An open mass spectrometry imaging method based on laser desorption assisted carbon fiber ionization

Abstract

The present invention discloses an open mass spectrometry imaging method based on laser desorption assisted carbon fiber ionization, which first desorbs the sample to be tested by emitting laser light from a laser, and then ionizes the desorbed sample to be tested by applying voltage to the carbon fiber with the assistance of an auxiliary solvent or a derivatization reagent, and finally allows the generated sample ions to enter the mass spectrometer from the injection port of the mass spectrometer, and mass spectrometry analysis and imaging are performed by the mass spectrometer. The open mass spectrometry imaging method based on laser desorption assisted carbon fiber ionization provided by the present invention has the advantages of high spatial resolution, wide range of applicable solvents, applicable to the detection of polar and non-polar compounds and thermally unstable compounds, and can realize open mass spectrometry online derivatization imaging.

Description

Technical Field

[0001] The invention relates to an open mass spectrometry imaging method based on laser desorption assisted carbon fiber ionization, and belongs to the technical field of mass spectrometry analysis. Background Art

[0002] Mass spectrometry imaging (MSI) can conduct non-targeted spatial distribution studies on the surfaces of various physical samples and is a powerful tool in the field of mass spectrometry analysis technology. In a single experiment, mass spectrometry imaging can simultaneously image thousands of molecules (such as lipids, neurotransmitters, peptides, proteins, etc.) without any additional labeling. It combines the chemical information obtained from the mass spectrometer with the spatial distribution information on the sample surface, making mass spectrometry imaging one of the indispensable analytical techniques for characterizing biological samples. As one of the important components of mass spectrometry and mass spectrometry imaging instruments, the ion source has always been a hot topic in the field of mass spectrometry analysis. With the continuous development and improvement of various ion source technologies, the range and types of samples that can be detected by mass spectrometry imaging are also expanding, which has greatly expanded the scope of application of mass spectrometry instruments.

[0003] At present, for mass spectrometry imaging, the commonly used ion source technologies mainly include matrix-assisted laser desorption / ionization (MALDI), desorption electrospray ionization (DESI) and secondary ion mass spectrometry (SIMS). Among them, both MALDI and SIMS need to complete sample detection under high vacuum conditions, and MALDI needs to coat an additional layer of matrix on the surface of the analyte to desorb molecules on the sample surface, and for compounds of different molecular weights, different matrices need to be selected for detection. In addition, the uniformity, thickness, and size of the matrix layer will affect the response of the compound in the mass spectrum and the spatial resolution of the MSI image to a certain extent. Therefore, the sample pretreatment process of MALDI-MSI is more complicated than other mass spectrometry imaging ion sources. SIMS-MSI uses a single atomic or polyatomic ion beam to bombard the sample surface, causing the desorption / ionization of secondary ions on the sample surface. Using a single-atom ion beam, a spatial resolution as low as 50 nm can be achieved, but only elemental ions and very few organic fragments can be detected, so the use of SIMS-MSI has major limitations when analyzing biological samples.

[0004] Ambient mass spectrometry imaging (AMSI) was first proposed by the Cooks research group in 2004. It is popular because it does not require sample pretreatment and can perform in-situ real-time visual analysis of biological samples under atmospheric pressure. It has become an effective analytical tool in various fields such as forensics, metabolomics, disease diagnosis, and drug evaluation. At present, in the field of AMSI, ion sources are mainly divided into the following three categories: first, ion sources that directly desorb / ionize samples; second, ion sources that first desorb and then ionize samples; third, ion sources that extract and ionize samples.

