ratio with high accuracy from the measurement results shown in fig. 3 (c) for the ions Ib and the ions Ic.

When the above plurality of measurements are summarized, the flight time of the ions Ia having a small presence ratio is calculated based on the detection result Ia3 in the measurement in which the transport efficiency S of the ion transport optical system 12 is set high (S3), the flight time of the ions Ib having a medium presence ratio is calculated based on the detection result Ib2 in the measurement in which the transport efficiency S of the ion transport optical system 12 is set medium (S2), and the flight time of the ions Ic having a large presence ratio is calculated based on the detection result Ic1 in the measurement in which the transport efficiency S of the ion transport optical system 12 is set low (S1), whereby high-precision and high-resolution flight time measurement in which adverse effects due to the space charge effect are reduced can be performed.

The method of changing the accumulation state of the ions introduced from the ion introduction unit 1 into the flight tube 14 is not limited to the change in the transmission efficiency of the ion transmission optical system 12 described above. The accumulated state of ions introduced from ion introduction unit 1 into flight tube 14 can also be changed by changing the voltage applied to ion guide 5 and ion guide 7, which are other elements constituting ion introduction unit 1, and the voltage applied to multipole rod-type ion guide 10 in collision cell 9.

(Effect of the first embodiment)

(1) The time-of-flight mass spectrometer of the first embodiment described above has the following structure: the ion implanter is provided with a flight tube 14, an ion introduction part 1 connected to the flight tube 14, an ion detector 20 for detecting ions flying in the flight tube 14, and a control part for controlling the ion introduction part 1 and the flight tube 14, wherein the control part 30 sequentially changes the accumulation state of the ions introduced into the flight tube 14 by the ion introduction part 1 in a plurality of repeated measurements.

Therefore, a high-precision and high-resolution time-of-flight mass spectrometer can be realized with reduced adverse effects due to space charge effects.

(second embodiment of time-of-flight Mass Spectrometry device)

The time-of-flight mass spectrometer of the second embodiment is substantially the same as the time-of-flight mass spectrometer of the first embodiment, but only the ion introduction part 1a is different from the ion introduction part 1 of the first embodiment.

Fig. 4 is a diagram showing an outline of an ion introduction unit 1a of a time-of-flight mass spectrometer according to a second embodiment. In the ion introduction part 1a of the time-of-flight mass spectrometer according to the second embodiment, an ion trap 22 is provided between the collision cell 9 and the ion transmission optical system 12. The ion trap 22 is, for example, a quadrupole ion trap.

In the time-of-flight mass spectrometer according to the second embodiment, various product ions generated in the collision cell 9 are accumulated in the ion trap 22, released from the ion trap 22 at a predetermined timing, guided by the ion transport optical system 12, and introduced into the orthogonal acceleration electrode 16 that is a part of the flight tube 14. The ion trap 22 accumulates and releases ions based on instructions from the control unit 30.

In the second embodiment, since various product ions can be accumulated and released in the ion trap 22, the number of ions flying in the flight tube 14 in one measurement can be set to be larger than that in the first embodiment, and a signal (ion detection amount) can be increased with respect to noise, thereby enabling measurement with good S/N.

(modification 1 of the second embodiment)

Instead of providing the ion trap 22 as described above, the collision cell 9 itself may have an ion trap function. That is, the following configuration may be adopted: for example, as shown in fig. 4, an entrance lens electrode 11a and an exit lens electrode 11b are provided in the collision cell 9, and product ions generated in the collision cell 9 are temporarily accumulated in the collision cell 9.

In this case, a voltage for discharging ions is applied to the entrance lens electrode 11a and the exit lens electrode 11b at a predetermined timing based on an instruction from the control section 30, and the accumulated ions are released.

In fig. 4, a collision cell 9 is shown with an ion trap 22 with the addition of an ion accumulation effect. However, the ion accumulation effect may be added to the collision cell 9 of the apparatus of fig. 1 without the ion trap 22.

(effects of second embodiment and modification 1)

(2) The time-of-flight mass spectrometer according to the first embodiment described above is configured such that the ion introduction unit 1 includes the ion trap 22, in addition to the time-of-flight mass spectrometer according to the first embodiment described above.

