An ion trap-time-of-flight tandem reaction mass spectrometry device and detection method

Abstract

The present invention belongs to the technical field of mass spectrometry analysis, and is an ion trap-time of flight reaction mass spectrometry combined with a femtosecond laser device and its operation method. The device of the present invention includes: an ion source, a conical body, a quadrupole system, an ion trap system, a femtosecond laser system, and a time of flight mass spectrometry system; the laser bombards the target through a channel to generate plasma; the carrier gas is introduced through a pipeline by a pulse valve, and then flies into a fast flow tube, where it is cooled and forms ions; the reaction gas is introduced into the flow tube by controlling the pulse valve; the ions react with the reaction gas and then enter the quadrupole system to allow the ions to pass through by mass selection; then they are sent into the ion trap, and then interact with the femtosecond laser, and finally enter the time of flight mass spectrometry. This device can achieve reactions for transient species, allow ion reactions, and send them to the mass spectrometer for mass analysis; it can also obtain spectral information by the interaction of ions with the femtosecond laser.

Description

Technical Field

[0001] The present invention belongs to the technical field of mass spectrometry analysis, and particularly relates to an ion trap-time of flight tandem reaction mass spectrometry device and a detection method. Background Art

[0002] The research on gas-phase ion structures and reactions is a frontier research field in chemistry. It explores the processes and reaction mechanisms of some important elementary reactions in chemistry at the atomic and molecular levels. Among them, ion-molecule reactions are an important type of gas-phase reaction. Since ions can be rapidly separated and other controllable operations can be achieved through means such as mass spectrometry, the research on such reactions has become a popular research field in science. Since many ions are highly reactive species with short lifetimes, higher requirements are imposed on the analytical instruments. In addition, many molecular ion reactions are multi-step reactions, and many reaction products can continue to react with neutral molecules. Therefore, tandem mass spectrometry is required to study these reaction processes.

[0003] An important means for studying molecular ion reactions is a mass spectrometer. A mass spectrometer is a device that obtains compositional information by measuring the mass-to-charge ratio of substances. It is one of the most widely used scientific instruments currently. A mass spectrometer mainly consists of an ion source, a mass analyzer, a detector, and a vacuum system. Among them, the mass analyzers of mass spectrometry include quadrupoles, ion traps, time of flight, ion cyclotron resonance, etc.

[0004] A quadrupole is a commonly used mass spectrometry analysis and mass selection tool. It applies an alternating electric field with a 180-degree phase difference and equal amplitude on two pairs of electrodes in the x and y directions. Only ions that meet specific conditions can pass through the quadrupole with stable oscillations, reach the monitor, and be detected, achieving the purpose of mass selection.

[0005] An ion trap is a mass analyzer composed of an alternating electric field combined with a DC end cap. It has many structures. Traditional 3D ion traps and linear ion traps, such as the linear ion trap of a certain company (United States Patent 5,420,425), and the rectangular ion trap invented by a certain doctor (United States Patent 6,838,666), etc. The structures of ion traps are very diverse and can be designed in different forms according to different research needs.

[0006] Ion traps can store ions and achieve various functions such as mass selection and mass analysis through the design of electric fields. Mass selection is mainly achieved by using the SWIFT (Stored Waveform Inverse Fourier Transform) technique. A radio frequency voltage, called the auxiliary alternating voltage and denoted as AC, is applied simultaneously to two electrodes of the ion trap. Ions in the trap resonate successively according to their mass-to-charge ratios. When a frequency notch exists in the applied AC voltage, ions with the mass-to-charge ratio corresponding to this frequency segment cannot resonate and remain trapped in the trap, while the remaining ions are ejected from the ion trap, thus achieving the mass selection function. By setting a specific AC frequency notch range, isolation of ions with specific mass-to-charge ratios, i.e., mass-selective isolation, can be achieved. Ion trap mass analysis is mainly carried out through resonance excitation technology. A radio frequency voltage (AC) is applied simultaneously to two electrodes of the ion trap. When the frequency of the AC is close to the secular frequency of an ion with a certain mass number, the ion resonates, and its motion trajectory intensifies in the direction of the endcap electrode. By selecting a specific AC voltage amplitude, the ion is ejected from the small hole on the endcap electrode and detected by a detector.

