Laser ionization method of aerosol mass spectrometer, aerosol mass spectrometer

Abstract

The present application discloses a laser ionization method for an aerosol mass spectrometer and an aerosol mass spectrometer. The method includes: obtaining the flight time and pulse signal corresponding to each detected particle, and obtaining the probability that each particle is a bioluminescent particle based on the pulse signal and / or flight time; wherein the pulse signal at least includes a fluorescence pulse signal, or the pulse signal at least includes a fluorescence pulse signal and a scattered light pulse signal; using the flight time to calculate the ionization trigger time corresponding to each particle; sorting the ionization trigger time from large to small according to probability; according to the sorting, laser ionizing the target particle at the ionization trigger time of the target particle; wherein the probability of the target particle is the highest. Through the above method, the pulse utilization rate of the ionization laser can be improved, thereby improving the detection sensitivity of the aerosol mass spectrometer.

Description

Technical Field

[0001] The present application relates to the technical field of aerosol detection, and in particular to a laser ionization method of an aerosol mass spectrometer and an aerosol mass spectrometer. Background Art

[0002] Aerosol mass spectrometers are widely used in aerosol research. They analyze and identify the chemical composition of aerosol particles in real time and at high resolution, and can also measure the particle size of aerosol particles. Aerosol mass spectrometers generally use an ionizing laser as the ionization source.

[0003] The disadvantage is that the triggering frequency of the ionization laser will cause idle time between pulse lasers. During this time, the ionization laser cannot be triggered, which leads to a decrease in the detection sensitivity of the aerosol mass spectrometer to bioaerosols. Summary of the Invention

[0004] The laser ionization method of an aerosol mass spectrometer and the aerosol mass spectrometer provided in the present application can improve the pulse utilization rate of the ionization laser, thereby improving the detection sensitivity of the aerosol mass spectrometer.

[0005] In a first aspect, the present application provides a laser ionization method for an aerosol mass spectrometer, the method comprising: obtaining a flight time and a pulse signal corresponding to each detected particle, and obtaining a probability that each particle is a bioluminescent particle based on the pulse signal and / or the flight time; wherein the pulse signal at least includes a fluorescence pulse signal, or the pulse signal at least includes a fluorescence pulse signal and a scattered light pulse signal; using the flight time to calculate the ionization trigger moment corresponding to each particle; sorting the ionization trigger moments from large to small according to probability; and according to the sorting, performing laser ionization on the target particle at the ionization trigger moment of the target particle; wherein the probability of the target particle is the largest.

[0006] Among them, the probability of each particle being a bioluminescent particle is obtained based on the pulse signal and / or flight time, including: calculating the relationship between the fluorescence pulse signal and the flight time of each particle; or, calculating the relationship between the fluorescence pulse signal and the scattered light pulse signal of each particle; or, calculating the relationship between the fluorescence pulse signal, the scattered light pulse signal and the flight time of each particle; and comparing the relationship with the prior probability to obtain the probability of each particle being a bioluminescent particle.

[0007] The prior probability is obtained in the following manner: collecting a pure environmental background particle sample without bioaerosols and a pure bioaerosol particle sample; obtaining a first target flight time and a first target pulse signal of the pure environmental background particle sample; and obtaining a second target flight time and a second target pulse signal of the pure bioaerosol particle sample; and determining the prior probability based on the first target flight time, the first target pulse signal, the second target flight time, and the second target pulse signal.

[0008] Among them, the flight time includes a first flight time and a second flight time; obtaining the flight time and pulse signal corresponding to each detected particle includes: obtaining the first flight time and pulse signal corresponding to each detected particle; using the first flight time to determine the second flight time; using the flight time to calculate the ionization trigger moment corresponding to each particle, including: using the second flight time to calculate the ionization trigger moment corresponding to each particle.

[0009] Determining the second flight time using the first flight time includes: determining a flight time range for the corresponding target particle to reach the next light source using the first flight time; and determining the second flight time based on the flight time range.

[0010] In response to the fact that the pulse signal of the next light source corresponding to the target particle is not collected within the flight time range, the information of the target particle is cleared.

[0011] In which, in response to collecting the pulse signals of the next light source corresponding to multiple target particles within the flight time range, the correspondence between the particles is determined by using the difference between the collection moments corresponding to the pulse signals of the next light source of the multiple target particles and the time centers of the flight time ranges corresponding to the multiple target particles.

[0012] Among them, the target particles are sorted according to the bioluminescence trigger probability, and laser ionization is performed on the target particles at the ionization trigger moment of the target particles, including: when the ionization trigger moment of any particle is reached, it is detected whether the current particle is the target particle; if so, the current particle is laser ionized; if not, the information of the current particle is cleared from the sorting.

[0013] The laser ionization of the current particle includes: obtaining the state of the ionization laser; in response to the state being a waiting trigger state, performing laser ionization on the current particle; and in response to the state being a disabled state, clearing the information of the current particle in the sorting.

[0014] In a second aspect, the present application provides an aerosol mass spectrometer, which includes: an optical device for generating at least two light sources; an acquisition module for collecting the flight time and pulse signals of each particle passing through at least two light sources successively; and a processing module for utilizing the flight time and pulse signals to implement the method provided in the first aspect.

[0015] The optical device includes: a first optical device for generating two light sources; a second optical device for generating one light source; and a third optical device for generating ionizing laser.

[0016] The beneficial effects of the present application are as follows: different from the prior art, the laser ionization method and aerosol mass spectrometer provided by the present application use the fluorescence pulse signal of each particle to obtain the probability of each particle being a bioluminescent particle, and sort the ionization triggering time of each particle from large to small according to the probability of each particle being a bioluminescent particle; then select the particle with the highest probability as the target of laser ionization, and perform laser ionization on the particle, so that the ionization laser can more likely hit the bioaerosol particles, improve the pulse utilization rate of the ionization laser, and thus improve the detection sensitivity of the aerosol mass spectrometer. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without inventive efforts. Among them:

[0018] Figure 1 1 is a schematic structural diagram of an embodiment of an aerosol mass spectrometer provided by the present application;

[0019] Figure 2 This is a flow chart of an embodiment of a laser ionization method for an aerosol mass spectrometer provided by the present application;

[0020] Figure 3 This is a flow chart of another embodiment of the laser ionization method for an aerosol mass spectrometer provided by the present application;

[0021] Figure 4 This is a flow chart of another embodiment of the laser ionization method for an aerosol mass spectrometer provided by the present application;

[0022] Figure 5 This is a flow chart of another embodiment of the laser ionization method for an aerosol mass spectrometer provided by the present application;

[0023] Figure 6 This is a schematic diagram of the relationship between the fluorescence pulse signal and the scattered light signal provided by the present application;

[0024] Figure 7 This is a schematic diagram of the relationship between the fluorescence pulse signal and the flight time provided in this application;

[0025] Figure 8is a structural schematic diagram of another embodiment of the aerosol mass spectrometer provided by the present application;

[0026] Figure 9 is a structural schematic diagram of another embodiment of the aerosol mass spectrometer provided by the present application;

[0027] Figure 10 This is a flow chart of another embodiment of the laser ionization method for an aerosol mass spectrometer provided by the present application;

[0028] Figure 11 This is a partial structural diagram of the aerosol mass spectrometer provided in this application.

[0029] In the figure: 100, aerosol mass spectrometer; 10, optical device; 20, acquisition module; 30, processing module; 101, first optical device; 1011, first continuous laser; 1012, first lens group; 1013, wave plate; 1014, beam splitter; 102, second optical device; 1021, second continuous laser; 1022, second lens group; 103, third optical device; 1031, ionization laser; 1032, third lens group; 2, aperture; 3, spherical reflector; 4, extinction cone; 5, first convex lens; 6, dichroic mirror; 7, second convex lens; 8, scattered light acquisition unit; 9, filter; 11, third convex lens; 12, fluorescence acquisition unit. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. It will be understood that the specific embodiments described herein are only used to explain the present application, rather than to limit the present application. It should also be noted that, for ease of description, only some, rather than all, structures related to the present application are shown in the drawings. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0031] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0032] Aerosol mass spectrometers are widely used in aerosol research. They analyze and identify the chemical composition of aerosol particles in real time and at high resolution, and can also measure the particle size of aerosol particles. Aerosol mass spectrometers generally use an ionizing laser as the ionization source.

[0033] The disadvantage is that the triggering frequency of the ionization laser will cause idle time between pulses of the laser. During this time, the laser cannot be triggered, which leads to a decrease in the detection sensitivity of the aerosol mass spectrometer to bioaerosols.

[0034] Based on this, the present application proposes using the fluorescence pulse signal of each particle to determine the probability of each particle being a bioluminescent particle, sorting the ionization triggering moments of each particle from highest to lowest probability. The particle with the highest probability is then selected as the target for laser ionization, and laser ionization is performed on that particle. This increases the probability of the ionization laser striking bioaerosol particles, improves the pulse utilization rate of the ionization laser, and thereby enhances the detection sensitivity of the aerosol mass spectrometer. For details, please refer to any one of the following embodiments or any combination of these embodiments.

[0035] See Figure 1 , Figure 1 FIG1 is a schematic structural diagram of an embodiment of an aerosol mass spectrometer provided in the present application. The aerosol mass spectrometer 100 comprises: an optical device 10 , a collection module 20 and a processing module 30 .

[0036] The optical device 10 is used to generate two light sources.

[0037] The collection module 20 is used to collect the flight time and pulse signals of aerosol particles passing through at least two light sources in succession.

[0038] The processing module 30 is configured to utilize the time of flight and the pulse signal to implement a method provided in any of the following embodiments.

[0039] In some embodiments, the aerosol mass spectrometer is a single particle aerosol mass spectrometer.

[0040] In some embodiments, the optical device 10 is functionally equivalent to a first diameter measuring laser. In other embodiments, the aerosol mass spectrometer 100 further includes an ionization laser for emitting laser light to perform laser ionization on target particles.

[0041] See Figure 2 , Figure 2 1 is a flow chart of an embodiment of a laser ionization method for an aerosol mass spectrometer provided in this application. The method comprises:

[0042] Step 21: Obtain the flight time and pulse signal corresponding to each detected particle, and obtain the probability that each particle is a bioluminescent particle based on the pulse signal and / or the flight time.

[0043] In some embodiments, the pulse signal includes at least a fluorescence pulse signal.

[0044] In some embodiments, the pulse signal includes at least a fluorescence pulse signal and a scattered light pulse signal.

[0045] In some embodiments, the time of flight represents the time it takes for a particle to pass through two light sources. For example, the time of flight is determined using scattered light pulse signals generated by the particle passing through the two light sources.

[0046] In some embodiments, a dichroic mirror can be used to separate the light generated by the particles passing through two light sources into fluorescence and scattered light, thereby obtaining corresponding fluorescence pulse signals and scattered light pulse signals.

