Nanoliter spray ionization mass spectrometry interface device and analytical instrument and ionization method

Abstract

The application discloses a nanoliter spray ionization mass spectrometry interface device, an analytical instrument and an ionization method, and belongs to the technical field of electrospray mass spectrometry ionization devices. The nanoliter spray ionization mass spectrometry interface device comprises an ion guide tube, a first electrode and a second electrode; the inner wall of the ion guide tube is plated with a conductive film; the ion guide tube has an ion transmission channel in the form of a funnel along the length direction of the tube; the ion transmission channel has a first end and a second end; the diameter of the ion transmission channel gradually decreases from the first end to the second end; the first electrode is connected to the end of the first end; and the second electrode is connected to the end of the second end. The device has a simple structure and is convenient to operate; high stability, high sample utilization and high ion transmission efficiency of the electrospray process under a nanoliter flow rate can be realized; positive and negative switching can be directly and rapidly performed under the condition of normal pressure and opening; and problems, such as unstable spraying caused by bad high pressure and complex parameter optimization process, are avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrospray mass spectrometry ionization device, in particular to a nanospray ionization mass spectrometry interface device, an analytical instrument and an ionization method. BACKGROUND

[0002] Electrospray ionization source is a common ionization method for organic mass spectrometry instrument, wherein the nanospray (Nano-ESI) ionization source can realize ionization of a target object at a lower voltage and without sheath flow gas due to the use of a smaller inner diameter capillary needle, has a very small flow rate, requires a small amount of sample and has higher sensitivity than a traditional electrospray ionization source, and is widely used in the fields of biological detection, life science, proteomics and metabolomics.

[0003] However, the following problems usually exist when using Nano-ESI analysis:

[0004] (1) Poor high voltage can cause unstable spraying;

[0005] (2) Mass spectrometry signal stability is easily affected by external environment;

[0006] (3) When the sample or ion source is replaced, parameter optimization is complex and greatly affects ionization effect.

[0007] The above problems result in poor stability and repeatability of analysis and determination results.

[0008] In view of this, the present application is proposed. SUMMARY

[0009] One of the purposes of the present application is to provide a nanospray ionization mass spectrometry interface device to at least solve one of the above technical problems.

[0010] The second purpose of the present application is to provide a nanospray ionization mass spectrometry analysis instrument comprising the nanospray ionization mass spectrometry interface device.

[0011] The third purpose of the present application is to provide a method for ionization treatment using the nanospray ionization mass spectrometry interface device or the nanospray ionization mass spectrometry analysis instrument.

[0012] The present application can be implemented as follows:

[0013] In a first aspect, the present application provides a nanospray ionization mass spectrometry interface device comprising an ion guide tube, a first electrode and a second electrode.

[0014] The inner wall of the ion guide tube is coated with a conductive film, the ion guide tube has an ion transmission channel in the form of a funnel along the length of the tube, the ion transmission channel has a first end for directing ions towards the nano-ESI device and a second end opposite the first end; the diameter of the ion transmission channel gradually decreases from the first end to the second end.

[0015] The first electrode is connected to the end of the first end, and the second electrode is connected to the end of the second end.

[0016] In an optional embodiment, the diameter of the first end is 10-20 mm, and / or the diameter of the second end is 0.5-1 mm.

[0017] In an optional embodiment, the ion guide tube is a transparent tube, and / or the conductive film is a metal oxide conductive film.

[0018] In an optional embodiment, the ion guide tube is a quartz tube.

[0019] In an optional embodiment, the metal oxide is indium tin oxide.

[0020] In an optional embodiment, the first electrode is a metal ring, and the inner diameter of the first electrode is equal to the diameter of the first end; and / or the second electrode is a metal ring or a sampling cone, and the inner diameter of the end of the second electrode for connecting to the second end is equal to the diameter of the second end.

[0021] In an optional embodiment, the nano-ESI ionization MS interface device further comprises a heating device for heating the ion guide tube.

[0022] In an optional embodiment, the heating device is arranged around the outer wall of the ion guide tube.

[0023] In an optional embodiment, the heating device is a heating tape, a heating rod or a resistance wire.

[0024] In an optional embodiment, the nano-ESI ionization MS interface device further comprises a temperature sensor.

[0025] The temperature sensor is arranged on the outer wall of the ion guide tube.