This makes it possible to increase the number of ions flying in the flight tube 14 in one measurement, and to perform a good S/N measurement.

In the second embodiment and modification 1, as in the first embodiment described above, even if the number of ions flying in the flight tube 14 increases, the adverse effect of the space charge effect is not received.

(modification 2 of the second embodiment)

In modification 2, in the second embodiment or modification 1 described above, the ion accumulation time of the ion trap 22 or the collision cell 9 is changed, thereby changing the accumulation state of ions introduced into the orthogonal acceleration electrode 16 of the flight tube 14. In addition, the transmission efficiency of the ion introduction part 1 can be changed by changing the voltages applied to the ion transmission optical system 12, the ion guide 5, and the ion guide 7 in the ion introduction part 1 in accordance with the change.

(Effect of modification 2)

(3) The time-of-flight mass spectrometer of modification 2 described above is configured to change the accumulation state by the ion trap 22 or change the accumulation state by changing the accumulation time accumulated in the collision cell 9, in addition to the time-of-flight mass spectrometer of the second embodiment described above, and therefore, ions generated in the ion introduction unit 1 can be efficiently used for measurement.

(modification 3)

In the time-of-flight mass spectrometer according to modification 3, in the time-of-flight mass spectrometer according to each of the above-described embodiments and modifications, the control unit 30 determines the optimum accumulation state based on the results of a plurality of measurements performed so as to differentiate the accumulation states of ions.

For example, the control unit 30 determines an accumulation state in which the peak value of the detected amount of ions designated by the operator is not saturated and is sufficiently higher than the noise level with respect to the measurement result shown in fig. 3.

In the case where the operator has designated the ion I2, for example, the detection result Ib2 of the ion Ib shown in (b) of fig. 3 satisfies this condition, and therefore the transmission efficiency S2 of the ion transport optical system 12 used when measuring the result of (b) of fig. 3 is decided as the optimum accumulation state.

Even when the operator designates two kinds of ions, the respective optimum accumulation states can be determined for the two kinds of ions.

The detected amount of ions may be sufficiently higher than the noise level, and for example, it is sufficient to determine whether or not the detected amount of ions is 4 times or more the standard deviation of the noise level.

The optimum accumulation time can also be decided by the following algorithm.

(1) The control unit 30 may set, as the optimal accumulation state, the transmission efficiency S (accumulation state) in which the peak of the ion detection amount of the detected ions is not saturated and is sufficiently higher than the noise level, for the ion having the smallest detection amount among the plurality of types of detected ions.

(2) The control unit 30 may select a measurement result in which the time width of the ion detection amount of the ions designated by the operator is within a predetermined time width range from the results of the plurality of measurements, and set the transmission efficiency S (accumulation state) when the measurement result is obtained as the optimal accumulation state.

The time width of the measured ion detection amount is, for example, a full width at half maximum of the ion detection amount in time, and is approximately equal to the time resolution of the time-of-flight mass spectrometer. Therefore, if the time width of the measured ion detection amount is, for example, 2 times or more the time resolution of the apparatus, it is estimated that the measurement result is adversely affected by the space charge effect. On the other hand, if the time width of the measured ion detection amount is, for example, half or less of the time resolution of the apparatus, it is estimated that the measurement result is affected by noise.

Therefore, the optimum accumulation state can be determined by selecting a measurement result in which the time width of the ion detection amount is within a predetermined time width range.

(3) The control section 30 can also determine the optimum accumulation state based on the integrated value of the ion detection amount in each result of the plurality of measurements. In this case, it is difficult to determine the optimal accumulation state for each ion based on the detected amount thereof, but the calculation amount required for determining the optimal accumulation state can be reduced, and the determination can be performed in a short time.

(4) The time-of-flight mass spectrometer may further include a second ion detector 21 in addition to the ion detector 20 for detecting the ions flying in the flight tube 14, the second ion detector 21 being configured to detect the ions introduced into the orthogonal acceleration electrode 16 as a part of the flight tube 14 and passing through the orthogonal acceleration electrode 16. The amount of ions detected by the second ion detector 21 is proportional to the amount of ions detected by the ion detector 20. Therefore, the amount of ions flying in the flight tube 14 can be estimated based on the amount of ion detection by the second ion detector 21, and therefore the control unit 30 can also determine the optimal accumulation state based on the amount of ion detection by the second ion detector 21 in each result of the plurality of measurements.

