JP2817625B2 - Plasma mass spectrometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma mass spectrometer for analyzing a sample by exciting the sample with plasma and guiding generated ions from a nozzle to a mass analyzer for detection.

[0002]

2. Description of the Related Art The structure and operation of a plasma mass spectrometer will be described with reference to FIG. First, the plasma 63 is generated by the plasma generation device 62, and the sample 61 is atomized and introduced into the plasma 63 to convert the sample into plasma. The ions 18 in the plasma are sent from the nozzle 64 to the second vacuum chamber 72.
After being deflected by a deflecting lens 65, which will be described later, the focusing lens 66 is used to deflect the quadrupole 6 in the third vacuum chamber 73.
8 In the quadrupole 68, the mass of the ion stream 18 containing a plurality of ion species is separated by scanning the applied voltage. The ions of the sample subjected to mass separation are detected by the ion detector 70, and the control unit 36 performs data analysis for sample analysis.

In the plasma mass spectrometer, ions are generated by the plasma 63, so that not only the ion stream 18 but also light 19 of the plasma 63 is introduced from the nozzle 64. Therefore, if the nozzle 64 and the quadrupole 68 are coaxially arranged, the strong plasma light 19 reaches the ion detector 70. Since the ion detector 70 generally employs a detection method of generating secondary electrons by ions and amplifying the secondary electrons, the secondary electrons are generated even by intense light and constitute noise. Of course, ions exiting the quadrupole 68 are guided to the ion inlet of the ion detector 70 by the ion deflection plate 69 so that the ion inlet of the ion detector 70 faces the outlet of the quadrupole 68 in front. Although it is arranged so as not to face, stray light irregularly reflected inside the device enters the ion detector 70, so that generation of some noise is inevitable.

Therefore, conventionally, as shown in FIG. 4, the axis of the ion stream 18 introduced from the nozzle 64 is shifted halfway by the ion deflection lens 65, and the quadrupole 68 is shifted as such. A configuration of being arranged on a shaft is used. According to this, the plasma light 19 travels straight from the nozzle 64 and is blocked by the electrode plate or the like, and stray light is greatly reduced.

The specific structure of the conventional ion deflection lens 65 will be described with reference to FIG. FIG. 5A shows an ion deflecting lens 80 that shifts ions using two pairs of electrode plates (83a and 83b) and (84a and 84b). Ions that have passed 18
Is deflected by the DC voltage applied between the first pair of electrode plates (83a and 83b), and is deflected by the second pair of electrode plates (84a and 84b).
The light is deflected again by the reverse voltage applied during b) so as to be in the same direction as the original, and passes through the ion passage hole 82a of the shielding plate 82 on the downstream side. On the other hand, the plasma light 19
After passing through the ion passage hole 81a of the upstream shielding plate 81, it goes straight and is shielded by the downstream shielding plate 82. Therefore, by disposing the quadrupole 68 at the position of the ion passage hole 82a of the downstream shield plate 82, the plasma light 19 is exhausted, and only the ion flow 18 is guided toward the quadrupole 68 and the detector 70. Can be. The ion deflection lens 8 of FIG.
Numeral 5 is for shifting ions by using a two-stage quadrupole of a first-stage quadrupole 88 and a second-stage quadrupole 89. FIG.
5C, the ion deflecting lens 90 has two pairs of upper and lower electrodes 93 like the ion deflecting lens 80 of FIG.
Although the electrode 94 is used, it is characterized in that the electrode pairs 93 and 94 are formed so as to surround the ion passage.

[0006]

The above-mentioned conventional ion deflecting lenses have a large number of electrodes, and have a problem that it is difficult to properly adjust the potential so that ions pass through both ion passing holes. The present invention has been made to solve such a problem, and an object of the present invention is to provide a plasma mass spectrometer having an ion deflection lens which has a simple structure and is easily adjusted. It is in.

