JP2021173553A - Analyzer - Google Patents

Abstract

To change the irradiation position of laser light when analyzing a liquid sample.SOLUTION: An analyzer (1) includes: a cell (11) having a housing section (11a) capable of housing a liquid sample (S); a laser light source (22) which outputs laser light (22a) for ablation of the surface of the liquid housed in the cell (11); mirrors (24, 25) which reflect the laser light (22a) output from the laser light source (22); a drive source (24b, 25b) which rotates the mirrors (24, 25); an optical system (23) which rotates the mirrors (24, 25) according to the irradiation position of the laser light (22a); and an analyzing instrument (2) which introduces an aerosol containing the sample (S) subjected to the laser ablation and delivered from the cell (11), and analyzes the introduced sample (S) by inductively-coupled plasma system.SELECTED DRAWING: Figure 1

Description

The present invention relates to an analyzer that irradiates a sample with a laser to emit (ablate) fine particles of the sample and analyzes the ablated fine particles, and particularly relates to an analyzer that is suitable when the sample is a liquid.

By applying a high voltage to an ionic or fine particle sample to make it plasma, and observing and analyzing the light from the excited atoms, qualitative and quantitative (mass spectrometry) of the element is performed. As a technique, an inductively coupled plasma (ICP) type analysis technique is known. In an ICP-type mass spectrometer (ICP-MS), a sample is made into an ion or fine particles and supplied to plasma. A liquid sample in which the measurement target is dissolved in a solvent is generally made into minute droplets with a nebulizer (sprayer) and sprayed for measurement. Further, a sample that is difficult to dissolve in a solvent or a solid sample that is desired to be measured in an insoluble state is irradiated with a laser to ablate and become an aerosol (LA-ICP-MS).
The technique described in Non-Patent Document 1 below is known as a technique for atomizing a sample with respect to ICP-MS.

In Non-Patent Document 1 (Gunther et al.), A solution in which trace elements and NaCl to be measured is dissolved is placed in a 150 μL beaker, the surface is covered with an anti-evaporation film, and a 20 μm through hole is formed in the film. A technique for irradiating a solution with a laser beam of an excima laser having a wavelength of 193 nm and a repetition frequency of 1 Hz to 20 Hz is described.

D. Gunther, 3 others, "Direct Liquid ablation: a new calibration strategy for laser ablation-ICP-MS microanalysis of solids and liquids", Fresenius J Anal. Chem. (1997) 359: 390-393

(Problems of conventional technology)
In the technique described in Non-Patent Document 1, when ablation of a liquid is performed, it is difficult to move the position where the laser beam is irradiated. If the laser beam is continuously irradiated to the same position, the temperature of the irradiation position rises too much, the characteristics change, and the ablation conditions fluctuate, which adversely affects the measurement. The position to irradiate the laser beam is generally performed by moving the stage that supports the cell, but if the cell containing the liquid is moved, the liquid may spill. If the liquid spills, the spilled liquid may evaporate and mix with the ablated material, adversely affecting the measurement results.
Further, if a wave is generated on the surface of the liquid when the cell is moving, the position of the surface of the liquid is not stable, and there is a possibility that a deviation from the irradiation position (focus position) of the laser beam may occur. Therefore, uneven ablation may occur, which may adversely affect the measurement result. Further, once a wave is generated, it takes time for the wave to subside, and the experiment cannot be performed until the wave subsides, which causes a problem that the experiment takes time.

An object of the present invention is to make it possible to change the irradiation position of a laser beam when analyzing a liquid sample.

In order to solve the technical problem, the analyzer of the invention according to claim 1 is used.
A cell having a storage unit that can store a liquid sample, and
A laser light source that outputs a laser beam that ablate the surface of the liquid contained in the cell,
An optical system that can move the irradiation position of the laser light output from the laser light source, and
An aerosol containing a sample that has been ablated and sent out from the cell is introduced, and an analyzer that analyzes the introduced sample by an inductively coupled plasma method.
It is characterized by being equipped with.