[0026] In an optional embodiment, the nano-ESI ionization MS interface device further comprises a power supply device;

[0027] The power supply device is connected to the first electrode, the second electrode and the heating device, respectively.

[0028] In an optional embodiment, the nano-ESI ionization MS interface device further comprises a photoionization device, and the photoionization device is arranged on the outer wall of the ion guide tube.

[0029] In an optional embodiment, the photoionization device is an ultraviolet lamp.

[0030] In an optional embodiment, the nanospray ionization mass spectrometry interface device further comprises a nanospray device, one end of which is used to extend into the ion transmission channel of the ion guide tube during detection.

[0031] In an optional embodiment, the extension distance is 1-2 mm.

[0032] In an optional embodiment, the nanospray device is a combination structure of a spray needle and a nanoscale chromatographic column.

[0033] In an optional embodiment, the nanospray device is supported by a moving platform.

[0034] In a second aspect, the present application provides a nanospray ionization mass spectrometry analysis instrument, comprising a mass spectrometer and the nanospray ionization mass spectrometry interface device of any one of the preceding embodiments, and the second end of the ion transmission channel is connected to the mass spectrometry inlet of the mass spectrometer.

[0035] In a third aspect, the present application provides an ionization method, comprising: ionizing a sample to be tested by using the nanospray ionization mass spectrometry interface device of any one of the preceding embodiments or the nanospray ionization mass spectrometry analysis instrument of the preceding embodiments.

[0036] In an optional embodiment, the ionization process comprises: applying high voltage to both the first electrode and the second electrode to form a high voltage electric field between the nanospray device and the mass spectrometry inlet and induce the solvent containing target compounds in the nanospray device to generate electrospray ionization; and turning on the heating device to heat the ion guide tube so that the ions after the solvent is removed are focused and transmitted to the mass spectrometer by the axial electric field formed by the inner wall of the ion guide tube for analysis.

[0037] In an optional embodiment, the high voltage applied by the first electrode is HV1, and in positive ion mode, HV1=0-5 kV, and in negative ion mode, HV1=0-5 kV; the high voltage applied by the second electrode is HV2, and HV2=HV1-U, U=10-200 V.

[0038] In an optional embodiment, the heating temperature of the heating device for the ion guide tube is not more than 350°C.

[0039] The beneficial effects of the present application include:

[0040] The conductive film is arranged on the inner layer of the ion guide tube. When the first electrode and the second electrode at the two ends of the ion guide tube are electrified, a high-voltage axial electric field is formed between the nanoliter spraying device and the mass spectrometry inlet, and the solvent containing the target compound in the nanoliter spraying device is induced to generate electrospray electricity, so that the positive and negative switching can be directly and quickly performed under the condition of normal pressure opening, and the problems of unstable spraying caused by high pressure and complex parameter optimization process are avoided. In addition, the above-mentioned axial electric field can effectively focus and transmit the ions into the mass spectrometry analysis, improve the transmission efficiency, and greatly reduce the influence of the position, angle and other parameters of the nanoliter spraying device on the ionization efficiency, and avoid the complex parameter optimization when the sample or ion source is replaced. BRIEF DESCRIPTION OF DRAWINGS

[0041] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0042] Figure 1 Part of the structure schematic diagram of the nanoliter spraying ionization mass spectrometry instrument provided for Embodiment 1 of the present application is shown in the figure.

[0043] Figure 2 Part of the structure schematic diagram of the nanoliter spraying ionization mass spectrometry instrument provided for Embodiment 2 of the present application is shown in the figure.

[0044] Figure legend: 1-nanoliter spraying device; 2-first electrode; 3-ion guide tube; 31-ion transmission channel; 4-second electrode; 5-heating device; 6-temperature sensor; 7-power supply device; 8-photoionization device; 9-mass spectrometer. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below. If the specific conditions are not specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturer are used. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased on the market.

[0046] The nanoliter spraying ionization mass spectrometry interface device and analysis instrument and ionization method provided by the present application will be described in detail below.

[0047] The present application provides a nanoliter spraying ionization mass spectrometry interface device, which comprises an ion guide tube 3, a first electrode 2 and a second electrode 4.

[0048] The inner wall of the ion guide tube 3 is plated with a conductive film, the ion guide tube 3 has an ion transmission channel 31 in the form of a funnel along the length direction of the tube, the ion transmission channel 31 has a first end for being directed towards the nanoliter spraying device 1 and a second end opposite to the first end (i.e. the second end as a mass spectrometry interface); the diameter of the ion transmission channel 31 gradually decreases from the first end to the second end.