The time-of-flight mass spectrometer according to modification 3 may be configured as follows: the ion sensor further includes a display unit 34, and the display unit 34 displays the result (such as a graph of the ion detection amount with respect to the flight time) measured in the optimal accumulation state. The operator can thereby observe the results measured under the optimum measurement conditions on the display unit 34.

In addition, in the case where the optimal accumulation state is determined based on the ions designated by the operator or the ions having the smallest number of ions, at least a part of the detection results other than the part indicating the detection results of the ions used in the determination of the optimal accumulation state can be excluded, and the measurement results after the exclusion can be displayed on the display unit 34.

Fig. 5 is a diagram showing an example of such display, and fig. 5 basically shows the measurement result shown in fig. 3 (b). As described above, in the measurement results shown in fig. 3 (a) to 3 (c), for example, in the case where the operator designates the ion I2, the result of fig. 3 (b) is a measurement result in the optimum accumulation state for the ion I2. In the measurement result in fig. 3 (b), the detection result Ic2 of the ion Ic is saturated. Therefore, in the display shown in fig. 5, a portion indicating the detection result Ic2 of the ion Ic is excluded from the measurement results in fig. 3 (b), and the portion indicating the detection result Ic2 of the ion Ic is displayed as at least a part other than the portion indicating the detection result Ib2 of the ion Ib.

By such display, unnecessary information can be deleted and only necessary information can be displayed to the operator.

Instead of displaying at least a part of the measurement results excluding the part from which the detection results of the ions used for the determination of the optimal accumulation state are excluded on the display unit 34, the measurement results excluding at least a part may be accumulated, that is, stored in the measurement result database, or the measurement results excluding at least a part may be accumulated, that is, stored in the measurement result database together with the display of the measurement results excluding at least a part on the display unit 34.

The measurement result database may be stored in a storage device (memory 32, hard disk drive 33, or the like) in the control unit 30, or may be in a server 35 connected via the network NW.

(modification 4)

In the time-of-flight mass spectrometer according to modification 4, the time-of-flight mass spectrometer according to modification 3 is configured such that, after the optimum accumulation state is determined, the determined optimum accumulation state is set to be larger than the other accumulation states in the subsequent measurements.

Fig. 6 is a diagram showing an example of setting of the accumulation state (the transmission efficiency S of the ion transmission optical system 12) in modification 4, and is the same as the diagram in fig. 2 described above.

In fig. 6, in the first 3 measurements (F1 to F3), the transmission efficiency S is set to S1, S2, and S3 in this order, as in the first embodiment described above. Then, the control unit 30 determines that the transmission efficiency S3 is in the optimum accumulation state based on the 3 measurements. Then, in the subsequent plural measurements, the control section 30 sets the transmission efficiency S3 as the optimum accumulation state more than the other transmission efficiencies S1 and S2, and performs the measurement. That is, as an example, 2 times of measurement of F4 and F8 are performed with the transmission efficiency S1, and 2 times of measurement of F5 and F9 are performed with the transmission efficiency S2, whereas 4 times of measurement of F6, F7, F10, and F11 are performed in total with the measurement at the transmission efficiency S3 which is the optimal accumulation state.

(Effect of modification 4)

(4) In the time-of-flight mass spectrometer according to modification 4 described above, in the time-of-flight mass spectrometer according to modification 3 described above, after the optimum accumulation state is determined, the determined optimum accumulation state is set to be larger than the other accumulation states in the subsequent multiple measurements.

By performing the measurement in the optimal accumulation state more than in the other accumulation states in this manner, the measurement accuracy of the ions designated by the operator or the ions having a smaller number of ions and a tendency to decrease the measurement accuracy can be improved.

