JPH10142197A - Mass spectrometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To determine a positional relationship of an opening part and a capillary without special adjustment work. SOLUTION: A pipe support 57 is set at the side of an opening part of a pipe, whereby a position of the pipe at the side of the opening part is fixed. A hole is opened in the pipe support 57 to pass nitrogen gas. Therefore, a gas flow rate necessary for ionization is secured when a sample solution is sprayed at the opening part. The opening part and a gas feed chamber 51, and the pipe support 57 and the gas feed chamber 51 are constituted to be fitted with each other. Accordingly, adjustment work at the assembly time is eliminated, and the opening part, gas feed chamber and pipe support are assembled at a proper position every time. A capillary 58 can be always sent to the central part of the opening part owing to this structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mass spectrometer for ionizing a sample for mass separation.

[0002]

2. Description of the Related Art A mass spectrometer is an apparatus for mass-separating an ionized sample by controlling an electric field or a magnetic field. At present, mass filter type mass spectrometers and magnetic field type mass spectrometers are widely used. These mass spectrometers ionize a sample continuously, scan an electric field or a magnetic field, and perform mass separation by passing a predetermined mass. As another method, an ion trap type mass spectrometer is also known. It is configured such that ions are confined in a trap space by a quadrupole high-frequency electric field, ions are accumulated, and then mass separation is performed. Such a technique is known, for example, from U.S. Pat. No. 2,399,952.

On the other hand, for ionization of a sample, an atmospheric pressure ionization method is mainly used, and various methods are known. This atmospheric pressure ionization method ionizes a sample under atmospheric pressure,
The ions are introduced into a high vacuum mass spectrometer and mass spectrometry is performed. Generally, since it is technically difficult to rapidly reduce the pressure from the atmospheric pressure to a high vacuum, differential exhaust (an intermediate pressure chamber is provided between the atmospheric pressure and the high vacuum chamber). for that reason,
A vacuum pump for evacuating the high vacuum chamber and a vacuum pump for evacuating the intermediate pressure chamber are required. Further, a vacuum pump for evacuating the back pressure is required as a vacuum pump for evacuating the high vacuum chamber, and a total of three vacuum pumps have been used.

[0004] All three vacuum pumps are located outside the apparatus.

As the atmospheric pressure ionization method, for example, an electrostatic spray ionization (ESI) method and an atmospheric pressure chemical ionization (APCI) method are known. In addition, there is a sonic spray ionization (SSI) method. The SSI is to ionize a sample solution by spraying it with a substantially sonic airflow. Many are often used as ion sources in liquid chromatography-direct mass spectrometers. That is,
The sample solution introduced from the liquid chromatograph is introduced into the gas supply chamber through the inside of the capillary. Here, the sample is ionized by being sprayed at a substantially sonic speed at the opening by the nitrogen gas introduced from the nitrogen gas inlet, and at the same time, subjected to the desolvation action, and is introduced into the mass spectrometer.

[0006] ESI, APCI and SSI are often selected depending on the sample. Therefore, replacing the ion source according to the sample is becoming mainstream.

Further, an adhesive has been used for connecting the liquid chromatograph to the mass spectrometer.

[0008]

In the above prior art,
Since the type of ion source was discriminated by directly observing the ion source, it often occurred that the type of ion source was misidentified and analysis was continued. Therefore, there has been a problem that correct analysis cannot be performed. For example, there has been a problem in that the setting temperature is inappropriate and the sample is destroyed due to the misinterpretation of ESI and APCI, or cluster ions are mixed in due to insufficient solvent removal. Further, there has been a problem that the corona discharge voltage in the APCI becomes inappropriate and sufficient ionization of the sample cannot be performed.

An object of the present invention is to provide a mass spectrometer capable of performing analysis suitable for the type of ion source and performing accurate analysis.

Further, in the above-mentioned conventional example, at least three vacuum pumps are used for evacuating the work.
When the performance of even one of the two vacuum pumps deteriorates, the pressure in the intermediate pressure chamber or the mass spectrometry chamber becomes improper and a problem arises that accurate analysis cannot be performed.

An object of the present invention is to provide a mass spectrometer capable of improving the accuracy and reliability of analysis and performing accurate analysis.