[0007] Time-of-flight mass spectrometry is a method for determining the mass-to-charge ratio by measuring the flight time of ions. Ions are accelerated by a known electric field. Ions with the same charge number have the same kinetic energy, but due to different masses, their flight times through a certain distance are different, which can be used to determine the mass-to-charge ratio of substances. After decades of continuous development, the resolution of time-of-flight mass spectrometry has been increased to tens of thousands or even hundreds of thousands, and it plays an increasingly important role in the fields of physical chemistry, biochemistry, organic chemistry, etc. [8] . Compared with other types of mass spectrometry, time-of-flight mass spectrometry has many advantages, such as a very large mass range, theoretically no limitation on the mass number of the substance to be measured, fast analysis speed, applicability to on-line detection, and relatively high sensitivity.

[0008] Mass spectrometry can only obtain the structural information of gas-phase ions, but cannot directly obtain spatial structure information. Therefore, it is very important to combine mass spectrometry with laser spectroscopy to give the structural information of mass-selected ions. Femtosecond laser is a laser with a short pulse duration but very high instantaneous power. Femtosecond laser can interact with mass-selected negative ions, causing the electrons of the negative ions to be desorbed and become neutral molecules. Then, a second femtosecond laser in the visible light band is added to make the neutral molecules become positive ions. At this time, the visible light excites coherent vibrations, and periodic oscillations will appear in the kinetic curve of the electronic spectrum, that is, the periodic oscillation of the cation intensity. Fourier transform can obtain the position of the vibration and the relevant spectrum, thereby obtaining the structural information of the neutral and ionic species. Summary of the Invention

[0009] The purpose of the present invention is to provide a multifunctional ion trap-time of flight cascade reaction mass spectrometer with fast detection speed and high sensitivity and a detection method, which combines quadrupole, ion trap and time of flight and femtosecond laser related technologies.

[0010] The ion trap-time-of-flight cascade reaction mass spectrometer provided by the present invention has a structure as shown in Figure 1 As shown, it includes: an ion source part, a cone, a quadrupole system, an ion trap system, a time-of-flight mass spectrometer system, a femtosecond laser system, and a cavity part; wherein:

[0011] The ion source part includes: an ion source block 1 of any shape, a laser 2, a target material 3, a carrier gas 4, and a fast flow tube 5; the ion source block 1 is provided with a laser channel (whose diameter is usually 0.1-5mm) and a carrier gas pipeline (whose inner diameter is usually 0.1-5mm) perpendicular to and connected to the laser channel; the target material 3 is located beside the ion source block 1, facing the laser channel; the target material 3 is driven by a motor to rotate continuously; the laser 2 bombards the target material 3 through the laser channel on the ion source block 1 (metal block); the carrier gas 4 is introduced into the carrier gas pipeline through an electromagnetic pulse valve; the outlet of the carrier gas pipeline is connected to the fast flow tube 5 (which can be a cylinder with a length of 10-150mm and an inner diameter of 0.3-6mm) through a connecting pipe; a small hole is opened in the middle of the fast flow tube 5, and a reaction gas 6 is introduced through the electromagnetic pulse valve;

[0012] The cone 7 has a hole with a diameter of 0.1-10 mm in the middle, which is in the shape of a trumpet and separates the front and middle cavities; the ion source part is located in the front cavity;

[0013] The quadrupole system 8 is arranged in the cavity behind the cone 7, and the quadrupole is used to allow the ions to pass through by mass selection; and then sent into the ion trap system;

