JP2004349139A - Ion trap mass spectrometer - Google Patents

Abstract

An ion trap mass spectrometer capable of easily setting parameter setting values is provided.
In an ion trap mass spectrometer, a display unit sets a parameter for displaying and setting at least a main RF voltage applied to a ring electrode and an auxiliary RF voltage applied to an end cap in a graph along a time axis. Screen and _az = -8eU /
A stable area display screen displaying a stable area of Mathieu represented by two axes of mr ₀ ² Ω ² and q _z = -4 eV / mr ₀ ² Ω ² is displayed, and the control unit performs mass analysis on the parameter setting screen. The resonance ions are calculated from the set values of the main RF voltage and the auxiliary RF voltage during the period of performing the above, and the line segment representing the calculated resonance ions is superimposed on the stable region display screen.
[Effect] The parameter can be set while easily confirming whether the parameter setting is optimally set in principle.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a mass spectrometer. In particular, it relates to control of a mass spectrometer using an ion trap technique and analysis parameter setting.
[0002]
[Prior art]
Ion trap mass spectrometers were introduced in the 1950's by Dr. It was invented by Paul, and since then many researchers and manufacturers have made various improvements on ion trap mass spectrometers. For example, a basic method of acquiring a mass spectrum is disclosed in Patent Document 1 below. Further, in Patent Documents 2 and 3 below, a method has been developed in which an auxiliary AC voltage (Supplementary AC voltage) is applied to detect ions by resonating them. It was also shown that the introduction of He gas at a pressure of about 1 mTorr (10 ⁻³ Torr) into the ion trap space significantly improved the resolution and sensitivity.
[0003]
The ion trap mass spectrometer in current use, it is possible to perform a variety of measurements such as MS / MS measurement and MS ⁿ measurements, accordingly, the specified mass range to accumulate in the ion trap, a particular mass range A large number of measurements, such as the designation of isolation for discharging ions with mass numbers other than those outside the ion trap electrode, the integration time and number of times, and the CID (Collision-induced dissociation) voltage during MS / MS. You need to set parameters.
[0004]
The most basic ion trap mass spectrometer is shown in FIG. 2 and a stabilizing envelope (so-called Mathieu stability curve) also shown in FIG. 2 of Patent Document 3, where _az = − (8 eU) / (mr ₀ ² ω ² ) and q _z = ( 4 eV) / (mr ₀ ² ω ² ). The inside of this line is a stable region, and the size of the ion trap electrode and the applied voltage determine these parameters, and determine whether or not ions are trapped in the ion trap space.
[0005]
[Patent Document 1]
US Patent No. 4,540,884 [Patent Document 2]
US Patent No. 4,736,101 [Patent Document 3]
JP-A-6-76790
[Problems to be solved by the invention]
In the current device, the setting method of these various parameters is performed by using a parameter prepared as a standard in the device in advance or by changing the numerical value of the parameter prepared in the standard by the user. .
[0007]
When a user sets a parameter, the setting is usually changed by directly inputting a numerical value of the parameter using a monitor and an input device (a keyboard, a pointing device, etc.) of a data processing device attached to the device. is there. However, it is difficult for the user to recognize whether or not the parameters are optimally set in principle only by inputting numerical values.
[0008]
Furthermore, when ions are mass-dispersed and emitted from the ion trap electrode, the voltage applied to the ion trap electrode is scanned. It was not easy to freely set the scanning conditions under the conditions intended by the company. In this case, the user has to change the scan condition program itself. Therefore, it is necessary to newly create a program with desired scanning conditions with a great deal of effort.
[0009]
Furthermore, even if a program for a new scan condition is set, there are restrictions on the power supply voltage on the apparatus and restrictions on the memory. Even when these restrictions are satisfied, ions to be measured are stored efficiently in a stable state and efficiently. It was not easy to study conditions for emission from the trap, that is, conditions that were optimal in principle (that is, conditions suitable for Mathieu's stability curve, etc.).