[0005] Among them, the first and third AMSI ion sources are basically based on the ESI principle (polar solvent is introduced into a capillary with a high voltage of 2-4kV at the end, and an aerosol spray is generated under the action of high voltage and auxiliary nebulizing gas, thereby promoting the generation of charged droplets) of soft ionization mass spectrometry imaging ion source technology. In these technologies, the charged droplet spray is used to impact the sample surface to desorb analytes and generate molecular ions through the ESI mechanism. Therefore, they all have the defects of ESI: they only have good compatibility and responsiveness to polar molecules, while some non-polar compounds cannot be detected using this type of ion source. On the other hand, since AMSI ion sources based on the ESI principle, such as DESI, use nebulizing gas, this makes the contact area between the charged spray and the sample surface larger than the diameter of the capillary tip, resulting in an excessively large spatial resolution of the MSI image. Generally speaking, the spatial resolution of the MSI image of the first type of ion source (direct desorption / ionization sample) usually reaches about 200μm. As mass spectrometry analysis develops towards micro-amount and trace detection, the third ion source represented by nanoDESI (extracting samples and ionizing) can extract and analyze samples without auxiliary atomizing gas, and its extraction tip can often reach 10μm, which provides the possibility of improving spatial resolution. However, the amount of sample that can be extracted by a too fine tip is also extremely low. When using this type of ion source, how to improve the response of the analyte in the mass spectrometer is another difficult problem.

[0006] The second type of ion source (desorbing first and then ionizing the sample) often uses ultraviolet, infrared lasers or thermal assistance to first desorb the analyte from the sample, and then connects to various ion sources for ionization. For example, the use of laser combined with real-time direct analysis ion source (DART), atmospheric pressure chemical ionization ion (APCI) source, etc., can achieve simultaneous analysis of polar and non-polar compounds. In addition, since the laser spot and laser position can be automatically adjusted, high spatial resolution MSI images can be produced. However, ion sources based on corona discharge mechanism such as DART and APCI require higher temperatures for ionization, APCI (350°C), DART (≥250°C), so it is difficult to detect some thermally unstable compounds. Summary of the invention

[0007] In view of the above-mentioned problems existing in the prior art, the object of the present invention is to provide an open mass spectrometry imaging method based on laser desorption assisted carbon fiber ionization, which has high spatial resolution, is applicable to a wide range of solvents, can be applied to the detection of polar and non-polar compounds and thermally unstable compounds, and can realize open mass spectrometry online derivatization imaging.

[0008] In order to achieve the above-mentioned invention object, the present invention adopts the following technical scheme:

[0009] An open mass spectrometry imaging method based on laser desorption assisted carbon fiber ionization is to first desorb the sample by emitting laser light from a laser, then ionize the desorbed sample by applying voltage to the carbon fiber with the assistance of an auxiliary solvent or a derivatization reagent, and finally allow the generated sample ions to enter the mass spectrometer from the injection port of the mass spectrometer, and perform mass spectrometry analysis and imaging through the mass spectrometer.

[0010] In one embodiment, the open mass spectrometry imaging method based on laser desorption assisted carbon fiber ionization comprises the following steps:

[0011] a) placing the sample to be tested between the laser, the sampling and ionization end of the carbon fiber and the injection port of the mass spectrometer, wherein the outer sleeve of the carbon fiber is provided with a capillary, the sampling and ionization end of the carbon fiber passes through the outlet end of the capillary and is located in front of the injection port of the mass spectrometer, and the inlet end of the capillary is connected to a solvent / reagent channel for introducing an auxiliary solvent or a derivatization reagent;

[0012] b) emitting laser light to hit the sample to be tested, so as to desorb the sample to be tested;

[0013] c) introducing an auxiliary solvent or a derivatization reagent into the sampling and ionization end of the carbon fiber through a solvent / reagent channel;

[0014] d) turning on a high-voltage power supply, applying voltage to the carbon fiber through the high-voltage power supply, and the unattached sample to be tested is collected and ionized by the sampling and ionization end of the carbon fiber 2 to generate sample ions;

[0015] e) The generated sample ions enter the mass spectrometer from the injection port of the mass spectrometer, and are subjected to mass spectrometry analysis and imaging by the mass spectrometer.

[0016] In one embodiment, the high voltage power source is connected to the carbon fiber through a conductive metal foil.

[0017] In a preferred embodiment, the voltage of the high voltage power supply is 1-3 kV.

