JP2004335417A - Method and device for ion trap mass spectrometry - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for ion trap mass spectrometry capable of improving the sensitivity of MS<SP>n</SP>analysis of an ion trap mass spectrometry device. <P>SOLUTION: A first ion guide 21, a slit electrode 22, and a second ion guide 23 are provided in a previous stage of an ion trap 31, for rapidly accelerating ion to cause a collision induction dissociation. A sample separated in a separation column 4 is ionized by an ion source 5, and the collision induction dissociation is caused by the first ion guide 21, the slit electrode 22 and the second ion guide 23 to perform MS<SP>2</SP>. The ion through MS<SP>2</SP>is introduced to the ion trap 31, to perform MS<SP>3</SP>in the ion trap 31. By limiting the operation inside the ion trap 31 to MS<SP>3</SP>, the operation time of the ion trap 31 is reduced to increase the number of operations in a certain period of time, thus made possible to improve detection sensitivity. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ion trap mass spectrometry method and apparatus.
[0002]
[Prior art]
A mass spectrometer is a device that adds a charge to a sample molecule to perform ionization, separates generated ions into a mass-to-charge ratio by an electric or magnetic field, and measures the amount as a current value with a detector.
[0003]
This mass spectrometer has high sensitivity and is excellent in quantitativeness and identification ability as compared with a general analyzer.
[0004]
In recent years, in the life science field, attention has been paid to peptide analysis instead of genome analysis, and the effectiveness of mass spectrometers having high sensitivity and excellent identification ability has been re-evaluated.
[0005]
When a sample is measured with a mass spectrometer, a current value in mass-to-charge ratio units is obtained. This is called a mass spectrum. This mass spectrum differs depending on the structure of the sample to be measured, and information on the structure of the sample can be obtained from the pattern of the mass spectrum.
[0006]
However, the constituent components in the sample may be complicated, or the obtained mass spectrum information may be insufficient for specifying the components. Particularly, in a mass spectrometer, molecular ions are separated based on a mass-to-charge ratio. Therefore, even if the structures have different structures, it is difficult to distinguish molecular ions when the mass-to-charge ratio is the same.
[0007]
To solve this, MS ⁿ analysis was devised. And the MS ⁿ analysis, captures the molecular ion in the mass spectrometer to eliminate ions other than specific mass number, by causing collisions with the selected molecular ions and neutral molecules, the portion of the molecular ion binding This is a method of measuring broken and broken ions.
[0008]
Collision with a neutral molecule to break the bond of a selected molecular ion is called collision-induced dissociation (CID), and MS ² or MS is determined by the number of repetitions of a series of operations including ion uptake, ion selection, and collision-induced dissociation. ³ and so on.
[0009]
Since bonds between atoms in a molecule have different bond energies depending on the structure and the type of bond, a portion having a lower bond energy is broken by collision-induced dissociation.
[0010]
By giving molecular ions the kinetic energy necessary to break molecular ion bonds when molecular ions collide with neutral molecules, fragment ions unique to molecular ions are generated, and the structure of molecular ions can be known. it can.
[0011]
Further, if many number of repetitions of MS ⁿ analysis, it is possible to obtain more structural information.
[0012]
There are various types of mass spectrometers depending on the operation and configuration for separating ions. One of the configurations suitable for performing ^MSn analysis is an ion trap mass spectrometer.
[0013]
The ion trap mass spectrometer forms a quadrupole electric field such that ions of a specific mass-to-charge ratio stay in the ion trap, and performs ion selection and collision-induced dissociation by changing the quadrupole electric field. it can.
[0014]
Then, after the collision induced dissociation, without inducing the detector ions, it is performed again ion selection and collision-induced dissociation the generated ions by collision induced dissociation, be performed a plurality of times of MS ⁿ analysis It becomes possible.
[0015]
Known techniques of an ion trap mass spectrometer include those described in Patent Literature 1 and Patent Literature 2.
[0016]
In the technique described in Patent Literature 1, the ionization chamber is partitioned by a partition wall into a second space in which the ion trap is disposed and a first space in which the ion trap is not disposed. The partition wall is provided with a slit for communicating the first space and the second space.
[0017]
By increasing the gas pressure in the first space by forming the partition wall, the irradiation volume of the sample gas with ultraviolet light is increased to increase the amount of ions generated, and the measurement sensitivity of the mass spectrometer is improved. Is configured.