[0049] In the present application, the ion guide tube 3 is a transparent tube, which can be a quartz tube exemplarily. In addition, it is also not excluded that it can be other transparent materials, such as Pyrex glass, etc.

[0050] The conductive film provided on the inner wall of the ion guide tube 3 is a metal oxide conductive film. Exemplarily, the metal oxide can be but is not limited to indium tin oxide.

[0051] By providing the conductive film on the inner wall of the ion guide tube 3, the entire inner side of the ion guide tube 3 can be conductive.

[0052] In the present application, the ion transmission channel 31 is in the form of a funnel, which facilitates focusing of the ionized ions and introducing the ions from the atmospheric pressure environment into the vacuum environment in the mass spectrometer.

[0053] For reference, the diameter of the first end of the ion transmission channel 31 can be 10-20mm, such as 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm or 20mm, etc., and can also be other arbitrary values within the range of 10-20mm.

[0054] The diameter of the second end can be 0.5-1mm, such as 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm or 1mm, etc., and can also be other arbitrary values within the range of 0.5-1mm.

[0055] By setting the diameters of the first end and the second end within the above range, the ion guide tube 3 has higher focusing and transmission effects.

[0056] In the present application, the first electrode 2 is connected to the end of the first end, and the second electrode 4 is connected to the end of the second end. In the working state, high voltage is applied to both the first electrode 2 and the second electrode 4, so as to form charged droplets in the nanoliter spraying device 1, and at the same time form an axial electric field in the ion guide tube 3 for ion focusing and transmission.

[0057] For reference, the first electrode 2 is a metal ring, and the inner diameter of the first electrode 2 is equal to the diameter of the first end.

[0058] The second electrode 4 can be a metal ring or a sampling cone. When the second electrode 4 is a metal ring, the inner diameter of the second electrode 4 is equal to the diameter of the second end; when the second electrode 4 is a sampling cone, the inner diameter of the end of the sampling cone for connecting the second end is equal to the diameter of the second end.

[0059] and the inner diameter of the second electrode 4 is equal to the diameter of the second end.

[0060] Further, by arranging the conductive film on the inner layer of the ion guide tube 3, when the first electrode 2 and the second electrode 4 at both ends of the ion guide tube 3 are electrified, a high-voltage axial electric field can be formed between the nanoliter spraying device 1 and the mass spectrometry inlet, which can induce the solvent containing the target compound in the nanoliter spraying device 1 to generate electrospray electricity, so that the positive and negative switching can be directly performed under the condition of normal pressure opening, and the problems such as unstable spraying caused by high pressure and complex parameter optimization process can be avoided. In addition, the above-mentioned axial electric field can effectively focus and transmit ions into mass spectrometry analysis, improve transmission efficiency, and greatly reduce the influence of the position, angle and other parameters of the nanoliter spraying device 1 on ionization efficiency, and avoid complex parameter optimization when replacing the sample or ion source.

[0061] Further, the above-mentioned nanoliter spraying ionization mass spectrometry interface device further comprises a nanoliter spraying device 1, one end of the nanoliter spraying device 1 being used to extend into the ion transmission channel 31 of the ion guide tube 3 during detection.

[0062] For reference, the extension distance can be 1-2 mm, such as 1 mm, 1.2 mm, 1.5 mm, 1.8 mm or 2 mm, etc. Preferably, the length of the ion transmission channel 31 corresponding to the above-mentioned extension distance can be 70-80 mm.

[0063] The above-mentioned nanoliter spraying device 1 is a combined structure of a spraying needle and a nanoliter chromatographic column, for example, it can be an integrated nanoliter chromatographic column with a spraying needle, or it can be a structure of a nanoliter chromatographic column plus a spraying needle. The flow rate range of the nanoliter spraying device 1 can be 10 nL-1000 nL.

[0064] The nanoliter spraying device 1 can be supported by a moving platform (such as a three-dimensional moving platform) to adjust the position of the nanoliter spraying device 1.

[0065] Further, the nanoliter spraying ionization mass spectrometry interface device provided by the present application further comprises a heating device 5 for heating the ion guide tube 3.

[0066] For reference, the heating device 5 is arranged around the outer wall of the ion guide tube 3.

[0067] The heating device 5 exemplarily but not limitatively can be a heating belt, a heating rod or a resistance wire.

[0068] The heating device 5 is mainly used for heating the ion guide tube 3 to remove solvent from the charged droplets.

[0069] Further, the nanospray ionization mass spectrometry interface device further comprises a temperature sensor 6.

[0070] The temperature sensor 6 is arranged on the outer wall of the ion guide tube 3 to monitor the temperature of the heating device 5.

[0071] Further, the nanospray ionization mass spectrometry interface device further comprises a power supply device 7.

[0072] The power supply device 7 is connected with the first electrode 2, the second electrode 4 and the heating device 5 respectively to supply power to the first electrode 2, the second electrode 4 and the heating device 5.

[0073] Further, the nanospray ionization mass spectrometry interface device can further comprise a photoionization device 8 arranged on the outer wall of the ion guide tube 3.

[0074] The photoionization device 8 can be used for auxiliary ionization of non-polar substances to increase ionization efficiency.

[0075] For reference, the photoionization device 8 can exemplarily be an ultraviolet lamp.

[0076] Correspondingly, the application further provides a nanospray ionization mass spectrometry instrument, which comprises a mass spectrometer 9 and the nanospray ionization mass spectrometry interface device, and the second end of the ion transmission channel 31 is connected with a mass spectrometry inlet of the mass spectrometer 9.

[0077] Other structures of the mass spectrometer 9 can refer to related prior art and will not be described in detail here.

[0078] In addition, the application further provides an ionization method, which comprises: using the nanospray ionization mass spectrometry interface device or the nanospray ionization mass spectrometry instrument to ionize a sample to be tested.

[0079] For reference, the ionization process comprises: applying high voltage on the first electrode 2 and the second electrode 4 to form a high-voltage electric field between the nanospray device 1 and the mass spectrometry inlet and induce the solvent containing target compounds in the nanospray device 1 to generate electrospray ionization; turning on the heating device 5 to heat the ion guide tube 3 so that the ions after removing the solvent are focused by the axial electric field formed by the inner wall of the ion guide tube 3 and transmitted into the mass spectrometer 9 for analysis. During the heating process, the heating temperature of the ion guide tube 3 is monitored by the temperature sensor 6.

[0080] During the pressurizing process, HV1 represents the high voltage applied by the first electrode 2, in positive ion mode, HV1 = 0 ~ -5 kV (such as 0 kV, -0.5 kV, -1 kV, -1.5 kV, -2 kV, -2.5 kV, -3 kV, -3.5 kV, -4 kV, -4.5 kV or -5 kV, etc.), in negative ion mode, HV1 = 0 ~ 5 kV (such as 0 kV, 0.5 kV, 1 kV, 1.5 kV, 2 kV, 2.5 kV, 3 kV, 3.5 kV, 4 kV, 4.5 kV or 5 kV, etc.).

[0081] HV2 represents the high voltage applied by the second electrode 4, HV2 = HV1 - U, U = 10 ~ 200 V (such as 10 V, 20 V, 50 V, 80 V, 100 V, 120 V, 150 V, 180 V or 200 V, etc.).

[0082] During the heating process, the heating temperature of the ion guide tube 3 by the heating device 5 does not exceed 350℃, such as 350℃, 300℃, 250℃ or 200℃, etc.

[0083] The features and performances of the present application are further described in detail below in combination with examples.

[0084] Example 1

[0085] The present example provides a nano-spray ionization mass spectrometer instrument, as shown in the figure, which comprises a mass spectrometer 9 and a nano-spray ionization mass spectrometry interface device. Figure 1

[0086] The nano-spray ionization mass spectrometry interface device comprises a nano-spray device 1, a first electrode 2, an ion guide tube 3, a second electrode 4, a heating device 5, a temperature sensor 6 and a power supply device 7.

[0087] The ion guide tube 3 is a quartz tube with an indium tin oxide conductive film on the inner wall, and the ion guide tube 3 has an ion transmission channel 31 in the form of a funnel along the length of the tube for focusing ions and introducing ions from an atmospheric pressure environment into a vacuum environment in the mass spectrometer.

[0088] The ion transmission channel 31 has a first end for facing the nano-spray device 1 and a second end opposite the first end, and the second end is connected with the mass spectrometry inlet of the mass spectrometer 9. The diameter of the ion transmission channel 31 gradually decreases from the first end to the second end. The diameter of the first end is 20 mm, the diameter of the second end is 0.5 mm, and the length of the entire ion transmission channel 31 is 75 mm.

[0089] The nano-spray device 1 is a nano-spray needle structure with a nano-spray column, and the working flow rate range is 300 nL ~ 1000 nL.

[0090] ​The metal spray needle of the nanoliter spray device 1 extends into the ion transmission channel 31 of the ion guide tube 3 by 1 mm.

[0091] The first electrode 2 is connected to the end of the first end, and the second electrode 4 is connected to the end of the second end.

[0092] The first electrode 2 and the second electrode 4 are both metal rings, the inner hole diameter of the first electrode 2 is 20 mm, and the inner hole diameter of the second electrode 4 is 0.5 mm. A high voltage HV1 is applied to the first electrode 2, HV1 = 0 ~ -5 kV in positive ion mode and HV1 = 0 ~ 5 kV in negative ion mode; a high voltage HV2 is applied to the second electrode 4, HV2 = HV1 - U, U is adjustable between 10 ~ 200 V, which is used to form charged droplets for the nanoliter spray device 1, and at the same time form an axial electric field in the ion guide tube 3 for ion focusing and transmission.

[0093] The heating device 5 (heating belt) is arranged around the outer wall of the ion guide tube 3, which is used to heat the ion guide tube 3 to remove the solvent from the charged droplets, and the maximum heating temperature is 350℃.

[0094] The temperature sensor 6 is arranged on the outer wall of the ion guide tube 3, which is used to monitor the temperature of the heating device 5.

[0095] The power supply device 7 is connected to the first electrode 2, the second electrode 4 and the heating device 5 respectively to supply power to the first electrode 2, the second electrode 4 and the heating device 5.

[0096] Example 2

[0097] The embodiment provides a nanoliter spray ionization mass spectrometer instrument, as shown in the figure, which comprises a mass spectrometer 9 and a nanoliter spray ionization mass spectrometry interface device. Figure 2

[0098] The nanoliter spray ionization mass spectrometry interface device comprises a nanoliter spray device 1, a first electrode 2, an ion guide tube 3, a second electrode 4, a heating device 5, a temperature sensor 6, a photoionization device 8 and a power supply device 7.

[0099] The ion guide tube 3 is a quartz tube with an indium tin oxide conductive film coated on the inner wall, and the ion guide tube 3 has an ion transmission channel 31 in the form of a funnel along the length direction of the tube for focusing ions and introducing ions from an atmospheric pressure environment into a vacuum environment in the mass spectrometer.

[0100] The ion transmission channel 31 has a first end facing the nanoliter spray device 1 and a second end opposite to the first end, and the second end is connected to the mass spectrometry inlet of the mass spectrometer 9. The diameter of the ion transmission channel 31 gradually decreases from the first end to the second end. The diameter of the first end is 10 mm, the diameter of the second end is 1 mm, and the length of the whole ion transmission channel 31 is 80 mm. ​

[0101] The nanoliter spraying device 1 is a structure of a nanoliter chromatographic column with a spraying needle, and the working flow rate ranges from 100 nL to 1000 nL.

[0102] The metal spraying needle of the nanoliter spraying device 1 extends into the ion transmission channel 31 of the ion guide tube 3 by 2 mm.

[0103] The first electrode 2 is connected to the end of the first end, and the second electrode 4 is connected to the end of the second end.

[0104] The first electrode 2 and the second electrode 4 are both metal rings, the inner hole diameter of the first electrode 2 is 10 mm, and the inner hole diameter of the second electrode 4 is 1 mm. A high voltage HV1 is applied to the first electrode 2, HV1 = 0-5 kV in positive ion mode and HV1 = 0-5 kV in negative ion mode; a high voltage HV2 is applied to the second electrode 4, HV2 = HV1-U, U is adjustable from 10-200 V, which is used to form charged droplets for the nanoliter spraying device 1, and at the same time, an axial electric field is formed in the ion guide tube 3 for ion focusing and transmission.

[0105] The heating device 5 (resistance wire) is arranged on the outer wall of the ion guide tube 3, which is used to heat the ion guide tube 3 and desolvate the charged droplets, and the maximum heating temperature is 350℃.