(embodiment of the procedure)

In each of the above-described embodiments and modifications, a program for realizing the above-described functions of the time-of-flight mass spectrometer 100 may be recorded in a computer-readable recording medium, and the program recorded in the recording medium may be read and executed by a computer system. The term "computer System" as used herein includes an OS (Operating System) and hardware of peripheral devices. The "computer-readable recording medium" refers to a removable recording medium such as a flexible disk, a magneto-optical disk, an optical disk, and a memory card, and a storage device such as a hard disk drive incorporated in a computer system. The "computer-readable recording medium" may further include: a medium that dynamically holds a program for a short time, such as a communication line when the program is transmitted via a network such as the internet or a communication line such as a telephone line; a medium that holds a program for a fixed time such as a volatile memory in a computer system serving as a server or a client in this case. The program may be a program for realizing a part of the functions, or may be a program realized by combining the functions with a program recorded in a computer system.

The program can be provided by a recording medium such as a CD-ROM or a data signal such as the internet. For example, the control unit 30 provided with the CPU 31, the memory 32, and the hard disk drive 33 in fig. 1 receives the supply of the program via the CD-ROM. The control unit 30 has a connection function to connect to the network NW. The server 35 connected to the network also functions as a server computer that provides the program, and transfers the program to a recording medium such as the hard disk drive 33. That is, the program is transmitted as a data signal by a carrier wave and transmitted via the network NW. In this manner, the program can be provided as a computer program product that can be read by a computer in various forms such as a recording medium and a carrier wave.

Fig. 7 shows an example of a flowchart in which the CPU 31 executes a program for controlling the time-of-flight mass spectrometer 100 according to modification 4 to control the ion introduction unit 1, the flight tube 14, and the control unit 30 of the time-of-flight mass spectrometer 100.

First, in step S101, measurement conditions such as an ion accumulation state (e.g., the transmission efficiency S of the ion transmission optical system 12 of the ion introduction unit 1) of the first N measurements (N is an arbitrary natural number, for example, 3) are determined.

In step S102, the program controls the control unit 30 to set the transfer efficiency S of the ion transfer optical system 12 of the ion introduction unit 1 and the accumulation time of the ion trap 22, which are measured J (J is 1 or more and N or less). Then, in step S103, the program control unit 30 applies a voltage to the orthogonal acceleration electrode 16 to perform the J-th measurement.

In step S104, it is determined whether or not the measurement has been performed N times, and if N times have been measured, the process proceeds to step S105, and if N times have not been measured, the process returns to step S102.

In step S105, the program controls the control unit 30 to determine an optimal accumulation state from the results of the above-described N measurements. The method of determining the optimal accumulation state is as described above. Then, in step S106, the measurement conditions for the M subsequent measurements (M is an arbitrary natural number) are determined so that the measurement in the optimal accumulation state determined in step S105 is performed more than the other accumulation states.

In step S107, the program controls the control unit 30 to set the transfer efficiency S of the ion transfer optical system 12 of the ion introduction unit 1 and the accumulation time of the ion trap 22, which are measured at the K-th time (K is 1 or more and M or less). Then, in step S108, the program controls the control unit 30 to apply a voltage to the orthogonal acceleration electrode 16, thereby performing the K-th measurement.

In step S109, it is determined whether or not the measurement has been performed M times, and if M times have been measured, the process proceeds to step S110, and if M times have not been measured, the process returns to step S107.

In step S110, the program causes the control unit 30 to analyze the measurement result, such as the calculation of the mass-to-charge ratio of each detected ion, based on the measurement result. As described above, processing is also performed to remove unnecessary portions (portions other than the portion corresponding to the designated ion) from the measurement result indicating the relationship between the amount of the detected ion and the flight time as necessary.

In step S111, the measurement results obtained by the analysis and various processes are displayed on the display unit 34 or accumulated in the database.

In step S112, it is determined whether the optimal accumulation state determined in step S105 is appropriate, that is, whether it is necessary to change the optimal accumulation state, based on the measurement result and the measurement result after the analysis and various processes are performed. If it is determined that the change is necessary, the process proceeds to step S101, and after changing each measurement condition N times, the process from step S101 onward is performed again. If it is determined that no change is necessary, the measurement is terminated.

Further, not all of the steps of the flowchart shown in fig. 7 are necessarily performed. For example, the steps S106 to S109 may be omitted.

In the above, although the various embodiments and the modifications have been described, the present invention is not limited to these. The embodiments may be applied individually or in combination. Other modes contemplated within the scope of the technical idea of the present invention are also included within the scope of the present invention.