[0018]
In the technique described in Patent Document 2, a plurality of ion trap mass spectrometers having different measurement mass number ranges are arranged in one analyzer. The ions are guided into the deflector by the ion lens and the ion guide, and are introduced into one of the two mass spectrometers due to a difference in mass number according to the electric field generated by the deflector. .
[0019]
A gate electrode is arranged before the ion introduction of each mass spectrometer, and a lens electrode is arranged after the ion introduction. The voltages applied to the gate electrode and the lens electrode allow the introduction of ions from outside during ion accumulation, and permit the extraction of ions from the ion trap mass spectrometer to the outside during ion detection.
[0020]
[Patent Document 1]
JP 2002-181790 A [Patent Document 2]
JP-A-11-144675
[Problems to be solved by the invention]
However, when performing MS ⁿ analysis by ion trap mass analyzer of the prior art has the following problems.
[0022]
(A) Ions given in the collision-induced dissociation with more kinetic energy than can be stably present in the quadrupole electric field cannot be confined in the ion trap, and are discharged out of the ion trap. Therefore, when MS ⁿ is repeated, the detection sensitivity decreases.
[0023]
(B) If the time spent for collision-induced dissociation is short, sufficient energy for the dissociation reaction cannot be given to the molecular ions, and the efficiency of generating the cleaved ions decreases. Therefore, it is necessary to give sufficient time to the collision-induced dissociation, but the time for one sequence becomes longer, and the detection sensitivity per unit time decreases.
[0024]
The ion trap mass spectrometer cannot capture new ions during ion separation or collision-induced dissociation, during which time the ions transported from the ion source are not used for measurements.
[0025]
In other words, the greater the number of repetitions of MS ⁿ and the longer the time spent for ion separation and collision-induced dissociation, the more the loss of ions shown in (a) and the number of ions generated in the ion source shown in (b) are measured. A reduction in efficiency is encouraged.
[0026]
An object of the present invention is to realize an ion trap mass spectrometry method and apparatus capable of improving the sensitivity of MS ⁿ analysis of an ion trap mass spectrometer.
[0027]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is configured as follows.
[0028]
(1) In the ion trap mass spectrometry method, a first ion separation is performed for each sample component, the separated sample is ionized, the first collision-induced dissociation of the ionized sample is performed, and the sample is led to an ion trap. After performing the second ion separation inside, the second collision-induced dissociation is performed to perform mass separation and detect ions.
Alternatively, after performing the second ion separation in the ion trap, the second collision-induced dissociation is performed, and the ions are mass-separated at a mass-to-charge ratio in a mass separation unit disposed downstream of the ion trap, and the ions are separated. To detect.
[0029]
(2) Preferably, in the above (1), the first collision-induced dissociation is performed by a plurality of electrodes having a potential gradient.
[0030]
(3) In the ion trap mass spectrometer, a sample introduction unit for introducing a sample, a sample separation unit for performing the first ion separation for each component of the introduced sample, an ionization unit for ionizing the separated sample, and an ionization unit An ion guide for conducting a first collisional dissociation of a sample to an ion trap; an ion trap for confining guided ions to perform second ion separation, second collision-induced dissociation, and mass separation; and mass separation. And a detector for detecting the selected ions.
[0031]
(4) In the ion trap mass spectrometer, a sample introduction unit for introducing a sample, a sample separation unit for performing the first ion separation for each component of the introduced sample, an ionization unit for ionizing the separated sample, and An ion guide section for conducting the first collision-induced dissociation of the sample to the ion trap; an ion trap for confining the guided ions to perform the second ion separation and the second collision-induced dissociation; And a detection unit that detects the mass-separated ions.
[0032]
(5) Preferably, in the above (3) or (4), the ion guide section has a plurality of electrodes having a potential gradient.
[0033]
(6) Preferably, in the above (5), the plurality of electrodes are applied with a first ion guide electrode to which a first voltage is applied and a second voltage lower than the first voltage. A second ion guide electrode, an eight slit electrode disposed between the first ion guide electrode and the second ion electrode, to which a third voltage higher than the first voltage is applied; The sample passed from the first guide electrode passes through the slit electrode and the second electrode.
