JPH044354Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a mass spectrometer equipped with an atmospheric pressure ionization (API) ion source.

[Prior art] As a mass spectrometer device equipped with an API ion source,
Conventionally, for example, a structure as shown in FIG. 3 is known. In FIG. 3, the API ion source 1 consists of a glass cylinder 2, a corona discharge section 3, and a sample holding needle 4. In the corona discharge section 3, a carrier gas such as argon is introduced into the cylindrical electrode 5, and carrier gas atoms (excited species) are excited by the corona discharge generated between the needle electrode 6 and the cylindrical electrode 5. Or ions are created. The excited species or ions thus obtained flow out onto the flow of carrier gas toward the sample holding needle 4 to which an appropriate voltage is applied, and ionize the sample held at the tip of the needle 4. The sample ions generated at the tip of the needle 4 are transferred to the orifice plates 7 and 8.
is introduced into a quadrupole mass spectrometer consisting of a quadrupole electrode 9, a lens electrode 10, etc.

If such an API ion source is used, it is possible to directly ionize a liquid sample at atmospheric pressure and introduce it into a mass spectrometer for mass analysis, so future developments are expected.

[Problems to be solved by the invention] By the way, in order to efficiently introduce the sample ions generated in the API ion source into the mass spectrometer, the diameter of the orifice formed in the orifice plate 7 should be made as large as possible, and It is necessary to bring the orifice and the ion generating section, ie, the sample holding needle in the example of FIG. 3, close to each other. However, if the diameter of the orifice is increased, the pressure reduction area due to gas flowing into the mass spectrometer expands around the orifice, and reaches the tip of the sample holding needle 4 where ionization is performed, as shown in FIG. If the pressure at the tip decreases, ionization will not proceed normally and the amount of ions generated will decrease.
Currently, the orifice plate and the sample holding needle are kept sufficiently apart to prevent the tip from entering the pressure reduction area, resulting in the inability to obtain the full effect of increasing the diameter of the orifice.

The present invention was developed in view of this point,
API that allows the orifice and ion generation part to be close together even when the diameter of the orifice is increased
The purpose is to provide an ion source.

[Means for Solving the Problems] To achieve this objective, the present invention provides an atmospheric pressure ionization ion source and an electrode having an orifice for introducing sample ions generated by the ion source into the analysis section of a mass spectrometer. The mass spectrometer is characterized in that a buffer plate having an orifice with a larger diameter than the orifice is disposed between the orifice electrode and the ionization section of the ion source.

[Operation] Since the buffer plate is interposed between the orifice electrode and the tip of the needle electrode, most of the gas flowing into the mass spectrometer comes from between the orifice electrode and the buffer plate. Although the pressure at the bottom portion is reduced, the pressure reduction region does not expand much toward the tip of the needle-like electrode, and therefore it is possible to bring the needle-like electrode and the orifice closer together.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing an example of a mass spectrometer embodying the present invention. 1 differs from the configuration in FIG. 3 in that a buffer plate 12 with an orifice 11 through which sample ions pass is disposed between an orifice electrode 7 and the tip of a needle electrode 4. be. This buffer plate 12
Argon gas filling the cylindrical body 2 can flow into the region between the cylindrical body 2 and the orifice electrode 7 from the surrounding area as shown by arrow a in FIG.

FIG. 2 shows the distribution of the pressure reduction area in the orifice portion of the device having the above configuration. The argon gas in the cylinder 2 flows into the mass spectrometer through a path passing through the orifice 11 (arrow b in FIG. 1) and a path passing between the orifice electrode 7 and the buffer plate (also arrow a). , most of them follow the path of arrow a. Therefore, as can be seen from Figure 2, between the orifice electrode 7 and the buffer plate
Although the pressure decreases, the pressure reduction region does not extend much from the orifice 11 toward the needle electrode 4.

Therefore, as can be seen from a comparison with FIG. 4 for the conventional example, the needle electrode 4 can be brought closer to the orifice. Therefore, it is possible to efficiently introduce sample ions generated at the tip of the needle electrode 4 into the mass spectrometer.

In the above embodiment, the argon gas filling the cylinder 2 is caused to flow into the region between the buffer plate 12 and the orifice electrode 7.
For example, the buffer plate 12 and the orifice electrode 7
The region between the two may be isolated from the surroundings, and a gas such as argon gas may be supplied to the region from the outside.

The buffer plate is preferably made of metal, and in that case, it may be given the same potential as the orifice electrode 7, or it may be insulated from the surroundings and given a different potential from the orifice electrode.

The above example is a method of ionizing a sample held at the tip of a needle-like electrode by applying ions or excited species to it.
Although the present invention has been applied to an API ion source, ion sources based on various methods such as a glow discharge method, a corona discharge method, and an inductively coupled plasma method can be employed as the API ion source.

[Effects of the invention] As detailed above, according to the invention, since a buffer plate is provided between the orifice electrode and the ionization part of the API ion source, the ionization part can be brought closer to the orifice, and sample ions can be It becomes possible to efficiently introduce it into a mass spectrometer.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing an example of a mass spectrometer implementing the present invention, Fig. 2 is a view showing the distribution of the pressure reduction area of the orifice portion in the present invention, and Fig. 3 is a cross-sectional view showing a conventional example. FIG. 4 is a diagram showing the distribution of the pressure reduction area of the orifice portion in the conventional example. DESCRIPTION OF SYMBOLS 1... API ion source, 2... Cylindrical body, 3... Corona discharge part, 4... Sample holding needle, 7, 8... Orifice plate, 11... Ion passage port, 12... Buffer plate.

Claims (1)

[Scope of utility model registration request] An atmospheric pressure ion source that has a needle-shaped electrode that holds a sample at its tip and generates sample ions at the tip of the needle-shaped electrode, and sample ions that are generated at the tip of the needle-shaped electrode of the atmospheric pressure ion source. In a mass spectrometer in which an orifice electrode is provided opposite to the needle-like electrode for introducing the orifice into a high-vacuum mass spectrometer, there is a space between the orifice electrode and the tip of the needle-like electrode that is larger than the orifice of the orifice electrode. A mass spectrometer characterized in that buffer plates having orifices of the same diameter are arranged at intervals, and gas is supplied from the periphery to a region between the buffer plates and the orifice electrodes.