JPH087831A - Multistage time of flight type mass spectrometry device - Google Patents

Abstract

PURPOSE:To obtain a multistage time of flight type mass spectrometry device which can measure the masses of parent ions and daughter ions accurately at a high discrimination. CONSTITUTION:Ions generated from a pulse ion source 1 pass through electrostatic analyzers C1 and C2 in order, and reach to an ion detector 2. No.3 is an impact chamber on an ion passage between the ion analyzers C1 and C2, which is provided at the position where the time focusing is accomplished by observing from the ion source side and from the ion detector side. No.4 is an ion source power source to control the operation of the ion source 1, No.5 is an electric field power source to set the analyzing energy of the electrostatic analyzer C1, No.6 is an electric field power source to set the analyzing energy of the electrostatic analyzer C2, No.7 is a detecting circuit to pick up a detecting signal from the ion detector 2, and No.8 is a control circuit to deliver a trigger signal of the pulse operation to the ion sporce power source 4, a control the electric field power sources 5 and 6, and furthermore, to control to take in the detecting signal obtained from the detecting circuit 7, and it has a memory 9 to store the taken-in detecting signal, and a display device 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a time-of-flight mass spectrometer, and more particularly to a multi-stage time-of-flight mass spectrometer having a plurality of fan-shaped electrostatic analyzers arranged in a flight path of ions.

[0002]

2. Description of the Related Art In recent years, a time-of-flight mass spectrometer has come to be widely used for structural analysis of substances due to the development of pulse ionization method using a laser. The two major features of mass spectrometry using time-of-flight are as follows. 1) There is no theoretical limit to the measurable mass range, and small to large masses can be measured one after another. 2) High sensitivity because all ions produced by the ion source are used for measurement.

On the other hand, the tandem mass spectrometry method in which ions are fragmented in mass spectrometry and the masses of the ion before splitting (parent ion) and the ion after splitting (daughter ion) are measured are a magnetic field type mass spectrometer and a quadrupole. An apparatus that is effectively used by using a mass spectrometer and that performs tandem mass spectrometry with a time-of-flight mass spectrometer is also proposed in Japanese Patent Publication No. 332018.

[0004]

However, in the apparatus proposed in Japanese Examined Patent Publication No. 3-32018, the mass of the parent ion is determined by the flight time of the ion, and the mass of the daughter ion is determined by the energy of the daughter ion. However, there is a problem in that mass resolution and determination accuracy of parent and daughter ions are limited due to the spread of energy during ion generation and fragmentation.

The present invention improves the above-mentioned points, improves the mass resolution and determination accuracy of both parent ions and daughter ions, and further allows multistage time-of-flight mass spectrometry capable of splitting ions two or more times. The purpose is to provide a device.

[0006]

To achieve this object, the multistage time-of-flight mass spectrometer of the present invention comprises means for splitting ions in the flight path of the ions between the pulsed ion source and the ion detector. Along with the provision of an ion flight path between the ion source and the splitting means and between the splitting means and the ion detector, an ion flight path is provided between the ion source and the splitting point and between the splitting point and the ion detector. At least one fan-shaped electrostatic analyzer is arranged so that the convergence condition for the flight time is satisfied.

Further, the second multi-stage time-of-flight mass spectrometer of the present invention is provided with a plurality of means for splitting ions in the flight path of the ions between the pulsed ion source and the ion detector, and the ion source and the first To the ion source and the splitting point, from the splitting point to the next splitting point, in the ion flight path between the splitting means, the splitting means and the splitting means, and the last splitting means and the ion detector. And at least one fan-shaped electrostatic analyzer is arranged so that the convergence condition for the flight time of ions is satisfied between the split point and the ion detector.

[0008]

In the present invention, since the fan-shaped electrostatic analyzer is arranged so that time convergence is established between the pulsed ion source and the splitting point and between the splitting point and the ion detector, the energy of the parent ions is spread. However, the parent ions of the same mass reach the splitting point at the same time, and even if the kinetic energy of the daughter ions spreads due to the splitting, they reach the ion detector in the same flight time, so the mass resolution And mass determination accuracy is high. An embodiment of the present invention will be described below in detail with reference to the drawings.

