CN117672802A - Mass spectrometry method based on time-of-flight technology - Google Patents
Mass spectrometry method based on time-of-flight technology Download PDFInfo
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- 238000002366 time-of-flight method Methods 0.000 claims description 7
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- 238000012935 Averaging Methods 0.000 description 1
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Abstract
The invention provides a mass spectrometry method based on a time-of-flight technology, which comprises the following steps: (S1) applying a pulsed signal to the modulated region repulsion, the time-of-flight mass spectrometer operating without ion entry, the detector outputting a first signal comprising an interference caused by said pulsed signal; (S2) inverting the first signal to obtain a second signal and storing the second signal; (S3) ions entering the time-of-flight mass spectrometer, the pulse signal being applied to a modulation region repulsive force, the detector outputting a third signal; (S4) the analysis unit sums the second signal and the third signal to obtain a fourth signal; (S5) the analysis unit processes the fourth signal, thereby obtaining the analyte information. The invention has the advantages of low detection limit, high sensitivity and the like.
Description
Technical Field
The invention relates to a mass spectrometry technology, in particular to a mass spectrometry analysis method based on a time-of-flight technology.
Background
The ICP-TOF time-of-flight mass spectrometer distinguishes different ions according to their different masses and different flight times. A pulsed voltage signal is required in the TOF modulation region to repel ions into the acceleration region. The pulse voltage signal requires a small rising edge, the amplitude is at a voltage level of hundreds of volts at a level of tens of ns, strong electromagnetic wave radiation can be formed outside at the moment, and obvious pulse signal interference can be generated on an ion detection signal.
In the full spectrum test, the signal with low quality number is tested to have extremely large interference, and the signal intensity is obviously identified from the interference when the sample concentration is high, so that the detection limit of the signal is extremely high, and the instrument is not beneficial to the application of micro sample analysis. Because the principle and structure of the instrument limit that the pulse interference cannot be completely eliminated by shielding, the signal detection is always provided with a pulse radiation interference signal.
In addition, the time-of-flight mass spectrometer resolution is defined as r=t/(2Δt), where T is the total time of flight of the ions and Δt is the mass spectral peak half-peak width. It can be seen that the way to improve the resolution of the mass spectrum is only two ways, namely the extension of the total flight time of the ions and the shortening of the half-peak width of the mass spectrum. The half-peak width of the mass spectrum is affected by the initial spatial dispersion, the initial energy dispersion and the return time, which is very difficult to reduce, and is also a main reason for limiting the resolution of the time-of-flight mass spectrometer.
The prior art solving method comprises the following steps: the length of the field-free region is prolonged to prolong the total flight time of ions, so that the resolution is improved, the resolution is tens of thousands of mass spectrometers, the length of the field-free region is required to be several meters, and the experimental environment is required to be very high.
Disclosure of Invention
To address the deficiencies in the prior art described above, the present invention provides a time-of-flight mass spectrometer.
The invention aims at realizing the following technical scheme:
a mass spectrometry method based on a time-of-flight technique, the mass spectrometry method comprising the steps of:
(S1) applying a pulsed signal to the modulated region repulsion, the time-of-flight mass spectrometer operating without ion entry, the detector outputting a first signal comprising an interference caused by said pulsed signal;
(S2) inverting the first signal to obtain a second signal and storing the second signal;
(S3) ions entering the time-of-flight mass spectrometer, the pulse signal being applied to a modulation region repulsive force, the detector outputting a third signal;
(S4) the analysis unit sums the second signal and the third signal to obtain a fourth signal;
(S5) the analysis unit processes the fourth signal, thereby obtaining the analyte information.
Compared with the prior art, the invention has the following beneficial effects:
1. the detection limit is low, and the sensitivity is high;
deducting the interference in the ion signal reduces the detection limit of the mass spectrometer, so that the detection of the full spectrum mass number element can be carried out,
after interference elimination, the pulse frequency can be improved, the number of spectrograms generated per second is increased, and the sensitivity of the mass spectrometer is improved;
2. the resolution is high;
the control electrode is arranged, and the voltage on the electrode of the acceleration region is regulated, so that the acceleration region is converted between acceleration and reflection functions as required, and meanwhile, the control electrode provides electric field force for ions in the field-free region to offset the ions and prevent the ions from escaping, so that the ions are reflected back and forth between the acceleration region and the reflection region, the total flight time is improved, and the resolution is improved as required;
3. the volume is small;
in view of the fact that ions are reflected back and forth between the acceleration region and the reflection region, the flight time is improved by repeatedly passing through the field-free region, the volume is obviously reduced by the folded design, and the length of the field-free region is reduced to 30cm of the patent from a few meters in the prior art.
