JPH0630238B2 - Ion source for mass spectrometer - Google Patents

Description

TECHNICAL FIELD The present invention relates to an ion source for a mass spectrometer capable of directly introducing a liquid sample into an ionization chamber and ionizing the sample by electron impact or chemical ionization.

[Prior Art] Recently, as a method of introducing a sample liquid developed by a liquid chromatograph into an ion source of a mass spectrometer to ionize it,
There are a belt method described in JP-A-52-11719 and a direct spray method described in JP-A-57-836.

[Problems to be Solved by the Invention] However, in the belt system, the vacuum holding mechanism for introducing the belt into the ion source becomes large-scale, and there is a problem of so-called memory effect due to contamination of the belt.

Further, the direct spraying method requires a very fine spraying nozzle, and the nozzle is also easily clogged, and there is a problem that it is difficult to stably introduce the sample solution into the ionization chamber.

The present invention has been made in view of the above points, and an object thereof is to provide an ion source capable of stably introducing a sample liquid into an ionization chamber and ionizing it with a simple configuration.

[Means for Solving Problems] In order to achieve this object, an ion source for a mass spectrometer according to the present invention has an ionization chamber and a tip portion inserted into the ionization chamber so that a sample solution is introduced into the ionization chamber from the outside. An introducing pipe to be introduced, a porous member attached to the outlet of the leading end of the introducing pipe to vaporize from the surface while allowing the sample liquid to pass therethrough, and for introducing an electron beam into the ionization chamber toward the vicinity of the surface of the porous member. It is characterized by comprising means and.

[Operation] The sample liquid introduced into the ionization chamber through the introduction tube and oozing to the surface through the porous member is vaporized and then ionized by electron impact. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[Embodiment] FIG. 1 is a sectional view showing an example of an embodiment in which the present invention is applied to an electron impact ionization type (EI) ion source. In FIG. 1, 1 is a mass analyzer of a mass spectrometer, and 2 is ionization. Room,
3 is a filament that generates an electron beam, 4 and 5 are electron entrances and exits that are opened in the ionization chamber 2, and 6 is a slit that takes out the ions generated in the ionization chamber 2 to the outside and accelerates and converges them. Electrodes, 7 are high performance liquid chromatographs, and 8 is an introduction tube for sending the sample liquid developed by the liquid chromatograph 7 to the ionization chamber 2. As the introduction tube 8, for example, a fused silica tube having an inner diameter of about 40 μm is used.

A stainless steel tube 9 is covered on the tip of the introduction tube 8, a glass tube 10 is covered on the outer side thereof, and a heater 11 for heating is further wound on the outer side thereof. And
The porous member 12 is attached so as to close the opening of the introduction tube 8. As this porous member, for example, a filter (frit) made by sintering stainless powder is used. In addition, the stainless steel tube 9 has a repeller power supply 13
Then, an appropriate repeller voltage is applied.

In the configuration as described above, the sample liquid developed by the liquid chromatograph is sent toward the ionization chamber 2 via the introduction pipe at a flow rate per hour according to the exhaust capacity of the ion source, for example, 5 μ / min. The sent sample liquid passes through the porous member 12 whose temperature is appropriately set by the heater 11 and gradually exudes to the surface thereof to be vaporized. At that time, in the vicinity of the surface of the porous member, the solvent in the sample liquid having a low boiling point is preferentially vaporized at a high speed, and the sample component having a high boiling point is vaporized relatively slowly. The concentration of sample components will increase. In this way
Due to the presence of concentrated sample components on the surface of the porous member,
In the vicinity of the surface of the porous member, the vaporized sample component is present at a relatively high concentration, and the vaporized sample component of this high concentration is subjected to the impact of the electron beam passing through the ionization chamber from the entrance 4 to the exit 5. Is ionized.

Since it is necessary to adjust the relative positional relationship between the electron beam and the surface of the porous member relatively rigorously, it is desirable to provide a mechanism for moving the porous member 12 in the front-back direction.

FIG. 2 is a sectional view showing an embodiment in which the present invention is applied to a chemical ionization (CI) ion source.
The point that the CI gas can be introduced through the chamber and that the electron entrance port 4 and the ion exit port are made small and the electron exit port 5 is eliminated in order to keep the ionization chamber at a relatively high pressure suitable for CI. Only the difference from the embodiment of FIG. 1 has the same structure as the other parts.

In this embodiment, the CI gas is first ionized by the electron beam introduced through the entrance 4, and then the vaporized sample component is ionized by the reaction with the CI gas ions.

FIG. 3 shows the configuration of an embodiment in which the present invention is applied to an EI / CI composite ion source, in which a small electron for CI is placed in an ionization chamber 2E equipped with a large electron entrance 4E and electron exit 5 for EI. An ionization chamber 2C having an entrance 4C is slidably inserted.

The state of FIG. 3 is the CI mode, and if the ionization chamber 2C is pulled out to the position indicated by the broken line and the CI gas introduction through the tube 14 is stopped, the electron beam passes between the entrance 4E and the exit 5. However, ionization in EI mode is possible.

In addition to the EI / CI composite ion source shown in FIG.
If a passage communicating with the outside is provided in the shaded portion A of the embodiment of FIG. 1 and the surface of the porous member is irradiated with the primary neutral beam or the ion beam through this passage, the EI results. A composite ion source capable of performing ionization and ionization by primary particle beam bombardment is realized.

[Effect] As described in detail above, according to the present invention, ions for a mass spectrometer capable of introducing and ionizing a liquid sample into an ionization chamber with a simple configuration in which a porous member is attached to the tip of an introduction tube. Source is realized.

[Brief description of drawings]

1 to 3 are sectional views showing the construction of an embodiment of the present invention. 1: Mass spectrometric section, 2: Ionization chamber 3: Filament, 4: Electron entrance port, 5: Electron exit port, 6: Slit electrode, 7: High performance liquid chromatograph, 8: Introduction tube, 9: Stainless tube, 10: Glass tube, 11 : Heater 12: Porous member, 13: Repeller power supply

Claims (4)

[Claims] 1. An ionization chamber, an introduction pipe whose tip is inserted into the ionization chamber to introduce the sample liquid into the ionization chamber from the outside, and an end pipe of the introduction pipe which is attached to the tip exit to vaporize the sample liquid while allowing the sample liquid to pass therethrough. An ion source for a mass spectrometer, comprising: a porous member for allowing the electron beam to be introduced into the ionization chamber toward the vicinity of the surface of the porous member. 2. An ion source for a mass spectrometer according to claim 1, wherein a repeller electrode is attached to a tip portion of said introduction tube, and further said porous member is attached to the tip thereof. . 3. An ion source for a mass spectrometer according to any one of claims 1 and 2, wherein a liquid chromatograph is connected to the introduction tube. 4. The ion source for a mass spectrometer according to any one of claims 1 to 3, wherein a reaction gas is introduced into the chamber to ionize the sample by chemical ionization.