[0018] In a preferred embodiment, the laser is located above the sample to be tested, preferably directly above it.

[0019] In a preferred embodiment, the angle between the laser line emitted by the laser and the surface of the sample to be measured is 45 to 90 degrees, preferably 90 degrees.

[0020] In a preferred embodiment, the distance between the emission end of the laser and the surface of the sample to be measured is 10 to 15 centimeters.

[0021] In a preferred embodiment, the diameter of the sampling and ionization end of the carbon fiber is 1 to 20 microns.

[0022] In a preferred embodiment, the angle between the axis of the carbon fiber and the laser line emitted by the laser is 30 to 45 degrees, preferably 45 degrees.

[0023] In a preferred embodiment, the distance between the sampling and ionization end of the carbon fiber and the surface of the sample to be tested is 1 to 5 mm, preferably 2 mm.

[0024] In one embodiment, the auxiliary solvent is a polar or non-polar organic solvent, including but not limited to methanol, dichloromethane, acetonitrile and toluene, and the derivatization reagent refers to a derivatization reagent that can react with specific chemical groups, including but not limited to hydroxyl groups, carboxyl groups, carbon-carbon double bonds, and amino groups.

[0025] In one embodiment, the solvent / reagent channel is a peek tube, a two-way is connected between the outlet end of the peek tube and the inlet end of the capillary tube, and the inlet end of the peek tube is connected to an injection needle.

[0026] In a preferred embodiment, the flow rate of the auxiliary solvent or derivatization reagent in the solvent / reagent channel is 1 to 5 μl / min, preferably 4 μl / min.

[0027] In a preferred embodiment, the injection needle is installed on a peristaltic pump.

[0028] In one embodiment, the sample to be tested is placed on top of a sample carrier, and the sample carrier is located between the sampling and ionization end of the carbon fiber and the injection port of the mass spectrometer.

[0029] In a preferred embodiment, the sample carrier is placed on top of a two-dimensional moving platform.

[0030] In one embodiment, the sample inlet of the mass spectrometer is connected to an ion transfer tube, and the inlet end of the ion transfer tube is located near the sample to be tested.

[0031] In a preferred embodiment, the distance between the inlet end of the ion transfer tube and the surface of the sample to be tested is 1 to 5 mm, preferably 2 mm.

[0032] In a preferred embodiment, the angle between the axis of the inlet end of the ion transfer tube and the laser line emitted by the laser is 30 to 45 degrees, preferably 45 degrees.

[0033] Compared with the prior art, the beneficial technical effects of the present invention are:

[0034] 1. The open mass spectrometry imaging method based on laser desorption assisted carbon fiber ionization provided by the present invention has higher spatial resolution than DESI technology; good solvent compatibility, and is compatible with polar and non-polar solvents (DESI is only compatible with polar solvents); strong ionization ability, a wide range of ionizable molecules, and is compatible with polar and non-polar compounds; no auxiliary gas is required during analysis and imaging, and the cost is low and the operation is simple;

[0035] 2. The open mass spectrometry imaging method based on laser desorption assisted carbon fiber ionization provided by the present invention, compared with the Nano-ESI technology, uses laser-assisted desorption of samples, which can effectively improve the response of compounds in mass spectrometry; the compatible solvent and reagent flow rate range is wider, up to 1 to 5 microliters / minute;

[0036] 3. The open mass spectrometry imaging method based on laser desorption assisted carbon fiber ionization provided by the present invention can support continuous injection, stable signal, wider detectable molecular weight range, and support online derivatization imaging on tissues compared with DART, APCI and DBDI technologies; it does not require the use of high-temperature ionized samples, can obtain more complete mass information of analytes, and is compatible with thermally unstable compounds;

[0037] 4. The open mass spectrometry imaging method based on laser desorption assisted carbon fiber ionization provided by the present invention can use a common mass spectrometer such as a triple quadrupole mass spectrometer, a time-of-flight mass spectrometer, an ion trap mass spectrometer, and Fourier transform ion cyclotron resonance, and has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1The present invention is a schematic diagram of a device structure for realizing the open mass spectrometry imaging method based on laser desorption assisted carbon fiber ionization according to the present invention;