[0047] Therefore, the probability of each particle being a bioluminescent particle can be determined based on the fluorescence pulse signal of each particle. For example, the probability of a particle being a bioluminescent particle can be determined based on the signal intensity of the fluorescence pulse signal. The greater the probability of a bioluminescent particle, the greater the probability that the particle is a bioaerosol.

[0048] Step 22: Calculate the ionization triggering time corresponding to each particle using the flight time.

[0049] In some embodiments, the ionization trigger time corresponding to each particle can be estimated based on the positional relationship between the light source position and the ionization laser corresponding to the time of flight. The ionization trigger time represents the moment when the particle enters the ionization range of the ionization laser and can be ionized by the ionization laser.

[0050] Step 23: Sort the ionization triggering moments according to the probability from large to small.

[0051] In some embodiments, during the time between the time a particle's flight time is calculated and the time it enters the ionization range of the ionizing laser, multiple particles may also have corresponding flight times. In other words, corresponding ionization triggering times and corresponding bioluminescent particle probabilities can be calculated for each of these particles.

[0052] Based on this, the ionization triggering moments can be sorted from large to small according to the probability.

[0053] In some embodiments, the following is described in conjunction with Table 1:

[0054] Table 1: Sorting table

[0055]

[0056] As shown in Table 1, the probability of particle A being a bioluminescent particle is 90%, and the corresponding ionization trigger time is T2. The probability of particle B being a bioluminescent particle is 85%, and the corresponding ionization trigger time is T1. The probability of particle C being a bioluminescent particle is 80%, and the corresponding ionization trigger time is T3. T1 is earlier than T2, and T2 is earlier than T3.

[0057] Step 24: According to the order, at the ionization triggering moment of the target particle, the target particle is laser ionized; among them, the probability of the target particle is the highest.

[0058] In some embodiments, the following is described in conjunction with Table 1:

[0059] At T1, the probability of the corresponding particle B being a bioluminescent particle is 85%, which is not the highest probability. Therefore, the particle B is not ionized by laser at this time, that is, the ionization laser is not triggered.

[0060] At T2, the probability of particle A being a bioluminescent particle is 90%, which is the highest probability. At this time, the particle A is laser ionized, i.e., the ionization laser is triggered.

[0061] It can be understood that due to the large number of particles, the probability ranking is constantly updated, and particles that have passed the ionization trigger moment will be removed from Table 1 to ensure the accuracy of subsequent probability comparisons that have not reached the ionization trigger moment.

[0062] In this embodiment, the probability of each particle being a bioluminescent particle is obtained using the fluorescence pulse signal of each particle, and the ionization triggering moment of each particle is sorted from large to small according to the probability of each particle being a bioluminescent particle; then, the particle with the highest probability is selected as the target of laser ionization, and the particle is laser ionized. In this way, the ionization laser can more likely hit the bioaerosol particles, thereby improving the pulse utilization rate of the ionization laser and thus improving the detection sensitivity of the aerosol mass spectrometer.

[0063] See Figure 3 , Figure 3 1 is a flow chart of another embodiment of the laser ionization method for an aerosol mass spectrometer provided by the present application. The method comprises:

[0064] Step 41: Obtain the flight time and pulse signal corresponding to each detected particle, and calculate the relationship between the fluorescence pulse signal and the flight time of each particle.

[0065] In some embodiments, the pulse signal includes at least a fluorescence pulse signal.

[0066] In some embodiments, the pulse signal includes at least a fluorescence pulse signal and a scattered light pulse signal.

[0067] In some embodiments, the ratio between the fluorescence pulse signal and the flight time may be used as the relationship between the fluorescence pulse signal and the flight time.

[0068] Step 42: Compare the relationship and the prior probability to obtain the probability that each particle is a bioluminescent particle.

[0069] In some embodiments, the prior probability can be determined in advance. Therefore, the relationship can be compared with the prior probability to obtain the probability that each particle is a bioluminescent particle.

[0070] Step 43: Calculate the ionization triggering time corresponding to each particle using the flight time.

[0071] Step 44: Sort the ionization triggering moments according to the probability from large to small.

[0072] Step 43-Step 44 has the same or similar technical solutions as any embodiment of the present application.

[0073] Step 45: According to the order, at the ionization triggering moment of the target particle, the target particle is laser ionized; wherein the probability of the target particle is the highest.

[0074] In some embodiments, when the ionization triggering moment of any particle is reached, it is detected whether the current particle is a target particle; if so, the current particle is laser ionized; if not, the information of the current particle is cleared from the sorting.

[0075] This is explained in conjunction with Table 1: T1 is earlier than T2, and T2 is earlier than T3.

[0076] At T1, the probability of particle B being a bioluminescent particle is 85%, which is not the highest probability. Therefore, particle B is not ionized by the laser. In other words, particle B is not the target particle, and the ionization laser is not triggered. The information about particle B is cleared from the sorting process.

[0077] At time T2, the probability of particle A being a bioluminescent particle is 90%, the highest probability. At this point, particle A is laser ionized. This means that particle A is the target particle, triggering the ionization laser. After the ionization laser is triggered, the information about particle A is removed from the ranking.

[0078] In some embodiments, ionization is performed in the following manner: acquiring the state of the ionization laser; in response to the state being a waiting trigger state, performing laser ionization on the current particle; in response to the state being a disabled state, clearing information of the current particle in the sorting.

[0079] Specifically, when the ionization trigger moment for the target particle is determined, the state of the ionization laser is obtained. If the state is in the waiting state, the ionization laser can be triggered to ionize the current particle. After the excitation, the state of the ionization laser is changed from the waiting state to the disabled state. If the state is in the disabled state, the ionization laser cannot be triggered, and the information of the current particle is cleared from the sorting.

[0080] The duration of the disabled state is the idle time mentioned above. When the duration of the disabled state reaches the idle time, the state of the ionization laser can be changed from the disabled state to the waiting trigger state.

[0081] In this embodiment, the probability of each particle being a bioluminescent particle is obtained using the fluorescence pulse signal of each particle, and the ionization triggering moment of each particle is sorted from large to small according to the probability of each particle being a bioluminescent particle; then, the particle with the highest probability is selected as the target of laser ionization, and the particle is laser ionized. In this way, the ionization laser can more likely hit the bioaerosol particles, thereby improving the pulse utilization rate of the ionization laser and thus improving the detection sensitivity of the aerosol mass spectrometer.

[0082] See Figure 4 , Figure 4 1 is a flow chart of another embodiment of the laser ionization method for an aerosol mass spectrometer provided by the present application. The method comprises:

[0083] Step 51: Obtain the flight time and pulse signal corresponding to each detected particle, and calculate the relationship between the fluorescence pulse signal and the scattered light pulse signal of each particle.

[0084] In some embodiments, the pulse signal includes at least a fluorescence pulse signal.

[0085] In some embodiments, the pulse signal includes at least a fluorescence pulse signal and a scattered light pulse signal.

[0086] In some embodiments, the ratio between the fluorescence pulse signal and the scattered light pulse signal may be used as the relationship between the fluorescence pulse signal and the scattered light pulse signal.

[0087] Step 52: Compare the relationship and the prior probability to obtain the probability that each particle is a bioluminescent particle.

[0088] In some embodiments, the prior probability can be determined in advance. Therefore, the relationship can be compared with the prior probability to obtain the probability that each particle is a bioluminescent particle.

[0089] Step 53: Calculate the ionization triggering time corresponding to each particle using the flight time.

[0090] Step 54: Sort the ionization triggering moments according to the probability from large to small.

[0091] Step 55: According to the order, at the ionization triggering moment of the target particle, the target particle is laser ionized; wherein the probability of the target particle is the largest.

[0092] Steps 53 to 55 have the same or similar technical solutions as any embodiment of the present application.

[0093] In this embodiment, the probability of each particle being a bioluminescent particle is obtained using the fluorescence pulse signal of each particle, and the ionization triggering moment of each particle is sorted from large to small according to the probability of each particle being a bioluminescent particle; then, the particle with the highest probability is selected as the target of laser ionization, and the particle is laser ionized. In this way, the ionization laser can more likely hit the bioaerosol particles, thereby improving the pulse utilization rate of the ionization laser and thus improving the detection sensitivity of the aerosol mass spectrometer.

[0094] See Figure 5 , Figure 5 1 is a flow chart of another embodiment of the laser ionization method for an aerosol mass spectrometer provided by the present application. The method comprises:

[0095] Step 61: Obtain the flight time and pulse signal corresponding to each detected particle, and calculate the relationship between the fluorescence pulse signal, scattered light pulse signal and flight time of each particle.

[0096] In some embodiments, the pulse signal includes at least a fluorescence pulse signal.

[0097] In some embodiments, the pulse signal includes at least a fluorescence pulse signal and a scattered light pulse signal.

[0098] In some embodiments, the ratio among the fluorescence pulse signal, the scattered light pulse signal and the flight time may be used as the relationship among the fluorescence pulse signal, the scattered light pulse signal and the flight time.

[0099] Step 62: Compare the relationship and the prior probability to obtain the probability that each particle is a bioluminescent particle.

[0100] In some embodiments, the prior probability can be determined in advance. Therefore, the relationship can be compared with the prior probability to obtain the probability that each particle is a bioluminescent particle.

[0101] Step 63: Calculate the ionization triggering time corresponding to each particle using the flight time.

[0102] Step 64: Sort the ionization triggering moments according to the probability from large to small.

[0103] Step 65: According to the order, at the ionization triggering moment of the target particle, the target particle is laser ionized; wherein the probability of the target particle is the largest.

[0104] Steps 63 to 65 have the same or similar technical solutions as any embodiment of the present application.

[0105] In this embodiment, the probability of each particle being a bioluminescent particle is obtained using the fluorescence pulse signal of each particle, and the ionization triggering moment of each particle is sorted from large to small according to the probability of each particle being a bioluminescent particle; then, the particle with the highest probability is selected as the target of laser ionization, and the particle is laser ionized. In this way, the ionization laser can more likely hit the bioaerosol particles, thereby improving the pulse utilization rate of the ionization laser and thus improving the detection sensitivity of the aerosol mass spectrometer.

[0106] In some embodiments, the prior probability is obtained by collecting a pure environmental background particle sample without bioaerosols and a pure bioaerosol particle sample; obtaining a first target flight time and a first target pulse signal for the pure environmental background particle sample; and obtaining a second target flight time and a second target pulse signal for the pure bioaerosol particle sample; and determining the prior probability based on the first target flight time, the first target pulse signal, the second target flight time, and the second target pulse signal. The first target pulse signal includes a fluorescent pulse signal and a scattered light pulse signal collected by an optical device. The second target pulse signal includes a fluorescent pulse signal and a scattered light pulse signal collected by an optical device. The first target flight time and the second target flight time are the times when the particles pass through the first optical device 101 described below in this application.

