JPH0754691B2 - Ion source for mass spectrometer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ion source for a mass spectrometer of a type in which a primary beam is irradiated and ionized by the impact thereof, and in particular, a sample solution from a liquid chromatograph is used in an ionization chamber. The present invention relates to an ion source suitable for use in the case of being directly introduced into and ionized.

[Prior Art] As an ion source of a type in which a sample liquid separated by a liquid chromatograph is directly introduced into a mass spectrometer, a structure shown in FIG. 3 is described in Japanese Utility Model Publication No. 61-116065.

In FIG. 3, 1 is a mass analyzer of the mass spectrometer, 2 is an ion source, 3 is an ionization chamber, 4 is an electrode group for accelerating and focusing the ions generated in the ionization chamber, and 5 is a primary particle beam generator. , 6 is a liquid chromatograph, and 7 is an introduction tube for introducing the sample liquid separated by the liquid chromatograph 6 into the ionization chamber 3. A fused silica tube is used as the introduction tube. Further, the distal end portion of the introduction tube 7 inserted into the ionization chamber is covered with a stainless steel tube 8 as shown in the enlarged sectional view of FIG. 4, and further, a glass tube (a metal such as stainless steel may be used) outside thereof. 9 is covered. A disk-shaped porous member 10 is attached so as to close the opening of the introduction tube. As this porous member, for example, a filter (frit) made by sintering stainless powder is used. An appropriate voltage is applied to the stainless steel tube 8 from a repeller power supply 11.

In such a configuration, the sample liquid separated by the liquid chromatograph 6 is sequentially introduced into the ionization chamber 3 through the introduction pipe 7, and exudes to the surface through the porous member 10 attached to the tip of the introduction pipe. To do. The sample liquid exuded on the surface is impacted by the primary particle beam B from the particle beam generator 5 and ionized, and the generated ions I are introduced into the mass spectrometric unit 1 for mass analysis.

In such an apparatus, it is necessary to supply the sample solution to the porous member at a solution sending rate such that the sample solution sent to the porous member is not completely ionized in order and remains on the surface of the porous member. With this device, the appropriate amount of liquid to be delivered is so small that it is difficult to control it accurately at the current technical level.
It is unavoidable that a large amount of sample liquid is sent to the porous member beyond the appropriate liquid sending speed. Then, the so-called memory phenomenon occurs in which the sample component sent earlier remains unionized and is ionized together with the sample component sent later, which adversely affects the analysis.

Therefore, in order to solve such a problem, an ion source as shown in FIG. 5 has been recently proposed.

In this ion source, an envelope (cap) 13 having an opening 12 defining the exudation area of the sample liquid on the surface of the porous member 10 is closely covered with the porous member, and the sample liquid exuded in the opening. Are ionized by primary beam irradiation. Reference numeral 14 is a positioning member for fixing the introduction pipe 7 in the cap 13.

By doing so, the sample liquid sent to the porous member is divided into the opening and the other portion and exudes, and the sample liquid exuding from the surface other than the opening is taken out into the cap. Therefore, even if a large amount of the sample liquid is sent to the porous member, the amount of the sample that exudes to the area of the opening irradiated with the primary beam B can be suppressed, and the occurrence of the memory phenomenon can be prevented.

[Problems to be Solved by the Invention] However, even if such a proposed method is adopted, the memory phenomenon cannot be completely prevented. This is a cap
It has been clarified that the cause is that the edge portion of the opening 13 of 13 and the primary beam irradiation surface of the porous member 10 are in close contact with each other. In other words, the sample liquid that has exuded to the central portion of the opening spreads radially to the periphery along the surface, once gathers at the peripheral portion of the opening, then flows into the porous member again and is discharged inside the cap. Therefore, the primary beam is irradiated on the sample liquid accumulated in the peripheral portion A of the opening, and the memory phenomenon occurs accordingly.

Therefore, the present invention has been made in view of the above points, and an object of the present invention is to provide an ion source capable of preventing the sample solution from accumulating in the peripheral portion of the opening of the cap with a simple configuration. .