[0039] Figure 2 This is the primary mass spectrum in positive ion mode obtained by direct mass spectrometry imaging using methanol as the carbon fiber auxiliary solvent in Example 1;

[0040] Figure 3 This is a positive ion mode mass spectrometry imaging diagram obtained by direct mass spectrometry imaging using methanol as a carbon fiber auxiliary solvent in Example 1;

[0041] Figure 4 This is a positive ion mode primary mass spectrum obtained by using a derivatization reagent (pyridine / deuterated pyridine in dichloromethane solution) to pass through carbon fiber to perform online derivatization mass spectrometry imaging on the tissue in Example 2;

[0042] Figure 5 This is a positive ion mode mass spectrometry imaging diagram obtained by using a derivatization reagent (pyridine / deuterated pyridine in dichloromethane solution) to pass through carbon fiber for online derivatization mass spectrometry imaging on tissue in Example 2; in the figure: A. derivatization product peaks of pyridine and deuterated pyridine: m / z 702.7457 and m / z 707.7709; B. derivatization product peaks of pyridine and deuterated pyridine: m / z 628.7310 and m / z 631.7617; C. derivatization product peaks of pyridine and deuterated pyridine: m / z 710.7437 and m / z 715.7776; D. derivatization product peaks of pyridine and deuterated pyridine: m / z 710.7332 and m / z 715.7626;

[0043] The numbers in the figure are as follows: 1. Laser; 2. Carbon fiber; 3. Sample to be tested; 4. High voltage power supply; 5. Capillary; 6. Inlet of mass spectrometer; 7. Solvent / reagent channel; 8. Two-way; 9. Injection needle; 10. Peristaltic pump; 11. Sample carrier; 12. Two-dimensional moving platform; 13. Ion transfer tube; α1, the angle between the laser line emitted by the laser and the surface of the sample to be tested; α2, the angle between the axis of the carbon fiber and the laser line emitted by the laser; α3, the angle between the axis of the inlet end of the ion transfer tube and the laser line emitted by the laser; d1, the distance between the emitting end of the laser and the surface of the sample to be tested; d2, the distance between the sampling and ionization end of the carbon fiber and the surface of the sample to be tested; d3, the distance between the inlet end of the ion transfer tube and the surface of the sample to be tested. DETAILED DESCRIPTION

[0044] The technical solution of the present invention is further described in detail and completely below in conjunction with the accompanying drawings.

[0045] See also Figure 1As shown: a device for implementing the open mass spectrometry imaging method based on laser desorption assisted carbon fiber ionization described in the present invention, comprising a mass spectrometer, a laser 1, a carbon fiber 2 and a sample 3 to be tested, the carbon fiber 2 is electrically connected to a high-voltage power supply 4, a capillary 5 is sleeved on the outside of the carbon fiber 2, the sampling and ionization end of the carbon fiber 2 passes through the outlet end of the capillary 5 and is located in front of the injection port 6 of the mass spectrometer, the sample 3 to be tested is located between the laser 1, the sampling and ionization end of the carbon fiber 2 and the injection port 6 of the mass spectrometer, and the inlet end of the capillary 5 is connected to a solvent / reagent channel 7 for introducing an auxiliary solvent or a derivatization reagent.

[0046] The mass spectrometer used in the present invention can be a common mass spectrometer such as a triple quadrupole mass spectrometer, a time-of-flight mass spectrometer, an ion trap mass spectrometer, or a Fourier transform ion cyclotron resonance mass spectrometer.

[0047] The above-mentioned device is used to implement the open mass spectrometry imaging method described in the present invention, which is to first emit laser light from the laser 1 to hit the sample 3 to desorb the sample 3, and then ionize the desorbed sample 3 by applying voltage to the carbon fiber with the assistance of an auxiliary solvent or a derivatization reagent, and finally allow the generated sample ions to enter the mass spectrometer from the injection port 6 of the mass spectrometer, and perform mass spectrometry analysis and imaging through the mass spectrometer.

