JPS6257068B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an atmospheric pressure ionization ion source used in a mass spectrometer, and more particularly to an atmospheric pressure ionization ion source suitable for an atmospheric pressure ionization mass spectrometer equipped with a liquid chromatograph.

Conventionally, an atmospheric pressure ionization ion source using, for example, a needle electrode has a structure as shown in FIG.

In the figure, a sample 1 is guided into a discharge chamber 11 by a carrier gas 2. In the discharge chamber 11, a corona discharge is generated between the needle electrode 4 and the counter electrode 5 by the high-voltage power supply 3, thereby generating primary ions of the carrier gas 2, and subsequently discharging the carrier gas, impurity substances, etc. reacts with ionic molecules to produce stable reactive ions. When a small amount of sample 1 having a low ionization potential or a large proton affinity is introduced into such reactive ions, the reactive ions ionize the sample.
The ions generated in this way pass through the holes in the counter electrode 5 to the accelerating electrode 6 connected to the power source V _a ;
It is emitted from the ground electrode 7.

In an ion source that operates in this way, especially when the sample 1 is a liquid, the volume of the discharge chamber 11 is large;
There was a problem that the resolution of the chromatogram decreased.

It is therefore an object of the present invention to eliminate the above-mentioned drawbacks and to provide a high-resolution atmospheric pressure ionization source.

In order to achieve the above object, in the ion source of the present invention, a sample is introduced from the center of the needle electrode to very close to the discharge section.

Hereinafter, the present invention will be explained based on examples.

FIG. 2 is a structural diagram of an ion source according to the present invention. In FIG. 2, the same reference numbers as in FIG. 1 refer to the same items. A liquid sample flowing out of the liquid chromatograph 9 passes through a through hole inside the hollow needle electrode 10 and is introduced into the discharge chamber 11 from the tip 0 of the hollow needle electrode 10 . On the other hand, the carrier gas 2 is provided outside the hollow needle electrode 10 and introduced between the guide tube 12 and the hollow needle electrode 10, which has a narrow tip and a small gap between the tip of the hollow needle electrode 10. is discharged into the discharge chamber 11 as a jet stream from the gap between the guide tube 12 and the hollow needle electrode 10. Further, a high voltage is applied between the hollow needle electrode 10 and the counter electrode 5 by the high voltage power supply 3, and corona discharge is generated by this high voltage. The liquid sample is vaporized by the heat of the corona discharge. The ionization method is as described in the prior art. In this type of ion source, liquid chromatograph 9
Since there is almost no dead volume between the outlet of the discharge chamber 11 and the discharge chamber 11, the resolution of the liquid sample will not be deteriorated. Furthermore, since the sample introduction section is concentrated in the ionization section, the sensitivity is very high and efficient ionization can be achieved. Additionally, the entire ion source is heated in advance to eliminate memory effects of the ion source. In addition, in order to efficiently vaporize the liquid sample, the needle electrode 10 may be heated; in this case, the discharge current may be controlled, that is, the resistance R shown in FIG. 2 may be changed, or a heater may be installed around the needle electrode 10. It's okay. Further, in order to efficiently vaporize the gas at the tip of the needle electrode 10, the flow rate of the carrier gas 2 may be increased and the gas may be exhausted from the gas outlet 8 using a pump or the like.

Note that in order to prevent the tip of the needle electrode 10 from clogging, a hole may be provided on the outer periphery of the needle electrode 10 at a portion slightly before the tip as a sample outlet. As explained above, according to the present invention, it has become possible to efficiently ionize a liquid sample flowing out of a liquid chromatograph without reducing the resolution of the liquid chromatograph. Therefore, it has become possible to use it as an ion source for a mass spectrometer directly connected to a liquid chromatograph.

[Brief explanation of the drawing]

FIG. 1 is a structural diagram of a conventional atmospheric pressure ionization ion source, and FIG. 2 is a structural diagram of an atmospheric pressure ionization ion source according to the present invention. 1... Sample, 2... Carrier gas, 3... High voltage source, 4... Needle electrode, 5... Counter electrode, 6...
Accelerating electrode, 7... Earth electrode, 8... Gas outlet,
9...Liquid chromatograph, 10...Hollow needle electrode.

Claims (1)

[Claims] 1. A corona discharge section having a needle electrode, a gas introduction section for introducing a carrier gas to the tip of the needle electrode, and a sample introduction section for supplying a sample to the tip of the needle electrode, In an atmospheric pressure ionization ion source that performs primary ionization of the carrier gas and reacts the generated ions with the sample to generate sample ions, the sample introduction part includes a through hole provided through the inside of the needle electrode. An atmospheric pressure ionization ion source characterized by comprising: