CN214374478U - Ion signal detection device for sector magnetic field mass spectrometer - Google Patents
Ion signal detection device for sector magnetic field mass spectrometer Download PDFInfo
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Abstract
The utility model relates to an ion signal detection device for a sector magnetic field mass spectrometer, which comprises a sector magnetic field mass analyzer, an electrode group and a current and voltage measuring device; the electrode group is arranged on one side of the fan-shaped magnetic field ion extraction end, except the electrode farthest from the fan-shaped magnetic mass spectrum ion extraction end, the other electrodes are correspondingly provided with small holes for passing the ions separated from the fan-shaped magnetic mass spectrum mass analyzer; wherein: when the signal detection device is 2 electrodes, the current and voltage detection device is directly connected with the 2 electrodes; when the electrode group is 3 or 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's technical field, concretely relates to an ion signal detection device for fan-shaped magnetic field mass spectrograph.
Background
Sector magnetic field mass spectrometers are the earliest mass spectrometry instruments, and are mainly classified into single-focus mass spectrometers and double-focus mass spectrometers at present. The appearance of the sector magnetic field mass spectrometer has extremely important significance in the development history of the mass spectrometer, has the advantages of capability of providing accurate mass number information, independence of resolution ratio and mass number of ions, good reproducibility, capability of scanning quickly and the like, is a technical classic and mature mass spectrometer, has wide application in scientific research and practical application, and is mainly used in the fields of detection of geological elements and trace dioxin and the like. The basic principle of the sector magnetic field mass analyzer is as follows: a sector magnetic field generated by an electromagnet is used to distinguish charged ions of different mass-to-charge ratios. When a large number of sample ions generated by the ion source are introduced into the magnetic sector, these charged particles of different mass-to-charge ratios are deflected differently by the magnetic sector, and only ions of a certain mass will reach the detector, while heavier and lighter ions will collide with the flight tube. When the magnetic field strength and the ion acceleration voltage excited from the ion source are kept fixed, ions with a certain mass-to-charge ratio can be screened out. An ion detector is placed at the ion output end and can detect and record selected ion signals, namely mass spectrum signals of sample ions, and the structural principle of a sector magnetic field mass analyzer is shown in figure 1. It is a uniform fan-shaped magnetic field generated by laminated magnets, the direction of the magnetic field is from the outer arc of the fan to the inner arc. In fig. 1, 1 is a beam of charged ions of different mass-to-charge ratios entering a magnetic field, assuming the ions are positively charged and enter the magnetic field at the same velocity. After entering the magnetic field, charged ions are deflected towards the direction of the center of the circular arc due to the Lorentz force acted by the constant magnetic field, and because the Lorentz forces acted on the ions with different mass-to-charge ratios in the magnetic field are different, the curvature radii of the ions moving in the magnetic field are also different, and the following formula is met:
m/z＝r2B2/2V (8)
where m is the mass of the charged ion, z is the amount of charge charged, r is the radius of the circular motion of the ion in the magnetic field, B is the strength of the magnetic field, and V is the initial velocity of the ion as it enters the magnetic field. When the magnetic field intensity and the initial speed are constant, the deflection radius of ions with a large mass-to-charge ratio is larger, the deflection radius of ions with a small mass-to-charge ratio is smaller, 2 in the figure 1 can collide with the upper side of the pipe wall due to the large mass-to-charge ratio, 3 can collide with the lower side of the pipe wall due to the small mass-to-charge ratio, 4 and 5 represent charged ions with a certain mass-to-charge ratio which can smoothly pass through the magnetic field selection, and then the charged ions are detected by a detector to finally form a mass spectrogram of an analyzed sample.
The ion detector of the mass analyser of a magnetic sector mass spectrometer is a so-called channel electron multiplier. The material used has high efficiency secondary electron emission capability, and FIG. 2 is a schematic diagram of a channel electron multiplier. 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 magnetic sector mass analyzer collide with the surface of the channel electron multiplier under the influence of an electric field, a plurality of secondary electrons are 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.
Fig. 2, 6, is a schematic diagram of an electrospray ion source, in which a sample is ionized by the ion source to generate sample ions 7, and then the sample ions are sent to a fan-shaped magnetic field mass analyzer 8 under the action of an accelerating electric field, so as to keep the sample ions having the same initial velocity when entering a magnetic field, and only the sample ions with a certain mass-to-charge ratio can pass through the magnetic field through the selection action of the fan-shaped magnetic field, while the rest of the charged ions can collide with the upper part or the lower part of a flight duct. When ions pass through the magnetic field, the ions enter the detector 9, and ion current or voltage signals corresponding to different voltages are recorded, so that a mass spectrogram of the analyzed sample is obtained, and chemical composition information of the analyzed sample is obtained. Briefly, a magnetic sector mass spectrometer consists of three most major components, namely: (1) an ion source 6 that turns the sample into ions, (2) a magnetic sector mass analyser 8 that can distinguish the mass to charge ratio of the ions and (3) an electron multiplier 9 that can detect the ions.