Further, in the above-mentioned prior art, all three vacuum pumps are arranged outside the apparatus. Generally, the vacuum pump is large in both weight and volume, so it is removed, transported, and reassembled at the installation site. All the vacuum pumps are arranged outside the apparatus, and the parts (exhaust system etc.) connected to them are inevitably also outside, so that the evacuation conditions change every time they are moved, making it impossible to analyze under the same conditions. However, there has been a problem that the accuracy of the apparatus is not constant.

It is an object of the present invention to provide a mass spectrometer capable of stabilizing analysis accuracy and performing accurate analysis.

Further, in the above conventional example, since an adhesive is used for connecting the liquid chromatograph and the mass spectrometer, there is a problem that components in the adhesive are eluted by a solution introduced from the liquid chromatograph. is there. In addition, there has been a problem that the bonded portion becomes weak due to aging and external impurities are mixed in, so that accurate analysis cannot be performed.

[0015] It is an object of the present invention to provide a mass spectrometer capable of stabilizing analysis accuracy and performing accurate analysis.

Further, in the above-mentioned prior art, the sample ionized by the ionizing means diffuses around and a sufficient amount of ions are not introduced into the mass spectrometer. For this reason, there has been a problem that the analysis accuracy is reduced and accurate analysis cannot be performed.

An object of the present invention is to provide a mass spectrometer capable of improving analysis accuracy and performing accurate analysis.

One of the conditions for efficiently ionizing a sample in a sonic spray-on mass spectrometer is that the capillary must be arranged at the center of the opening so as not to touch the wall of the opening. In the conventional device, the position of the opening is adjustable, the capillary fixed to the pipe is carried to the vicinity of the opening, and the capillary is adjusted so as to come to the central position of the opening to determine the position. In this method, it is necessary to adjust the position of the opening every time the ion source is disassembled. However, since the hole diameter of the opening is about 0.4 mm, the adjustment operation requires the use of a microscope and is extremely difficult. And the reproducibility of the performance of the ion source is also problematic due to the difficulty of the operation.

An object of the present invention is to provide a mass spectrometer in which the positional relationship between the opening and the capillary is stable and accurate analysis is possible.

[0020]

In order to achieve the above object, the present invention provides an ionizing means for ionizing a sample,
In the mass spectrometer for mass-analyzing the ions, the ionization means can be replaced with different types of ionization, and the ionization means is provided with means for determining the type of ionization.

In order to achieve the above object, the present invention provides:
A first chamber lower than a pressure for ionizing a sample;
A second chamber having a pressure lower than that of the second chamber, and guiding the ionized sample to the second chamber via the first chamber;
A mass pump for mass separating the ions in the chamber or guiding the ions to a chamber having a lower pressure through the second chamber to perform mass separation, wherein a first pump for exhausting the first chamber; A second exhaust pump for exhausting the second chamber is provided, and the back pressure of the second pump is exhausted by the first pump.

In order to achieve the above object, the present invention provides:
In a mass spectrometer that ionizes a sample and guides the ionized sample to a high-vacuum high-vacuum chamber for mass separation, the mass spectrometer has an exhaust unit that exhausts the high-vacuum chamber, and the high-vacuum chamber and the exhaust unit are the same. It was configured to be stored in the casing.

In order to achieve the above object, the present invention provides:
A liquid chromatograph for column-separating a sample, and a mass spectrometer having mass spectrometry means for mass-analyzing an effluent from the liquid chromatograph, comprising a tube to which the effluent of the liquid chromatograph is supplied, wherein the tube Is supplied to the mass spectrometric means via a capillary, the capillary is inserted into one end of the tube, and the outer periphery of the tube is pressed.

In order to achieve the above object, according to the present invention, there is provided a mass spectrometer having an ionization means for ionizing a sample and a mass separation means for mass separating the ions, wherein a mass spectrometer is provided between the ionization means and the mass separation means. The passage has a member that forms a part, and further has a projection that projects from the member toward the mass spectrometric means.

