JPH0429181B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an ion source for a mass spectrometer that irradiates a sample with a primary particle beam and ionizes the sample by the impact, and particularly relates to an ion source for a mass spectrometer that ionizes the sample with a primary particle beam. It provides an effective ion source when a sample solution is directly introduced into the ionization chamber and ionized.

[Prior Art] As a method for directly introducing a sample solution separated by a liquid chromatograph into a mass spectrometer, a structure shown in FIG. 4 is used.

In the figure, 1 is a mass analysis section of a mass spectrometer, 2 is an ion source, 3 is an ionization chamber, 4 is a group of slits that accelerate and focus the ions generated in the ionization chamber 3, and 5 is a particle beam generator. 6 is a liquid chromatograph, and 7 is an introduction tube for introducing the sample solution separated by the liquid chromatograph 6 into the ionization chamber 3, which is removably attached to the outer wall of the ion source 2 in a substantially horizontal state. It is being As this introduction tube, for example, a fused silica tube with an inner diameter of about 40 μm is used. Further, as shown in FIG. 5, which is an enlarged cross-sectional view of the introduction tube 7 inserted into the ionization chamber 3, a stainless steel tube 8 is placed over the tip, and a glass tube (a metal tube such as stainless steel tube may also be used) 9 is placed on the outside of the stainless steel tube 8. is covered. A porous member 10 is attached so as to close the opening of the introduction pipe. Examples of this porous member include filters (frits) made by sintering stainless steel powder.
is used. Incidentally, an appropriate voltage is applied to the stainless steel tube 8 from a repeller power source 11.

In this configuration, the sample solution separated by the liquid chromatograph 6 is sequentially introduced into the ionization chamber 3 through the introduction tube 7, seeps out onto the surface of the porous member 10 attached to the tip of the introduction tube, and is introduced into the particle beam generator 5. It is ionized by being irradiated with the primary particle beam B from the source. The generated ions are pushed out of the ionization chamber 3 by a repeller voltage applied to the stainless steel tube 8, introduced into the mass spectrometer 1, and subjected to mass analysis.

[Problems to be Solved by the Invention] When introducing the sample solution from the liquid chromatograph into the ion source online in this way and sending the sample solution to the porous member 10 for ionization, the sent sample All components are sequentially ionized,
Although it is desirable that no previously sent sample components remain, in reality, it is unavoidable that sample components that are not ionized accumulate at the bottom of the porous member 10, as shown by the symbol S in FIG. As a result, the sample component S accumulated at the lower end of the porous member is also irradiated with the primary particle beam B, and the resulting ions are introduced into the mass spectrometer and subjected to mass analysis.
Therefore, the sample components sent later and the sample components sent earlier are simultaneously ionized and subjected to mass spectrometry, which adversely affects the analysis.

Therefore, the present invention has been made in view of this point, and a shielding member is arranged on the primary particle beam irradiation surface to prevent the primary particle beam from irradiating the sample liquid that exists on the irradiation surface without being ionized. The purpose is to provide an ion source that can prevent

[Means for Solving the Problems] In order to achieve the above object, the present invention introduces an introduction tube into the ionization chamber in a substantially horizontal state, and applies this to the irradiation surface provided at the tip of the introduction tube. In an ion source for a mass spectrometer that supplies a sample liquid through an introduction tube and ionizes the sample liquid by irradiating the irradiated surface with a primary particle beam, particles that remain on at least the lower surface of the irradiated surface without being ionized at the irradiated surface. The present invention is characterized in that a shielding member is provided to prevent the sample liquid from being irradiated with the primary particle beam.

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

[Embodiment] FIG. 1 is an enlarged sectional view of a main part showing an embodiment of the present invention, and the same reference numerals as in FIGS. 4 and 5 indicate the same components.

In the figure, reference numeral 12 denotes a shielding body formed in the shape of a cylinder with a bottom, and this shielding body is arranged so as to surround the outside of the porous member 10 with a certain interval maintained between several supports 13a, It is attached to the glass tube 9 via 13b... Moreover, the open end 12a of this shield penetrates the side wall of the ionization chamber 3 and is taken out into the ion source 2. Furthermore, this shield 1
A primary particle beam passage hole 14 is formed in the center of the bottom portion 12b of 2. A sharp protrusion 15 is provided at the edge of the hole 14 toward the inside of the shield 12 (toward the porous member 10 side), and the tip of this protrusion is the primary particle beam irradiation surface of the porous member 10. is in contact with.

If done in this way, the hole 1 formed in the shielding body 12
Only the primary particle beam B that has passed through the porous member 10 reaches the porous member 10, and the remaining primary particle beams are blocked by the shield, so that the area irradiated by the primary particle beam of the porous member is limited to the center of the porous member. be able to. As a result, the sample solution in the area irradiated by the primary particle beam of the porous member is efficiently ionized, so that only new sample solution always exists on this irradiation surface without any unionized sample solution remaining. In addition, the sample solution on the surface of the porous member 10 in an area other than the irradiation area is denoted by S in the figure.
As shown in , due to the capillary phenomenon that occurs in the gap between the porous member 10 and the bottom portion 12b of the shielding body 12, it flows to the lower part of the shielding body and is accumulated therein, or it is accumulated in the periphery of the porous member 10.

