JPH10112280A - Ion source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the sensitivity of an analysis section by suppressing reduction in vacuum extent, when the diameters of orifices are increased. SOLUTION: A vacuum chamber provided with an ion guide 12 is divided into the second and third vacuum chambers 11, 19 by a partition plate 18 and an insulator 20. The diameters of the first and second orifices 7, 10 and set large. A large quantity of ions passing through the second orifice 10 are guided by the ion guide 12 and introduced into the third vacuum chamber 19, sent from its outlet, and guided into an accelerating region in the third vacuum chamber 19. Since the pressure in the outlet of the ion guide 12 and the accelerating region is low, ions rarely collide with gas molecules in the acceleration region, a large quantity of ions are introduced into a mass spectormeter(MS) analyzing section 17, and the sensitivity of the MS analysis section 17 is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion source for ionizing a sample for an analyzer for analyzing an ionized sample under a high vacuum, such as a mass spectrometer (MS). Belongs to the technical field of
In particular, the present invention belongs to the technical field of an ion source including an ion guide for guiding generated ions to an analysis unit.

[0002]

2. Description of the Related Art Conventionally, when analyzing a sample of a mixture using MS, first, the sample is introduced into a liquid chromatograph (hereinafter also referred to as LC) together with a mobile phase to separate it into single components. Then, the separated effluent is introduced into an ion source to be ionized. Then, the generated ions are guided to a mass spectrometer (MS analyzer) under a high vacuum for analysis.

[0003] As a method of ionizing a mobile phase from LC in this way, Atmospheric Pressure Ionization (hereinafter, also referred to as API), which is ionized under atmospheric pressure, is widely used. This API has the following three main methods.

[0004] One is an electrospray ionization (hereinafter, also referred to as ESI) method, which generates ions by electrostatic field spraying using a high voltage under atmospheric pressure. .

Another one is Atmospheric Pressure Chemical Ionization (hereinafter, referred to as Atmospheric Pressure Chemical Ionization).
APCI is a method of generating ions by spraying at atmospheric pressure and then chemically ionizing by corona discharge.

[0006] Still another is a sonic spray ionization (Sonic Spray Ionization; hereinafter, also referred to as SS), which is sprayed with a gas under atmospheric pressure,
This is a method of generating ions by ionizing by the effect of the ejected gas.

FIGS. 4A and 4B show a conventional ESI.
FIG. 2 is a diagram schematically illustrating an example of an ion source according to the present invention. In the figure,
1 is a LC, 2 is a capillary through which the effluent from LC1 flows, 3
Is an atomization probe, 4 is a block-shaped heater (vaporizer), 5 is a heater disposed in the heater 4, and 6 is a hole in the heater 4, and the atomized effluent flows. A bore, 7 is a first orifice, 8 is a first vacuum chamber held at a first pressure by a first vacuum pump (not shown),
9 is a ring lens disposed in the first vacuum chamber 8, 10 is a second orifice, 11 is a second vacuum chamber maintained at a second pressure higher than the first pressure by a second vacuum pump (not shown), 12 Is an ion guide for guiding the ions passing through the second orifice 10 so as not to be scattered; 13 is a support member for fixing the ion guide 12 to the apparatus body; 15 is an ion acceleration for accelerating ions guided by the ion guide 12 A lens, 16 is a main slit, and 17 is an MS analyzer.

The ion guide 12 is constituted by a Q-pole lens composed of four rod electrodes 12a, 12b, 12c, and 12d. Of these electrodes, the opposing electrodes 12a, 12c and the electrodes 12b, 12d are connected to each other. Are set to the same potential, and the electrodes 12a, 12
c and the electrode 12b, between the 12d, an AC voltage of 1～5MH _Z position is adapted to be applied. As a result, the ion guide 12 guides the ions such that they do not escape to the outside while resonating the ions.

A predetermined high voltage is applied between the thin tube 2 and the heater section 4, and the first and second
A predetermined high voltage is also applied to the orifices 7, 10 and the ring lens 9, respectively.