In order to achieve the above object, according to the present invention, there is provided a pipe support which is disposed in contact with the periphery of the gas supply chamber to maintain the tip of the capillary at a predetermined position, The capillary cover is arranged so as to be in contact with the opening so as to surround the tip of the capillary and not to contact the tip of the capillary. By attaching a pipe support to the opening side of the pipe, the position of the pipe on the opening side can be fixed. The pipe support is provided with a hole through which nitrogen gas is passed, so that the gas flow required for ionization is secured when the sample solution is sprayed at the opening. The opening and the gas supply chamber, and the pipe support and the gas supply chamber have a fitting structure. The displacement of each position is determined by the processing accuracy of the fitting part, but the error is within an allowable range. Therefore, there is no need for adjustment at the time of assembly, and the assembly can be performed at an appropriate position each time. As a result of these structures, it is possible to always carry the capillary to the center of the opening.

[0026]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows an external view of a liquid chromatograph (LC) direct mass spectrometer (hereinafter abbreviated as LC / MS). The LC direct mass spectrometer is a device for measuring a trace amount of an organic compound dissolved in a liquid with high sensitivity. The sample is separated for each component by the LC system 41. The effluent from the LC system is guided to the atmospheric pressure ionization section 42 through the Teflon tube 26 and ionized. The atmospheric pressure ionization section 42 is connected to the atmosphere and is maintained at the atmospheric pressure. The ions ionized by the atmospheric pressure ionization section 42 are guided to the mass separation section 43 and subjected to mass separation. Mass separation unit 4
Numeral 3 is divided into a vacuum portion and an intermediate pressure portion, and is evacuated by a vacuum pump. The vacuum pump is stored in the pump section 44. As described above, since all the components including the two types of vacuum pumps 22 and 25 (the turbo molecular pump 22 and the scroll pump 25) are arranged in the apparatus, the noise is excellent. The cover 49 of the ionization chamber
Slide open and close to the right as viewed from the front of the device. The upper part of the apparatus is flat and mounts a liquid chromatograph (LC) 41. In this way, the device has a role as a table for placing the LC.

Although details will be described later, in this device,
Three types of ion sources can be used, and any one of them is mounted in the room of the atmospheric pressure ionization unit 42 for measurement. At the time of measurement, an organic solvent is sprayed and vaporized, and a high voltage of several kV is applied to the ion source.

All three sources are obtained from a common connector in the chamber of the atmospheric pressure ionization section 42. Therefore,
By detecting the connection state of unused connector pins and determining which connector pin is connected, the type of the attached ion source is determined. The result of the determination is reflected on the setting screen of the measurement parameters of the ion source, and a setting screen corresponding to each detected ion source is output.

The product is shipped in the following order: 1) assembly → 2) shipping test → 3) disassembly → 4) transport → 5) on-site assembly → 6) on-site performance evaluation. In a mass spectrometer, when parts having a large size and weight, such as a pump and a transformer, are separated from the main body, the labor required for the disassembly operation and the assembly operation becomes large. If there are many dismantled parts, the amount of work required for disassembly and assembly is large, and it takes time and labor costs. Also, since the number of cables and the like connecting these components increases, the number of components to be transported also increases, and it is necessary to check whether all the components are present, and there is a risk of loss. Further, by performing disassembly → assembly, the performance of the apparatus is affected, and adjustments need to be made, so that the time required for on-site performance evaluation also increases.

For this reason, the pumps 22 and 25 are removed,
Other parts can be transported as they are. Simply connecting to a power cable, a communication cable, and an exhaust duct device enables the device to operate. The pumps 22 and 25
Introduce into the body from the front part of the body. In this way, by shipping in the state at the time of the shipping test, it is possible to greatly reduce the time required for disassembly → assembly → on-site performance evaluation.

FIG. 1 shows the overall configuration of the LC / MS. The mobile phase solvent stored in the solution bottle 1 is sent to the separation column 4 via the inlet 3 by the pump 2. The sample is introduced from the injection port 3 by a micro syringe or the like. The introduced sample is separated for each component while traveling through the separation column 4. The separated components are sent to the ionization chamber 20 via the Teflon tube 26 together with the mobile phase solvent.
An ion source for LC / MS is stored in the ionization chamber. There are various ion sources, such as electrostatic spray ionization (ESI) and atmospheric pressure chemical ionization (AP).
CI) and Sonic Spray Ionization (SSI)
The method can be selected. Here, an example in which the SSI is connected is shown. In SSI, a sample component solution is exposed to a substantially sonic gas and becomes a mist. At this time, the sample components become charged droplets. The generated charged droplets are removed from the desolvation cover 6.
To remove the solvent.