[0007]

According to the present invention made to solve the above problems, a sample is excited by plasma,
In a plasma mass spectrometer that analyzes a sample by guiding generated ions from a nozzle to a mass analyzer and detecting the sample, a) between the nozzle and the mass analyzer, A first electrode plate that is provided substantially vertically and has a first ion passage hole in front of the nozzle; and b) is provided substantially parallel to the first electrode plate behind the first electrode plate with respect to the direction of ion movement. A second electrode plate having a second ion passage hole outside a solid angle range connecting the one ion passage hole; and c) both ends of the cylindrical member provided between the first electrode plate and the second electrode plate. And d) a DC voltage applying means for applying a DC voltage to the first electrode plate, the second electrode plate, and the intermediate electrode. And having an ion deflecting lens comprising: And

[0008]

The edges of both ends of the intermediate electrode are inclined with respect to the first electrode plate and the second electrode plate. Therefore, the DC voltage applying means applies a voltage between the first electrode plate and the intermediate electrode and a voltage between the intermediate electrode and the first electrode plate. When a different DC voltage is applied between the two electrode plates, the electric field between the electrodes is inclined with respect to the direction in which ions are emitted. For this reason, ions emitted from the nozzle and passing through the first ion passage hole of the first electrode plate are deflected between the first electrode plate and the intermediate electrode, and between the intermediate electrode and the second electrode plate. Is deflected by Therefore, by setting the edge shape and applied voltage of the intermediate electrode so that the electric field between the first electrode plate and the intermediate electrode and the electric field between the intermediate electrode and the second electrode plate are in exactly opposite directions, The ions passing through the second ion passage hole can be made to fly on an axis deviated from the axis of the ion flow emitted from the nozzle. On the other hand, the plasma light
After passing through the first ion passage hole, only the inside of each of the above three-dimensional regions is irradiated, so that the irradiation is not possible through the second ion passage hole and is blocked by the second electrode plate.

The flight direction of the ions is not necessarily parallel in front of the first electrode plate and after the second electrode plate.
Both ion flight directions may be angled. Therefore,
The angles of the edges of the two ends of the intermediate electrode and the voltage applied by the voltage applying means are set to any values as long as only ions pass through the first ion passage hole and the second ion passage hole and plasma light does not pass. No problem. In this case, it is conceivable to separate the voltage applying means for the second electrode and the first electrode and to set the second and first electrodes to different potentials.

[0010]

FIG. 2 shows the structure and operation of a high frequency inductively coupled plasma mass spectrometer 20 embodying the present invention. First, the plasma 23 is generated by the high-frequency inductively coupled plasma generator 22. Then, the sample 21 is atomized and introduced into the plasma 23, thereby turning the sample into plasma. The ions 18 in the plasma 23 are transmitted from a nozzle 24 provided at the tip of a double cone composed of a sampling cone and a skimmer cone to the extractor electrode 2.
5 introduces into the second vacuum chamber 32. Second vacuum chamber 3
2, the flight path of the ions 18 is shifted by the ion deflection lens 10 as shown in FIG.

The ion deflecting lens 10 of the present embodiment has a first electrode plate 11 provided on the upstream side in the ion flight direction and substantially perpendicular to the direction in which ions are emitted from the nozzle 24, and a first electrode plate on the downstream side. Second electrode plate 1 provided in parallel with plate 11
2 and an intermediate electrode 1 provided between both electrode plates 11 and 12
And 3. The first electrode plate 11 has a first ion passage hole 11a, and the second electrode plate 12 has a second ion passage hole 12a.
is provided so that the center axis of the first ion passage hole 11a coincides with the center axis of the nozzle 24, and the center of the second ion passage hole 12a coincides with the center of a quadrupole 28 described later. , Each is installed.

The intermediate electrode 13 is formed by connecting both ends of a metal cylinder to each other.
It has a shape cut on a plane inclined with respect to the first and second electrode plates 11 and 12. Therefore, as shown in FIG. 1A, for example, a DC voltage V1 is applied to the first electrode plate 11 and a different DC voltage V3 to the intermediate electrode 13 (V1> V3 when the ion charge is positive, as shown in FIG. (Preferably) is applied to form an inclined electric field between the two. With this tilted electric field,
The ions 18 that have passed through the first ion passage hole 11a are shown in FIG.
It is deflected upward in (a). In FIG. 1A, since the same potential is applied to the first electrode plate 11 and the second electrode plate 12, the electric field between the intermediate electrode 13 and the second electrode plate 12 is axially symmetric with respect to the electric field. Is formed. For this reason, the ions 18 are now shifted downward between the intermediate electrode 13 and the second electrode plate 12 and fly on a parallel path shifted from the original path, so that the second ion passage hole is formed. Pass through 12a. On the other hand, the light 19 of the plasma 23
The vacuum chamber enters the first ion passage hole 11 together with the ions 18.
a, but goes straight irrespective of these electric fields, and is blocked by the second electrode plate 12 to form the second ion passage holes 12a.
Never go through.