Here, in this embodiment, the open end 12 of the shield 12
Since a is discharged to the outside of the ionization chamber, the vaporized gas from the sample solution stored in the shielding body is discharged to the outside of the ionization chamber. As a result, vaporized gas from the sample solution within the shielding body flows into the ionization chamber 3, thereby making it possible to prevent electrical discharge and the like caused by an increase in the pressure within the ionization chamber. In addition, the shield 1
By forcibly discharging the sample solution accumulated in the shield 2 using a pump or the like, cleaning of the shield can be made unnecessary. Furthermore, if the distance between the bottom part 12b of the shielding body and the surface of the porous member 10 is made very small to cause a capillary phenomenon, or if a sponge, metal mesh, etc. Since the excess sample solution that oozes out can be forcibly sucked up and discharged to the lower part of the shielding body 12, it is possible to completely eliminate the accumulation of unionized sample solution on the primary particle beam irradiation surface of the porous member. .

FIG. 2 is an enlarged cross-sectional view of a main part showing another embodiment of the present invention, and FIG. 3 is an enlarged view taken in the direction of arrow A. The same numbers as in FIG. 1 indicate the same components.

In this embodiment, the lower end of the porous member 10, that is, the part where the sample solution that is not ionized on the surface of the porous member easily flows down and accumulates, as shown by the symbol S in FIG. 2, is a plate-shaped shield 16. It is characterized by being shielded by. This shield 16 is fixed to a sample solution storage container 17 attached to the bottom of the glass tube 9.

If this is done, only the part where the unionized sample solution accumulates will be shielded by the shielding body 16, so the amount of primary particle beam B irradiated to the porous member will increase, the amount of ions will increase, and the sensitivity will be improved. .

It should be noted that the above description is an example of the present invention, and many modifications can be made when implementing the present invention. For example, the porous member, the glass tube, or the stainless steel tube may be heated in order to accelerate the evaporation of the solvent component in the sample container that seeps out from the porous member or to increase the amount of generated ions.

In addition, a porous member was attached to cover the irradiation surface, or opening, where the primary particle beam of the introduction tube introduced into the ionization chamber is irradiated, but this is not necessarily necessary, and the porous material is directly attached to the opening of the introduction tube. The primary particle beam may be irradiated to sequentially ionize the sample components that are sent.

In addition, although the above example shows the case where the liquid chromatograph and the ion source are connected online,
The present invention is not limited to this, and the same method can be applied to off-line analysis of a single sample component.

[Effects] As detailed above, according to the present invention, it is possible to prevent the sample liquid that has not been ionized on the primary particle beam irradiation surface provided at the tip of the introduction tube from being irradiated with the primary particle beam. It is possible to prevent the sample liquid sent first and the sample liquid sent later from being ionized together, improving analysis accuracy, and at the same time, it is possible to prevent the sample liquid sent earlier and the sample liquid sent later from being ionized together. It is also possible to increase the amount introduced into the cell, and it is possible to improve the sensitivity.

[Brief explanation of drawings]

FIG. 1 is an enlarged cross-sectional view of a main part showing one embodiment of the present invention, FIG. 2 is an enlarged cross-sectional view of a main part showing another embodiment of the present invention, and FIG. 3 is an enlarged view taken in the direction of arrow A in FIG. , FIG. 4, and FIG. 5 are diagrams for explaining conventional examples. 1...Mass spectrometry diagram, 2...Ion source, 3...Ionization chamber, 4...Slit group, 5...Particle beam generator, 6...Liquid chromatograph, 7...Introduction tube, 8...Stainless steel Tube, 9...Glass tube, 10
... Porous member, 11 ... Repeller power supply, 12,1
6... Shielding body, 12a... Open end, 12b... Bottom, 13a, 13b... Support stand, 14... Hole, 1
5...Protrusion, 17...Container.

Claims (1)

[Scope of Claims] 1. Introduce the introduction tube into the ionization chamber in a substantially horizontal state, supply the sample liquid through the introduction tube to the irradiation surface provided at the tip of the introduction tube, and apply a primary injection to the irradiation surface. In an ion source for a mass spectrometer that ionizes a sample liquid by irradiating a particle beam, preventing the primary particle beam from irradiating the sample liquid that is not ionized on the irradiation surface and remains at least on the lower surface of the irradiation surface. An ion source for a mass spectrometer, characterized in that it is provided with a shielding member for the purpose of 2. Claim 1, characterized in that the shielding member is formed into a cylindrical shape with a bottom to cover the irradiation surface of the tip of the introduction tube, and a hole is provided at the bottom of the shielding member to allow the primary particle beam to pass through. The ion source for the mass spectrometer described in Section 1.