Drawings
The present disclosure will become more readily understood with reference to the accompanying drawings. As will be readily appreciated by those skilled in the art: the drawings are only for illustrating the technical scheme of the present invention and are not intended to limit the scope of the present invention. In the figure:
FIG. 1 is a flow diagram of a method of mass spectrometry based on time-of-flight techniques according to an embodiment of the invention;
fig. 2 is a schematic diagram of a time-of-flight mass spectrometer according to an embodiment of the invention.
Detailed Description
Figures 1-2 and the following description depict alternative embodiments of the invention to teach those skilled in the art how to make and reproduce the invention. In order to teach the technical solution of the present invention, some conventional aspects have been simplified or omitted. Those skilled in the art will appreciate variations or alternatives derived from these specific embodiments that fall within the scope of the invention. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple variations of the invention. Thus, the invention is not limited to the following alternative embodiments, but only by the claims and their equivalents.
Example 1
According to the mass spectrometry method based on the time-of-flight technology, as shown in fig. 1, the mass spectrometry method comprises the following steps:
(S1) applying a pulsed signal to the modulated region repulsion, the time-of-flight mass spectrometer operating without ion entry, the detector outputting a first signal comprising an interference caused by said pulsed signal;
(S2) inverting the first signal to obtain a second signal and storing the second signal;
(S3) ions entering the time-of-flight mass spectrometer, the pulse signal being applied to a modulation region repulsive force, the detector outputting a third signal;
(S4) the analysis unit sums the second signal and the third signal to obtain a fourth signal;
(S5) the analysis unit processes the fourth signal, thereby obtaining the analyte information.
In order to improve the accuracy of the interference subtraction, further, in step (S1), a first signal of a plurality of periods is obtained and averaged.
In order to improve the accuracy of the interference subtraction, further, in step (S1) and step (S3), the operating parameters of the time-of-flight mass spectrometer are the same.
To increase the time of flight of ions to increase resolution, further, as shown in fig. 2, ions enter the acceleration region 20, the field free region 60, the reflection region 30, and the field free region 50 in this order from the modulation region 10, which is a prior art in the art;
adjusting the voltage on the electrodes in the acceleration region 20 so that ions entering the acceleration region 20 from the field-free region 60 are reflected, and then enter the field-free region 60 and the reflection region 30;
ions are reflected back and forth between the acceleration region 20 and the reflection region 30 while the ions in the field free region 60 are deflected by the application of an electric field force, preventing the ions from escaping the field free region 60;
when the number of back and forth reflections reaches the requirement, the voltage of the electrodes in the acceleration region 20 is adjusted, and the ions pass through the acceleration region 20 and are received by the detector 40.
In order to switch the acceleration region 20 between ion acceleration and ion reflection, further, the acceleration region 20 includes a plurality of electrodes arranged in sequence, when a positive voltage is applied to the electrode 21 nearest to the modulation region 10 by the power supply, and a negative voltage is applied to the other electrodes, ions entering the acceleration region 20 are reflected;
when the power supply applies a positive voltage to the electrode 21 nearest to the modulation region 10 and a negative voltage to the other electrodes, ions entering the acceleration region 20 are accelerated.
To obtain a precise time of flight, further, the total time of flight T of the ions is:
，/>，/>，/>；
m/q is the mass-to-charge ratio of the ion and z is the distance from the initial ion position to the electrode 11 of the modulation region 10 in the vicinity of the acceleration region 20Separation, d 2 Is the maximum distance between the electrodes in the acceleration zone 20, E 1 、E 2 、E 3 、E 4 The electric field intensities of the modulation region 10, the acceleration region 20 at the time of ion acceleration, the reflection region 30, and the acceleration region 20 at the time of ion reflection, respectively, and N is the number of times ions pass through the field-free region.
To ensure that ions do not escape from the field-free region and are able to reflect back and forth between the acceleration region 20 and the reflection region 30 multiple times, further, the ions within the field-free region 60 are offset in such a way that:
the control electrodes 50 are positioned at two sides of the field-free region 60, and ions in the field-free region 60 are pushed to deviate by the electric field force between the control electrodes 50;
the voltage on the control electrode 50 is adjusted so that a forward or reverse electric field force is applied to ions within the field free region 60.