[0107] Combine Figure 6 and Figure 7 Based on the distribution of fluorescence pulse signals, scattered light pulse signals, and particle sizes of pure environmental background particles and pure bioaerosol particles, the probability distribution of the credibility of the particles being bioaerosol particles can be calculated. P = N 生物 / ( N 环境 + N 生物 ).in N 生物 Indicates the number of pure bioaerosol particles in the intensity range of the pulse signal, N 环境 Indicates the number of pure environmental background particles in the intensity range of the pulse signal.

[0108] Table 2: Probability distribution of bioaerosols

[0109]

[0110] As shown in Table 2, this specifically means the probability that a particle is a bioaerosol when its fluorescence pulse signal and scattered light pulse signal fall within a specific intensity range. The first vertical column represents the intensity range of the fluorescence pulse signal, the last horizontal column represents the intensity range of the scattered light pulse signal, and the remaining columns represent the probability that the particle is a bioaerosol (bioluminescent particle).

[0111] See Figure 8 , Figure 8 This is a schematic diagram of the structure of another embodiment of the aerosol mass spectrometer provided in this application. The aerosol mass spectrometer 100 includes an optical device 10, an acquisition module 20, and a processing module 30. The optical device 10 includes a first optical device 101, a second optical device 102, and a third optical device 103. The first optical device 101 is used to generate two light beams. The second optical device 102 is used to generate one light beam. The third optical device 103 is used to generate an ionizing laser.

[0112] The collection module 20 is used to collect the flight time and pulse signals of aerosol particles passing through at least two light sources in succession.

[0113] The processing module 30 is configured to utilize the time of flight and the pulse signal to implement the method provided in any embodiment of the present application.

[0114] In some embodiments, functionally, the first optical device 101 is equivalent to a first caliper laser, the second optical device 102 is equivalent to a second caliper laser, and the third optical device 103 is equivalent to an ionization laser.

[0115] In some embodiments, as Figure 9 As shown, the first optical device 101 has a first continuous laser 1011. The laser light emitted by the first continuous laser 1011 passes through a first lens group 1012 and a wave plate 1013 and is transmitted to a beam splitter 1014. The beam splitter 1014 splits the laser light into two beams, and a first time-of-flight is calculated using the two beams. The second optical device 102 has a second continuous laser 1021. The laser light emitted by the second continuous laser 1021 passes through a second lens group 1022. The second time-of-flight can be calculated using the laser light emitted by the second optical device 102 and the second laser light in the first optical device 101. The third optical device 103 has an ionization laser 1031 and a third lens group 1032. The ionization laser light emitted by the ionization laser 1031 passes through the lens group and is irradiated to a predetermined position. The ionization trigger time corresponding to each particle can be calculated based on the distance between the third optical device 103 and the second optical device 102.

[0116] See Figure 10 , Figure 101 is a flow chart of another embodiment of the laser ionization method for an aerosol mass spectrometer provided by the present application. The method comprises:

[0117] Step 111: Obtain a first time of flight and a pulse signal corresponding to each detected particle, and obtain a probability that each particle is a bioluminescent particle based on the pulse signal and / or the first time of flight.

[0118] In some embodiments, the pulse signal includes at least a fluorescence pulse signal.

[0119] In some embodiments, the pulse signal includes at least a fluorescence pulse signal and a scattered light pulse signal.

[0120] In some embodiments, the first flight time represents the duration of time that the particle passes through the two light sources generated by the first optical device 101. For example, the first flight time is determined using scattered light pulse signals generated by the particle passing through the two light sources.

[0121] In some embodiments, a dichroic mirror can be used to separate the light generated by the particles passing through two light sources into fluorescence and scattered light, thereby obtaining corresponding fluorescence pulse signals and scattered light pulse signals.

[0122] Therefore, the probability of each particle being a bioluminescent particle can be obtained based on the fluorescence pulse signal of each particle. For example, the probability of the particle being a bioluminescent particle can be determined based on the signal intensity of the fluorescence pulse signal.

[0123] In some embodiments, the relationship between the fluorescence pulse signal and the first flight time of each particle can be calculated, and the relationship can be compared with the prior probability to obtain the probability that each particle is a bioluminescent particle.

[0124] In some embodiments, the relationship between the fluorescence pulse signal and the scattered light pulse signal of each particle can be calculated, and the relationship can be compared with the prior probability to obtain the probability that each particle is a bioluminescent particle.

[0125] In some embodiments, the relationship between the fluorescence pulse signal, scattered light pulse signal and first flight time of each particle can be calculated, and the relationship can be compared with the prior probability to obtain the probability that each particle is a bioluminescent particle.

[0126] Step 112: Determine a second flight time using the first flight time.

[0127] The second flight time represents the time it takes for the particle to reach the second optical device from the first optical device.

[0128] In some embodiments, the first time-of-flight is used to determine a flight time range for a corresponding target particle to reach a next light source. Based on the flight time range, a second time-of-flight is determined in response to a pulse signal corresponding to the next light source being collected within the flight time range. The next light source is a beam of light generated by the second optical device.

[0129] In response to not collecting a pulse signal corresponding to the next light source of the target particle within the time-of-flight range, the target particle information is cleared. Failure to collect a pulse signal corresponding to the next light source of the target particle within the time-of-flight range indicates that the pulse signal of the target particle may be lost, and therefore, the target particle information can be cleared.