As described above, in the ion deflecting lens 10 of the present embodiment, since only two potentials need to be applied to the three components, the structure and control are very simple.

Returning to FIG. 2, the second part of the ion deflecting lens 10 will be described.
The ions 18 that have passed through the ion passage holes 12a enter the third vacuum chamber 33, are focused by the focusing lens 26, and
8 to the central axis. By applying a superimposed voltage of a predetermined DC voltage and an AC voltage to the quadrupole 28 by the driver 38, only ions having a predetermined mass can pass through the quadrupole 28. The target ions that have passed through the quadrupole 28 are deflected by the deflection plate 29, and
0 is detected. The detection signal of the detector 30 is
The sample is sent to the control unit 36 via the control unit 5, and the control unit 36 analyzes the sample by a predetermined method.

FIG. 3 shows another configuration example of the ion deflection lens. The ion deflection lens 40 shown in FIG.
Sleeves 41b and 42b extending toward the intermediate electrode 43 are provided around the first and the second electrodes 42, and the side surfaces of the entrance and the exit of the intermediate electrode 43 are covered with the sleeves 41b and 42b. The ion deflection lens 50 shown in FIG. 3B is obtained by dividing the intermediate electrode 53 into two front and rear parts 53a and 53b. In the configuration of FIG.
In comparison with the configuration of the above, the size (diameter and / or length) of each intermediate electrode can be set relatively freely, and the degree of freedom in designing the electric field shape including the setting of the applied voltage is improved. There is an advantage.

[0016]

The ion deflecting lens of the plasma mass spectrometer according to the present invention has a small number of electrodes to which a DC voltage is to be applied. The adjustment of the potential for passing through is facilitated. Also, since the number of components is small, assembly is easy.

[Brief description of the drawings]

FIG. 1 is a sectional view (a) and a front view (b) of an ion deflection lens used in a high-frequency inductively coupled plasma mass spectrometer according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a high-frequency inductively coupled plasma mass spectrometer of the embodiment.

FIG. 3 is a schematic configuration diagram of another two types of ion deflecting lenses according to the present invention.

FIG. 4 is a schematic configuration diagram of a conventional plasma mass spectrometer.

FIG. 5 is a schematic configuration diagram of three conventional ion deflection lenses.

[Explanation of symbols]

10, 40, 50, 80, 85, 90: ion deflecting lens 11, 41, 51, 81, 86, 91: first electrode plate 12, 42, 52, 82, 87, 92: second electrode plate 11a, 41a 81a: First ion passage holes 12a, 42a, 82a: Second ion passage holes 13, 43, 53a, 53b: Intermediate electrode 18: Ion flow 19: Plasma light 20: High-frequency inductively coupled plasma mass spectrometer 21: Sample 22 ... High frequency inductively coupled plasma generator 23 ... Plasma 24 ... Nozzle 25 ... Extractor electrode 26 ... Converging lens 28 ... Quadrupole 30 ... Ion detector 37 ... Ion deflection lens driver 38 ... Quadrupole driver

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-12448 (JP, A) JP-A-1-183051 (JP, A) JP-A-2-30050 (JP, A) JP-A-63-1988 91950 (JP, A) JP-A-60-211745 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01J 49/00-49/48 G01N 27/62 G21K 1/00- 1/16

Claims (1)

(57) [Claims] 1. A plasma mass spectrometer which excites a sample by plasma and guides generated ions from a nozzle to a mass analyzer to detect the sample, wherein a mass spectrometer is provided between the nozzle and the mass analyzer. a) a first electrode plate which is provided substantially perpendicular to the direction in which ions are emitted from the nozzle and has a first ion passage hole in front of the nozzle; and b) a first electrode plate behind the first electrode plate with respect to the direction of ion movement. A second electrode plate provided substantially parallel to the electrode plate and having a second ion passage hole outside a solid angle range connecting the nozzle and the first ion passage hole; c) a first electrode plate and a second electrode plate And an intermediate electrode having a shape obtained by cutting both ends of the cylindrical member at a plane inclined with respect to the first electrode plate and the second electrode plate; and d) the first electrode plate, the second electrode plate, DC voltage applying means for applying a DC voltage to the intermediate electrode, Plasma mass spectrometer, characterized in that it comprises an ion deflector lens having.