CN106908511B - A method for continuous analysis of large-scale ions by small ion trap mass spectrometry - Google Patents

Abstract

A method for continuous analysis of large-scale ions by a small ion trap mass spectrometer, the method keeps the ion trap in the sampling state by applying a fixed sinusoidal high-voltage radio frequency signal and an ion gate electrode DC signal on the ion trap electrode; and using the The ion cooling is assisted by a buffer gas; at the same time, the frequency of the sinusoidal low-voltage excitation signal loaded on the ion trap is cyclically scanned. When the excitation signal and the bound ions are resonantly excited, the ions will leave the ion trap through the slit or small hole on the exit electrode. , is detected by the ion detector, and the mass spectrometry analysis is completed, so as to achieve the effect of mass analysis while injecting and cooling the sample. This method has low requirements on radio frequency power, and does not need time-sequentially separated steps of ion sampling, ion cooling, scanning analysis, and ion removal. It can realize continuous, fast and efficient mass spectrometry analysis of ions in a large mass range, and can be quickly detected on-site by small ion trap mass spectrometers. It has a good application prospect.

Description

A method for continuous analysis of large-scale ions by small ion trap mass spectrometry

technical field

The invention relates to the field of detection of biochemical substances using a mass spectrometer, in particular to a detection method suitable for continuous, rapid and high-efficiency mass spectrometry analysis of ions in a large mass range by a miniaturized ion trap mass spectrometer.

Background technique

An ion trap is a device that uses a quadrupole electric field to capture, trap and analyze ions. Since Paul et al. proposed US2939952 in 1960, ion traps have been widely used in mass spectrometry, cold atom technology, and quantum information processing. Especially in the field of mass spectrometry, ion traps have become one of the most important mass analyzers due to their relatively simple structure and powerful time-tandem mass spectrometry capabilities.

In recent years, with the increasing demand for on-site detection and in-situ analysis, portable miniaturized mass spectrometers have been rapidly developed and applied. The first step in the miniaturization of the mass spectrometer is the miniaturization of the mass analyzer. Traditional ion traps are generally divided into three-dimensional ion traps and two-dimensional ion traps. In order to obtain an ideal quadrupole electric field, the electrode shape needs to be made into a hyperboloid shape, which is not convenient for the miniaturization of the instrument. Therefore, in recent years, various simplified ion traps have come out successively, such as three-dimensional cylindrical ion trap (US6762406), two-dimensional rectangular ion trap (US20040135080) and two-dimensional flat ion trap (CN101599410). In addition, thanks to the rapid development of MEMS technology, ion traps can be made smaller in size. However, in addition to the size of the ion trap itself, the power consumption and size of the instrument are also affected by the parameters and size of the control power supply, so how to develop a mass spectrometry method suitable for small ion trap mass spectrometers that can simplify the design of the instrument power supply appears very important.

