CN210897195U - Ion signal detection device for ion trap mass spectrometer - Google Patents
Ion signal detection device for ion trap mass spectrometer Download PDFInfo
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- CN210897195U CN210897195U CN201922434347.8U CN201922434347U CN210897195U CN 210897195 U CN210897195 U CN 210897195U CN 201922434347 U CN201922434347 U CN 201922434347U CN 210897195 U CN210897195 U CN 210897195U
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Abstract
The utility model discloses an ion signal detection device for ion trap mass spectrograph. The device of the utility model comprises an ion trap mass analyzer, an electrode group and a current or voltage measuring device; the electrode group is arranged on one side of an ion extraction electrode, which is far away from an ion storage area, in the ion trap mass analyzer, and consists of more than 2 electrodes which are mutually electrically insulated, and except the electrode which is farthest from the ion extraction electrode, other electrodes are correspondingly provided with small holes for the passing of ions separated from the ion trap analyzer; wherein: when the electrode group is 2 electrodes, the current or voltage measuring device is directly connected with the 2 electrodes; when the electrode group is more than 3 electrodes, the working power supply is connected with the 2 electrodes nearest to the ion extraction electrode, and the current or voltage measuring device is connected with the 2 electrodes farthest. The device of the utility model is simple in structure, it is with low costs, can realize the high sensitivity test of ion mass spectrum signal.
Description
Technical Field
The utility model relates to a mass spectrometry instrument technical field, concretely relates to an ion signal detection device for ion trap mass spectrograph.
Background
An ion trap mass spectrometer is a most commonly used mass spectrometer, has the functions of ion storage, mass analysis and tandem mass spectrometry, can quickly analyze the chemical composition and molecular structure of a substance, and is a common scientific instrument in scientific research and practical application. And is the first choice for the miniaturization of mass spectrometry at present. The method is widely applied to the fields of life science, environmental monitoring, food safety, public safety and the like. The basic principle of an ion trap mass analyser is: the proper electrode and power supply are utilized to generate proper electric field distribution in a certain space, wherein the electric field distribution is mainly composed of quadrupole electric field components and is assisted by electric fields of other components. When sample ions generated by various ion sources are introduced into an ion storage region of the ion trap, the ions are bound in the ion storage region under the action of an electric field, and the ions stored in the ion trap can be subjected to mass selective excitation by utilizing the change of the electric field through changing the voltage loaded on the electrodes of the ion trap, and are sequentially extracted from the ion trap according to different mass-to-charge ratios of the ions. The extraction of ions from the ion trap is typically achieved by machining an ion aperture in an ion trap electrode, so that mass selectively excited ions can escape from the aperture. If an ion detector is mounted outside the ion flood aperture, i.e. on the side remote from the ion storage region, it can detect and record the ion signal, i.e. the mass spectral signal of the sample ions.
The most commonly used ion detector in ion trap mass spectrometry instruments is the so-called channel electron multiplier (fig. 1). It is constructed of materials with high secondary electron emission capability. In use, a high voltage operating power supply is applied between the two ends of the channel electron multiplier, thereby forming an electric field within it. When ions separated by the ion trap mass analyser collide under the influence of an electric field towards the surface of the channel electron multiplier, a plurality of secondary electrons will be generated. These secondary electrons will be accelerated and hit the surface of the multiplier at high speed under the action of the electric field generated by the operating voltage, generating more secondary electrons. This is repeated, and the electrons are accelerated again and again in the multiplier, producing more and more secondary electrons. Finally, all secondary electrons pass through the final electron exit of the electron multiplier and are collected by electrodes arranged behind the electron multiplier, obtaining current signals corresponding to the incident ions, which can also be converted into voltage signals, eventually becoming mass spectra signals.
Electron multipliers are one of the essential components of current ion trap mass spectrometry, as well as other types of mass analyzers, such as quadrupole mass analyzers and the like, and more complex mass spectrometry systems, including time-of-flight mass analyzers, which are responsible for the tasks of mass spectrometers to record ion signals and obtain mass spectra.
Suppose the electron multiplication factor of one channel electron multiplier is 107Multiple multiplication, i.e. the number of secondary electrons generated by an ion gives a total number of 10 electrons7The final measured electron charge is then:
1.6×10-19×107＝1.6×10-12coulombs.