[0009]

1 is an ion optical diagram showing an embodiment of the present invention. In the figure, the ions generated from the pulse ion source 1 sequentially pass through the two concentric cylindrical electrostatic analyzers C1 and C2 and reach the ion detector 2. 3 is an electrostatic analyzer C
The collision chamber is located in the ion passage between C1 and C2.
Reference numeral 4 is an ion source power source for controlling the operation of the ion source, 5 is an electric field power source for setting the analysis energy (electric field strength) of the electrostatic analyzer C1, and 6 is the analysis energy (electric field strength) of the electrostatic analyzer C2. An electric field power source, 7 is a detection circuit for extracting a detection signal from the ion detector 2, 8 is a trigger signal for pulse operation to the ion source power source 4, and controls the electric field power sources 5 and 6,
Further, it is a control circuit for controlling the capture of the detection signal obtained from the detection circuit 7, and includes a memory 9 for storing the captured detection signal and a display device 10.

The collision chamber 3 has a gas having an appropriate pressure present therein, and splits parent ions that have entered through the electrostatic analyzer C1 by collision with gas molecules. The daughter ions generated by the splitting exit the collision chamber 3 and then travel toward the ion detector 2 via the electrostatic analyzer C2.

In the electrostatic analyzers C1 and C2, the ions of the same mass emitted from the ion source at the same time are simultaneously incident on the collision chamber (so-called time convergence), and the ions of the same mass simultaneously emitted from the collision chamber are simultaneously detected. Various conditions are selected so as to reach the container 2.

Now, the time-converging action of the sector electric field will be described. When the acceleration energy applied to the ions in the ion source is U, the velocity v of the ion of mass m is v = (2U / m) ^1/2 (1) from the equation of kinetic energy. The time T required for the ion to fly the distance L is inversely proportional to the velocity of the ion, and T = L / v = L (m / 2U) ^1/2 (2)

Therefore, ions having the same acceleration energy applied by the pulsed ion source and leaving the ion source at the same time are delayed by the distance L to the ion having the smaller mass and larger velocity, and the larger the mass and slower velocity. hand,
It arrives sequentially in the required time according to the equation (2). From the ion detector arranged there, a time-series mass spectrum signal in which incident ions are sequentially detected is obtained. This required time T
From this, the mass m of the ions can be obtained based on the equation (2).

In an ideal time-of-flight mass spectrometer, since ions of the same mass reach the ion detector at the same time,
The peak width of each peak of the spectrum signal is infinitesimally small.
However, in an actual device, it is inevitable that the peak will spread. In the time-of-flight mass spectrometer,
This time-of-flight spread Δt is important because it determines the mass resolution of the device. This Δt can be expressed as follows by a first-order approximation of ion optics. Δt = T _X x _o + T _α α _o + T _δ δ _o (3) where x _o is the slit width of the ion source, α _o is the incident angle of incident ions, and δ _o is the energy spread of the ions. T _X , T _α and T _δ are constants determined by the device. Here, using a sectoral electrostatic analyzer, T _X = T _α = T _δ
If the device is designed so that = 0, Δt becomes zero, and a device with high resolution can be realized. This is the time focusing effect of the sector electric field.

The position and rotation angle of the electrostatic analyzer C1 are selected so that time focusing is established at the position of the collision chamber 3 for the ions emitted from the ion source 1. The electrostatic analyzer C2 also has a collision chamber. The position of the ion emitted from the ion detector 2 is adjusted so that time focusing is established,
The rotation angle is selected.

Next, the principle of tandem mass spectrometry in the time-of-flight mass spectrometer will be described. Assuming that the mass of the parent ion is m ₁ , the velocity is v _1, and the mass of the daughter ion generated by the splitting in the collision chamber is m ₂ , the kinetic energy U ₂ of the daughter ion and the velocity V ₂ are given by Given.

U ₂ = (m ₂ / m ₁ ) U−ΔU (4) v ₂ = v ₁ −Δv (5) where U is the acceleration energy of the parent ion, and ΔU and Δv are in the splitting process. It is the spread of kinetic energy and velocity distribution.

Since the time of flight from the ion source to the detector is the same as that when the velocity is v ₁ due to the time focusing effect of the electrostatic analyzer even when Δv is present at the time of fragmentation of the ion, T = L / v ₁ = L (m ₁ / 2U) ^1/2 ...
(6)

By using this equation (6), the mass m ₁ of the parent ion before fragmentation can be determined from the flight time.