[0014] The ion trap system comprises: an ion trap front cover 9, an ion trap rear cover 10, an ion trap electrode 11, a detector I 12, and an air intake system 13; an opening is provided in the middle of the ion trap front cover 9, the opening has an air intake connecting pipe 13, the opening is directly opposite to the quadrupole, and an opening is provided in the middle of the ion trap rear cover 11, a femtosecond laser passes through the opening into the ion trap, interacts with negative ions, and turns the negative ions into neutral molecules, and then into positive ions; it is connected to a time-of-flight mass spectrometer through a focusing mirror 16, the focusing mirror 16 has an aperture of 0.3-3 mm to isolate the middle cavity and the rear cavity, and the detector I 12 monitors the generation of positive ions;

[0015] The femtosecond laser system includes a pump laser and a probe laser. The pump laser is used to emit a pump light (pump) 14 with a wavelength of 700 - 850 nm and a pulse width of 20 - 80 fs. This pump light interacts with negative ions to desorb electrons from the negative ions. The probe laser is used to emit a probe light (probe) 15 with a wavelength of 300 - 500 nm and a pulse width of 20 - 80 fs. This probe light interacts with neutral molecules to turn the neutral molecules into positive ions. There is a time delay of 1 ps to 1 μs between the two beams of light.

[0016] The time-of-flight mass spectrometry system includes an ion extraction and acceleration region 17, a deflection plate 18, a reflection region 19, and a detector II 20. Ions have an initial velocity when entering the extraction and acceleration region, so the flight trajectory of the ions is adjusted through the extraction and acceleration region and deflection design, and they smoothly enter the reflection region.

[0017] The present invention also provides a detection method for the above ion trap - time-of-flight tandem reaction mass spectrometry device. The specific steps are as follows:

[0018] (I) Start the laser 2 to generate laser light, and control the laser energy to be 2 - 20 mJ and the frequency to be 3 - 1000 Hz. The laser bombards the target 3 through the laser channel on the ion source block 1 to generate plasma. The target 3 rotates continuously driven by a motor to improve the signal stability.

[0019] (II) Control the electromagnetic pulse valve to allow the carrier gas 4 to enter through the carrier gas pipeline. The carrier gas carries the plasma and flies into the fast flow tube 5 through a connecting tube with a smaller inner diameter. Due to the effect of supersonic expansion, it cools and forms ions.

[0020] (III) Control another electromagnetic pulse valve to allow the reaction gas to enter the fast flow tube 5 through a small hole in the middle of the fast flow tube 5. The ions enter the quadrupole system after reacting with the reaction gas.

[0021] When the ions fly out of the quadrupole, there are two working modes:

[0022] The first working mode is for negative ions. The laser operates in a high-frequency mode, the quadrupole is in the mass selection mode, the amplitude of the RF voltage on the ion trap electrodes is a constant value. After the negative ions enter and are selected for a single mass ion by the quadrupole, they enter the ion trap. Among them, the front cover 9 of the ion trap is set to a positive voltage, and the rear cover 10 of the ion trap is set to a negative voltage. After the ions pass through the ion trap, they interact with two femtosecond laser pump light beams 14 and probe light beams 15 emitted by the femtosecond laser system. After the negative ions become neutral, they turn into positive ions. Then, after passing through the focusing lens 16, the positive ions are sent to the time-of-flight mass spectrometry extraction region 17. After being accelerated by applying a high-voltage pulse dual field, they pass through the deflection region 18 and are sent to the reflection region 19, and are detected by the detector I 12 after reflection. The detector I 12 monitors the generation of positive ions. By adjusting the delay between the femtosecond laser pump light 14 and the probe light 15, a periodic oscillation kinetic curve of the positive ion signal intensity is obtained. Then, through subsequent Fourier transform, the vibration position can be obtained, and the relevant spectrum can be obtained, thereby obtaining the structural information of the neutral molecule. The first working mode mainly obtains mass spectrometry and spectral information.

[0023] The second working mode is for the reaction of positive ions / negative ions. The laser operates in a low-frequency mode, the quadrupole is in the mass selection mode. After the positive ions / negative ions enter the ion trap, the amplitude of the RF voltage on the ion trap electrodes is a constant value. The front cover 9 and the rear cover 10 of the ion trap are set to positive / negative voltages, and the ions are confined in the trap. The rear cover 9 of the ion trap becomes negative / positive voltage. Then, after passing through the focusing lens 16, the ions are sent to the time-of-flight mass spectrometry extraction region 17. After being accelerated by applying a high-voltage pulse dual field, they pass through the deflection region 18 and are sent to the reflection region 19, and are detected by the detector II 20 after reflection. The reaction gas 6 can be introduced into the fast flow tube 5 after the ions are generated, or a single mass ion can be selected by the ion trap and react with the reaction gas in the ion trap. The second working mode mainly studies the reaction of ions with neutral molecules.

[0024] In the present invention, the ion trap is any two-dimensional linear ion, three-dimensional ion trap or any other shaped ion trap mass analyzer.

[0025] Among them, the buffer gas is helium, or it can also be other noble gases or nitrogen, and the gas flow rate is 0.05 - 10 ml / min.

[0026] The reaction gas is generally a neutral gas such as methane or carbon monoxide, the gas pressure is 0.1 to 0.5 atmospheres, and the pulse width is 180 - 1000 μs.

[0027] In the present invention, the voltage and timing of the laser switch, carrier gas, two reaction gas injection electromagnetic pulse valves, the RF of the ion trap electrodes, the front and rear covers of the ion trap, and the resonance excitation circuit are controlled by the total controller.

[0028] The front, middle, and rear cavities are respectively connected to a set of mechanical pump and molecular pump systems. The mechanical pump provides a rough vacuum with a pressure of 0.1 - 10 Pa, and the molecular pump system provides a high vacuum with a pressure of 0.5 - 10×10 -4 Pa.

[0029] This device can achieve multiple functions. For some highly reactive or short-lived highly reactive species, through the first flow tube mode, the residence time of ions in the ion trap is less than 1 ms. After the reaction, they are directly sent to the time-of-flight mass spectrometer to obtain a mass spectrum. For some easily dissociable ions, the second working mode is adopted. After operations such as mass selection and reaction of the ions, they are sent to the time-of-flight mass spectrometer for detection. Description of the Drawings

[0030] Figure 1 It is a schematic structural diagram of the laser ablation ultrasonic molecular beam ion source - ion trap mass spectrometer device according to an embodiment of the present invention.

[0031] Figure 2 It is the spectrum and mass spectrum according to an embodiment of the present invention.

[0032] Figure 3 It is the mass spectrum of the ion - molecule reaction according to an embodiment of the present invention.

[0033] Reference numerals in the figure: 1 is the ion source block, 2 is the laser, 3 is the target, 4 is the carrier gas, 5 is the fast flow tube, 6 is the reaction gas, 7 is the cone, 8 is the quadrupole system, 9 is the front cover of the ion trap, 10 is the rear cover of the ion trap, 11 is the ion trap electrode, 12 is the detector I, 13 is the intake pipe for introducing buffer gas and reaction gas, 14 is the pump - probe femtosecond light, 15 is the detection femtosecond light, 16 is the focusing mirror, 17 is the extraction and acceleration region, 18 is the deflector, 19 is the reflection region, 20 is the detector II. Detailed Embodiments

[0034] The present invention will be further described below in conjunction with the drawings, but the present invention is not limited to the following embodiments only.

[0035] Embodiment 1, studying silver metal ions.

[0036] As Figure 1 shown, in the ionization stage, the laser ablates the target 3 (in this example, it is metal Ag) to generate plasma. The laser operates in a high - frequency mode, and then the carrier gas 4 is introduced through an electromagnetic pulse valve. The carrier gas is helium gas at 5 atmospheres.