The invention according to claim 2 is the analyzer according to claim 1.
The optical system, which has a mirror that reflects laser light output from the laser light source and a drive source that rotates the mirror, and the mirror is rotated according to the irradiation position of the laser light.
It is characterized by being equipped with.

The invention according to claim 3 is the analyzer according to claim 2.
The mirror having a first mirror rotatable about a first axis and a second mirror rotatable about a second axis different from the first axis, and the first mirror. The drive source having a first drive source for rotating the first axis and a second drive source for rotating the second mirror around the second axis, said. The frequency at which the laser light from the laser light source is reflected by the first mirror, the laser light reflected by the first mirror is reflected by the second mirror toward the sample, and each mirror is rotated. The optical system having a repetition frequency of 10 kHz or more.
It is characterized by being equipped with.

The invention according to claim 4 is the analyzer according to any one of claims 1 to 3.
The laser light source that outputs a femtosecond pulsed laser beam having a pulse width on the order of femtoseconds.
It is characterized by being equipped with.

According to the first aspect of the present invention, when analyzing a liquid sample, the irradiation position of the laser beam can be changed.
According to the second aspect of the present invention, the irradiation position of the laser beam can be changed by controlling the mirror that reflects the laser beam.
According to the invention of claim 3, the range in which the laser beam can be irradiated can be widened as compared with the case of one mirror, and the analysis can be executed in a short time as compared with the case where the repetition frequency is low. can.
According to the invention of claim 4, ablation can be reliably performed as compared with the case of using nanosecond laser light.

FIG. 1 is an overall explanatory view of the analyzer according to the first embodiment of the present invention. FIG. 2 is an explanatory diagram of the cell of the first embodiment. FIG. 3 is an explanatory view of a main part of the laser ablation apparatus of the first embodiment.

Next, an embodiment which is a specific example of the embodiment of the present invention will be described with reference to the drawings, but the present invention is not limited to the following examples.
In addition, in the explanation using the following drawings, the illustrations other than the members necessary for the explanation are omitted as appropriate for the sake of easy understanding.

FIG. 1 is an overall explanatory view of the analyzer according to the first embodiment of the present invention.
In FIG. 1, the analyzer 1 of Example 1 has a mass spectrometer 2 as an example of an analyzer. The mass spectrometer 2 of Example 1 is composed of an inductively coupled plasma mass spectrometer (ICP-MS). The analyzer is not limited to ICP-MS, and for example, an inductively coupled plasma-optical Emission Spectroscopy (ICP-OES) can be used. As ICP-MS and ICP-OES, conventionally known ones can be used. For example, they are described in JP2013-130492A and the like, and since they are known, detailed description thereof will be omitted.

The downstream end of the connecting tube 3 as an example of the connecting portion is connected to the mass spectrometer 2. A merging joint 4 is connected to the upstream end of the connecting tube 3. The merging joint 4 is connected to the downstream end of the additional gas tube 6 as an example of the additional gas supply unit. In the first embodiment, the addition gas tube 6 is supplied with argon (Ar) gas as an example of the addition gas (makeup gas). In Example 1, the argon gas is supplied at a flow rate of about 0.5 to 1.2 L / min as an example.
The downstream end of the cell connection tube 7 is connected to the merging joint 4 as an example of the cell connection portion. A cell 11 is connected to the upstream end of the cell connection tube 7.

FIG. 2 is an explanatory diagram of the cell of the first embodiment.
In FIG. 2, the cell 11 is formed with a well 11a as an example of an accommodating portion capable of accommodating a liquid. The well 11a contains the liquid sample S. In the present specification and the scope of the patent claim, the "liquid sample" is not only when the sample itself is in a liquid state, but also when the sample is dissolved as ions in a solvent or when the sample is fine particles in the solvent. It is used in the sense that it includes the case where the sample is present in the liquid as in the case where the solvent is dispersed.
A transport gas tube 12 as an example of a transport gas supply unit is connected to the cell 11. In the first embodiment, the transport gas tube 12 is supplied with helium (He) gas as an example of the transport gas (carrier gas). In Example 1, the carrier gas is supplied at a flow rate of about 0.2 to 1 L / min as an example.

A laser ablation device 21 is arranged above the cell 11. The laser ablation device 21 irradiates the sample S in the cell 11 with a laser beam to ablate the sample S.
The analyzer 1 of the first embodiment has a computer device 31 as an example of the information processing device. The computer device 31 includes a computer main body 32, a display 33 as an example of a display unit, and a keyboard 34 and a mouse 35 as an example of an input unit. The computer main body 32 outputs a signal for controlling the drive of the laser ablation device 21, receives a detection result from the mass spectrometer 2, and can display it on the display 33.

(Explanation of laser ablation device)
FIG. 3 is an explanatory view of a main part of the laser ablation apparatus of the first embodiment.
In FIG. 3, the laser ablation apparatus 21 of Example 1 has a femtosecond laser 22 as an example of a laser light source. The femtosecond laser 22 outputs a femtosecond laser beam 22a having a pulse width on the order of femtoseconds as an example of the laser beam. The femtosecond laser 22 of the first embodiment outputs the femtosecond laser light 22a having a pulse width of 230 fs as an example, but the pulse width is not limited to the illustrated numerical value and can be changed.
The femtosecond laser 22 of the first embodiment has a shutter (not shown) arranged inside, and is configured to be able to control the frequency at which the femtosecond laser light 22a is output (the reciprocal of the interval at which the femtosecond laser light 22a is output). ing. In the first embodiment, as an example, the frequency can be controlled between 100 Hz and 60 kHz. That is, the femtosecond laser 22 outputs the femtosecond laser light 22a at 60 kHz, keeps the shutter always open at 60 kHz, and at 10 kHz, 5 out of 6 femtosecond laser lights 22a. It is possible to obtain an output of 10 kHz by blocking the output with a shutter. When other repetition frequencies are used, it can be dealt with by changing the number of shields blocked by the shutter according to the target frequency.

The femtosecond laser beam 22a is introduced into the galvano optical system 23 as an example of an optical system in which the irradiation position of the femtosecond laser beam 22a in the cell 11 can be moved. The galvano optical system 23 of the first embodiment has a first galvano mirror 24 as an example of a first mirror and a second galvano mirror 25 as an example of a second mirror. The first galvano mirror 24 reflects the femtosecond laser light 22a from the femtosecond laser 22 toward the second galvano mirror 25, and the second galvano mirror 25 samples the femtosecond laser light 22a from the first galvano mirror 24. It reflects toward S.
The first galvano mirror 24 is rotatably supported around the first mirror shaft 24a. Drive is transmitted to the first mirror shaft 24a from the first galvano motor 24b as an example of the first drive source. Therefore, in response to the drive from the first galvano motor 24b, the first galvano mirror 24 rotates and tilts around the first mirror shaft 24a to change the reflection direction of the femtosecond laser beam 22a.

Like the first galvano mirror 24, the second galvano mirror 25 also has a second mirror shaft 25a and a second galvano motor 25b as an example of the second drive source, and reflects a femtosecond laser beam 22a. Change. In Example 1, as an example, the first galvanometer mirror 24 controls the irradiation position in the X direction mainly along the gas flow direction on the surface of the sample S, and the second galvanometer mirror 25 mainly controls the irradiation position in the gas flow direction. The irradiation position in the Y direction intersecting with is controlled. Therefore, it is possible to scan the femtosecond laser beam 22a two-dimensionally under the control of the two galvanometer mirrors 24 and 25. In the first embodiment, as an example, the femtosecond laser beam 22a can be irradiated in a range of 20 cm × 20 cm.
A lens 26 as an example of an optical member is arranged between the second galvanometer mirror 25 and the cell 11. The lens 26 collects the passing femtosecond laser beam 22a so that the focal position of the femtosecond laser beam 22a is on the surface of the sample S.