[0130] In response to collecting pulse signals corresponding to the next light source for multiple target particles within the time-of-flight range, the corresponding relationship between the particles is determined using the pulse signals of the previous light source for the multiple target particles. In the case of high particle concentrations, the time-of-flight ranges of the multiple particles reaching the second optical device may exhibit aliasing. The particles passing through the first optical device can be matched by comparing the time difference between the center position of the time-of-flight range generated by the multiple particles and the pulse signal (scattered light pulse signal) actually generated when reaching the next light source, generally minimizing the time difference. For example, the corresponding relationship between the particles can be determined by using the difference between the time centers of the time-of-flight ranges corresponding to the multiple target particles at the time of collection corresponding to the pulse signal of the next light source. The time-of-flight ranges of two particles reaching the second optical device 102 may exhibit aliasing. The particles passing through the first optical device 101 can be matched by minimizing the difference between the time centers of the corresponding time-of-flight ranges calculated for the two particles. For example, particles A and B correspond to pulse signals a1 and b1 passing through the first optical device, while particles A and B correspond to pulse signals a2 and b2 passing through the second optical device. However, it is currently unknown whether pulse signal a1 corresponds to pulse signal a2 or pulse signal b2, and whether pulse signal b1 corresponds to pulse signal a2 or pulse signal b2. Therefore, it is possible to obtain the flight time ranges corresponding to particle A and particle B. For example, the flight time range corresponding to particle A is range F1, and the flight time range corresponding to particle B is range F2. Then calculate the first time center corresponding to range F1 and the second time center corresponding to range F2. Then calculate the first difference between the acquisition time of pulse signal a2 and the first time center, and calculate the second difference between the acquisition time of pulse signal b2 and the first time center. If the first difference is less than the second difference, then pulse signal a2 corresponds to pulse signal a1, and pulse signal b2 corresponds to pulse signal b1. If the first difference is greater than the second difference, then pulse signal a2 corresponds to pulse signal b1, and pulse signal b2 corresponds to pulse signal a1.

[0131] The above are just two examples, and three or more can be determined in this way.

[0132] In another embodiment, the pulse signals of multiple target particles at the previous light source and the pulse signals of multiple target particles at the next light source can be used to calculate the corresponding undetermined flight times between particles passing through the previous light source and the next light source. The corresponding relationship between the particles can be determined using the difference between the time centers corresponding to the undetermined flight times. For example, the flight time ranges of particles A and B reaching the second optical device 102 are aliased. Therefore, when two pulse signals are detected at the second optical device 102, it is impossible to distinguish the corresponding relationship between these two pulse signals and particles A and B. Therefore, four undetermined flight times are calculated separately.

[0133] For example, particles A and B correspond to pulse signals a1 and b1 through the first optical device, and particles A and B correspond to pulse signals a2 and b2 through the second optical device. However, it is currently unknown whether pulse signal a1 corresponds to pulse signal a2 or pulse signal b2, and it is also unknown whether pulse signal b1 corresponds to pulse signal a2 or pulse signal b2. Therefore, the first to-be-determined time-of-flight can be calculated using pulse signals a1 and a2, the second to-be-determined time-of-flight can be calculated using pulse signals a1 and b2, the third to-be-determined time-of-flight can be calculated using pulse signals b1 and a2, and the fourth to-be-determined time-of-flight can be calculated using pulse signals b1 and b2.

[0134] Then, the first flight time to be determined and the third flight time to be determined are grouped together to calculate the difference between the flight time centers of the first flight time to be determined and the third flight time to be determined. The second flight time to be determined and the fourth flight time to be determined are grouped together to calculate the difference between the flight time centers of the second flight time to be determined and the fourth flight time to be determined.

[0135] By comparing the differences, a set of actual flight times is determined, and then the corresponding pulse signals and particles are associated with each other. For example, the set of flight times with the smallest difference is determined as the actual flight time, and then the corresponding pulse signals and particles are associated with each other.

[0136] Step 113: Calculate the ionization triggering time corresponding to each particle using the second flight time.

[0137] Once the scattered light signal from the particle reaching the second optical device matches the scattered light signal from the first optical device, the particle's second time of flight can be calculated. The ionization trigger time is then calculated based on the ratio of the second time of flight to the ionization trigger time, which is then stored in memory. This ratio is typically calculated based on the ratio of the distance between the first and second optical devices, and the distance between the second optical device and the ionization laser. This ratio also takes into account the delay time required for active pumping of the ionization laser. Generally, the ionization trigger time is calculated as k*second time of flight - delay.

[0138] Step 114: Sort the ionization triggering moments according to the probability from large to small.

[0139] Step 115: According to the order, at the ionization triggering moment of the target particle, the target particle is laser ionized; wherein the probability of the target particle is the largest.

[0140] In some embodiments, when the ionization triggering moment of any particle is reached, it is detected whether the current particle is a target particle; if so, the current particle is laser ionized; if not, the information of the current particle is cleared from the sorting.

[0141] This is explained in conjunction with Table 1: T1 is earlier than T2, and T2 is earlier than T3.

[0142] At T1, the probability of particle B being a bioluminescent particle is 85%, which is not the highest probability. Therefore, particle B is not ionized by the laser. In other words, particle B is not the target particle, and the ionization laser is not triggered. The information about particle B is cleared from the sorting process.

[0143] At time T2, the probability of particle A being a bioluminescent particle is 90%, the highest probability. At this point, particle A is laser ionized. This means that particle A is the target particle, triggering the ionization laser. After the ionization laser is triggered, the information about particle A is removed from the ranking.

[0144] In some embodiments, ionization is performed in the following manner: acquiring the state of the ionization laser; in response to the state being a waiting trigger state, performing laser ionization on the current particle; in response to the state being a disabled state, clearing information of the current particle in the sorting.