[0010]
In the above prior art, there is no means for confirming the principle optimum value for the parameter setting, and there is no function of generating a scan program for the parameter setting, and no consideration is given to the user freely changing the scanning method and parameters. There was a problem that hindered analysis due to a change in the scanning method.
[0011]
An object of the present invention is to provide an ion trap mass spectrometer capable of easily setting appropriate parameter setting values used for analysis.
[0012]
[Means for Solving the Problems]
A feature of the present invention for achieving the above object is that an ion trap portion having a ring electrode and a pair of end cap electrodes, and forming a trap space for trapping ions by applying a high-frequency voltage to the electrode, A detection unit for detecting ions discharged from the ion trap unit, a control unit for controlling the voltage applied to the ion trap, a detection result obtained by the detection unit, and a set value of the voltage applied to the ion trap unit In the ion trap mass spectrometer having a display unit for displaying, the display unit graphs and displays at least a main RF voltage applied to the ring electrode and an auxiliary RF voltage applied to the end cap along a time axis. a parameter setting screen for ^{_{setting, a z = -8eU / mr 0}} 2 Ω 2 and ^{_{q z = -4eV / mr 0 2}} Ω Mathieu represented by two axes of ² (where U = DC voltage, V = RF voltage, m = mass, e = charge, Ω = RF frequency, and r ₀ = rotational radius of the ion trap space). A stable area display screen for displaying the stable area of the parameter setting screen is displayed, and the control unit calculates resonance ions from the set values of the main RF voltage and the auxiliary RF voltage during a period in which the mass analysis of the parameter setting screen is performed. This is to superimpose a line segment representing the calculated resonance ion on the region display screen.
[0013]
With the above configuration, it is possible to set while easily confirming whether the parameter setting is optimally set in principle.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to FIGS.
[0015]
FIG. 3 is a schematic configuration diagram of an ion trap mass spectrometer to which the present invention is applied. The ion trap is composed of two end cap electrodes 3111 and 3112 arranged facing each other, and a ring electrode 301 arranged between the end cap electrodes. By applying a voltage to these electrodes, an ion trap space capable of accumulating ions in a space surrounded by the electrodes is formed. An RF voltage 111 is applied to the ring electrode 301 from an RF generator and an amplifier 303. Similarly, an AUX (auxiliary electric field) voltage 121 is applied to the end cap electrodes 3111 and 3112 from the auxiliary RF generator and the amplifier 313. The control of the RF generator / amplifier 303 and the auxiliary RF generator / amplifier 313 is performed by the control unit 330. By controlling the voltage applied to the ion trap, accumulation and discharge of ions are controlled.
[0016]
Ions introduced from the outside into the ion trap space or generated inside the ion trap space are accumulated in the ion trap space and then discharged from the ion trap space by controlling the voltage applied to each electrode. The ejected ions are emitted from the emission opening provided in the end cap electrode 3112 and detected by the detector 321. The detection signal is amplified by the pre-amplifier 322, taken into the control unit 330, subjected to data processing, and displayed on the monitor screen 331 as a detection result.
[0017]
FIG. 1 is an example of a scan setting screen displayed on the monitor screen 331 when mass spectrometry is performed by the present apparatus. It comprises a parameter setting screen 101 and a measurement signal display screen 102. The control section 330 performs all operations such as control of the display screen on the monitor screen 331 and recalculation of parameters based on an instruction input from an operator.
[0018]
Parameter setting screen 101 shows a setting example for the analysis of MS ^n, the RF voltage 111 and a DC voltage 112 which is applied to the ring electrode 301, AUX (auxiliary applied to the end cap electrodes 3111,3112 An electric field voltage 121 and a DC voltage 122 are set. The horizontal axis represents time, and the vertical axis represents voltage. On the parameter setting screen 101, an ion injection period (a period for introducing ions into the ion trap space) 114 and an isolation period (only necessary ions are trapped, 115), an activation period (period for performing MS / MS for cleaving trapped ions) 116, and a mass analysis period (period for performing mass spectrometry) 117. In each period, As shown in the figure, a voltage to be applied to the end cap electrode extending over the ring is set. In this display, the voltage values indicated by thick solid lines are parameters that can be arbitrarily set. More specifically, the setting value can be changed by moving a mouse cursor (not shown) to a solid line at a position to be changed with a pointing device such as a mouse, dragging the mouse cursor to an arbitrary position, and dropping it after moving to an arbitrary position.