[0106] The photoionization device 8 (ultraviolet) is arranged on the outer wall of the ion guide tube 3, which is used to assist ionization.

[0107] The temperature sensor 6 is arranged on the outer wall of the ion guide tube 3, which is used to monitor the temperature of the heating device 5.

[0108] The power supply device 7 is connected with the first electrode 2, the second electrode 4 and the heating device 5 respectively, so as to supply power for the first electrode 2, the second electrode 4 and the heating device 5.

[0109] In summary, the nanoliter spraying ionization mass spectrometry interface device provided by the application has simple structure and convenient operation, can realize high stability, high sample utilization rate and high ion transmission efficiency of the electrospray process under nanoliter flow rate, can directly switch positive and negative electrodes quickly under the condition of normal pressure and opening, and avoids problems such as unstable spraying caused by bad high pressure, complex parameter optimization process and the like.

[0110] The preferred embodiments of the application have been described above, but the application is not limited to the above. Any modifications, equivalent replacements, improvements and the like made within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. An ionization method, characterized in that, include: The sample to be tested was ionized using a nano-liter spray ionization mass spectrometer. The nano-spray ionization mass spectrometry analysis instrument includes a mass spectrometer and a nano-spray ionization mass spectrometry interface device, which includes an ion guide tube, a first electrode, and a second electrode. The inner wall of the ion guiding tube is coated with a conductive film. The ion guiding tube has an ion transmission channel in the shape of a funnel along the length of the tube. The ion transmission channel has a first end facing the nano-spray device and a second end opposite to the first end. The diameter of the ion transmission channel gradually decreases from the first end to the second end. The first electrode is connected to the end of the first end, and the second electrode is connected to the end of the second end; The diameter of the first end is 10-20 mm, and the diameter of the second end is 0.5-1 mm; The ion guiding tube is a transparent tube, and the conductive film is a metal oxide conductive film; The first electrode is a metal ring, and the inner diameter of the first electrode is equal to the diameter of the first end; the second electrode is a metal ring or a sampling cone, and the inner diameter of the end of the second electrode used to connect to the second end is equal to the diameter of the second end. The nanoliter spray ionization mass spectrometry interface device further includes a heating device for heating the ion guide tube; the heating device is wound around the outer wall of the ion guide tube. The nanoliter spray ionization mass spectrometry interface device also includes a photoionization device, which is disposed on the outer wall of the ion guiding tube; The nano-spray ionization mass spectrometry interface device also includes a nano-spray device, one end of which is used to extend into the ion transmission channel of the ion guide tube during detection; the extension distance is 1-2 mm; the nano-spray device is a combination structure of a spray needle and a nano-chromatographic column; The second end of the ion transport channel is connected to the mass spectrometry inlet of the mass spectrometer; The ionization process includes: applying high voltage to both the first and second electrodes to form a high voltage electric field between the nano-spray device and the mass spectrometer inlet and inducing the solvent containing the target compound in the nano-spray device to generate electrospray ionization; turning on the heating device to heat the ion guide tube so that the ions after solvent removal are focused by the axial electric field formed on the inner wall of the ion guide tube and transported to the mass spectrometer for analysis. The high voltage applied to the first electrode is HV1. In positive ion mode, HV1 = 0 to -5kV, and in negative ion mode, HV1 = 0 to 5kV. The high voltage applied to the second electrode is HV2, where HV2 = HV1 - U, and U = 10 to 200V. The heating temperature of the heating device on the ion guiding tube does not exceed 350℃.

2. The ionization method according to claim 1, characterized in that, The ion guiding tube is a quartz tube.

3. The ionization method according to claim 1, characterized in that, The metal oxide is indium tin oxide.

4. The ionization method according to claim 1, characterized in that, The heating device is a heating belt, a heating rod, or a resistance wire.

5. The ionization method according to claim 1, characterized in that, The nanoliter spray ionization mass spectrometry interface device also includes a temperature sensor. The temperature sensor is disposed on the outer wall of the ion guiding tube.

6. The ionization method according to claim 1, characterized in that, The nanoliter spray ionization mass spectrometry interface device also includes a power supply device; The power supply is connected to the first electrode, the second electrode, and the heating device, respectively.

7. The ionization method according to claim 1, characterized in that, The photoionization device is an ultraviolet lamp.

8. The ionization method according to claim 1, characterized in that, The nano-spray device is supported by a mobile platform.

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