(Explanation of Control Unit of Example 1)
The computer main body 32 as an example of the control unit has an input / output interface I / O for inputting / outputting signals to / from the outside. Further, the computer main body 32 has a ROM: read-only memory in which a program, information, and the like for performing necessary processing are stored. Further, the computer main body 32 has a RAM: random access memory for temporarily storing necessary data. Further, the computer main body 32 has a CPU: a central processing unit that performs processing according to a program stored in a ROM or the like. Therefore, the computer main body 32 can realize various functions by executing the program stored in the ROM or the like.

(Functions of computer body 32)
The computer main body 32 executes processing according to an input signal from a signal output element such as a keyboard 34, a mouse 35, a mass analyzer 2, and other sensors (not shown), and performs processing according to an input signal of the galvanomotors 24b and 25b and the femtosecond laser 22. It has a function to output a control signal to each control element such as a shutter.
That is, the computer main body 32 rotates the galvanometer mirrors 24 and 25, respectively, according to the target irradiation position in the liquid sample S of the cell 11, and irradiates the femtosecond laser beam 22a to the target irradiation position. It also has a function of controlling the shutter and displaying the analysis result on the display 33 according to the set repetition frequency.

(Action of Example 1)
In the analyzer 1 of the first embodiment having the above configuration, when the target analysis position is ablated in the liquid sample S, the position where the femtosecond laser beam 22a is irradiated by the galvano optical system 23 is controlled. Therefore, in the analyzer 1 of the first embodiment, it is not necessary to move the cell 11 side when moving the irradiation position of the femtosecond laser beam 22a. Therefore, the liquid sample S is prevented from spilling from the well 11a of the cell 11, and the liquid sample S is prevented from rippling. Therefore, when analyzing a liquid sample, it is possible to change the irradiation position of the laser beam and suppress the adverse effect on the measurement result.
In particular, in the conventional configuration for moving the stage, a commercially available one having a moving speed of about 100 μm / sec to 200 μm / sec is common, whereas in the galvano optical system 23, the laser is used even at 200 mm / sec or more. It is possible to scan the light. That is, it is possible to realize a moving speed of 1000 to 2000 times. Therefore, when the repetition frequency is the same, the moving distance (interval, pitch) between the irradiation of one pulsed laser beam and the irradiation of the next laser beam is 1000 to 2000 times. For example, when the repetition frequency is 1 kHz, the pitch is 100 nm to 200 nm in the case of stage movement, whereas in Example 1, it can be 200 μm. Therefore, in the case of stage movement, there is a concern that the irradiation position of the next laser light may overlap with the irradiation position of the previous laser light and the temperature may rise too much, but this is suppressed in the first embodiment.

Further, in the first embodiment, the galvano optical system 23 has two galvano mirrors 24 and 25. In the configuration where there is only one galvano mirror, the irradiation position of the femtosecond laser beam 22a can only be adjusted along the uniaxial direction (linear), but in the first embodiment having two galvano mirrors 24 and 25, 2 The irradiation position can be adjusted in the axial direction, that is, in the plane. Therefore, it is possible to greatly expand the irradiation range as compared with the case where there is only one galvanometer mirror.

Further, in the first embodiment, the galvanometer mirrors 24 and 25 are driven at a high repetition frequency of 10 kHz. Therefore, when the number of irradiation positions is the same, the time required to irradiate the femtosecond laser beam 22a is shortened as compared with the case where the repetition frequency is low. For example, when the repetition frequency is 10 Hz, it takes 600 seconds = 10 minutes to irradiate 6000 laser beams, but in Example 1 where the repetition frequency is 10 kHz, it is 0 to irradiate 6000 laser beams. It only takes 6 seconds. Therefore, in Example 1, the number of fine particles ablated in a short time can be increased and the amount of aerosol generated can be increased as compared with the case where the repetition frequency is low. Therefore, the amount of aerosol introduced into the mass spectrometer 2 can be increased, and the signal strength measured by the mass spectrometer 2 also becomes stronger.
Further, in Example 1, a femtosecond laser beam 22a is used as the laser beam. Therefore, the intensity of the laser beam is higher than that of the laser beam having a pulse width of nanoseconds, and ablation can be reliably performed.