[0019]
The RF voltage 111 and the DC voltage 112, and the AUX (auxiliary electric field) voltage 121 and the DC voltage 122 are arranged on the same screen and on the same time axis. As a result, setting errors can be prevented, and time timing can be easily and accurately set.
[0020]
Further, in this screen, a signal capture button 201 and a stable area display button 202 are arranged. For example, when changing the voltage setting value of the isolation period 115 of the RF voltage 111 as shown by a broken line 1151, when the user changes the setting line by dragging and dropping using a pointing device, and then presses the signal capture button 201. The changed voltage value is compared with a previously stored allowable voltage of the device. If the changed voltage is within the allowable voltage of the device, the changed setting line is registered as an analysis program and the analysis is executed. If the voltage after the change exceeds the allowable voltage of the device, as indicated by the error message 103 for the setting parameter, "The isolation voltage is too high. Set the voltage to XXV or less." Is displayed. Further, depending on the condition, a display such as "RF voltage is too high", "AUX voltage is too high", or "Positive / negative matching between RF voltage and AUX voltage" is not displayed.
[0021]
When the analysis is performed according to the conditions set on the parameter setting screen 101 and the ions are detected, they are displayed on the measurement signal display screen 102 in the order in which m / z (mass-to-charge ratio) is obtained. In the measurement signal display screen 102, the vertical axis represents the signal intensity and the horizontal axis represents the time. FIG. 1 shows an example in which spectra 1341, 1342, and 1343 are acquired. The time axes of the parameter setting screen 101 and the measurement signal display screen 102 are displayed so as to be the same.
[0022]
Note that the parameter setting screen 101 and the measurement signal display screen 102 may be displayed in independent windows instead of on the same screen, or the measurement data may be stored and displayed in parallel for each parameter change. Further, a function of enlarging or reducing the signal intensity axis and / or the time axis and displaying the measurement data may be provided. Further, a function of simultaneously storing measurement parameters for each measurement data may be provided. Further, a function may be provided for assigning a name to the parameter setting screen 101 for each setting parameter and storing the name. This makes it possible to easily use a desired parameter by calling it as a standard protocol and changing a part of the standard protocol.
[0023]
A case where the stable area display button 202 on the parameter setting screen 101 is pressed will be described.
[0024]
First, the ion stable region will be described.
[0025]
From Mathieu's equation, the behavior of ions is as follows.
[0026]
_{^{d 2 u / dξ 2 + (}} a u + 2q u cos2ξ) u = 0
u = x, y, z
ξ = Ωt / 2
_{^{x 2 + y 2 = r 0}} 2
_{a z = -2a x = -2a y} = -16eU / m (r 0 2 + 2z 0 2) Ω 2
_{q z = -2q x = -2q y} = -8eV / m (r 0 2 + 2z 0 2) Ω 2
z ₀ = r ₀ / √2 (for pure quadrapole)
_{a z = -2a x = -2a y} = -8eU / mr 0 2 Ω 2 ... (1)
_{q z = -2q x = -2q y} = -4eV / mr 0 2 Ω 2 ... (2)
Where U = DC voltage, V = RF voltage, m = mass, e = charge, Ω = RF frequency, r ₀ = radial radius of ion trap space,
_zo = axial radius of the ion trap space.
[0027]
As described above, the ion to be measured has a certain a value and a certain q value in accordance with Expressions 1 and 2. From these a and q values, it can be easily determined whether the ions are stably trapped or unstable in the trap. If both the a value and the q value are within the stable region of Mathieu, ions are stably captured. If either the a-value or the q-value, or both, are outside the stable region, the ions become unstable and disappear due to collision with the electrodes or ejection out of the trap.
