JP2000113852A - Atmospheric pressure ionization mass spectrograph - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an atmospheric pressure ionization mass spectrograph capable of guiding the ions generated by an atmospheric pressure ion source and introduced into an intermediate exhaust chamber via a guide port into a mass spectrometry section with high passing efficiency over a wide mass range. SOLUTION: This atmospheric pressure ionization mass spectrograph ionizes a sample in the atmospheric pressure or the pressure atmosphere near it and guides the ions to a mass spectrometry section arranged in vacuum via a guide port for mass spectrometry. The mass spectrograph is provided with ion guides 21 guiding the ions introduced via the guide port to the mass spectrometry section, arranged with plate-like electrodes having many ion passing ports in a line, and applied with voltages different in polarity in turn to the electrodes and barrier ribs 31 partitioning the chamber arranged with the mass spectrometry section and a chamber guided with ions via the guide port between the electrodes of the ion guides 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an atmospheric pressure ionization mass spectrometer which ionizes a sample in an atmosphere at or near atmospheric pressure and introduces the mass into a mass spectrometer arranged in a vacuum through an inlet. The present invention relates to an analyzer and, more particularly, to an ion guide for guiding ions introduced through an inlet to the mass spectrometer.

[0002]

2. Description of the Related Art Atmospheric pressure ionization has been widely used because of its easy handling and soft ionization. Representative examples of the atmospheric pressure ionization method include an APCI (atmospheric pressure chemical ionization) method and an ESI (electrospray ionization) method. A differential pumping system is used to introduce ions generated by these ionization methods into a mass spectrometer maintained in a high vacuum.

FIG. 1 is a diagram showing an ion introducing section of a mass spectrometer provided with such a differential pumping system. In FIG. 1, ions 2 generated by an atmospheric pressure ion source 1 are introduced into a first intermediate exhaust chamber 4 via a skimmer 3 and further introduced into a second intermediate exhaust chamber 6 via a skimmer 5. A multipole lens 7 and a converging lens 8 for improving the convergence of ions are arranged in the second intermediate exhaust chamber 6, and the ions having improved convergence by these lenses pass through the inlet 9. And introduced into the mass spectrometer 10 maintained in a high vacuum (a pressure of about 10 ⁻⁶ Torr) and subjected to mass analysis.

The first intermediate exhaust chamber 4 is evacuated to a pressure of about 1 to several Torr by a rotary pump RP, and the second intermediate exhaust chamber 6 is exhausted by a turbo molecular pump TMP to a pressure of 1 × 10 Torr.
A differential evacuation system is constructed such that the gas is exhausted to a pressure of about ^-3 Torr and the pressure difference between the ion source 1 at atmospheric pressure and the mass spectrometer 10 at high vacuum is maintained.

[0005]

The above-mentioned multipole lens 7 is provided to prevent the diffusion of ions in the second intermediate exhaust chamber 6, and for example, four rod-like electrodes are formed at 90 ° around the ion passage. Only the high frequency voltage is applied to the Q pole lenses arranged at intervals. In some cases, six or eight rod-shaped electrodes are used.

However, the multipole lens has a filter function, and cannot pass ions having different mass-to-charge ratios over a wide range at once. In order to cover a wide range, it is necessary to sweep the amplitude or frequency of a high-frequency voltage, which is disadvantageous due to its complicated structure and sensitivity.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned point, and has a high passing efficiency over a wide mass range over ions generated by an atmospheric pressure ion source and introduced into an intermediate exhaust chamber through an inlet. It is an object of the present invention to provide an atmospheric pressure ionization mass spectrometer that can be led to a mass spectrometer.

[0008]

In order to achieve this object, an atmospheric pressure ionization mass spectrometer according to the present invention ionizes a sample in an atmosphere at or near atmospheric pressure, and a mass spectrometer placed in a vacuum. Atmospheric pressure ionization mass spectrometer for mass spectrometry which is introduced through an inlet to a part, and which is an ion guide for guiding ions introduced via an inlet to the mass spectrometer, and a plate-like electrode having an ion passage port A large number of passage openings are aligned and arranged in a row, and an ion guide is provided in which voltages having different polarities are alternately applied to the respective electrodes. It is characterized in that a partition is provided for partitioning a room into which ions are introduced through a mouth.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 2 is a diagram showing the structure of one embodiment of the present invention. In FIG. 2, ions 2 generated by an atmospheric pressure ion source 1 are introduced into a first intermediate exhaust chamber 4 via a skimmer 3, further to a second intermediate exhaust chamber 6 via a skimmer 5, and further to a third intermediate exhaust chamber 6. It is introduced into the exhaust chamber 11. In the second intermediate exhaust chamber 6 and the third intermediate exhaust chamber 11, an ion guide composed of a ring lens 21 is disposed so as to extend over both of them. Thus, the light is converged toward the inlet 9, passes through the inlet 9, is introduced into the mass spectrometer 10 maintained in a high vacuum (pressure of about 10 ⁻⁶ Torr), and is subjected to mass analysis.