In the ion source based on the conventional ESI having the above-described structure, a high voltage is applied to the thin tube 2 to
The sample in the effluent containing the sample flowing from LC1 is ionized. That is, when nitrogen gas for atomization is ejected from the atomization probe 3 in a state where a high voltage is applied to the thin tube 2, the effluent from the LC 1 flows out into the atmospheric pressure through the thin tube 2 in the form of a mist and is atomized. To produce charged droplets. When the droplet flows through the pores 6 of the heater unit 4, the droplets are heated by the heater 5 via the heater unit 4, the remaining mobile phase is vaporized and removed, and exits the pores 6. At times, ions of the sample that can be analyzed by the MS analyzer 14 are generated. The generated ions are introduced into the first vacuum chamber 8 through the first orifice 7, and the ions are further transferred to the second vacuum chamber 8 by the ring lens 9 in the first vacuum chamber 8.
After passing through the orifice 10, it is introduced into the ion guide 12 in the second vacuum chamber 11. Finally, Ion Guide 1
The ions that have been guided by 2 and have moved with little loss of energy (acceleration potential) are further accelerated by the ion accelerating lens 15 and are focused on the MS analyzer 17 under high vacuum through the main slit 16. The mass analysis is performed by the MS analyzer 17.

[0011]

By the way, in order to analyze a sample in the MS analyzing section 17 with high sensitivity, the hole diameter of the first and second orifices 7, 10 is increased, and
What is necessary is just to increase the amount of ions to be introduced into the analysis unit 17.

However, in the above-mentioned conventional ion source, if the diameters of the first and second orifices 7 and 10 are simply increased, the pressure of the second vacuum chamber 11 conventionally maintained at about 4 × 10 ⁻⁵ Torr is obtained. Rises to about 4 × 10 ⁻⁴ Torr over the acceleration region of the ion acceleration lens 15. As described above, when the degree of vacuum is reduced over the acceleration region, the probability that ions will not be introduced into the MS analysis unit 17 in this acceleration region due to collision with gas molecules and loss of electric charge will be greatly increased. Therefore, the first
Simply increasing the pore diameter of the second orifices 7, 10 cannot increase the amount of ions introduced into the MS analyzer 17, and as a result, cannot increase the sensitivity of the MS analyzer 17.

The present invention has been made in view of such circumstances, and an object of the present invention is to increase the sensitivity of an analysis unit by suppressing an increase in pressure even when the diameter of an orifice is increased. It is to provide an ion source.

[0014]

In order to solve the above-mentioned problems, the invention of claim 1 generates ions of a sample in the atmosphere and introduces the generated ions into a vacuum region through an orifice. Further, the ions are guided to an acceleration region provided in the vacuum region by an ion guide provided in the vacuum region, and the ions are accelerated in the acceleration region and introduced into the analyzer. In the source, the vacuum region is divided into a plurality of regions where the pressure is gradually reduced from the orifice side to the acceleration region by one or more partition plates, and the ion guide is provided across the plurality of regions. It is characterized by being.

Further, the invention according to claim 2 is characterized in that the ion guide extends from the vacuum area on the orifice side to the vacuum area on the acceleration area through the plurality of partition plates.

Further, according to a third aspect of the present invention, the partition plate is provided with orifice holes for the partition plate, and the ion guides are independently provided for each of the plurality of divided vacuum regions. It is characterized by being.

[0017]

In the ion source according to the present invention having the above-described structure, the vacuum region is divided into a plurality of portions whose pressure gradually decreases from the orifice side to the acceleration region by one or more nets. Since the ion guide is provided over the plurality of regions, the pressure at the outlet of the ion guide and the acceleration region can be reduced. Therefore, a large amount of ions are introduced into the analysis unit, the sensitivity of the analysis unit is improved, and the analysis is performed more accurately.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a partial view partially showing an example in which an embodiment of an ion source according to the present invention is applied to ESI. The same components as those of the ion source shown in FIGS. 4A and 4B are denoted by the same reference numerals,
Detailed description is omitted.

As shown in FIG. 1, the ion source of the present embodiment has a structure shown in FIG.
In the ion source shown in (a), the second vacuum chamber 11 provided with the ion guide 12 is divided into two chambers by the partition plate 18, and a new second vacuum chamber 11 and a new third vacuum chamber 19 are formed. The ion guide 12 penetrates a hole formed in the partition plate 18 and is supported by an insulator 20 which is air-tightly held in the hole of the partition plate 18. The acceleration region of the ion acceleration lens 15 is the third region.
It is arranged in a vacuum chamber 19.