[0028]
This will be described with reference to FIG. FIG. 4 is a stable area display screen 400 displayed after the stable area display button 202 is pressed, and the stable area of Mathieu is displayed. The horizontal axis is the _qz axis shown by the equation (2), and the vertical axis is the _az axis shown by the equation (1). The stable region 410 is a range surrounded by the above-mentioned stable region of r and the stable region of z. The line 411 of βr = 0, the line 412 of βz = 1, the line 413 of βr = 1, and the line of βz = 0 414.
[0029]
Here, in the mass analysis period 117 of FIG. 1, the resonance point from which ions are emitted changes depending on the relationship between the RF voltage 111 and the AUX (auxiliary electric field) voltage 121. Therefore, when the stable region display screen 400 is displayed, resonance emission in mass sweep is performed based on the RF voltage set value 1171, the DC voltage set value 128, the AUX voltage set value 127, and the DC voltage set value 129 during the mass analysis period 117. The points are automatically calculated and automatically displayed as a straight line of U / V = y (constant value) 430 in the stable region of FIG.
[0030]
When the operator designates an arbitrary point on the RF voltage set value 1171 by using a pointing device such as a mouse, the same ion position as the ion that is resonated and emitted at the designated point is linked, and the stable area display screen 400 is displayed. Also displayed above. For example, when a point 1191, a point 1192, and a point 1193 are specified on the RF voltage set value 1171, m / z = x1, m / z = x2, m / z = x3 (x1 <x2 <x3) at each point. ) Ions resonate. On the stable region display screen 400, when U / V = 0, points 420, 421, and 422 corresponding to the ions x1, x2, and x3 are displayed as resonance emission points. By performing such a display, it is possible to easily know which part of the mass analysis period 117 is within the stable region 410 and how many ions are stably trapped.
[0031]
When U / V = y (constant value) 430, the resonance emission points are point 4201, point 4211, and point 4221 as shown in the figure, respectively. 4221 is outside the stable region, and it can be seen that m / z = x1 and m / z = x2 are trapped, but m / z = x3 is not trapped. Therefore, when it is desired to trap all the ions of x1, x2, and x3, the user changes the value of the straight line of y of U / V = y (constant value) 430 by dragging and dropping using the mouse cursor. The slope of the U / V straight line may be changed arbitrarily so that all of the points 4201, 4211 and 4221 fall within the stable region.
[0032]
One end of the line y are the fixed point of a z _{= q} z _{= 0,} the straight line y can be changed so as to rotate about axis points a z _{= q} z ₌ 0. Thus, by changing the position of the straight line y, ions to be trapped can be easily set.
[0033]
On the other hand, in conjunction with U / V = y set in the stable area display screen 400 in FIG. 4, the RF voltage set value 1171, the DC voltage set value 128, and the AUX voltage set in the mass analysis period 117 shown in FIG. The voltage of the value 127 and the voltage of the DC voltage set value 129 are automatically changed. For example, when the voltage application pattern of the RF voltage set value 1171 is fixed, the voltage application pattern of the AUX voltage set value 127 is automatically changed. When the voltage application pattern of the AUX voltage set value 127 is fixed, the voltage application pattern of the RF voltage set value 1171 and the DC voltage set value 128 is automatically changed. When U / V = y (constant value) 430 in the stable region display screen 400 is set with U / V = 0, the DC voltage setting values 128 and 129 are set to the voltage value 0. A reference voltage selection box 450 is provided on the stable region display screen 400, and a voltage to be fixed is selected by checking either the RF voltage or the AUX voltage check box. By pressing the box of “recalculation”, the above-mentioned RF voltage set value 1171 or AUX voltage set value 127 is changed.
[0034]
Further, a mass number designation bar 1194 for designating a mass number within a certain range is provided next to the RF voltage set value 1171 in the mass analysis period 117, and the operator operates and designates the range of this bar by a pointing device. By doing so, the resonance emission point to be displayed on the stable area display screen 400 in FIG. 4 can be designated as a predetermined range instead of a point. In the stable region display screen 400, the resonance emission region 423 corresponds to the region designated by the mass number designation bar 1194.