[0048] For details, see Figure 1 As shown, the following steps are included:

[0049] a) placing the sample 3 to be tested between the laser 1, the sampling and ionization end of the carbon fiber 2 and the injection port 6 of the mass spectrometer;

[0050] b) emitting laser light from the laser 1 to hit the sample 3 to be tested, so that the sample 3 to be tested is desorbed;

[0051] c) introducing an auxiliary solvent or a derivatization reagent into the sampling and ionization end of the carbon fiber 2 through a solvent / reagent channel;

[0052] d) turning on the high-voltage power supply 4, applying voltage to the carbon fiber 2 through the high-voltage power supply 4, and the unattached sample 3 to be tested is collected and ionized by the sampling and ionization end of the carbon fiber 2 to generate sample ions;

[0053] e) allowing the generated sample ions to enter the mass spectrometer from the injection port 6 of the mass spectrometer, and performing mass spectrometry analysis and imaging by the mass spectrometer.

[0054] In the present invention, the carbon fiber 2 and the high voltage power supply 4 may be electrically connected in a conventional manner. For example, the high voltage power supply 4 is connected to the carbon fiber 2 via a conductive metal foil (not shown in the figure).

[0055] In the present invention, the voltage of the high voltage power supply 4 is preferably 1 to 3 kV.

[0056] In the present invention, the laser 1, the sampling and ionization end of the carbon fiber 2, and the injection port 6 of the mass spectrometer are in a separated state, and the relative positions of the three and the positions of the three relative to the sample 3 to be measured can be adjusted.

[0057] In the present invention, the laser 1 is located above the sample 3 to be tested, preferably directly above it, so that the laser 1 can emit laser light to hit the surface of the sample 3 to be tested. Accordingly, the angle α1 between the laser line emitted by the laser 1 and the surface of the sample 3 to be tested is preferably 45 to 90 degrees, preferably 90 degrees.

[0058] In the present invention, the distance d1 between the emission end of the laser 1 and the surface of the sample 3 to be measured is preferably 10 to 15 cm.

[0059] In the present invention, the diameter of the sampling and ionization ends of the carbon fiber 2 is preferably 1 to 20 microns.

[0060] In the present invention, the angle α2 between the axis of the carbon fiber 2 and the laser line emitted by the laser 1 is preferably 30 to 45 degrees, preferably 45 degrees.

[0061] In the present invention, the distance d2 between the sampling and ionization end of the carbon fiber 2 and the surface of the sample 3 to be tested is preferably 1 to 5 mm, preferably 2 mm.

[0062] In the present invention, the auxiliary solvent is a polar or non-polar organic solvent, including but not limited to methanol, dichloromethane, acetonitrile and toluene, and the derivatization reagent refers to a derivatization reagent that can react with specific chemical groups, and the chemical groups include but are not limited to hydroxyl, carboxyl, carbon-carbon double bond, and amino group.

[0063] In the present invention, the solvent / reagent channel 7 is a peek tube, and a two-way 8 is connected between the outlet end of the peek tube 7 and the inlet end of the capillary 5, and the inlet end of the peek tube 7 is connected to an injection needle 9. The injection needle 9 is used to inject the auxiliary solvent or derivatization reagent into the capillary 5, specifically: the auxiliary solvent or derivatization reagent is injected into the solvent / reagent channel (peek tube) 7 through the injection needle 9, and then the auxiliary solvent or derivatization reagent is introduced into the capillary 5 through the solvent / reagent channel (peek tube) 7, and then introduced into the sampling and ionization end of the carbon fiber 2.

[0064] In the present invention, the flow rate of the auxiliary solvent or the derivatization reagent in the solvent / reagent channel 7 is preferably 1 to 5 μl / min, preferably 4 μl / min.