[0037] Ions Ag4 ‒ are generated. The generated ions enter the quadrupole system 8 through the cone 7. The floating low voltage of the quadrupole system is 0 V. The quadrupole can allow ions to pass through by mass selection (selecting three ions with mass numbers 430, 432, and 434), and then they are sent into the ion trap.

[0038] In the first working mode, a +5V voltage is applied to the front cover 9 of the ion trap and a -5V voltage is applied to the rear cover 10 of the ion trap. The amplitude of the RF voltage of the ion trap is 300V. After the ions enter the ion trap through the holes in the front cover, they pass through the focusing lens (16) with voltages set at 0V and -5V, and are sent to the extraction region of the time-of-flight mass spectrometer. Pulse voltages of 2000V and 1750V are applied to region 17, the deflection voltage 18 is 50V, and the ions reach the reflection region 19 with voltages set at 2050V and 1780V. After reflection, they reach the detector II 20, and then a mass spectrum ( Figure 2 as shown in a) is obtained. Additionally, when the ions enter the ion trap, the femtosecond laser (pump light) 14 outputs light with a wavelength of 710nm and interacts with Ag4 ‒ to turn the ions into neutral Ag4. After 5 ps, the femtosecond laser (probe light) 15 outputs light with a wavelength of 400nm and interacts with the neutral molecules to turn them into positive ions. Then, after the positive ions pass through the focusing lens 16, pulse voltages of 2000V and 1750V are applied to the extraction region 17, the deflection voltage 18 is 50V, and the ions reach the reflection region 19 with voltages set at 2050V and 1780V. After reflection, they reach the detector II 20. The visible light excites coherent vibrations, and the resulting metal positive ions will exhibit periodic oscillations in the kinetic curve of the electronic spectrum, so that the intensity of the positive ions shows periodic oscillations. The Fourier transform gives the vibrational position spectrum (as Figure 2 shown in b).

[0039] Example 2: Study the reaction of iridium metal ions.

[0040] As Figure 1 shown, in the ionization stage, the laser sputtering of target 3 (iridium metal Ir in this example) generates a plasma, and then carrier gas 4 is introduced through an electromagnetic pulse valve. The carrier gas is helium at 5 atmospheres.

[0041] The generated ions Ir + ( Figure 3 a) enter the fast flow tube 5, and reaction gas is introduced through an electromagnetic pulse valve to react with the ions. In this case, CH4 reaction gas is introduced at 0.2 atm in the working mode ( Figure 3 b).

[0042] The generated ions enter the quadrupole system 8 through the cone 7. The quadrupole system has a floating low voltage of 0V. The quadrupole allows ions to pass through according to their mass and then sends them into the ion trap. A +5V voltage is applied to the front cover 9 of the ion trap and a -5V voltage is applied to the rear cover 10 of the ion trap. The RF voltage amplitude of the ion trap is 100V. After the ions pass through the holes in the front cover and enter the ion trap, they then pass through the focusing lens 16, with voltages set at 0V and -5V, and are sent into the extraction region of the time-of-flight mass spectrometer. A pulse voltage of 2000V and 1750V is applied to the addition region 17, the deflection voltage 18 is 50V, and they reach the reflection region 19, with voltages set at 2050V and 1780V. After reflection, they reach the detector II 20, and then a mass spectrum is obtained.

[0043] Another way to introduce the reaction gas is during the ionization stage. The laser sputters the target 3 (iridium metal Ir in this example) to generate a plasma. The laser operates in a low-frequency mode, and then the carrier gas 4 is introduced through an electromagnetic pulse valve. The carrier gas is helium at 5 atmospheres.

[0044] The generated ions Ir + enter the quadrupole system 8 through the cone 7. The quadrupole system has a floating low voltage of 0V. The quadrupole allows ions to pass through according to their mass ( Figure 3 c), and then sends them into the ion trap. The RF voltage amplitude on the ion trap electrodes is 100V. The front cover 9 and the rear cover 10 of the ion trap are set to positive voltages, and the ions are confined in the trap and react with the reaction gas. The voltage of the rear cover 10 of the ion trap becomes -10V. Then, the positive ions pass through the focusing lens 16 and are sent into the time-of-flight mass spectrometry for detection. A pulse voltage of 2000V and 1750V is applied to the extraction region of the time-of-flight mass spectrometer, the deflection voltage 18 is 50V, and they reach the reflection region 19, with voltages set at 2050V and 1780V. After reflection, they reach the detector II 20, and then a mass spectrum is obtained ( Figure 3 as shown in d).

Claims

1. An ion trap-time-of-flight tandem reaction mass spectrometry device, characterized in that Comprising: Ion source section, cone, quadrupole system, ion trap system, time-of-flight mass spectrometry system, femtosecond laser system, cavity section; wherein: The ion source section includes: an ion source block (1) of arbitrary shape, a laser (2), a target (3), a carrier gas (4), a fast flow tube (5); the ion source block (1) is provided with a laser channel and a carrier gas pipeline perpendicular to and communicating with the laser channel; the target (3) is located beside the ion source block (1), facing the laser channel; the target (3) is driven by a motor to rotate continuously; the laser (2) bombards the target (3) through the laser channel on the ion source block (1); the carrier gas (4) is introduced into the carrier gas pipeline through an electromagnetic pulse valve; the outlet of the carrier gas pipeline is connected to the fast flow tube (5) through a connecting tube; a small hole is opened in the middle of the fast flow tube (5), and a reaction gas (6) is introduced through an electromagnetic pulse valve; The cone (7) has a hole with a diameter of 0.1 - 10 mm in the middle, is in a horn shape, and separates the front and middle cavities; the ion source section is located in the front cavity; The quadrupole system (8) is arranged in the cavity behind the cone (7), and the quadrupole is used to allow ions to pass through by mass; and then sent to the ion trap system; The ion trap system includes: an ion trap front cover (9), an ion trap rear cover (10), ion trap electrodes (11), a detector I (12), an intake pipeline (13); there is an opening in the middle of the ion trap front cover (9), and the intake pipeline (13) is provided in the opening, and the opening faces the quadrupole; there is an opening in the middle of the ion trap rear cover (10), and the femtosecond laser passes through the opening into the interior of the ion trap, interacts with the negative ions, makes the negative ions become neutral molecules, and then become positive ions; it is connected to the time-of-flight mass spectrometry through a focusing lens (16), and the aperture of the focusing lens (16) is 0.3 - 3 mm to isolate the middle cavity and the rear cavity, and the detector I (12) monitors the generation of positive ions; The femtosecond laser system includes a pump laser and a probe laser; the pump laser is used to emit a pump light (14) with a wavelength of 700 - 850 nm and a pulse width of 20 - 80 fs, and this pump light interacts with the negative ions to desorb the electrons of the negative ions; the probe laser is used to emit a probe light (15) with a wavelength of 300 - 500 nm and a pulse width of 20 - 80 fs, and this probe light interacts with the neutral molecules to make the neutral molecules become positive ions; there is a delay of 1 ps to 1 μs between the two beams of light; The time-of-flight mass spectrometry system includes an ion extraction and acceleration region (17), a deflection plate (18), a reflection region (19) and a detector II (20); the ions enter the extraction and acceleration region with an initial velocity, and the ion flight trajectory is adjusted through the extraction and acceleration region and the deflection design, and then enters the reflection region.

2. The ion trap-time of flight tandem reaction mass spectrometry device according to claim 1, wherein The diameter of the laser channel on the ion source block (1) is 0.1 - 5 mm, and the inner diameter of the carrier gas pipeline is 0.1 - 5 mm; the fast flow tube (5) is a cylinder with a length of 10 - 150 mm and an inner diameter of 0.3 - 6 mm.

3. The ion trap-time-of-flight tandem reaction mass spectrometry device according to claim 1, characterized in that, The ion trap is a three-dimensional ion trap.

4. An ion trap-time of flight tandem reaction mass spectrometry detection method based on the device according to claim 1, 2 or 3, characterized in that, The specific steps are as follows: (I) Start the laser (2) to generate laser light, control the laser energy to be 2 - 20 mJ, and the frequency to be 3 - 1000 Hz; the laser bombards the target (3) through the laser channel on the ion source block (1) to generate plasma; the target (3) rotates continuously driven by a motor to improve signal stability; (II) By controlling the electromagnetic pulse valve on the carrier gas pipeline, the carrier gas (4) is introduced from the carrier gas pipeline, and the carrier gas carries the plasma and flies into the fast flow tube (5) through the connecting tube. Due to the effect of ultrasonic expansion, it cools and forms ions; (III) By controlling the electromagnetic pulse valve on the reaction gas pipeline, the reaction gas is introduced into the fast flow tube (5) through the small hole in the middle of the fast flow tube (5); the ions enter the quadrupole system after reacting with the reaction gas; When the ions fly out of the quadrupole, there are two working modes: In the first working mode, for negative ions, the laser operates in a high-frequency mode. After the ions are generated, they react with the reaction gas (6) in the fast flow tube (5). The quadrupole is in the mass selection mode, and the amplitude of the radio frequency voltage on the ion trap electrode is a constant value. After the negative ions enter the quadrupole, a single mass ion is selected to enter the ion trap; among them, the front cover (9) of the ion trap is set to a positive voltage, and the rear cover (10) of the ion trap is set to a negative voltage; after the ions pass through the ion trap, they interact with the femtosecond laser pump light (14) and probe light (15) emitted by the femtosecond laser system. After the negative ions become neutral, they become positive ions, and the detector I (12) monitors the generation of positive ions; after the positive ions pass through the focusing lens (16), they are sent into the extraction and acceleration region (17) of the time-of-flight mass spectrometer. After being accelerated by applying a high-voltage pulse dual field, they pass through the deflector (18) and are sent into the reflection region (19), and are detected by the detector II (20) after reflection; the visible light excites coherent vibrations. By adjusting the delay between the femtosecond laser pump light (14) and the probe light (15), the generated metal positive ions will show periodic oscillations in the kinetic curve of the electronic spectrum, that is, the intensity of the positive ions shows periodic oscillations, and the vibrational spectrum of the neutral molecule is obtained by Fourier transform; In the second working mode, for positive ions / negative ions, the laser operates in a low-frequency mode, and the quadrupole is in the mass selection mode. After the positive ions / negative ions enter the ion trap, the amplitude of the radio frequency voltage on the ion trap electrode is a constant value. The front cover (9) of the ion trap is set to a positive voltage / negative voltage, and the rear cover (10) of the ion trap is set to a positive voltage / negative voltage, and the ions are confined in the trap; the rear cover (10) of the ion trap becomes a negative voltage / positive voltage, and then after the ions pass through the focusing lens (16), they are sent into the extraction and acceleration region (17) of the time-of-flight mass spectrometer. After being accelerated by applying a high-voltage pulse dual field, they pass through the deflector (18) and are sent into the reflection region (19), and are detected by the detector II (20) after reflection; after the ions are generated, the reaction gas (6) is introduced into the fast flow tube (5), or a single mass ion is selected through the ion trap, and the reaction gas reacts with the ions in the ion trap.

5. The detection method according to claim 4, characterized in that The switch of the laser, the radio frequency of the ion trap electrode, the front cover of the ion trap, and the rear cover of the ion trap, their voltages and timings are controlled by the main controller.

Images