JPH01298636A - Sample introducing probe in mass spectrograph - Google Patents

Abstract

PURPOSE:To make decomposing cleaning of a probe needless for easy handling by supporting a male screw body on a collar of a sample leading-in probe with thin supporting rods of a low thermal conductivity material. CONSTITUTION:A male screw body 12 is not directly fixed to a collar 11 being instead supported with four thin supporting rods from 21a to 21d of a material such as the low thermal conductivity stainless steel. The screw 12 is formed of a material having bad thermal conductivity and a gap is made on the window part of a transfer tube 19 so that the screw 12 may not directly touch the transfer tube 19. In this way, the heat of a holder 15 is not transferred to the collar 11 so as to prevent temperature rise of the transfer tube 19, a solvent component is not vaporized halfway but vaporized immediately before a porous member 14 and a sample component is not stuck to the transfer tube 19 instead for being vaporized after reaching the member 14. Thereby the transfer tube 19 is prevented from being heated and the solvent component in a sample liquid is prevented from being vaporized halfway to stick the sample component to the transfer tube for being stopped up so that a probe 9 is not needed to be decomposed for cleaning so as to extremely simplify handling.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a sample introduction probe suitable for directly introducing a liquid sample into an ion source and ionizing it by chemical ionization, electron bombardment, or primary beam bombardment. be.

[Prior Art] Recently, a structure as shown in Figure 3 has been proposed as a sample introduction probe that directly introduces and ionizes a sample liquid developed in a liquid chromatograph into the ion source of a mass spectrometer. There is.

In the figure, 1 is an ion source housing whose inside is kept in a high vacuum, 2 is a lid thereof, and 3 is an El ionization box, and an electron entrance port 4 and an electron exit port 5 are opposite to each other on the outer periphery of this ionization box. It is shaped like this. 6 is a filament for generating an electron beam; 7 is a group of electrodes for extracting, accelerating and focusing the ions I generated in the El ionization box; The electrode 7a is fixed to the end of the EI ionization box and serves as a lid, and a hole 8 for ion passage is provided in the center of the electrode. Furthermore, these electrode groups and E
Ionization sheath box 3 is fixed to the ion source housing 1.

Reference numeral 9 denotes a cylindrical sample introduction probe that is introduced into the ion source housing 1 through a cylindrical guide body 10 provided on the lid 2, and one end of this probe (on the ion source housing 1 side) is electrically insulated. A male screw body 12 is fixed with a material collar 11 interposed therebetween, and a knob 13 is provided at the other end. A holder 15 holding a porous member 14 is screwed onto the male screw body 12 . A bottomed cylindrical CL ionization sheath box 16 is threaded onto this holder 15 so as to house a porous member, and this holder and CI ionization box are movable within the EI ionization sheath box 3. inserted into.

An opening 1 for introducing electrons is provided on the outer periphery of the CI ionization box 16.
7, and an ion exit port 18 is formed at the bottom. The opening 17 and the ion exit port 18 are formed small in order to maintain a relatively high pressure suitable for the CI ionization sheath box 16CI.

Reference numeral 19 denotes a transfer tube inserted into the probe 9 in an airtight manner, and a fused silica tube with a minute diameter is used as the transfer tube.One end of the transfer tube is connected to the porous member 14. It is attached so as to close its open end, and the other end is taken out into the atmosphere and connected to a liquid chromatograph (not shown).

A heating coil 20 is wound around the outer periphery of the EI ionization box 3, and is used to heat the porous member 14 to a desired temperature via the EI ionization box. Although not shown, an air lock valve is provided at the insertion portion of the lid 2 for the probe 9, so that the probe can be replaced without breaking the vacuum inside the ion source housing 1.

In this configuration, in the state shown in the figure, the electron entrance port 4 and the opening 17 coincide, and the electron beam from the filament 6 is introduced into the CI ionization sheath box 16. In this state, when the sample liquid developed by the liquid chromatograph is introduced to the porous member 14 via the transfer pipe 19, the sample liquid oozes out through the porous member to the surface thereof, and the solvent in the sample liquid is converted into a reaction gas. Chemical ionization takes place. That is, since the porous member 14 is maintained at a temperature (approximately several hundred degrees) at which the sample liquid to be analyzed is vaporized by the heating coil 20, the solvent (reactive gas) vaporized on the surface of the porous member first reaches the electron incidence port 4. and opening 1
The sample components are ionized by the electron beam incident from 7, and then the sample components are ionized by a chemical reaction with the solvent ions, and the generated sample ions I are sent to a mass spectrometer (not shown) through the ion exit port 18 and hole 8. Therefore, mass spectrometry using CI ionization can be performed.

Next, move the probe 9 to the left side and pull it out from the CI ionization sheath box 16 and El ionization box 3, and stop it at a position just before the bottom of the CI ionization box closes the entrance port 4 of the El ionization box. The vaporized sample liquid ejected from the ion exit port 18 is ionized by the impact of the electron beam passing through the EI ionization sheath box 3 from the electron entrance port 4 toward the electron exit port 5. Since the generated ions are sent to the mass spectrometer through the hole 8, mass spectrometry can be performed by electron impact ionization.