The electron multiplier is an ion detection device commonly used by some common mass spectrometers at present, such as a quadrupole mass spectrometer, a time-of-flight mass spectrometer, and a complex mass spectrometer composed of a plurality of mass analyzers, and the electron multiplier has the shadow of the electron multiplier, and is responsible for the tasks of recording ion signals and obtaining mass spectrograms of the mass spectrometer.
Fig. 3 is a schematic diagram of the operation of the electron multiplier. In fig. 3, 10 is a sample ion generated by an ion source, when the ion 10 with certain kinetic energy hits the surface 11 of an electron multiplier constructed by a material with secondary electron emission capability, secondary electrons 121 and 122 will be generated, and under the action of the operating voltage of the electron multiplier, secondary electrons 131, 132, 133, 134 will be generated by continuous collision, and so on, the number of secondary electrons will double after each collision, and finally more and more secondary electrons will be generated and pass through the outlet 15 of the electron multiplier. The electron current signal resulting from the ions 10 undergoing multiple multiplications is collected and measured, i.e., a mass spectral signal associated with the sample ions 10 can be obtained.
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:
Q＝N*q＝107×1.6×10-19＝1.6×10-12C (1)
if 1000 ions of the same mass to charge ratio enter the ion detector per second, the resulting electron charge should theoretically be:
Q＝N*q＝1000×1.6×10-19×107＝1.6×10-9C (2)
I＝Q/t＝1.6×10-9C/S＝1.6×10-9A (3)
if this current signal is converted into a voltage signal, it is assumed that the resistance used is 106Ohm, then the voltage that can be measured is:
U＝I*R＝1000000×1.6×10-9＝1.6×10-3V (4)
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
The utility model aims at overcoming the defect that prior art exists, providing a simple structure, with low costs, can realize the ion mass spectrum signal's high sensitivity test be used for fan-shaped magnetic field mass spectrograph's ion signal detection device.
Realize the utility model discloses the technical scheme of purpose is: an ion signal detection device for a sector magnetic field mass spectrometer is provided with an ion source, a sector magnetic field mass analyzer, an electrode group and a measuring device; the ion source is arranged at one end of the fan-shaped magnetic field mass analyzer; and the other end of the magnetic field mass analyzer is provided with an electrode group connected with a detection device.
In the technical scheme, the electrode group is provided with at least 2 electrodes, and except for the electrode farthest from the sector magnetic field mass analyzer, other electrodes are correspondingly provided with small holes for passing through ions separated from the sector magnetic field mass analyzer.
The electrode group has 2 electrodes, and the monitoring device is directly connected with the 2 electrodes.
In the technical scheme, the electrode group is provided with 3 or more than 3 electrodes, two electrodes close to the sector magnetic field mass analyzer are connected with a working power supply, and two electrodes far away from the sector magnetic field mass analyzer are connected with a measuring device.
In the technical scheme, the measuring device is a current or voltage measuring device.
The sector magnetic field mass analyzer in the technical scheme is a single-focus sector magnetic field or a double-focus sector magnetic field or a combination thereof.
The ion source in the technical scheme is an electrospray ion source.
A detection method of an ion signal detection device is characterized in that ions separated by a fan-shaped magnetic field mass analyzer move between electrodes at a high speed, and an ion mass spectrum signal is obtained by measuring current generated by the movement of the ions between the two electrodes.
According to the technical scheme, when the electrode group is 2 electrodes, the current or voltage on the 2 electrodes is tested through a current or voltage measuring device, and mass spectrum signals are obtained through Fourier transform.
According to the technical scheme, when the electrode group is 3 or more than 3 electrodes, voltage is loaded on 2 electrodes close to the sector magnetic field mass analyzer through the working power supply, so that ions separated from the sector magnetic field mass analyzer directionally move to the farthest electrode to form current, and the current or voltage on 2 electrodes far away from the sector magnetic field mass analyzer is measured through a device for measuring the current or voltage to obtain a mass spectrum signal.
After the technical scheme is adopted, the utility model discloses following positive effect has:
(1) the utility model does not use the ion detector, so the problems of aging and damage of the detector and the service life of the ion detector are avoided;
(2) the utility model has no problem of unequal multiplication efficiency of ions with different sizes because the current signal generated by the movement of the ions is measured;
(3) the utility model discloses theoretically, the produced electric current of N ion will be strictly equal to the produced electric current of an ion N times, so do not have so-called signal "saturation" phenomenon yet, do not have so-called quality discrimination effect yet, the produced mass spectrum signal intensity of "big ion" and "little ion" of the same number promptly will be the same completely, and the quantitative analysis result is accurate.
(4) The utility model discloses owing to do not use ion detector, do not have maintenance and the change to ion detector, saved the spending.
Drawings
In order that the present invention may be more readily and clearly understood, the following detailed description of the present invention is given in conjunction with the accompanying drawings, in which
Figure 1 is a schematic diagram of a magnetic sector mass analyser.
Fig. 2 is a schematic diagram of a conventional electrospray ionization fan magnetic field mass spectrometer.
Fig. 3 is a schematic diagram of the operation of the electron multiplier.