[0065] In a preferred embodiment, the device further comprises a peristaltic pump 10, and the injection needle 9 is mounted on the peristaltic pump 10. The peristaltic pump 10 is used to carry the injection needle 9 and push the injection needle 9 at a set flow rate, thereby introducing the auxiliary solvent or derivatization reagent into the sampling and ionization end of the carbon fiber 2 at the set flow rate. The flow rate set by the peristaltic pump 10 is equivalent to the flow rate of the auxiliary solvent or derivatization reagent in the solvent / reagent channel 7.

[0066] In a preferred embodiment, the device further comprises a sample carrier 11, the sample 3 to be tested is placed on the top of the sample carrier 11, and the sample carrier 11 is located between the sampling and ionization end of the carbon fiber 2 and the injection port 6 of the mass spectrometer. The sample carrier 11 is used to carry and fix the sample 3 to be tested. When in use, the sample carrier 11 is placed between the sampling and ionization end of the carbon fiber 2 and the injection port 6 of the mass spectrometer, and is located below the laser 1, and then the sample 3 to be tested is placed on the top of the sample carrier 11.

[0067] In a preferred embodiment, the device further comprises a two-dimensional mobile platform 12, and the sample carrier 11 is placed on the top of the two-dimensional mobile platform 12. The two-dimensional mobile platform 12 is used to carry the sample carrier 11 and the sample 3 to be tested, and can move according to the set step length. During mass spectrometry imaging, the two-dimensional mobile platform 12 can move by the set step length so that the laser 1 and the carbon fiber 2 can desorb and ionize the selected sample detection area, and then desorb and ionize the sample 3 to be tested in the sample detection area.

[0068] In a preferred embodiment, the device further comprises an ion transfer tube 13, the outlet end of the ion transfer tube 13 is connected to the injection port 6 of the mass spectrometer, and the inlet end of the ion transfer tube 13 is located near the sample to be tested 3. During mass spectrometry imaging, the generated sample ions enter the mass spectrometer from the injection port 6 of the mass spectrometer through the ion transfer tube 13.

[0069] In the present invention, the distance d3 between the inlet end of the ion transfer tube 13 and the surface of the sample 3 to be tested is preferably 1 to 5 mm, preferably 2 mm.

[0070] In the present invention, the angle α3 between the axis of the inlet end of the ion transfer tube 13 and the laser line emitted by the laser 1 is preferably 30 to 45 degrees, preferably 45 degrees.

[0071] The technical effects that can be achieved by the present invention are further explained below in conjunction with specific application examples.

[0072] Example 1

[0073] use Figure 1The device shown (wherein the mass analyzer of the mass spectrometer is a quadrupole-time of flight) and the open mass spectrometry imaging method based on laser desorption assisted carbon fiber ionization described in the present invention are used to perform mass spectrometry analysis and imaging on a C57 mouse brain tissue slice sample (16 μm):

[0074] A sample slide 11 is placed on the top of a two-dimensional moving platform 12, and a sample 3 to be tested (a sample of a C57 mouse brain tissue slice) is placed on the top of the sample slide 11, and the sample 3 to be tested is located between the laser 1, the sampling and ionization end of the carbon fiber 2, and the injection port 6 of the mass spectrometer (specifically, the inlet end of the ion transfer tube 13 connected to the injection port 6 of the mass spectrometer); the laser 1 is used to emit a laser to hit the sample 3 to be tested (the two-dimensional moving platform 12 moves a distance of 100 μm and a moving speed of 200 μm / s after each laser hits the sample 3 to be tested), and the distance between the laser and the sample 3 to be tested is 15 cm, so that the sample 3 to be tested is desorbed. ; The auxiliary solvent methanol (flow rate is 3 μl / min) is introduced into the sampling and ionization end of the carbon fiber 2 through the solvent / reagent channel, and the distance between the sampling and ionization end and the sample 3 to be tested is 1 mm; the high-voltage power supply 4 is turned on, and a high voltage of 2.5 kV is applied to the carbon fiber 2 through the high-voltage power supply 4, and the desorbed sample 3 to be tested is collected and ionized by the sampling and ionization end of the carbon fiber 2 to generate sample ions; the generated sample ions enter the mass spectrometer from the injection port 6 of the mass spectrometer through the ion transfer tube 13 (the distance between the inlet end of the ion transfer tube 13 and the surface of the sample 3 to be tested is 2 mm), and mass spectrometry analysis and imaging are performed by the mass spectrometer, and the results are as follows: Figure 2 and Figure 3 shown.