Here, the case where the ESI is connected will be described. The sample component solution that has left the separation column 4 is sent to an ESI probe to which a high voltage has been applied. It is sprayed from the probe tip into the atmosphere as a charged droplet. The droplet repeatedly collides with atmospheric molecules, the diameter of the droplet is reduced, and ions are finally released into the atmosphere. When the APCI is connected, the sample is sprayed and ionized by corona discharge.

The ions generated in the ionization chamber 20 pass through the pores 7 and pass through the first intermediate pressure chamber (1 Torr) lower than the atmospheric pressure.
Degree). Further, the gas is guided to the second intermediate pressure chamber (about several mTorr) lower than the first intermediate pressure chamber through the fine holes 9. Further, it is guided to a high vacuum mass spectrometry chamber 21 (about 10 −5 Torr) through the pores 11.

The ions introduced into the mass spectrometry chamber 21 are sent to the quadrupole space 24 via the ion guide 8. The quadrupole space 24 is formed by being surrounded by two end cap electrodes 13 and 15 and one donut-shaped ring electrode 14. These electrodes are kept electrically insulated from each other by spacers made of glass or ceramic. The cross sections of these three electrodes 13, 14, 15 are hyperbolic. The ions sent into the quadrupole space 24 are the ring electrodes 1
4 is stably captured in the quadrupole space 24 by the high frequency of about 1 MHz applied to the four.

The ion trap mass spectrometer can integrate ions in the quadrupole space 24 while introducing ions. This is a factor that allows an ion trap mass spectrometer to provide better sensitivity than mass spectrometers based on other principles. The ions stored in the electrode are opened at the center of the end cap electrode 15 by changing the high-frequency voltage (amplitude) applied to the ring electrode 14 and are discharged out of the trap through the hole 23. The emitted ions are detected by the detector 16 and the data processor 17 obtains a mass spectrum. The mass spectrum is displayed on the display 19.

The second intermediate pressure chamber is evacuated by a scroll pump 25. On the other hand, the first intermediate pressure chamber 8 is
Since the first intermediate pressure chamber 8 is connected to the intermediate pressure chamber by the small hole 31, the pressure is maintained higher by the conductance than the second intermediate pressure chamber.

The mass spectrometer 21 is a turbo molecular pump (TM)
P) Evacuated by 20. Thus, the mass spectrometry chamber 21 is kept at a high vacuum. The back pressure of the TMP 20 is exhausted by the scroll pump 25.

Next, the details of the ion source will be described with reference to FIG. 3 using SSI as an example. The liquid sample from the separation column 4 is introduced into the gas supply chamber 51 through the fused silica capillary 58 through the Teflon tube 26.
Although the fused silica capillary 58 is fed through the stainless steel pipe 56, the tip of the fused silica capillary 58 needs to be maintained near the center of the opening without contacting the capillary cover 59. Here, the tip position of the fused silica capillary 58 is determined by the position of the stainless steel pipe 56. The position of the stainless steel pipe 56 on the opening side is fixed by a pipe support 57. The pipe support 57 has a cylindrical shape having a central hole for fixing the pipe and a hole for allowing nitrogen gas to pass through the opening around the central portion. Since it is in contact with the inner circumference, it is fixed at a predetermined position in the gas supply chamber 51. As a result, the stainless steel pipe 56 is also fixed at a predetermined position with respect to the gas supply chamber. Further, the capillary cover 59 has a disk shape having an opening (hole) at the center thereof, and its outer periphery is in contact with the inner periphery of the gas supply chamber 51, so that the capillary cover 59 is located at a predetermined position with respect to the gas supply chamber 51. Fixed. As a result, the positional relationship between the stainless steel pipe 56 and the opening of the capillary cover 59 is always constant. As described above, since the position of the tip of the fused silica capillary 58 is determined by the stainless steel pipe 56, the tip of the fused silica capillary 58 can be maintained at the center of the opening of the capillary cover 59. The liquid sample sent through the fused silica capillary 58 is sprayed at a substantially sonic speed at the opening of the capillary cover 59 by the nitrogen gas introduced from the nitrogen gas inlet 52. In this manner, the liquid sample is exposed to substantially the speed of sound and ionized. A hole is formed in the pipe support 57 so that the nitrogen gas is sent to the opening of the capillary cover 59, and the gas flow required for ionization is sufficiently obtained at the opening. The sample is ionized by spraying, and at the same time, is subjected to desolvation.

The sample ionized by the ion source 5 is desolvated by the desolvation cover 6 and led to the first intermediate pressure chamber. An ion passage 61 is formed in the desolvation cover 6 so as to extend from the ion source 5 toward the pore 7. A heater 62 passes through the inside of the desolvation cover 6. Heater 62
Due to the heat generated, the solvent removal cover 6 is kept at a high temperature. Also,
A guide 60 is provided so as to surround the outlet of the ion passage 61 on the side of the fine hole 7.

The details of the desolvation cover 6 will be described with reference to FIG. The desolvation cover 6 is for preventing the temperature of the pores 7 from lowering especially when the flow rate of the solution is increased. In particular, a heater 62 is mounted inside to effectively prevent the temperature from lowering. The generated ions pass through the ion passage 61.
And diffuses from the opening to the pores 7. Therefore, how to suppress the diffusion of ions and efficiently pass the generated ions through the pores 7 affects the performance of the apparatus.
Therefore, a guide 60 is provided around the ion passage 61,
Suppresses the diffusion of ions through the holes in the cover. The distance between the solvent removal cover 6 and the pores 7 is very short,
If there is only a small gap between the gap and the pores 7, diffusion of ions reaching this space is suppressed, and ions are efficiently introduced into the pores 7.

Next, the connection between the Teflon tube 26 and the fused silica capillary 58 will be described with reference to FIG. The effluent of the separation column 4 is led to a Teflon tube (outer diameter 1/16 inch) 26. On the other hand, in the SSI, a sample solution is introduced into the silica capillary 58 and the solution is sprayed from the tip. For these connections, the fused silica capillary 58 is passed through the Teflon tube 26, and both are fastened together using a ferrule 65. Since the Teflon tube 26 is deformed by the ferrule 65 and holds down the fused silica capillary 58, the fused silica capillary 5
8 is not easily removed. Fused silica capillary 58
As a means for connecting (fixing) the Teflon tube 26 and the Teflon tube 26, an adhesive can also be used. However, in this case, there is a problem that components in the adhesive are eluted by the introduced solution. It is also conceivable that the bonded portion becomes weak due to aging. On the other hand, in the joint fastening using ferrule 65,
Since the contact between the silica capillary 58 and the Teflon tube 26 is sufficient and the contact with other members can be avoided, the problem of contamination of the solution from the outside can be avoided. Further, the exchange of the fused silica capillary 58 and the Teflon tube 26 is easy, and the maintainability is improved.

Further, the ionization unit 20 and the mass spectrometer 2
Details of 1 will be described with reference to FIG. The small hole 31 of the scroll pump 25 is connected to the branch part 36. One of the branch portions is connected to the intermediate pressure chamber (first intermediate pressure chamber 8). The other branch is connected to TMP34. As a result, the scroll pump 25 exhausts the back pressure of the TMP 34.

The heater 6 of the SSI desolvation cover 6
In order to heat 2, it is necessary to supply a voltage,
This is achieved by connecting the connector 35 and the connector 38. That is, the voltage of the external power supply is supplied to the connector 35, and the connector 38 is connected to the connector 35.
Is supplied to the heater 62 via the. The connector 35 (38) supplies a voltage to the heater 62 and has another function. That is, it has a function of determining which type of interface is connected (ESI, APCI or SSI).

The determination of the ion source will be described with reference to the circuit diagram of FIG. As shown in FIG. 7 (a), the connector 35 (38) is provided with eight pins, of which the pins and the pins are connected to the power source of the heater 62. On the other hand, the pins 〜 are connected to the data processing device 17 via the determination circuit 70, and the type of the ion source is determined.
The connector 38 is pre-configured to jump one and / or and / or one set. For example, in the case of SSI, as shown in FIG. 7, the connector 38 is devised so that the pins are connected. Therefore, a current flows through the photocoupler 73, and the potential of the line (C) becomes zero. On the other hand, since the pins are not connected, no current flows through the photocouplers 71 and 72, and the potentials of the lines (A) and (B) become V. These lines (A) to (C) are connected to the data processing device 17 respectively. Here, in the data processing device 17, FIG.
As shown in (b), when D0 (line A) is High, D1 (line B) is High, and D2 (line C) is Low, it is determined that the SSI is connected. The data processing device 17 sends necessary signals to each unit based on this determination. As shown in FIG. 7B, the data processing device 17 determines that the connector 38 is APCI if the pin is connected to the pin, and determines that the connector 38 is ESI if the pin is connected to the connector 38. The result of the determination is reflected on the setting screen of the measurement parameters of the ion source, and a setting screen corresponding to each detected ion source is output. For safety reasons, the ionization chamber is covered with a cover 49, and the mechanism cannot perform measurement unless the cover 49 is closed. On the other hand, it is difficult for a measurer to confirm which ion source is attached during measurement, but the type of ion source is displayed on the device display unit 50 and the display 19, so that it is easy. The type of the ion source can be determined.