[0145] Specifically, when the ionization trigger moment for the target particle is determined, the state of the ionization laser is obtained. If the state is in the waiting state, the ionization laser can be triggered to ionize the current particle. After the excitation, the state of the ionization laser is changed from the waiting state to the disabled state. If the state is in the disabled state, the ionization laser cannot be triggered, and the information of the current particle is cleared from the sorting.

[0146] The duration of the disabled state is the idle time mentioned above. When the duration of the disabled state reaches the idle time, the state of the ionization laser can be changed from the disabled state to the waiting trigger state.

[0147] In this embodiment, the probability of each particle being a bioluminescent particle is obtained using the fluorescence pulse signal of each particle, and the ionization triggering moment of each particle is sorted from large to small according to the probability of each particle being a bioluminescent particle; then, the particle with the highest probability is selected as the target of laser ionization, and the particle is laser ionized. In this way, the ionization laser can more likely hit the bioaerosol particles, thereby improving the pulse utilization rate of the ionization laser and thus improving the detection sensitivity of the aerosol mass spectrometer.

[0148] In one application scenario, sampled air passes through an aerodynamic lens and enters the aerosol mass spectrometer 100. Based on the structure of the aerosol mass spectrometer 100, the air passes through the dual laser beams of the first optical device 101, generating a first time-of-flight (TFL), a scattered light pulse signal, and a fluorescence pulse signal. The relationship between the particle scattered light pulse signal (or the first TFL) and the fluorescence intensity is calculated and compared with the prior probability to determine the probability that the particle is a bioluminescent particle. This probability is then stored in the bioluminescence probability space.

[0149] The time it takes for a particle to reach the second optical device 102 can be calculated based on the first time-of-flight. Based on a preset calculation error, the time range from the first optical device 101 to the second optical device 102 can be determined and stored in the memory corresponding to the second time-of-flight. When a particle reaches the second optical device 102, the scattered light pulse signal at that location is calculated against the corresponding scattered light pulse signal from the first optical device 101 to obtain an accurate second time-of-flight. This second time-of-flight can then be used to calculate the ionization trigger moment for the particle. During this process, due to the divergence of aerosols (particles) by the aerodynamic lens, the scattered light pulse signal from the particle may be lost. In this case, the data for that particle is discarded, and the next particle is awaited until it reaches the second optical device 102.

[0150] The timing algorithm uses a countdown method. After reaching the first optical device 101, the particle's flight time range for reaching the second optical device 102 is calculated and counted down. When the time reaches 0, it indicates that the particle has entered the range of the second optical device 102. The scattered light pulse signal generated by the second optical device 102 within the detection range is measured and correlated with the particle's scattered light pulse signal from the first optical device 101 to calculate the particle's precise second flight time. Because this process runs in parallel, the time ranges of multiple particles are generally accumulated and stored in the memory of the timing control card. All particles are then checked to see if they have reached the second optical device 102.

[0151] The above method has the beneficial effect of utilizing parallel computing. If scattered light pulse signals are lost due to aerosol (particle) dispersion caused by the aerodynamic lens, the data for that particle can be discarded without affecting the calculation of other particles. Furthermore, in the case of high particle concentrations, the flight time ranges of two particles reaching the second optical device 102 may be aliased. By minimizing the difference in the calculated flight time centers of the two particles, the particle passing through the first optical device 101 can be matched.

[0152] When the scattered light pulse signal from the particle reaching the second optical device 102 matches the scattered light pulse signal reaching the first optical device 101, the particle's second time of flight can be calculated. Based on the ratio of the second time of flight to the ionization trigger time, the ionization trigger time is calculated and stored in memory. The ratio of the second time of flight to the ionization trigger time is generally calculated based on the ratio of the distance between the first and second optical devices, and the distance between the second optical device and the ionization laser. This ratio also takes into account the delay time required for active pumping of the ionization laser. Generally, the ionization trigger time = k * second time of flight - delay.

[0153] Compared to the first-come, first-served triggering method used in related technologies, where the ionization trigger time is calculated for a particular particle, then the ionization laser is triggered after the ionization trigger time has elapsed. However, due to the low frequency of the ionization laser, a longer wait is required before the next particle is ionized. The present invention selects the particle with the highest probability of being struck based on the distribution relationship between the particle's fluorescence pulse signal and scattered light pulse signal, as well as the fluorescence pulse signal and the first flight time, during the time the particle travels from the first optical device to the third optical device (ionization laser), thereby improving the detection sensitivity of bioaerosols.

[0154] Specifically, after calculating the bioluminescent particle probability of a particle, it is stored in memory and associated with the particle's time of flight. During the time between the first optical device 101 and the position of the third optical device (ionizing laser), multiple particles may pass through the first optical device 101, generating multiple bioluminescent particle probabilities and particle flight times. At this point, the bioluminescent particle probabilities are sorted, the ionizing laser is triggered at a time corresponding to the bioluminescent particle probability, and the particle is ionized. The particle then enters the mass analyzer for chemical composition analysis, accurately determining whether it is a bioaerosol particle.

[0155] More specifically, after calculating the ionization trigger time for each particle, a countdown method is used to wait for the particle to reach the ionization trigger position. Only particles with the highest probability of biofluorescence will be triggered by the ionization laser. However, the premise for determining whether the ionization laser has been triggered is that the laser is in a state of waiting for triggering. If the countdown time for a particle reaches zero, that is, the particle has reached the ionization laser position, the ionization laser will not be triggered, because the ionization laser is not in a state of waiting for triggering, or the particle with the highest probability of biofluorescence is not, and its data record will be released from memory.