[0034]
According to the present invention, performing a first ion separation is MS ^2, then rapidly accelerated ions by ion guide for taking ions into the ion trap performs a collision induced dissociation, MS ³ in the ion trap Only configured to do.
[0035]
Therefore, an ion trap mass spectrometry method and apparatus capable of improving the sensitivity of MS ⁿ analysis of the ion trap mass spectrometer can be realized.
[0036]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0037]
FIG. 1 is a schematic configuration diagram of a mass spectrometer according to an embodiment of the present invention. In FIG. 1, a mobile phase 1 is introduced into a flow channel by a liquid sending pump 2. Then, the sample is introduced from the sample injector 3 and is introduced into the separation column 4.
[0038]
The sample introduced into the separation column 4 is separated into component units by the separation column 4 and sent to the ion source 5.
[0039]
The ion source 5 is in the form of a capillary, and electrostatic spraying is performed by applying a high voltage of several kV to its tip. The ions generated by the electrostatic spray are attracted to the first pore 11 charged to several hundred volts, introduced into the vacuum chamber 51, and sent to the first ion guide 21 through the second pore 12. .
[0040]
The inside of the vacuum chamber 51 is maintained at a degree of vacuum of about 10 ⁻³ Torr by vacuum evacuation by the turbo molecular pumps 61 and 62 and the rotary pump 65 and natural suction from the first pores 11.
[0041]
An octupole is used for the first ion guide 21. When a high-frequency voltage is applied to the first ion guide 21, a high-frequency electric field is formed and the ions are converged.
[0042]
Here, in one embodiment of the present invention, the slit electrode 22 and the second ion guide 23 are arranged at the subsequent stage of the first ion guide 21, and a gradient of potential described later is formed between the slit electrode 22 and the second ion guide 23, so that collision-induced dissociation is performed. The ions are induced, and the ions with molecular bonds broken are transported to the ion trap 31.
[0043]
An Einzel lens is used for the slit electrode 22, and an octupole similar to the first ion guide 11 is used for the second ion guide 23 to form a high-frequency electric field.
[0044]
The slit electrode 22 is disposed in a vacuum chamber 51, and the second ion guide 23 is disposed in a vacuum chamber 52.
[0045]
Here, as shown in FIG. 2, in order to cause collision-induced dissociation near the slit electrode 22, the offset voltage Vg1 of the first ion guide 21, the voltage Vs of the slit electrode 22, and the offset voltage Vg2 of the second ion guide 23 are set. , Vs>Vg1> Vg2.
[0046]
Since the voltage Vs is higher than the voltage Vg1, the ions are decelerated immediately before the slit electrode 22. The voltage Vg2 is smaller than the voltage Vg1, and has a large potential gradient with the voltage Vs. The ions are rapidly accelerated by the steep potential gradient. The rapidly accelerated ions repeatedly collide with neutral molecules such as air entering the vacuum chamber 51 from the first pores 11, and collision-induced dissociation occurs.
[0047]
According to the inventor's experiments, for example, collision-induced dissociation occurred when the voltage Vs was set to 45 V, the voltage Vg1 was set to 50 V, and the voltage Vg2 was set to 35 V. By adjusting the voltage Vs of the slit electrode 22, the degree of collision-induced dissociation can be changed.
[0048]
The ions whose molecular bonds have been broken by the collision-induced dissociation are converged by the second ion guide 23 and transported to the ion trap 31. Then, MS ³ is performed in the ion trap 31 and converged by the focus electrode 32 at the subsequent stage, and ions are detected by the detector 41.
[0049]
In one embodiment of the present invention, since only MS ³ is performed in the ion trap 31, the operation time of the ion trap 31 can be shortened, and the sensitivity can be improved by increasing the number of operations per unit time.
[0050]
FIG. 3 is an explanatory diagram using a mass spectrum for the operation of the ion trap mass spectrometer due to the collision-induced dissociation of the slit electrode 22 in one embodiment of the present invention.
[0051]
FIG. 4 is an explanatory view using a mass spectrum for the operation of an ion trap mass spectrometer, in which a slit electrode is not provided and collision-induced dissociation is performed only in the ion trap, unlike the present invention.
[0052]
The horizontal axis of the mass spectrum in FIGS. 3 and 4 is the mass-to-charge ratio, and the vertical axis is the current value of the detector. Each mass spectrum in FIGS. 3 and 4 is a mass spectrum predicted when ions are detected in each step of ion separation and collision-induced dissociation.