(Change example)
Although the examples of the present invention have been described in detail above, the present invention is not limited to the above-mentioned examples, and various modifications are made within the scope of the gist of the present invention described in the claims. It is possible. Examples of modifications (H01) to (H05) of the present invention are illustrated below.
(H01) In the above-described embodiment, the galvano optical system 23 illustrates a configuration of 2-axis control, but a configuration of 3 or more axes is also possible. It is also possible to have a one-axis configuration.
(H02) In the above embodiment, it is desirable to use the femtosecond laser 22 as the laser light source, but the present invention is not limited to this. Depending on the object to be measured, a laser other than the femtosecond laser, for example, a nanosecond laser such as an excimer laser or a YAG laser can be used.

(H03) In the above embodiment, the specific numerical values and shapes can be arbitrarily changed according to the design, specifications, and the like.
(H04) In the above-mentioned embodiment, it is preferable to use He gas as the carrier gas, but the present invention is not limited to this. It can be changed to, for example, hydrogen gas, neon gas, argon gas, etc., depending on the type of the sample to be analyzed, the required accuracy, and the like.
(H05) In the above embodiment, the galvano optical system 23 is exemplified as an example of an optical system in which the irradiation position of the femtosecond laser beam 22a can be moved, but the present invention is not limited thereto. For example, as an example of the optical system, it is also possible to use a rotating multifaceted mirror (polygon mirror) in which a plurality of reflecting mirrors are provided on the outer surface of the rotating polygonal prism. In addition, for example, LCOS (Liquid Crystal On Silicon), which is a reflective liquid crystal element using a liquid crystal, can be used as an optical element.

1 ... Analyzer,
2 ... Analyzer,
11 ... cell,
11a ... Containment section,
22 ... Laser light source,
22a ... Laser light,
23 ... Optical system,
24 ... First mirror,
24, 25 ... Mirror,
24a ... 1st axis,
24b ... First drive source,
24b, 25b ... Drive source,
25 ... Second mirror,
25a ... Second axis,
25b ... Second drive source,
S ... Sample.

Claims (4)

A cell having a storage unit that can store a liquid sample, and
A laser light source that outputs a laser beam that ablate the surface of the liquid contained in the cell,
An optical system that can move the irradiation position of the laser light output from the laser light source, and
An aerosol containing a sample that has been ablated and sent out from the cell is introduced, and an analyzer that analyzes the introduced sample by an inductively coupled plasma method.
An analyzer characterized by being equipped with. The optical system, which has a mirror that reflects laser light output from the laser light source and a drive source that rotates the mirror, and the mirror is rotated according to the irradiation position of the laser light.
The analyzer according to claim 1, wherein the analyzer is provided with. The mirror having a first mirror rotatable about a first axis and a second mirror rotatable about a second axis different from the first axis, and the first mirror. The drive source having a first drive source for rotating the first axis and a second drive source for rotating the second mirror around the second axis, said. The frequency at which the laser light from the laser light source is reflected by the first mirror, the laser light reflected by the first mirror is reflected by the second mirror toward the sample, and each mirror is rotated. The optical system having a repetition frequency of 10 kHz or more.
The analyzer according to claim 2, wherein the analyzer is provided. The laser light source that outputs a femtosecond pulsed laser beam having a pulse width on the order of femtoseconds.
The analyzer according to any one of claims 1 to 3, wherein the analyzer is provided.

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