On the other hand, the energy of the daughter ions can be measured by changing the intensity of the electrostatic analyzer C2. here,
Since ΔU can be corrected from the flight time, the case of ΔU = 0 should be considered. In that case, m ₂ is given by m ₂ = (U ₂ / U) m ₁ (7) from the equation (4). From the formulas (6) and (7), the mass m _{2 of the} daughter ion having the energy U ₂ that has passed through the fan-shaped analyzer C ₂ set to the analysis energy U ₂ and the mass m of the parent ion thereof
You can ask for _one .

Hereinafter, a specific measurement procedure will be described in detail with reference to the timing chart shown in FIG. FIG. 2a shows the operation timing of the pulsed ion source 1, in which ions (parent ions) are repeatedly generated in a pulsed manner at an appropriate measurement repetition period, and a constant acceleration energy U is given to the electrostatic analyzer C1 and ejected. The analysis energy of the electrostatic analyzer C1 is
As shown in FIG. 2b, since it is fixed to U and is given a time-focusing action, the ions to which the energy U is added are introduced into the collision chamber 3 in order from the ion having the smaller mass with a smaller time lag. Incident in sequence. Then, the daughter ions generated by the collision with the gas molecules in the collision chamber 3 are generated together with the parent ions which have not collided and have not been decomposed.
To the electrostatic analyzer C2.

The analysis energy of this electrostatic analyzer C2 is
As shown in FIG. 2C, the control circuit 8 controls the value from the initial value U to 0 (zero) step by step in small steps at each measurement repetition. Therefore, at the time of measuring the initial value U, only the parent ions that have not been split in the collision chamber pass through the electrostatic analyzer C2, reach the ion detector 2, and reach the detection signal D ₁ in FIG. Mass spectrum signal) is obtained. This detection signal is taken in by the control circuit 8 as a function of the elapsed time (time of flight) from the trigger signal of the pulse operation of the ion source 1 and the ion intensity,
It is stored in the memory 9 in association with the analysis energy value at that time.

After that, the measurement is repeated while the analysis energy of the electrostatic analyzer C2 is gradually reduced, and only when there is a daughter ion having an energy equal to the analysis energy at that time, the daughter ion is electrostatically analyzed. It passes through C2, reaches the ion detector 2, and is detected. D ₃ in FIG. 2d is
Shows the detection signal when such daughter ions are present, D
₂ , D ₄ and D ₅ indicate detection signals when there is no daughter ion having an energy equal to the analysis energy at that time.

In this way, the measurement is repeated, for example, N times until the analysis energy of the electrostatic analyzer C2 = 0, and the measurement is completed. The N detection signals obtained by the end of the measurement are
The memory 9 attached to the control circuit 8 is stored and stored in association with the analysis energy values of N stages.

FIG. 3 shows a two-dimensional mass in which a series of detection signals stored and stored in the memory 9 are displayed on the display device 10 with the daughter ion energy on the vertical axis, the flight time on the horizontal axis, and the ion intensity, for example, as brightness. An example of a spectrum is shown. The mass of the parent ion is calculated based on the flight time using the equation (6), and is displayed on the horizontal axis in comparison with the flight time.

As an analytical method of tandem mass spectrometry,
(A) Analysis of all daughter ions derived from a specific parent ion, (B) Analysis of all parent ions derived from a specific mass of daughter ions, (C) All splits that lose a constant mass of neutrals There are three types of process analysis.

These analyzes can be carried out as follows based on the two-dimensional mass spectrum obtained by the series of measurements shown in FIG. (A) Analysis of all daughter ions derived from a particular parent ion When a particular parent ion splits, the flight time of the daughter ion is
Regardless of its mass, it takes a constant value given by equation (6). Therefore, the daughter ion derived from the parent ion having a mass of 1000 has a parent ion mass on the horizontal axis in FIG.
Appears on a straight line (a) drawn vertically from 1000.
For example, this straight line is displayed as a vertical cursor on the display device 10, and this vertical cursor is used as a parent ion (eg, mass 100).
(0) When a series of signal intensity data on this vertical cursor is read out and displayed as a spectrum Sd in FIG. 3 when it is aligned with the position (0), daughters representing all daughter ions derived from the parent ion of mass 1000 are displayed. Ion spectra can be displayed. Further, it may be output on paper or the like by another output device.