[0035]
Further, the measurement signal display screen 102 is provided with a mass number confirmation bar 1195 displayed in association with the designated range of the mass number designation bar 1194 on the parameter setting screen 101. When the mass range of the mass number designation bar 1194 is changed, the mass number confirmation bar 1195 is also displayed so that the range (length in the horizontal direction) is changed in accordance with this range. By displaying the mass number confirmation bar 1195, it is possible to easily confirm which of the mass spectra obtained as a result of the detection is in the range designated by the mass number designation bar 1194. The correspondence between (m / z) and the time axis can be understood, which is convenient.
[0036]
As described above, by using the parameter setting screen 101 and the stable area display screen 400, parameters can be set while confirming trappable ions, and optimal parameters can be efficiently set and analyzed. It becomes.
[0037]
A second embodiment of the present invention will be described with reference to FIG. This example is an example in which the changed RF voltage set value 1171 is set on the parameter setting screen 101, and is not a straight line but a curve. Naturally, even a broken line that changes discontinuously can be set as long as it has an arbitrary time function. Therefore, as shown on the stable area display screen 400 in FIG. 4, a curve such as U / V = y (t) 431 is automatically calculated and displayed. As described above, by changing the shape of U / V = y (t) 431 by dragging with a pointing device such as a mouse or the like, it is automatically calculated, and the RF voltage set value 1171 on the parameter setting screen 101 and the DC voltage The voltage set values of the set value 128, the AUX voltage set value 127, and the DC voltage set value 129 can be changed.
[0038]
A third embodiment of the present invention will be described with reference to FIG.
[0039]
In the example of FIG. 5, the axis of the graph is a DC voltage (U) axis on the vertical axis and an RF voltage (V) axis on the horizontal axis.
[0040]
The aforementioned formula (1), (2) from ^{_{U = a x mr 0 2 Ω}} 2 / 8e = -a y mr 0 2 Ω 2 / 8e
^{_{V = q x mr 0 2 Ω}} 2 / 4e = -q y mr 0 2 Ω 2 / 4e
The stable region of ions corresponding to the mass numbers on the U axis and the V axis is displayed.
[0041]
In this example, it is assumed that the parameter setting is performed on the parameter setting screen 101 in FIG. 1 in the same manner as described above, and the stable area display screen 4001 in FIG. 5 is displayed by pressing the stable area display button 202. Incidentally, it may be used together with the stable area display screen 400 of FIG.
[0042]
In the case of FIG. 5, the size of the graphic in the stable region is different for each mass number. For example, when x1 <x2 <x3, the stable region 415 has a mass number m / z = x1, the stable region 416 has a mass number m / z = x2, and the stable region 417 has a mass number m / z = x3. Here, when U / V = 0, the resonance emission points are points 420, 421, and 422, respectively. In the case of a straight line of U / V = y (constant value) 430, the resonance emission points of mass numbers m / z = x1, m / z = x2, and m / z = x3 are points 4201, 4211, 4221, which indicates that the point 4221 is not trapped because it is outside the stable region. The relationship of the automatic change between the U / V straight line 430 on the stable area display screen 4001 and the voltage pattern of the AUX voltage set value 127 or the pattern of the RF voltage set value 1171 on the parameter setting screen 101 is the same as described above.
[0043]
This example is convenient not when examining the permeation of ions at the octapole but at the same time when examining the trapping of ions at the octapole, instead of the ion trap mass spectrometer.
[0044]
【The invention's effect】
According to the present invention, when performing a new scan, it is possible to set parameters such as an RF voltage while easily confirming whether or not parameters are optimally set in principle. Further, even when the setting is changed using the Mathieu stable area, the parameter can be fed back and changed, and the parameter setting can be easily changed.
[0045]
As described above, the operation efficiency in the parameter setting operation can be significantly reduced.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of a parameter setting screen and a signal display screen.
FIG. 2 is a diagram showing another example of a parameter setting screen and a signal display screen.
FIG. 3 is a schematic configuration diagram of an apparatus used in the present invention.