[Means for Solving the Problems] In order to achieve the above object, the ion source of the present invention has an introduction tube for introducing a sample solution into the ionization chamber from the outside, and a porous material attached to the tip of the introduction tube. Member, means for generating a primary beam that irradiates the sample liquid that has passed through the porous member and exudes to the surface thereof, and irradiation of the primary beam on the primary beam irradiation surface of the porous member that is covered with the primary beam An envelope having an opening defining a region; and a ring-shaped spacer interposed between the opening edge portion of the envelope and the surface of the porous member and having an inner diameter larger than the size of the opening, It is characterized in that the spacer or the porous member is provided with a notch for allowing the sample liquid leached on the surface of the porous member to escape to the inside of the enclosure.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[Embodiment] FIG. 1 is a partial sectional view showing the structure of an embodiment of the present invention, and the same reference numerals as those in FIG. 5 indicate the same constituent elements.

In FIG. 1, reference numeral 15 is a spacer for forming a gap G without bringing the edge portion of the opening 12 of the cap 13 and the surface of the porous member 10 on which the primary beam B is irradiated into close contact with each other, and this spacer is fixed to the cap. Further, this spacer is formed in a ring shape having an inner diameter larger than the size of the opening 12 as shown in FIG. 2, and further, four notches 16a.6b, 16c, 16d is provided. Each notch is formed so that the bottom thereof protrudes beyond the outer periphery of the porous member 10. The cap 13 is a porous member.
It is screwed to the member 14 so that the 10 can be easily replaced.

By doing so, the sample liquid that has exuded from the central portion of the porous member 10 and diffused to the peripheral portion is discharged to the inside of the cap 13 through the notches 16a to 16d of the spacer 15. Therefore, the sample liquid does not collect in the peripheral portion of the opening 12 as in the conventional case, so that the memory phenomenon can be completely prevented. Here, the sample solution is collected in the inner portion C of the spacer 15, but since this portion is located farther than the edge portion of the opening 12, the primary beam B is blocked by the cap 13 and is not irradiated.

The above description is an example of the present invention, and various modifications can be considered in the implementation. For example, the number of notches formed in the spacer is not limited to four, and one or two or more may be formed.

Further, in the above embodiment, the sample liquid exuded on the surface of the porous member is allowed to escape to the inside of the cap through the notch formed in the spacer, but the present invention is not limited to this, and as shown in FIG. 6, for example. Even if the notches 17a, 17b, 17c, 17d are formed in the porous member 10, the same effect can be obtained. In this case, it goes without saying that the bottom of the notch is formed so as to protrude inside the inner diameter of the spacer.

[Effect] As described in detail above, according to the present invention, an ion source for a mass spectrometer capable of completely preventing a memory phenomenon is realized.

[Brief description of drawings]

FIG. 1 is a partial sectional view showing the structure of an embodiment of the present invention, FIGS. 2 and 6 are views showing a spacer used in the present invention, and FIGS. 3 to 5 are explanations of conventional examples. FIG. 1: Mass spectrometric section, 2: Ion source 3: Ionization chamber 5: Primary particle beam generator 6: Liquid chromatograph 7: Introduction tube, 10: Porous member 12: Opening, 13: Cap 15: Spacers 16a, 16b, 16c, 16d: Notch

Claims (1)

[Claims] 1. An introduction tube for introducing a sample solution into the ionization chamber from the outside, a porous member attached to the tip of the introduction tube, and a sample solution leached on the surface of the porous member through the porous member is irradiated. Means for generating a primary beam, an enclosure having an opening which covers the porous member and defines an irradiation area of the primary beam on the irradiation surface of the primary beam of the porous member, and an opening edge portion of the enclosure. And a ring-shaped spacer interposed between the porous member surface and the porous member surface and having an inner diameter larger than the size of the opening, and the sample liquid exuded on the porous member surface escapes to the inside of the enclosure. An ion source for a mass spectrometer, characterized in that a notch for forming is formed in the spacer or the porous member.