Various ion trap analysis methods are mentioned in US Patents US4540884, US4736101 and US5420425. These methods all need to apply appropriate high-voltage radio-frequency signals on the electrodes of the ion trap, so that ions with different mass-to-charge ratios will be bound in the ion trap according to the law described by the Matthew equation, and move at different "duration frequencies". Among the various methods, the most commonly used method is to keep the frequency of the sinusoidal high-voltage radio frequency signal (RF) loaded on the ion trap electrode unchanged during mass analysis, and then scan the amplitude of the radio frequency, then the Matthew equation of ions with different mass-to-charge ratios The value of the stability parameter q will increase sequentially. When q is greater than 0.908, the ions will leave the ion trap from the stable state and arrive at the detector to complete the analysis. This RF amplitude scanning mode is also called mass selective unstable mode or boundary excitation mode. In order to improve the analysis performance, a fixed-frequency sinusoidal low-voltage excitation signal (AC) can be introduced on this basis, so that during the RF amplitude sweep process, the ion has not reached the unstable boundary (q<0.908), and the low-voltage excitation signal Resonance occurs and is scanned out of the ion trap. This RF amplitude scanning mode is called resonance excitation mode. However, the above-mentioned method based on RF amplitude scanning requires that the radio frequency system has a high quality factor and can achieve good scanning linearity. Therefore, most of the current RF power supplies are realized by means of coil resonance, which also makes it difficult to make the power supply small. In addition to the RF amplitude scanning mode, the amplitude of the high-voltage radio frequency signal can also be fixed, and the analysis of the ion trap can be completed by scanning its frequency. This mode needs to be coupled with a power amplifier with large power consumption, so it is not easy to miniaturize. Later, in the international patent (WO0129875A, PCT/GB00/03964), Ding Li et al. proposed a method for realizing mass spectrometry by using a square wave to drive a quadrupole field. In this method, a group of switches is used to connect the high-level and low-level voltages, and a square wave signal with a sweepable frequency is generated by switching the switches and output to the ring electrodes of the three-dimensional ion trap, and A low-voltage excitation signal is applied between the lid electrodes to achieve resonant excitation, thereby completing mass analysis. The power supply structure of this digital ion trap driving method is simple and the output is stable, and it has also been applied to the two-dimensional ion trap later. However, when the ion trap is driven by a high-voltage square wave signal, the boundary value of the stable parameter of the Matthew equation is q=0.7125, which is less than 0.908 when the sinusoidal drive is used, so it increases the low mass cut-off limit (LMCO) compared with the sinusoidal RF signal drive method. . Moreover, relevant studies have shown that for miniaturized ion traps, high radio frequency frequencies are required to complete ion confinement. This digital ion trap mode needs to scan the square wave frequency from high frequency to low frequency, so this mode is effective at low frequency. The analytical effect of the small ion trap needs to be further verified. In addition, another ion trap mass spectrometry analysis mode is also mentioned in patents US4736101 and US866952. It requires fixing the amplitude and frequency of the high-voltage radio frequency signal during mass analysis, and then scanning the frequency of the low-voltage excitation signal. When the frequency is close to the "long-term frequency" of ions and resonates, the ions will leave the ion trap and reach the detector to complete mass spectrometry analysis. . This model has been experimentally verified by Purdue University Dalton T.Snyder et al. Because it can use a fixed high-voltage radio frequency signal, has low power requirements, and can realize mass spectrometry in a large mass range, the method is suitable for small ion trap mass spectrometers.

On the other hand, in all the mass spectrometry methods mentioned above, a complete mass spectrometry analysis needs to go through four stages: ion injection, ion cooling, mass analysis and ion removal. Each stage generally takes tens of milliseconds, so a mass spectrometry analysis needs more than hundreds of milliseconds. This cannot meet the increasing needs of high-speed, high-throughput on-site mass spectrometry analysis. And for the ion source of continuous ionization, only the ions in the ion injection stage are effectively analyzed, while the ions in other stages are isolated from the ion trap by the ion gate, so the analysis efficiency of the ion trap (i.e. ion utilization = Injection time/total mass spectrometry time) is also limited. How to improve the analysis speed and efficiency of ion trap mass spectrometry is an important issue in the development of mass spectrometry. In 2008, ThermoFinnigan proposed a method of improving the efficiency and speed of mass spectrometry analysis by using a serial array of two ion traps in the US patent US20080142705, which combines the characteristics of high-pressure ion trap ion capture ability and low-pressure ion trap mass analysis effect. . However, this dual pressure trap mode adds a linear ion trap and buffer gas unit to the original ion trap mass spectrometer, which increases the complexity of the system and is not conducive to miniaturization. In the patent CNIO476678O published by Fudan University in 2015, a method of synchronously scanning the frequency of the high-voltage bound square wave and the low-voltage excitation square wave was proposed to realize the mass spectrometry analysis of the ion trap. This mode does not require the four sequential stages of conventional ion trap mass spectrometry, and only needs one ion resonance ejection stage to achieve ion mass analysis, which improves the analysis speed and efficiency of ion traps. However, in this mode, it is necessary to scan the frequency of the high-voltage radio frequency and the low-voltage excitation signal synchronously, so that the "long-term frequency" of the ion will change accordingly, and all the ions are at the same Matthew equation stability parameter q value (q<0.7125) If the resonant excitation occurs and is expelled from the ion trap, in order to avoid the re-excitation of ions at the boundary (q=0.7125), it is necessary to limit the frequency scanning range of the radio frequency signal, thereby limiting the mass analysis range of the ion trap. And it also faces the same problem as the square wave driving the ion trap mentioned above.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method suitable for continuous analysis of large-scale ions by small-scale ion trap mass spectrometry, so as to overcome the inability of existing mass spectrometry analysis methods to take into account the power supply design and performance requirements suitable for miniaturization, large mass analysis range and high ion utilization. Contradictions such as rate and rapid analysis.