FIG. 4 is a diagram showing an example of a display screen of an ion stable region.
FIG. 5 is a diagram showing another example of a display screen of an ion stable region.
[Explanation of symbols]
101: Parameter setting screen, 102: Measurement signal display screen, 103: Error message, 111: RF voltage, 114: Injection period, 115: Isolation period, 116: Activation period, 117: Mass analysis period, 121 ... AUX (auxiliary electric field) voltage, 126, 127 AUX voltage set value, 131 measurement signal (mass spectrum), 201 signal acquisition button, 202 stable area display button, 301 ring electrode, 303 RF generator and amplifier, 313: auxiliary RF generator and amplifier, 321: detector, 322: preamplifier, 330: control unit, 331: monitor screen, 400, 4001: stable area display screen, 1171: RF voltage set value, 1194: mass number designation Bar, 3111, 3112 ... Endoki -Up electrode.

Claims (8)

An ion trap section having a ring electrode and a pair of end cap electrodes, forming a trap space for trapping ions by applying a high-frequency voltage to the electrodes, and a detection section for detecting ions discharged from the ion trap section A control unit for controlling the voltage applied to the ion trap, and a display unit for displaying a detection result obtained by the detection unit and a set value of the voltage applied to the ion trap unit. ,
The display unit is a parameter setting screen for displaying and setting at least the main RF voltage applied to the ring electrode and the auxiliary RF voltage applied to the end cap in a graph along a time axis, and _az = -8 eU / Mr ₀ ² Ω ² and q _z = -4 eV / mr ₀ ² Ω ² (where U = DC voltage, V = RF voltage, m = mass, e = charge, Ω = RF frequency, r ₀ = ion A stable area display screen that displays the Mathieu stable area represented by the two axes of the trap space is displayed.
The control unit calculates resonance ions from the set values of the main RF voltage and the auxiliary RF voltage during a period in which the mass analysis of the parameter setting screen is performed, and the calculated resonance ions are displayed on the stable region display screen. An ion trap mass spectrometer characterized by superimposing and displaying line segments. In claim 1,
The parameter setting screen includes a period for introducing ions into the ion trap space, a period for trapping only necessary ions and eliminating unnecessary ions, a period for performing MS / MS for cleaving trapped ions, and a mass analysis. The ion trap mass spectrometer is characterized in that the operation is divided into periods in which the main RF voltage and the auxiliary RF voltage are set and changed in each period. In claim 1,
When an arbitrary point on the graph during the period of performing the mass analysis of the main RF voltage is specified, a resonance ion corresponding to the specified point is calculated, and the calculated ion is calculated on the line segment of the stable region display screen. An ion trap mass spectrometer, which displays points corresponding to the resonance ions. The line segment of one end of the stable region display screen according to claim 1 is connected to the intersection of a _z-axis and q _z-axis, the line segment position can be changed to the intersection point as a fixed point, is the segment position When changed, the control unit changes the set value of the main RF voltage or the auxiliary RF voltage during a period in which the mass analysis of the parameter setting screen is performed according to the position of the changed line segment. Trap mass spectrometer. In claim 4,
The stable area display screen displays a designated area for designating whether to change the main RF voltage or the auxiliary RF voltage when recalculating after changing the position of the line segment. apparatus. In claim 1,
The ion trap mass spectrometer, wherein the display unit displays a measurement display screen displaying a mass spectrum detected by the detection unit, and the measurement display screen is displayed on the same time as the parameter setting screen. . In claim 6,
On the graph for setting the main RF voltage of the parameter setting screen, having a mass number designation bar to specify the range to reflect the resonance ions in the period of performing the mass analysis on the stable region display screen,
The measurement display screen displays a mass number confirmation bar indicating a designated range of the mass number designation bar on a mass spectrum. In claim 1,
The control unit stores a threshold for a set value of each parameter set on the parameter setting screen, and at the time of parameter setting, calculates whether a set value set on the parameter setting screen is within the threshold, and as a result Is displayed on the display unit.

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