The first and second orifices 7, 10
Is set to be larger than before. And
Since the diameter of the orifice is set to be large, the pressure in the second vacuum chamber 11 is about 4 × 10 ⁻⁴ Torr, which is higher than in the past, but the pressure in the third vacuum chamber 19 is Approximately 7 × 10 ^-6 by plate 18 and insulator 20
It is kept at about Torr, which is much lower than before. As described above, the ion guide 12 is connected to the orifice 10.
The vacuum region is provided over two vacuum regions that are pressure-divided into two, a relatively high vacuum region at the second pressure side and a relatively low vacuum region at the third pressure region on the acceleration region side. Other configurations of the ion source of this example are the same as those of the ion source shown in FIGS. 4A and 4B.

In the thus configured ion source of the present embodiment, a larger amount of ions passing through the first and second orifices 7 and 10 having a large hole diameter as compared with the prior art are supplied to the second vacuum chamber 11. Guided by the ion guide 12 in the third vacuum chamber 19
And the ion guide 1 in the third vacuum chamber 19
By 2, it is led to the acceleration region in the third vacuum chamber 19.
In that case, ions are supplied to the ion guide 1 in the third vacuum chamber 19.
While proceeding through 2, the unnecessary molecules not guided by the ion guide 12 are diffused and removed, and are emitted from the exit of the ion guide 12.

Since the amount of gas molecules in the acceleration region is reduced due to the lower pressure at the outlet of the ion guide 12 and the acceleration region as described above, the ions emitted from the outlet of the ion guide 12 Collisions with surrounding gas molecules are less likely to occur.

As described above, according to the ion source of the present embodiment, the area where one ion guide 12 is extended is pressure-divided into a second pressure area and a third pressure area. The pressure at the exit of the guide 12 and at the acceleration region can be reduced. Therefore, a large amount of ions can be introduced into the MS analyzer 17. Thereby, the sensitivity of the MS analyzer 17 is improved, and the analysis can be performed more accurately.

Also, the first and second orifices 7, 10
Since the pressure at the outlet of the ion guide 12 and the acceleration region can be reduced even if the hole diameter of the orifice 7 is increased, the hole diameter of the orifices 7 and 10 is increased to some extent (for example, 1.5 times from the conventional hole diameter φ1 to φ1.5). Can be bigger. Since the sensitivity of the MS analyzer 17 is almost proportional to the hole area of the orifice, that is, the square of the hole diameter, the sensitivity can be further improved by increasing the hole diameter of the orifice. Other operations and effects of the ion source of this example are the same as those of the ion source shown in FIGS.

FIG. 2 is a partial view similar to FIG. 1, partially showing another example of the embodiment of the present invention. In the ion source of the example shown in FIG. 1 described above, one ion guide 12 penetrates the partition plate 18, is disposed in both the second vacuum chamber 11 and the third vacuum chamber 19, and passes through the insulator 20. Although supported by a partition plate 18, the ion source of the present embodiment is provided with a partition plate 18 that partitions the second vacuum chamber 11 and the third vacuum chamber 19 as shown in FIG. However, no insulator is provided. In this partition plate 18,
First and second orifices 7, 10 and main slit portion 16
A third orifice 21 is formed in the same straight line.

Further, a first ion guide 12a is provided in the second vacuum chamber 11, and a second ion guide 12b is provided in the third vacuum chamber 19. That is, in the ion source of the present example, the ion guide 12 is divided into two and provided independently for each of the second vacuum chamber 11 and the third vacuum chamber 19. Other configurations of the ion source of this example are the same as those of the ion source shown in FIG.

In the thus configured ion source of the present embodiment, a large amount of ions passing through the second orifice 10 are guided by the first ion guide 12 in the second vacuum chamber 11 and are separated by the partition plate 18. Is introduced into the third vacuum chamber 19 through the third orifice 21. Further, the ions introduced into the third vacuum chamber 19 through the third orifice 21 are guided by the second ion guides 12 b in the third vacuum chamber 19, and are introduced into the acceleration region in the third vacuum chamber 19. Be guided. In that case, ions are supplied to the second ion guide 12 in the third vacuum chamber 19.
While proceeding through b, unnecessary molecules are diffused and removed, and emerge from the outlet of the second ion guide 12b.