[0075] Figure 2 : is the primary mass spectrum in positive ion mode obtained by direct mass spectrometry imaging using methanol as the auxiliary solvent for carbon fiber in this embodiment; Figure 2 It can be seen that the mass spectrum shows relatively abundant signals in both the low molecular weight (less than 500Da) and higher molecular weight regions (500-900Da), providing strong data support for the analysis of biological samples.

[0076] Figure 3 This is a positive ion mode mass spectrometry imaging diagram obtained by direct mass spectrometry imaging using methanol as a carbon fiber auxiliary solvent in this embodiment; Figure 3 Representative mass spectrometric images of endogenous metabolites in the low- and higher-molecular-weight regions are shown.

[0077] Example 2

[0078] use Figure 1The device shown (wherein the mass analyzer of the mass spectrometer is a quadrupole-time of flight) and the open mass spectrometry imaging method based on laser desorption assisted carbon fiber ionization described in the present invention are used to perform mass spectrometry analysis and imaging on a C57 mouse brain tissue slice sample (16 μm):

[0079] The sample carrier 11 is placed on the top of the two-dimensional moving platform 12, and the sample 3 to be tested (C57 mouse brain tissue slice sample) is placed on the top of the sample carrier 11, and the sample 3 to be tested is located between the laser 1, the sampling and ionization end of the carbon fiber 2, and the injection port 6 of the mass spectrometer (specifically, the inlet end of the ion transfer tube 13 connected to the injection port 6 of the mass spectrometer); the laser 1 is used to emit a laser to hit the sample 3 to be tested (the two-dimensional moving platform 12 moves a distance of 100 μm after each laser hits the sample 3 point to be tested, and the moving speed is 200 μm / s), and the distance between the laser and the sample 3 to be tested is 15 cm, so that the sample 3 to be tested is desorbed; the derivatization solvent (1 % pyridine + 1% deuterated pyridine in dichloromethane solution, the flow rate is 4 microliters / minute) is introduced into the sampling and ionization end of the carbon fiber 2 through the solvent / reagent channel, and the distance between the sampling and ionization end and the sample 3 to be tested is 1mm; the high-voltage power supply 4 is turned on, and a high voltage of 2.5kV is applied to the carbon fiber 2 through the high-voltage power supply 4, and the desorbed sample 3 to be tested is collected and ionized by the sampling and ionization end of the carbon fiber 2 to generate sample ions; the generated sample ions enter the mass spectrometer from the injection port 6 of the mass spectrometer through the ion transfer tube 13 (the distance between the inlet end of the ion transfer tube 13 and the surface of the sample 3 to be tested is 2mm), and mass spectrometry analysis and imaging are performed by the mass spectrometer, and the results are as follows: Figure 4 and Figure 5 shown.

[0080] Figure 4 This is the primary mass spectrum in positive ion mode obtained by using a derivatization reagent (pyridine / deuterated pyridine in dichloromethane solution) to pass through carbon fiber for online derivatization mass spectrometry imaging on tissue in this example; Figure 4 It can be seen that in the average mass spectrum after derivatization, a mass spectral peak pair of glycerolipids and sphingolipids with a mass-to-charge ratio difference of 5.03 Da appeared in the range of m / z 500-850.