If 1000 ions of the same mass to charge ratio enter the ion detector per second, the resulting electron charge should theoretically be:
1000×1.6×10-19×107＝1.6×10-9coulombs.
1.6×10-9Coulomb 1 s 1.6 × 10-9Ampere is
If this current signal is converted into a voltage signal, assuming that the resistance used is 1000000 ohms, the voltage that can be measured is: v1000000 1.6 10-9＝1.6*10-3In volts.
The channel electron multipliers used at present mainly have several major problems:
(1) all electron multipliers are aged due to aging of materials, and the consequence is that the electron multiplication efficiency is poorer and poorer, so that the obtained mass spectrum signals are weaker and weaker; therefore, all electron multipliers have a certain service life;
(2) different electron multiplier manufacturers, electron multipliers manufactured in different batches may have different final electron multiplication efficiencies due to different used materials or processes, and thus when used as a signal for detecting ions, may cause mass spectrum signals with equal ion content to have different magnitudes;
(3) theoretically, the total amount of secondary electrons generated by N ions should be equal to N times of that of one ion, but the secondary electron emission capability of all materials is limited, for example, a large number of electrons collide with the surface of a very small area of an electron multiplier in a very short time, the number of generated secondary electrons is difficult to be a simple multiple of that of the secondary electrons generated by one electron, so that the so-called signal saturation phenomenon of the ions is caused, and the quantitative analysis result is inaccurate.
(4) The electron multiplier also often has a mass discrimination effect, that is, one ion with a large mass-to-charge ratio and a large volume is small compared with one ion with a small mass-to-charge ratio, and the number of secondary electrons generated by the small ion is different, which finally causes the difference in the intensity of mass spectrum signals generated by the same number of large ions and small ions, resulting in the inaccuracy of the quantitative analysis result.
(5) The microchannel plate electron multiplier is a consumable product of the device in a flight time mass spectrum vacuum chamber, and is expensive and inconvenient to replace.
SUMMERY OF THE UTILITY MODEL
In order to solve the defects existing in the prior ion detection technology, the utility model provides a novel ion detection device and a method. The device of the utility model is simple in structure, it is with low costs, can realize the high sensitivity test of ion mass spectrum signal.
The utility model discloses set up several electrodes at ion trap mass analyzer's ion leading-out end, the high-speed motion of ion between the electrode that will be separated by ion trap mass analyzer obtains ion mass spectrum signal through measuring the produced electric current of ion motion between two electrodes. The basic process is as follows:
assuming that ions separated by the ion trap mass analyser are accelerated to 2000eV, the time taken for the ions to pass at high velocity through the two ion current sensing electrodesIs 10-7Second (i.e., 0.1 microseconds), the current generated is:
if 1000 ions of the same mass-to-charge ratio pass between the two electrodes at the same time, the resulting electron current should theoretically be:
further, if this current is converted into a voltage, it is assumed that the resistance used is 106Ohm, then the voltage that can be measured is: v106×1.6×10-9＝1.6×10-3In volts.
The technical scheme of the utility model specifically introduces as follows.
An ion signal detection arrangement for an ion trap mass spectrometer, comprising an ion trap mass analyser, an electrode set, and a current or voltage measuring means; the electrode group is arranged on one side of an ion extraction electrode, which is far away from an ion storage area, in the ion trap mass analyzer, and consists of more than 2 electrodes which are mutually electrically insulated, and except the electrode which is farthest from the ion extraction electrode, other electrodes are correspondingly provided with small holes for the passing of ions separated from the ion trap analyzer; wherein: when the electrode group is 2 electrodes, the current or voltage measuring device is directly connected with the 2 electrodes; when the electrode group is more than 3 electrodes, the working power supply is connected with the 2 electrodes nearest to the ion extraction electrode, and the current or voltage measuring device is connected with the 2 electrodes farthest.
In the present invention, the electrodes in the electrode group are made of conductive material, and the shape thereof may be planar, curved, or any other shape.
In the present invention, the ion trap mass analyzer is a three-dimensional ion trap, a linear ion trap or a combination thereof with other types of mass analyzers.