[0053]
First, the sample of the mass spectrum shown in (1) of FIG. 3 is ionized by the ion source 5 after the MS ² is separated in the separation column 4 ((2) in FIG. 3). After passing through the first ion guide 21, collision-induced dissociation is performed by the slit electrode 22 and the second ion guide 23 ((3) in FIG. 3).
[0054]
Then, incorporated into the ion trap 31 ((4 in FIG. 3)), for performing the MS ^3, the separation of the ions is performed to leave the desired ions from the trapped ions (in FIG. 3 (5) ). Then, the separated ions are subjected to collision-induced dissociation to generate ions ((6) in FIG. 4), mass separation and discharge are performed, and the detector 41 detects them.
[0055]
On the other hand, in the case of the example shown in FIG. 4, the sample of the mass spectrum shown in FIG. 4A is subjected to component separation in the separation column (FIG. Ionized. Then, after passing through the ion guide, it is taken into the ion trap ((3) in FIG. 4).
[0056]
The ions are separated from the trapped ions so that the target ions remain ((4) in FIG. 4). Then, the separated ions are subjected to collision-induced dissociation to generate their daughter ions ((5) in FIG. 4) and confined in an ion trap.
[0057]
Further, in order to perform MS ³ , target daughter ions are separated from the mass spectrum shown in (5) of FIG. 4 ((6) of FIG. 4), and collision-induced dissociation is performed to generate grandchild ions ( ((7) of FIG. 4). Then, mass separation and discharge are performed, and detection is performed by a detector.
[0058]
Thus, as in the example of FIG. 4, in the example of performing collision-induced dissociation only in the ion trap, to do MS ^3, in the ion trap, a collision-induced dissociation of the two ion separation and twice There is a need to do.
[0059]
In the case of the ion trap mass spectrometer of the example shown in FIG. 4, since the operations from mass spectra (3) to (7) shown in FIG. 4 are performed in the ion trap, the voltage sweep time and the ion orbit It took about 140 msec for one sequence, depending on the sample, including the stabilization time.
[0060]
On the other hand, in the case of the embodiment of the present invention shown in FIG. 3, the ion separation of MS ² is continuously performed in the separation column 4 and the collision-induced dissociation is performed in the slit electrode 22. ^Since only Step ³ is performed, the time for ion separation and collision-induced dissociation of MS ² can be eliminated.
[0061]
As a result, in one embodiment of the present invention, the time required for one sequence can be reduced to about 80 msec, the number of operations of the ion trap 31 per unit time increases, the S / N ratio improves, and Sensitivity can be increased. In particular, in the case of a molecular ion having a large binding energy, a long time is required for collision-induced dissociation, so that the effect of the present invention is great.
[0062]
Here, the example shown in FIG. 4 is a case where the collision-induced dissociation is performed only in the ion trap, and is an example in which a separation column is used.
[0063]
FIG. 5 is an explanatory diagram using a mass spectrum for the operation of the ion trap mass spectrometer when the collision-induced dissociation is performed only in the ion trap and no separation column is used.
[0064]
In the case of the example of FIG. 5, after the sample of the mass spectrum shown in (1) is taken into the ion trap, ion separation → collision-induced dissociation → ion separation → collision-induced dissociation is performed, and both MS ² and MS ³ are performed. This is performed in the ion trap.
[0065]
Therefore, in the case of the example of FIG. 5, as in the example of FIG. 4, about 140 msec is required for one sequence.
[0066]
As described above, according to one embodiment of the present invention, ion separation as MS ² is performed by the separation column, and then the ions are rapidly accelerated by the ion guide for taking the ions into the ion trap, thereby causing collision-induced dissociation. Is performed, and only MS ³ is performed in the ion trap. Therefore, an ion trap mass spectrometry method and apparatus capable of improving the sensitivity of MS ⁿ analysis of the ion trap mass spectrometer can be realized.
[0067]
Note that in the embodiment described above, collision-induced dissociation to near offset voltage of the voltage of the slit electrode 22 first ion guide 21 is not performed, operation of the ion trap becomes MS ^2.