[0081] Figure 5 This is a positive ion mode mass spectrometry image obtained by using a derivatization reagent (pyridine / deuterated pyridine in dichloromethane solution) to pass through carbon fiber to perform online derivatization mass spectrometry imaging on tissue in this example; Figure 5The corresponding mass spectrum imaging diagrams of the mass spectrum peaks shown in the region are shown, in which: A. peaks of derivatization products of pyridine and deuterated pyridine: m / z 702.7457 and m / z 707.7709; B. peaks of derivatization products of pyridine and deuterated pyridine: m / z 628.7310 and m / z 631.7617; C. peaks of derivatization products of pyridine and deuterated pyridine: m / z 710.7437 and m / z 715.7776; D. peaks of derivatization products of pyridine and deuterated pyridine: m / z 710.7332 and m / z 715.7626.

[0082] Finally, it is necessary to point out here that the above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto, and any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. An open mass spectrometry imaging method based on laser desorption assisted carbon fiber ionization, characterized in that: The method is to firstly emit laser light to hit the sample to be tested so as to desorb the sample to be tested, and then ionize the desorbed sample to be tested by applying voltage to the carbon fiber with the assistance of an auxiliary solvent or a derivatization reagent, and finally allow the generated sample ions to enter the mass spectrometer from the injection port of the mass spectrometer, and perform mass spectrometry analysis and imaging through the mass spectrometer; the method specifically includes the following steps: a) placing the sample to be tested between the laser, the sampling and ionization end of the carbon fiber and the injection port of the mass spectrometer, wherein the outer sleeve of the carbon fiber is provided with a capillary tube, the sampling and ionization end of the carbon fiber passes through the outlet end of the capillary tube and is located in front of the injection port of the mass spectrometer, the inlet end of the capillary tube is connected to a solvent / reagent channel for introducing an auxiliary solvent or a derivatization reagent, the solvent / reagent channel is a peek tube, a two-way tube is connected between the outlet end of the peek tube and the inlet end of the capillary tube, and the inlet end of the peek tube is connected to an injection needle; b) emitting laser light to hit the sample to be tested, so as to desorb the sample to be tested; c) introducing an auxiliary solvent or a derivatization reagent into the sampling and ionization end of the carbon fiber through a solvent / reagent channel; d) turning on a high-voltage power supply, applying voltage to the carbon fiber through the high-voltage power supply, so that the desorbed sample to be tested is collected and ionized by the sampling and ionization end of the carbon fiber to generate sample ions; e) allowing the generated sample ions to enter the mass spectrometer from the injection port of the mass spectrometer, and performing mass spectrometry analysis and imaging by the mass spectrometer.

2. The open mass spectrometry imaging method based on laser desorption assisted carbon fiber ionization according to claim 1, characterized in that: The angle between the laser line emitted by the laser and the surface of the sample to be measured is 45 to 90 degrees.

3. The open mass spectrometry imaging method based on laser desorption assisted carbon fiber ionization according to claim 1, characterized in that: The distance between the emission end of the laser and the surface of the sample to be measured is 10 to 15 centimeters.

4. The open mass spectrometry imaging method based on laser desorption assisted carbon fiber ionization according to claim 1, characterized in that: The angle between the axis of the carbon fiber and the laser line emitted by the laser is 30 to 45 degrees.

5. The open mass spectrometry imaging method based on laser desorption assisted carbon fiber ionization according to claim 1, characterized in that: The distance between the sampling and ionization end of the carbon fiber and the surface of the sample to be tested is 1 to 5 mm.

6. The open mass spectrometry imaging method based on laser desorption assisted carbon fiber ionization according to claim 1, characterized in that: The sample to be tested is placed on the top of a sample carrier, and the sample carrier is located between the sampling and ionization end of the carbon fiber and the injection port of the mass spectrometer.

7. The open mass spectrometry imaging method based on laser desorption assisted carbon fiber ionization according to claim 6, characterized in that: The sample carrier is placed on top of the two-dimensional moving platform.

8. The open mass spectrometry imaging method based on laser desorption assisted carbon fiber ionization according to claim 1, characterized in that: The sample inlet of the mass spectrometer is connected with an ion transmission tube, and the inlet end of the ion transmission tube is located near the sample to be tested.

Images