Compare in traditional ion detection device, the utility model has the advantages of:
(1) because the ion detector is not used, the problems of aging and damage of the detector and the problem of service life of the ion detector are avoided;
(2) because the current signal generated by the ion movement is measured, the problem that the multiplication efficiency of ions with different sizes is not equal is avoided;
(3) theoretically, the current generated by N ions is strictly equal to N times of the current generated by one ion, so that the phenomenon of signal saturation is avoided, and the mass discrimination effect is avoided, namely the mass spectrum signal intensity generated by the same number of large ions and small ions is completely the same, and the quantitative analysis result is accurate.
(4) Because the ion detector is not used, the maintenance and replacement of the ion detector do not exist, and the expenditure is saved.
Drawings
Fig. 1 is a structural diagram of an electron multiplier.
Fig. 2 is a schematic cross-sectional view of a conventional three-dimensional ion trap mass analyzer.
Fig. 3 is a schematic diagram of a three-dimensional ion trap mass analyzer-ion signal detection system instrumentation system constructed in accordance with the teachings of the present invention.
Fig. 4 is a schematic diagram of a linear ion trap mass analyzer-ion signal detection system instrumentation system constructed in accordance with the teachings of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings, which are not intended to limit the present invention.
Figure 2 is a schematic diagram of a three-dimensional ion trap mass analyzer. It is composed of three electrodes with hyperboloid cross sections, a ring electrode 11 and two end electrodes 12 and 13 which are surrounded together. In fig. 2, 11, 12 and 13 are fixed together in a manner to form a three-dimensional ion trap in which end electrode 12 has an ion introduction aperture 121 which allows an ion beam 10 generated by the ion source to enter the ion trap for storage, mass analysis, etc. The terminal electrode 13 is formed with a small hole 14 for ion escape. In practical applications, a radio frequency power RF is applied to the ring electrode 11, and the terminal electrode 12 and the terminal electrode 13 are connected together and applied with another working power. The terminal electrodes 12 and 13 are also often loaded with another dipole electrode, also referred to as an ion excitation voltage, which functions to excite and drive ions out of the ion trap and out of the aperture 14.
The ion trap electrode system generates electric field distribution mainly based on a quadrupole electric field under the action of a radio frequency power supply RF, and ions with different mass-to-charge ratios are bound in the ion trap by the electric field when entering an ion storage area defined by the ion trap electrodes. When the dipole voltages on the end electrodes 12 and 13 are changed, some ions will be resonantly excited, i.e., ions having a particular mass-to-charge ratio will be resonantly excited and escape from the aperture 14. Eventually reaching the ion detector 15 disposed outside the end electrode 13, i.e., on the side away from the ion storage region. If the voltage value of the dipole excitation voltage is continuously changed, ions with different mass-to-charge ratios are ejected and detected one by one, and finally, a mass spectrogram of the analyzed sample is formed.
Fig. 3 is a schematic diagram of a three-dimensional ion trap mass analyzer-ion signal detection system instrumentation system constructed in accordance with the teachings of the present invention. In fig. 3, it is composed of three electrodes with hyperboloid cross-section, a ring electrode 21, two end electrodes 22 and 23 surrounding together, the ring electrode 21, the end electrodes 22 and 23 are fixed together in a certain way to form a three-dimensional ion trap, wherein the end electrode 22 has an ion introduction aperture 221, which allows the ion beam 20 generated by the ion source to enter the ion trap for storage, mass analysis, etc. The terminal electrode 23 is formed with a small hole 24 for allowing ions to escape. In practice, ring electrode 21 is supplied with a radio frequency power RF, and end electrodes 22 and 23 are connected together and supplied with another operating power. The end electrodes 22 and 23 are also often loaded with another dipole electrode, also referred to as an ion excitation voltage, which functions to excite and drive ions out of the ion trap and out of the aperture 24.
The ring electrode 21 and the end electrodes 22 and 23 generate electric field distribution mainly based on a quadrupole electric field under the action of the radio frequency power supply RF, and ions with different mass-to-charge ratios are bound in the ion trap by the electric field when entering an ion storage region defined by the ion trap electrodes. When the dipole voltages on the terminal electrodes 22 and 23 are changed, some ions will be resonantly excited, i.e., ions having a particular mass-to-charge ratio will be resonantly excited and escape from the aperture 24. Eventually reaching the side disposed outside the terminal electrode 23, i.e., away from the ion storage region. If the voltage value of the dipole excitation voltage is continuously changed, ions with different mass-to-charge ratios are ejected and detected one by one, and finally, a mass spectrogram of the analyzed sample is formed.