Example 2
Application example of the mass spectrometry method based on the time-of-flight technique according to embodiment 1 of the present invention.
In this application example, as shown in fig. 2, in the time-of-flight mass spectrometer that operates the intrinsic spectrum analysis method, the modulation region 10, the acceleration region 20, the field-free region 60, and the reflection region 30 are disposed in this order in the vertical direction. The accelerator region 20 comprises a plurality of electrodes arranged in parallel, such as (uppermost) electrode 21 nearest the modulator region, (lowermost) electrode 22 nearest the reflector region, and a first set of electrodes 23 in between. In the reflective area 30, an uppermost electrode 31, a lowermost electrode 32, and a second set of electrodes 33 in between are included. A field free region is between electrode 22 and electrode 31.
The control electrode 50 is respectively positioned at the left side and the right side of the field-free region 60, and a power supply applies a voltage to the control electrode 50 to apply an electric field force in the horizontal direction to the ions in the field-free region 60, so that the ions are offset towards the center of the field-free region 60, and the ions are prevented from escaping the field-free region.
The power supply receives the instruction of the controller, applies a positive voltage to the electrode 21, and applies a negative voltage to other electrodes in the acceleration region 20, and the acceleration region 20 has an ion reflection function at the moment; when the electrode 21 is grounded and the other electrodes are negative voltages, the acceleration region has an ion acceleration function. The power supply applies a negative voltage to electrode 31 of reflective region 30, which is the same voltage as electrode 22, and positive voltage to electrode 32, and field-free region 60 is formed between electrode 22 and electrode 31. The power supply applies a voltage to the control electrode 50 such that the electric field force is switched between horizontal right (forward) and horizontal left (reverse).
According to the mass spectrometry method based on the time-of-flight technology, as shown in fig. 1, the mass spectrometry method comprises the following steps:
(S1) applying a pulsed signal to the modulated region repulsion, the time-of-flight mass spectrometer operating without ion entry, the detector outputting a first signal comprising an interference caused by said pulsed signal;
obtaining a first signal of a plurality of periods and averaging;
the first signal is obtained in the same manner as in step (S3), except that no ions enter the time-of-flight mass spectrometer in this step.
(S2) inverting the averaged first signal to obtain a second signal and storing the second signal;
(S3) ions enter the time-of-flight mass spectrometer, the pulse signal is applied to the repulsive pole of the modulation area, and the detector outputs a third signal in the specific way that:
ions enter acceleration region 20, field free region 60, reflection region 30, and said field free region 50 in that order from modulation region 10, as is known in the art;
the power supply is controlled by the instruction of the controller(time zero is the downward movement of ions from the modulation zone) the voltage on the electrode 21 in the acceleration zone 20 is adjusted: the ground becomes a positive voltage so that ions entering the acceleration region 20 from the field-free region 60 are reflected, and then enter the field-free region 60 and the reflection region 30;
ions are reflected back and forth between the acceleration region 20 and the reflection region 30 while the ions within the field-free region 60 are subjected to an electric field force(time zero point)Is the downward movement of ions from the modulation region), initially an electric field force horizontally to the left, and then every +.>The horizontal electric field is switched once to the left and right directions, and ions in the field-free region are deflected: when the ions move to the right side of the field-free region 60, a horizontal leftward electric field force is applied, and when the ions move to the left side of the field-free region 60, a horizontal rightward electric field force is applied, so that the ions are prevented from escaping the field-free region 60, and the ions are ensured to be reflected back and forth between the acceleration region 20 and the reflection region 30 and pass through the field-free region 60 for a plurality of times;
when the number of back and forth reflections reaches the requirement, the voltage of the electrode in the acceleration region 20 is adjusted, ions pass through the acceleration region 20 and are received by the detector 40, and the detector 40 outputs a third signal; the total time of flight T of the ions is:
，/>，/>，/>；
m/q is the mass-to-charge ratio of the ion, z is the distance from the initial ion position to the electrode 11 of the modulation region 10 in the region 20 of the acceleration region, d 2 Is the maximum distance between the electrodes in the acceleration zone 20, E 1 、E 2 、E 3 、E 4 The electric field intensities of the modulation region 10, the acceleration region 20 at the time of ion acceleration, the reflection region 30, and the acceleration region 20 at the time of ion reflection, respectively, and N is the number of times ions pass through the field-free region.