[0156] Because the time it takes for particles to travel from the first optical device 101 to the third optical device 103 is shorter than the idle time caused by the laser frequency of the third optical device 103, under normal circumstances, the time it takes for particles to travel from the first optical device 101 to the third optical device 103 is much shorter than the idle time caused by the laser frequency of the third optical device 103. Therefore, targeting particles most likely to be bioluminescent particles within this time range can more fully utilize the number of ionization laser pulses, thereby increasing the detection rate and sensitivity of bioaerosols per unit time.

[0157] In some embodiments, the first optical device 101 is further configured with a corresponding collection unit and an optical path transmission device. Figure 11 As shown, in the optical path direction of the first optical device 101, an aperture 2, a spherical reflector 3, a first convex lens 5, a dichroic mirror 6, a second convex lens 7, a filter 9, a third convex lens 11, an extinction cone 4, a scattered light collection unit 8, and a fluorescence collection unit 12 are provided. The light source of the first optical device 101 is incident on the extinction cone 4 through the aperture 2. When particles pass through the light source, they are scattered, generating corresponding scattered light and fluorescence. At this time, the scattered light and fluorescence are incident on the first convex lens 5 through the spherical reflector 3, and then incident on the dichroic mirror 6 from the first convex lens 5, and the scattered light and fluorescence are separated by the dichroic mirror 6. The scattered light is incident on the scattered light collection unit 8 through the second convex lens 7, and a corresponding scattered light pulse signal is obtained. The fluorescence is incident on the fluorescence collection unit 12 through the third convex lens, and a corresponding fluorescence pulse signal is obtained.

[0158] In summary, the laser ionization method and aerosol mass spectrometer provided by the present application use the fluorescence pulse signal of each particle to obtain the probability of each particle being a bioluminescent particle, and sort the ionization trigger time of each particle from large to small according to the probability of each particle being a bioluminescent particle; then select the particle with the highest probability as the target of laser ionization, and perform laser ionization on the particle, so that the ionization laser can more likely hit the bioaerosol particles, improve the pulse utilization rate of the ionization laser, and thus improve the detection sensitivity of the aerosol mass spectrometer.

[0159] In the several embodiments provided in this application, it should be understood that the disclosed methods and devices can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the modules or units is merely a logical functional division. In actual implementation, other division methods may be used, such as combining or integrating multiple units or components into another system, or ignoring or not implementing certain features.

[0160] If the integrated units in the other embodiments described above are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) or a processor to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes various media that can store program code, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0161] The above description is only an implementation method of the present application and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the description and drawings of this application, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A laser ionization method for an aerosol mass spectrometer, characterized in that: The method comprises: Obtaining a time-of-flight and a pulse signal corresponding to each detected particle, wherein the pulse signal includes at least a fluorescence pulse signal, calculating a relationship between the fluorescence pulse signal and the time-of-flight for each particle, and comparing the relationship with a priori probability to obtain a probability that each particle is a bioluminescent particle; Calculating the ionization triggering time corresponding to each particle using the flight time; sorting the ionization triggering moments according to the probabilities from largest to smallest; According to the ranking, at the ionization triggering moment of the target particle, the target particle is laser ionized; wherein the probability of the target particle is the largest; the prior probability is obtained by the following method: Collect pure environmental background particle samples without bioaerosols and pure bioaerosol particle samples; Acquiring a first target flight time and a first target pulse signal of the pure environmental background particle sample; and acquiring a second target flight time and a second target pulse signal of the pure bioaerosol particle sample; The prior probability is determined according to the first target flight time, the first target pulse signal, the second target flight time, and the second target pulse signal.

2. The method according to claim 1, characterized in that The flight time includes a first flight time and a second flight time; and obtaining the flight time and pulse signal corresponding to each detected particle includes: Acquire the first flight time and the pulse signal corresponding to each detected particle; determining the second flight time using the first flight time; The step of calculating the ionization triggering time corresponding to each particle by using the flight time includes: The second flight time is used to calculate the ionization triggering time corresponding to each particle.

3. The method according to claim 2, characterized in that The determining the second flight time by using the first flight time includes: Determining a flight time range for a corresponding target particle to reach a next light source using the first flight time; The second flight time is determined based on the flight time range.

4. The method according to claim 3, characterized in that In response to not collecting the pulse signal of the target particle corresponding to the next light source within the flight time range, the information of the target particle is cleared.

5. The method according to claim 3, characterized in that In response to collecting the pulse signals of the next light source corresponding to multiple target particles within the flight time range, the correspondence between the particles is determined by using the difference between the collection moments corresponding to the pulse signals of the next light source of the multiple target particles and the time centers of the flight time ranges corresponding to the multiple target particles.

6. The method according to claim 1, characterized in that The step of performing laser ionization on the target particles according to the sequence at the ionization triggering moment of the target particles comprises: When the ionization triggering moment of any particle is reached, detecting whether the current particle is the target particle; If so, performing laser ionization on the current particle; If not, the information of the current particle is cleared from the sorting.

7. The method according to claim 6, characterized in that The laser ionization of the current particle comprises: Get the status of the ionization laser; In response to the state being a wait-for-trigger state, performing laser ionization on the current particle; In response to the state being the disabled state, clearing the information of the current particle in the sorting.

8. An aerosol mass spectrometer, characterized in that The aerosol mass spectrometer comprises: An optical device for generating at least two light sources; A collection module, used for collecting the flight time and pulse signal of each particle passing through the at least two light sources successively; A processing module is configured to utilize the flight time and the pulse signal to implement the method according to any one of claims 1 to 7.

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