Different from the ion signal detection mode commonly used at present: the ion trap mass spectrometry system does not require the use of an electron multiplier to detect the ion signal, but rather performs the ion signal measurement in such a way that, as the ion beam mass analyzed by the ion trap passes through 24, it will be accelerated by the voltage applied between electrodes 25 and 26, and the accelerated ions will rapidly pass through the space between electrodes 26 and 27. Between the electrodes 26 and 27 there will be provided means for measuring the associated current signal, i.e. the mass spectral signal of the ions, generated by the rapid movement of the ions. The size of which can be derived from previous analyses.
Obviously, in the ion trap mass spectrum provided by the utility model, an electron multiplier is not needed for ion signal detection.
Fig. 4 is a schematic structural diagram of an instrument system of the constructed linear ion trap mass analyzer-ion signal detection system. In fig. 4, the quadrupole ion guide 31 is formed by surrounding four electrodes having a hyperboloid or cylindrical cross section. The ion trap mass analyser 32 is also formed by four electrodes of hyperboloid or cylindrical cross-section surrounding together. One of the ion trap electrodes in the quadrupole ion guide 31 has an ion introduction aperture 39. The ion beam generated by the ion source 30 enters the quadrupole ion guide from aperture 34 in electrode 35, is focused and transported, and passes through aperture 36 in electrode 37 into the ion trap mass analyser 32 for storage and mass analysis.
The ion trap mass analyser 32 will generate an electric field distribution dominated by a quadrupole electric field under the action of the radio frequency power supply RF, and when ions of different mass to charge ratios enter an ion storage region defined by the ion trap electrodes, they will be bound in the ion trap by the electric field. When the dipole voltage on the pair of electrodes of the ion trap is changed, some ions will be resonantly excited, i.e. ions having a particular mass to charge ratio will be resonantly excited and escape from the aperture 39. Eventually reaching the side disposed outside of the ion trap, i.e., away from the ion storage region. If the voltage value of the dipole excitation voltage is continuously changed, ions with different mass-to-charge ratios are ejected and detected one by one, and finally, a mass spectrogram of the analyzed sample is formed.
Different from the ion signal detection mode commonly used at present: the ion trap mass spectrometry system does not require the use of an electron multiplier to detect the ion signal, but rather performs the ion signal measurement in such a manner that, after the ion beam mass-analyzed by the ion trap passes through the aperture 39, it is accelerated by a voltage applied between the electrode 41 and the electrode 42, and the accelerated ions rapidly pass through the space between the electrodes 42 and 43. Between the electrodes 42 and 43 there will be provided means for measuring the associated current signal, i.e. the mass spectral signal of the ions, resulting from the rapid movement of the ions. The size of which can be obtained from previous analyses.
Obviously, in the quadrupole linear ion trap mass spectrum provided by the utility model, an electron multiplier is not needed for detecting ion signals.
Claims (2)
1. An ion signal detection arrangement for an ion trap mass spectrometer, comprising an ion trap mass analyser, an electrode set, and a current or voltage measuring means; the electrode group is arranged on one side of an ion extraction electrode, which is far away from an ion storage area, in the ion trap mass analyzer, and consists of more than 2 electrodes which are mutually electrically insulated, and except the electrode which is the farthest from the ion extraction electrode, the other electrodes are correspondingly provided with small holes for the passing of ions separated from the ion trap analyzer; wherein: when the electrode group is 2 electrodes, the current or voltage measuring device is directly connected with the 2 electrodes; when the electrode group is more than 3 electrodes, the working power supply is connected with the 2 electrodes nearest to the ion extraction electrode, and the current or voltage measuring device is connected with the 2 electrodes farthest.
2. The ion signal detection device of claim 1, wherein the ion trap mass analyzer is a three-dimensional ion trap, a linear ion trap, or a combination thereof and other types of mass analyzers.
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| CN110931341A (en) * | 2019-12-30 | 2020-03-27 | 中国计量科学研究院 | Ion signal detection device and method for ion trap mass spectrometer |
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