The parameters of this embodiment are:
z=7.5mm、d 2 =120mm，L=300mm，E 1 =5000V/M，E 2 =33333V/M，E 3 =-66666 V/M，E 4 =66666 V/M。
taking the mass number 159 as an example, when Δt is 0.05 μs, ions are flown directly into the detector without controlling the electric field of the acceleration region according to the prior art, and the resolution is 259.5.
According to the present patent solution, the accelerating area electric field is controlled, the electric field force initially horizontally leftwards is started at t=14.6 μs, then the horizontal electric field left and right directions are switched once every Δt=19.58 μs, the accelerating area 20 plays a role of reflecting as required, at this time, the voltage on the electrode 21 is 4000V, N is equal to 42, the total flight time t= 223.415 μs, and the resolution= 4468.3. When N is 202, the resolution is= 22928.3, and it can be seen that with the scheme of this patent, a small-sized high-resolution time-of-flight mass spectrometer is realized.
(S4) the analysis unit sums the second signal and the third signal to obtain a fourth signal, thereby subtracting the interference due to the pulse signal;
(S5) the analysis unit processes the fourth signal, thereby obtaining the analyte information.
Claims (8)
1. A mass spectrometry method based on a time-of-flight technique, the mass spectrometry method comprising the steps of:
(S1) applying a pulsed signal to the modulated region repulsion, the time-of-flight mass spectrometer operating without ion entry, the detector outputting a first signal comprising an interference caused by said pulsed signal;
(S2) inverting the first signal to obtain a second signal and storing the second signal;
(S3) ions entering the time-of-flight mass spectrometer, the pulse signal being applied to a modulation region repulsive force, the detector outputting a third signal;
(S4) the analysis unit sums the second signal and the third signal to obtain a fourth signal;
(S5) the analysis unit processes the fourth signal, thereby obtaining the analyte information.
2. The method of time-of-flight based mass spectrometry according to claim 1, wherein in step (S1), a plurality of cycles of the first signal are obtained and averaged.
3. The method of claim 1, wherein the time-of-flight based mass spectrometry,
in step (S1) and step (S3), the operating parameters of the time-of-flight mass spectrometer are the same.
4. A method of mass spectrometry based on time of flight techniques as claimed in claim 3,
in the step (S3), ions sequentially enter an acceleration region, a field-free region, a reflection region and the field-free region from a modulation region;
adjusting the voltage on the electrode in the accelerating region so that ions entering the accelerating region from the field-free region are reflected and then enter the field-free region and the reflecting region;
ions are reflected back and forth between the accelerating region and the reflecting region, and meanwhile, the ions in the field-free region are offset by applying electric field force, so that the ions are prevented from escaping the field-free region;
when the number of back and forth reflections reaches the requirement, the voltage of the electrode in the acceleration region is adjusted, and ions pass through the acceleration region and are received by the detector.
5. The method according to claim 4, wherein the acceleration region includes a plurality of electrodes arranged in sequence, and ions entering the acceleration region are reflected when a positive voltage is applied to an electrode nearest to the modulation region and a negative voltage is applied to other electrodes;
and when a positive voltage is applied to the electrode nearest to the modulation area and a negative voltage is applied to other electrodes, ions entering the acceleration area are accelerated.
6. The method of claim 4, wherein the total time of flight T of the ions is:
，/>，/>，/>；
m/q is the mass-to-charge ratio of the ion, z is the distance from the initial ion position to the electrode of the modulation region in the adjacent acceleration region, d 2 Is the maximum distance between the electrodes in the acceleration zone, E 1 、E 2 、E 3 、E 4 The electric field intensities of the modulation region, the acceleration region during ion acceleration, the reflection region and the acceleration region during ion reflection are respectively, and N is the number of times that ions pass through the field-free region.
7. The method of claim 5, wherein the ion drift in the field-free region is as follows:
the control electrodes are positioned at two sides of the field-free region, and ions in the field-free region are pushed to deviate by the electric field force between the control electrodes;
and adjusting the voltage on the control electrode so that the direction of the electric field force changes.
8. The method of claim 7, wherein the time-of-flight based mass spectrometry,
when (when)At the same time, a positive voltage is applied to the electrode nearest to the modulation region in the acceleration region, and then every +.>The voltage on the control electrode is adjusted so that the direction of the electric field force changes by 180 degrees.
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