As shown in FIG. 3, the ring lens 21 has ring electrodes L1, L2,
Have a structure in which L3,... Positive voltage on every other electrode
(+ V) and the negative voltage (−V) are applied alternately. Partition plate 3 for partitioning the second intermediate exhaust chamber 6 and the third intermediate exhaust chamber 7
1 (earth potential) has an ion passage port concentric with the ring electrode, and is arranged along an equipotential surface of zero potential intermediate between adjacent ring electrodes.

FIG. 4 shows a potential distribution formed around the partition plate 31 and the ring electrode in the vicinity thereof.
It can be seen that 1 is arranged along the equipotential surface at zero potential intermediate between adjacent ring electrodes. The ions that have entered the ring lens 21 make a simple oscillation along the central trajectory by the electric field formed in the ring electrode, and pass through the ring lens in a form guided by the ring lens.

The diameter of the ion passage port provided in the partition plate 31 is selected to be a size necessary to maintain a pressure difference between the second intermediate exhaust chamber 6 and the third intermediate exhaust chamber 7. It is smaller than the ion passage of the ring electrode. Therefore, as shown in FIG. 2, the partition plate 31 is disposed at a position where the amplitude of the ion trajectory guided to the second intermediate exhaust chamber 6 via the skimmer 5 is at or near a minimum.

Therefore, even if the partition plate 31 for differential exhaust is provided, the ions can pass through the ion passage opening of the partition plate 31 with little loss.

The partition plate 31 is desirably set at an optimum position in consideration of the mean free path of the inflowing ions and the ion passage efficiency (the position where the amplitude of the ion orbit is minimum or close to it is high) in accordance with the result of the orbit calculation. As the converging lens 8, various electrostatic lenses including an Einzel lens can be used.

[0015]

As described above in detail, according to the present invention, a large number of plate-like electrodes having ion passage openings are arranged in a row with their passage openings aligned, and an ion guide to which voltages having different polarities are alternately applied to each electrode is provided. Since a partition is provided between the electrode in the middle of the ion guide and a room in which the mass spectrometric unit is arranged between the electrodes and a room into which ions are introduced via the inlet, the inlet generated by the atmospheric pressure ion source is used. An atmospheric pressure ionization mass spectrometer capable of guiding ions introduced into the intermediate exhaust chamber via the mass spectrometer with high passage efficiency over a wide mass range is provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing an ion introducing unit of a mass spectrometer provided with a differential pumping system.

FIG. 2 is a diagram showing the structure of one embodiment of the present invention.

FIG. 3 is a diagram showing a structure of a ring lens.

FIG. 4 is a diagram showing a potential distribution formed around a partition plate and a ring electrode in the vicinity thereof.

[Explanation of symbols]

 1: Atmospheric pressure ion source 2: Ions 3, 5: Skimmer 4: First intermediate exhaust chamber 6: Second intermediate exhaust chamber 11: Third intermediate exhaust chamber 21: Ring lens 21 31: Partition plate

Claims (2)

[Claims] 1. An atmospheric pressure ionization mass spectrometer for ionizing a sample in an atmosphere at or near atmospheric pressure, introducing the sample into a mass spectrometer arranged in a vacuum through an inlet, and performing mass analysis. An ion guide for introducing ions introduced through the mass spectrometer to the mass spectrometer, wherein a number of plate-like electrodes having ion passage openings are arranged in a row with their passage openings aligned, and a voltage having a different polarity is alternately applied to each electrode. And a partition that separates a room in which the mass spectrometric unit is arranged between the electrodes in the middle of the ion guide and a room into which ions are introduced via the inlet. Atmospheric pressure ionization mass spectrometer. 2. The atmospheric pressure ionization mass spectrometer according to claim 1, wherein the partition wall is arranged at a position where the amplitude of an ion trajectory in the ion guide is at or near a minimum.