Technical scheme of the present invention is as follows:

A method for continuous analysis of large-scale ions by a small ion trap mass spectrometer, characterized in that: using a single ion trap to perform the following steps synchronously:

1) Apply a fixed sinusoidal high-voltage radio frequency signal and a fixed ion gate electrode DC signal on the ion trap electrode, so that the ion trap is always in the state of ion sampling;

2) The ions entering the ion trap complete the ion cooling through the collision with the buffer gas, and the ions with different mass-to-charge ratios are bound in the ion trap and vibrate at different frequencies;

3) The frequency of the low-voltage excitation signal loaded on the ion trap is cyclically scanned. When the low-voltage excitation signal resonates with the bound ions, the ions leave the ion trap through the slit or small hole on the exit electrode and are detected by the ion trap. device detection;

In this way, a single ion trap can be used to simultaneously perform continuous sampling and continuous scanning mass spectrometry on ions. The low-voltage excitation signal scans one cycle per cycle, and the ion trap can obtain a mass spectrum of all injected ions in this cycle.

In the present invention, the low-voltage excitation signal is an AC sinusoidal waveform, and its frequency adopts a monotonous form from small to large or from large to small to carry out periodic cycle scanning, and its amplitude remains constant or equal to The frequencies are scanned synchronously.

In the present invention, the high-voltage radio frequency signal is a sine wave, and keeps a fixed frequency and amplitude throughout the mass spectrometry analysis process.

In the present invention, the ion trap is a three-dimensional ion trap, a two-dimensional ion trap, or any other ion trap that utilizes a quadrupole electric field for mass analysis.

In the present invention, the outgoing electrode is the rear end cover electrode, ring electrode, X-direction electrode, Y-direction electrode of the ion trap, or any other electrode with a slit or a small hole to provide a channel for ions to reach the detector.

In the present invention, the buffer gas is helium, nitrogen or any other neutral gas.

The present invention has the following advantages and outstanding effects simultaneously:

① The analysis method only needs to scan the low-voltage excitation signal, but does not need to scan the high-voltage radio frequency signal, so it reduces the system’s requirements on the radio frequency power supply and facilitates miniaturization;

② In the method described above, because the radio frequency signal is fixed, different ions are resonantly excited with different q values, so that ions in a large mass range stored in the ion trap can be effectively analyzed;

③In the method described above, ion sampling, ion cooling and scanning analysis all take place in the same scanning cycle, so all injected ions will be effectively analyzed, that is, 100% ion utilization can be achieved;

④At the same time, the entire analysis process can be completed in only one stage, which improves the analysis speed of ion trap mass spectrometry compared with the traditional mode.

Description of drawings

Fig. 1 is a control timing diagram of a method for continuous analysis of large-scale ions by a small-sized ion trap mass spectrometer involved in the present invention in three cycles of low-voltage excitation signal cycle scanning.

Fig. 2 is a schematic diagram of time series comparison between the traditional RF amplitude scanning mode, the traditional AC frequency scanning mode and the analysis method involved in the present invention.

Fig. 3 is a structural schematic diagram of a rectangular ion trap mass spectrometer in a secondary vacuum cavity used to verify the effect of the analysis method involved in the present invention.

Fig. 4 is a structural diagram of a rectangular ion trap mass analyzer used to verify the effect of the analysis method involved in the present invention.

Fig. 5 is a schematic diagram of loading control signals required to control the rectangular ion trap by using the analysis method of the present invention.

Fig. 6 is a mass spectrum of human hemotensin at a concentration of 100 μm/mL obtained by the analysis method of the present invention.

Fig. 7 is a mass spectrum of amitriptyline at a concentration of 50 μm/mL obtained by the analysis method of the present invention at different scanning periods (20ms-300ms).

Fig. 8 is a schematic diagram of loading control signals required to control the three-dimensional ion trap mass analyzer by using the analysis method of the present invention.

In the figure: 1-ion gate electrode; 2-X direction electrode; 3-Y direction electrode; 4-rear end cover electrode; 5-ion detector; 6-atmospheric pressure ion source; 7-first-stage vacuum chamber; Second-stage vacuum chamber; 9-atmospheric pressure interface sampling cone; 10-quadrupole rod; 11-ion lens electrode; 12-ion optical element; 13-capillary for introducing buffer gas. 14-ring electrode.

Detailed ways

A method for continuously analyzing ions in a large range by a small ion trap mass spectrometer provided by the present invention will be further described below in conjunction with the drawings and specific embodiments.

The present invention provides a method for continuous analysis of large-scale ions by a small ion trap mass spectrometer, which uses a single ion trap to perform the following steps synchronously:

1) Apply a fixed sinusoidal high-voltage radio frequency signal and a fixed ion gate electrode DC signal on the ion trap electrode, so that the ion trap is always in the state of ion sampling;

2) The ions entering the ion trap complete the ion cooling through the collision with the buffer gas, and the ions with different mass-to-charge ratios are bound in the ion trap and vibrate at different frequencies;

3) The frequency of the low-voltage excitation signal loaded on the ion trap is cyclically scanned. When the low-voltage excitation signal resonates with the bound ions, the ions leave the ion trap through the slit or small hole on the exit electrode and are detected by the ion trap. device detection;

In this way, a single ion trap can be used to simultaneously perform continuous sampling and continuous scanning mass spectrometry on ions. The low-voltage excitation signal scans one cycle per cycle, and the ion trap can obtain a mass spectrum of all injected ions in this cycle.

In the present invention, the low-voltage excitation signal is an AC sinusoidal waveform, and its frequency adopts a monotonous form from small to large or from large to small to carry out periodic cycle scanning, and its amplitude remains constant or equal to The frequencies are scanned synchronously; the high-voltage radio frequency signal is a sine wave, and keeps a fixed frequency and amplitude throughout the mass spectrometry analysis process.

In the present invention, described ion trap is three-dimensional ion trap, two-dimensional ion trap, or any other ion trap that utilizes quadrupole electric field to carry out mass analysis; Described exit electrode is the rear end cover electrode of ion trap, ring electrode, X-direction electrodes, Y-direction electrodes, or any other electrodes with slits or small holes to provide channels for ions to reach the detector.

In the present invention, the buffer gas is helium, nitrogen or any other neutral gas.

Fig. 1 is a control timing diagram of a method for continuously analyzing large-scale ions by a small-sized ion trap mass spectrometer involved in the present invention during three cycles of low-voltage excitation signal cycle scanning. The present invention fixes the amplitude and frequency of the sinusoidal high-voltage radio frequency signal (RF) loaded on the ion trap electrode when performing mass spectrometry, and adjusts and selects a suitable DC voltage of the ion gate electrode (Gate), so that the ion trap is always in the ion trap. At the same time, a neutral buffer gas is introduced into the ion trap to assist in the completion of ion cooling, so that ions with a large mass range with different mass-to-charge ratios can be bound in the ion trap and move at different "duration frequencies"; At the same time, the recirculation scans the frequency of the low-voltage excitation signal (AC) loaded on the ion trap electrode. When the low-voltage excitation signal resonates with the bound ions, the ions will leave the ion trap through the slit or small hole on the exit electrode. , is detected by the detector outside the ion trap to complete the mass spectrometry analysis, so that this method achieves the effect of scanning and analyzing while injecting and cooling the sample; the low-voltage excitation signal scans one cycle per cycle, and the ion trap can obtain a Mass spectra of all injected ions during the cycle. The ion trap used in this invention can be any ion trap using quadrupole electric field for mass analysis, such as three-dimensional ion trap or two-dimensional ion trap. Here we first take a two-dimensional linear ion trap driven by a sinusoidal high-voltage radio frequency signal and a sinusoidal low-voltage excitation signal as an example, to elaborate on the principle and effect of the invention:

According to Newton's second law and electric field force formula, the law of motion of ions after entering the ion trap has the same form as the second-order linear differential equation proposed by Mathieu in 1868 in theory. Without considering the electric field in the Z direction (the electric field in the Z direction affects the depth of the potential well, and generally only plays the role of axial compression of ions), the collision between ions and the influence of higher-order fields, the Mathieu formula can deduce the stability characteristics of ion motion, The parameters affecting stability can be expressed as:

Among them, V _RF is the amplitude of the applied RF AC voltage, Ω is the angular frequency of the RF voltage, U _RF is the magnitude of the DC bias, m/z is the mass-to-charge ratio of the ion, x ₀ and y ₀ are the ion traps, respectively field radius. In the traditional RF amplitude scanning mode, the DC bias U _RF of the high-voltage RF signal is generally set to zero, and then the amplitude V _RF of the RF voltage is scanned. When the q _x value is greater than 0.908, the ions will get rid of the ion trap control and move from the X direction Slits in the electrodes eject the ion trap. When the low-voltage excitation signal (AC) is introduced, the kinetic energy of the ions in the X direction can be enhanced through the resonance excitation mode, and the ion q _x value can be ejected before it reaches 0.908.

According to the relevant theory of the Mathieu equation, the vibration frequency ω _x,n (n is the vibration order) of the ion in the X direction in the fourth-order field can be expressed as:

where the coefficient β _x related to the vibration frequency of the ion is defined by the iterative formula related to the parameters a _x and q _x :

Through the formulas (1), (2), (3), it can be obtained that when the size of the ion trap (x ₀ , y ₀ ) is fixed and the radio frequency f _RF (Ω=2πf _RF ) is fixed, only the basic vibration of ions in the X direction is considered In the case of frequency f ₀ (f ₀ =ω _x,0 /2π):

m/z=V _RF ×f(q _x ) q _x =g(β _x ) β _x =χ(f ₀ ) (4)

thereby:

m/z=V×f{g[χ(f ₀ )]}=V×Ψ(f ₀ ) (5)

That is, the mass-to-charge ratio of ions will become a function of the basic frequency f ₀ of ion vibration. By scanning the frequency f _AC of the low-voltage excitation AC signal, f ₀ can be scanned through resonance excitation to complete mass analysis. Different from the traditional RF amplitude scanning mode in which all mass-to-charge ratio ions are ejected under the same stability parameter q value, in this method of scanning the frequency of the low-voltage excitation signal, different ions are separated by different stability parameters The q value completes the resonance excitation. This analysis method of sweeping the frequency of the low-voltage excitation signal is also called the AC frequency sweep mode. FIG. 2 shows a schematic diagram of the timing comparison of the traditional RF amplitude scanning mode, the traditional AC frequency scanning mode and the analysis method involved in the present invention. In the traditional RF amplitude sweep mode and the traditional AC frequency sweep mode, a complete mass analysis needs to go through four stages: ion introduction, ion cooling, mass analysis, and ion emptying. Each stage takes tens of milliseconds, so the entire analysis cycle takes hundreds of milliseconds. However, the method described in the present invention combines ion sampling, ion cooling and mass analysis because it omits each separation stage in the mass spectrometry process. Therefore, in the traditional RF scanning mode and the traditional AC scanning In the period of performing one quality analysis in the mode, multiple analysis cycles involved in the present invention can be performed. In addition, in the two existing traditional analysis modes, for the ion source with continuous ionization, only the ions in the ion injection stage can enter the ion trap and be effectively analyzed, and the ions at other times are blocked by the ion gate electrode. Outside the ion trap, so ion utilization is limited. However, the method of this patent maintains the state of ion injection all the time, so theoretically 100% ion utilization can be achieved.

In the following, we first use a two-dimensional rectangular ion trap as an implementation case to further elaborate the content of the present invention.

Example 1

Fig. 3 is a structural schematic diagram of a rectangular ion trap mass spectrometer in a secondary vacuum cavity used to verify the effect of the analysis method involved in the present invention. It includes an atmospheric pressure ion source 6 that can be ionized in an atmospheric environment and a two-stage vacuum chamber with a pressure gradient. The first-stage vacuum chamber 7 includes an atmospheric pressure interface sampling cone 9 for sampling, a quadrupole rod 10 and ion A lens electrode 11, an ion optical element 12 is arranged between the two-stage vacuum chambers, and they can cooperate to carry out ion transmission; an ion detector 5 and a capillary 13 for introducing helium as a buffer gas are included in the second-stage vacuum chamber 8 , the mass analyzer used is a rectangular ion trap. The structural diagram of the rectangular ion trap is shown in Figure 4, which includes: an ion gate electrode 1, a pair of X-direction electrodes 2 with ion exit slits, a pair of Y-direction electrodes 3 and a rear end cover electrode 4. For the analysis method involved in the present invention, the loading mode of the high-voltage radio frequency signal and the low-voltage excitation signal is shown in FIG. 5 . Firstly, a resonant RF power supply is used to control the rectangular ion trap, and RF voltages with a frequency f _RF of 1.021 MHz and opposite phases are applied to the electrodes in the X direction and the plate in the Y direction of the rectangular ion trap to form a A quadrupole field is used to confine the ions. Then, the mass analysis of the rectangular ion is accomplished by scanning the frequency f _AC of the low-voltage excitation AC signal, which is generated by a self-made auxiliary AC signal generating circuit, coupled to the RF voltage through a coil transformer, and drives the rectangular ion trap. The auxiliary AC signal generating circuit is composed of FPGA chip ep3c55f484i7, high-speed DA chip and power amplifier, which can realize undistorted output up to 500kHz. The frequency resolution of frequency sweep is 50Hz, and the amplitude range is ±10V.

Figure 6 shows the spectrogram of the 100 μg/mL human hemotensin solution obtained by using a small ion trap mass spectrometer involved in the present invention for continuous analysis of large-scale ions, wherein the high radio frequency signal amplitude is 884.5V , the frequency is 1.021MHz, the voltage of the ion gate electrode 1 is 6V, the voltage of the rear end cover electrode 4 is 60V, the amplitude of the low-voltage excitation signal (AC) is 3.5V, the frequency is linearly scanned from 500kHz to 50kHz, and the scanning period is 100ms. It can be seen from the figure that the range of the mass axis exceeds 2500 mass numbers. This experiment shows that although the analysis method invented by this patent combines the various time series stages in the traditional analysis method into one, it can still perform effective mass spectrometry analysis.

Fig. 7 is a mass spectrogram of 50 μg/mL amitriptyline hydrochloride solution obtained by using a small ion trap mass spectrometer involved in the present invention for continuous analysis of a wide range of ions. The RF frequency used in the experiment is 1.021MHz, the amplitude is 274.5V, the voltage of the ion gate electrode 1 is 6.4V, the voltage of the rear electrode 4 cover is 60V, the amplitude of the voltage excitation AC signal is 2V, and the frequency is cycled from 500kHz to 50kHz Cyclic scanning, the scanning period is changed from 20ms to 300ms in turn. Experiments show that for the rectangular ion trap mass spectrometer in the secondary vacuum chamber used in this experiment, the minimum scan period of this patent analysis method is only 20ms. Previous studies have shown that the system generally needs 160ms for sample injection, 10ms for cooling, 100ms for analysis, and 10ms for cleanup in traditional sweep mode. The analysis cycle is about 280ms, and the ion utilization rate is about 57.1%. That is, this patent analysis method increases the analysis speed of the rectangular ion trap by nearly 14 times, and because the ion trap always maintains the state of ion injection during the entire mass spectrometry analysis process, this patent analysis method theoretically achieves 100% ion utilization. .