Since the pressure at the exit of the second ion guide 12b and the acceleration region is low, the ions emitted from the exit of the second ion guide 12b are less likely to collide with gas molecules in the acceleration region. Is further accelerated in the acceleration region and introduced into the MS analyzer 17. Other operations and effects of the ion source of this example are the same as those of the ion source shown in FIG.

In the example shown in FIGS. 1 and 2, one partition plate 18 is provided and the second vacuum chamber 11 is subdivided into two chambers. However, in the present invention, the second vacuum chamber 11 is provided with an ion guide. The two vacuum chambers 11 can be divided into three or more. In that case,
In the example shown in FIG. 2, the ion guide 12 is divided into two. However, the ion guide 12 is divided by the same number as the number of the vacuum chambers, and is provided independently for each vacuum chamber. You can also

The number of rods 12a to 12d constituting the ion guide 12 is not necessarily four, but is six.
A plurality of other rods, such as eight, twelve, and twelve rods, may be provided.

FIG. 3 is a diagram schematically showing still another example of the embodiment of the present invention. FIG. 3A shows an example in which the first and second ion guides 12a and 12b are provided so that the ion center orbits intersect. FIG. 3B shows an example in which the second ion guide 12b has an ion whose central orbit is curved in an arc shape. FIG. 3C shows the first case.
An example is shown in which the ion center trajectories of the second ion guides 12a and 12b are slightly shifted. Each of these examples has a structure in which neutral particles that travel straight from the second orifice are hardly introduced into the mass spectrometer 17.

Further, the ion source of the present invention is applicable not only to the APCI which is an atmospheric pressure ion source other than the ESI to which the above-mentioned respective examples are applied, but also to the ICP mass spectrometry. In that case, since the ion source of the present invention has an acceleration region, it is particularly effective for an apparatus using a magnetic field type mass spectrometer.

[0033]

As is apparent from the above description, according to the ion source of the present invention, since the ion guide is divided into a plurality of pieces under vacuum pressure, the pressure at the outlet of the ion guide and the acceleration region is reduced. be able to. Therefore,
Since a large amount of ions can be introduced into the analysis unit without loss, the sensitivity of the analysis unit can be improved, and the analysis can be performed more accurately.

Further, even if the hole diameter of the orifice is increased, the pressure at the outlet of the ion guide and the acceleration region can be reduced, so that the hole diameter of the orifice can be increased. Therefore, the sensitivity of the analyzer can be further improved.

[Brief description of the drawings]

FIG. 1 is a partial view partially showing an example of an embodiment of an ion source according to the present invention.

FIG. 2 is a diagram showing another example of the embodiment of the present invention.

FIGS. 3A to 3C are diagrams showing still another example of the embodiment of the present invention.

4A and 4B show an example of a conventional ion source, in which FIG. 4A schematically shows the entire configuration, and FIG.
It is sectional drawing which follows the IB-IIIB line.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Liquid chromatography (LC), 7 ... 1st orifice, 8 ... 1st vacuum chamber, 10 ... 2nd orifice, 11 ... 2nd vacuum chamber, 12 ... Ion guide, 12a ... 1st ion guide, 12b ... 2 ion guide, 15 ion accelerating lens, 17 mass analyzer (MS analyzer), 18 partition plate, 19 third vacuum chamber, 20 insulator, 21
Third orifice

Claims (3)

[Claims] 1. A method for generating ions of a sample in the atmosphere, introducing the generated ions into a vacuum region through an orifice, and further introducing the ions into the vacuum region by an ion guide provided in the vacuum region. In the ion source, the ions are accelerated in the acceleration region and introduced into the analysis section, and the vacuum region is accelerated from the orifice side by one or more partition plates. An ion source, wherein the ion guide is divided into a plurality of regions where the pressure gradually decreases to the region, and the ion guide is provided over the plurality of regions. 2. The ion source according to claim 1, wherein the ion guide extends from the vacuum region on the orifice side to the vacuum region on the acceleration region through the plurality of partition plates. . 3. An orifice hole for a partition plate is formed in each of the partition plates, and the ion guide is independently provided for each of the plurality of divided vacuum regions. The ion source according to claim 1, wherein