[0045]

As described above, according to the present invention,
The analysis accuracy is improved, and accurate analysis becomes possible. Also, preferably, the time required for assembling the sonic spray-on source can be greatly reduced. Also, an ion source with stable performance can be obtained regardless of the skill of the assembly operator, and anyone can perform the disassembly and assembly work, thereby improving the maintainability of the apparatus.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an embodiment of the present invention.

FIG. 2 is an external view of the embodiment.

FIG. 3 is a diagram showing details of an ion source.

FIG. 4 is an explanatory diagram of an ion source.

FIG. 5 is a diagram for explaining the connection between the liquid chromatograph and the mass spectrometer.

FIG. 6 is a diagram showing details of an ionization chamber and a mass spectrometry chamber.

FIG. 7 is a view for explaining selection determination of an ion source.

[Explanation of symbols]

4 separation column, 5 ion source, 10 second intermediate pressure chamber, 17 data processing device, 21 mass spectrometry room, 22
Turbo molecular pump, 25 Scroll pump, 31 Small hole, 35, 38 Connector, 51 Gas supply chamber, 52
Nitrogen gas inlet, 56: stainless steel pipe, 57: pipe support, 58: fused silica capillary, 59: capillary cover, 63: guide.

Claims (6)

[Claims] 1. An ionization means for ionizing a sample, and a mass spectrometer for mass spectrometric analysis of said ions, wherein said ionization means can be replaced with different types of ionization, and has means for judging the type of said ionization means. A mass spectrometer characterized by the above-mentioned. A first chamber having a pressure lower than a pressure for ionizing the sample; and a second chamber having a pressure lower than the pressure of the first chamber, wherein the ionized sample is supplied to the second chamber through the first chamber. Lead to the room,
Mass separation of the ions in the second chamber or the second
In a mass spectrometer for introducing ions to a chamber having a lower pressure through a chamber and performing mass separation, a first pump for exhausting the first chamber and a second exhaust pump for exhausting the second chamber Wherein the back pressure of the second pump is exhausted by the first pump. 3. A mass spectrometer for ionizing a sample and introducing the ionized sample to a high vacuum high vacuum chamber for mass separation, the mass spectrometer having exhaust means for exhausting the high vacuum chamber, The mass spectrometer, wherein the exhaust means is housed in the same casing. 4. A mass spectrometer having a liquid chromatograph for column-separating a sample and mass spectrometry means for mass-analyzing an effluent from the liquid chromatograph, wherein a tube to which the effluent of the liquid chromatograph is supplied is provided. A mass spectrometer, wherein the effluent of the tube is supplied to the mass spectrometry means via a capillary, the capillary is inserted into one end of the tube, and the outer periphery of the tube is pressed. 5. A mass spectrometer having ionization means for ionizing a sample and mass separation means for mass separating the ions, wherein a member which partially forms a passage between the ionization means and the mass separation means is provided. And a projection that projects from the member toward the mass analysis unit. 6. A capillary for introducing a liquid sample, a gas supply chamber for supplying a substantially sonic gas around the tip of the capillary to ionize the liquid sample at the tip of the capillary, and massaging the ionized sample. In a mass spectrometer having an analysis unit for separation, a support is provided so that a part of the outer periphery is in contact with the gas supply chamber and the tip of the capillary is maintained at a predetermined position. A mass spectrometer comprising a capillary cover arranged so as to be in contact with a portion of the capillary so that the opening surrounds the tip of the capillary so as not to contact the tip of the capillary.