FIG. 4 is a spectrum of daughter ions derived from the Hg8Cs ⁺ cluster ion of mercury cesium. The mass of the daughter ion is calculated from the mass and energy value of the parent ion using the equation (7). (B) Analysis of All Parent Ions Deriving Daughter Ions of Specific Mass When the analysis energy of the electrostatic analyzer C2 is changed, the mass of parent ions is m ₁ = (U / U ₂ ) from the formula (7). m ₂ is given by (8). At that time, the flight time T to be noted is
By substituting the equation (8) into the equation (6), it is given by T = L (m ₂ / 2U ₂ ) ^1/2 (9).

The curve (b) in FIG. 3 shows that m ₂ = 200
3 is a graph obtained by plotting the function of Expression (9) on the coordinate plane of FIG. 3 for m ₂ and 400. By reading out a series of signal intensity data on this curve and displaying it as a spectrum, it is possible to obtain a parent ion spectrum that represents all parent ions that derive the daughter ions of masses 200 and 400. (C) Analysis of all fission processes that lose a constant mass of neutral matter. If the mass of the parent ion is m ₁ and the mass of the daughter ion is m ₂ ,
Mass m _n of the lost neutrals is m _n = m ₁ -m _2. From the equation (6), m ₁ = [U / (U−U ₂ )] _mn (10) m ₂ = [U ₂ / (U−U ₂ )] _mn (11), which should be noted. The flight time is given by T = L [m _n / 2 (U−U ₂ )] ^1/2 (12) from the equations (8) and (10).

The curve (c) in FIG. 3 shows that m _n = 200.
And for the case of m _n = 400, it is plotted on the coordinate plane of Figure 3 the function of equation (12). By reading out a series of signal intensity data on this curve and displaying it as a spectrum, it is possible to obtain a so-called neutral loss spectrum that represents all parent ions that lose the neutral substances of masses 200 and 400.

In the above description, the time-of-flight spectrum as shown in FIG. 3 is measured over the entire area and stored in the memory, and then a straight line or a curve corresponding to the analysis method (A), (B) or (C) is used. The spectrum was obtained by taking out the above data, but when only one of the methods is performed, a straight line (a), a curve (b) or (of FIG. 3 is performed while performing a series of measurements according to the timing of FIG. If only the analysis energy U ₂ and flight time T data corresponding to c) are captured and stored, it is not necessary to capture other unnecessary data.

FIG. 5 is a schematic view showing another embodiment of the present invention. The present embodiment is characterized in that, in addition to the embodiment of FIG. 1, the third electrostatic analyzer C3 and the second collision chamber 12 are arranged between the electrostatic analyzer C2 and the ion detector 2. There is.
Reference numeral 11 is an electric field power source for the electrostatic analyzer C3, and the control circuit 8
Controlled by. The collision chamber 12 is arranged at a position where time focusing is established for ions emitted from the collision chamber 3 and passed through the electrostatic analyzer C2, and similarly, ions emitted from the collision chamber 12 are located at the position of the ion detector 2. The position and rotation angle of the electrostatic analyzer C3 are selected so that time focusing is established.

FIG. 6 is a timing chart showing the operation timing of the embodiment of FIG. FIG. 6 a shows the operation timing of the pulsed ion source 1. FIG. 6b shows the analysis energy set in the electrostatic analyzer C1 and is fixed at the energy value U. FIG. 6c shows the analysis energy set in the electrostatic analyzer C2, which is fixed to the energy value U ₂₁ so that only the daughter ions generated in the collision chamber 3 having a specific energy value U ₂₁ are allowed to pass. Has been done. FIG. 6d shows the analysis energy set in the electrostatic analyzer C3, which is controlled by the control circuit 8 so as to decrease stepwise in small steps from the initial value U to 0 (zero) at each measurement repetition.

As a result, among the daughter ions generated in the collision chamber 3, only those having the daughter ion energy U ₂₁ that can pass through the electrostatic analyzer C2 enter the collision chamber 12 and the daughter ions are generated in the collision chamber 12. The grandchild ions generated by the fragmentation of the ions and having various energies reach the ion detector 2 when the analytical energy of the electrostatic analyzer C3, which is changed at each measurement repetition, matches the energy of each grandchild ion, and is detected. To be done.

The measurement is repeated N times, for example, until the grandchild ion analysis energy of the electrostatic analyzer C3 = 0, and the measurement is completed. The N detection signals obtained by the end of the measurement are stored in the memory 9 attached to the control circuit 8 in association with the N-stage grandchild ion analysis energy values.

After completion of the measurement, if a series of detection signals stored in the memory 9 are displayed on the display device 10 with the energy of the grandchild ion on the vertical axis, the flight time on the horizontal axis, and the ion intensity, for example, the brightness, The two-dimensional mass spectrum of the grandchild ion can be displayed in exactly the same manner as in 3.

FIG. 7 shows Hg4C among the daughter ions derived from the cluster ion Hg5Cs ^{+ of} mercury cesium.
The grandchild ion mass spectrum measured by selecting s ⁺ by the electrostatic analyzer C2 and guiding it to the collision chamber 12 is shown.

In the operation example shown in FIG. 6, the electrostatic analyzer C2 is fixed to a certain analysis energy value U ₂₁ , but the analysis energy value of this electrostatic analyzer C2 is also a series of measurement shown in FIG. The pulse ion source 1 is changed by gradually changing each time, and repeating the series of measurement of FIG. 6 at each step.
The grandchild ion spectra can be measured for all daughter ions derived from all parent ions generated in.

The present invention can be modified without being limited to the above-mentioned embodiments. The rotation angle of the electrostatic analyzer can be arbitrarily selected, and the number of electrostatic analyzers may be further increased. FIG. 8 shows an example in which four electrostatic analyzers having a rotation angle of approximately 270 ° are combined. Since the time convergence is satisfied at the three places indicated by the broken lines in the figure, if the collision chambers are arranged at all of the three places, more splitting processes can be investigated.

[0040]

As described above in detail, since a plurality of fan-shaped electrostatic analyzers are arranged in the present invention, a multistage flight capable of accurately measuring masses of parent ions and daughter ions with high resolution. A time type mass spectrometer is realized.

[Brief description of drawings]

FIG. 1 is an ion optical diagram showing an embodiment of the present invention.

FIG. 2 is a timing diagram showing an operation timing of the device of FIG.

FIG. 3 is a diagram showing an example of a two-dimensional mass spectrum displayed on a display device based on a series of detection signals stored and stored in a memory.

Figure 4: Mercury cesium cluster ion Hg8Cs ⁺
It is a figure which shows the spectrum of the daughter ion which split and were derived from.

FIG. 5 is an ion optical diagram showing an example of the present invention.

FIG. 6 is a timing chart showing the operation timing of the embodiment of FIG.

Fig. 7 Cluster ion Hg5Cs ^{+ of} mercury cesium
FIG. 7 is a diagram showing a mass spectrum of grandchild ions measured by selecting Hg4Cs ⁺ from the daughter ions generated by splitting from ## EQU1 ## by the electrostatic analyzer C2 and guiding it to the collision chamber 12.

FIG. 8 is an ion optical diagram showing an example of the present invention.

[Explanation of symbols]

 1 pulse ion source 2 ion detector 3,12 collision chamber 4 ion source power supply 5,6,11 electric field power supply 7 detection circuit 8 control circuit 9 memory 10 display device C1, C2, C3 concentric cylindrical electrostatic analyzer

Claims (3)

[Claims] 1. An ion-splitting means is provided in an ion flight path between a pulsed ion source and an ion detector, and an ion is provided between the ion source and the splitting means and between the splitting means and the ion detector. Arrangement of at least one fan-shaped electrostatic analyzer in the flight path so that the convergence condition for the flight time of ions is satisfied both from the ion source to the split point and from the split point to the ion detector. A multi-stage time-of-flight mass spectrometer characterized by: 2. A fan-shaped electrostatic analyzer control means for changing the analysis energy of a fan-shaped electrostatic analyzer disposed between the splitting means and the ion detector to repeatedly measure the time of flight, and
2. A multi-stage time-of-flight mass spectrometer according to claim 1, further comprising a storage means for storing measurement data relating to a flight time obtained from an ion detector in association with the analysis energy of the sector electrostatic analyzer. apparatus. 3. A plurality of means for splitting ions are provided in the flight path of the ions between the pulsed ion source and the ion detector, and between the ion source and the first splitting means, between the splitting means and the splitting means, and In the ion flight path between the last splitting means and the ion detector, the ion source is separated from the ion source and the splitting point, from one splitting point to the next splitting point, and from the splitting point to the ion detector. A multistage time-of-flight mass spectrometer characterized in that at least one fan-shaped electrostatic analyzer is arranged so that the convergence condition for the flight time is satisfied.