[Problems to be Solved by the Invention] By the way, if a sample introduction probe with such a configuration is used for a long time, the transfer tube 19 inside the probe becomes clogged, and each time the probe is disassembled and the inside of the transfer tube is cleaned or a new transfer tube is installed. It was very difficult to handle as it had to be replaced.

The inventor investigated this point and found that the cause was that the sample liquid became high temperature before flowing into the porous member 14. In other words, the porous member uses the holder 15 in order to vaporize the sample components seeped onto the surface of the porous member.
It is heated up to several hundred degrees by a heating coil.

At this time, ideally only the porous member should be kept at a high temperature, but in reality the heat of the holder is transmitted to the collar 11 via the male screw 12. Furthermore, the heat transferred to this collar is transferred to the transfer tube 19 placed inside the collar by radiant heat, so the temperature of the transfer tube in this part rises to a temperature at which the solvent component in the sample liquid vaporizes, for example, about 50 to 60 degrees Celsius. Resulting in. Due to this temperature rise in the transfer tube, the solvent component in the sample liquid is vaporized near the collar, that is, well in front of the porous member, and as a result, the sample component is centered on the inner wall of the transfer tube, and as time passes, This causes the transfer pipe to become clogged.

Therefore, it is an object of the present invention to solve this problem.

[Means for Solving the Problems] In order to achieve the above object, the ion source of the present invention includes an ionization box, a sample introduction probe whose tip is arranged in the ionization box so that it can be inserted and removed from the outside, and the probe. a porous member attached to a portion of the probe that is inserted into the ionization box; a transfer tube for transferring a sample liquid to the porous member through the inside of the probe; and a heating member for heating the porous member. and means for attaching the porous member to the probe in a heat-insulating manner.

Hereinafter, embodiments of the present invention will be explained in detail based on the drawings.

[Example] Fig. 1 is a cross-sectional view showing an example of a sample introduction probe used in the present invention, and Fig. 2 is an enlarged cross-sectional view taken along line AA in Fig. 1.
Components with the same reference numerals as in FIG. 3 indicate the same structural requirements.

The difference in this embodiment from the conventional example shown in FIG. 3 is that the color 1
For example, without directly fixing the male threaded body 12 to the
．． Four support rods 21a, 21b, 21c of about 6 mm,
This is the point supported in 21d. The male thread 12 is similarly made of a material with poor thermal conductivity, such as stainless steel, and a gap is formed in the part where the transfer pipe 19 passes through the male thread, so that the male thread does not come into direct contact with the transfer pipe. That's how it is.

Since the holder 15 kept at a high temperature is supported by several very thin support rods 214 to 21d, the heat of the holder 15 can be suppressed from being transferred to the collar 11. Therefore, since the temperature of the transfer pipe 19 can be prevented from rising, the solvent component is vaporized just before the porous member without being vaporized midway as in the conventional case. As a result, the sample components reach the porous member without being stuck to the transfer tube and are vaporized through the porous member.

It should be noted that the above description shows an example of the present invention, and many modifications can be made in implementing the present invention. For example, in the above embodiment, a thin support rod was used to prevent the heat of the holder from being transmitted to a portion of the collar, but the invention is not limited to this. A formed stainless steel cylinder may also be used.

In the above example, the sample liquid was ionized using El or CI, but the present invention is not limited to this. Alternatively, a probe with a porous member attached to the tip may be inserted into an ionization box, and the sample liquid may be ionized on the surface of the porous member. The sample liquid may be ionized by second beam irradiation.

[Effects] As detailed above, according to the present invention, it is possible to prevent the transfer tube placed inside the probe from being heated during the transfer, so that the solvent component in the sample liquid is It is vaporized during the process, which prevents sample components from sticking to the transfer tube and clogging it.

As a result, the probe does not need to be disassembled for cleaning or replaced with a new transfer tube, making handling much easier.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an example of a sample introduction probe used in the present invention, FIG. 2 is an enlarged cross-sectional view along line AA of FIG. 1, and FIG. 3 is a diagram for explaining a conventional example. 1: Ion source housing 3: E1 ionization box 4; Electron entrance port 5: Electron exit port 6: Filament 9: Sample introduction probe 11: Collar 12 = Male screw body 14: Porous member 15: Holder 16: CI ionization box

Claims (1)

[Claims] an ionization box; a sample introduction probe whose tip is disposed in the ionization box so that it can be inserted and removed from the outside; a porous member attached to a portion of the probe that is inserted into the ionization box; The porous member is provided with a transfer tube for transferring a sample liquid to the porous member through the inside thereof, and a heating means for heating the porous member, and the porous member is adiabatically attached to the probe. Characteristic sample introduction probe in mass spectrometer.