[0068]
Further, in the above-described embodiment, the ion guide is described as an octopole, but a multipole such as a quadrupole or a hexapole may be used. If the mass separation operation is performed in the first ion guide 21 before the slit electrode 22, the accuracy of ion separation can be improved.
[0069]
Further, if a mass separation unit such as a time-of-flight mass spectrometer is arranged at the subsequent stage of the ion trap 31, the discharge from the ion trap 31 can be operated without mass separation, so that the time required for one sequence is reduced. Can be further reduced.
[0070]
【The invention's effect】
According to the present invention, since MS ² is performed before the ion trap, only MS ³ needs to be performed in the ion trap. Therefore, the operation time of the ion trap at the time of MS ³ is reduced, and ions per unit time are reduced. The number of times of operation of the trap increases, the S / N ratio improves, and the detection sensitivity can be improved.
[0071]
Therefore, an ion trap mass spectrometry method and apparatus capable of improving the sensitivity of MS ⁿ analysis of the ion trap mass spectrometer can be realized.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a mass spectrometer according to an embodiment of the present invention.
FIG. 2 is a conceptual diagram of a potential gradient applied to a first ion guide, a second ion guide, and a slit electrode.
FIG. 3 is an explanatory diagram illustrating an operation of the ion trap mass spectrometer according to the embodiment of the present invention.
FIG. 4 is a diagram illustrating the operation of an ion trap mass spectrometer in one example in which collision-induced dissociation is performed only in the ion trap, different from the present invention.
FIG. 5 is a diagram illustrating the operation of an ion trap mass spectrometer in another example in which collision-induced dissociation is performed only in the ion trap, different from the present invention.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 mobile phase 2 liquid sending pump 3 sample injector 4 separation column 5 ion source 11 first pore 12 second pore 21 first ion guide 22 slit electrode 23 second ion guide 31 ion trap 32 focus electrode 41 ion detector 51 , 52 Vacuum chamber 61, 62 Turbo molecular pump 65 Rotary pump

Claims (7)

The sample was subjected to the first ion separation for each component, the separated sample was ionized, the first collision-induced dissociation of the ionized sample was performed, and the sample was led to the ion trap, and the second ion separation was performed in the ion trap. Thereafter, a second collision-induced dissociation is performed, mass separation is performed, and ions are detected. The sample was subjected to the first ion separation for each component, the separated sample was ionized, the first collision-induced dissociation of the ionized sample was performed, and the sample was led to the ion trap, and the second ion separation was performed in the ion trap. Thereafter, a second collision-induced dissociation is performed, and the ions are mass-separated at a mass-to-charge ratio in a mass separation unit disposed downstream of the ion trap to detect the ions. 3. The ion trap mass spectrometry method according to claim 1, wherein the first collision-induced dissociation is performed by a plurality of electrodes having a potential gradient. A sample introduction unit that introduces a sample, a sample separation unit that performs first ion separation on the introduced sample in component units,
An ionization unit for ionizing the separated sample;
An ion guide section for performing a first collision-induced dissociation of the ionized sample and leading to an ion trap;
An ion trap for confining the guided ions and performing second ion separation, second collision-induced dissociation, and mass separation;
A detection unit that detects mass-separated ions,
An ion trap mass spectrometer comprising: A sample introduction unit that introduces a sample, a sample separation unit that performs first ion separation on the introduced sample in component units,
An ionization unit for ionizing the separated sample;
An ion guide section that performs a first collisional dissociation of the ionized sample and guides the ionized sample to an ion trap;
An ion trap for confining the guided ions and performing a second ion separation and a second collision-induced dissociation;
A mass separation unit for separating ions by mass-to-charge ratio,
A detection unit that detects mass-separated ions,
An ion trap mass spectrometer comprising: 6. The ion trap mass spectrometer according to claim 4, wherein the ion guide section has a plurality of electrodes having a potential gradient. 7. The ion trap mass spectrometer according to claim 6, wherein the plurality of electrodes include a first ion guide electrode to which a first voltage is applied and a second ion guide electrode to which a second voltage smaller than the first voltage is applied. An ion guide electrode, and an eight slit electrode disposed between the first ion guide electrode and the second ion electrode, to which a third voltage higher than the first voltage is applied, and an ionized sample. Is an ion trap mass spectrometer characterized by being passed through a slit electrode and a second electrode from a first guide electrode.

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