Fig. 4 is a schematic structural diagram of an electrospray ionization-sector magnetic field mass spectrometer-ion signal detection system constructed by the present invention.
Detailed Description
(example 1)
The utility model is provided with an ion source 16, a sector magnetic field mass analyzer 18, an electrode group and a measuring device; the ion source 16 is disposed at one end of a sector magnetic field mass analyzer 18; the other end of the magnetic field mass analyzer 18 is provided with an electrode group connected with a detection device; the electrode group is provided with 2 electrodes, and the monitoring device is directly connected with the 2 electrodes; the measuring device is a current or voltage measuring device; the sector magnetic field mass analyzer 18 is a single-focus sector magnetic field or a double-focus sector magnetic field or a combination thereof; the ion source 16 is an electrospray ion source.
The electrodes in the electrode group are made of conductive materials, and the shape of the electrodes can be plane, curved or any other shape.
(example 2)
Referring to fig. 4, this embodiment is substantially the same as embodiment 1, and its distinctive features are: the electrode group has 3 electrodes (such as a first electrode 20, a second electrode 21 and a third electrode 22 in the figure), two electrodes close to the fan-shaped magnetic field mass analyzer 18 are connected with a working power supply, two electrodes far away from the fan-shaped magnetic field mass analyzer 18 are connected with a measuring device, and except for the electrode farthest from the fan-shaped magnetic field mass analyzer 18, the other electrodes are respectively provided with small holes 19 for passing ions separated from the fan-shaped magnetic field mass analyzer.
(example 3)
A detection method of an ion signal detection device is characterized in that an ion source 16 sprays sample ions 17, the sample ions 17 enter a fan-shaped magnetic field mass analyzer 18, the ions separated by the fan-shaped magnetic field mass analyzer move at high speed between electrodes, and an ion mass spectrum signal is obtained by measuring current generated by the movement of the ions between the two electrodes.
When the electrode group is 2 electrodes, the current or the voltage on the 2 electrodes is tested by a current or voltage measuring device, and a mass spectrum signal is obtained by Fourier transform.
When the electrode group is 3 or more than 3 electrodes, voltage is loaded on 2 electrodes close to the fan-shaped magnetic field mass analyzer through a working power supply, so that ions separated from the fan-shaped magnetic field mass analyzer directionally move to the farthest electrode to form current, and the current or the voltage on the 2 electrodes far away from the fan-shaped magnetic field mass analyzer is measured through a device for measuring the current or the voltage to obtain a mass spectrum signal.
Assuming that n ions separated by the magnetic sector mass spectrometer are accelerated to 2000eV, the time taken for these ions to pass through the two ion current detecting electrodes at high speed is 10-7Second (i.e., 0.1 microseconds), the current generated is:
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:
U＝I*R＝1.6nE-12×106 ＝1.6n×10-6 V (6)。
the above-mentioned embodiments, further detailed description of the objects, technical solutions and advantages of the present invention, it should be understood that the above-mentioned embodiments are only specific embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (7)
1. An ion signal detection device for a sector magnetic field mass spectrometer, characterized in that: the device comprises an ion source, a fan-shaped magnetic field mass analyzer, an electrode group and a measuring device; the ion source is arranged at one end of the fan-shaped magnetic field mass analyzer; and the other end of the magnetic field mass analyzer is provided with an electrode group connected with a detection device.
2. The ion signal detection apparatus for a magnetic sector mass spectrometer according to claim 1, wherein: the electrode group has at least 2 electrodes, except the electrode farthest from the fan-shaped magnetic field mass analyzer, the other electrodes are respectively provided with small holes for passing the ions separated from the fan-shaped magnetic field mass analyzer.
3. The ion signal detection apparatus for a magnetic sector mass spectrometer according to claim 2, characterized in that: the electrode group has 2 electrodes, and the monitoring device is directly connected with 2 electrodes.
4. The ion signal detection apparatus for a magnetic sector mass spectrometer according to claim 2, characterized in that: the electrode group is provided with 3 or more than 3 electrodes, two electrodes close to the fan-shaped magnetic field mass analyzer are connected with a working power supply, and two electrodes far away from the fan-shaped magnetic field mass analyzer are connected with a measuring device.
5. The ion signal detection apparatus for a magnetic sector mass spectrometer according to claim 3 or 4, characterized in that: the measuring device is a current or voltage measuring device.
6. The ion signal detection apparatus for a magnetic sector mass spectrometer according to claim 3 or 4, characterized in that: the sector magnetic field mass analyzer is a single-focus sector magnetic field or a double-focus sector magnetic field or a combination thereof.
7. The ion signal detection apparatus for a magnetic sector mass spectrometer according to claim 3 or 4, characterized in that: the ion source is an electrospray ion source.
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Effective date of registration: 20211108 Address after: 213000 9, Yang Road, West Taihu science and technology industry, Changzhou, Jiangsu Patentee after: CHANGZHOU PANNUO APPARATUS CO.,LTD. Address before: 315211, Fenghua Road, Jiangbei District, Zhejiang, Ningbo 818 Patentee before: Ningbo University |
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