In addition, it should be noted that in this embodiment, the rear end cover electrode 4 maintains a relatively high amplitude during the analysis process, and the ion detector is located near the X-direction electrode, so ions leave the ion trap from the slit on the X-direction electrode . If the electrode of the rear end cover 4 maintains a suitable low amplitude during the analysis process, and the ion detector is placed near the electrode 4 of the rear end cover, fast mass spectrometry analysis of the base axis mass selective emission can be realized, and ions will flow from the ion gate electrode 1 sample injection, and then cyclically scan the frequency of the low-voltage excitation signal to achieve resonance excitation, and finally the ions leave the ion trap from the rear end cover electrode 4 of the ion trap to complete the mass analysis.

Example 2

The rectangular ion trap mentioned in Example 1 can adopt a small ion trap mass spectrometer involved in the present invention to carry out continuous analysis of a large range of ions. After modification, this method can also be applied to the efficient and rapid analysis of a large mass range in a three-dimensional ion trap. As shown in Figure 8, for a three-dimensional ion trap, apply a fixed high-voltage radio frequency signal on the ring electrode 14, and keep the voltage of the ion gate 1 fixed, the ion trap can be kept in the state of ion injection, and at the same time, scan and load The frequency of the low-voltage excitation signal on the end cap electrode 4 can achieve the same effect as the two-dimensional ion trap that performs mass analysis while injecting samples and cooling.

Claims (8)

1. A method for continuous analysis of large-scale ions by a small ion trap mass spectrometer, characterized in that: a single ion trap is utilized to carry out the following steps synchronously: 1) Apply a fixed sinusoidal high-voltage radio frequency signal and a fixed ion gate electrode DC signal on the ion trap electrode, so that the ion trap is always in the state of ion sampling; 2) The ions entering the ion trap complete the ion cooling through the collision with the buffer gas, and the ions with different mass-to-charge ratios are bound in the ion trap and vibrate at different frequencies; 3) Continuously periodically scan the frequency of the low-voltage excitation signal loaded on the ion trap. When the low-voltage excitation signal resonates with the bound ions, the ions leave the ion trap through the slit or small hole on the exit electrode and are captured by the ion trap. Detector detection outside the well; In this way, a single ion trap can be used to simultaneously perform continuous sampling and continuous scanning mass spectrometry on ions. The low-voltage excitation signal scans one cycle per cycle, and the ion trap can obtain a mass spectrum of all injected ions in this cycle. 2. according to claim 1, a kind of small-sized ion trap mass spectrometer carries out the method for large-scale ion continuous analysis, it is characterized in that: described low voltage excitation signal is AC sinusoidal waveform, and its frequency adopts the form of monotone to carry out periodic cycle scanning , its amplitude remains constant during the sweep or sweeps synchronously with the frequency. 3. The method for continuously analyzing large-scale ions by a small ion trap mass spectrometer according to claim 1, characterized in that: the high-voltage radio frequency signal is a sine wave with a constant frequency and amplitude. 4. The method for continuous analysis of large-scale ions by a small ion trap mass spectrometer according to claim 1, characterized in that: said ion trap is a three-dimensional ion trap that utilizes a quadrupole electric field for mass analysis. 5. The method for continuously analyzing large-scale ions by a small-sized ion trap mass spectrometer according to claim 1, characterized in that: said ion trap is a two-dimensional ion trap that utilizes a quadrupole electric field for mass analysis. 6. according to claim 4, a kind of small-sized ion trap mass spectrometer carries out the method for large-scale ion continuous analysis, it is characterized in that: described exit electrode is the rear end cover electrode that has slit or aperture of three-dimensional ion trap or ring electrode to provide ions to reach the detector. 7. The method for continuous analysis of large-scale ions by a small ion trap mass spectrometer according to claim 5, characterized in that: the exit electrode is an X-direction electrode with a slit or a small hole in a two-dimensional ion trap , Y direction electrode or rear end cover electrode to provide ions to reach the detector. 8. A method for continuous analysis of large-scale ions by a small ion trap mass spectrometer according to any one of claims 1-7, wherein the buffer gas is a neutral gas.